Lung Mechanics Analysis in Anesthetized Rats

One week after the last administration of saline or ghrelin (Fig. 1b), animals were pre-medicated with diazepam [(10 mg kg^-1, i.p.) Compaz®, Cristália, Itapira, SP, Brazil], anaesthetised with thiopental sodium [(20 mg kg^-1 i.p.) Thiopentax®, Cristália, Itapira, SP, Brazil], tracheotomised, paralysed with Vecuronium bromide 0.005 mg kg^-1 i.v. (Vecuron®, Cristália, Itapira, SP, Brazil), and ventilated with a constant flow ventilator (Samay VR15; Universidad de la Republica, Montevideo, Uruguay) set as follows: respiratory rate 100 breaths/min, tidal volume (V_T) 0.2 mL, and fraction of inspired oxygen (FiO₂) 0.21. The anterior chest wall was surgically removed and a positive end-expiratory pressure (PEEP) of 2 cmH₂O applied. Airflow and tracheal pressure (Ptr) were measured. In an open chest preparation, Ptr reflects transpulmonary pressure (PL). Lung mechanics were analysed by the end-inflation occlusion method [25 (link), 26 (link)]. Static lung elastance (Est,L) was determined by dividing lung elastic recoil pressure (Pel) by V_T. Est,L was measured 10 times in each animal. All data were analysed using ANADAT software (RHT-InfoData, Inc., Montreal, Quebec, Canada). All experiments lasted less than 15 min.