MEDEX 2015: Positive expiratory pressure improves oxygenation and symptoms at high altitude

Breathing with a positive expiratory pressure (PEP) has been shown to increase arterial oxygenation during acute hypoxic exposure but the underlying mechanisms and consequences on symptoms at high altitude remain to be elucidated. Twenty four males (41(6) yrs) were investigated at sea level and at 5100 m. Participants laid down for 90 min, while breathing through a face mask with PEP=0 cmH2O (PEP0, 0-45 min) and with PEP=10 cmH2O (PEP10, 46-90 min). During PEP0 and PEP10, arterial (SpO2), quadriceps and prefrontal (near infrared spectroscopy) oxygenation, middle cerebral artery blood velocity (MCAv), cardiac function, extravascular lung water accumulation (UsLC, thoracic ultrasound lung comets) and symptoms of acute mountain sickness (Lake Louise score) were assessed. At 5100 m with PEP0, SpO2 was 78(4)%, UsLC was 8(5) and the Lake Louise score was 2.3(1.7) pts (all p<0.05 vs sea level). At high altitude, PEP10 increased SpO2 (+9(5)%), quadriceps (+2(2)%) and prefrontal cortex (+1(2)%) oxygenation (all p<0.05), but decreased mean MCAv (-16(14) cm.s-1, p<0.001) and reduced cardiac output (-0.7(1.2) L.min-1, p=0.01) due to a decreased stroke volume (-9(15) mL). The number of UsLC was slightly decreased (-1(3), p=0.08) while Lake Louise score decreased significantly (-0.5(1.3) pts, p=0.04), with the incidence of acute mountain sickness being 42% with PEP0 (10/24) and 25% with PEP10 (6/24). PEP breathing improved arterial and tissue oxygenation and decreased symptoms of ...
Source: European Respiratory Journal - Category: Respiratory Medicine Authors: Tags: Clinical Respiratory Physiology, Exercise and Functional Imaging Source Type: research