Ultraprotective versus apneic ventilation in acute respiratory distress syndrome patients with extracorporeal membrane oxygenation: a physiological study

Abstract

Background: Even an ultraprotective ventilation strategy in severe acute respiratory distress syndrome (ARDS) patients treated with extracorporeal membrane oxygenation (ECMO) might induce ventilator-induced lung injury and apneic ventilation with the sole application of positive end-expiratory pressure may, therefore, be an alternative ventilation strategy. We, therefore, compared the effects of ultraprotective ventilation with apneic ventilation on oxygenation, oxygen delivery, respiratory system mechanics, hemodynamics, strain, air distribution and recruitment of the lung parenchyma in ARDS patients with ECMO.

Methods: In a prospective, monocentric physiological study, 24 patients with severe ARDS managed with ECMO were ventilated using ultraprotective ventilation (tidal volume 3 ml/kg of predicted body weight) with a fraction of inspired oxygen (FiO₂) of 21%, 50% and 90%. Patients were then treated with apneic ventilation with analogous FiO₂. The primary endpoint was the effect of the ventilation strategy on oxygenation and oxygen delivery. The secondary endpoints were mechanical power, stress, regional air distribution, lung recruitment and the resulting strain, evaluated by chest computed tomography, associated with the application of PEEP (apneic ventilation) and/or low V_T (ultraprotective ventilation).

Results: Protective ventilation, compared to apneic ventilation, improved oxygenation (arterial partial pressure of oxygen, p < 0.001 with FiO₂ of 50% and 90%) and reduced cardiac output. Both ventilation strategies preserved oxygen delivery independent of the FiO₂. Protective ventilation increased driving pressure, stress, strain, mechanical power, as well as induced additional recruitment in the non-dependent lung compared to apneic ventilation.

Conclusions: In patients with severe ARDS managed with ECMO, ultraprotective ventilation compared to apneic ventilation improved oxygenation, but increased stress, strain, and mechanical power. Apneic ventilation might be considered as one of the options in the initial phase of ECMO treatment in severe ARDS patients to facilitate lung rest and prevent ventilator-induced lung injury.

Trial registration: German Clinical Trials Register (DRKS00013967). Registered 02/09/2018. https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00013967 .

Keywords: Acute respiratory distress syndrome; Extracorporeal membrane oxygenation; Mechanical ventilation; Respiratory function; Respiratory mechanics; Strain; Transpulmonary pressure; Ventilator-induced lung injury.

Fig. 1

Oxygenation and oxygen delivery for ultraprotective and apneic ventilation and three different fractions of inspired oxygen. A Arterial oxygen saturation; SaO₂, arterial oxygen saturation, FiO₂, fraction of inspired oxygen. B Arterial partial pressure of oxygen. PaO₂, arterial partial pressure of oxygen, FiO₂, fraction of inspired oxygen. C Cardiac output, FiO₂, fraction of inspired oxygen. D Oxygen delivery. FiO₂, fraction of inspired oxygen, brackets denote statistically significant differences between ventilation strategies, p-values are shown above the brackets. a: p < 0.05 ultraprotective ventilation with a FiO₂ of 21% vs. ultraprotective ventilation with a FiO₂ of 50%; b: p < 0.05 ultraprotective ventilation with a FiO₂ of 21% vs. ultraprotective ventilation with a FiO₂ of 90%; c: p < 0.05 ultraprotective ventilation with a FiO₂ of 50% vs. ultraprotective ventilation; with a FiO₂ of 90%; d: p < 0.05 apneic ventilation with a FiO₂ of 21% vs. apneic ventilation with a FiO₂ of 50%; e: p < 0.05 apneic ventilation with a FiO₂ of 21% vs. apneic ventilation with a FiO₂ of 90%; f: p < 0.05 apneic ventilation with a FiO₂ of 50% vs. apneic ventilation with a FiO₂ of 90%

Fig. 2

Air distribution in lung parenchyma, percentage of lung recruitment and strain in the non-dependent, dependent, and whole lung. A Air distribution in lung parenchyma in in the non-dependent, dependent, and whole lung. Black, non-aerated lung volume (− 100 to + 100 hounsfield units); dark grey, poorly inflated lung volume (− 500 to − 100 hounsfield units); light grey, normally inflated lung volume (− 501 to − 900 hounsfield units); white, overinflated lung volume (< − 900 hounsfield units), ZEEP, air distribution at zero end-expiratory pressure; PEEP, air distribution at end-expiratory hold, INSP, air distribution at end-inspiratory hold. B Percentage of recruitment associated to the application of apneic and ultraprotective ventilation in the non-dependent, dependent and whole lung. PEEP, recruitment due to positive end-expiratory pressure from zero positive end-expiratory pressure (ZEEP); tidal volume; recruitment due to tidal volume from end-expiratory pressure. C Static and dynamic strain in the non-dependent, dependent and whole lung. Static, static strain due to the application of PEEP; dynamic, dynamic strain due to the application of tidal volume. Brackets denote statistically significant differences, p values are shown above the brackets. a: p < 0.05 PEEP vs. ZEEP. b p < 0.05 INSP vs. PEEP