Tracheobronchial dilating effect of high frequency jet ventilation

Effect of high frequency jet ventilation (HJFV) on tracheobronchial tone was examined in anesthetized dogs. Changes in intraluminal pressure of water-filled endotracheal cuff (Pcuff) were used as an indicator of tracheal smooth muscle tone. Animals were initially ventilated with conventional mechanical ventilation (CMV) to maintain normal Pa(CO)(2). HFJV (2.0 Hz.) was then applied to each animal in such a way to maintain the same mean airway pressure and Pa(CO)(2) as in CMV. Immediately after changing CMV to HFJV, Pcuff decreased significantly and remained decreased during the period of HFJV. After changing HFJV to CMV, Pcuff gradually returned to its previous level. Histamine-induced tracheobronchial constriction was partially released by HFJV as shown by a decrease in Pcuff and airway resistance (Raw) and by an increase in static lung-thorax compliance (Cst) measured immediately after the cessation of HFJV. These results suggest that HFJV has a tracheobronchial dilating action, presumably mediated by pulmonary stretch reflex, and this may be one of the mechanisms of an increase in mucous secretion and of other reported favorable effects of HFJV in some types of respiratory failure.