| Research Abstract |
Objectives and Methods : 1) An objective of my investigation is to evaluate the respiratory mechanics and hemodynamics during permissive hypercapnia (PHY) using partial assist ventilation. We produced respiratory failure with oleinic acid on five dogs and ventilated them by pressure support ventilation. The blood gas, the respiratory mechanics and hemodynamics were measured at the support pressure of 30 cmH_2O,25cmH_2O,15cmH_2O,and 5cmH_2O.2) The other objective of my investigation is to evaluate the hemodynamics, intracranial pressure (ICP), tissue acid-base balance and tissue blood flow-oxygenation in induced hypercapnia. We ventilated seven dogs with volume control ventilation and measured the blood gas, hemodynamics, intracranial pressure and tissue pH (pHi) at the tidal volume of 10 ml/kg, 8 ml/kg, and 6 ml/kg.
Results : 1) The respiration and hemodynamics were not changed abnormally at the support pressure of 30 cmH_2O and 25 cmH_2O.Although PaCO_2 did not change, the respiratory
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rate, peak inspiratory flow, work of breathing of patient (WOBp) and heart rate increased at the support pressure of 15 cmH_2O.In addition of these parameters, PaCO_2 increased at the support pressure of 5cmH_2O.2) By changing the tidal volume from 10 ml/kg to 8 ml/kg, the average of PaCO_2, mean pulmonary pressure (mPAP) and ICP elevated from 35.7 mmHg to 57.8 mmHg, from 19.3 mmHg to 22.8 mmHg, and from 19.3 mmHg to 27.5 mmHg respectively and pH decreased from 7.384 to 7.214. The average of PaCO_2, pH,pHi, mPAP,and ICP reached to 90.4 mmHg, 7.057,6.986,26.5 mmHg, and 38.1 mmHg after changing the tidal volume to 6ml/kg.
Conclusions : 1) PHY with partial assist ventilation mode is possible in moderate respiratory failure. The partial assist ventilation, however, should be changed to a control ventilation mode when PaCO_2 elevates besides increases of respiratory rate, WOBp and hheart rate. 2) PHY should be avoided on the patients who have the danger of elevation of ICP and heart failure. PHY,however, did not change pHi critically. Less
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