Biomedical subjects
Publications and source records attributed to M Wojtkowiak.
The goal of this paper was studying the effectiveness of frequently repeated low values of long duration acceleration on circulatory system response during gradual onset rate of acceleration on a human centrifuge.
The effects of acceleration (Gz) on changes in the levels of cortisol in saliva and of cortisol and testosterone in serum have been studied in 48 cadet pilots exposed to a linear acceleration gradient (0.2 G/s) until a loss of coordination when the mean G value was found to be 5.94 +/- 0.57. Three patterns of salivary cortisol responses were discerned based on Gz-induced significant changes: increase (I; n = 20), decrease (D; n = 8), the magnitude of changes being dependent on the pre-Gz values. Fifteen min after the Gz load, the mean salivary cortisol was significantly higher from the pre-Gz value in all subjects combined. In 19 subjects, who consented to blood sampling, significant increases in serum cortisol were observed both 3 and 15 min post-Gz (by 37 and 57% respectively) while, a significant increase in serum testosterone concentration has been observed only 3 min post-Gz. Testosterone levels 3 min post-Gz were significantly correlated with the final Gz values (r = 0.54; p < 0.05). A significant correlation was also observed between all salivary and serum cortisol values combined (r = 0.696; p < 0.001). It has been concluded that acceleration stress, although of very short duration, proved very potent in eliciting glucocorticoid and androgen responses.
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Experiments were performed on 60 rats undergoing about 5 Gz acceleration. The animals were killed in liquid nitrogen at various times after centrifugation (time of centrifugation 1 hour). Before centrifugation 131I-labelled albumin was injected intravenously and after the experiment radioactivity of muscles from the extremities was measured. The following conclusions were drawn from the experiments: (i) About 5 Gz acceleration in the longitudinal axis results in blood displacement to the hind limbs with extravascular leakage of albumin. (ii) Immediately after centrifugation lowering of blood amount in the hind limbs occurred. During the first 15 minutes this decrease progresses very quickly, while later it is much smaller. Nevertheless even 3 hours after centrifugation there was only partial return to normality. (iii) Transudation of albumin in the hind limbs lasts a few hours after centrifugation. (iv) The haemodynamic changes caused by centrifugation consist of blood stasis and extravascular leakage of proteins.
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Twenty-five men with decreased acceleration tolerance limits were subjected to two weeks centrifuge training, in which selected characteristics of +Gz acceleration (head-feet directed) were applied. The training loads were controlled basing on the responses of blood flow velocity and heart rate. The results show that the human centrifuge training in which the graded loads are based on measurement of these parameters, increases acceleration tolerance limits. It is also demonstrated that the human centrifuge training methods can be used in pilots after convalescence period or on finding lowered acceleration tolerance produced by other causes. The physical and physiological methods of increasing acceleration tolerance limits (ATL) consist some of the most important and urgent problems of today to be solved in modern military aviation. This demand is produced not only by the systematically increasing requirements as to the highest health performance of the military pilot, but also by the enormous costs of the flying equipment and training. In the group of different methods of increasing ATL, the human centrifuge training is an open problem. The available literature presents only a few reports in which the +Gz acceleration (i.e. head-pelvis directed) was used as the loading stimulus in pilots' training. The reasons for the lack of interest in this direction of examination include: easily developed decompensation of the circulatory system; cummulated effects of acceleration, and lack of optimal criteria to evaluate the body systems loads. Moreover, the positive effects of training could be baffled by the above mentioned factors.(ABSTRACT TRUNCATED AT 250 WORDS)