Measuring tidal volume (V-T) in nonintubated swine or swine with leaking breathing circuits is challenging. The aim of this study was to validate respiratory inductance plethysmography (RIP) for measuring V-T in swine that are comparable in size to adult humans. To determine calibration curves, V-T and RIP readings were obtained from anesthetized swine (n = 8; weight, 46-50 kg) during positive-pressure (mechanical) ventilation and spontaneous breathing. For positive-pressure ventilation, 6 pigs were mechanically ventilated by using the pressure-control mode. The 2 pigs in the spontaneously breathing cohort each received a single intravenous bolus dose of propofol to abolish spontaneous breathing; V-T was measured during gradual return of their respiratory drive. A flow volume sensor was placed between the proximal end of the endotracheal tube and breathing circuit for the recording of inspiratory and expiratory V-T. RIP readings were recorded by using 2 bands, which simultaneously measured ribcage and abdominal excursions. The data revealed that V-T was linearly correlated with the movements of both ribcage and abdomen as measured by using plethysmography over a large range of tidal volume (44 to 1065 mL). In addition, the intercept of the linear equation was small or even negative during spontaneous breathing but increased significantly (maximum, 145 mL, 59.2 +/- 35.1 mL) during positive pressure ventilation. Our results indicate that V-T in swine can be calculated by using a simple univariate linear regression equation with RIP readings obtained during either mechanical ventilation or spontaneous breathing.
[1]Jilin Univ, China Japan Union Hosp, Dept Anesthesia, Changchun 130023, Peoples R China.
[2]Massachusetts Gen Hosp, Dept Anesthesia Crit Care & Pain Med, Boston, MA 02114 USA.
[3]Massachusetts Gen Hosp, Dept Resp Care Serv, Boston, MA 02114 USA.
[4]Jining Med Univ, Affiliated Hosp, Dept Obstet & Gynecol, Jining, Peoples R China.
[5]Massachusetts Gen Hosp, Div Trauma Emergency Surg & Surg Crit Care, Knight Surg Res Lab, Operat, Boston, MA 02114 USA.
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