Hypoxia Inhalation Test (HIT) of Robson et al for Evaluating a Patient with Chronic Lung Disease Prior to Air Travel

Description

The oxygen concentration in a pressurized airplane is less than at sea level. The Hypoxia Inhalation Test (HIT) is used to determine if a patient with chronic lung disease can tolerate the level of hypoxia likely to be encountered. The authors are from Western General Hospital in Edinburgh.

Commercial airlines have a cabin pressure comparable to the altitude at 8,000 feet (2,438 meters). At this altitude the FIO2 is 15.1% (approximately 14.4 kPa, vs 21 kPa at sea level).

Parameters:

(1) SaO2 on pulse oximetry while breathing room air (FIO2 = 0.21) for 5 minutes

(2) minimum SaO2 during the 20 minute HIT trial (FIO2 = 0.15)

(3) PaO2 after the HIT

(4) PaO2 after breathing supplemental oxygen at 2 liters/min for 20 minutes

SaO2 on room air	minimum SaO2 during HIT	PaO2 after HIT	PaO2 after oxygen	Interpretation
< 90%	NA	NA	NA	unit
>= 90%	< 85%	NA	< 7.5 kPa	unfit
>= 90%	< 85%	NA	>= 7.5 kPa	fit with oxygen
>= 90%	85 - 89%	>= 7.5 kPa		fit to fly
>= 90%	85 - 89%	< 7.5 kPa	< 7.5 kPa	unfit
>= 90%	85 - 89%	< 7.5 kPa	>= 7.5 kPa	fit with oxygen
>= 90%	>= 90%			fit to fly

where:

• If the minimum SaO2 is < 85% during the HIT, then the test is stopped and supplemental oxygen given. In Figure 1 it mentions that areterial blood gases are taken immediately but there is no mention on how this is used.

• Fit to fly with oxygen indicates that a tank of supplemental oxygen is provided during the flight.

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Hypoxia Inhalation Test (HIT) of Robson et al for Evaluating a Patient with Chronic Lung Disease Prior to Air Travel

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