Double Cycling During Mechanical Ventilation: Frequency, Mechanisms, and Physiologic Implications

Objectives: Double cycling generates larger than expected tidal volumes that contribute to lung injury. We analyzed the incidence, mechanisms, and physiologic implications of double cycling during volume- and pressure-targeted mechanical ventilation in critically ill patients. Design: Prospective, observational study. Setting: Three general ICUs in Spain. Patients: Sixty-seven continuously monitored adult patients undergoing volume control-continuous mandatory ventilation with constant flow, volume control-continuous mandatory ventilation with decelerated flow, or pressure control-continuous mandatory mechanical ventilation for longer than 24 hours. Interventions: None. Measurements and Main Results: We analyzed 9,251 hours of mechanical ventilation corresponding to 9,694,573 breaths. Double cycling occurred in 0.6%. All patients had double cycling; however, the distribution of double cycling varied over time. The mean percentage (95% CI) of double cycling was higher in pressure control-continuous mandatory ventilation 0.54 (0.34–0.87) than in volume control-continuous mandatory ventilation with constant flow 0.27 (0.19–0.38) or volume control-continuous mandatory ventilation with decelerated flow 0.11 (0.06–0.20). Tidal volume in double-cycled breaths was higher in volume control-continuous mandatory ventilation with constant flow and volume control-continuous mandatory ventilation with decelerated flow than in pressure control-continuous mandatory ventilation. Double-cycled breaths were patient triggered in 65.4% and reverse triggered (diaphragmatic contraction stimulated by a previous passive ventilator breath) in 34.6% of cases; the difference was largest in volume control-continuous mandatory ventilation with decelerated flow (80.7% patient triggered and 19.3% reverse triggered). Peak pressure of the second stacked breath was highest in volume control-continuous mandatory ventilation with constant flow regardless of trigger type. Various physiologic factors, none mutually exclusive, were associated with double cycling. Conclusions: Double cycling is uncommon but occurs in all patients. Periods without double cycling alternate with periods with clusters of double cycling. The volume of the stacked breaths can double the set tidal volume in volume control-continuous mandatory ventilation with constant flow. Gas delivery must be tailored to neuroventilatory demand because interdependent ventilator setting–related physiologic factors can contribute to double cycling. One third of double-cycled breaths were reverse triggered, suggesting that repeated respiratory muscle activation after time-initiated ventilator breaths occurs more often than expected. Additional investigators from the Asynchronies in the Intensive Care Unit (ASYNICU) Group are listed in Appendix 1. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's website (https://ift.tt/29S62lw). Supported, in part, by projects PI09/91074 and PI13/02204, integrated in the Plan Nacional de R+D+I, and cofunded by the Instituto de Salud Carlos III Subdirección General de Evaluación y el Fondo Europeo de Desarrollo Regional, Centro de Investigación Biomédica en Red en Enfermedades Respiratorias, Fundación Mapfre, Fundació Parc Taulí, Plan Avanza TSI-020302-2008-38, Ministerio de Ciencia e Innovación, and Ministerio de Industria, Turismo y Comercio (Spain). Mr. Montanya and Drs. Blanch, Murias, and Lucangelo own stock options of Better Care SL, which is a research and development spinoff of Corporació Sanitària Parc Taulí (Spain). Dr. Subirà disclosed work for hire. Drs. Murias and Blanch disclosed that they are inventors of one Corporació Sanitaria Parc Taulí owned US patent: "Method and system for managed related patient parameters provided by a monitoring device," U.S. Patent No. 12/538,940. Dr. Kacmarek is a consultant for Medtronic and Orange Medical and has received research grants from Medtronic and Venner Medical. His institution received funding from Medtronic and Venner Medical, and he received funding from Medtronic, Orange Medical, and Teleflex. The remaining authors have disclosed that they do not have any potential conflicts of interest. For information regarding this article, E-mail: lblanch@tauli.cat Copyright © by 2018 by the Society of Critical Care Medicine and Wolters Kluwer Health, Inc. All Rights Reserved.

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