The effect of cooling on PaO2.
The data shown above are from a simulated patient with severe respiratory failure and an oxygen consumption of ~200 ml/min on stable VV ECMO. The patient has been completely paralysed with pancuronium and is ventilated on 100% oxygen with a tidal volume of 400 mls at 10 breaths per minute. The VV ECMO system has been set at a constant blood flow rate of 5.0 lpm and ‘Sweep Gas’ rate of 4.0 lpm. The patient's native cardiac output is about 5 lpm.
Over a period of twenty minutes, the patient has been cooled from 37 to 34 Centigrade. As the temperature (and metabolic rate) falls, note how the PaO2 rises steadily.
This illustrates another important priciple of VV ECMO – that, if oxygenation is marginal and ECMO pump flow is adequate, consideration should be given to cooling the patient.