Frequency and percent inspiratory time for high-frequency jet ventilation.
A variety of frequencies and percent inspiratory times (%TI) may be used for high-frequency jet ventilation (HFJV). Five physiologic criteria were used to evaluate various combinations of frequency and %TI: mean airway pressure (Paw), cardiac output, PaCO2, PaO2, and intrapulmonary shunt (Qsp/Qt). At a constant drive pressure, the effects of frequencies of 100, 200, 300, 450, 600, 750, and 900 cycle/min at %TI values of 20%, 30%, and 40% of the respiratory cycle were evaluated and compared with the effects of controlled mechanical ventilation (CMV) at 8 to 12 breath/min. Only at 200 cycle/min and 20% TI, were Paw, cardiac output, PaCO2, PaO2, and Qsp/Qt all the same as the CMV values. At 100 cycle/min and 20% TI, CO2 elimination increased without significantly affecting Paw, cardiac output, PaO2, or Qsp/Qt. These data suggest that HFJV might compromise one or more physiologic variables at certain combinations of frequency and %TI. Therefore, at a fixed drive pressure, there appears to be a narrow range of HFJV ventilator settings that should be considered.
D000818:Animals; D002302:Cardiac Output; D004285:Dogs; D011175:Positive-Pressure Respiration; D011659:Pulmonary Gas Exchange; D012121:Respiration, Artificial