Bests & Worsts Reviews from Amazon

I am a medical doctor, and wore this mask while using an FDA certified pulse oximeter to validate the manufacturer's claim. The mask in fact INCREASED my O2 saturation (SpO2) since its create was is called PEEP (positive end expiratory pressure) thus keeping my alveoli open at the end of an exhalation. I suppose that at the highest setting, it could eventually decrease SpO2 (O2%) since one gets tired and one can't breath anymore. But at the highest setting, I was never able to decrease my SpO2 since I just worked harder at inspiring air and expiring air. No evidence either of increasing EtCO2 with a capnograph (device use to measure CO2). The manufacturer claims it increases your CO2. Again, if you tire yourself out, this will probably be the case, but you can achieve this no differently by simply holding your breath. On the positive side, the mask has a superb fit and seal, something we appreciate in the medical world.