Mechanical ventilation for SARS The basics Charles Gomersall Dept of Anaesthesia & Intensive Care The Chinese University of Hong Kong Prince of Wales Hospital Version 1.0 April 2003
Jan 15, 2016
Mechanical ventilation for SARSThe basics
Charles GomersallDept of Anaesthesia & Intensive CareThe Chinese University of Hong Kong
Prince of Wales Hospital
Version 1.0April 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
Inflates and deflates
normally
Inflates and deflates
normally
Inflates and deflates
normally
Inflates and deflates
normally
Inflates and deflates
normally
Inflates and deflates
normally
Hyperinflates
Hyperinflates
Hyperinflates
Hyperinflates
Hyperinflates
Hyperinflates
Hyperinflates
Tidal opening and collapse
Tidal opening and collapse
Tidal opening and collapse
Tidal opening and collapse
Tidal opening and collapse
Tidal opening and collapse
Tidal opening and collapse
Collapsed
Collapsed
Collapsed
Collapsed
Collapsed
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
Volume controlPRVCPressure 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
Volume control
• PEEPi
– Aim for <2 cmH2O– ie PEEPtotal – PEEPe <2
Click here to continue
Volume control
• Pplat
– Aim for 25-30 cmH2O• <25: VT up to 6 ml/kg• 25-30: VT up to 7-8 ml/kg and
respiratory rate if PEEPi increased due to rapid respiratory rate
• >30: VT to minimum of 4 ml/kg
Click here to continue
Volume control
• Aim for pH>7.3– 7.15-7.3:
set respiratory rate until– Rate=35 bpm or– pH=7.3 or
– PaCO2<3.25
• If RR=35 and pH<7.3 NaHCO3 may be given.
Click here to continue
Volume control
– <7.15: set RR to 35
• If RR=35 and pH<7.15 and NaHCO3 has been considered, VT may be in 1 ml/kg steps until pH>7.15 (Pplat target may be exceeded)
Click here to continue
Volume control
– >7.45 set respiratory rate until patient RR>set
RR (do not decrease set RR below 6 bpm)
Click here to return to the modes menu
Pressure control
• Measure patient’s height and calculate PBW
• Set PEEP 6-12 cmH2O, I:E =1:2• Start with pressure control level that
results in VT=8 ml/kg PBW • At 1-2 hour intervals pressure to VT by
1 ml/kg to a minimum of 4 ml/kg– Maintain 4-6 ml/kg
• Every 4h and after each change measure airway pressure, PEEPi, and pH
Click here to continue
Pressure control
• PEEPi
– Aim for <2 cmH2O– ie PEEPtotal – PEEPe <2
Click here to continue
Pressure control
• PAW and VT
– Aim for 25-30 cmH2O and VT 4-6 ml/kg• <25 and VT <6 ml/kg: pressure to VT
up to 6 ml/kg• 25-30: pressure to VT up to 7-8 ml/kg
and respiratory rate if PEEPi increased due to rapid respiratory rate
• >30 or VT >6 ml/kg: pressure (do not allow VT to fall below 4 ml/kg)
Click here to continue
Pressure control
• Aim for pH>7.3– 7.15-7.3:
set respiratory rate until– Rate=35 bpm or– pH=7.3 or
– PaCO2<3.25
• If RR=35 and pH<7.3 NaHCO3 may be given.
Click here to continue
Pressure control
– <7.15: set RR to 35
• If RR=35 and pH<7.15 and NaHCO3 has been considered, pressure may be to VT in 1 ml/kg steps until pH>7.15 (PAW
target may be exceeded)
Click here to continue
Pressure control
– >7.45 set respiratory rate until patient RR>set
RR (do not decrease set RR below 6 bpm)
Click here to return to the modes menu
Pressure regulated volume control• Measure patient’s height and calculate
PBW• Set PEEP 6-12 cmH2O• Set upper pressure alarm limit=35• 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 PAW, PEEPi, and pH
Click here to continue
Pressure regulated volume control• PEEPi
– Aim for <2 cmH2O– ie PEEPtotal – PEEPe <2
Click here to continue
Pressure regulated volume control• Recurrent “Limited pressure
breath” or high airway pressure alarm VT to minimum of 4 ml/kg
Click here to continue
Pressure regulated volume control• PAW
– Aim for 25-30 cmH2O• <25: VT up to 6 ml/kg• 25-30: VT up to 7-8 ml/kg and
respiratory rate if PEEPi increased due to rapid respiratory rate
Click here to continue
Pressure regulated volume control• Aim for pH>7.3
– 7.15-7.3: set respiratory rate until
– Rate=35 bpm or– pH=7.3 or
– PaCO2<3.25
• If RR=35 and pH<7.3 NaHCO3 may be given.
Click here to continue
Pressure regulated volume control
– <7.15: set RR to 35
• If RR=35 and pH<7.15 and NaHCO3 has been considered, VT may be in 1 ml/kg steps until pH>7.15 (Upper pressure limit may be increased and PAW target may be exceeded)
Click here to continue
Pressure regulated volume control
– >7.45 set respiratory rate until patient RR>set
RR (do not decrease set RR below 6 bpm)
Click here to return to the modes menu
Prone ventilation
Mediastinum
Consolidated lung
ventilation, perfusion
ventilation, perfusion
Prone ventilation
• In prone position:– ventilation now
preferentially goes to dorsal region
– recruitment of alveoli
– alveoli in ventral regions remain open because of PEEP
Prone ventilation
• Improved VQ matching– ventilation to
dorsal region improved
– perfusion continues to go preferentially to dorsal region
Prone ventilation
• On return to supine position:– alveoli in dorsal
regions may remain open because of PEEP resulting in a persistent response
Complications
• Accidental extubation• Others:
– pressure effects on skin and eyes– disconnection of intravenous lines– haemodynamic instability
Practical aspects
• Consider for patients requiring more than 50% oxygen
• Turn prone and leave prone until for a minimum of a few hours
• Pillows under chest, abdomen and pelvis. Head support
Practical aspects
• If a responder turn back to supine once a day– Nursing care– Examination– Change lines– Persistence of response
• If not a responder try removing pillow from under abdomen
Practical aspects
• Do not disconnect from ventilator• Care with ETT and lines• Check pressure points including
eyes• Heavy sedation ± paralysis
Key points
• Minimize further lung damage– Minimize FIO2
– Low tidal volumes and inspiratory pressures titrated against pH
– Consider prone ventilation