To the Editor
Regulations in some countries, such as ours (FRG), mandate the monitoring of inspiratory oxygen concentration (F’02) in the anesthesia breathing system (A.B.S). In my opinion, pulse oximetry (P.O.) adds more to patient safety than F102-monitoring ever could; therefore, I would like to ask two questions:
1. Would it diminish patient safety if, instead of also monitoring F102, arterial oxygen saturation alone were monitored by P.O.? Or would that even enhance patient safety, especially when using an 02/N20-mixer Which provides, under optical control via flowmeters, at least 21 volume percent 02 under all conditions? (1)
2. If, never the less, the monitoring of oxygen concentration in the A.B.S. is considered essential in spite of P.O., why in the inspiratory and not in the expiratory limb (at least in circle systems)? In my experience monitoring FE02, instead of F102, gives more information, e.g. on the effect of preoxygenation or indirectly on N20-washout at the end of anesthesia and is not less safe.
My first question has a financial background. Actually we, according to regulations, must buy a FIO2-monitor for every anesthesia machine. Due to this, our budget does not allow us to buy enough pulse oximeters. With respect to the fact that the sensors in the oxygen monitors used in our institution need replacing roughly once a year, oxygen monitors are nearly as expensive as P.O., but in my opinion, less useful. I would prefer to spend the money on P.O. Is this, from a scientific/practical point of view, reasonable? (I do not expect legal consequences to be considered).
I would appreciate very much if a discussion on these questions could take place.
Klinikum Steglitz der FU Berlin Federal Republic of Germany
- Heath, J.R., Anderson, M.M., Nunn, J.F. Performance of quantiflex monitored dial mixer. Br. 1. Anaesth. 1973; 45:216