The impacts of baseline ventilator parameters on hospital mortality in acute respiratory distress syndrome treated with venovenous extracorporeal membrane oxygenation: a retrospective cohort study

Abstract

Background: Venovenous extracorporeal membrane oxygenation (VV-ECMO) is a valuable life support in acute respiratory distress syndrome (ARDS) in adult patients. However, the success of VV-ECMO is known to be influenced by the baseline settings of mechanical ventilation (MV) before its institution. This study was aimed at identifying the baseline ventilator parameters which were independently associated with hospital mortality in non-trauma patients receiving VV-ECMO for severe ARDS.

Methods: This retrospective study included 106 non-trauma patients (mean age: 53 years) who received VV-ECMO for ARDS in a single medical center from 2007 to 2016. The indication of VV-ECMO was severe hypoxemia (P_aO₂/ FiO₂ ratio < 70 mmHg) under pressure-controlled MV with peak inspiratory pressure (PIP) > 35 cmH₂O, positive end-expiratory pressure (PEEP) > 5 cmH₂O, and F_iO₂ > 0.8. Important demographic and clinical data before and during VV-ECMO were collected for analysis of hospital mortality.

Results: The causes of ARDS were bacterial pneumonia (n = 41), viral pneumonia (n = 24), aspiration pneumonitis (n = 3), and others (n = 38). The median duration of MV before ECMO institution was 3 days and the overall hospital mortality was 53% (n = 56). The medians of PaO₂/ FiO₂ ratio, PIP, PEEP, and dynamic pulmonary compliance (PC_dyn) at the beginning of MV were 84 mmHg, 32 cmH₂O, 10 cmH₂O, and 21 mL/cmH₂O, respectively. However, before the beginning of VV-ECMO, the medians of PaO₂/ FiO₂ ratio, PIP, PEEP, and PC_dyn became 69 mmHg, 36 cmH₂O, 14 cmH₂O, and 19 mL/cmH₂O, respectively. The escalation of PIP and the declines in PaO₂/ FiO₂ ratio and PC_dyn were significantly correlated with the duration of MV before ECMO institution. Finally, the duration of MV (OR: 1.184, 95% CI: 1.079-1.565, p < 0.001) was found to be the only baseline ventilator parameter that independently affected the hospital mortality in these ECMO-treated patients.

Conclusion: Since the duration of MV before ECMO institution was strongly correlated to the outcome of adult respiratory ECMO, medical centers are suggested to find a suitable prognosticating tool to determine the starting point of respiratory ECMO among their candidates with different duration of MV.

Trial registration: This study reported a health care intervention on human participants and was retrospectively registered. The Chang Gung Medical Foundation Institutional Review Board approved the study (no. 201601483B0 ) on November 23, 2016. All of the data were extracted from December 1, 2016, to January 31, 2017.

Keywords: Adult respiratory distress syndrome; Lung recruitment; Lung-protective mechanical ventilation; Venovenous extracorporeal membrane oxygenation.

Fig. 1

Flow chart of patient distribution and managements during venovenous extracorporeal membrane oxygenation. ARF: Acute respiratory failure. FiO2: The fraction of inspired oxygen. PaO2: Arterial oxygen tension. PEEP: Positive end-expiratory pressure. PIP: Peak inspiratory pressure. RR: Respiratory rate. SaO2: Arterial oxygen saturation; SpO2: Oxyhemoglobin saturation by pulse oximetry. V_T: Tidal volume. VV-ECMO: Venovenous extracorporeal membrane oxygenation

Fig. 2

Observed mortality rates among patients categorized by the baseline sequential organ failure assessment (SOFA) score. The case number in each group is also presented

Fig. 3

Survivors’ trends of PF ratio and dynamic driving pressure during the support of VV-ECMO. (T₀: 1–2 h after intubation for MV, T₁: 1–2 h before ECMO cannulation, T₂:24 h after ECMO institution, T₃: 1–2 h before ECMO decannulation, and T₄: 24 h after ECMO removal)