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Animal and tissue studies have indicated that the carotid bodies are sensitive to glucose concentrations within the physiological range. This glucose sensitivity may modulate the ventilatory response to hypoxia, with hyperglycaemia suppressing the hypoxic response and hypoglycaemia stimulating it. This study was designed to determine whether hypo-and hyperglycaemia modulate the hypoxic ventilatory response in humans. In 11 normal research participants, glucose levels were clamped at 2.8 and 11.2 mmol l −1 for 30 min. At the start and end of each clamp, blood was drawn for hormone measurement and the isocapnic hypoxic ventilatory response was measured. Because generation of reactive oxygen species may be a common pathway for the interaction between glucose and oxygen levels, the experiments were repeated with and without pretreatment for 1 week with vitamins C and E. Hypoglycaemia caused an increase in the counter-regulatory hormones, a 54% increase in isocapnic ventilation, and a 108% increase in the hypoxic ventilatory response. By contrast, hyperglycaemia resulted in small but significant increases in both ventilation and the hypoxic ventilatory response. Antioxidant vitamin pretreatment altered neither response. In conclusion, the stimulant effect of hypoglycaemia on the hypoxic ventilatory response is consistent with a direct effect on the carotid body, but an indirect effect through the activation of the counter-regulatory response cannot be excluded. The mechanisms behind the mild stimulating effect of hyperglycaemia remain to be elucidated.

At the mild to moderate level of sedation studied, midazolam and propofol sedation resulted in the same propensity for UAO. In this homogeneous group of healthy subjects, there was a considerable range of negative pressures required to cause UAO. The specific factors responsible for the maintenance of the upper airway during sedation remain to be elucidated.

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SummaryAirway management is primarily designed to avoid hypoxia, yet hypoxia remains the main ultimate cause of anaesthetic‐related death and morbidity. Understanding some of the physiology of hypoxia is therefore essential as part of a ‘holistic’ approach to airway management. Furthermore, it is strategically important that national specialist societies dedicated to airway management do not only focus upon the technical aspects of airway management, but also embrace some of the relevant scientific questions. There has been a great deal of research into causation of hypoxia and the body’s natural protective mechanisms and responses to it. This enables us to think of ways in which we might manipulate the cellular and molecular responses to confer greater protection against hypoxia‐induced tissue injury. This article reviews some of those aspects.