[Show abstract][Hide abstract] ABSTRACT: Background and objectiveDuring forced expiration, alveolar pressure (PALV) increases and intrathoracic gas is compressed. Thus, 1-s forced expiratory volume measured by spirometry (FEV1-sp) is smaller than 1-s forced expiratory volume measured by plethysmography (FEV1-pl). Thoracic gas compression volume (TGCV) depends on the amount of gas within the lung when expiratory flow limitation occurs in the airways. We therefore tested the hypothesis that bronchoconstrictor and bronchodilator responses using FEV1-sp are biased by height and gender, which are major determinants of lung volume.Methods
We studied 54 asthmatics during methacholine challenge and 55 subjects with airway obstruction (FEV1-sp increase >200 mL and >12% after salbutamol) measuring at the same time FEV1-sp or FEV1-pl.ResultsDuring methacholine challenge, TGCV increased more in males than females, correlated with PALV, total lung capacity (TLC) and height, and the provocative dose was lower using FEV1-sp than FEV1-pl. With salbutamol, FEV1-pl increased <200 mL and <12% in 28 subjects, predominantly tall males, with larger TLC, TGCV and PALV.Conclusions
Bronchoconstrictor and bronchodilator responses are overestimated by standard spirometry in subjects with larger lungs because of TGCV.
[Show abstract][Hide abstract] ABSTRACT: Little is known about the response of variable orifice peak flow meters to high frequency flow input. The purpose of this study was to define and test dynamic requirements for such peak flow meters. In a population sample we measured peak expiratory flow (PEF), rise time (t r), from 10-90% PEF and the duration of the flow in excess of 97.5, 95 and 90% of PEF, by use of a carefully calibrated Fleisch pneumotachograph with known and adequate frequency response. Three peak flow meters (Mini Wright, Vitalograph and Ferraris) were tested with an explosive decompression calibrator adjusted to values for PEF and t r as close as possible to the 95th and 5th percentile values, respectively, both for males and females, and with peak durations between 5 and more than 100 ms. The 95th percentile values of PEF were 597 L·min-1 for females and 894 L·min-1 for males. The 5th percentile values of t r were, respectively 55 and 45 ms. The duration of flow in excess of 95% PEF was longer than 10 ms in 99% of the subjects. For all meters, the deviation of PEF corrected for alinearity were less than 5% at a peak duration of 10 ms. We conclude that PEF, rise time, and peak duration can be used for description of dynamic properties of variable orifice meters, and that the tested meters had a satisfactory frequency response for recording PEF in mostly normal subjects. The widespread use of portable peak flow meters for clinical, occupational, and epidemiological purposes has made it necessary to establish calibration standards to be used for quality control for the manufacturers, and to ensure for the users that the values obtained can be used in treatment plans and for comparison between studies. The orifice type peak flow meters seem to have an excellent repeatability. Until recently, the scales have not been calibrated in terms of true flow, but this can easily be done (1). Previous calibration studies have been performed by use of slowly rising flows (1). Little is known about the response of the meters to higher frequency content in the input. Due to the nature of the meters, conventional testing by means of sine wave inputs with increasing frequencies cannot be used. The purpose of the present study is, therefore, to present and test an alternative method to determine whether the dynamic response of the peak flow meters is satisfactory. The study had two parts. In the first part, we tried to define the requirements to be met by a peak flow meter. This was done by analysis of data from subjects who performed peak flow manoeuvres with a linear, low- resistance pneumotachograph, with known and sat- isfactory frequency response. For these subjects, the 95th percentile of peak expiratory flow (PEF), the 5th percentile of rise time (t r) from 10-90% of PEF, and PEF duration were determined to define the requirements. In the second part, we tested different makes of variable orifice peak flow meters for adequate response to these values and different durations of the peak ("dwell time").
