Effect of baseline lung compliance on the subsequent response to positive end-expiratory pressure in ventilated piglets with normal lungs.
OBJECTIVE
To determine the pulmonary function and hemodynamic effects of incremental positive end-expiratory pressure in two groups of normal ventilated newborn piglets with different baseline dynamic lung compliance.


METHODS
Prospective, controlled, intervention study.


METHODS
Animal laboratory.


METHODS
One group of piglets (inflation group) was prepared with 3 cm H2O (0.29 kPa) positive end-expiratory pressure and a maximal lung inflation to increase baseline lung compliance as compared with the other group (no-inflation group), prepared by 3 hrs of ventilation at zero end-expiratory pressure. Both groups were then subjected to a sequence of incremental positive end-expiratory pressures from 0 to 12 cm H2O (0 to 1.18 kPa) in 2-cm increments for 15-min periods at each level followed by a 60-min recovery period at zero end-expiratory pressure.


RESULTS
Pulmonary function, hemodynamic and blood gas data were collected at each positive end-expiratory pressure value and at 15-min intervals during recovery. Baseline dynamic lung compliance was 5.2 +/- 0.3 mL/cm H2O (53.04 +/- 3.06 mL/kPa) in the inflation group and 2.5 +/- 0.1 mL/cm H2O (25.5 +/- 1.02 mL/kPa) in the no-inflation group. No differences were found in any other pulmonary function, hemodynamic or blood gas value at baseline. Incremental positive end-expiratory pressure resulted in a decrease in dynamic lung compliance and an increase in end-expiratory lung volume in both groups of piglets; dynamic lung compliance was greater in the inflation group at all times. No differences were found in end-expiratory lung volume between groups. Hemodynamic changes in both groups of piglets included: decreased cardiac output and increased pulmonary vascular resistance and systemic vascular resistance. The changes in cardiac output (-23% vs. -32%), pulmonary vascular resistance (+53% vs. +95%), and systemic vascular resistance (17% vs. 51%) were less in the inflation group as compared with the no-inflation group.


CONCLUSIONS
Baseline dynamic lung compliance is an important determinant of the subsequent effect of positive end-expiratory pressure on pulmonary function and hemodynamics in the ventilated piglet with normal lungs.
Mundie
T G
TG
Department of Clinical Investigation, Tripler Army Medical Center, Honolulu, HI.
Easa
D
D
Finn
K C
KC
Stevens
E L
EL
Hashiro
G
G
Balaraman
V
V
D000818:Animals; D000831:Animals, Newborn; D005260:Female; D006439:Hemodynamics; D008170:Lung Compliance; D008176:Lung Volume Measurements; D008297:Male; D011175:Positive-Pressure Respiration; D011446:Prospective Studies; D013552:Swine