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Maximal inspiratory and expiratory pressures in men with chronic obstructive pulmonary disease: A cross-sectional study

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Introduction: Respiratory muscle dysfunction is a cardinal feature in chronic obstructive pulmonary disease (COPD) contributing to decreased exercise capacity and pulmonary function test (PFT) limitation with progression of the disease. Maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) are reliable parameters for assessing the respiratory muscle strength. Aims: This study aims to measure maximal inspiratory and expiratory pressures in male COPD patients, to determine their correlates, and to study the relationship between the severity of COPD and respiratory muscle strength. Patients and Methods: This was an observational, cross-sectional study. A total of 100 males, who were known COPD patients and who were clinically stable, were recruited. Both inpatients and outpatients were studied. Spirometric PFT test was done, and MIP and MEP were measured using respiratory pressure meter. Descriptive statistics and Pearson's correlation were used. Results: The mean (± standard deviation) MIP and MEP were 47.73 (±19.6) cm H2O and 60.76 (±11.6) cm H2O, respectively. MIP and MEP showed a highly significant correlation (P < 0.001) with forced expiratory volume at 1 s (FEV1) and forced vital capacity. The correlation of MIP and MEP with FEV1shows a positive linear trend, and the MEP values were higher than MIP values. There was a decrease in MIP and MEP with increasing severity of COPD. Conclusion: MIP decreases with progression of the disease, and thus, inspiratory muscle training should be included in a pulmonary rehabilitation program.
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88
Original Article
IntroductIon
According to the World Health Organization, it is estimated
that chronic obstructive pulmonary disease (COPD) will
be the third‑most common cause of death and fth‑most
common cause of disability in the world by 2020.[1] COPD
is considered as a respiratory disease with multiple systemic
pathological components. Musculoskeletal system is often
involved in patients with COPD, contributing to decrease in
effort capacity and quality of life.[2] In this context, inspiratory
muscle function is frequently affected. This may be due to
chronic systemic inammation inducing pathological changes
in the thoracic cage or producing structural alteration in
the respiratory muscles.[3‑5] Decrease in inspiratory muscle
function represents an important prediction factor for the
survival rate in COPD patients.[6]
The imbalance between respiratory muscle function and load is
an important determinant of dyspnea and hypercapnia.[7] While
inspiratory muscles reach their optimal force‑length relationship
at low pulmonary volumes, the expiratory muscles reach it at
high lung volumes.[8] Respiratory muscle dysfunction is a cardinal
feature of acute and chronic respiratory failure in COPD.[9]
Hypercapneic respiratory failure following inspiratory muscle
weakness is found to be the leading cause of death in COPD
patients.[10,11] As the most of the lung and airway derangements
are irreversible in COPD, all therapeutic interventions must be
aimed at strengthening the respiratory muscles.[7]
The respiratory muscle strength is best assessed regarding
maximal inspiratory pressure (MIP) and maximal expiratory
Maximal Inspiratory and Expiratory Pressures in Men with
Chronic Obstructive Pulmonary Disease: A Cross‑Sectional
Study
Veena Kiran Nambiar, Savita Ravindra, B. S. Nanda Kumar1
Departments of Physiotherapy and 1Community Medicine, Ramaiah Medical College and Hospitals, Bengaluru, Karnataka, India
Introduction: Respiratory muscle dysfunction is a cardinal feature in chronic obstructive pulmonary disease (COPD) contributing to decreased
exercise capacity and pulmonary function test (PFT) limitation with progression of the disease. Maximal inspiratory pressure (MIP) and maximal
expiratory pressure (MEP) are reliable parameters for assessing the respiratory muscle strength. Aims: This study aims to measure maximal
inspiratory and expiratory pressures in male COPD patients, to determine their correlates, and to study the relationship between the severity
of COPD and respiratory muscle strength. Patients and Methods: This was an observational, cross‑sectional study. A total of 100 males, who
were known COPD patients and who were clinically stable, were recruited. Both inpatients and outpatients were studied. Spirometric PFT
test was done, and MIP and MEP were measured using respiratory pressure meter. Descriptive statistics and Pearson’s correlation were used.
