Gustavo Zubieta-Calleja

Retinal Vessel Diameters in Relation to Hematocrit Variation during Acclimatization of Highlanders to Sea Level Altitude

PURPOSE To examine variations in retinal vessel diameters during acclimatization of native highlanders to normobaric normoxia at sea level. METHODS Fifteen healthy residents of the greater La Paz region in Bolivia (3600 m above sea level) were examined thrice over a 72-day period, after having traveled by airplane to Copenhagen, Denmark, near sea level. RESULTS In the study subjects, hematocrit decreased from 49.6% (day 2) to 45.9% (P = 0.0066, day 23) and 41.7% (P < 0.0001, day 72); from days 2 to 23, retinal vein diameter increased by 2.68% (P = 0.0079); whereas retinal artery and vein diameters were indistinguishable from baseline after 72 days. No funduscopic signs of retinopathy were observed. Arterial blood pressure remained stable throughout the study. CONCLUSIONS Although a 16% reduction in hematocrit occurred between days 2 and 72 after arrival at sea level, the only significant excursion observed was that the diameter of the veins was larger at day 23 than at days 2 and 72. Retinal vessel diameters demonstrated a wide homeostatic range during acclimatization-driven hematocrit variation.

HIGH ALTITUDE DIVING DEPTHS

In order to make any sea level dive table usable during high altitude diving, a new conversion factor is created. We introduce the standardized equivalent sea depth (SESD), which allows conversion of the actual lake diving depth (ALDD) to an equivalent sea dive depth. SESD is defined as the sea depth in meters or feet for a standardized sea dive, equivalent to a mountain lake dive at any altitude, such that Mountain lakes contain fresh water with a relative density that can be standardized to 1000 kg m−3, and sea water can likewise be standardized to a relative density of 1033 kg m−3, at the general gravity of 9.80665 m s−2. The water density ratio (1000/1033) refers to the fresh lake water and the standardized sea water densities. Following calculation of the SESD factor, we recommend the use of our simplified diving table or any acceptable sea level dive table with two fundamental guidelines: 1. The classical decompression stages (30, 20, and 10 feet or 9, 6, and 3 m) are corrected to the altitude lake level, dividing the stage depth by the SESD factor. 2. Likewise, the lake ascent rate during diving is equal to the sea ascent rate divided by the SESD factor.

Lens autofluorescence is not increased at high altitude.

Purpose:  To study the relation between ambient environmental ultraviolet radiation exposure and lens fluorescence.

High-Altitude Research and Its Practical Clinical Application

Upon arriving above 2,500 m, the organism compensates the diminished inspired oxygen partial pressure by increasing ventilation and cardiac output. The pneumodynamic pump moves more rarefied air into the alveoli through an increase of the respiratory frequency and the tidal volume. Likewise, the hemodynamic pump increases both the cardiac frequency and the stroke volume, as if exercise were performed at sea level. The two pumps, one for air and the other for blood, carry out the essential role of supplying sufficient oxygen to the tissues and increasing the energy consumption until the red blood cells take over. The acid–base status, adequately interpreted at high altitude through the titratable hydrogen ion difference, along with the adaptation formula and multiple cellular changes, gives rise to adaptation. The tolerance to hypoxia formula reflects and explains the paradoxical concept that resistance to hypoxia grows as one goes higher. The possibility that man can adapt to live in the hypoxic environment of the summit of Mt. Everest is exposed. Furthermore, the knowledge of life at high altitude is proposed as an alternative to the environment of space travel. Herein, we describe our 43 years of experience and discoveries with fundamental concepts that change the way disease is treated in the hypoxic environment of high altitude.