ARDSnet Ventilation Strategy

OVERVIEW

The ARDSNet ARMA study is one of the pivotal clinical trials in critical care and established the current standard of care for mechanical ventilation

• key study underpinning the protective lung ventilation approach, which has since been extended to the safe ventilation of non-ARDS patients
• provides a sliding scale approach to the optimisation of FiO2 and PEEP, based on oxygenation (though the optimisation of PEEP is controversial)
• ARDSnet Ventilation Strategy is practical and can be used at the bedside
• Open lung approaches to ventilation typically use higher PEEP settings than the ARDSnet Ventilation Strategy

DEFINITIONS

Note that the definitions of ALI and ARDS have been revised – however they are included here as they were used in the ARDSNet trial. See ARDS Definitions.

Acute lung injury (ALI)

• acute onset
• PaO2/FiO2 ratio < 300
• bilateral infiltrates consistent with pulmonary oedema
• no evidence of LA hypertension

Acute Respiratory Distress Syndrome (ARDS)

• acute onset
• PaO2/FiO2 ratio < 200
• bilateral infiltrates consistent with pulmonary oedema
• no evidence of LA hypertension

Protective lung ventilation

• synonymous with low tidal volume (TV) ventilation (4-8 mL/kg) and maintaining plateau pressures (Pplat) <30 cmH20, and often includes permissive hypercapnia
• 6 mL/kg PBW (predicted body weight, not actual body weight) is most commonly quoted as this was used in the intervention arm of the practice defining ARDSNet ARMA trial and is physiologically normal for a healthy person

Predicted body weight (PBW)

• PBW (using kg and cm) is calculated using the Devine formula as follows:
  • Adult male: 50 + 0.91 (Height cm −152.4)
  • Adult female: 45 + 0.91 (Height cm −152.4)
• ARDSNet use the term “predicted” body weight, but this is the same as ideal body weight (IBW) calculated using the Devine formula, available at MDCalc.
• ARDsNet also published tidal volume tables for different heights and PBWs, for both male and female patients.

ARDSNet VENTILATION STRATEGY

Ventilator Setup and Adjustment

• calculate predicted body weight (PBW)
• select any ventilator mode
• achieve a TV of 6mL/kg
• set respiratory rate (RR) to maintain optimal minute ventilation (MV) (not RR > 35/min)
• aim for SpO2 88-95% or PaO2 55-80mmHg
• increase PEEP with increasing FiO2 (5-24 cmH2O) according to a sliding scale (see table below)
• aim for plateau pressure (Pplat) <30cmH2O
  • if necessary decrease TV stepwise by 1 mL/kg PBW to a minimum of 4 mL/kg PBW
  • If Pplat < 25 cmH20, increase TV stepwise by 1 mL/kg PBW until Pplat >25 cmH20 or TV of 6 mL/kg PBW
  • Pplat >30 cmH20 allowed if TV 4 mL/kg IBW and pH <7.15
  • TV could be increased up to 8 mL/kg PBW for patients with severe dyspnoea if Pplat maintained <30 cmH20
• pH goal = 7.30-7.45
  • if pH < 7.15 increase TV, give NaHCO3

Paired FiO2 and PEEP settings

FiO2	PEEP (cmH20)
0.3	5
0.4	5
0.4	8
0.5	8
0.5	10
0.6	10
0.7	10
0.7	12
0.7	14
0.8	14
0.9	14
0.9	16
0.9	18
1.0	18
1.0	20
1.0	22
1.0	24

Weaning

• criteria for weaning:
  • FiO2 < 0.40
  • PEEP < 8 cmH20
  • patient has acceptable breathing efforts
  • SBP > 90 mmHg without pressors
• if criteria met conduct a Spontaneous Breathing Trial:
  • T-piece, trache collar or pressure support of <5/5 cmH20
  • -aim for 120 minutes
  • -assess for failure
    • HR > 120%
    • Accessory muscle use
    • Abdominal paradox
    • Sweating
    • Marked dyspnoea

References and Links

Journal articles

• ARDSNet. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. The Acute Respiratory Distress Syndrome Network. N Engl J Med. 2000 May 4;342(18):1301-8. [pubmed]