Results: The mean (± standard deviation) MIP and MEP were 47.73 (±19.6) cm H2O and 60.76 (±11.6) cm H2O, respectively. MIP and MEP
showed a highly signicant correlation (P < 0.001) with forced expiratory volume at 1 s (FEV1) and forced vital capacity. The correlation of
MIP and MEP with FEV1 shows a positive linear trend, and the MEP values were higher than MIP values. There was a decrease in MIP and
MEP with increasing severity of COPD. Conclusion: MIP decreases with progression of the disease, and thus, inspiratory muscle training
should be included in a pulmonary rehabilitation program.
Keywords: Chronic obstructive pulmonary disease, maximal expiratory pressure, maximal inspiratory pressure, pulmonary function test
Address for correspondence: Dr. Veena Kiran Nambiar,
Department of Physiotherapy, Ramaiah Medical College and Hospitals,
Bengaluru ‑ 560 054, Karnataka, India.
E‑mail: veenakiran_nambiar@yahoo.co.in
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DOI:
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How to cite this article: Nambiar VK, Ravindra S, Kumar BS. Maximal
inspiratory and expiratory pressures in men with chronic obstructive
pulmonary disease: A cross‑sectional study. Indian J Respir Care
2018;7:88‑92.
Abstract
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Nambiar, et al.: Respiratory muscle pressures in male COPD patients
Indian Journal of Respiratory Care ¦ Volume 7 ¦ Issue 2 ¦ July-December 2018 89
pressure (MEP). MIP is the maximum negative pressure that
can be generated from one inspiratory effort starting from
functional residual capacity (FRC) or residual volume (RV).
MEP measures the maximum positive pressure that can be
generated from one expiratory effort starting from total lung
capacity (TLC) or FRC.
This study aimed to measure the respiratory muscle strength
using MIP and MEP in clinically stable male COPD patients,
to determine the correlates for MIP and MEP, and to study the
relationship between severity of COPD (GOLD Criteria) and
respiratory muscle strength.
PatIents and Methods
This was a cross‑sectional, observational study. Convenience
sampling was used. Participation was purely on voluntary basis.
After obtaining informed consent, 100 males, who were known
COPD patients, both inpatients and outpatients, and who were
clinically stable, were recruited. Ethical clearance was obtained
from the Ethical Review Board of the Institution. This study
was conducted on male patients only to avoid intergender
differences in MIP and MEP. A total of 99 patients completed
the MIP and MEP assessment phase. There was a dropout of
one patient due to noncompliance and thus incomplete data.
Patients with primary muscular/neuromuscular diseases and
clinically signicant comorbidities that could affect the test
results and COPD patients in acute exacerbation were excluded
from the study.
For all patients, demographic data were obtained. Spirometric
pulmonary function (PFT) was done using Schiller machine.
Best of the three successive test readings were taken as a nal
result, and the primary values, i.e., forced vital capacity (FVC),
forced expiratory volume in the 1 s (FEV1), and FEV1/FVC
ratios were recorded. Anthropometry was done by measuring
weight in kilogram (kg) and height with a stadiometer and body
mass index (BMI) was calculated according to the formula
kg/m2. MIP and MEP were determined using portable pressure
meter (Micro respiratory pressure meter). MIP was measured
from FRC or RV, and MEP was measured starting from TLC. All
recordings were taken in the sitting posture. Maximum of three
trials were given with an interval of 1 min between the trials for
each subject. The highest value was accepted for computation.
The collected data were coded, tabulated, and introduced to
PC using SPSS 16 (SPSS Inc., SPSS for Windows, Chicago).
Descriptive statistics were used to obtain mean and standard
deviation (±SD) for parametric numerical data, namely, age,
height, weight, BMI, FEV1, FVC, FEVI/FVC, MIP, and MEP.
