Up to date, expert answers to frequently asked questions (FAQ) about oxygen supply systems, respiratory care and pulse oximetry written by OCC & collaborators.
Invasive mechanical ventilation
Can all ventilators be used on neonates, children and adults?
No. All ventilators have pre specified limits on the size of patient they can safely support. Manufacturers’ information must always be referenced to determine the recommended patient size as well as the necessary components required for such care. Failure to account for this can result in serious harm.
- Tidal volume limits – The lower limit of patient size is most often determined by the lower limit of tidal volume that the ventilator can accurately deliver. This limit must be referenced from the user’s manual. For example, if the tidal volume lower limit of a ventilator is specified to be 150mL, and you wish to deliver lung protective ventilation (6mL/kg), then the smallest patient that can be supported can way no less than 25kg (150/6=25). Of note, most international standards require delivered tidal volume to be accurate to within +/- 10% of the set value.
- Circuits – The use of ventilators on smaller patients may require smaller circuits (check manufacturer specifications). These circuits have lower compliance, and thus less tidal volume is ‘lost’ to circuit expansion with pressurization. These circuits also have more resistance and less overall weight. Some ventilators will calibrate themselves during self check to account for circuit compliance and ‘compressible volume’ (Note: this calibration only applies during volume control ventilation and cannot be accounted for during pressure control ventilation). Some ventilators are factory calibrated to account for a pre-specified circuit compliance and thus are intended to be used only with certain proprietary circuits. For example, if an adult circuit (compliance 2.5 ml/cmH20) is used on a 10kg child (goal tidal volume 60-80mL), and the ventilator is set to deliver 20 cmH20 inspiratory pressure, then 50mL (2.5 ml/cmH20 x 20 cmH20 = 50mL) of volume can be expected to be ‘lost’ to expansion of the circuit. Depending on the ventilator brand, pre check calibration and mode, this lost volume may not be accounted for and the patient may receive little if any true ventilation.
- Dead Space – special consideration for connectors beyond the patient Wye is always important, but especially essential when managing smaller patients to avoid increasing dead space ventilation.
Below are a few examples of different weight limits for select ventilators:
10 - 20 kg
5 - 25 kg
5 - 23 kg