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Spirometry Don't Blow It!
Abstract
Spirometry is a useful test of pulmonary function and can be safely performed in a variety of clinical situations. Although the technique for performing the maneuver is straightforward, there are many sources of variability in results. Specific criteria must be met in order for the test to be considered valid. For the best results, proper instruction and coaching is essential, and patient understanding and effort must be maximized. Appropriate interpretation of spirometry requires several steps, including recognition and reporting of technically sound maneuvers, comparison to an appropriate reference population, and finally application of a well-developed interpretation scheme utilized in the context of patient symptoms and findings. Failure at any point along this path from performance to interpretation can yield misleading results that may ultimately poorly impact patient care. A clear understanding by the provider of proper coding and billing for spirometry is necessary to receive appropriate reimbursement from payers.
... [13] Personal information such as height, weight, age, gender and racial group should be recorded for each patient. [11,14] This information is necessary for the use of appropriate reference equations. The recently updated Global Lung Initiative (GLI) reference equations are the most comprehensive and should be used as they take into account the impact of racial differences in different population groups worldwide. ...
... [16] If standing height cannot be measured -e.g. in patients with severe spinal or thoracic cage abnormalities -the arm span may be used as an estimate of height. [10,11,17] A skilled and trained technician who is used to working with children and a comfortable and safe environment are important factors in achieving successful spirometry in children. [3] Children need adequate training and practise prior to being tested. ...
... The standing position should be avoided as this may lead to larger FVC values, especially in obese patients. [19] A nose clip should be worn, [2,11,20] but is not necessary if it does not fit properly or if it causes discomfort or anxiety; however, use, or lack thereof, should also be documented. A finger pinch of the nose is acceptable as long as this forms an adequate seal to the nose. ...
Spirometry forms an important component in the diagnosis and management of pulmonary diseases in children. In the paediatric setting, there are different challenges in terms of performance and interpretation of good quality and reliable tests. An awareness of the physiological and developmental aspects that exist in children is necessary to improve the quality and reliability of spirometry. We reviewed the recommendations on the technical aspects of performing spirometry in children, from the available guidelines and clinical trials. The focus was on the indications, methods and the interpretation of lung function tests in children <12 years of age. Reliable lung function testing can be performed in children, but an awareness of the limitations, the use of incentives and a dedicated lung function technologist are necessary.
... However, the process of PFT should be checked. For the precise evaluation of PFT, the patient's effort is essential (14). Therefore, although PFT is an objective means of evaluating pulmonary function, it has the possibility of misinterpretation. ...
Background:
This retrospective study was designed to evaluate preoperative pulmonary function test (PFT) results and skeletal muscle mass, represented by the erector spinae muscle (EM), as predictors of postoperative pulmonary complications (PPCs) in older patients undergoing lobectomy for lung cancer.
Methods:
The medical records, including preoperative PFT, chest computed tomography (CT) and PPCs, of patients older than 65 years undergoing lobectomy for lung cancer were retrospectively examined at Konkuk University Medical Center from January 2016 to December 2021. The sum of cross-sectional areas (CSAs) of the right and left EMs at the level of the spinous process with the 12th thoracic vertebra was used as the skeletal muscle mass (CSABoth).
Results:
Data from a total of 197 patients were included in the analyses. In total, 55 patients had PPCs. The preoperative functional vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) showed significantly poorer values and the CSABoth had significantly lower values in patients with than in those without PPCs. The preoperative FVC and FEV1 showed significant positive correlations with CSABoth. Multiple logistic regression analysis identified age, diabetes mellitus (DM), preoperative FVC and CSABoth as risk factors for PPCs. The areas under the curves for FVC and CSABoth were 0.727 (95% CI, 0.650-0.803; P<0.001) and 0.685 (95% CI, 0.608-0.762; P<0.001), respectively. The optimal threshold values of FVC and CSABoth to predict PPCs based on a receiver operating characteristic curve analysis were 2.685 L (sensitivity =64.1% and specificity =61.8%) and 28.47 mm2 (sensitivity =62.0% and specificity =61.5%), respectively.
Conclusions:
PPCs in older patients undergoing lobectomy for lung cancer were associated with lower preoperative FVC and FEV1 values and a lower skeletal muscle mass. Skeletal muscle mass, represented by the EM, was significantly correlated with the preoperative FVC and FEV1. Therefore, skeletal muscle mass may be useful for the prediction of PPCs in patients undergoing lobectomy for lung cancer.
... In the subsequent years that overlapped with the birth of the "evidence-based medicine" movement of the 1990s, the clinical utility of spirometry was increasingly studied. These efforts resulted in spirometry becoming the gold standard tool for respiratory disease diagnosis, monitoring disease status, assessing response to therapies, prognostication, pre-operative assessment, determining eligibility for specialized therapies and as an important outcome in pulmonary research [36]. However, some controversy still exists around the optimal role for spirometry in several important respiratory conditions [35,[37][38][39][40][41][42]. ...
175 years have elapsed since John Hutchinson introduced the world to his version of an apparatus that had been in development for nearly two centuries, the spirometer. Though he was not the first to build a device that sought to measure breathing and quantify the impact of disease and occupation on lung function, Hutchison coined the terms spirometer and vital capacity that are still in use today, securing his place in medical history. As Hutchinson envisioned, spirometry would become crucial to our growing knowledge of respiratory pathophysiology, from Tiffeneau and Pinelli's work on forced expiratory volumes, to Fry and Hyatt's description of the flow–volume curve. In the 20th century, standardization of spirometry further broadened its reach and prognostic potential. Today, spirometry is recognized as essential to respiratory disease diagnosis, management and research. However, controversy exists in some of its applications, uptake in primary care remains sub-optimal and there are concerns related to the way in which race is factored into interpretation. Moving forward, these failings must be addressed, and innovations like Internet-enabled portable spirometers may present novel opportunities. We must also consider the physiologic and practical limitations inherent to spirometry and further investigate complementary technologies such as respiratory oscillometry and other emerging technologies that assess lung function. Through an exploration of the storied history of spirometry, we can better contextualize its current landscape and appreciate the trends that have repeatedly arisen over time. This may help to improve our current use of spirometry and may allow us to anticipate the obstacles confronting emerging pulmonary function technologies.