Pearson’s correlation was used to assess the relation between
MIP and MEP with independent variables such as age, height,
weight, BMI, FEV1%, FVC%, and FEVI/FVC%.
results
A total of 99 known COPD male patients, who were clinically
stable, completed the measurement process in this study. The
mean age of the COPD population studied was 62.90 ± 6.23 years.
PFT measured by spirometry showed a mean (±SD) FEV1%
of 47.81 ± 23.9, mean (±SD) FVC% of 63.99 ± 22.08, and
mean (±SD) FEV1/FVC% of 67.60 ± 21.99. Maximum
inspiratory and expiratory pressures were a mean (±SD)
47.73 ± 19.6 and 60.76 ± 11.6 cm H2O, respectively, [Table 1].
Pearson’s correlation‑coefficient was used to assess the
relation between MIP and MEP with independent variables
such as age, height, weight, BMI, FEV1%, FVC%, and
FEVI/FVC% [Tables 2 and 3]. It was seen that MIP showed
a highly signicant correlation (P < 0.001) with both FEV1%
and FVC%. The correlation between MIP and FEV1 shows a
positive linear trend and more clustering of MIP toward FEV1
at 25%–75% [Figure 1]. MEP showed a highly signicant
correlation (P < 0.001) with weight, FEV1%, and FVC% and a
moderately signicant correlation (P < 0.05) with BMI [Table 3].
A positive linear correlation was seen between MEP
and FEV1, and the MEP P values were higher than MIP
P values [Figure 2]. A negative correlation existed between
MIP and MEP with age [Figures 3 and 4]. With increase in
age, there was a decrease in both MIP and MEP. According to
Table 1: Descriptive statistics (n=99)
Mean±SD Minimum Maximum
Age (years) 62.90±6.23 50 85
Height (cm) 165.74±6 140 177
Weight (kg) 61.60±11 30 120
FEV1 (%) 47.81±24 20 127
FVC (%) 63.99±22 28 135
FEV1/FVC (%) 67.60±22 20 114
MIP (cm H2O) 47.73±19.62 18 127
MEP (cm H2O) 60.76±11.64 40 128
BMI (kg/m2) 22.4±3.55 10.73 41.52
FEV1: Forced expiratory volume in the 1 s, FVC: Forced vital capacity,
MIP: Maximum inspiratory pressure, MEP: Maximum expiratory
pressure, BMI: Body mass index, SD: Standard deviation
Table 2: Correlation between maximum inspiratory
pressure and age, height, weight, body mass index,
forced expiratory volume in the 1 s percentage, forced
vital capacity percentage, and forced expiratory volume
in the 1 s/forced vital capacity percentage
Variable MIP (cm H2O)
r P
Age (years) −0.051 0.613
Height (cm) 0.194 0.054
Weight (kg) 0.151 0.137
BMI (kg/m2) 0.101 0.318
FEV1 (%) 0.616 <0.001*
FVC (%) 0.535 <0.001*
FEV1/FVC (%) 0.128 0.207
* Level of signicance set at P < 0.05. BMI: Body mass index, FEV1: Forced
expiratory volume in the 1 s, FVC: Forced vital capacity, MIP: Maximum
inspiratory pressure
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Nambiar, et al.: Respiratory muscle pressures in male COPD patients
Indian Journal of Respiratory Care ¦ Volume 7 ¦ Issue 2 ¦ July-December 2018
90
the value of FEV1%, the results revealed that 30% of COPD
patients had very severe airow obstruction (FEV1 <30%),
35% had severe airow obstruction (FEV1 30%–50%), 25%
had moderate airow obstruction (FEV1 50%–80%), and 9% of
patients had mild airow obstruction (FEV1 >80%) [Table 4].
As the severity of airow obstruction is progressively increasing,
the value of MIP and MEP were signicantly lowered in
patients with severe and very severe airway obstruction with a
statistically signicant difference between the levels of airway
obstruction concerning MIP value (F‑test‑29.31, P < 0.001)
and MEP value (F‑test‑15.67, P < 0.001) [Table 5].
