Peripheral chemoreceptors (carotid bodies) are the main sensing organs for hypoxaemia. During carotid surgery, the carotic body in the bifurcation of the common carotid artery is often involved and damaged or destroyed. Animals lose their ability to adapt to high altitude after experimental denervation of the carotid bodies. The objective of our study was to responds to hypoxaemia and not to anaemia or reduced flow. It is, therefore, the main organ for transduction of hypoxic signals in altitude and inducing hypoxic ventilatory response. In animal experiments, after removal or denervation of both carotid bodies, acute hypoxia actually causes depression of ventilation3. Up to now, no data have been reported on the altitude adaptation of patients after carotid surgery with possible involvement and damage of the carotic body.The objective of our study was to evaluate the acute ventilatory adaptation in moderate altitude of patients after carotid surgery. Patients and methodsThis study was performed in the Austrian Alps at moderate altitude. Five patients participated after informed consent. Four male and one female patient, mean(s.d.) age 70(3.21) years at the time of operation, had elective carotid surgery because of severe symptomatic stenosis of the internal carotid. All five patients had a history of hypertension; no patient suffered from COPD or asthma; and all patients were ex-smokers for more than 2 years. No patient took part in a special training programme, all five estimated their physical fitness to be average, all were in a good state of health after the operation and able to go for walks on foot, and all were lowland dwellers. Before (interval 2 weeks -2 months) and after (interval 6 months-15 months) carotid surgery, capillary blood was obtained from the arterialized ear lobe of each patient4 at 171 m altitude. After passive transport by car to 1600 m and 45 min rest, the same procedure was repeated. Blood samples were stored in an ice water cooling box and analysed on a BGE Blood Gas Analyser (Instrumentation Laboratory, Milano, Italy) within 2 h. Samples were taken between 0900 and 1100 at similar conditions, ambient temperature was constant at 21°C at 171 m (air conditioned university clinic) and 18°C at 1600 m (mountain restaurant). Breathing frequency and blood pressure were also recorded at each sampling.

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