Improving microcirculation with therapeutic intrathoracic pressure regulation in a porcine model of hemorrhage.
OBJECTIVE
Intrathoracic pressure regulation (IPR) has been used to treat hypotension and states of hypoperfusion by providing positive pressure ventilation during inspiration followed by augmentation of negative intrathoracic pressure during expiration. This therapy augments cardiac output and lowers intracranial pressure, thereby providing greater circulation to the heart and brain. The effects of IPR on microcirculation remain unknown.


METHODS
Using a hemorrhagic model, hemodynamics and sublingual microcirculation were evaluated after a 55% blood loss over a 30 min timeframe in 10 female farm pigs (30 kg) previously anesthetized with isoflurane.


RESULTS
After hemorrhage the mean arterial pressure was 27 ± 4 mm Hg. Blood cell velocity, the key indicator of microcirculation, was significantly reduced after the bleed from 1033 ± 175 μm/s pre-bleed to 147 ± 60 μm/s (p < 0.0001). Application of an IPR device reduced airway pressure during expiration to -9 mm Hg after each positive pressure breath (10 mL/kg, 10 breaths/min) and resulted in a rapid increase in systemic hemodynamics and microcirculation. During IPR treatment, average mean arterial pressure increased by 59% to 43 ± 6 mm Hg (p = 0.002) and blood cell velocity increased by 344% to 506 ± 99 μm/s (p = 0.001).


CONCLUSIONS
In this animal model, we observed that microcirculation and systemic blood pressures are correlated and may be significantly improved by using IPR therapy.
Department of Emergency Medicine, University of Minnesota Medical Center, Minneapolis, MN, USA.
Nicolas
N
Segal
Jennifer
J
Rees
Victor A
VA
Convertino
Anja
A
Metzger
Daniel
D
Zarama
Leida
L
Voulgaropoulos
Scott H
SH
McKnite
Demetris
D
Yannopoulos
Wanchun
W
Tang
Eric
E
Vicaut
Keith
K
Lurie
D000818:Animals; D016887:Cardiopulmonary Resuscitation / Q000379:methods*; D004195:Disease Models, Animal; D005260:Female; D006470:Hemorrhage / Q000503:physiopathology / Q000628:therapy*; D008833:Microcirculation / Q000502:physiology*; D009060:Mouth Floor / Q000098:blood supply*; D011312:Pressure; D013552:Swine; D013909:Thorax / Q000502:physiology*