Last week was a good week. Wednesday several of us flew to Winnipeg in one of Transport Canada’s C550s to do a day of AeroMedical Training on Thursday, at the Canadian Forces School of Survival and AeroMedical Training (CFSSAT). The highlight, and the whole reason we went, were the hypoxia demonstrations in the pressure chamber. We do quite a bit of flying in pressurized aircraft at high altitude, and there is always a risk of a loss of cabin pressure. Thus it is very smart to be familiar with your personal hypoxia symptoms, to increase the odds that you will recognize the situation and don the oxygen mask before it is too late.

In the past, the hypoxia demos were done at 25,000 ft or 43,000 ft cabin altitude in the pressure chamber. Large vacuum pumps reduce the pressure in the pressure chamber to produce a cabin pressure that is equivalent to the low pressure found at altitude. The human body is not designed for such low pressures, and there is a real risk of decompression sickness at 25,000 ft and above if this altitude is reached quickly, caused by nitrogen coming out of solution and forming bubbles in the body. CFSSAT has changed their training protocol since I was there last - now the hypoxia demos are done at 10,000 ft cabin altitude, with the training wearing a mask and breathing a gas mix which is 10% oxygen and 90% nitrogen, vs the normal 21% oxygen, 78% nitrogen and 1% other gasses. The combination of higher altitude and lower oxygen percentage is equivalent to 25,000 ft. This new protocol is much easier on the body.

I learned that my hypoxia symptoms have changed slightly as I aged. In the past, the first sign was always a tingling sensation on the back of my palms, followed by a feeling of confusion as the brain started to be starved of oxygen. We each did two hypoxia events on Thursday, and in both cases the first noticeable symptom was confusion - no tingling of the hands either time.

Friday we flew home. Only two of us were qualified on the C550, so I was up front on both Wednesday and Thursday.

Saturday morning I did a short flight in the RV–8 to warm up the engine, then I pulled the cowlings to check the cylinder compression, check the ignition timing, etc, as part of the annual inspection. No major issues were noted.