... Demographic data mainly included the age, gender, body mass index and general information were collected. Clinical data included patient medical history, vital signs, laboratory test data, 6-minute walk distance (6MWD) [11,12], mMRC dyspnea score [13], spirometry [14], arterial blood gas, and diaphragm motions during quiet breathing and deep breathing [15]. These measurements were recorded before, after two-week and four-week periods of electrical stimulation. ...
Background: Chronic obstructive pulmonary disease (COPD) is a progressive lung disease, which might be improved by neuromuscular electrical stimulation. To date, no trials of intervention of inspiratory plus expiratory neuromuscular electrical stimulation have been conducted. This study aimed to evaluate the effect and safety of in patients with severe COPD.
Methods: In this prospective, multicenter controlled trial, 120 stable patients with severe COPD who received standard medical treatment were randomized assigned 1:1 to receive either inspiratory plus expiratory neuromuscular electrical stimulation (study intervention) or stimulation of the phrenic nerve, called diaphragm pacing (control intervention). Intention-to-treat analysis was carried out. The primary outcome was to analyze the changes in functional exercise capacity, estimated as six-minute walk distance (6MWD), following four weeks of electrical stimulation intervention.
Results: The change in 6MWD was greater in the study intervention (65.53 ± 39.45m) than in the control intervention (26.66 ± 32.65m). The mean between-group difference at four weeks was 29.07 m ([95% CI, 16.098 to 42.035]; P < 0.001). There was no significant between-group difference in secondary (modified Medical Research Council, forced expiratory volume in 1 second (FEV1), FEV1% predicted, and FEV1 ratio forced vital capacity (FEV1/FVC)) outcomes after four weeks of electrical stimulation. For GOLD 4 subjects, FEV1 and FEV1/FVC had improved in the study intervention (P < 0.05). No electrical stimulation-related serious adverse events were observed in either group.
Conclusion: Functional exercise capacity were significantly improved in the study intervention in stable patients with severe COPD after four weeks of treatment.
Trial registration: ChiCTR, ChiCTR2000032681. Registered 6 May 2020- Retrospectively registered,
http://www.chictr.org.cn/showproj.aspx?proj=53086.
... To evaluate the pulmonary problems that obesity may associated with; one may use the spirometer to assess the effect of obesity on lung functions and the type and extent of pulmonary impairment (7) . It is also pivotal in screening, diagnosing and monitoring respiratory diseases and distinguishing between the two basic impairment patterns of pulmonary impairments (obstructive and restrictive) (8) . ...
... Spirometry is an important tool to assist diagnosis, detect severity of lung disease, follow disease development, determine effects of and changes in treatment, and to assess preoperative risk [1]. Thus, accurate and reliable results from spirometry testing are necessary for optimal treatment of most patients with lung disease. ...
Objective
The aim of this pilot study was to compare spirometric values obtained with different types of spirometers, spirometers of same type, and repeated measurements with the same spirometer in a pulmonary function laboratory setting.
Results
12 healthy volunteers performed spirometry on four hot-wire (SensorMedics), two ultrasonic (Spirare) and one wedge-bellows (Vitalograph S) spirometers, according to ATS/ERS (American Thoracic Society/European Respiratory Society) guidelines. Spirometric values were compared using linear mixed models analysis with a random intercept for subjects and a fixed effect for type of spirometer used. Confidence intervals and p values were adjusted for multiple comparisons. Mean ± SD (L) values for hot-wire, ultrasonic and wedge-bellows spirometers for FVC (forced vital capacity) were 4.02 ± 0.66, 3.69 ± 0.61 and 3.93 ± 0.69, and for FEV1 (forced expiratory volume in one second) 3.06 ± 0.44, 2.95 ± 0.44 and 3.10 ± 0.49. Significant differences were found between hot-wire and ultrasonic and between wedge-bellows and ultrasonic spirometers for FVC and FEV1, and between hot-wire and wedge-bellows spirometers for FVC but not for FEV1. There were no significant differences between spirometers of same type, and low mean differences in repeated measurements for all spirometers included. In conclusion, the pilot study shows systematically higher values for FVC and FEV1 for hot-wire and wedge-bellows compared to ultrasonic spirometers.
... cia de valores de referência, a aplicação de espirometria em pré-escolares foi pouco estimulada. O uso de equações para crianças maiores (acima de 6 anos de idade) em pré-escolares é inadequado; as extrapolações introduzem grandes distorções no valor previsto (27)(28)(29). Idealmente, os valores de referência deveriam ser obtidos em populações sadias, oriundas do mesmo local onde se pretende usá-las. Além disso, os dados deveriam ser obtidos com tecnologia atualizada, isto é, com equipamentos semelhantes aos que serão usados na coleta da espirometria nos laboratórios e clínicas. ...
... Traditional pulmonary function testing includes a more comprehensive assessment of lung volumes and capacities; however, this information is beyond the scope of the current article. 6 In contrast to more comprehensive lung volumes and capacities, modern portable spirometry devices use a more simplified flow-volume loop display ( Figure 1). In addition, Table 1 provides the common pulmonary function parameters, definitions, and predicted normal values of a flow-volume loop. ...
Objectives:
To introduce pharmacy practitioners to spirometry testing and provide strategies for integrating this "value-added" tool with other direct patient care pharmacy services.
Data sources:
Spirometry literature and resources obtained through search strategies including Ovid, PubMed, and Google Scholar.
Summary:
Pharmacists are distinctive members of the multidisciplinary patient care team and can contribute by performing spirometry services for pulmonary patients. Pharmacists have been largely absent from performing this much needed service, perhaps as a result of lack of training or because this testing may be perceived as irrelevant to the pharmacist scope of practice. However, pharmacists are actively integrated with many aspects of pulmonary patient care, including recommending and adjusting inhaled pharmacological agents, monitoring for potential drug-drug and drug-disease interactions, recommending smoking cessation, assessing patient prescription insurance coverage, and educating patients, caregivers, and health care providers on use of prescribed respiratory delivery devices. Adding quality spirometry services, based on American Thoracic Society guidelines for accuracy, would increase the breadth and depth of services for pharmacy practitioners.
Conclusion:
Spirometry testing is an added tool for expanding direct patient care pharmacy services. Physician support, appropriate pharmacist training, and understanding of reimbursement of spirometry services are essential in providing quality spirometry testing. Future studies are needed to assess the role of pharmacists in performing spirometry and measuring the performance outcomes of pulmonary patients.
A BSTRACT
Background
Lung oscillometry is an alternative pulmonary function test in patients unable to perform spirometry due to cough or dyspnea.
