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Biomedical subjects

A S Nekhaev

Publications and source records attributed to A S Nekhaev.

16 recordsLinked to original sources
PubMed1994

[The effect of the professional activities of flight personnel on their tolerance for the rebreathing test].

The return breathing test (rerespiration) developed by the authors makes it possible to conduct testing on the efficiency of compensatory reactions and disclose the reserve capacities of cardiorespiratory system in pilots. 82 pilots were examined in the process of their professional activity. The major part can be subdivided into 3 groups with middle, good and high tolerance to rerespiration, having 1/3 of pilots under 30 years old a high tolerance to test. This test substantiates the expediency to subdivide the flight personnel into the groups of tolerance. The low tolerance can be explained by changes of functional state of organism under the influence of endogenic or exopathic factors.

Adult↗
PubMed1985

[Coronary blood flow function in patients with chronic postembolic pulmonary hypertension].

Variations in coronary blood flow and cardiac output were studied using dopplerography throughout rationed exercise in 16 patients with chronic postembolic pulmonary hypertension. All patients showed reduced coronary flow during exercise, an evidence of early signs of coronary insufficiency. A correlation was demonstrated between coronary flow disorders and the severity of pulmonary hypertension, the extent of pulmonary vascular bed lesion and right-ventricular hypertrophy.

Adult↗
PubMedDate not supplied

[Informative value of rerespiration as a method for evaluating functional reserves of the cardiorespiratory system in modeling of some flight factors].

This article presents a study of the informative value of the recurrent breathing (rerespiration) method developed by the authors, for evaluating the functional status of the human body during recovery after exposure to noise and vibration, to piloting accelerations and head-down hypokinesis. It is shown that a 1.5-h exposure to noise and vibration increases tolerance to rerespiration, suggesting a stimulatory effect. A 5-h exposure in half of cases either does not change tolerance to the test or lowers it. Piloting head-to-seat accelerations of 7 to 9 G are associated with a lowering in tolerance to rerespiration, the functional status being recovered 1 d later. A similar exposure to 3-5 G in 83% of cases is not associated with an alteration of response to the test. After a 30-day head-down hypokinesis there is a lowering of tolerance to rerespiration, both in subjects with drug correction and in the control group. On day 10 of recovery in the control group return to the baseline rerespiration tolerance level was incomplete. Medically treated subjects demonstrated a complete recovery. Thus, rerespiration in the developed methodological version, is an informative loading test allowing to evaluate the dynamics of the functional status of the body. As a signal method it helps to clarify the individual duration of recovery after performing flight-related tasks, to substantiate the necessity of rehabilitation procedures and assess their effectiveness, as well as to detect persons with a stable decline of tolerance to rerespiration.

Adult↗
PubMedDate not supplied

[Criteria of tolerance of the hypercapnia-hypoxia test].

Examination of 84 essentially healthy men, aged 19 to 34 years, by the rebreathing method showed that in various test subjects the reserve time prior to decompensation was in the range 5 to 9 min. A certain change was seen 1-2 min before termination of the test due to acute respiratory failure. This change included an increase in the minute respiration volume above 40 1/min and its relative increment by 10 1/min or over when compared to the preceding minute. The test time varied from 4 to 8 min. Analysis of the data using the cardiorespiratory index which is equal to the product of heart rate by systolic arterial pressure divided by the minute respiration volume helped to discriminate test subjects with satisfactory, good and very good tolerance of the rebreathing test.

Adult↗
PubMedDate not supplied

[Effect of the hypercapnic-hypoxic test on cardiovascular parameters in individuals with neurocirculatory dystonia].

Twenty healthy men and twelve patients with hypertensive type neurocirculatory dystonia belonging to the flying personnel were examined. They breathed a hypercapnic-hypoxia mixture formed during rebreathing in a closed circuit without a CO2 adsorber. In both groups this provocative test produced similar variations of most parameters under study. However in contrast to the healthy men, the hypertensive subjects showed a lower compensatory hyperventilation, a greater increase of blood pressure and cardiac output and a relatively small decrease of total peripheral resistance. Three test subjects displayed sinus arrhythmia. The time of test tolerance in the patients was on the average 20% shorter than in the healthy subjects. The changes can be viewed as an indication that the reserve capability of the cardiorespiratory system declines. The fact that the test is rapid, simple and safe makes it possible to use it during regular medical monitoring of the flying personnel with functional disorders of the cardiovascular system.

Adult↗
PubMedDate not supplied

[Use of central electroanalgesia to restore the body's functional state in motion sickness].

Central electroanalgesia (CEAN) is a technique that involves application of pulsating current to the central nervous system in order to enhance its tonicity recover autonomic equilibrium and to reduce parasympathetic cardiovascular reactions. In two experimental runs in which 9 volunteers participated the efficacy of CEAN in preventing motion sickness symptoms produced by Markaryan's test was studied. After two rotations repeated with a one-hour interval vestibular reactions persisted for 7-10 hours. CEAN had a positive effect: after a one-hour CEAN session applied between two rotations the tolerance time of the second rotation increased on an average by 76%. An additional exposure to CEAN after rotation eliminated almost completely the adverse effects of rotation and made effective the postrotation work. Due to CEAN parasympathetic reactions of the cardiovascular system typical of the postrotation recovery period were indistinct. These data suggest that CEAN is an effective method to be used to help a rapid recovery of the functional state of the human body during motion sickness.

Adult↗
PubMedDate not supplied

[Venous blood circulation in the crew of the Saliut-5 orbital station].

Studies of venous circulation were continued in the space crewmembers of the orbital station Salyut-5. New data which demonstrated again that weightlessness induced symptoms specifically assoicated with blood redistribution and pressure increase in the jugular veins were obtained. It is suggested to further the studies of venous circulation and regional hemodynamics aimed at determining the time and degree of human body adaptation to weightlessness.

Blood Circulation↗
PubMedDate not supplied

[Potential for modelling the hemodynamic effects of weightlessness by exposure to increased pressure].

Venous and arterial circulation was investigated by simulating cephalad blood shifts generated by an exposure of test subjects (n = 15) to lower body positive pressure (+25 mm Hg) and head-down tilts (at -8 degrees and -15 degrees). At LBPP and tilt -15 degrees arterial pressure increased by 5-15%. During tilt -8 degrees jugular vein blood filling increased by 8-94% in the course of the first 3 hrs and then decreased reaching the baseline (horizontal position) level. During LBPP the parameter changed in a similar manner (increased by 2-50%). During tilt -15 degrees the parameter grew by 10-110% and remained elevated. The exposures gave rise to bradycardia which was more pronounced during -8 degrees and LBPP. The data obtained give evidence that circulation changes during LBPP and head-down tilts are identical. This suggests that LBPP can be used to simulate the effect of cephalad blood shifts, one of the most important effects of weightlessness on the human body.

Adult↗
PubMedDate not supplied

[Dynamics of the venous circulation in the cosmonauts of the 2d "Saliut-4" expedition].

During the first month of the orbital flight the cosmonauts showed an increase in the blood pressure and filling in the jugular veins whereas during the second month they exhibited a decrease in these parameters below the preflight level. Throughout the mission the pressure in the pulmonary artery remained slightly increased. The time of contractions of the right heart changed. The changes in the blood pressure and filling in the jugular veins can be explained by blood pooling there and subsequent extravasation of blood into the abdominal cavity.

Blood Circulation↗