It is seen from the box and error plot that there was a
decrease in MIP and MEP with increasing severity of COPD
[Figures 5 and 6]. There is a positive correlation between MIP
and MEP [Figure 7].
dIscussIon
The results show that the MIP values among male COPD
patients were much lower than their age‑matched controls.[12]
The MIP (inspiratory muscle strength) values were more
affected when compared to MEP (expiratory muscle strength)
Figure 4: Scatter plot depicting the correlation between maximal expiratory
pressure and age
Figure 3: The correlation between maximal inspiratory pressure and age
Table 3: Correlation between maximum expiratory
pressure and age, height, weight, body mass index,
forced expiratory volume in the 1 s percentage, forced
vital capacity percentage, and forced expiratory volume
in the 1 s/forced vital capacity percentage
Variable MEP (cm H2O)
r P
Age (years) −0.190 0.059
Height (cm) 0.172 0.089
Weight (kg) 0.273** <0.006
BMI 0.233* <0.020
FEV1 (%) 0.505** <0.001
FVC (%) 0.379** <0.001
FEV1/FVC (%) 0.222 0.027
**P<0.001, *P<0.05. BMI: Body mass index, FEV1: Forced expiratory
volume in the 1 s, FVC: Forced vital capacity, MEP: Maximum
expiratory pressure
Figure 1: Scatter plot depicting the correlation between maximal
inspiratory pressure and FEV1
Figure 2: Scatter plot depicting the correlation between Maximal expiratory
pressure and FEV1
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Nambiar, et al.: Respiratory muscle pressures in male COPD patients
Indian Journal of Respiratory Care ¦ Volume 7 ¦ Issue 2 ¦ July-December 2018 91
values in COPD patients. There was a decline in MIP and MEP
with increase in age.
MIP and MEP correlated with FEV1, i.e., when FEV1 reduced,
MIP and MEP also reduced signicantly. The results obtained
in the present study were in parallel with some of the recent
literature. In addition, it was seen that respiratory muscle
weakness occurs early in COPD with a decline in MIP and
MEP as the severity of the disease (GOLD Criteria) progressed.
The results show that the MIP values among COPD patients
were much lower than their age‑matched normal people.
However, the MEP values did not show much of a difference
in the (60–70) years of age group. The MIP (inspiratory
muscle strength) values were more affected when compared
to MEP (expiratory muscle strength) values in COPD
patients. According to a study done by Voicu et al., MIP was
signicantly decreased in moderate to severe stages of COPD
which correlated with decreased effort capacity as measured
by 6‑min walk distance.
The lean body mass decreases with increase in the severity
of the disease. Thus, there is decreased muscle strength
which is induced by various factors such as oxidative stress,
inammatory status, metabolic and nutritional dysfunction,
bed rest, and prolonged steroid treatment.[13] MIP and MEP
indicate the state of respiratory muscle strength and is related
to the severity of COPD and spirometric indices.
MIP negatively correlated with age. Due to the aging process,
there is a reduction in the diaphragm and respiratory muscle
mass. Therefore, MIP was further compromised in COPD
patients.[14] Khalil et al. studied MIP and MEP in patients with
COPD being 43.6% ± 26.9% and 46.8% ± 26%, respectively,
which was similar to this present study.[15] It was concluded in
a study done by Hans‑Joachim Kabitz that inspiratory muscle
strength decreases in COPD patients with increasing disease
severity. This could be attributed to two factors: compromised
diaphragmatic contractility in the early stages and further
reduction in inspiratory muscle strength following hyperination
in advanced COPD. All these lead to decreased exercise capacity,
impaired gas exchange, and increased dyspnea. Thus, the two
mechanisms responsible for decreased MIP in COPD are
decreased diaphragmatic contractility which begins in the early
stages of the disease, which is independent of hyperination,
and second, decreased diaphragmatic force generation due to
hyperination in severe to very severe stages of the disease.[16]
Limitations of the study
In this study, other factors, such as smoking, medication
compliance, and comorbidities were not considered, which
probably could have an inuence on MIP and MEP.
conclusIon
COPD is a cause of respiratory muscle weakness and it occurs
early in the disease. There is a decrease in respiratory muscle
strength, especially inspiratory muscle strength (MIP) with
progression of the disease.