Objective
The objective of the study was to study the characteristics of lung oscillometry parameters in patients with cough or dyspnea and who are unable to perform spirometry.
Methodology
A retrospective cross-sectional study Was conducted in a pulmonology outpatient clinic. Patients during the study period were selected for lung oscillometry after fulfilling the inclusion and exclusion criteria. The resistance and reactance parameters were measured along with the demographic variables. Statistical calculations were done.
Results
Forty-two percent patients were found to have airway obstruction if the recommended cutoff for resistance at 5 hertz (R5) was followed. However, reactance parameters were abnormal in most of the cases. The area of reactance (Ax) had a very good coefficient of correlation with R5 (0.867, P = 0.001).
Conclusions
Ax is a suitable lung oscillometric parameter for identifying airway obstruction in asthmatics.
Background:
Chronic obstructive pulmonary disease (COPD), a progressive lung disease, might improve with neuromuscular electrical stimulation. No trials on inspiratory plus expiratory neuromuscular electrical stimulation have been conducted yet.
Aim:
To evaluate the safety and effectiveness of inspiratory plus expiratory neuromuscular electrical stimulation in subjects with severe COPD.
Design:
This was a multicentre, prospective, randomised controlled trial.
Setting:
The subjects were outpatients enrolled from Beijing Chao-Yang Hospital affiliated with Capital Medical University, Tianjin Chest Hospital, and the First Hospital of Hebei Medical University.
Population:
Subjects had stable COPD with severe respiratory impairment.
Methods:
Using a computer statistical software, 120 stable subjects were randomly allocated (1:1) to receive inspiratory plus expiratory neuromuscular electrical stimulation (study group) and diaphragm pacing (control group). Demographic and clinical data were collected before, and after 2, and 4 weeks of the trial. The intention-to-treat analysis was conducted. The primary outcome was to analyse the changes in functional exercise capacity, estimated as six-minute walk distance (6-MWD), following electrical stimulation for 4 weeks. The secondary outcomes were changes in modified Medical Research Council score, forced expiratory volume in 1 second (FEV1), FEV1% predicted, and FEV1 ratio forced vital capacity (FEV1/FVC) following electrical stimulation for 4 weeks.
Results:
The change in 6-MWD was greater in the study group (65.53 ± 39.45 m) than in the control group (26.66 ± 32.65 m). The mean between-group difference at the fourth week was 29.07 m (95% confidence interval, 16.098-42.035; P <0.001). There were no significant between-group differences in the secondary outcomes after 4 weeks of electrical stimulation. For GOLD-4 COPD subjects, FEV1 and FEV1/FVC improved in the study group (P <0.05). No electrical stimulation-related serious adverse events were observed in either group.
Conclusions:
6-MWD were increased significantly, without adverse events, after four weeks of treatment of inspiratory plus expiratory neuromuscular electrical stimulation in stable patients with severe COPD, suggesting that this protocol benefits COPD rehabilitation.
Clinical rehabilitation impact:
The results of this study suggest that the simultaneous use of inspiratory plus expiratory neuromuscular electrical stimulation as an adjunct therapy may improve the functional exercise capacity of severe stable COPD subjects.
Objective:
To assess value-added service of a pharmacist-driven point-of-care spirometry clinic to quantify respiratory disease abnormalities within a primary care physicians office.
Methods:
This retrospective, cohort study was an analysis of physician referred patients who attended our spirometry clinic during 2008-2010 due to pulmonary symptoms or disease. After spirometry testing, data was collected retrospectively to include patient demographics, spirometry results, and pulmonary pharmaceutical interventions. Abnormal spirometry was identified as an obstructive and/or restrictive defect.
Results:
Sixty-five patients with a primary diagnosis of cough, shortness of breath, or diagnosis of asthma or chronic obstructive pulmonary disease were referred to the spirometry clinic for evaluation. A total of 51 (32 patients with normal spirometry, 19 abnormal spirometry) completed their scheduled appointment. Calculated lung age was lower in normal spirometry (58.1; SD=20 yrs) than abnormal spirometry (78.2; SD=7.5 yrs, p<0.001). Smoking pack years was also lower in normal spirometry (14.4; SD=10.7 yrs) than abnormal spirometry (32.7; SD=19.5 yrs, p=0.004). Resting oxygen saturation of the arterial blood (SaO2) was higher in normal spirometry than abnormal spirometry (98.1% vs 96.5%, p=0.016). Mean change in the forced expiratory volume in one second (FEV1) after administration of bronchodilator was greater in patients with abnormal spirometry compared with normal spirometry (10.9% vs 4.1%, p<0.001). Spirometry testing assisted in addition, discontinuation or altering pulmonary drug regimens in 41/51 patients (80%) and the need for further diagnostic testing or physician referral in 14/51 patients (27.4%).
Conclusions:
Implementation of a pharmacist-driven spirometry clinic is a value-added service that can be integrated with other clinical pharmacy services within the ambulatory care setting. Further studies are needed to determine the role of pharmacists in performing spirometry testing and measuring performance outcomes of the pulmonary patient.
Chronic lung diseases carry a significant amount of morbidity and mortality. Obstructive lung diseases in particular are the fourth leading cause of death in the United States. Easily implemented in the primary care office, spirometry is a portable and useful tool to diagnose and monitor patients with chronic lung disease. The main goals of office spirometry are to measure a patient's ability to exhale forcefully, and to distinguish obstructive from restrictive lung disease. Indications include to evaluate the signs or symptoms of possible lung disease, to assess effectiveness of treatment for lung disease, and to follow-up or monitor progression of lung disease in primary care or in occupational health patients. It may also be used to assess a patient's baseline lung function if needed for insurance purposes or by some employers as part of pre-employment screening. Basic requirements to perform office spirometry are a well-trained operator, a suitable patient, and spirometry equipment that meets or exceeds the American Thoracic Society's standards for office spirometers. Interpretation of spirometry results should always be done in the context of the patient's clinical picture and never as isolated values that may or may not fall within the range of normal. Results obtained in the office can be analyzed to determine if the patient has obstructive, restrictive, or mixed lung disease, or if any airway obstructions are present. The test can also be repeated after the administration of a bronchodilator to determine if significant bronchodilation is present. Spirometry data can be monitored over time to optimize therapy and assess progression of patients with chronic lung disease.
