Combination of external chest wall oscillation with continuous positive airway pressure

We studied the effects of continuous positive airway pressure (CPAP) on pul monary gas exchange during external chest wall oscillation (ECWO), and the relationship with obesity, in nine patients with normal body weight (group 'N') and 10 obese patients (group 'O'). During ECWO with CPAP 5, Pa-CO 2 de creased in group 'O' (6.0 (SD 0.8) to 5.6 (0.5) kPa, P<0.05), whereas it in creased in group 'N' at all levels (P<0.01). Arterial PO2 (P<0.001) was gre ater and Pa-CO 2 (P<0.01) less in group 'N' during CPPV and ECWO plus CPAP We also compared the haemodynamic effects of ECWO plus CPAP with those of c ontinuous positive pressure ventilation (CPPV). ECWO plus CPAP and CPPV wer e applied for 30 min to 6 ASA III patients. Cardiac output (CI 2.7 (0.5) vs 2.1 (0.2) litre min(-1) m(-2), P<0.05) and stroke volume (SVI 49 (9) vs 32 (6) ml m(-2), P<0.05) were greater during ECWO plus CPAP than with CPPV. E CWO is less effective in obese individuals than in those with normal body w eight, and the effect of CPAP in overweight individuals is small.