Aim of study: 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). Conclusion: In this animal model, we observed that microcirculation and systemic blood pressures are correlated and may be significantly improved by using IPR therapy.
|Original language||English (US)|
|Issue number||SUPPL. 2|
|State||Published - Dec 2011|
Bibliographical noteFunding Information:
aDepartment of Emergency Medicine, University of Minnesota Medical Center, Minneapolis, MN, USA bMinnesota Medical Research Foundation, Minneapolis, MN, USA cAdvanced Circulatory Systems, Inc., Roseville, MN, USA dUnited States Army Institute of Surgical Research, Fort Sam Houston, TX, USA eDepartments of Neurology and Medicine-Cardiovascular Division, University of Minnesota Medical Center, University of Minnesota (DY), Minneapolis, MN, USA fWeil Institute of Critical Care Medicine, Rancho Mirage, CA, USA gMicrocirculation/Bioenergetic/Inflammation and Acute Circulatory Insufficiency Laboratory, Paris 7 University (Paris Diderot), France
All animal studies were approved by the Institutional Animal Care Committee of the Minneapolis Medical Research Foundation at Hennepin County Medical Center. All animals received treatment and care in compliance with the 1996 Guide for the Care and Use of Laboratory Animals by the National Research Council in accordance with the USDA Animal Welfare Act, PHS Policy, and the American Association for Accreditation of Laboratory Animal Care.
- Cardiovascular collapse
- Hemorrhagic shock
- Intrathoracic pressure
- Intrathoracic pressure regulation