Anesth Analg 2001;92:161-165
© 2001 International Anesthesia Research Society
CRITICAL CARE AND TRAUMA
The Effect of Breath Termination Criterion on Breathing Patterns and the Work of Breathing During Pressure Support Ventilation
Hiroaki Tokioka, MD,
Toshiaki Tanaka, MD,
Tomoko Ishizu, MD,
Tomihiro Fukushima, MD,
Toshio Iwaki, MD,
Yuko Nakamura, MD, and
Yoshinori Kosogabe, MD
Department of Anesthesiology, Okayama Rosai Hospital, Okayama, Japan
Address correspondence and reprint requests to Hiroaki Tokioka, MD, Department of Anesthesiology, Okayama Rosai Hospital, 1-10-25 Chikko-Midorimachi, Okayama, 702-8055, Japan.
With pressure support ventilation (PSV), each PSV breath is flow-cycled, and the breath termination criterion (TC) is usually nonadjustable. When TC does not match the interaction between the patients inspiratory-expiratory efforts to the opening and closing of the inspiratory and expiratory valves, patient-ventilator asynchrony may occur, and the work of breathing (WOB) may increase. Therefore, we studied the effect of TC on breathing patterns and WOB during PSV in eight patients with acute respiratory distress syndrome or acute lung injury. We studied five levels of TC during PSV1%, 5%, 20%, 35%, and 45% of the peak inspiratory flow. With increasing levels of TC, the tidal volume decreased and respiratory frequency increased, along with a decrease in duty cycle. WOB markedly increased with increasing levels of TC from 0.31 ± 0.12 J/L with TC 1% to 0.51 ± 0.11 J/L with TC 45%. Premature termination with double breathing occurred in one patient with TC 35% and four patients with TC 45%. Delayed termination with a duty cycle of >0.5 occurred in two patients with TC 1%. In conclusion, the proper adjustment of TC improves patient-ventilator synchrony and decreases WOB during PSV.
Implications: Although termination criterion (TC) is usually nonadjustable, it influences the effectiveness of pressure support ventilation for mechanical ventilation. The proper adjustment of TC is crucial to improve patient-ventilator synchrony and decrease work of breathing. TC 5% of the peak inspiratory flow may be the optimal value for patients with acute respiratory distress syndrome or acute lung injury.
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