Important ventilatory figures (adult)

  • Tidal volume (VT) ~ 7ml/kg (= 500ml)
  • Respiratory rate (RR) ~ 15
  • Minute volume (MV)  ~ 7.5L/min
  • I:E ratio ~ 1:1.5
  • Physiological PEEP 5cm H2O
  • pCO2 40 mmHg
  • pO2 100 mmHg
  • FiO 21% (air) [pAO2 = 150mmHg at atmospheric pressure]
  • End Tidal CO2 (ETCO2) 35mmHg
  • Peak airway pressure 50mmHg (recommended max)
  • Mean airway pressure 35mmHg (recommended max)
  • PEEP 15 cm H2O (recommended max)

See Ventilation strategy for asthma

See Principles of mechanical ventilation

This is a practical description of using the Oxylog 2000

Setting up

  • The oxylog requires a power supply, either via main source or by rechargeable battery (unlike the old model oxylog which was gas powered)

  • An oxygen supply can be delivered via wall source or by portable cyclinder (note that the small C cylinder only allows for short transport < 15min before being exhausted)

  • The tubing should be attached with in-line filter +/- ETCO2 monitor

Initial settings

  • Set the oxygen concentration to No Air Mix (There are only two settings - No Air Mix = 100% O2  and Air/Mix = 60% O2)

  • Set the tidal volume to about 10ml/kg (700ml in a 70kg male)

  • Set rate (frequency) to 12 breaths/minute

  • Set PEEP at 5 cmH2O

  • Set I:E ratio to 1:1.5

  • Set mode to SIMV/CPAP

  • Turn the ventilator switch I/O to on

  • Attach the patient to the ventilator and ensure that they are being ventilated, this can be assessed clinically or (if attached) by the ETCO2 waveform


  • Immediately check peak airway pressures (this is the analog dial on the left hand side) and treat causes of high or low pressures (see Volume/Pressure alarms)
  • Review alarms (on digital screen) which monitors tidal volumes, airway pressures and disconnections and address problems as they occur
  • Ensure that SaO2 is being maintained and send for ABG after 10min
  • Monitor BP regularly
  • Sedate and/or paralyse patient appropriately

Addressing problems


High Peak airway pressures > 40cmH2O

    see Volume/Pressure alarms

  • If no cause is found then reduce the tidal volume slowly until pressures are acceptable but that SaO2 continues to be maintained

Low airway pressure

    see Volume/Pressure alarms

  • Quickly check for disconnections
  • If no disconnection identified remove ventilator and hand ventilate
  • Exclude cuff leak
  • Check breath sounds to exclude oesophageal intubation - 'if in doubt, take it out'


  • Exclude pneumothorax as a cause
  • Treat other causes such as hypovolaemia, sepsis, anaphylaxis
  • If no cause is found reduce tidal volumes or PEEP until pressure improves but only if SaO2 can be maintained

Adjusting the ventilator

    Intially aim for pCO2 40mmHg and pO2 100mgHg

pO2 too high

  • Reduce FiO2 to Air Mix

pO2 too low

  • Give 100% FiO2
  • Exclude problems such as pneumothorax
  • Ensure adequate tidal volumes are being delivered (10-15ml/kg)
  • Increase PEEP gradually to achieve adequate oxygenation to a maximum of 15cmH2O

        pCO2 too high

  • Increase rate


  • Increase tidal volume (this may increase peak pressures AND/OR pO2 as well)

pCO2 too low

  • Decrease rate


  • Decrease tidal volume (this may decrease peak pressures AND/OR pO2 as well)
Disclaimer: Note: The information described here relates solely to operational matters in the Emergency Department.  Every effort has been made to verify the accuracy of the content. However, neither the author or the hospital will take responsibility for errors resulting from its use.  Please refer to your own departmental guidelines and verify all clinical decisions with a reliable source.  

Date Last Reviewed: 05/08/2004