An improved in vivo rat model for the study of mechanical ventilatory support effects on organs distal to the lung

Objective: To study the influence of different mechanical ventilatory support strategies on organs distal to the lung, we developed an in vivo rat model, in which the effects of different tidal volume values can be studied while maintaining other indexes. Design: Prospective, randomized animal laboratory investigation. Setting: University laboratory of Ospedale Maggiore di Milano-Instituto di Ricovero e Cura a Carattere Scientifico. Subjects: Anesthetized, paralyzed, and mechanically ventilated male Sprague-Dawley rats. Interventions: Two groups of seven rats each were randomized to receive tidal volumes of either 25% or 75% of inspiratory capacity (IC), calculated from a preliminary estimation of total lung capacity. Ventilation strategies for the two groups were as follows: a) 25% IC, 9.9 ± 0.8 mL/kg; frequency, 59 ± 4 beats/min; positive end-expiratory pressure, 3.6 ± 0.8 cm H2O; and peak inspiratory airway pressure (P̄āw), 13.2 ± 2 cm H2O; and b) 75% IC, 29.8 ± 2.9; frequency, 23 ±...