Grade A Recommendation
Low tidal volume ventilation in ARDs.
This review may be edited
Author info
Posted By: Gordon S. Doig
E-Mail: gdoig@med.usyd.edu.au
Posted Date: 10 June, 2004
Title: Low tidal volume ventilation in ARDs.
PubMed Resource Link: Click here to repeat the Medline search used to develop this EBR.
 
Evidence-based Recommendation
Best level of evidence
Well conducted Level I RCT.
Target Population
Mechanically ventilated patients with:
  • an acute decrease in the PaO2 / FiO2 ratio to 300 or less
  • bilateral pulmonary infiltrates on chest x-ray consistent with the presence of edema and
  • no clinical evidence of left atrial hypertension (if measured, a PaOP < 18mmHg)
  • Purpose
    To reduce hospital discharge mortality by 8.7% (absolute).
    Exclusion criteria
    Clinical judgement should be exercised in order to decide whether it is reasonable to expect that the following patient groups would benefit from this strategy:
  • Neuromuscular disease that impairs the ability to ventilate spontaneously, such as C5 or higher spinal cord injury, amyotrophic lateral sclerosis, Guillain-Barre syndrome and myasthenia gravis.
  • Increased intracranial pressure, tricyclic antidepressant overdose, Hgb SS, HgbSC or other conditions where hypercapnia would be contraindicated.
  • Severe chronic respiratory disease.
  • Morbid obesity.
  • Burns > 30% BSA, bone marrow transplant, lung transplant or severe chronic liver disease (Child-Pugh Score of 10-15).
  • Recommendation
    6 ML/KG Tidal Volume Ventilation Strategy Synopsis

    INITIAL VENTILATOR TIDAL VOLUME AND RATE ADJUSTMENTS

    1. Calculate predicted body weight (PBW)
      • Male= 50 + 2.3 [height (inches) - 60] or 50 + 0.91 [height (cm) - 152.4]
      • Female= 45.5 + 2.3 [height (inches) - 60] or 45.5 + 0.91 [height (cm) - 152.4]
    2. Mode: Volume Assist-Control
      1. Set initial tidal volume to 8 ml/kg PBW
      2. Reduce tidal volume to 7 ml/kg after 1-2 hours and then to 6 ml/kg PBW after 1-2 hours
      3. Set initial ventilator rate to maintain baseline minute ventilation (not > 35 bpm)

    SUBSEQUENT TIDAL VOLUME ADJUSTMENTS

    Plateau Pressure Goal: ≤ 30 cmH2O

    Check inspiratory plateau pressure (Pplat) with 0.5 second inspiratory pause at least every four hours and after each change in PEEP or tidal volume.

    • If Pplat > 30 cmH2O, decrease tidal volume by 1 ml/kg PBW steps to 5 or if necessary to 4 ml/kg PBW.
    • If Pplat < 25 cmH2O and tidal volume < 6 ml/kg, increase tidal volume by 1 ml/kg PBW until Pplat > 25 cmH2O or tidal volume = 6 ml/kg.
    • If breath stacking or severe dyspnea occurs, tidal volume may be increased (not required) to 7 or 8 ml/kg PBW if Pplat remains ≤ 30 cmH2O.

    ARTERIAL OXYGENATION

    GOAL: PaO2 55-80 mm Hg or SpO2 88-95%

    Use these FiO2/PEEP combinations to achieve oxygenation goal.

    FiO2 0.3 0.4 0.4 0.5 0.5 0.6 0.7 0.7 0.7 0.8 0.9 0.9 0.9 1.0
    PEEP 5 5 8 8 10 10 10 12 14 14 14 16 18 20-24

    RESPIRATORY RATE (RR) AND ARTERIAL pH
    ARTERIAL pH GOAL: 7.30-7.45

    1. Acidosis Management:
      • If pH 7.15-7.30:
        • Increase set RR until pH > 7.30 or PaCO2 < 25 (Maximum Set RR =35)
        • If set RR = 35 and pH < 7.30, NaHCO3 may be given (not required)
      • If pH < 7.15:
        • Increase set RR to 35.
        • If set RR = 35 and pH < 7.15 and NaHCO3 has been considered, tidal volume may be increased in 1 ml/kg PBW steps until pH > 7.15 (Pplat target may be exceeded).
    2. Alkalosis Management: (pH > 7.45):
      • Decrease set RR until patient RR > set RR.

