100% inspired oxygen from a Hudson mask-a realistic goal?
BACKGROUND
The administration of oxygen at a high-inspired concentration is often required in medicine, particularly in resuscitation of critically ill patients. However, there is a lack of evidence-based guidance on how to achieve this using currently available apparatus. The aim of this study was to assess how maximum inspired oxygen concentrations can be delivered using existing equipment.


METHODS
Ten healthy female volunteers breathed oxygen through two types of Hudson non-rebreathing mask with reservoir bag, one with a safety vent in the mask body and the other with a valve replacing this safety vent (3-valve mask). Oxygen flow was adjusted to either 10 or 15 l min(-1) and the masks were fitted to the face either loosely or tightly. The expired oxygen concentration was measured using an oxygen analyzer.


RESULTS
By using the Hudson non-rebreathing mask with three valves, increasing the oxygen flow to 15 l min(-1), and fitting the mask tightly to the face the average expired oxygen fraction could be raised to 0.85. This equates to an average inspired oxygen fraction of 0.97 in these subjects.


CONCLUSIONS
The three simple measures mentioned above result in a significant improvement in the performance of the Hudson non-rebreathing mask. Together they allow the delivery of an inspired oxygen concentration close to maximum.
Boumphrey
S M
SM
Department of Anaesthesia, Derriford Hospital, PL6 8DH, Plymouth, UK.
Morris
E A J
EA
Kinsella
S M
SM
D000328:Adult; D000704:Analysis of Variance; D015331:Cohort Studies; D004867:Equipment Design; D004869:Equipment Safety; D005260:Female; D006801:Humans; D017214:Laryngeal Masks; D008875:Middle Aged; D010100:Oxygen / Q000008:administration & dosage*; D010102:Oxygen Inhalation Therapy; D011336:Probability; D012016:Reference Values; D012121:Respiration, Artificial / Q000295:instrumentation* / Q000379:methods; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics / Q000502:physiology; D018570:Risk Assessment; D012680:Sensitivity and Specificity
D010100:Oxygen