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Aim. To study the features of the impact of the extreme climate and weather factors of an arid area, which cause exacerbations of circulatory system diseases (CSD).

Materials and methods. The authors have studied 32,339 visits for emergency medical care (EMC) because of exacerbations of CSD (coronary heart disease, angina pectoris (n = 29,932), myocardial infarction (n = 306), hypertensive crises (n = 2,101) and their events) when the Afghan wind forms in winter and spring and on heat discomfort days in summer. Meteological parameters, synoptic patterns, partial oxygen density (AOD) in the atmosphere, atmospheric electric potential gradient, and human heat sensation (equivalent and effective air temperatures (EEAT)) were estimated using the generally accepted three-hour gradations.

Results. In the formation of the Afghan wind (24-48 hours before its surge, i.e. in the prodromal phase), the atmospheric electric potential gradient increased by 4-10 times. Atmospheric pressure fell by 15-20 mbar; air temperature rose by 10-15 degrees C, AOD dropped by 15-25 g/m(3) a hypoxic type of weather formed. In the surge phase, the hypoxic type drastically changed to the spastic one there was an increase in atmospheric pressure and a decrease in air temperature (by 12-19 degrees C), which gave rise to circulatory hypoxia due to vascular spasm. The average daylight air temperature changed from +31.1 to +42.2 degrees C, amounting to +36.6 +/- 1.2 degrees C; EEAT was in the gradation of heat (27-30 degrees C) and very heat (32 degrees C or higher), AOD decreased (248.6 +/- 1.3 g/m(3)), a hyperthermia-and-hypoxia type of weather was observed. The rates of EMC visits by the population for CSD exacerbations were strongly correlated with the formation of the Afghan wind (Spearman rank correlation 0.82). In the prodromal and Afghan wind surge phases, the number of exacerbations of CSD increased by an average of 2.2-3.6 times. Analysis of annual patient visits by hours during a day showed that their first rise was seen at 9.00 to 12.00 and the second (more substantial) one at 18.00 to 21.00 (p <0.05). However, in summer, the patient visit rates increased at 15.00 local legal time when there was human thermal sensation at the gradation of heat under hyperthermal hypoxia more frequently in people older than 70 years.

Conclusion. The rates of EMC visits by patients for CSD exacerbations increased in the formation of the Afghan wind and in summer during significant heat discomfort; hypoxia (external weather and internal circulatory hypoxia) is a major pathophysiological factor in these situations.