Introduction:The most single hazard of Flight at high altitude is Hypoxia.The new generation of the Commercial Jets aircrafts keep the cockpit and cabin environment altitude between 1.828 mts.( 6000 f ) and 2.438 mts.( 8.000 f ). This characteristic determine a Mild Hypoxia induced by breathing air at these altitudes, that in general may be considered acceptable for the normal healthy people, but in susceptible persons with known coronary artery disease (CAD), exposed in non-stop international routes for more than 13 hs, it may unchain in-flight a Major Cardiovascular Events and inclusive the Death.  

Objetive. This paper describe the validation of the Basal Oxygen Concentration Decrease (BOC-D) Test as a predictive study of Cardiac behavior in Mild Hypoxia.

Method. A comparison study was performed to include: 1. A control group of 10 healthy male subjets (asymptomatics), and 2. A group of 14 male pacients with C.A.D. who had undergone a) a Coronary arterial by-pass surgery, b) a percutaneous transluminal coronary artery dilatation and/or c) a stent procedure.
The BOC-D test is a single integrated sequential procedure. It involves Single-Photon Emission Computed Tomography (SPECT) analysis performed both at rest and under ergometry. On day 1 the subjects were at rest (basal condition) and exposed to a normal  Atmosphere of 21 % oxygen. On day 2 the subjects performed an exercise stress test while exposed to an Atmosphere of 15 % oxygen, equivalent to altitude of 2.438 mts.( 8.000 f.). Both groups were administered 15 mCi of MIBI  Tc 99m during rest  (day 1) and during maximum exercise (day 2). Oxygen consumtion, anaerobic threshold, and functional respiratory capacity were determined.

Results. In the Control Group the SPECT analysis there was no difference between rest and exercise in the Cellular level (mitochondrial) oxygen uptake . In CAD subjects, only in the ergometric test at the maximum exercise attained breathing atmosphere with 15 % oxigen all of them showed a significant lacunar defects that are expression of lack of oxygen in the cellular level on the terrytory of the affected coronary artery.

Conclusion.  The new Cardiovascular test (BOC-D) was shown to be consistent in evaluating preflight cardiac behavior on subjets with C.A.D., who have undergone Major Cardiac events or Medical interventions. This test will be usefull to Air-Crews that must certify their Psycho-physiologic habilitation and also for Passengers that must travel in a environment of Mild Hypoxia in International ultra long-haul flights .