Spirometry plays an important role in occupational respiratory health surveillance programs. However, when not performed correctly, the values obtained can be misleading, resulting in misclassification of the workers' health status. Studies carried out in Italy have shown that spirometries recorded by occupational physicians often do not comply with quality criteria for recording FEV1 and FVC, according to joint statements on lung function testing for the American Thoracic Society and the European Respiratory Society, issued in 2005. For this reason, they are useless for the purposes of their execution. Compliance with ATS/ERS statements is essential to assure that spirometry results are beneficial for the monitoring of workers' health.
Measurement of lung volumes is an integral part of complete pulmonary function testing. Some lung volumes can be measured during spirometry; however, measurement of the residual volume (RV), functional residual capacity (FRC), and total lung capacity (TLC) requires special techniques. FRC is typically measured by one of three methods. Body plethysmography uses Boyle's Law to determine lung volumes, whereas inert gas dilution and nitrogen washout use dilution properties of gases. After determination of FRC, expiratory reserve volume and inspiratory vital capacity are measured, which allows the calculation of the RV and TLC. Lung volumes are commonly used for the diagnosis of restriction. In obstructive lung disease, they are used to assess for hyperinflation. Changes in lung volumes can also be seen in a number of other clinical conditions. Reimbursement for measurement of lung volumes requires knowledge of current procedural terminology (CPT) codes, relevant indications, and an appropriate level of physician supervision. Because of recent efforts to eliminate payment inefficiencies, the 10 previous CPT codes for lung volumes, airway resistance, and diffusing capacity have been bundled into four new CPT codes.
Bimaxillary orthognathic surgery (BOS) is commonly used in the correction of severe Class III deformities (mandibular prognathism with maxillary retrognathism). The postural response of the pharyngeal airway after mandibular setback and maxillary advancement procedures is clinically crucial for maintaining optimum respiration. Patients might suffer from obstructive sleep apnoea, postoperatively. The aim of this study was to determine the effects of BOS on pharyngeal airway space, respiratory function during sleep and pulmonary functions. 21 male patients were analysed using cephalometry, spirometry for pulmonary function tests, and a 1 night sleep study for full polysomnography before and 17±5 months after BOS. The data show that the hyoid bone repositioned to the inferior, the tongue and soft palate displaced to the posterior, narrowed at the oropharynx and hypopharynx and widened at the nasopharynx and velopharynx levels significantly (p<0.05). The alterations indicated decreased airway resistance and better airflow. As a consequence of polysomnography evaluation, the sleep quality and efficiency of the patients improved significantly after BOS. Patients who undergo BOS should be monitored with pulmonary function tests and polysomnography pre- and postoperatively to detect any airway obstruction.
Spirometry before and after bronchodilator is performed to assess air flow-limitation reversibility. In patients with normal baseline spirometry the frequency of a positive bronchodilator response, as defined by American Thoracic Society/European Respiratory Society criteria, has not been described.
We retrospectively analyzed adult patients tested in 2 academic pulmonary function testing laboratories over a 7-year period, with specific attention to patients who underwent bronchodilator testing after a normal baseline spirometry (FEV(1), FVC, and FEV(1)/FVC within normal limits). The frequency of a positive response to bronchodilator, defined as a 12% and 200 mL increase in either FEV(1) or FVC, was calculated and associated with demographic factors.
Of the 1,394 patients with normal spirometry who were administered bronchodilator, 43 (3.1%) had a positive response. The percent of patients responding to bronchodilator were grouped according to pre-bronchodilator FEV(1): > lower limit of normal to 90% of predicted = 6.9%, 90-100% of predicted = 1.9%, and > 100% of predicted = 0%. An FEV(1)/FVC in the lowest 2 quartiles was associated with a higher frequency of bronchodilator response. Older patients were more likely to respond to bronchodilator, but no other demographic factors were associated with a positive bronchodilator response.
In our study population the frequency of a positive bronchodilator response in patients with normal baseline spirometry is 3.1%. None of the patients with a pre-bronchodilator FEV(1) > 100% of predicted and only 1.9% of patients with an FEV(1) between 90% and 100% of predicted responded. Bronchodilator testing can be omitted in patients with normal spirometry and an FEV(1) above 90% of predicted, as they have a low probability of a positive response.
This study explores the use of spirometry in primary care settings.
A 4-page survey was mailed to a national, random sample of office-based family physicians and pediatricians. Survey items addressed knowledge, attitudes, and practices regarding spirometry and standardized clinical vignettes. Data were analyzed by using χ2 tests and multivariate logistic regression.
Among the 360 respondents who provided care to children with asthma, 52% used spirometry in clinical practice, whereas 80% used peak flow meters and 10% used no lung function tests. Only 21% routinely used spirometry for all guideline-recommended clinical situations. More family physicians than pediatricians reported using spirometry (75% vs 35%; P<.0001), and family physicians were more comfortable in interpreting spirometric results (50% vs 25%; P<.0001). Only one-half of respondents interpreted correctly the spirometric results in a standardized clinical vignette, and the frequency of underrating asthma severity increased with the inclusion of spirometric results. The most common barriers to the use of spirometry, that is, time and training, were cited more often by physicians who did not use spirometry. Two-thirds of respondents agreed that they would want additional training regarding implementing spirometry in their clinical practices.
The use of spirometry in primary care settings for children with asthma does not conform to national guidelines. Widespread implementation of national asthma guidelines likely would require a major educational initiative to address deficiencies in spirometry interpretation and other barriers.
Three recent advances in assessment of routine lung function are reviewed. In both normal subjects and patients with obstructive lung disease, the flows during the forced vital capacity (FVC) manoeuvre depend significantly on the pattern of the preceding inspiratory manoeuvre. Accordingly, the latter should be standardized in clinical and epidemiological studies. Although the nature of this phenomenon is not fully understood, stress relaxation of lung tissues probably plays the primary role. The negative expiratory pressure technique provides a simple and reliable tool for detecting expiratory flow limitation both at rest and during exercise. The method does not require body plethysmography or the patient’s cooperation and coordination, and can be applied in any desired body posture. A simple method for monitoring FVC performance has been developed. It allows detection of flow limitation during the FVC manoeuvre.
