ARDSnet (ARMA) - Ventilation with Lower Tidal Volumes as Compared with Traditional Tidal Volumes for Acute Lung Injury and the Acute Respiratory Distress Syndrome

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Brower RG, et al. "Ventilation With Lower Tidal Volumes As Compared With Traditional Tidal Volumes For Acute Lung Injury And The Acute Respiratory Distress Syndrome". The New England Journal of Medicine. 2000. 342(18):1301-1308.

Link to Article: https://www.nejm.org/doi/full/10.1056/NEJM200005043421801

Clinical Question

In patients with ALI/ARDS receiving mechanical ventilation, how does a lung protective strategy using lower tidal volumes compare with traditional ventilation protocols in decreasing mortality and ventilator-free days?

  • Type of Trial: RCT, 2×2 study combined with ketoconazole treatment (published separately)

    • Ketoconazole arm of study was later stopped due to inability to show efficacy ; name changed from KARMA to ARMA

  • Blinding: Single; clinicians were aware of the allocation arm

  • Setting: 10 university affiliated ARDSnet centers in the USA from March 1996 - March 1999

  • Intention to treat analysis: yes

PICO

  • Population:

    • 861 patients >18 years old receiving mechanical ventilation with a dx of ARDS/ALI <36h prior to enrollment as defined as acute decrease in P/F</= 300, bilateral pulmonary infiltrates on CXR, PCWP</= 18 mmHg without evidence of L atrial hypertension

      • Excluded:

        • pregnancy; neuropathies; chronic lung disease; severe burns

  • Intervention:

    • Low tidal volume ventilation with protocol for limiting plateau pressures and respiratory acidaemia

      • Volume-assist-control ventilation with 6 ml/kg/breath (ideal body weight)

      • Plateau pressure < 30 cm water

  • Control:

    • Traditional, higher, tidal volume ventilation with similar protocol

      • Volume-assist-control ventilation with 12ml/kg/breath (ideal body weight)

      • Plateau pressure < 50 cm water

  • Outcome:

    • 1st Primary outcome: reduced mortality favoured lower volume ventilation

      • 39.8% vs 31.0% (p=0.007)

    • 2nd Primary outcome: increased ventilator-free days favoured lower volume ventilation

      • 12+/-11 days vs 10 +/-11 days (p=0.007)

Conclusions

Lower-tidal-volume protocol should be used in patients with acute lung injury and the acute respiratory distress syndrome.

Strengths

  • Well designed methodology for the clinical question

  • Adequately powered to detect small difference in primary outcome

Weaknesses

  • As a group sequential clinical trial, it will statistically favour a positive outcome.

  • Only single-blinded: clinician aware of allocation, but no apparent difference in care provided with exception of PEEP level.

  • The small between group difference in PEEP level may favour the intervention group.

Take Note

  • Patients with ARDS should be ventilated with tidal volumes of 6 cc/kg

Sources:

https://www.thebottomline.org.uk

Rachel MulderComment