[Show abstract][Hide abstract] ABSTRACT: Spirometric lung function is partly determined by sex, age and height (Ht). Commonly, lung function is expressed as a percentage of the predicted value (PP) in order to account for these effects. Since the PP method retains sex, age and Ht bias, forced expiratory volume in 1 s (FEV(1)) standardised by powers of Ht and by a new sex-specific lower limit (FEV(1) quotient (FEV(1)Q)) were investigated to determine which method best predicted all-cause mortality in >26,967 patients and normal subjects. On multivariate analysis, FEV(1)Q was the best predictor, with a hazard ratio for the worst decile of 6.9 compared to 4.1 for FEV(1)PP. On univariate analysis, the hazard ratios were 18.8 compared to 6.1, respectively; FEV(1) x Ht(-3) was the next-best predictor of survival. Median survival was calculated for simple cut-off values of FEV(1)Q and FEV(1) x Ht(-3). These survival curves were accurately fitted (r(2) = 1.0) by both FEV(1)Q and FEV(1) x Ht(-3) values expressed polynomially, and so an individual's test result could be used to estimate survival (with sd for median survival of 0.22 and 0.61 yrs, respectively). It is concluded that lung function impairment should be expressed in a new way, here termed the FEV(1)Q, or, alternatively, as FEV(1) x Ht(-3), since these indices best relate spirometric lung function to all-cause mortality and survival.
European Respiratory Journal 10/2009; 35(4):873-82. · 6.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: c1 Address for correspondence: Dr MR Miller, Department of Medicine, University of Birmingham, Selly Oak Hospital, Birmingham B29 6JD, UK. Email: email@example.com
[Show abstract][Hide abstract] ABSTRACT: The prevalence of airway obstruction varies widely with the definition used.
To study differences in the prevalence of airway obstruction when applying four international guidelines to three population samples using four regression equations.
We collected predicted values for forced expiratory volume in 1 s/forced vital capacity (FEV(1)/FVC) and its lower limit of normal (LLN) from the literature. FEV(1)/FVC from 40 646 adults (including 13 136 asymptomatic never smokers) aged 17-90+years were available from American, English and Dutch population based surveys. The prevalence of airway obstruction was determined by the LLN for FEV(1)/FVC, and by using the Global Initiative for Chronic Obstructive Lung Disease (GOLD), American Thoracic Society/European Respiratory Society (ATS/ERS) or British Thoracic Society (BTS) guidelines, initially in the healthy subgroup and then in the entire population.
The LLN for FEV(1)/FVC varied between prediction equations (57 available for men and 55 for women), and demonstrated marked negative age dependency. Median age at which the LLN fell below 0.70 in healthy subjects was 42 and 48 years in men and women, respectively. When applying the reference equations (Health Survey for England 1995-1996, National Health and Nutrition Examination Survey (NHANES) III, European Community for Coal and Steel (ECCS)/ERS and a Dutch population study) to the selected population samples, the prevalence of airway obstruction in healthy never smokers aged over 60 years varied for each guideline: 17-45% of men and 7-26% of women for GOLD; 0-18% of men and 0-16% of women for ATS/ERS; and 0-9% of men and 0-11% of women for BTS. GOLD guidelines caused false positive rates of up to 60% when applied to entire populations.
Airway obstruction should be defined by FEV(1)/FVC and FEV(1) being below the LLN using appropriate reference equations.
