Understanding Patient-Ventilator Asynchrony
People display normal variability in their breathing patterns even at rest. In contrast, although a necessary medical intervention, mechanical ventilation uses some sort of fixed parameter in almost all currently available modes. If the mechanical breath is delivered in a fashion that the patient doesn’t want or expect (too short, not enough flow, too long, etc.), asynchrony between the ventilator and the patient, discomfort, anxiety and fatigue can result.([FOOTNOTE=de Wit M. Monitoring of patient ventilator interaction at the bedside. Respiratory Care. 2011;56(1):61-68.],[ANCHOR=],[LINK=])
Eight out of 10 ventilated patients come off the vent within three to four days with little difficulty.([FOOTNOTE=Thille AW et al. Patient-ventilator asynchrony during assisted mechanical ventilation. Intensive Care Med. 2006;32(10):1515-1522.],[ANCHOR=],[LINK=]),([FOOTNOTE=Anzueto A, Peters JI, Tobin MJ, et al. Effects of prolonged controlled mechanical ventilation on diaphragmatic function in healthy adult baboons. Crit Care Med. 1997;25(7):1187-1190.],[ANCHOR=],[LINK=]) They might be uncomfortable under mechanical ventilation, but they are able to wean from the ventilator. Still, in these patients, improving patient-ventilator synchrony may potentially result in less anxiety and need for sedation.([FOOTNOTE=Siegel MD. Management of agitation in the intensive care unit. Clin Chest Med. 2003;24(4):713-725.],[ANCHOR=],[LINK=])
Those who stay on ventilation longer (~25%) and continue to fail to wean use 50% of our ICU resources, accounting for 40% of all ICU costs.3,([FOOTNOTE=Hermans G. Increased duration of mechanical ventilation is associated with decreased diaphragmatic force: a prospective observational study. Crit Care. 2010;14:R127.],[ANCHOR=],[LINK=]) In these patients, asynchrony may have a greater impact.2,([FOOTNOTE=de Wit M, Miller KB, Green DA, Ostman HE, Gennings C, Epstein SK. Ineffective triggering predicts increased duration of mechanical ventilation. Crit Care Med. 2009;37(10):2740-2745.],[ANCHOR=],[LINK=]),([FOOTNOTE=Xirouchaki N, Kondili E, Vapoidi K, et al. Proportional assist ventilation with load-adjustable gain factors in critically ill patients: comparison with pressure support. Int Care Med. 2008;34:2026-2034.],[ANCHOR=],[LINK=]),([FOOTNOTE=Epstein SK. Optimizing patient-ventilator synchrony. Semin Respir Crit Care Med. 2001;22(2):137-152.],[ANCHOR=],[LINK=])