Approximately 741 Million Passengers Traveled on US Commercial Airlines in 2006 (Chest, 2008) [MEDLINE]
Approximately 1 Billion Passengers Travel Worldwide Each Year (Chest, 2008) [MEDLINE]
Respiratory Complaints are Among the Most Common Necessitating Emergency Calls on Airlines
Commercial Aircraft are Pressured to Approximately 8,000 Feet: corresponds to a FIO2 of 15.1%
Indications
Screening for Altitude-Associated Hypoxemia in Patients with Cardiopulmonary Disease: HAST aims to identify patients who fall on the steep portion of the hemoglobin dissociation curve and are, therefore, at risk for significant oxygen desaturation at altitude
British Thoracic Society Recommendations for Screening Based on Ground SpO2
SpO2 >95%: no further testing or supplemental oxygen with air travel is required
SpO2 92-95%: HAST is recommended to determine the need for supplemental oxygen with air travel
These recommendations recognize that pulse oximeters have large confidence intervals of 2-4%
SpO2 <92%: supplemental oxygen is recommended with air travel
Aerospace Medical Association Medical Guidelines Task Force Guidelines for Screening Based on Ground pO2
Ground pO2 <70 mm Hg: HAST is recommended (Aviat Space Environ Med, 2003)[MEDLINE]
Technique
Procedure
HAST is as Predictive as Measuring Oxygenation in a Hypobaric Chamber (Considered the Gold Standard Test)
Testing of SpO2 (or pO2) with the Patient Breathing 15.1% Oxygen (Simulating 8,000 ft = 2,400 m, Pb 565 mm Hg) via a Tight Fitting Mask/Mouth Piece or in a Body Box
Concomitant EKG Monitoring
Patient Also Wears a Nasal Cannula Beneath the Mask, Allowing Repeat Testing with Supplemental Oxygen
HAST Interpretation
pO2 >55 mm Hg During HAST: no supplemental oxygen is required
pO2 50-55 mm Hg During HAST: considered borderline -> measurement with activity can then be obtained
pO2 <50 m Hg During HAST: testing with supplemental oxygen (usually 2L/min) is performed
Clinical Data
Comparative Study of 6MWT and Hypoxia Altitude Simulation Test (HAST) in Patients with Either Interstitial Lung Disease or COPD (Aviat Space Environ Med, 2007) [MEDLINE]
Oxygen Desaturation Induced by the 6MWT Correlated with that After HAST (r = 0.52)
Study of Algorithm Using Resting/6WMT SpO2 and HAST in COPD Patients (Thorax, 2012) [MEDLINE]
Baseline SpO2 <92%: supplemental oxygen is required for air travel
Baseline SpO2 92-95%
6MWT SpO2 <84%: supplemental oxygen is required for air travel
6MWT SpO2 ≥84%:
HAST SpO2 ≤85%: supplemental oxygen is required for air travel
HAST SpO2 >85%: no supplemental oxygen is required for air travel
Baseline SpO2 >95%
6MWT SpO2 <84%
HAST SpO2 ≤85%: supplemental oxygen is required for air travel
HAST SpO2 >85%: no supplemental oxygen is required for air travel
6MWT SpO2 ≥84%: no supplemental oxygen is required for air travel
References
Aerospace Medical Association. Medical guidelines for airline travel, 2nd ed. Aviat Space Environ Med 2003; 74:A1–A19 [MEDLINE]
Walking capacity and fitness to fly in patients with chronic respiratory disease. Aviat Space Environ Med 2007;78:789–792 [MEDLINE]
The hypoxia altitude simulation test: an increasingly performed test for the evaluation of patients prior to air travel. Chest. 2008 Apr;133(4):839-42. doi: 10.1378/chest.08-0335 [MEDLINE]
Air travel and chronic obstructive pulmonary disease: a new algorithm for pre-flight evaluation. Thorax. 2012 Nov;67(11):964-9. doi: 10.1136/thoraxjnl-2012-201855. Epub 2012 Jul 5 [MEDLINE]
