UMEM Educational Pearls

During the height of the pandemic, a large proportion of patients who were referred to our center for VV-ECMO evaluation were on Airway Pressure Release Ventilation (APRV).  Does this ventilation mode offer any advantage?  This new randomized control trial attempted to offer an answer.

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1.Settings: RCT, single center

2. Patients: 90 adults patients with respiratory failure due to COVID-19

3. Intervention: APRV with maximum allowed high pressure of 30 cm H20, at time of 4 seconds.  Low pressure was always 0 cm H20, and expiratory time (T-low) at 0.4-0.6 seconds. This T-low time can be adjusted upon analysis of flow-time curve at expiration.

4. Comparison: Low tidal volume (LTV)  strategy according to ARDSNet protocol.

5. Outcome: Primary outcome was Ventilator Free Days at 28 days.

6.Study Results:

• Baseline characteristics were similar. At randomization, PF ratio for APRV group = 140 (SD 42) vs. 149 (SD 50) for LTV group.
• Median Ventilator Free Day for APRV group: 3.7 [0-15] days vs. 5.2 [0-19] for LTV group ( P = 0.28)
• APRV group had higher PaO2/FiO2 ratio during first 7 days (mean difference = 26, P<0.001)
• ICU length of stay for APRV group: 9 [7-16] vs. 12 [8-17] days (P = 0.17)
• Severe hypercapnia (Pco2 at ≥ 55 along with a pH < 7.15): APRV group = 19 (42%) vs. LTV = 7 (15%), P = 0.009.
• Death at 28 days: 35 (78%) for APRV group, vs. 27 (60%) for LTV group ( P = 0.07)

7.Discussion:

• Hypercapnea was transient and was mostly due to implementation of the ventilator settings.  The protocol recommended reduction of T-high to allow more ventilation, but most clinicians did not want to shorten the T-High, but instead opted for higher T-low.
• Although the number of barotrauma were similar in both group, all 4 cases of barotrauma in the APRV group occurred within a very short period of time (3 weeks), prompted the safety monitoring board to recommend stopping recruitment for COVID-19 patients.

8.Conclusion:

APRV was not associated with more ventilator free days or other outcomes among patients with COVID-19, when compared to Low Tidal Volume strategies in this small RCT.

 

References

Ibarra-Estrada MÁ, García-Salas Y, Mireles-Cabodevila E, López-Pulgarín JA, Chávez-Peña Q, García-Salcido R, Mijangos-Méndez JC, Aguirre-Avalos G. Use of Airway Pressure Release Ventilation in Patients With Acute Respiratory Failure Due to COVID-19: Results of a Single-Center Randomized Controlled Trial. Crit Care Med. 2022 Apr 1;50(4):586-594. doi: 10.1097/CCM.0000000000005312. PMID: 34593706; PMCID: PMC8923279.