Effects of endotracheal intubation on airway neuropeptide content, arterial oxygenation and lung volumes in anaesthetized rats.

Background General anaesthesia affects lung volume and pulmonary gas exchange. What role is played by mechanical stimulation by the endotracheal tube? Methods We investigated the effects of intubation on arterial oxygenation and lung volume in rats. Results Endotracheal intubation caused an increase in PA–a O2 and volume of trapped gas in the lung. This was accompanied by a reduction in neuropeptides and calcitonin gene-related peptide (CGRP) in trachea, bronchi and lung, and in vasoactive intestinal peptide (VIP) in the trachea. The increase in PA–a O2 and volume of trapped gas due to intubation was not altered in the animals given capsaicin, in which neuropeptide levels were reduced. Conclusions These data suggest that the decrease in CGRP and VIP content in the airway tissues may be one of the consequences, but not the cause, of impaired gas exchange by endotracheal intubation. The increase in volume of trapped gas in the lung is apparently not mediated by activation of capsaicin-sensitive sensory nerves.