Effect of extradural anaesthesia on the ventilatory response to hypoxaemia

The effect of lumbar or thoracic extradural anaesthesia on the ventilatory response to progressive isocapnic hypoxaemia was studied in two groups of 10 unpremedicated patients. The ventilatory measurements were taken twice, before and 20 min after the administration of 10 ml of lignocaine 2%. Lumbar extradural anaesthesia did not change the slope of the hypoxic response curve, but it significantly increased minute ventilation by 27% at an arterial oxygen saturation of 90%. Thoracic extradural anaesthesia was not associated with any changes in either index. We conclude that neither lumbar nor thoracic extradural anaesthesia impairs the ventilatory response to progressive isocapnic hypoxaemia.