Chest
Volume 96, Issue 2, August 1989, Pages 267-271
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Determinants of Maximum Exercise Capacity in Patients with Chronic Airflow Obstruction

https://doi.org/10.1378/chest.96.2.267Get rights and content

Patients with chronic airflow obstruction (CAO) often develop impairment of respiratory muscle function. We hypothesized that inspiratory muscle strength, as assessed by resting, peak inspiratory pressure (PIP) may be an important determinant of maximum exercise capacity in patients with CAO. Twenty ambulatory male patients (mean age, 56 ± 3 years [± SE]) with CAO (FEV1, 1.72 ± 0.21 L) comprised the studied population. Oxygen consumption at incremental cycle ergometry to tolerance ( V˙o2max, 1.80 ± 0.20 L/min) served as the dependent variable for regression vs measures of resting pulmonary function. Significant correlations with V˙o2max included power output in watts (r=0.951), V˙Emax (r = 0.858), Dsb (r = 0.841), PIP (r = 0.816), age (r = – 0.809), FEV1 (r = 0.763), and FVC (r = 0.663). The FEV1, Dsb, and PIP each entered into a multiple linear regression relationship describing V˙o2max. Also, when paired with V˙Emax as independent variables in multiple regression, PIP and Dsb each improved description of V˙o2max over V˙Emax alone (p<0.05), whereas FEV1 and FVC did not (p>0.05). We conclude that factors other than ventilatory capacity also have a quantitative effect on V˙o2max and that PIP constitutes a determinant of maximum exercise capacity in patients with CAO. (Chest 1989; 96:267–71)

Section snippets

MATERIALS AND METHODS

For the purposes of this study, we defined CAO as clinically stable primary pulmonary disease with the following characteristics: (1) ratio of FEV1/FVC less than 0.70; (2) TLC greater than 80 percent of predicted; and (3) change in FEV1 after bronchodilator inhalation less than 15 percent.

In addition, we defined VLE as (1) fcmax less than 2 SD below predicted maximum; (2) primary symptom at maximal exercise consisting of dyspnea without other limiting symptom; and (3) exercise ventilation

RESULTS

The studied population (Table 1) consisted of 20 men with CAO ranging from mild to severe by expiratory spirometric data. They had a mean age of 56 ± 3 years (mean ± SE) and a mean ratio of FEV1/FVC of 0.50 ± 0.03. Racially, there were 18 white subjects and two black subjects.

The PIP and PEP for the sample equalled 70 ± 6 and 66 ± 6 percent of predicted from Black and Hyatt,16 respectively. The PIP and PEP fell below the lower limit of normal in 11 and eight patients, respectively.

All subjects

DISCUSSION

We developed a multiple linear regression model (equation 2) which describes V˙o2max in patients with CAO in terms of the resting pulmonary function parameters, FEV1, Dsb, and PIP. The use of PIP in multivariate prediction of V˙o2max has not previously been reported. In addition, we presented V˙o2max as a function of power output in watts (equation 1) for patients with CAO.

Equation 2 relates exercise capacity to the function of anatomic compartments of the respiratory system,

ACKNOWLEDGMENTS

We thank Mr. William A. Slivka, Mr. Thomas R. McCumber, and Mr. James A. Godville for technical assistance on this project.

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  • Cited by (0)

    Presented in part at the 51st Annual Scientific Assembly, American College of Chest Physicians, New Orleans, Oct 30, 1985.

    Supported by WRAMC Department of Clinical Investigation research protocol 1717.

    The opinions contained herein represent solely the views of the authors and are not to be construed as representing the views of the Department of Defense or the Department of the Army.

    Manuscript received September 12; revision accepted December 9.

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