minute respiratory rate, PaO2, SaO2 and pulmonary functions was found in volunteers taking
acetazolamide. Erythropoietin achieved its maximum level (23 fold increase) after 24 hours of
ascent and started decreasing after 72 hours but did not reduce to pre-ascent level. The significant
increase in haematocrit was recorded after 72 hours of ascent and continued to increase even after
8 weeks. Changes in pH, Pa CO2, HCO-3, and BE revealed uncompensated respiratory alkalosis.
There was insignificant change in serum ACTH, cortisol and TSH whereas free T4 remained at
higher levels after acute and prolonged exposure to high altitude. The aldosterone decreased
initially after acute ascent but gradually rose (23 fold) on chronic exposure to hypoxia. It is
concluded that hormonal and ventilatory changes are directed at improving transport and delivery
of oxygen to tissues. Acetazolamidedexamehtasone combined therapy appears beneficial for
enhancing tissue oxygenation during acute ascent.
96.
SHORT-CYCLE HYPOXIA WORSENS HYPOXEMIA AND MOUNTAIN SICKNESS. Outi
Hyyti
1
, Xue-Han Ning
2
, Shi-Han Chen
3
, Cheng-Su Xu
4
, Fu-Ren Li
4
, Shu-Ping Li
4
, De-Song
Song
4
, Michael Portman
3
. Univ of Washington
1
, Univ of Washington, CHMC, Qinghai-Tibet
High Altitude Physiology Collaborative Group
2
, Univ of Washington, CHMC
3
, Qinghai-Tibet
High Altitude Physiology Collaborative Group
4
.
Sleep periodic breathing and heavy physical work can induce short-cycle hypoxia (SCH) to
further worsen hypoxemia at high altitude. Hypothesi:s There exists a threshold that can be
reached by SCH to cause injury. If SCH does not reach this threshold, molecular adaptive
responses may be induced. Methods: Human: ECG and respiratory graph were recorded in
patients with chronic mountain sickness, in mountaineers and miners during rest, physical work
and sleep. Animal model: Isolated perfused rabbit hearts, where no systemic factors were present,
were used to test the hypothesis. Results: Human: SCH was induced by sleep periodic breathing
(PB), one of the earliest syndromes for impairing (?It is unclear to me what this person is trying
to say) acclimatization, and was accompanied with hypoxic characteristics on ECG. PB was
severe in patients with chronic mountain sickness, and was observed commonly in mountaineers
above 8500 m. SCH with abnormal ECG was also induced by heavy physical work in miners at
high altitude. Breathing and ECG returned to normal by increasing environmental oxygen
pressure during sleep with hyperbaria or inhalation of oxygen. Animal: Myocardial injury was
indicated by loss of recovery of cardiac function during reoxygenation. Injury threshold induced
by SCH depended on three factors: the hypoxic intensity (oxygen content 0.22 _mol/ml); the
timing of hypoxia/reoxygenation (H/R at 30/90 sec); and the cycle numbers. Functional recovery
varied inversely to length of hypoxia and cycle number. The functional recovery, ATP, and
mRNA of bF1-ATPase did not differ between H/R at 10/110 sec and control hearts, but decreased
at 30/90 sec and dramatically decreased at 120/120 sec. When SCH did not reach the threshold,
protective factors (HSP70-1, Grp94) were induced. Conclusion Acclimatization was impaired by
SCH. SCH injury threshold exists in the myocardium. When SCH does not reach the threshold,
instead of injury, molecular adaptive responses are induced.
97.
QUEST FOR CMS IN THE HINDUKUSH, KARAKORAM AND HIMALYAYA (HKH)
REGION. Muhammad Ilyas
1
, Hajira Ilyas
1
, Farakh A. Khan
2
. MMM_IMRC, Pakistan Heart
Foundation
1
, K.E. Medical College, Lahore
2
.
The north of Pakistan is the arena where the Hindukush, Karakoram and Himalaya (HKH)
merge. The highlanders of HKH were studied for human geography, physical anthropology,
blood pressure and serum lipids levels, electrocardiography and plethysmography (MMM-I,
1986, MMM-II, 2004). They were shorter, lighter and leaner than subjects in Peshawar (300 m).
The mean systolic blood pressure in the highlanders of Misgar and Shimshal was significantly
lower than in comparable subjects in Karachi (SL), with no significant increase in the chest
volume or vital capacity compared to residents in Peshawar. Electrocardiographic surveys
demonstrated sinus bradycardia, and plethysmography confirmed significantly prolonged left
ventricular ejection time due to increased stroke volume. The incidence of coronary heart disease
