Changes in airway resistance induced by nasal or oral intermittent positive pressure ventilation in normal individuals

Nasal intermittent positive-pressure ventilation (nIPPV) is used for the tr eatment of respiratory failure in patients with neuromuscular disease, The aim of the present study was to demonstrate that nIPPV may activate nose re ceptors, the consequence of which being reflex changes in lung resistance, The changes in interrupter resistances (Rint) in response to nIPPV were tes ted before and after local anaesthesia of the nasal mucosa in normal subjec ts. They were compared to the Rint changes induced by oral intermittent pos itive-pressure ventilation (oIPPV) in the same individuals. Rint was measur ed during IO-min periods of nIPPV or oTPPV at a constant rate (15 L.min(-1) ), but at two different stroke volumes (0.8 and 1.2 L). Inspired temperatur e and relative humidity were held constant, nIPPV with 1.2 L (17 mL.kg(-1)) significantly increased the Rint value (+22 %), This effect disappeared after nose anaesthesia or after inhalation of a cholinergic antagonist. oIPPV never changed Rint, even though the associat ed hypocapnia was present and more accentuated than during nIPPV. Adding CO 2 to the inspired gas during nIPPV and oIPPV trials suppressed the Rint cha nges. The present study suggests the existence of a nasopulmonary bronchoconstric tor reflex elicited through the stimulation of nasal mechanoreceptors, thei r activity being markedly influenced by the changes in expired CO2 concentr ation.