The Science Journal of the American Association for Respiratory Care

2011 OPEN FORUM Abstracts


John R. Priest, Craig D. Smallwood; Respiratory Care, Children's Hospital Boston, Boston, MA

INTRODUCTION: A ventricular assist device (VAD) is a mechanical pump that is used to support heart function in patients with acute or chronic heart failure. These devices can be used in a biventricular or univentricular capacity. We report the case of a patient with a biventricular assist device (BiVAD), spontaneous respiratory drive and auto-triggering. CASE SUMMARY: A 2 year old 8kg female with restrictive cardiomyopathy presented to the cardiac ICU. The patient was intubated on day five of admission due to cardiopulmonary failure; respiratory support was maintained on PC-SIMV. Flow and pressure trigger were set to 1L/min and -2cmH2O respectively. No auto-triggering was observed. Heart function continued to deteriorate and on day fifteen a BiVAD was placed. The patient was not breathing and auto-triggering was detected almost immediately. In order to prevent auto-triggering, flow and pressure trigger sensitivities were set to 1.5L/min and -2.5cmH2O. As the patient recovered, chemical paralytics were lifted and the patient began making spontaneous respiratory efforts. It was technically difficult to set an optimal flow and pressure trigger in order to prevent auto-triggering while preventing dysynchrony and allowing spontaneous triggering. To determine the presence of spontaneous effort we turned the flow and pressure trigger to 10L/min and 10cmH2O respectively. If a negative deflection in pressure was associated with a positive deflection in flow (fig. 1), it was concluded that the patient was making spontaneous efforts. Upon making this determination, it was found that a flow trigger of 2L/min and pressure trigger 2.5cmH2O prevented auto-triggering but allowed adequate patient triggering (fig. 2).The patient was assessed for extubation and was extubated on day 26 to a nasal cannula. DISCUSSION: This case illustrates the impact of a BiVAD on the respiratory system and highlights the importance of discerning patient effort from auto-triggering. Because VADs are often implanted within the chest, it is possible for the pumping action of the VAD to cause changes in intrathoracic pressure. Although these changes are small, they may be enough to cause flow changes in the airway, leading to auto-triggering, hypocapnea, and respiratory alkalosis. The ability to specifically determine spontaneous respiratory efforts in this case ensured appropriate ventilator management in a patient at high risk for auto-triggering and patient-ventilator dysynchrony. Sponsored Research - None