Obesity is increasingly prevalent. Earlier studies indicated that there was a significant but small difference in spirometric values between sitting and standing position in the normal population. It is not known if this is true for obese individuals. The recommendations of the American Thoracic Society (ATS) are to document if a spirometry is done in a sitting or standing position. We performed a study in which we compared sitting and standing spirometric values in obese individuals. Patients with a body mass index (BMI) > or = 30 kg/m2 who were referred for spirometry were invited to participate. All tests were done according to American Thoracic Society recommendations. We studied 50 subjects (32 females and 18 males; mean age 45 yr [SD +/- 14.4]). Age range was 20-71 years. Average BMI was 39 (SD +/- 7, range 30 to 65). Twenty-two did the first testing in the sitting position and 28 standing. There was a small but statistically significant difference between forced vital capacity (FVC) in the standing versus sitting position (Wilcoxen test, p < or = 0.05). There was no significant difference in FEV1 between sitting and standing. Our conclusion is that body position is not important when performing spirometry in persons with BMI > or = 30 kg/m2.
Spirometric reference values for Caucasians, African-Americans, and Mexican-Americans 8 to 80 yr of age were developed from 7,429 asymptomatic, lifelong nonsmoking participants in the third National Health and Nutrition Examination Survey (NHANES III). Spirometry examinations followed the 1987 American Thoracic Society recommendations, and the quality of the data was continuously monitored and maintained. Caucasian subjects had higher mean FVC and FEV1 values than did Mexican-American and African-American subjects across the entire age range. However, Caucasian and Mexican-American subjects had similar FVC and FEV1 values with respect to height, and African-American subjects had lower values. These differences may be partially due to differences in body build: observed Mexican-Americans were shorter than Caucasian subjects of the same age, and African-Americans on average have a smaller trunk:leg ratio than do Caucasians. Reference values and lower limits of normal were derived using a piecewise polynomial model with age and height as predictors. These reference values encompass a wide age range for three race/ethnic groups and should prove useful for diagnostic and research purposes.
The impact of denture wear in edentulous subjects while performing routine spirometric measurements has never been systematically investigated. We compared the values of FVC, FEV(1), PEFR, FEF(50%), FIV(1), and FIF(50%) recorded with and without dentures in three groups of edentulous subjects: 36 asymptomatic subjects with normal spirometry (N), 22 patients with chronic obstructive pulmonary disease (COPD), and 18 with interstitial lung disease (ILD). In 14 subjects retropharyngeal space with and without dentures was assessed by cephalometry. Subjects with N and ILD had significantly lower airflow rates without dentures, whereas subjects with COPD had no significant difference in spirometric values recorded with or without dentures. The retropharyngeal space was significantly decreased by removing dentures (from 1.52 +/- 0.07 to 1.16 +/- 0.09 cm, SEM, p < 0.0001). These findings indicate that in edentulous subjects with a normal or restrictive pattern, the recording of flow-volume curves with or without dentures produces small but significant differences. Although such differences do not appear to have clinical significance, the fact that when dentures are used some respiratory flows are higher would favor the use of dentures in edentulous subjects during spirometric evaluation.
Pulmonary function tests are most useful when performed with good technique and with an accurate system. Using standard techniques in performing the tests minimizes diagnostic and therapeutic errors. This report discusses the rationale and limits of standardization and offers practical suggestions for using available standards to increase confidence in test results.
SERIES “ATS/ERS TASK FORCE: STANDARDISATION OF LUNG FUNCTION TESTING”
Edited by V. Brusasco, R. Crapo and G. Viegi
Number 1 in this Series
⇓In preparing the joint statements on lung function testing for the American Thoracic Society (ATS) and the European Respiratory Society (ERS), it was agreed by the working party that the format of the statements should be modified so that they were easier to use by both technical and clinical staff. This statement contains details about procedures that are common for many methods of lung function testing and, hence, are presented on their own. A list of abbreviations used in all the documents is also included as part of this statement.
All terms and abbreviations used here are based on a report of the American College of Chest Physicians/ATS Joint Committee on Pulmonary Nomenclature 1. The metrology definitions agreed by the International Standards Organization (ISO) are recommended 2 and some important terms are defined as follows.
Accuracy is the closeness of agreement between the result of a measurement and the conventional true value.
Repeatability is the closeness of agreement between the results of successive measurements of the same item carried out, subject to all of the following conditions: same method, same observer, same instrument, same location, same condition of use, and repeated over a short space of time. In previous documents, the term reproducibility was used in this context, and this represents a change towards bringing this document in line with the ISO.
Reproducibility is the closeness of agreement of the results of successive measurements of the same item where the individual measurements are carried out with changed conditions, such as: method of measurement, observer, instrument, location, conditions of use, and time. Thus, if a technician tests a subject several times, this is looking at the …
The clinical utility of spirometric screening of asymptomatic smokers for early signs of air flow limitation has recently come under review. The current authors propose that reduced forced expiratory volume in one second (FEV 1 ) is more than a measure of airflow limitation, but a marker of premature death with broad utility in assessing baseline risk of chronic obstructive pulmonary disease (COPD), lung cancer, coronary artery disease and stroke, collectively accounting for 70–80% of premature death in smokers.
Reduced FEV 1 identifies undiagnosed COPD, has comparable utility to that of serum cholesterol in assessing cardiovascular risk and defines those smokers at greatest risk of lung cancer. As such, reduced FEV 1 should be considered a marker that identifies smokers at greatest need of medical intervention.
Smoking cessation has been shown to attenuate FEV 1 decline and, if achieved before the age of 45–50 yrs, may not only preserve FEV 1 within normal values but substantially reduce cardiorespiratory complications of smoking.
Recent findings suggest inhaled drugs (bronchodilators and corticosteroids), and possibly statins, may be effective in reducing morbidity and mortality in patients with chronic obstructive pulmonary disease. The current authors propose that spirometry has broad utility in identifying smokers who are at greatest risk of cardiorespiratory complications and greatest benefit from targeted preventive strategies, such as smoking cessation, prioritised screening and effective pharmacotherapy.
Description:
New U.S. Preventive Services Task Force (USPSTF) recommendation about screening for chronic obstructive pulmonary disease (COPD) using spirometry.
Methods:
The USPSTF weighed the benefits (prevention of > or =1 exacerbation and improvement in respiratory-related health status measures) and harms (time and effort required by both patients and the health care system, false-positive screening tests, and adverse effects of subsequent unnecessary therapy) of COPD screening identified in the accompanying review of the evidence. The USPSTF did not consider the financial costs of spirometry testing or COPD therapies.
Recommendation:
Do not screen adults for COPD using spirometry. (Grade D recommendation).
