High Altitude - Practical Limits for SpO2 and Pulse?

I spend about half my work time at 2,500 feet above sea level. The other half of the time I am at 14,000 above sea level. I recently had a lung infection that put me out of altitude work for two months. I've since been cleared for high altitude duty, and was given a prescription for a pulse oximeter. I've been carrying it around ever since.

Yesterday I was working at our 14,000 foot site, so I used the opportunity to make several spot checks. After a fairly strenuous project I took a reading and got a pulse rate of 134bpm and a blood saturation level of 74%. I was able to use pressure breathing to get my blood saturation back into the low 90's range without the use of medicinal oxygen. It took a while to get my pulse down below 100bpm. 90-100bpm is typical for me when resting at altitude.

As soon as I finish typing this I am going to call my doctor to discuss a course of action (e.g. monitoring and logging, limits, etc.) but I wanted to ask here as well: What are the practical limits on pulse rate and blood oxygen saturation when working at altitude? I do have some flexibility in my work schedule to take breaks and if necessary go on oxygen, so this would have immediate application for me.

Thanks,

- TNS