Physiological effects of an open lung ventilatory strategy titrated on elastance-derived end-inspiratory transpulmonary pressure: study in a pig model*.

Abstract

In the presence of increased chest wall elastance, the airway pressure does not reflect the lung-distending (transpulmonary) pressure. To compare the physiological effects of a conventional open lung approach titrated for an end-inspiratory airway opening plateau pressure (30 cm H2O) with a transpulmonary open lung approach titrated for a elastance-derived end-inspiratory plateau transpulmonary pressure (26 cm H2O), in a pig model of acute respiratory distress syndrome (HCl inhalation) and reversible chest wall mechanical impairment (chest wall and abdomen restriction). In eight pigs, physiological parameters and computed tomography were recorded under three conditions: 1) conventional open lung approach, normal chest wall; 2) conventional open lung approach, stiff chest wall; and 3) transpulmonary open lung approach, stiff chest wall. As compared with the normal chest wall condition, at end-expiration non aerated lung tissue weight was increased by 116 ± 68 % during the conventional open lung approach and by 28 ± 41 % during the transpulmonary open lung approach (p < .01), whereas cardiac output was decreased by 27 ± 19 % and 22 ± 14 %, respectively (p = not significant). In this model, the end-inspiratory transpulmonary open lung approach minimized the impact of chest wall stiffening on alveolar recruitment without causing hemodynamic impairment.