Helium-oxygen reduces the production of carbon dioxide during weaning from mechanical ventilation

BACKGROUND Prolonged weaning from mechanical ventilation has a major impact on ICU bed occupancy and patient outcome, and has significant cost implications.There is evidence in patients around the period of extubation that helium-oxygen leads to a reduction in the work of breathing. Therefore breathing helium-oxygen during weaning may be a useful adjunct to facilitate weaning. We hypothesised that breathing helium-oxygen would reduce carbon dioxide production during the weaning phase of mechanical ventilation. MATERIALS/PATIENTS AND METHODS We performed a prospective randomised controlled single blinded cross-over trial on 19 adult intensive care patients without significant airways disease who fulfilled criteria for weaning with CPAP. Patients were randomised to helium-oxygen and air-oxygen delivered during a 2 hour period of CPAP ventilation. Carbon dioxide production (VCO2) was measured using a near patient main stream infrared carbon dioxide sensor and fixed orifice pneumotachograph. RESULTS Compared to air-oxygen, helium-oxygen significantly decreased VCO2 production at the end of the 2 hour period of CPAP ventilation; there was a mean difference in CO2 production of 48.9 ml/min (95% CI 18.7-79.2 p = 0.003) between the groups. There were no significant differences in other respiratory and haemodynamic parameters. CONCLUSION This study shows that breathing a helium-oxygen mixture during weaning reduces carbon dioxide production. This physiological study supports the need for a clinical trial of helium-oxygen mixture during the weaning phase of mechanical ventilation with duration of weaning as the primary outcome. TRIAL REGISTRATION ISRCTN56470948.