        Minimum set RR = 6/min.
    3. I:E RATIO

      GOAL: 1:1.0 - 1:3.0
      • Adjust flow rate and inspiratory flow wave-form to achieve goal.
    4. WEANING:
      1. Conduct A CPAP trial daily when:
        1. FiO2 ≤ 0.40 and PEEP ≤ 8, and
        2. PEEP and FiO2 ≤ values of previous day, and
        3. Patient has spontaneous breathing efforts (may decrease vent set rate by 50% for 5 minutes to detect effort), and
        4. Systolic BP ≥ 90 mm Hg without vasopressor support.
        Conducting the CPAP Trial:
        1. Set: CPAP = 5 cmH2O, FiO2 = 0.50.
        2. If patient RR ≤ 35 for 5 min., advance to Pressure Support Weaning (See below)
        3. If patient RR > 35, return to previous A/C settings and reassess for weaning next morning.
      2. Pressure Support (PS) Weaning Procedure
        1. Set PEEP = 5 and FiO2 = 0.50
        2. Set initial PS based on RR during CPAP trial:
          1. If CPAP RR < 25: set PS = 5 cmH2O and go to REDUCING PS steps 3.3 to 3.4
          2. If CPAP RR = 25-35: set PS = 20 cmH2O, then reduce by 5 cmH2O at ≤ 5 min. intervals until patient RR = 26-35, then go to REDUCING PS step 3.1
          3. If initial PS not tolerated: return to previous A/C settings.
      3. REDUCING PS: (No reductions made after 1700 hrs)
        1. Reduce PS by 5 cmH2O q 1-3 hr.
        2. If PS ≥ 10 cmH2O not tolerated, return to previous A/C settings (If Weaning Tolerance Criteria O.K., resume last tolerated PS level next morning and go to step 3.1).
        3. If PS = 5 cmH2O not tolerated, go to PS = 10 cmH2O. If tolerated, PS of 5 or 10 cmH2O may be used overnight with further attempts at weaning the next morning.
        4. If PS = 5 cmH2O tolerated for ≥ 2 hours, assess for ability to sustain unassisted breathing (See below).
      4. UNASSISTED BREATHING TRIAL
        1. Place on T-piece, trach collar, or CPAP < 5 cmH2O
        2. Assess for tolerance as below for two hours.
        3. If tolerated, consider extubation.
        4. If not tolerated, resume PS 5 cmH2O.

    Definition of Weaning Intolerance

    1. RR > 35 (may exceed 35 ≥ 5 minutes), and
    2. SpO2 < 88% (< 5 minutes at < 88% may be tolerated), and
    3. Respiratory distress (≥ 2 of the following):
      • Pulse > 120% of rate at 6 A.M. > 5 minutes
      • Marked use of accessory muscles
      • Abdominal paradox
      • Diaphoresis
      • Marked complaint of dyspnea

    Definition of Unassisted Breathing Intolerance

    1. RR > 35
    2. SpO2 < 90 % and/or PaO2 < 60 mm Hg, and
    3. Spontaneous tidal volume < 4 ml/kg PBW, and
    4. Respiratory distress (any two of the following):
      • Pulse > 120% of usual rate for > 5 minutes
      • Marked use of accessory muscles
      • Abdominal paradox
      • Diaphoresis
      • Marked complaints of dyspnea

    For complete study protocol, visit: www.ARDSnet.org.
    Potential harm
  • To maintain arterial oxygenation at acceptable levels, there may be higher PEEP and FiO2 requirements in the first few days of treatment with low tidal volumes.
  • Development Information
    Date EBR last updated
    10 June 2004.
    Literature source and search terms
    Medline was searched using the PubMed search engine.
    A specific (narrow) search was conducted using the Therapy Clinical Query. The primary search terms were: 'acute respiratory distress syndrome' and 'mecahnical ventilation'.
    The exact search statement is duplicated in the PubMed Resource link.
    147 abstracts were retrieved.
    Study selection
    Well conducted RCTs adequately powered to detect a difference in clinically meaningful outcomes were sought. Methodologically rigorous reviews of Level II trials were considered.
    1 Level I RCT was retrieved. A recent meta-analysis was reviewed to assess the impact of Level II studies.
    References
  • Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med 2000;342:1301-8 (Level I)
  • Ventilation with lower tidal volumes versus traditional tidal volumes in adults for acute lung injury and acute respiratory distress syndrome. Cochrane Database Syst Rev. 2003;(3):CD003844.(Level I / Level II)

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    Low tidal volume ventilation in ARDs.

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