Transpulmonary‑pressure guided strategy in severe ARDS treated with VV‑ECMO

Would a ventilation strategy guided by transpulmonary pressure (Ptp) increase the proportion of patients successfully weaned from extracorporeal membrane oxygenation (ECMO) support when compared to the lung‑rest strategy (LRS) recommended by the Extracorporeal Life Support Organization (ELSO) guidelines for patients with severe ARDS?

• Previous studies have suggested that adjusting ventilator settings based on Ptp measurements may minimize ventilator‑induced lung injury (VILI). 
• The effect of a ventilation strategy guided by Ptp in patients with severe ARDS supported with VV‑ECMO has never been investigated previously. 
• Setting the ventilator parameters during venovenous (VV)‑ECMO is challenging and there have been several recommendations published over the past decades. 
• This study compared the outcome of a ventilation strategy guided by Ptp with the outcome of a lung‑rest strategy recommended by the ELSO guidelines for patients with severe ARDS (Wang R, Sun B, Li X, et al. Mechanical Ventilation Strategy Guided by Transpulmonary Pressure in Severe Acute Respiratory Distress Syndrome Treated With Venovenous Extracorporeal Membrane Oxygenation. Crit Care Med. 2020;48(9):1280-1288. doi:10.1097/CCM.00000000000044451​).  
   

• Single‑center, prospective, randomized controlled trial
• All nurses and other research personnel were blinded to the randomization schedule and block size; however, due to the nature of the intervention, physicians and nurses could not be blinded to group assignments
• Conducted in a 16‑bed, respiratory ICU at a tertiary academic medical center
   

• Severe ARDS patients receiving VV‑ECMO 
• A sample size of 48 participants per group was chosen to have 80% power to demonstrate the superiority of the intervention for the primary endpoint (proportion of patients successfully weaned from VV‑ECMO) 
   

• A total of 104 patients were randomized to Ptp‑guided ventilation group (n = 52) or lung‑rest strategy group (n = 52).
• Two patients had cardiac arrest during establishment of  VV‑ECMO in the lung‑rest group  and did not receive the assigned intervention. Thus, 102 patients were included in the analysis.
   

• The proportion of patients successfully weaned from VV‑ECMO in the Ptp‑guided ventilation group was significantly higher than that in the lung rest group (71.2% vs 48.0%; p = 0.017).

Mortality at 60 days 

• The 60‑day mortality rate in the Ptp‑guided group was significantly lower than that of the lung rest group (32.6% vs 54%; p = 0.030). 

• Kaplan‑Meier analysis indicated that the Ptp‑guided group had a significantly higher 60‑day survival rate (p = 0.037) compared to the lung rest group.

ECMO duration

• ECMO duration was significantly shorter in the Ptp‑guided group (p = 0.004).

Mortality at 6 months 

• The 6 months mortality rate in the Ptp‑guided group was significantly lower than that of the lung rest group (36.5 % vs 56%; p = 0.049).
• Ventilator‑free days at day 60, length of ICU and hospital stays, combined renal replacement therapy and tracheostomy were similar between both groups.
• Driving pressure, tidal volumes, and mechanical power were all significantly lower in the Ptp‑guided group compared to the LRS group.
• PEEP was significantly higher in the Ptp‑guided group during VV‑ECMO. 
• In the Ptp‑guided group, levels of interleukin‑1beta, interleukin‑6, and interleukin‑8 were significantly lower, and interleukin‑10 was significantly higher than in the LRS group over time.
• Lung density was significantly lower in the Ptp‑guided group after VV‑ECMO than in the LRS group

A Ptp‑guided ventilation strategy was able to increase the proportion of patients with severe ARDS successfully weaned from VV‑ECMO when compared to LRS.

• A Ptp‑guided ventilation strategy was able to increase the proportion of patients with severe ARDS successfully weaned from VV‑ECMO when compared to LRS.
• A Ptp‑guided ventilation strategy may help improve survival and lung function by better stabilizing lung morphology and reducing markers of VILI when compared to LRS. 
• Results should be confirmed by other large multicenter studies.

1. The HAMILTON‑G5/S1 and HAMILTON‑C6 ventilators offer an auxiliary port for connecting the esophageal catheter pressure line. The clinician can then display the waveform for absolute values of esophageal and transpulmonary pressures.
2. Esophageal manometry as a surrogate for Ppl allows us to separate the lung from chest wall mechanics assessment and provides useful information for monitoring and potentially optimizing mechanical ventilation.
3. Esophageal manometry may help prevent ventilator‑induced lung injury by optimizing recruitment of the dependent lung, while avoiding overdistention of the nondependent lung.
4. When patients have an active muscle contraction, Pes tracings are a handy tool for diagnosing all types of asynchronies, as well as for measuring PL and breathing effort.
5. For difficult‑to‑wean patients later in the ventilation process, quantifying the effort and changes in the amount of effort during SBTs can help clinicians better understand the patient's condition and potential treatment.

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