CPAP at 10 cm H2O during cardiopulmonary bypass does not improve postoperative gas exchange

To compare postoperative (PO) pulmonary gas exchange indexes in patients submitted to myocardial revascularization (MR) with or without the application of continuous positive airway pressure (CPAP) during cardiopulmonary bypass (CPB).

Thirty adult patients submitted to MR with CPB between March and September 2005 were randomly allocated to two groups: CPAP (n=15), patients that received CPAP at 10 cm H2O during CPB, and control (n=15), patients that didn't receive CPAP. PaO(2)/FiO2 and P(A-a)O2 were analyzed at four moments: Pre (just before CPB, with FiO2=1.0 ); Post (30 min post-CPB, with FiO2=1.0); immediate PO period (12h post-surgery, with FiO2=0.4 by using a Venturi(R) facial mask) and first PO day (24h post-surgery, with FiO2=0.5 by a facial mask).

PaO2/FiO2 and P(A-a)O2 tend to get significantly worst as time elapsed during the postoperative period in both groups, but no differences were observed between them at any moment. When PaO2/FiO2 was subdivided into three categories, a greater prevalence of patients with values between 200 mmHg and 300 mmHg were observed in CPAP group only at moment Post (30 min post-CPB; p = 0.02).

CPAP at 10 cm H2O administered during CPB, although had lightly improved PaO2/FiO2 at 30 minutes post-CPB, had no significant sustained effect on postoperative pulmonary gas exchange. We concluded that in patients submitted to MR, application of 10 cmH2O CPAP does not improve postoperative pulmonary gas exchange.