The forced expiratory manoeuvre was first described by Tiffeneau and Pinelli working in Paris (France), in December 1947, who proposed measurement of the "pulmonary capacity usable on exercise" (capacite pulmonaire utilisable a l'effort) (CPUE), the maximal volume expelled in one second after a deep inspiration, It was intended to replace the measurement of the maximum breathing capacity, a difficult and tiring manoeuvre, A similar approach was later followed in the USA by Gaensler, who proposed the "timed vital capacity" in 1951. The name CPUE was changed to "volume expiratoire maximum seconde" (VEMS) by a group of European experts, who met in Paris on February 13, 1954, whereas the expression "forced expiratory volume" was adopted by the British Thoracic Society in 1957, Despite numerous attempts to examine the forced expiration in a different manner, the VEMS and/or forced expiratory volume in one second (FEV1) remain, after 50 yrs the main variables used daily by the respiratory physician. Although primarily a pharmacologist, Robert Tiffeneau (1910-1961) undoubtedly deserves to figure among the pioneers of respiratory medicine.
In a serach for risk factors for myocardial infarction and sudden cardiac death, the mean total vital capacity as measured at multiphasic health checkups was lower in persons who later had a first myocardial infarction than in risk-factor-matched controls (3.17 vs. 3.29 liters, 395 pairs, P less than 0.05) and non-risk-factor-matched controls (3.16 vs. 3.41 liters, 401 pairs, P less than 0.001). Findings were little affected by age and height adjustment and were similar for sudden cardiac death. The first-second vital capacity was also inversely related to later development of these conditions, but the ratio of that measurement to total vital capacity was not. Heavy smoking, productive cough, exertional dyspnea and cardiac enlargement were associated with diminished total capacity. However, exclusion of subjects with these findings did not reduce the predictive value of total vital capacity. Diminished vital capacity deserves continued attention as a possible coronary risk factor. Its relation to subsequent coronary events is not well explained.
Guberan, E., Williams, M. K., Walford, Joan, and Smith, Margaret M. (1969).Brit. J. industr. Med.,26, 121-125. Circadian variation of F.E.V. in shift workers. The one-second forced expiratory volume (F.E.V.1·0), the forced vital capacity, and the oral temperature were measured in a group of men working a rotating three-shift system—2 to 10 p.m. one week, 10 p.m. to 6 a.m. the next week, and 6 a.m. to 2 p.m. the third week. The outside air temperature at the London Weather Centre was also obtained. Measurements were made on Mondays and Fridays at the beginning, middle, and end of the shift.The mean F.E.V.1·0 of 19 normal men showed an increase of 0·15 litre (4·1%) between the beginning and end of both the morning shifts, a mean decrease of some 0·05 litre (1·5%) between the beginning and end of the afternoon shifts, and little change during the night shifts. This circadian variation could not be attributed to industrial fume, smoking or a learning effect.The findings will be of practical importance when F.E.V. is measured in shift workers to determine the effects of toxic substances on ventilatory capacity.
From 1954 to 1961, pulmonary function was assessed in 2,718 British men by forced expiratory maneuvers, and mucus hypersecretion and smoking habits were assessed by questionnaires. In 20 to 25 yr of follow-up, 104 men (all of whom had smoked) died of chronic obstructive pulmonary disease (COPD). The risk of death from COPD was strongly correlated with the initial degree of air-flow obstruction. Among men with similar initial air-flow obstruction, however, age-specific COPD death rates were not significantly related to initial mucus hypersecretion, supporting the concept that air-flow obstruction and mucus hypersecretion are largely independent disease processes. A moderate relationship existed between initial mucus hypersecretion and subsequent lung cancer mortality, but it is not known whether this was due solely to a common correlation of both conditions with the effective degree of exposure of the large bronchi to causative factors such as tobacco smoke.
Thirteen patients with chronic obstructive pulmonary disease (COPD) performed forced vital capacity (FVC) maneuvers either immediately after a rapid inspiration (maneuver 1) or after a slow inspiration with a 4- to 6-s end-inspiratory pause (maneuver 2). Seated in a body plethysmograph, they breathed through a pneumotachograph. Inspirations were initiated from resting end-expiratory lung volume. Abdominal muscle activity was recorded by means of surface electrodes. With maneuver 1: (1) expiratory flows were 20 to 40% larger in the volume range 10 to 95% FVC; (2) peak expiratory flow was on average 30% higher; and (3) FEV1, expressed as percent of FVC, increased by about 8%. No substantial differences in the pattern of abdominal muscle activity occurred between maneuvers. The dependence of maximal flow-volume curves on the time course of the preceding inspiration is probably related in part to the viscoelastic elements present within the respiratory system, which, stretched during rapid inspirations, increase the effective elastic recoil during the FVC maneuver 1. This cannot occur with maneuver 2, because of stress relaxation of the viscoelastic elements during the 4- to 6-s breathhold preceding the FVC maneuver. Other factors (e.g., time constant inequality) might also be involved. In any case, the results imply that the inspiratory maneuver prior to FVC must be standardized.
The American Thoracic Society (ATS) recommendations to establish reproducibility of the forced expiratory volume in one second (FEV1) are that the value come from "at least 3 acceptable forced expiratory curves" where "the largest forced vital capacity maneuver (FVC) and the second largest FVC should not vary by more than 5%." It has been suggested that there is a "negative effort dependence" of the FEV1 and, alternatively, that the magnitude of the FVC influences the FEV1. We examined the relationship between FEV1 and a direct measurement of effort, or work, defined as the area under the alveolar pressure-volume curve in 1 s. Thirteen normal individuals and 17 patients with cystic fibrosis or asthma were instructed to make a series of maximal efforts, as in routine testing. Comparing the maneuver that resulted in the greatest work to that with the lowest work, all with FVCs within 5% of one another, there was no correlation between change in work and change in FEV1 (delta FEV1). There was a significant relationship between delta FEV1 and changes in FVC (r = 0.49, p < 0.01). The delta FEV1 did not correlate with the degree of hyperinflation (the FRC) or degree of airflow limitation (the initial FEV1). The magnitude of changes in FEV1 was small and almost always within acceptable limits for reproducibility. Because a larger FVC is due either to an increased inspiration, which could affect the FEV1, or to an increased expiratory reserve volume, which occurs only after the first second, these results emphasize the importance of a maximal inspiration at the start of the test.
