Quantification of the jet function of a jet stylet.

The concept and use of a jet stylet as an additional safety measure during tracheal extubation of patients in whom subsequent ventilation and/or reintubation of the trachea may be difficult has recently been described. If jet ventilation through a jet stylet could provide for effective gas exchange, it would allow additional time to assess the need for reintubation of the trachea. We determined the tidal volumes (measured by integrating a pneumotachograph flow signal) that 50-psi jet ventilation, at an inspiratory to expiratory time ratio of 1:1 (unit of time = 1 s), could deliver through small, medium, and large Sheridan tube exchangers into an in vitro lung model that had lung compliances of 50 and 30 mL/cm H2O (six experimental permutations). The tidal volume (VT) produced during jet ventilation was moderately dependent on air entrainment (measured by a volume spirometer), with the contribution to total VT ranging from 0% to 31%; the amount of air entrainment was confirmed by excellent correlation between the alveolar oxygen concentration (FAO2) measured by an oxygen analyzer and the FAO2 calculated from entrained and total VT. Decreased lung compliance caused decreased VT and end-expiratory volume for all six experimental conditions. The largest VT and minute ventilation (VE) generated were 1680 mL and 51.6 L/min (large tube exchanger, high lung compliance) and the lowest VT and VE were 440 mL and 13.2 L/min (small tube exchanger, low lung compliance), respectively. These findings validate the term "jet stylet" for all three tube exchangers as even the smallest tube exchanger, coupled with a low lung compliance, can provide a VE consistent with total ventilatory support for most clinical situations.