The ventilatory response to hypoxia.
The patient's ventilatory response to hypoxia is shown in this graph. The red line represents the virtual patient's minute ventilation (correlated with PaO2) when the supervisor administers a hypoxic mixture. The response has been superimposed on the actual data of Weil et al who examined the ventilatory response to hypoxia in a group of 10 normal volunteers.
When you are using the simulator, it is important to understand that if you make the patient hypoxic, this type of reaction will occur (unless you have depressed the response in some way). Broadly speaking, there are three ways in which you can suppress this behaviour:
- Administer a muscle relaxant (eg Pancuronium).
- Administer a respiratory depressant (eg Fentanyl).
- Ask the Supervisor to impair the patient's ventilatory responses.
In many of the tutorials, you will often be asked to paralyse and ventilate the patient. - This is done in order to make it easier to assess the impact of the ECMO technique under study without having also to consider the effect of a change in intrinsic respiratory behaviour.
Hypoxic ventilatory drive in normal man. Weil JV, et al. J Clin Invest. 1970 Jun;49(6):1061-72.