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

Abstract

RATIONALE: In the presence of increased chest wall elastance, the airway pressure does not reflect the lung-distending (transpulmonary) pressure. OBJECTIVE: 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). METHODS: 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. MEASUREMENTS AND MAIN RESULTS: As compared with the normal chest wall condition, at end-expiration non aerated lung tissue weight was increased by 116 &#xb1; 68 % during the conventional open lung approach and by 28 &#xb1; 41 % during the transpulmonary open lung approach (p < .01), whereas cardiac output was decreased by 27 &#xb1; 19 % and 22 &#xb1; 14 %, respectively (p = not significant). CONCLUSION: In this model, the end-inspiratory transpulmonary open lung approach minimized the impact of chest wall stiffening on alveolar recruitment without causing hemodynamic impairment.