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KMID : 0356919950290030399
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Korean Journal of Anesthesiology
1995 Volume.29 No. 3 p.399 ~ p.405
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Effects of Mutual Changes of Tidal Volume and Respiratory Rates on Peak Airway Pressure, Compliance and Resistance during Positive-pressure Mechanical Ventilation
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Abstract
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Since the advent of positive-pressure mechanical ventilator in respiratory support, barotrauma has become a feared complication. Elevated peak airway pressure is one of the risk factors of barotrauma, so it has been tried how to change ventilator
setting to minimize airway pressure. One method is to decrease tidal volume and increase respiratory rates. Therefore we studied changes of airway pressure, compliance and resistance of the total respiratory system according to change tidal
volume
and
respiratory rates.
We selected 23 patients over the age of 15 and with no respiratory problem. And we excluded patients received thoracic and abdomen surgery because airway pressure might be changed by surgical manipulation. The patients without premedication were
ventilated during 5 minutes with 50% oxygen, N2O and isoflurane(1.0 vol%) by closed circuit ventilator(Physio-FlexTM) after slow intravenous injection of thiopental sodium, fentanyl and vecuronium. Then we intubated with I.D. 8 mm sized
endotracheal
tube for men and with I.D. 7 mm for women. Minute ventilation(110 ml/kg), concentration of isoflurane(1.0 vol%), gas flow rate and I:E ratio(1:2) were maintained constantly during controlled ventilation and we increased respiratory rates stepwise
by 2
bpm from 8 to 24 bpm and decreased tidal volume to maintain minute ventilation. At 10 minutes after change of ventilator setting, we checked peak airway pressure, plateau airway pressure, arterial and end-tidal CO2 tension. And then we calculated
compliance and resistance of the total respiratory system.
Peak airway pressure and compliance decreased decreased according to decreasing tidal volume and increasing respiratory rates, but arterial CO2 tension and resistance were not changed.
We concluded that method of decreasing tidal volume and increasing respiratory rates decrease peak airway pressure and keep minute ventiation to prevent hypercarbia. (Korean J Anesthesiol 1995; 29: 399~405)
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