Patient-ventilator interactions during volume-support ventilation: asynchrony and tidal volume instability--a report of three cases.
During pressure-support ventilation, tidal volume (V(T)) can vary according to the level of the patient's respiratory effort and modifications of the thoraco-pulmonary mechanics. To keep V(T) as constant as possible, the Siemens Servo 300 ventilator proposes an original modification of pressure-support ventilation, called volume-support ventilation (VSV). VSV is a pressure-limited mode of ventilation that uses V(T) as a feedback control: the pressure support level is continuously adjusted to deliver a preset V(T). Thus, the ventilator adapts the inspiratory pressure level, breath by breath, to changes in the patient's inspiratory effort and the mechanical thoraco-pulmonary properties. The clinician sets V(T) and respiratory frequency, and the ventilator calculates a preset minute volume. It has been shown that ineffective respiratory efforts can occur during pressure-support ventilation.
Sottiaux
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Intensive Care Unit, Clinique Notre Dame de Grâce, 212, Chaussée de Nivelles, 6041 Gosselies, Belgium. thierry.sottiaux@skynet.be
D005260:Female; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000503:physiopathology / Q000628:therapy; D008297:Male; D011175:Positive-Pressure Respiration / Q000009:adverse effects* / Q000379:methods*; D012120:Respiration Disorders / Q000503:physiopathology / Q000628:therapy*; D013990:Tidal Volume; D012122:Ventilators, Mechanical