Helium/Oxygen Breathing Improves Hypoxemia after Cardiac Surgery

The effects of helium/oxygen (He/O2) on oxygenation (respiratory index [PaO2/FiO2] and intrapulmonary shunt [Qs/Qt]) and on lung parameters (dynamic compliance [Cdyn] and peak inspiratory pressure [PIP]) were studied in 12 patients. After cardiac surgery, they had impairment of oxygenation without physiological findings and with normal chest radiographs despite having a positive end expiratory pressure of up to 10 cm H2O. After 90 min of inhalation of He/O2, oxygenation had improved significantly; that is, PaO2/FidO2 increased significantly (from 113 to 174 mm Hg; mean values are given; p < 0.01), and there was a significant fall in Qs/Qt (from 29 to 19%; p < 0.001) together with an increase in Cdyn (from 60 ml/cm H2O to 64 ml/cm H2O; p < 0.05). These results suggest that He/O2 may have improved oxygenation by recruiting previously obstructed small airways and alveoli.