The Effect of Intense Passive Apnea in the Acid-Base Balance and Electrolytes

Abstract

The aim of this study was to investigate the disturbances of the acid-base balance and electrolyte disorders in healthy individuals in the greatest passive apnea (prior to apnea and prior to first inhalation). The changes of the acid-base balance, the serum potassium and calcium levels as well as the disturbances of the cardiac rhythm were studied in a group of 15 healthy males aged 18 to 41 years old. Seven individuals part of the original group participated in a second trial. Following the initial apnea trial the individuals were allowed to 2–3 free inhalations and a second passive apnea effort was performed. The same parameters were measured in the second effort. In the primary effort the apnea duration was 170 ± 53 s (mean ± SD). The results received prior to the effort and immediately before the end of the apnea (paired t-test), showed no significant changes in the blood pH. The PaCO2 increased significantly, the PaO2 decreased significantly, blood bicarbonate increased significantly, the hemoglobin oxygen saturation decreased significantly. In addition the serum potassium and calcium levels decreased significantly. In the subgroup (7 individuals) the second effort of apnea lasted 50–70 s and showed no significant changes in the blood pH. The same changes concerning PaCO2 and blood bicarbonate were observed in the first and second effort of passive apnea. The serum potassium and calcium levels as well as the hemoglobin oxygen saturation showed no significant changes. During the initial effort of apnea all men presented bradycardia, which was followed by tachycardia immediately after the end of the effort. One individual, whose effort lasted 290 s suffered intense tachycardia, cyanosis, convulsions, and loss of consciousness. It is concluded that during an intense effort of passive apnea: (a) the blood PaCO2 is significantly increased, as well as the blood bicarbonates, (b) the PaO2, the hemoglobin oxygen saturation and the serum potassium and calcium levels are significantly decreased, (c) the cardiac rate is significantly decreased, and (d) the second effort of apnea, following immediately the initial one, is sorter in duration and produces similar or milder changes of the above parameters.