Ca. Velarde et al., A comparison of intratracheal pulmonary ventilation to conventional ventilation in a surfactant deficient animal model, CRIT CARE M, 28(5), 2000, pp. 1455-1458
Objective: To compare intratracheal pulmonary ventilation (ITPV) with conve
ntional ventilation in a rabbit model of surfactant deficiency.
Design: A prospective randomized animal study.
Setting: The Children's National Medical Center Research Animal Facility in
Washington, DC.
Subjects: Adult male New Zealand white rabbits (n = 20), weighing 1.4-4.2 k
g.
Interventions: After anesthesia and catheter placement, rabbits were trache
otomized, paralyzed, and placed on the conventional ventilator. We determin
ed pulmonary functions at baseline. We washed surfactant out of the lungs b
y using serial bronchoalveolar lavages. Pulmonary function studies were det
ermined after completion of the bronchoalveolar lavages and were used as an
indication of severity of lung injury. Animals were randomized into two gr
oups: We placed ten animals on ITPV, using the ITPV reverse thruster cathet
er designed by Kolobow and a prototype ITPV ventilator designed at Children
's National Medical Center; we placed ten animals on conventional ventilati
on using the Sechrist iv-100 ventilator. Arterial blood gases were drawn ev
ery 15 mins, and the ventilator settings were adjusted to the minimal level
that would maintain arterial blood gases in the following ranges: pH 7.35-
7.45, PaCO2 30-40 torr (3.99-5.33 kPa), PaO2 50-70 torr (6.66-9.33 kPa), An
imals were ventilated with the randomized ventilation techniques for 4 hrs.
Measurements and Main Results: Peak inspiratory pressure, mean airway press
ure, and positive end-expiratory pressure were measured at the distal end o
f the endotracheal tube. We recorded these variables plus respiratory rate
at baseline and every 30 mins for a total of 4 hrs of ventilation. Lung com
pliance did not differ between groups at the postlavage study period (ITPV,
0.56 +/- 0.13 mL/cm H2O/kg; conventional 0.49 +/- 0.15 mL/cm H2O/kg). At t
he end of the 4 hr study period, peak inspiratory pressure (ITPV, 26.2 +/-
4.6 cm H2O; conventional, 32.4 +/- 5.04 cm H2O, p = .007) and positive end-
expiratory pressure (ITPV, 3.9 +/- 1.96 cm H2O; conventional, 6.3 +/- 1.42
cm H2O, p = .005) were lower in the ITPV ventilation group. Peak inspirator
y pressure was significantly lower in the ITPV group by 2 hrs into the stud
y.
Conclusion: In this model of surfactant deficiency lung injury, ventilation
and oxygenation were achieved at significantly lower ventilator settings u
sing ITPV compared with conventional ventilation. Long-term studies are nee
ded to determine whether this reduction in ventilation is maintained, and i
f so, if lung injury is reduced.