Calculating oxygen consumption for Hamilton Medical ventilators


Author: Simon Franz

Date of first publication: 30.06.2020

Last change: 07.07.2020

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As at June 2020, many hospitals are housing far more ICU beds than normal. Many may also be using new makes or models of ventilators they are unfamiliar with. In order to work out the total amount of oxygen required under these changed circumstances, it is necessary to know how to calculate the oxygen consumption for a particular ventilator.

Calculating oxygen consumption for Hamilton Medical ventilators

Parameters and calculation

While the basic principle applies to most makes and models, the calculation depends on several parameters that may differ.

To calculate the estimated oxygen consumption for your Hamilton Medical ventilator, you need to take these parameters into account:

  • Fraction of inspired oxygen (%Oxygen)
  • Expiratory minute volume (ExpMinVol) (x2 for patients < 8 kg)
  • Base flow (see table below)
  • In the case of leaks: leak flow (Mvleak)

The calculation is as follows:

(ExpMinVol + Base flow + MVleak) * ((%Oxygen – 20.9) / 79.1)

Note that this calcuation provides you with an estimate only and the actual consumption may be higher.

Tip: HAMILTON-C1/T1/MR1 ventilators offer oxygen consumption as a measured parameter. When activated, the O2 consumption is displayed in the System > Info window.

See the table below for the base flow rates on Hamilton Medical ventilators.

Example of calcuation on HAMILTON-C1

Here you can see a calculation of the estimated oxygen requirement for a HAMILTON-C1 ventilator based on the following parameters:

  • Expiratory minute volume (ExpMinVol): 8 l/min
  • Total minute volume leakage (MVleak): 1 l/min
  • Base flow: 3 l/min
  • Set duration (FiO2): 60%
  • Planned duration of transport: 120 min

O2 consumption (in l/min): (8.0 l/min + 3.0 l/min + 1.0 l/min) * (60.0 – 20.9) / 79.1 = 5.93 l/min

Total oxygen requirement (in liters) for 120 minutes: 5.93 l/min * 120 = 711.6 liters

Therefore, the estimated oxygen consumption for the planned transport duration of 2 hours is approximately 712 liters.

Patient group




Adult / pediatric

3 l/min

6 l/min

Flow trigger setting ≤ 2 l/min: 4 l/min 
Flow trigger setting > 2 l/min: 2*Flow trigger  
IntelliSync+: variable
Range: 2 to 30 l/min


4 l/min

6 l/min

Flow trigger setting ≤ 1 l/min: 2 l/min
Flow trigger setting > 1 l/min: 2*Flow trigger (max. 6 l/min)
Range: 2 to 6 l/min


Not applicable

Not applicable

Pressure trigger or trigger off: 1 l/min