Intratracheal pulmonary ventilation and continuous positive airway pressure in a sheep model of severe acute respiratory failure.
OBJECTIVE
Previously we have shown that optimal pulmonary gas exchange can be sustained at normal airway pressures in a model of severe acute respiratory failure (ARF), using intratracheal pulmonary ventilation (ITPV), with weaning to room air. In an identical model of ARF, we have now explored whether ITPV, combined with continuous positive airway pressure (CPAP), can sustain adequate ventilation, with weaning to room air.


METHODS
Randomized study in sheep.


METHODS
Animal research laboratory at the National Institutes of Health.


METHODS
ARF was induced in 12 sheep, using mechanical ventilation at peak inspiratory pressure of 50 cm H2O, but excluding 5 to 8% of lungs. Sheep were then randomized into two groups: the CPAP-ITPV group (n=6), in which ITPV was combined with a novel CPAP system; and a control group (n=6) in which the same CPAP circuit was used, but without ITPV.


RESULTS
All sheep in the CPAP-ITPV group were weaned to room air in 38.7+/-14 h. PaO2/fraction of inspired oxygen (FIO2) progressively increased from 108.8+/-43 to 355.7+/-93.1; PaCO2 remained within normal range; respiratory rate (RR) ranged from 18 to 120 breaths/min, and tidal volume (VT) was as low as 1.1 mL/kg. All sheep in the control group (CPAP alone) developed severe respiratory acidosis and hypoxemia after 4.8+/-4 h. PaO2/FIO2 decreased from 126.6+/-58.2 to 107.2+/-52.5 mm Hg, with a final PaCO2 of 166.8+/-73.3 mm Hg.


CONCLUSIONS
All sheep treated with CPAP-ITPV maintained good gas exchange without hypercapnia at high RR and at low VT, with weaning to room air. All control animals treated with CPAP alone developed severe hypercapnia, respiratory acidosis, and severe hypoxemia, and were killed.
Giacomini
M
M
Pulmonary-Critical Care Medicine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Md 20892-1590, USA.
Kolobow
T
T
Reali-Forster
C
C
Trawöger
R
R
Cereda
M
M
D000142:Acidosis, Respiratory / Q000209:etiology; D000208:Acute Disease; D000704:Analysis of Variance; D000818:Animals; D002245:Carbon Dioxide / Q000097:blood; D002423:Cause of Death; D004195:Disease Models, Animal; D005260:Female; D006935:Hypercapnia / Q000209:etiology; D000860:Hypoxia / Q000209:etiology; D001239:Inhalation; D007442:Intubation, Intratracheal; D008170:Lung Compliance; D010100:Oxygen / Q000008:administration & dosage / Q000097:blood; D011175:Positive-Pressure Respiration; D011312:Pressure; D011659:Pulmonary Gas Exchange; D012123:Pulmonary Ventilation; D011897:Random Allocation; D012119:Respiration; D012121:Respiration, Artificial; D012126:Respiratory Dead Space; D012131:Respiratory Insufficiency / Q000503:physiopathology / Q000628:therapy*; D012756:Sheep; D013990:Tidal Volume; D015300:Ventilator Weaning
D002245:Carbon Dioxide; D010100:Oxygen