Abstract Body: Background: Hemorrhagic shock, precipitated by rapid blood loss, is highly lethal. Successful treatment requires rapid stabilization to prevent mortality. Ventilatory support may be required when accompanied by respiratory failure, and in austere prehospital settings is most likely to occur via manual bagging, which carries risks of barotrauma and hemodynamic compromise. Airway flow limiting devices can facilitate correct manual ventilation, but their utility in the hemorrhagic shock resuscitation setting is not well established.
Objective: Evaluate the use of an airway flow limiting device on manual ventilation performance and hemodynamics in a preclinical model of hemorrhagic shock resuscitation.
Methods: We sedated, anesthetized and intubated 20 mixed-breed Yorkshire swine, mean(SD) weight 53.1(4) kg. Animals were mechanically ventilated at 8mL/kg while undergoing instrumentation (pressure transducer in descending aorta via femoral cutdown for assessing mean arterial pressure (MAP) and systolic blood pressure (SBP)). Airway flow, pressure (P_AW) and tidal volume (V_T) were monitored continuously. We bled animals in 60cc draws until MAP <40mmHg, and then commenced manual bagging, with animals randomized to standard ventilation (“SHAM”) or flow modulated ventilation (“FM”; Sotair, SafeBVM, Inc). Respiratory rate was guided by a metronome, dynamically adjusted to maintain eucapnia. After 30 min, all withdrawn blood was returned and bagging continued for another 30 min. Performance and hemodynamic parameters were compared between groups and across shock & resuscitation phases (t-tests; ANOVA). a = 0.05 was the threshold for statistical significance.
Results: Fourteen pigs survived initial hemorrhage until randomization (1 animal arrested during resuscitation) and initiation of bagging (FM, n = 7; SHAM, n = 7). Airway performance parameters differed between FM and SHAM (p<0.001). MAP and SBP did not differ between FM and SHAM groups but differed between phases (p<0.001).
Conclusions: Bagged ventilations with a flow modulation device resulted in more favorable ventilation performance, but no differences in hemodynamics during hemorrhagic shock/resuscitation.