The Science Journal of the American Association for Respiratory Care

2005 OPEN FORUM Abstracts

A COMPARISON OF INTRATRACHEAL PULMONARY VENTILATION WITH CONVENTIONAL MECHANICAL VENTILATION WITH A SALINE INSTILLED MODEL IN RABBITS

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Kook-Hyun Lee, M.D., Chul-Woo Jung, M.D.*, Jin-Tae Kim, M.D. *Department of Anesthesiology, College of Medicine, Seoul National University, Seoul, Korea.

INTRODUCTION: Intratracheal pulmonary ventilation (ITPV) was developed to allow a decrease in physiological dead space during mechanical ventilation. We compared the effect of hybrid ventilation (HV) as a modification of ITPV with a saline instilled model in rabbits

METHODS: A pulmonary injury model was developed by instilling normal saline (3 ml/kg) into the lung of 10 adult rabbits (2.7-3.6 kg). A bent needle (BN) was inserted into the lumen at the tip of a 3.5 jet endotracheal tube. The BN was connected with a bias oxygen source. Conventional mechanical ventilation was performed to maintain PaCO2 at 40 mmHg without a bias gas (CMV group, n=5). Hybrid ventilation (CMV + ITPV) was done by adding a bias gas through the BN (ITPV group, n=5). Airway pressures, a mixed expired CO2 tension, arterial blood gas values and a total gas flow were measured in one hour increments for 5 hours. Alveolar ventilation, dead space ventilation and removed CO2 were calculated at each measurement.

RESULTS: Respiratory variables showed no differences between CMV and ITPV groups during the course of 5 hours in terms of reduction of airway pressures and dead space ventilation. However, after 5 hours' ventilation in each group, an internal comparison between CMV and HV showed significant differences in airway pressures and dead space ventilation.

Internal Comparison of CMV and Hybrid ventilation in CMV and ITPV groups

   CMV group ITPV group
PIP (cmH2O) CMV 20 ± 6 18 ± 5
  HV 16 ± 6 * 13 ± 4 *
Tidal Volume (ml) CMV 18.8 ± 6.3 15.6 ± 3.6
  HV 15.7 ± 5.7 * 12.7 ± 3.4 *
Deas Space (ml) CMV 13.3 ± 5.9 10.3 ± 2.8
  HV 10.2 ± 5.0 * 7.4 ± 2.6 *

*: p < 0.05 compared with CMV

CONCLUSION: HV shows greater efficiency of removing dead space in short time, but long term efficacy remains to be proved with saline-instilled rabbits.

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