Influence of the equipment used for manual ventilation over the variability of respiratory mechanics in rabbits

Abstract

Introduction A self-inflating bag is used for newborns' manual ventilation, using an oxygen concentration close to 100%, unknown peak inspiratory pressure (PIP), no end positive expiratory pressure (PEEP) and high tidal-volume (Vt). Manual ventilation using a T-piece device allows better control of PIP, use of PEEP and probably less variation in pulmonary ventilation. Objective To compare using an experimental model with the adult rabbit, the variability of PIP, PEEP, Vt, minute ventilation (VMin), respiratory rate (RR), inspiratory time (Tins), expiratory time (Tex) and ratio Tins/Total time during manual ventilation using a self-inflating bag or T-piece device. Methods Adult New Zealand White rabbits were manually ventilated by 21 individuals using a self-inflating bag (LIFESAVER(registered trademark) Neonate Manual Resuscitator; Teleflex Medical, Research Triangle Park, NC, USA) or a T-piece device (Babypuff(registered trademark) Fanem Ltd, Sao Paulo, Brazil). Before ventilation each animal was sedated with intramuscular ketamine- acepromazine solution (10 mg/kg and 0.1 mg/kg, respectively) and anesthetized (1% lidocaine, s.c.) at the site of incision for tracheostomy and carotid cannulation. After curarization (pancuronium 1 mg/kg, i.v.) the ventilation was started and ventilatory data (PIP, PEEP, Vt, minute volume, inspiratory and expiratory time) were continuously recorded until sacrifice with sodium pentobarbital (100 mg/kg, i.v.), after 10-minute ventilation. For each variable analyzed a variability index was calculated, defined as the standard deviation of the mean values of each variable during the 10-minute ventilation. Statistical analysis was by t test or Mann-Whitney test, significance was set at P = 0.05. (Table presented) Results The variability indices for all variables analyzed during the 10-minute ventilation are shown in Table 1. Conclusion The authors conclude that the use of a T-piece device allows lower variability during manual ventilation, with the exception of respiratory rate and expiratory time. We speculate that this lower variability could result in lower lung injury during manual ventilation.