Table 4: The degree of airflow obstruction in the study
population
Degree of airflow obstruction (n=99) Frequency, n (%)
Mild (FEV1% >80) 9 (9.1)
Moderate (FEV1% [50‑80]) 25 (25.3)
Severe (FEV1% [30‑50]) 35 (35.4)
Very severe (FEV1% <30) 30 (30.3)
FEV1: Forced expiratory volume in the 1 s
Table 5: Comparison between the chronic obstructive pulmonary disease subjects according to the level of severity
concerning the maximum inspiratory pressure and maximum expiratory pressure (cm H2O)
COPD stage (GOLD criteria)
Mild Moderate Severe Very severe
MIP
Range (mean±SD)* 69.54‑110.46 (90±26.6) 41.27‑50.89 (46.08±11.64) 42.1‑46.0 (44.09±5.7) 33.89‑47.45 (40.67±18.1)
MEP
Range (mean±SD)* 62.7‑100.14 (81.44±24.3) 57.45‑62.5 (60±6.1) 56.9‑61.7 (59.3±6.8) 54.03‑59.64 (56.83±7.5)
* Compared using ANOVA and the difference was found to be signicant with P<0.001. SD: Standard deviation, COPD: Chronic obstructive pulmonary
disease, MIP: Maximum inspiratory pressure, MEP: Maximum expiratory pressure
Figure 5: Box error plot showing the correlation between maximal
inspiratory pressure and different stages of chronic obstructive pulmonar y
disease severity (GOLD criteria). 1 ‑ Mild, 2 ‑ Moderate, 3 ‑ Severe,
4 ‑ Very Severe
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Nambiar, et al.: Respiratory muscle pressures in male COPD patients
Indian Journal of Respiratory Care ¦ Volume 7 ¦ Issue 2 ¦ July-December 2018
92
Implications
Respiratory muscle strength assessment in the form of MIP
and MEP should be carried out in a COPD patient, and thus,
respiratory muscle training should be included in a pulmonary
rehabilitation program.
Figure 7: Scatter plot depicting the correlation between Maximal
inspiratory pressure and Maximal expiratory pressure
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conicts of interest.
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Figure 6: Box error plot showing the correlation between Maximal
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disease severity (GOLD criteria). 1 ‑ Mild, 2 ‑ Moderate, 3 ‑ Severe,
4 ‑ Very Severe
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... 25 Furthermore, according to a study by Nambiar et al and Vyas et al, MRPs in COPD patients are much lower than in healthy people, which has a negative impact on physical functioning. 26 Our findings revealed a significant gender effect, which is consistent with previous findings in the literature, in which males had higher MIP and MEP values than females. 17,27 Men had MRP values that were 10-15% higher than female participants in our study. ...
... 31 Physical activity components measured with the GPAQ had no correlation with MRPs or MVV in our study. There are a few studies that support our findings that MIP, MEP, and MVV have no relationship with moderate to severe physical activity, 26,32 whereas other studies found a positive correlation. 33 MIP, MEP, and PFT values (FVC, FEV1) showed a moderately significant relationship, which is consistent with previous research that found a strong correlation between MRPs and FVC and FEV1. ...
... 25,33 MIP, MEP, and FEV1, FVC in COPD patients showed a highly significant correlation with a positive linear trend. 26 MIP and MEP had a moderate relationship (r= 0.27, p=0.01) with MVV, which is consistent with a study by Pradeep Kumar et al, who found the highest correlation between MVV and MRPs. 26 Because these two factors are linked, respiratory muscle endurance measured by MVV may have a direct impact on respiratory muscle strength measured by MIP and MEP. ...
