Assessment Method of Cooling and Heart Rewarming Speed under Cardiopulmonary Bypass
Background. The analysis of the heat propagation rate in the myocardium with hypothermia and hyperthermia of the heart under cardiopulmonary bypass is considered.
Objective. Development of a method for assessing the hypothermia and cardiac hyperthermia rate, which allows quantitatively describe the heat and mass transfer between the liquid medium and the heart muscle tissue.
Methods. The analysis of the heat spread rate in the myocardium during hypothermia and cardiac hyperthermia in conditions of cardiopulmonary bypass allows us to isolate from the temperature distribution on the thermogram the branches of the coronary vessels and their distal segments. The method application provides additional information for increasing the effectiveness of non-invasive heart temperature monitoring under cardiopulmonary bypass. Clinical approbation of a method for assessing the rate of hypothermia and hyperthermia was carried out, and cardiac thermograms were used in conditions of cardiopulmonary bypass, which were obtained using Flir i7 and ThermoCam E300 thermal imagers.
Results. Formulas are derived and a method for estimating the rate of hypothermia and cardiac hyperthermia is developed, it is determined that the temperature acceleration can be estimated as a derivative of the temperature change rate for the maximum and minimum temperature values in the investigated area of the myocardium, and the temperature change rate during the operation is determined by the ratio of the temperature range to the temperature change time period ∆T/t for the minimum and maximum temperature fluctuations.Conclusions. The obtained data allow determining the coronary obstruction degree and the degree of narrowing of the coronary arteries, which reduces the probability of ischemic complications after surgery on the open heart.
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