RTO MP-062 / HFM-050 - FTP Directory Listing - Nato

T-4
authorities. Type I may ground an aircraft pilot for three to seven days, and type II for one
month. Headache after exposure has traditionally been classified as type II. However, in paper
2, scull sutures are viewed as joints, where bubbles may cause pain. This opens up for the
possibility that headache may be classified as type I DCI. It is also possible that the pain may
stem from other scull structures than the sutures, and still be classified as type I. I do not think
the classification of DCI in type I and II is very helpful, because this distinction implies that
any neurological symptom is regarded as more serious than any symptom from other
structures. Besides, for any bubble effect to be detected by the subject, nerve endings must be
affected. Thus, any DCI symptom could theoretically be classified as type II. I would regard
massive joint pain as more serious than a small hypesthetic skin patch caused by a bubble
compressing a small, peripheral nerve branch, or compromising the blood supply to the same.
However, with respect to rules and regulations, the issue discussed in paper 2 may have
important operational implications for special alliance missions. Further, the neurologic
damage markers demonstrated in recent stroke studies, may prove helpful in the distinction
between DCI I and II. The development in this field should thus be followed.
Breathing gas composition
Most military sea and land surface operations can be conducted safely and effectively without
paying attention to the ambient atmosphere, except for pollution. However, in hyperbaric
diving and altitude exposure the breathing gas composition becomes a prime concern.
Hyperoxia
This may be a problem only during hyperbaric diving and the operation of high altitude flying
in agile combat aircraft.
Aviation
Oxygen is a very reactive and aggressive element, but essential to most life forms. Man is
adapted to function optimally in an atmosphere with an oxygen partial pressure (pO2) of
approximately 21 kPa.
Toxic effects of pure oxygen breathing are not a problem at reduced ambient pressure during
high altitude flying. However, when oxygen replaces also the nitrogen in the breathing gas,
+Gz accelerations exceeding 4G rapidly induce absorption collapse of the basal parts of the
lungs, associated with large right to left shunting and bouts of uncontrollable coughing. This
may have an unfavourable influence on pilot efficiency in fight.
The high rate of gas absorption from non-ventilated middle ears, may cause delayed middle
ear barotrauma, with ear discomfort and deafness. As stated in the first Key Note presentation,
these problems can be avoided by preventing the nitrogen concentration from dropping below
40%. Accordingly, the oxygen concentration in the breathing mixture should not exceed 60%
at high altitude if sustained high +Gz accelerations may be encountered, like in the new
generation of agile combat aircraft. However, this requirement may be in conflict with the
oxygen concentration required to prevent hypoxia at high cabin altitude, as well as to prevent
alveolar pO2 from dropping below 30 mmHg after rapid cabin decompression. This conflict
will increase with increasing cabin differential pressure, and is obviously an important
operational problem in alliance aviation missions. Accordingly, these aspects must be given
priority regarding the construction and operation of this type of aircraft.
Diving
As stated in paper 23, central nervous system (CNS) and pulmonary oxygen toxicity are
central problems in hyperbaric diving. Thus, regulation of pO2 in the breathing mixture is