To assess whether satisfying American Thoracic Society (ATS) end-of-test spirometry criteria can be enhanced by modifying the patient's expiratory technique, we conducted a cross-over trial of two expiratory techniques in 48 patients with a range of pulmonary functions (Group 1, n = 12: FEV1/FVC < 0.45; Group 2, n = 11: FEV1/FVC, 0.45 to 0.60; Group 3, n = 16: FEV1/FVC, 0.61 to 0.74; Group 4, n = 9: FEV1/FVC > or = 0.75). After randomizing the order of testing, each patient performed three exhalations using a "standard" forced expiratory maneuver and a modified expiratory technique consisting of an initial maximal expiratory effort followed by a "relaxed expiration" for as long as possible. Patients initiated "relaxed expiration" when instructed by the supervising technician, who issued the instruction to relax when expiratory airflow fell to < or = 200 ml/s (as determined by flow-volume loop analysis). ATS end-of-test criteria were satisfied significantly more often using the modified expiratory technique (58.3% of testing sessions) than using the standard technique (18.7% of sessions, p = 0.001) because of prolongation of the forced expiratory time (FET) with the modified technique in all patient groups. In the 38 patients with FEV1/FVC < or = 0.75, the largest FVC and FET rose significantly using the modified expiratory technique, without compromising the largest FEV1 in any group. In patients with FEV1/FVC > or = 0.75, FET increased without concomitant changes in FVC or FEV1.(ABSTRACT TRUNCATED AT 250 WORDS)
To assess the relation between forced expiratory volume in one second (FEV1) and subsequent mortality.
Prospective general population study.
Renfrew and Paisley, Scotland.
7058 men and 8353 women aged 45-64 years at baseline screening in 1972-6.
Mortality from all causes, ischaemic heart disease, cancer, hung and other cancers, stroke, respiratory disease, and other causes of death after 15 years of follow up.
2545 men and 1894 women died during the follow up period. Significant trends of increasing risk with diminishing FEV1 are apparent for both sexes for all the causes of death examined after adjustment for age, cigarette smoking, diastolic blood pressure, cholesterol concentration, body mass index, and social class. The relative hazard ratios for all cause mortality for subjects in the lowest fifth of the FEV1 distribution were 1.92 (95% confidence interval 1.68 to 2.20) for men and 1.89 (1.63 to 2.20) for women. Corresponding relative hazard ratios were 1.56 (1.26 to 1.92) and 1.88 (1.44 to 2.47) for ischaemic heart disease, 2.53 (1.69 to 3.79) and 4.37 (1.84 to 10.42) for lung cancer, and 1.66 (1.07 to 2.59) and 1.65 (1.09 to 2.49) for stroke. Reduced FEV1 was also associated with an increased risk for each cause of death examined except cancer for lifelong nonsmokers.
Impaired lung function is a major clinical indicator of mortality risk in men and women for a wide range of diseases. The use of FEV1 as part of any health assessment of middle aged patients should be considered. Smokers with reduced FEV1 should form a priority group for targeted advice to stop smoking.
To determine the quality of spirometry performed in primary care practice and to assess the impact of formal training.
Randomized, controlled prospective interventional study.
Primary care practice, Auckland City, New Zealand.
Thirty randomly selected primary care practices randomized to "trained" or "usual" groups. One doctor and one practice nurse were nominated to participate from each practice.
"Trained" was defined as participation in an "initial" spirometry workshop at week 0 and a "maintenance of standards" workshop at week 12. "Usual" was defined as no formal training until week 12, when participants they attended the same "initial" workshop provided for the trained group. The study duration was 16 weeks. Each practice was provided with a spirometer to be used at their clinical discretion.
Spirometry data were uploaded weekly and analyzed using American Thoracic Society (ATS) criteria for acceptability and reproducibility. The workshops were assessed objectively with practical and written assessments, confirming a significant training effect. However, analysis of spirometry performed in clinical practice by the trained practitioners revealed three acceptable blows in only 18.9% of patient tests. In comparison, 5.1% of patient tests performed by the usual practitioners had three acceptable blows (p<0.0001). Only 13.5% of patient tests in the trained group and 3.4% in the usual group (p<0.0001) satisfied full acceptability and reproducibility criteria. However, 33.1% and 12.5% of patient tests in the trained and usual groups, respectively (p<0.0001), achieved at least two acceptable blows, the minimum requirement. Nonacceptability was largely ascribable to failure to satisfy end-of-test criteria; a blow of at least 6 s. Visual inspection of the results of these blows as registered on the spirometer for the presence of a plateau on the volume-time curve suggests that < 15% were acceptable.
Although a significant training effect was demonstrated, the quality of the spirometry performed in clinical practice did not generally satisfy full ATS criteria for acceptability and reproducibility. Further study would be required to determine the clinical impact. However, the ATS guidelines allow for the use of data from unacceptable or nonreproducible maneuvers at the discretion of the interpreter. Since most of the failures were end-of-test related, the FEV1 levels are likely to be valid. Our results serve to emphasize the importance of effective training and quality assurance programs to the provision of successful spirometry in primary care practice.
Results from several studies have described a relationship between pulmonary function and both all-cause and cause-specific mortality. The purpose of this study was to investigate the predictive value of pulmonary function by gender after 29 years of follow-up.
Prospective study with 29-year follow-up of the Buffalo Health Study cohort.
Randomly selected sample of 554 men and 641 women, aged 20 to 89 years, from all listed households of the city of Buffalo, NY.
Baseline measurements were performed in 1960 to 1961. Pulmonary function was assessed based on FEV(1) expressed as the normal percent predicted (FEV(1)%pred). FEV(1)%pred adjusted by age, body mass index, systolic BP, education, and smoking status was inversely related to all-cause mortality in both men and women (p<0.01). A sequential survival analysis in participants who had a survival time of at least 5, 10, 15, 20, and 25 years after enrollment in the study was also performed. Except for men who survived for > 25 years, we observed a statistically significant negative association between FEV(1)%pred and all-cause mortality. FEV(1)%pred was also inversely related to ischemic heart disease (IHD) mortality. When participants were divided into quintiles of FEV(1)%pred, participants in the lowest quintile of FEV(1)%pred experienced significantly higher all-cause mortality compared with participants in the highest quintile of FEV(1)%pred. For the entire follow-up period, the adjusted hazard ratios for all-cause mortality were 2.24 (95% confidence interval [CI], 1.60 to 3.13) for men and 1. 81 (95% CI, 1.24 to 2.63) for women, respectively. Hazard ratios for death from IHD in the lowest quintile of FEV(1)%pred were 2.11 (95% CI, 1.20 to 3.71) and 1.96 (95% CI, 0.99 to 3.88) for men and women, respectively.
