Role of the Carotid Bodies in Breath-Holding

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Abstract
To determine the role of the carotid bodies in the sensation of breathlessness during breath-holding, studies were performed in six normal subjects and in five patients with asymptomatic asthma who had had both carotid bodies resected. Breath-holding followed single inspirations of 100, 50, 21 and 12 per cent oxygen and after breathing of 12 per cent oxygen for one minute. In the normal subjects, breath-holding time and alveolar carbon dioxide tension at the breaking point progressively decreased as alveolar oxygen tension decreased. In contrast, there was no change in alveolar carbon dioxide tension or breath-holding time until alveolar oxygen tension was reduced below 50 mm Hg in this patient group. Breath-holding time was twice that for the normal subjects at 50 mm Hg. These studies indicate that the carotid bodies are active chemoreceptors for oxygen through levels greater than 200 mm Hg, that interaction of carbon dioxide and oxygen on respiratory control occurs at the level of the carotid bodies in man, and that the carotid bodies contribute to the sensation of breathlessness that results in the break from breath-holding. (N Engl J Med 290:819–822, 1974)