[Show abstract][Hide abstract] ABSTRACT: The acute effects of pure inhaled glucan on respiratory inflammation remain inconclusive and not sufficiently examined with regards to the simultaneous interaction of glucan, endotoxin (lipopolysaccharide, LPS), and house dust in airway inflammation. This study aims at determining effects of simultaneous exposure to office dust and glucan on nasal and pulmonary inflammation. This is relevant for humans with occupational exposure in waste handling and farming and buildings with mold problems. Office dust collected from Danish offices was spiked with 1% (1-3)-beta-glucan (curdlan). Guinea pig nasal cavity volume was measured by acoustic rhinometry (AR) and animals were exposed by inhalation for 4 h to curdlan-spiked dust, unspiked dust, purified air (negative controls), or LPS (positive controls). After exposure (+5 h) or the following day (+18 h), measurements were repeated by AR and followed by bronchoalveolar lavage (BAL). Total and differential cell counts, interleukin (IL)-8 in BAL fluid, and change in nasal volume were compared between groups. A 5-10% increase in nasal volume was seen for all groups including clean air except for a significant 5% decrease for spiked-dust inhalation (+18 h). No marked differences were observed in BAL cells or IL-8 except in LPS-exposed controls. The delayed decrease of nasal cavity volume after exposure to glucan spiked dust suggests a slow effect on the upper airways for curdlan and office dust together, though no pulmonary response or direct signs of inflammation were observed. Glucan-spiked office dust exposures produced a delayed nasal subacute congestion in guinea pigs compared to office dust alone, but extrapolated to nasal congestion in humans, paralleling the nasal congestion seen in human volunteers exposed to the same dust, this may not have clinical importance.
Journal of Toxicology and Environmental Health Part A 12/2007; 70(22):1923-8. · 1.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Sixteen healthy nonsmoking subjects (7 women), 21-49 yr old, were exposed in a climate chamber to either clean air or 300 parts/billion ozone on 4 days for 5 h each day. Before each exposure, the subjects had been pretreated with either oxidants (fish oil) or antioxidants (multivitamins). The study design was double-blind crossover with randomized allocation to the exposure regime. Full and partial flow-volume curves were recorded in the morning and before and during a histamine provocation at the end of the day. Nasal cavity volume and inflammatory markers in nasal lavage fluid were also measured. Compared with air, ozone exposure decreased peak expiratory flow, forced expiratory volume in 1 s, and forced vital capacity (FVC), with no significant effect from the pretreatment regimens. Ozone decreased the ratio of maximal to partial flow at 40% FVC by 0.08 +/- 0.03 (mean +/- SE, analysis of variance: P = 0.018) and at 30% FVC by 0.10 +/- 0.05 (P = 0.070). Ozone exposure did not significantly increase bronchial responsiveness, but, after treatment with fish oil, partial flows decreased more than after vitamins during the histamine test, without changing the maximal-to-partial flow ratio. The decreased effect of a deep inhalation after ozone exposure can be explained by changes in airway hysteresis relative to parenchymal hysteresis, due either to ozone-induced airway inflammation or to less deep inspiration after ozone, not significantly influenced by multivitamins or fish oil.
Journal of Applied Physiology 06/2004; 96(5):1651-7. · 3.48 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Recent evidence suggests that the frequency response requirements for peak expiratory flow (PEF) meters are higher than was first thought and that the American Thoracic Society (ATS) waveforms to test PEF meters may not be adequate for the purpose.
The dynamic response of mini-Wright (MW), Vitalograph (V), TruZone (TZ), MultiSpiro (MS) and pneumotachograph (PT) flow meters was tested by delivering two differently shaped flow-time profiles from a computer controlled explosive decompression device fitted with a fast response solenoid valve. These profiles matched population 5th and 95th centiles for rise time from 10% to 90% of PEF and dwell time of flow above 90% PEF. Profiles were delivered five times with identical chamber pressure and solenoid aperture at PEF. Any difference in recorded PEF for the two profiles indicates a poor dynamic response.
The absolute (% of mean) flow differences in l/min for the V, MW, and PT PEF meters were 25 (4.7), 20 (3.9), and 2 (0.3), respectively, at PEF approximately 500 l/min, and 25 (10.5), 20 (8.7) and 6 (3.0) at approximately 200 l/min. For TZ and MS meters at approximately 500 l/min the differences were 228 (36.1) and 257 (39.2), respectively, and at approximately 200 l/min they were 51 (23.9) and 1 (0.5). All the meters met ATS accuracy requirements when tested with their waveforms.
An improved method for testing the dynamic response of flow meters detects marked overshoot (underdamping) of TZ and MS responses not identified by the 26 ATS waveforms. This error could cause patient misclassification when using such meters with asthma guidelines.