I was trying to understand why I recorded a blood oxygen saturation levels of 99% after just smoking several cigarettes. This test was done using a finger stall. Carbon monoxide binding should have made my oxygen saturation as low as 70% (but at that level, I would need a higher oxygen flow, hence a higher pulse rate and blood pressure in smokers). The normal long term binding is supposed to be about 10% in heavy smokers, and takes weeks after heavy smoking stops to reduce the CO saturation (the red blood cells have to die).
The problem is multifold.
Arterial blood gas analysis machines measure oxygen saturation by using complex calculations based on a number of separate reactions, creating a selection of products whose concentrations are used to interpret the readings obtained. Specifically, large levels of carbon monoxide can skew the results which then need a different interpretation. But a reading of other results obtained simultaneously will indicate that the oxygen saturation results are unreliable. It is better if the analysis is done with the operator already knowing that the blood sample comes from a smoker.
Pulse oximetry use the frequency of light transmitted by the sample. High carbon monoxide levels can skew the results, since oxygen saturation is actually measured as a result of the combination of different results, both of which are affected by CO saturation.
While I was a patient at Bankstown Hospital early in 2007, no account was taken of any possible skewing of my test results, in spite of knowledge that I had been (I was in a coma, and could not smoke anyway) a heavy smoker. No account was taken of the results provided by the blood gas analysis that cast strong doubts on the reliability of the measured oxygen saturation levels.
No test was done on my CO levels, and no venous blood gas analysis was done.
Basically the medical staff saw what they thought they should see, and not what was actually measured.
They were obviously comforted by the fact that the separate monitoring of my blood oxygen saturation via a finger stall also showed a 95% oxygen saturation. But this is a simpler measurement, easily confused. Blood with carbon monoxide saturation actually comes out a brighter red, and when mixed with oxygen-saturated blood, inflates the measured oxygen saturation levels.
Unfortunately, the correct interpretation of these results is beyond the competence of even the most highly qualified nurses in public hopsitals. The doctors, who believe that since they can occasionally revive patients who are technically dead, and therefore obviously must have some god-like attributes, are actually worse. Talking to a doctor about a medical issue is like being the customer in the Monty Python dead parrot sketch!
It is no wonder why I, but one of many, suffered severe oxygen stress while in a coma. I can be thankful that the attempts to reduce my blood pressure failed, because if it had been reduced, the oxygen stress would have increased my neural atrophy to the point where I would have not revived.
The alternative view is that if I had died permanently, or been so neurologically challenged that I would be in a home, then I wouldn't have to put up with Banktown Hospital's view that I should stop beiong crippled by them and be thankful I am still alive.