Comparing methods of administering high-frequency jet ventilation in a model of laryngotracheal stenosis.

Abstract

We administered high-frequency jet ventilation (HFJV) to a tracheal-lung model with connectors of internal diameter 2.5-8.5 mm to simulate ventilation through varying degrees of laryngotracheal stenosis. With reductions in diameter, end-expiratory pressure (EEP) and peak inspiratory pressure (PIP) increased. During supraglottic, translaryngeal, and transtracheal HFJV, respectively, EEP was > or =10 mm Hg at diameters narrower than 5.5, 4.0, and 3.5 cm, and PIP was >20 mm Hg at diameters narrower than 5.5, 3.5, and 3.0 cm. EEP and PIP were greater during supraglottic HFJV than during translaryngeal and transtracheal HFJV (P < 0.01). At diameters of <3.5 and 4.0 cm, respectively, PIP and EEP increased and were significantly greater (P < 0.01) during translaryngeal HFJV than during transtracheal HFJV. In a second experiment, the degree of ventilation and air entrainment was assessed by administering nitrous oxide 4 L/min to the model. Nitrous oxide concentrations were significantly (P < 0.01) smaller and nitrogen concentrations were significantly (P < 0.01) larger during supraglottic HFJV than either translaryngeal or transtracheal HFJV. The larger EEP and PIP associated with supraglottic HFJV may be attributable to increased ventilation and air entrainment compared with translaryngeal and transtracheal HFJV. Ventilatory driving pressure during supraglottic high-frequency jet ventilation may be reduced to minimize high airway pressures and hence the potential for pulmonary barotrauma in patients with laryngotracheal stenosis.