Article
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Background: Maximum inspiratory pressure (MIP), maximum expiratory pressure (MEP) and maximum voluntary ventilation (MVV) measurements assist in determining the respiratory muscle strength and endurance. These determinants of respiratory muscles vary significantly by age, gender, height, and ethnic origin. Normative values for maximum respiratory pressures (MRPs) and MVV would aid in evaluating respiratory muscle function in athletes, estimating performance, and assisting in rehabilitation. In addition, the reference values may aid in determining the efficacy of therapeutic interventions in young people with chronic respiratory diseases. The purpose of this study was to see how respiratory muscle strength indices correlated with anthropometric and physical activity characteristics in young Arabs. Methodology: The study included 80 male volunteers and 85 female volunteers ranging in age from 18 to 30 years. MicroRPM was used to measure MIP and MEP, and pulmonary function test data, including MVV values, were recorded. All subjects completed the Global Physical Activity Questionnaire (GPAQ) and anthropometric measurements. Unpaired t-tests or Mann-Whitney U-tests were used to determine male-female differences. Using the Pearson correlation coefficient and Spearman Rho correlation coefficient tests, MIP and MEP values were correlated with body composition and physical activity. Using stepwise multiple linear regression analysis, the relationships between respiratory function (MVV, MIP, and MEP) and PFT values (FVC, FEV1, and FEV1/FVC), physical activity, and sedentary behavior were investigated. Results: MIP, MEP, and MVV values were significantly lower in females than in males. MIP, MEP, and MVV values had a moderate correlation with forced vital capacity, forced expiratory volume in 1 second, and height, but not with weight, BMI, or GPAQ. Age, gender, and body mass index were found to be significant predictors of maximal respiratory pressures in a young Arab population. Conclusion: Maximum respiratory pressures and maximal voluntary ventilation were significantly lower in young Arabs than in other ethnic groups; these values were influenced by gender and height but not by levels of physical activity.
... It is worthy to comment on the interesting study by Nambiar et al. on the maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) in Indian patients with chronic obstructive pulmonary disease (COPD) published in the latest issue of Indian J Resp Care. [1] Using respiratory pressure meter to measure spirometric pulmonary function test (PFT), the authors found that the correlation of MIP and MEP with forced expiratory volume in the 1 s showed a positive linear trend, and the MEP values were higher than MIP values. There was a decrease in MIP and MEP with increasing severity of COPD. ...
... Sir, It is worthy to comment on the interesting study by Nambiar et al. on the maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) in Indian patients with chronic obstructive pulmonary disease (COPD) published in the latest issue of Indian J Resp Care. [1] Using respiratory pressure meter to measure spirometric pulmonary function test (PFT), the authors found that the correlation of MIP and MEP with forced expiratory volume in the 1 s showed a positive linear trend, and the MEP values were higher than MIP values. There was a decrease in MIP and MEP with increasing severity of COPD. ...
... There was a decrease in MIP and MEP with increasing severity of COPD. [1] I presume that such results ought to be cautiously taken. As a limitation in the study, the authors mentioned that other factors, such as smoking, medication compliance, and comorbidities were not considered, which probably could have an influence on MIP and MEP. ...
... This test of breathing muscles is a routine procedure in the diagnosis of certain pulmonary diseases, specifically in patients with suspected respiratory muscle weakness. Some examples of very prevalent diseases which alter MIP/MEP values are chronic obstructive pulmonary disease (COPD), neuromuscular diseases, such as multiple sclerosis, or chronic heart failure (Laghi and Tobin, 2003;Kelley and Ferreira, 2017;Nambiar et al., 2018;Laveneziana et al., 2019). ...
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The measurement of maximal inspiratory (MIP) and maximal expiratory (MEP) pressures is a widely used technique to non-invasively evaluate respiratory muscle strength in clinical practice. The commercial devices that perform this test range from whole body plethysmographs to portable spirometers, both expensive and include a wide range of other respiratory tests. Given that a portable, low-cost, and specific option for MIP and MEP measuring device is not currently available in the market. A high-performance and easy-to-build prototype has been developed and the detailed technical information to easily reproduce it is freely released. A novel device is based on an Arduino microcontroller with a digital display, an integrated pressure transducer, and three-dimensional (3D) printed enclosure (total retail cost €80). The validation of the device was performed by comparison with a laboratory reference setting, and results showed accuracy within ±1%. As the device design is available according to the open-source hardware approach, measuring MIP/MEP can greatly facilitate easily available point-of-care devices for the monitoring of patients and, most important, for making this lung function measurement tool affordable to users in low- and middle-income countries.
