HELIUM OXYGEN BREATHING IMPROVED HYPOXEMIA AFTER CARDIAC-SURGERY - CASE-REPORTS

Helium possesses a low specific gravity, has a coefficient of diffusio n twice that of nitrogen and is half as soluble (1). The use of a heli um-oxygen mixture (He/O-2) has been reported to result in the temporar y relief of major airway obstruction or chronic obstructive lung disea se, including asthma (2,3), by reducing turbulent flow with a concomit ant reduction in flow resistance. Patients undergoing open heart surge ry can develop increases in extravascular lung water and microatelecta sis, resulting in a compromised pulmonary mechanism and gas exchange. These effects are usually reversible by increasing the level of positi ve end-expiratory pressure (PEEP) to 15-20 cm H2O (high PEEP). However , high PEEP has undesirable cardiovascular effects in patients with se verely deteriorated circulation. We hypothesized that the substitution of helium for nitrogen would effectively resolve the abnormalities in pulmonary gas exchange. After institutional approval and informed con sent, three hypoxemic post-cardiac surgical patients were ventilated w ith He/O-2 after failing to improve sufficiently with the usual therap eutic techniques.