Helium/Oxygen Breathing Improved Hypoxemia After Cardiac Surgery

Abstract

14 breaths/min under volume-controlled ventilation without muscle relaxants, which was sufficient to maintain normocapnea) and Pao, did not improve. After admission to the intensive care unit (ICU), her arterial blood oxygenation failed to improve despite vigorous therapy, including nebulization of a bronchodilator, an 1:E ratio of 0.75, and PEEP of up to 10 cm H,O. Use of high PEEP (15-20 cm H,O) was avoided in order to prevent hemodynamic deterioration. (Her cardiac index [CI] and central venous pressure were 2.0-2.3 L * min-’ * m-’ and 9-13 mm Hg, respectively, with support by intravenous dopamine and dobutamine at a rate of 5 Fg * kg-’ . min-’ each.) Bronchial secretion was not pathologic, and her chest radiograph showed no significant change (Fig. 1). On the second postoperative day, when Pao, had decreased to 56 mm Hg with a FIO, of 1.0 and the intrapulmonary shunt fraction (Qs/Qt) was calculated to be 35%, He/O, was initiated. Helium (purity, 99.9%) was connected to the compressed-air port of a Servo-ventilator 900-C. The required FIO, decreased and the fraction of helium thus increased: Pao, was 50 mm Hg with a FIO, of 40.5 and Qs/Qt of 31% some 15 min after the initiation of He/O, (Fig. 2). Pace, was slightly decreased (42 + 37 mm Hg). Peak inspiratory pressure (PIP, 24 + 24 cm H,O), CI (2.4 + 2.5 L * min-’ * m-‘), and a systolic systemic blood pressure (127 + 129 mm Hg) showed no change. After 2 h of inhaling He/O,, oxygenation remained good and reached the normal range after 12 h.