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Respir Care. 2012 Aug;57(8):1334-6. doi: 10.4187/respcare.01378. Epub 2012 Feb 17.

Inadvertent triggering of the ventilator caused by surgically placed pacer wires.

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Department of Respiratory Care, Sentara Norfolk General Hospital, Norfolk, Virginia, USA.


Inadvertent ventilator triggering can occur for various reasons. Leaks in the ventilator circuit, endotracheal tube leaks, tracheal cuff leaks, cardiac oscillations, water condensate causing oscillations in the circuit tubing, ventilator expiratory valve integrity, and overly sensitive triggering mechanism settings may precipitate this phenomena. We present a case of inadvertent ventilator triggering caused by electrical stimulation of the diaphragm from surgically placed pacing wires post cardiothoracic surgery. A 47-year-old woman underwent surgical placement of a left (LVAD) and right (RVAD) ventricular assist device for severe end stage cardiomyopathy, as a bridge to cardiac transplantation. The patient was observed to have inadvertent ventilator triggering while deeply sedated postoperatively. The ventilator set respiratory rate was 16 breaths/min, with patient respiratory rate of 30 breaths/min while deeply sedated. Upon assessment of ventilator waveforms and arterial blood gas revealing a profound respiratory alkalosis, the pressure/time waveform demonstrated a -2 cm H(2)O decrease in pressure prior to each cycled breath. The ventilator was subsequently changed from flow trigger sensitivity of 3 L/min to pressure trigger sensitivity of -3 cm H(2)O to eliminate the autotriggering. Later in the patient's ICU stay, inadvertent ventilator triggering was again observed. Further adjustment of the pressure trigger sensitivity to -3 cm H(2)O eliminated the autotriggering. Clinical assessment found the pacing wires were responsible for stimulating the patient's diaphragm, therefore causing airway pressure decreases and premature breath delivery. Once the electrical amplitude of the pacemaker was decreased, the inadvertent ventilator triggering resolved and normal trigger sensitivity and pH was restored.

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