Static pressure-volume curves and effect of positive end-expiratory pressure on gas exchange in adult respiratory distress syndrome.
Fifteen patients with adult respiratory distress syndrome (ARDS) were studied: 11 in the early stage of ARDS (group 1); 4 in the late stage (group 2). The inspiratory and expiratory static pressure-volume (P-V) curves of the respiratory system were compared to the pulmonary shunt (Qsp/Qt) when PEEP was increased; cardiac output was kept constant. In group 1 patients, we found that a concavity on the P-V curves was associated with an abrupt decrease in Qsp/Qt when PEEP was increased; the concavity on the expiratory curve was correlated with the change in Qsp/Qt but not the concavity on the inspiratory curve. In group 2 patients, the P-V curves were found rectilinear and Qsp/Qt was not abruptly decreased when PEEP was increased. Expiratory P-V curve can be used to determine: first, whether a patient should be ventilated with PEEP; second, the PEEP level which can be set on the respirator. In group 1 patients, when PEEP was set to a value corresponding to the inflexion point, i.e., the point of departure from the exponential shape (mean value 14.6 +/- 2.8 cm H2O), Qsp/Qt compared to zero PEEP was abruptly decreased to 87.6 +/- 6%; further increase in PEEP had little advantage.
D000293:Adolescent; D000328:Adult; D000368:Aged; D002245:Carbon Dioxide / Q000097:blood; D002648:Child; D005260:Female; D005652:Functional Residual Capacity; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007385:Intermittent Positive-Pressure Ventilation; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D011175:Positive-Pressure Respiration; D011312:Pressure; D011654:Pulmonary Edema / Q000503:physiopathology; D011658:Pulmonary Fibrosis / Q000503:physiopathology; D011659:Pulmonary Gas Exchange; D012128:Respiratory Distress Syndrome / Q000503:physiopathology* / Q000628:therapy
D002245:Carbon Dioxide; D010100:Oxygen