EFFECTS OF BODY POSITION, HYPERINFLATION, AND BLOOD-GAS TENSIONS ON MAXIMAL RESPIRATORY PRESSURES IN PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

Background Inspiratory muscle strength in patients with chronic obstru ctive pulmonary disease (COPD) can be affected by mechanical factors w hich influence the length of the diaphragm, and by non-mechanical fact ors. The aim of the present study was to evaluate firstly the effects of body position on respiratory pressures and, secondly, to determine the relative contribution of age, body mass index (BMI), lung volumes, and arterial blood gas tensions to respiratory muscle strength. Metho ds - Thirty male patients with stable COPD (mean FEV(1) 40.4% predicte d) participated in the study. Maximal inspiratory and expiratory mouth pressures (PImax, PEmax) and maximal inspiratory transdiaphragmatic p ressures (PDI) in the sitting and supine position, lung function, and arterial blood gas tensions were measured. Results - Mean (SD) PImax i n the sitting position was higher than in the supine position (7.1 (2. 3)kPa v 6.4 (2.2) kPa respectively). In contrast, PDI in the sitting p osition was lower than in the supine position (10.0(3.5)kPa v 10.8(3.7 )kPa respectively). PEmax was higher in the sitting position (9.3 (3.0 ) kPa) than in the supine position (8.7 (2.8) kPa). Significant correl ations were found between inspiratory muscle strength on the one hand, and lung function parameters, BMI, and arterial blood gas tensions on the other. Conclusions Inspiratory muscle strength in patients with C OPD is influenced by mechanical factors (body position, lung volumes) and non-mechanical factors (BMI, FEV(1), gases). PImax PEmax are blood lower in the supine position while, in contrast to healthy subjects, PDI is higher in the supine position than in the sitting position.