External high-frequency oscillation for hypercapnia after upper abdominal surgery.

The purpose of this study was to evaluate the efficacy of external high-frequency oscillation (EHFO) in patients with hypercapnia following upper abdominal surgery. Seven patients were ventilated with EHFO for 2 hr at 60 oscillations/min, with cuirass pressures of 36 cm H2O (-26 to +10), and an inspiratory to expiratory ratio of 1:1. Blood gases and cardiac functional parameters were examined during the 2 hr on EHFO. Pulmonary functional parameters were analyzed prior to the institution and after the termination of EHFO. PaCO2 significantly decreased from 61 +/- 8 mmHg to 48 +/- 7 mmHg after 10 min on EHFO (p < 0.01). PaO2 significantly increased from 74 +/- 10 mmHg 95 +/- 26 mmHg after 1 hr on EHFO (p < 0.01). The heart rate decreased significantly from 108 +/- 27 beats/min to 101 +/- 24 beats/min after 30 min on EHFO (p < 0.05). The FEV1 and FVC significantly increased from 1.09 +/- 0.54 L to 1.50 +/- 0.46 L (p < 0.01) and from 1.90 +/- 0.74 L to 2.18 +/- 0.60 L (p < 0.05), respectively. The other parameters of lung function also significantly improved after the termination of EHFO. The significant changes in all of the pulmonary functional parameters continued for 1 hr after the termination of EHFO. EHFO is an effective method of gas exchange which is associated with earlier return to preoperative lung function.