Comparison of different inspiratory triggering settings in automated ventilators during cardiopulmonary resuscitation in a porcine model

<div><p>Background</p><p>Mechanical ventilation via automated in-hospital ventilators is quite common during cardiopulmonary resuscitation. It is not known whether different inspiratory triggering sensitivity settings of ordinary ventilators have different effects on actual ventilation, gas exchange and hemodynamics during resuscitation.</p><p>Methods</p><p>18 pigs enrolled in this study were anaesthetized and intubated. Continuous chest compressions and mechanical ventilation (volume-controlled mode, 100% O₂, respiratory rate 10/min, and tidal volumes 10ml/kg) were performed after 3 minutes of ventricular fibrillation. Group trig-4, trig-10 and trig-20 (six pigs each) were characterized by triggering sensitivities of 4, 10 and 20 (cmH₂O for pressure-triggering and L/min for flow-triggering), respectively. Additionally, each pig in each group was mechanically ventilated using three types of inspiratory triggering (pressure-triggering, flow-triggering and turned-off triggering) of 5 minutes duration each, and each animal matched with one of six random assortments of the three different triggering settings. Blood gas samples, respiratory and hemodynamic parameters for each period were all collected and analyzed.</p><p>Results</p><p>In each group, significantly lower actual respiratory rate, minute ventilation volume, mean airway pressure, arterial pH, PaO₂, and higher end-tidal carbon dioxide, aortic blood pressure, coronary perfusion pressure, PaCO₂ and venous oxygen saturation were observed in the ventilation periods with a turned-off triggering setting compared to those with pressure- or flow- triggering (all <i>P</i><0.05), except when compared with pressure-triggering of 20 cmH₂O (respiratory rate 10.5[10/11.3]/min vs 12.5[10.8/13.3]/min, <i>P</i> = 0.07; coronary perfusion pressure 30.3[24.5/31.6] mmHg vs 27.4[23.7/29] mmHg, <i>P</i> = 0.173; venous oxygen saturation 46.5[32/56.8]% vs 41.5[33.5/48.5]%, <i>P</i> = 0.575).</p><p>Conclusions</p><p>Ventilation with pressure- or flow-triggering tends to induce hyperventilation and deteriorating gas exchange and hemodynamics during CPR. A turned-off patient triggering or a pressure-triggering of 20 cmH2O is preferred for ventilation when an ordinary inpatient hospital ventilator is used during resuscitation.</p></div

Aortic blood pressure, right atrial pressure and mean airway pressure during the inspiratory phase of an animal in Group trig-20.

<p>The period indicated by dotted box is the decompression phase of chest compressions. Coronary perfusion (shadow area) is indicated by the area between red and blue line in the dotted box. (A), Turned-off triggering. (B), A pressure-triggering of 20 cmH₂O. (C), A flow-triggering of 20 L/min.</p

Physiological parameters at baseline.

<p>Physiological parameters at baseline.</p

Experimental protocol.

<p>VF, ventricular fibrillation.</p

Venous-arterial CO₂ gradients in Group trig-20 (median, 25/75% percentiles, min/max) [mmHg].

<p>Venous-arterial CO₂ gradients in Group trig-20 (median, 25/75% percentiles, min/max) [mmHg].</p

Results of Arterial and Venous blood Gas Analysis.

<p>Results of Arterial and Venous blood Gas Analysis.</p