These results suggest that pulmonary function is a long-term predictor for overall survival rates in both genders and could be used as a tool in general health assessment.
John Hutchinson, a surgeon, recognized that the volume of air that can be exhaled from fully inflated lungs is a powerful indicator of longevity. He invented the spirometer to measure what he called the vital capacity, ie, the capacity to live. Much later, the concept of the timed vital capacity, which became known as the FEV(1), was added. Together, these two numbers, vital capacity and FEV(1), are useful in identifying patients at risk of many diseases, including COPD, lung cancer, heart attack, stroke, and all-cause mortality. This article cites some of the rich history of the development of spirometry, and explores some of the barriers to the widespread application of simple spirometry in the offices of primary care physicians.
Poorly performed spirometry greatly increases the risk of misinterpreting spirometry results. The most common cause of erroneous results is suboptimal patient coaching. Use exaggerated body language to demonstrate each of the 3 phases of the forced vital capacity (FVC) maneuver. The first phase of the maneuver (the maximally deep breath) is the most important and should receive the most emphasis. In the second phase (the blast) startle the patient to prompt maximum flow during the first second. In the third phase do not yell at the patient to keep blowing; instead, draw the patient's attention to the movement of the bell of the volume spirometer, the computer incentive display, or the audio tone of the flow-sensing spirometer, which shows that he or she is continuing to get some air out. Pay attention to the patient's body language as you coach him or her through the 3 phases. Facial expressions and body language are much more important than telling the patient what to do. Use the latest National Health and Nutrition Examination Survey (NHANES III) reference equations and the ratio of forced expiratory volume in the first second to forced expiratory volume in the first 6 seconds (FEV(1)/FEV(6)). Young, old, and sick patients can produce high-quality, reproducible pulmonary function test results. Grade pulmonary function test efforts with the scholastic grading system (A, B, C, D, and F). Implement a centralized spirometry quality assurance program. Test your spirometers daily. Be cautious in making corrections for body-temperature-and-pressure-saturated.
To assess the success rate of smoking cessation with the "minimal intervention strategy" in general practice, and to determine the influence of spirometry on this success rate.
Training in smoking cessation advice was given to 16 general practitioners (GPs). During 12 weeks, these GPs screened their practice population for smoking habits, the degree of dependence on nicotine, and the motivation to quit smoking. Patients willing to stop were randomised to a group that underwent a single office spirometry, or to a control group. The GPs were asked to support the attempts with the minimal intervention strategy. Success rates were compared after 6, 12 and 24 months.
On a population of 5590 patients, 1206 smokers were identified (22%). To the vulnerable group, identified following the Prochaska and Di Clemente scheme, the proposal was made to change smoking behaviour. Two hundred and twenty-one patients undertook an attempt of smoking cessation. Nicotine replacement therapy (NRT) or bupropion was prescribed in 51% of the attempts. Sixty-four sustained quitters were counted after 6 months (29%), 43 after 1 year (19%) and 33 after 2 years (15%). We found a small but statistically non-significant difference in success rate in favour of the group that underwent office spirometry.
GPs can motivate almost 20% of their smoking population to quit smoking. The success rate with the minimal intervention strategy was 19% after 1 year and 15% after 2 years. We found no arguments in favour of confronting smokers with their lung function as a tool for enhancing smoking cessation.
To the Editors:
“The devil's in the details” of the new American Thoracic Society (ATS)/European Respiratory Society (ERS) document regarding the interpretation of pulmonary function test (PFT) results 1. As a member of the Task Force, I was happy for the opportunity to help standardise the way in which clinically important PFTs are performed and interpreted. Unfortunately, the group spent almost all of the 3 yrs reaching an agreement (or compromise) on the mechanics of making accurate spirometry, diffusing capacity of the lung for carbon monoxide and lung volume measurements, but left inadequate time to thoroughly discuss the more important but controversial aspects of …
In November 2005, the American Thoracic and European Respiratory Societies jointly published a statement proposing a new interpretation scheme for pulmonary function tests. The practical effect of adoption of these new guidelines has not yet been studied. The purpose of the current study was to address the effects of the new interpretation strategy on the relative distribution of obstructive and restrictive diagnoses in patients evaluated at a single academic medical center laboratory.
Pulmonary functions tests from 319 patients were analyzed according to four different interpretation schemes. The number of patients classified according to each as obstructed, restricted, neither, or both were compared, and factors associated with a change in classification using the different approaches were examined.
Although similar proportions of patients were identified as restricted using either the "GOLD" scheme (23%) or new approaches (22%), significantly more (P<0.005) were defined as obstructed using the newly proposed scheme (44% versus 33%). Additionally, 36% of subjects defined as obstructed using either the traditional or new schemes were classified differently (i.e., either "gained" or "lost" the diagnosis of obstruction) using the new approach. Women were significantly more likely than men to have a change in classification.
The new interpretation scheme leads to a diagnosis of obstruction in a greater proportion of patients undergoing pulmonary function testing. The clinical significance of this finding has not yet been validated, and its economic impact remains to be assessed.
Standardisation of spirometry
- Mr Miller
- J Hankinson
- V Brusasco
Miller MR, Hankinson J, Brusasco V, et al. Standardisation of
spirometry. Eur Respir J 2005; 26:319 –338
Appropriate coding for critical care services and pulmonary medicine
- E Diamond
Diamond E. Pulmonary function and exercise testing. In:
Manaker S, ed. Appropriate coding for critical care services
and pulmonary medicine 2007. New Berlin, WI: Northbrook,
2007; 161-175
Lung function testing: selection of reference values and interpretative strategies: American Thoracic Society
Lung function testing: selection of reference values and
interpretative strategies: American Thoracic Society. Am Rev
Respir Dis 1991; 144:1202-1218
Spirometric reference values from a sample of the general U.S. population
- J L Hankinson
- J R Odencrantz
- K B Fedan
Hankinson JL, Odencrantz JR, Fedan KB. Spirometric reference values from a sample of the general U.S. population.
Am J Respir Crit Care Med 1999; 159:179 -187
- M Beebe
- J A Dalton
- M Espronceda
Beebe M, Dalton JA, Espronceda M, et al. CPT 2007
professional edition. Chicago, IL: American Medical Association, 2007; 400
Spirometric reference values from a sample of the general U.S. population
- Hankinson
Standardisation of spirometry
- Miller