Does the supine position worsen respiratory function in elderly subjects?

The aim of our study was to test whether the supine position or the sitting position worsens static, forced expiratory flows and measurements of lung mechanics in a group of aged subjects living in a nursing home who were clinically stable and without clinical evidence of cardiorespiratory diseases. Seventeen subjects (mean age 80 +/- 7 years; 16 f) were studied under baseline conditions. Spirometric, breathing pattern and mechanics data by means of an esophageal balloon were measured in sitting and supine positions. Analysis of sitting results showed aged subjects to have a slight flow limitation in peripheral airways, an increase in expiratory airways resistance and mild hyperinflation index (PEEPi = 2.2 +/- 1.9 cm H2O). Pressure time index did not reach the fatigue level in hardly any patient. Maximal inspiratory pressure values (42 +/- 15 cm H2O) were reduced by about 50\% in comparison with our normal laboratory standards. Arterial blood gas analysis revealed no pathological data in any subject. When supine, subjects revealed a significant decrease in forced expiratory volume at the first second (p < 0.005), in forced vital capacity (p < 0.01) and in peak expiratory flow (p < 0.05). Moreover, mechanics and breathing pattern data showed a significant decrease in tidal volume (Vt) and dynamic lung compliance (Cld) (p < 0.05) and an increase in respiratory rate/Vt ratio (p < 0.05). Our data confirm the results of previous reports about Cld decrease in supine posture in young normal people. Although our aged subjects showed a significant decrease in forced expiratory volumes and Vt when the supine position was adopted, static mechanics data did not appear modified by the gravitational effect of this posture.