Introduction: Traumatic injury and hypovolemic shock are leading causes of death in children worldwide. We previously demonstrated that augmentation of negative intrathoracic pressure generated by spontaneously breathing through an impedance threshold device (ITD) improves blood pressure and cardiac output in a pediatric porcine model of hemorrhagic shock. However, the optimal method to restore intravascular volume, prevent secondary organ damage, and prevent progression of reversible shock to irreversible circulatory collapse after severe blood loss in children is not known.
Hypothesis: Breathing through an ITD for 90 min prior to fluid resuscitation will safely increase short and long-term survival rates.
Methods: Seventeen spontaneously breathing female piglets (12.4 ± 0.1 kg), anesthetized with propofol, were subjected to a 40% bleed and randomized in a prospective, blinded manner to either a sham or active ITD (cracking pressure of -7 cmH2O, Advanced Circulatory Systems, Minneapolis, MN) for 90 min. Shed blood was then reinfused. Work of breathing (WOB), 90 minute and 24 hour survival were evaluated. Survival analysis was performed using the Wilcoxon Rank Sum Test, Fischer’s Exact Test, and Kaplan-Meier Methods.
Results: Baseline and post-bleed heart rate, blood pressure, lactate levels, and arterial blood gas parameters were similar between groups. Piglets treated with the active ITD had significantly improved survival compared to the piglets treated with the sham ITD at 90 min (8/9 vs. 3/8, p=0.04). At 24 hours, Kaplan-Meier curve analysis revealed improved survival with the active ITD (6/9 vs. 2/8, p=0.04). The 3 animals in the active ITD group that did not survive died at a median time of 280 minutes (82–580), and the 6 animals in the sham group that did not survive, died at a median time of 69 minutes (24 –101) after bleed (p=0.11). The WOB at 45 min (J/L) was 73% higher in the active ITD group than the sham group (1.18 ± 0.07 vs. 0.68 ± 0.07, p= 0.001). The piglets safely tolerated the active ITD therapy.
Conclusion: In this spontaneously breathing, anesthetized piglet model of hemorrhagic shock, treatment with an active ITD for 90 min without supplemental fluid resuscitation significantly improved short and long-term survival rates.
Addition of Impedance Threshold Device Therapy Improves Blood Pressure in the Out-of-Hospital Spontaneously Breathing Hypotensive Patient
