Spontanatmung beim ARDS – Mythos oder pathophysiologische Rationale: Was gegen Muskelrelaxierung spricht

In 2010, Papazian et al. published that the use of the neuromuscular blocking agent cis-atracurium over 48 hours in the early phase of severe ARDS is associated with a better outcome in patients ventilated with a constant tidal volume. Upon interpreting to the results of this study, it has to be emphasised that the patients had been ventilated in the volume assist/control mode, a mode of mechanical ventilation which rarely allows for an interaction between spontaneous breathing and mandatory ventilation, thus leading to an increased incidence of patient-ventilator asynchrony. The question as to whether a ventilation strategy allowing for unassisted spontaneous breathing may result in a better outcome compared with the volume assist/control mode and the use of neuromuscular blocking agents cannot be answered at the moment because of a lack of appropriate studies. In contrast to the results of the study of Papazian et al., we report in this review the benefts of unassisted spontaneous breathing in ARDS patients. Unassisted spontaneous breathing in the BIPAP/APRV mode leads to alveolar recruitment, decrease of mechanical "stress" and "strain", improvement of the ventilation/perfusion ratio with an amelioration of the pulmonary gasexchange as well as shortening of the length of mechanical ventilation. As in the BIPAP/APRV mode spontaneous breathing occurs in a "superimposed" manner with low tidal volumes, the resulting pleural pressure variations are kept low and consequently the resulting transpulmonary pressure, the main factor for ventilator associated lung injury, also remains low. The better outcome due to neuromuscular blocking agents in the early phase of severe ARDS was verifed using the volume assist/control mode. In the light of the recent literature, recommending the use of neuromuscular blocking agents is not evidence-based while other modes of augmented mechanical ventilation are applied on the basis pathophysiological approved concepts.