A 64 year old lady admitted with G~de V subarachnoid hemorrhage was pronounced brain dead based on a 4 vessel cerebral angiogram. Subsequent to the angiogram, the total respiratory rate was 15/min when the ventilator rate was set at 10/min.
What are the potential causes of the discrepancy between the set ventilator
rate and the total respiratory rate?
What steps will you take to distinguish the cause in this case?
What are the potential causes of the discrepancy between the set ventilator rate and the total respiratory rate?
1) Auto-triggering of the. ventilator due to
- cardiogenic oscillations
- High sensitivity settings
- Circuit leaks
- Water condensation in the circuit
2) True spontaneous breath (although unlikely as there is a definitive test indicating brain death.
b) What steps will you take to distinguish the cause in this case?
1) Connect the patient to aT -piece circuit with a capnograph and look for
spontaneous breathing movements and a C02 waveform.
So, why is this braindead woman seemingly making spontaneous breathing efforts?
Note that the college does not rule out true spontaneous breaths.
- Cardiac oscillation
- Inappropriately sensitive trigger
- Condensation pooling in the circuit
- leaky circuit
- Triggering by something other than the patient's brain:
- Diaphragmatic "capture" of her pacemaker
- External movements (eg. nursing care)
One excludes the embarrassing possibility of a breathing braindead patient by connecting her to a T-piece or by adjusting the trigger to a less sensitive setting.