A New Parameter to Study the Respiratory Airways Hyper-reactivity in an Ovalbumin- Induced Rat Model of Asthma

Aim: The present study was purported to determine the value and applicability of positive end-inspiratory pressure (PEIP) for the in vivo assessment of airways responsiveness (AR) in an experimental model of asthma induced in rats by ovalbumin (OVA) sensitization. Materials and methods: Male Sprague–Dawley rats were randomized in two groups: a control group (CON, n = 8) and a group sensitized by ovalbumin (OVA, n = 8). After anesthesia (sodium thiopenthal 50 mg/kg), animals were mechanically ventilated (respiratory rate of 80-90 /min, current volume of 10 ml/kgc, and a positive end expiratory pressure of 3 cmH2O). For the in vivo assessment of AR, a nebulizer with metacholine (MCh, 1 mg/ml) was placed along the inspiratory limb of the ventilation circuit. In both groups PEIP was determined before and after MCh administration. We have further determined the in vitro reactivity of tracheal smooth muscle (spiral strips) challenged with a submaximal dose of MCh (10-5 M) in isolated organ bath. Results: In the in vivo study, PEIP values recorded after MCh were 24.75 ± 2.54 cmH2O were significantly decreased in CON group vs. 39.5 ± 4.95 cmH2O in OVA group, respectively (p < 0,001). In the in vitro experiments, Mch (10-5M) elicited a submaximal contractile response of spiral tracheal strips (CON: 0.93 ± 0.25 g force, OVA: 1.16 ± 0.15 g force, p < 0.05). Conclusions: In the rat model of allergic asthma, positive end-inspiratory pressure is a valid index of in vivo airways hyperreactivity as confirmed by the comparable results obtained in isolated organ bath. We propose the determination of this parameter as a physiologically valid measure of airway hyperresponsiveness in allergic rodents.