Hypoxic challenge

Question 1

Which screening tests are used for the hypoxia test

Answer 1

•Pulse Oximetry:
oUsually first screening test
oGenerally SpO2>95% at sea-level → no need for in-flight oxygen

Spirometry:
oAdvised in patients with known lung disease (or symptoms suggestive)
•Walk tests (e.g. ISWT/6MWT):
oMay inform a decision who needs further assessment
•Hypoxic Challenge Tests (HCT)

Question 2

Who should be assed with HCT?

Answer 2

COPD patients with resting SpO2 ≤ 95% (or desaturate to <84% on 6MWT)
•Severe Asthma – persistent symptoms/frequent exacerbations despite optimal treatment (regardless of resting SpO2)
•Moderate/severe restrictive disease including:
oSpO2 < 95% on exercise
oTLco ≤ 50% predicted
oPO2 ≤ 9.42kPa
•Existing/previous hypercapnia (or risk)
•On LTOT:
oIf HCT not available, reasonable to recommend that O2 flow rate is doubled

Question 3

WHAT IS THE METHOD FOR HCT?

Answer 3

Uses inspired gas mixture containing 15% Oxygen:
oSimilar inspired oxygen tension (PO2) to breathing at maximum allowable cabin pressure altitude (8000ft)
•Several methods commonly performed in lung function laboratories:
o15% Oxygen mixture
oUsing a body plethysmography
o40% venturi oxygen mask

Question 4

WHAT IS THE TEST END POINT?

Answer 4

Gas mixture breathed for up to 20 minutes (or if SpO2 falls < 85%)

Question 5

THE TEST END POINT IS WHEN…

Answer 5

Gas mixture breathed for up to 20 minutes (or if SpO2 falls < 85%)

Question 6

Inflight oxygen is not recommended when the Pa02 is >? Or an sp02 of >85%

Answer 6

●If PaO2 ≥ 6.6 kPa or SpO2 ≥ 85%, in flight oxygen is not recommended.

Question 7

If the PaO2 < 6.6 kPa or SpO2 < 85%, then what would be recommended.

Answer 7

oxygen should be titrated to maintain PaO2 ≥ 6.6 kPa or SpO2 ≥ 85%

Question 8

What are the contraindication for HCT?

Answer 8

oUntreated ventilatory failure
oUntreated pneumothorax
oRespiratory infection posing a risk to others (e.g. TB, SARS, MERS)
oBronchogenic Cysts – possibility of rupture