High Tidal Volume Ventilation Is Not Deleterious in Infant Rats Exposed to Severe Hemorrhage

Abstract

and key wordsBackground: Both high tidal volume (V T ) ventilation and hemorrhage induce acute lung injury in adult rodents. It is not known whether injurious ventilation augments lung injury in infant rats exposed to severe hemorrhage. Methods:Two week old rats were allocated to ventilation with V T 7 mL/kg and PEEP 5 cmH 2 O (low V T ) or V T 21 mL/kg and PEEP 1 (high V T ) for 4 h. Additional rats were subjected to volume-controlled hemorrhage and delayed saline resuscitation, followed by low V T or high V T ventilation for 4 h. Non-ventilated control groups were also included.Airway resistance and the coefficient of tissue elastance (H) were derived from respiratory input impedance measurements using the low-frequency forced oscillation technique. Pressure-volume curves were obtained at baseline and at the end of the study.Interleukin-6 (IL-6), macrophage inflammatory protein-2 (MIP-2), and tumor necrosis factor alpha (TNF-α) were determined in bronchoalveolar lavage fluid (BALF) and serum. Results:In both healthy and hemorrhage-exposed animals high V T resulted in reduced H (better lung compliance), and increased transcutaneous oxygen saturation. IL-6 in BALF was greater in ventilated animals when compared to non-ventilated controls, but not different between ventilated groups. No significant differences were found for all other inflammatory mediators, total protein concentration in BALF, and histology. Conclusion:High V T ventilation with low PEEP improves respiratory system mechanics without causing additional damage to healthy and hemorrhage-exposed infant rats after 4 3 h of ventilation. This study highlights the tolerance to high V T ventilation in infant rats and underscores the need for age-specific animal models.

High tidal volume ventilation does not exacerbate acid-induced lung injury in infant rats

“…The elevated IL-6 concentrations in all ventilated groups either imply that ventilation protocols were too short to cause significant differences in biotrauma (Dos Santos and Slutsky, 2006;Bailey et al, 2008) or that a similar degree of mechanical stress occurred during artificial ventilation with both strategies. Overall, our results from both inflammatory response and lung mechanics are consistent with a previous infant rat study showing improvement in lung mechanics following high V T -low PEEP when compared with low V T -high PEEP ventilation in an indirect lung injury model (Cannizzaro et al, 2010). Despite these experimental findings it is too early to draw direct conclusions for clinical practice.…”

Determinants of plasma copeptin: A systematic investigation in a pediatric mechanical ventilation model

“…acute hemorrhage without (n = 8) and with subsequent fluid resuscitation (n = 7), respectively. Acute hemorrhage was produced after 90 min of protective mechanical ventilation via transcutaneous cardiac puncture and withdrawal of ~0.38 mL blood within 30 s. Blood volume was supposed to approximate 7% of body weight (Cannizzaro et al, 2010). Therefore, removing ~0.38 mL blood resulted in a controlled hemorrhage of ~15% estimated blood volume.…”

Impact of high tidal volume ventilation on surfactant metabolism and lung injury in infant rats

“…Results from these age-specific animal studies also challenge the concept of protective low V T ventilation. In fact, high V T ventilation in both one-hit (10,27) and two-hit models (8,41) was associated with improved lung function without aggravated inflammation when compared to control animals. Ex vivo and in vitro studies suggest that mechanical stretch of alveolar epithelial type II (AE2) cells promotes both surfactant de novo synthesis and calcium-induced secretion of surfactant proteins (SPs) and phospholipids (PLs) (1,36).…”