| Popis: |
Computer-controlled research ventilators for small animals (SAV) are often used to assess the respiratory mechanics’ parameters such as resistance and elastance of the respiratory system in animal models of disease. In commercially available SAVs, it is common to obtain such parameters with the forced oscillation of a given volume of air into respiratory system with a quasi-sinusoidal pattern in a closed pneumatic circuit (i.e. both the injection and the removal of gas during the piston movement). We hypothesized that obtaining the respiratory mechanical parameters with the linear single-compartment model (LSCM) during the forced inspiration and forced expiration (when calculated together) is not sufficient to explain the physiology of the respiratory system exposed to high doses of bronchial agonist. In order to verify this, male Wistar rats (n = 5) were anesthetized, orotracheally intubated, mechanically ventilated at 90bpm (or 1.5Hz) with a tidal volume of 10mL/kg, and a positive end-expiratory pressure (PEEP) was set at 3cmH2O. The ventilation was performed in a commercial mechanical ventilator (flexiVent, SCIREQ Inc., Canada) and the animals were infused with a saline solution (PBS), followed by 3 increasing doses (3, 30 and 300mg/mL) of the bronchial agonist methacholine (MCh). Respiratory parameters were calculated by the LSCM. Pressure and volume data, calibrated and corrected by a proprietary software, were analyzed using a computational routine. The full quasi-sinusoidal signal data was compared to inlet and outlet of air from the lungs separately. The data obtained showed that the difference among the three signals (i.e. whole signal, imposed-inspiration, and imposed-expiration) is pronounced at the higher dose (MCh 300mg/mL). Data from imposed-inspiration alone seem to better reflect the respiratory mechanics when a large dose of bronchial agonist is used. |
