Journal of Applied Physiology, Vol 64, Issue 3 1217-1222, Copyright © 1988 by American Physiological Society
Effect of mechanical load on tidal volume during high-frequency jet ventilation
G. G. Berdine and P. J. Strollo
Department of Medicine, University of Texas Health Sciences Center, San Antonio.
High-frequency jet ventilation (HFJV) was studied in twelve deeply
anesthetized, paralyzed dogs. Entrained volume and total expired volume
were directly measured by integration of flow. Jet volume was computed from
these measurements. Seven dogs were ventilated with a driving pressure of
10 psi at rates of 2 and 5 Hz for each of three mechanical loads: control,
thoracoabdominal wrap, and histamine infusion. Both load conditions reduced
total expired volume and entrained volume but had no effect on jet volume.
Wrap reduced entrainment more at 2 Hz while the effect of histamine
infusion was frequency independent. Control arterial blood gases
demonstrated that PO2 was higher and PCO2 was lower during 2 Hz ventilation
than during 5 Hz ventilation despite equivalent minute volumes. Five
additional dogs were studied using control and wrap loads and an additional
ventilator setting of 15 psi at 5 Hz. This group demonstrated that wrap
reduces entrainment more at lower frequencies for ventilatory settings
providing equivalent gas exchange. We conclude that increasing mechanical
load reduces entrainment during HFJV and that this reduction is frequency
dependent for restrictive loads.
