Chest
Volume 107, Issue 3, March 1995, Pages 652-656
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Clinical Investigations: Techniques: Articles
Peak Inspiratory Mouth Pressure in Healthy Subjects and in Patients With COPD

https://doi.org/10.1378/chest.107.3.652Get rights and content

The validity of peak inspiratory mouth pressure (P. PImax) as a measure of inspiratory muscle strength was investigated by comparing it with sniff Pes in patients with COPD with respect to (1) learning effect, (2) reproducibility, and (3) measures of agreement. To assess the discriminating capacity of P. PImax, we compared the values in patients with COPD with those of healthy elderly subjects. Thirty-four patients (mean age, 62.5 years) with severe airways obstruction (FEV1, 44% predicted; FEV1/IVC, 37% predicted) and 149 healthy subjects (age ≥55 years) were included. P. PImax was assessed during a maximal static inspiratory maneuver, while sniff Pes was assessed during a maximal sniff maneuver. Both maneuvers were performed from residual volume ten times on the same day. P. PImax showed no learning effect, while the sniff maneuver used seven attempts to obtain a maximal value. The intraindividual coefficients of variation of P. PImax and sniff Pes were 11.2% and 6.0%, respectively. Measures of agreement showed no significant discrepancies between the mean P. PImax and mean sniff Pes (0.29 kPa, p=0.49). There was a significant correlation (r=0.57, p<0.001) between both measurements. P. PImax was significantly (p<0.001) lower in both male (8.2 kPa) and female (6.2 kPa) patients with COPD compared with healthy men (11.0 kPa) and healthy women (8.8 kPa). We conclude that P. PImax is a valid and noninvasive assessment of inspiratory muscle strength.

Section snippets

Patients With COPD

We studied 34 patients with known COPD, according to the American Thoracic Society criteria, 13 at the start of a pulmonary rehabilitation program. All patients were in a clinical stable condition with optimal drug management. Entry criteria were (1) FEV1 <60% predicted and (2) FEV1/IVC (inspiratory vital capacity) <50% both after bronchodilation with two inhalations of 40 µg of ipratropium bromide. The study was approved by the medical ethics committee of the University Hospital of Groningen

Results

All variables showed no deviation from a normal distribution.

Discussion

This study shows that P. PImax had no learning effect, an acceptable intraindividual variation, and an acceptable agreement with sniff Pes in patients with COPD. Furthermore, the P. PImax in healthy subjects is significantly higher than P. PImax in patients with COPD of comparable age and gender.

As for the learning effect, patients with COPD needed only two attempts to achieve their maximal P. PImax, while seven attempts are needed for the sniff maneuver. This indicates that patients learn the

ACKNOWLEDGMENTS

We thank the Department of Human Movement Sciences, University of Groningen. Data on the healthy subjects were collected in the study “Physical Fitness, Medical Consumption and Lifestyle of Citizens Over the Age of 55 in the Province of Drenthe, The Netherlands.” This study was supported by a grant of the Health Insurance Company “Het Groene Land.” We thank the lung function laboratory staff of Beatrixoord for their technical assistance in the performance of this study.

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    Supported by a grant of the Dutch Asthma Foundation (89.29) and the Foundation Astmabestrijding.

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