Explain fixed performance system in oxygen therapy?
Fixed Performance Systems: These devices are capable of delivering a fixed, preset concentration of oxygen regardless of the breathing pattern. Venturi masks are of this type - oxygen flows into the mask as a jet, resulting in entrainment of air through holes at the bottom of the mask (venture effect). The FiO2 would depend on the oxygen flow and amount of air entrained. Precise FiO2 like 24 per cent, 28 per cent, 35 per cent and 40 per cent can be achieved. These masks are used for controlled oxygen therapy like in acute exacerbation of COPD.
Thus, the key points in oxygen therapy are:
1) Give oxygen to the patient with hypoxia. Give as much as you can at first, and then reduce it, guided by blood gas measurements/pulse oximetry
2) Oxygen treatment will work only if the patient has a patent airway and is breathing - if not, he requires intubation and mechanical ventilation
3) The underlying cause for the hypoxia must be identified and addressed. Giving oxygen buys time while you do this