Mechanical ventilation for SARS The basics

Mechanical ventilation for SARSThe basics Charles GomersallDept of Anaesthesia & Intensive CareThe Chinese University of Hong KongPrince of Wales Hospital Version 1.0 April 2003

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Disclaimer • Although considerable care has been taken in the preparation of this tutorial, the author, the Prince of Wales Hospital and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from its use.

The problem • Heterogenous involvement of lung • Normal compliance •  compliance • Overall:  compliance

Inflates and deflates normally

Hyperinflates Inflates and deflates normally

Hyperinflates

Hyperinflates Tidal opening and collapse

Tidal opening and collapse

Collapsed

The problem • Hyperinflated  risk of volutrauma • Recurrent opening and collapse  risk of shear injury • Some alveoli persistently collapsed  shunting

The problem • Heterogenous involvement of lung • Normal compliance •  compliance • High risk of “barotrauma”

Barotrauma & volutrauma • Unrestricted lungs • Pulmonary oedema at PAW of 45 cmH2O • Restricted lungs • No pulmonary oedema at same pressures

The problem • Heterogenous involvement of lung • Normal compliance •  compliance • High risk of barotrauma • Large shunt • High oxygen requirement • Risk of oxygen toxicity

Principles • Minimize FIO2 • SpO2 88-94%

Principles • Minimize FIO2 • Low tidal volume and low inspiratory pressure • Start with 8ml/kg PBW and work down to 4-6 ml/kg

Principles • Minimize FIO2 • Low tidal volume and low inspiratory pressure • Start with 8ml/kg PBW and work down to 4-6 ml/kg • Increase respiratory rate to maintain minute ventilation • Check for intrinsic PEEP

Principles • Minimize FIO2 • Low tidal volume and low inspiratory pressure • Start with 8ml/kg PBW and work down to 4-6 ml/kg • Increase respiratory rate to maintain minute ventilation • Check for intrinsic PEEP • Allow PaCO2 to rise • Keep pH>7.3 if possible

Principles • Minimize FIO2 • Low tidal volume and low inspiratory pressure • Start with 8ml/kg PBW and work down to 4-6 ml/kg • Increase respiratory rate to maintain minute ventilation • Check for intrinsic PEEP • Allow PaCO2 to rise • Keep pH>7.3 if possible • Sedation ± paralysis

Practice • Start with FIO2=1.0 • Choose the mode that you and the other staff in your ICU are most familiar with Pressure control PRVC Volume control Before selecting a mode of ventilation download and printthe relevant algorithm for ventilating SARS patients Download

Volume control • Measure patient’s height and calculate PBW • Set PEEP 6-12 cmH2O, I:E=1:2 • Start with VT=8 ml/kg PBW • At 1-2 hour intervals decrease VT by 1 ml/kg to a minimum of 4 ml/kg • Maintain 4-6 ml/kg • Every 4h and after each change measure Pplat, PEEPi, and pH Click here to continue

Mechanical ventilation for SARS The basics