Scientific article
Open access

Acute hemorrhagic shock decreases airway resistance in anesthetized rat

Published inJournal of applied physiology, vol. 111, no. 2, p. 458-464
Publication date2011

We studied the relation between changes in pulmonary and systemic hemodynamics to those in the airway resistance, respiratory tissue mechanics, and thoracic gas volume (TGV) following acute hemorrhage and blood reinfusion in rats. Forced oscillation technique was used to measure airway resistance (Raw), respiratory tissue damping, and elastance at baseline and after stepwise 1-ml blood withdrawals up to 5 ml total, followed by stepwise reinfusion up to full restoration. Mean systemic (Pam) and pulmonary arterial pressures and suprarenal aortic blood flow were measured at each step. In supplemental animals, plethysmographic TGV, Pam, and respiratory mechanics measurements were performed. Blood volume loss (BVL) led to proportional decreases in Raw (66.5 ± 8.8 vs. 44.8 ± 9.0 cmH(2)O·s·l(-1) with 5 ml, P < 0.001), Pam, and aortic blood flow. In contrast, tissue damping increased significantly (1,070 ± 91 vs. 1,235 ± 105 cmH(2)O/l, P = 0.009 with 5 ml BVL), whereas tissue elastance did not change significantly. TGV significantly increased with acute BVL (3.7 ± 0.2 vs. 4.2 ± 0.2 ml, P = 0.01). Stepwise reinfusions produced opposite changes in the above parameters, with Raw reaching a higher value than baseline (P = 0.001) upon full volume restoration. Both adrenalin (P = 0.015) and noradrenalin levels were elevated (P = 0.010) after 5-ml blood withdrawal. Our data suggest that the decreases in Raw following BVL may be attributed to the following: 1) an increased TGV enhancing airway parenchymal tethering forces; and 2) an increase in circulating catecholamines. The apparent beneficial effect of a reduction in Raw in acute hemorrhagic shock is counteracted by an increase in dead space and the appearance of peripheral mechanical heterogeneities due to de-recruitment of the pulmonary vasculature.

  • Acute Disease
  • Airway Resistance/physiology
  • Anesthesia
  • Animals
  • Blood Volume/physiology
  • Catecholamines/blood
  • Lung Volume Measurements
  • Pulmonary Circulation/physiology
  • Rats
  • Rats, Sprague-Dawley
  • Respiratory Mechanics/physiology
  • Shock, Hemorrhagic/physiopathology
Citation (ISO format)
BAYAT, Sam et al. Acute hemorrhagic shock decreases airway resistance in anesthetized rat. In: Journal of applied physiology, 2011, vol. 111, n° 2, p. 458–464. doi: 10.1152/japplphysiol.00024.2011
Main files (1)
Article (Published version)
ISSN of the journal1522-1601

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