To evaluate the state of external respiration system, breath-holding tests are usually used. However, there are few studies of the peculiarities of the gas exchange in breath-holding with previous hyperventilation. The purpose of the study was to analyze the dynamics of changes in the PetCO2 level and arterial blood oxygenation during breath-holding tests with and without previous hyperventilation in healthy young men. Materials and methods. The СО2 level was recorded in the side stream on the Datex Normocap capnograph (Datex, Finland). This value was recorded for 5 minutes at rest, 5 minutes after half-breath hold, for 5 minutes of regulated breathing with a frequency of 30 cycles per minute, 5 minutes after half-breath hold. The capnogram, atmospheric pressure level and humidity were used to assess the level of СО2 at the end of exhalation (PetCO2), respiratory rate, the ratio of inspiratory duration to expiratory duration (Rie). Statistical processing of the results was performed by parametric methods. According to the method of sigmoid deviation, three groups of individuals were distinguished by the PetCO2 level: I – PetCO2 < 32.7 mmHg, II – PetCO2 – 32.7-36.2 mmHg, III – PetCO2 > 36.2 mmHg. Results and discussion. Breath-holding during the test after hyperventilation was significantly greater than in the first attempt (62.99±3.31 s and 33.78±2.24 s, p <0.001). Visual qualitative and quantitative analysis of capnograms and graphs of arterial blood oxygenation revealed significant inter-individual features of the reactions of these indicators to tests. Therefore, changes in PetCO2 were compared depending on its initial level. After the breath-holding test, the PetCO2 levels on average during the 5-minute recovery reliably decreased in groups II and III compared with I. During the test with hyperventilation, a natural significant increase in its level of reactivity was registered, most pronounced in group III (-13.48 mmHg, p <0.001). After the second breath-holding, there was a decrease in PetCO2 compared to the level after the first breath-holding in all groups. However, the level of HbO2 in the tests differed only in group II. Thus, after a breath-holding test, individuals with relatively low PetCO2 did not have its decrease in contrast to those with relatively medium and high levels. The use of hyperventilation potentiates these reactions before breath-holding, and aligns their level after a long recovery period in different groups. Conclusion. The study shows that breath-holding tests without and after hyperventilation significantly affect the level of CO2 stress and arterial blood oxygenation; the breath-holding test after hyperventilation potentiates the decrease in PetCO2 and HbO2 in arterial blood by increasing breath-holding time. There are significant individual features in the reactivity of such physiological parameters
Keywords: carbon (IV) oxide, HbO2, hyperventilation, breath-holding, PetCO2
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