To investigate the effects of both positive end-expiratory pressure (PEEP) and mean airway pressure (Paw) on gas exchange, we used lung lavage to induce severe respiratory insufficiency in six lambs. The animals were then mechanically ventilated at constant tidal volume, respiratory rate, and inspired O2 fraction. PEEP levels were varied -5, +5 and +10 cm H2O around the pressure (Pflex) corresponding to a major change in slope of the inspiratory limb of the respiratory volume-pressure curve. In each animal the effects of the three PEEP levels were studied at two Paw levels, differing by 5 cm H2O. Increasing Paw significantly improved PaO2 and reduced venous admixture. A 5-cm H2O PEEP increase from +5 to +10 did not affect oxygenation; however, oxygenation was significantly better when PEEP was greater than Pflex. Both PaCO2 and anatomic dead space were higher at higher PEEP, and decreased with increasing Paw. Hence, Paw was a major determinant of oxygenation, although a PEEP greater than Pflex appeared necessary to optimize oxygenation at a constant Paw.

Mean airway pressure vs. positive end-expiratory pressure during mechanical ventilation / A. Pesenti, R. Marcolin, P. Prato, M. Borelli, A. Riboni, L. Gattinoni. - In: CRITICAL CARE MEDICINE. - ISSN 0090-3493. - 13:1(1985 Jan), pp. 34-7-37.

Mean airway pressure vs. positive end-expiratory pressure during mechanical ventilation

A. Pesenti;L. Gattinoni
1985-01

Abstract

To investigate the effects of both positive end-expiratory pressure (PEEP) and mean airway pressure (Paw) on gas exchange, we used lung lavage to induce severe respiratory insufficiency in six lambs. The animals were then mechanically ventilated at constant tidal volume, respiratory rate, and inspired O2 fraction. PEEP levels were varied -5, +5 and +10 cm H2O around the pressure (Pflex) corresponding to a major change in slope of the inspiratory limb of the respiratory volume-pressure curve. In each animal the effects of the three PEEP levels were studied at two Paw levels, differing by 5 cm H2O. Increasing Paw significantly improved PaO2 and reduced venous admixture. A 5-cm H2O PEEP increase from +5 to +10 did not affect oxygenation; however, oxygenation was significantly better when PEEP was greater than Pflex. Both PaCO2 and anatomic dead space were higher at higher PEEP, and decreased with increasing Paw. Hence, Paw was a major determinant of oxygenation, although a PEEP greater than Pflex appeared necessary to optimize oxygenation at a constant Paw.
Pulmonary Gas Exchange; Animals; Cardiac Output; Analysis of Variance; Respiratory Insufficiency; Chromatography, Gas; Sheep; Respiration, Artificial; Positive-Pressure Respiration; Pulmonary Wedge Pressure; Tidal Volume
Settore MED/41 - Anestesiologia
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/185576
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