Hypoxic Challenge Testing (Fitness to Fly) in children with complex congenital heart disease

Abstract

Objective: Commercial airplanes fly with an equivalent cabin fraction of inspired oxygen of 0.15, leading to reduced oxygen saturation (SpO₂) in passengers. How this affects children with complex congenital heart disease (CHD) is unknown. We conducted Hypoxic Challenge Testing (HCT) to assess need for inflight supplemental oxygen.

Methods: Children aged <16 years had a standard HCT. They were grouped as (A) normal versus abnormal baseline SpO₂ (≥95% vs <95%) and (B) absence versus presence of an actual/potential right-to-left (R-L) shunt. We measured SpO₂, heart rate, QT interval corrected for heart rate and partial pressure of carbon dioxide measured transcutaneously (PtcCO₂). A test failed when children with (1) normal baseline SpO₂ desaturated to 85%, (2) baseline SpO₂85%-94% desaturated by 15% of baseline; and (3) baseline SpO₂75%-84% desaturated to 70%.

Results: There were 68 children, mean age 3.3 years (range 10 weeks-14.5 years). Children with normal (n=36) baseline SpO₂ desaturated from median 99% to 91%, P<0.0001, and 3/36 (8%) failed the test. Those with abnormal baseline SpO₂ (n=32) desaturated from median 84% to 76%, P<0.0001, and 5/32 (16%) failed (no significant difference between groups). Children with no R-L shunt (n=25) desaturated from median 99% to 93%, P<0.0001, but 0/25 failed. Those with an actual/potential R-L shunt (n=43) desaturated from median 87% to 78%, P<0.0001, and 8/43 (19%) failed (difference between groups P<0.02). PtcCO₂, heart rate and QT interval corrected for heart rate were unaffected by the hypoxic state.

Conclusions: This is the first evidence to help guide which children with CHD need a preflight HCT. We suggest all children with an actual or potential R-L shunt should be tested.

Keywords: airflight; airplane; congenital heart disease; hypoxia.