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KMID : 0356019930080020091
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Koean Jounral of Critical Care Medicine
1993 Volume.8 No. 2 p.91 ~ p.96
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.Comparision between Demand Valve and Flow-by System during Continuous Positive Airway Pressure Ventilation
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Abstract
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The use of continuous positive airway pressure(CPAP) has contibuted greatly to the management of respiratory failure associated with acute lung disease and to weaning patients from mechanical ventilation, but CPAP would be expected to increase
work
of
breathing even if it was applied effectively.
In our study CPAP was applied to patients on mechanical ventilations by the use of flow-by system and demand valve system. We studied to determine the differences of flow-by system and demand valve system by measuring hemodynamics and ventilatory
variables.
Each patient was studied in random order for the two CPAP systems: a) Demand valve system: pressure trigger sensitivity of -1.5 cmH2O: b) flow-by system: base flow of 10 L/min and flow trigger sensitivity of 3L/min. The patients were maintained
at
constant level ranging from 5 to 10 cmH2O.
@ES The results were as follows:
@EN 1) In the decrease of inspiratory airway pressure, demand valve system was-5.4±1.5 cmH2O and flow-by system was-1.0±0.4 cmH2O.
2) In the increase of expiratory airway pressure, demand valve system was 1.9±1.6 cmH2O and flow-by system was 1.2±0.6 cmH2O.
These results suggested that airway pressure fluctuation due to the inspiratory pressure drop and an increase in expiratory pressure was reduced significantly with the flow-by system than demand valve system.
Therefore, the flow-by system offered the advantage of reducing work of breathing in terms of airway pressure fluctuation and would be beneficial to patients breathing spontaneously with CPAP.
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KEYWORD
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