... 17 However, the results in this study showed the significant correlation of FVC (L and %) with MIP and MEP, which was similar to a previous report suggesting that the male gender, younger age, obesity, higher FVC (L) and shorter height were associated strongly and independently with higher values of MIP in relatively healthy adults. 18 Interestingly, results of weak FEV1 (L and %) correlations with MIP and MEP were not identified previously. In addition, the results of PEF (L/s and %) in all 217 participants or each sex showed low positive correlation with MIP and MEP. ...
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... It could therefore be postulated that those with inspiratory muscle weakness may suffer from more severe airflow obstruction and greater lung hyperinflation. This is in accord with previous research that found a positive correlation between MIP and airflow limitation in a COPD population [38,39]. ...
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Bronchiectasis is characterised by airflow obstruction and hyperinflation resulting in respiratory muscle weakness, and decreased exercise capacity. Inspiratory muscle training (IMT) is potentially an alternative treatment strategy to enhance respiratory muscle strength and endurance. Therefore, the aim was to investigate the effects of IMT on those with bronchiectasis. Eighteen participants (10 bronchiectasis) took part in an eight-week, three times a week IMT programme at 80% sustained maximal inspiratory pressure (SMIP). Lung function, respiratory muscle strength and endurance, exercise capacity, physical activity and self-determination theory measures were taken. Participants also took part in a semi-structured interview to assess their perceptions and experience of an IMT intervention. After eight weeks of IMT, bronchiectasis and healthy participants exhibited significant increases in MIP (27% vs. 32%, respectively), SMIP (16% vs. 17%, respectively) and inspiratory duration (36% vs. 30%, respectively). Healthy participants exhibited further improvements in peak expiratory flow and maximal oxygen consumption. Bronchiectasis participants reported high levels of perceived competence and motivation, reporting higher adherence and improved physical ability. Eight weeks of IMT increased inspiratory muscle strength and endurance in those with bronchiectasis. IMT also had a positive effect on perceived competency and autonomy, with bronchiectasis participants reporting improved physical ability and motivation, and high adherence.
... In agreement with our findings, multiple studies have reported significant positive correlations between MIP and airflow limitation as reflected by FEV 1 in subjects with COPD [17][18][19][20][21]. Furthermore, we observed that lower MIP values were related to reduced IC, IC/TLC and higher RV, which is also consistent with previous literature and makes physiological sense since pulmonary hyperinflation is known to alter respiratory mechanics, often leading to inspiratory muscle impairment [3,[22][23][24]. ...
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A prospective evaluation of the prevalence of CO2 retention and its relationship to lung mechanics and inspiratory muscle strength was carried out in 311 clinically stable patients with chronic obstructive pulmonary disease (COPD). Of these patients 32.8% had hypercapnia (PaCO2 greater than or equal to 43 mm Hg). PaCO2 was directly related to lung resistance (RL; r = 0.53) and inversely related to FEV1 (r = 0.53) and to an expression of the dead space/tidal volume ratio (1 - VD/VT) (r = 0.48). RL was found to be a major determinant of the mean intrathoracic pressure swing developed during inspiration (PI) at rest (r = 0.85). Maximal inspiratory pressure (PImax) was found to improve the predictive value for PaCO2 of several mechanical loads, with RL/PImax the best predictor (r = 0.57). The prevalence of hypercapnia increased from virtually 0 to 100% with increases in the RL/PImax value and was higher in the obese subjects at intermediate RL/PImax values, probably because of the burden placed on the respiratory muscles by chest wall mass loading. Our results show that chronic alveolar hypoventilation is likely to develop in COPD patients who have a combination of high inspiratory loads and inspiratory muscle weakness. hypercapnia may be one strategy available to avoid overloading of the inspiratory muscles leading to fatigue and possible irreversible failure.
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