Treatment of hypoxemia with an oxygen enricher

An oxygen enricher (concentrator) was evaluated by performing studies of the inhalation of oxygen and arterial blood gas levels over a period of 30 minutes to 40 hours in ten patients, each with acute or chronic hypoxemia (or both) and in two normal volunteers. One other patient was followed at home up to 2,000 hours. The final concentration of oxygen in the inhaled gas (FI(O₂)) was checked by analysis of oxygen within the oropharynx when using the nasal cannulae and within the mask and in-line when using Venturi masks of oxygen concentrations of 24 to 40%. We demonstrated that oxygen could be supplied dependably via the machine, but only according to specific guidelines. The characteristics of this type of machine, as a result of its flow-dependent ability to concentrate oxygen, are such that: the FI(O₂) within the oropharynx achieved with the nasal cannula encompasses a range of 22 to 44%, depending on the machine's flow rate and the patient's minute ventilation; individually labelled Venturi masks must be used at a specific flow as ascertained by this study, using flows of 2 to 4 L/min for a 24% mask, 4 L/min for a 28% mask, 5 L/min for a 31% mask, 4 L/min for a 35% mask, and 4 L/min for a 40% mask in order to achieve the FI(O₂) as labelled; and arterial blood gas levels should be monitored from time to time because changes may occur (albeit rarely) if the patient's minute ventilation exceeds the volume flow of the Venturi mask.