• The Korean Journal of Physiology
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• 제30권2호
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• pp.237-247
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• 1996

This study was carried out to determine the effect of $-6^{\circ}$ head-down bedrest on the cardiovascular and hormonal responses to orthostasis and to evaluate the mechanism of orthostatic intolerance. Ten healthy young men were changed the body position from $-6^{\circ}$ head-down or supine bedrest for 2 hr to $70^{\circ}$ head-up tilt for 20 min. During the bedrest, there were no differences in hemodynamic and hormonal changes between the head-down and the supine positions. However, the tendency of decreased end-diastolic volume and increased cardiac contractility during the later period of 2 hr showed that the cardiovascular adaptation could be accelerated within a relatively short period in the head-down bedrest. During the head-up tilt, presyncopal signs were developed in five subjects of the supine bedrest, and one of the same subjects of the head-down bedrest. In the tolerant subjects, the increase in cardiac contractility and plasma epinephrine level during the bend-up tilt was greater following the head-down bedrest than that following the supine bedrest to compensate for reduced venous return. The intolerant subjects showed the greater decrease in end-diastolic and stroke volume, and the greater increase in heart rate during the head-up tilt than the tolerant subjects. Cardiac contractility and plasma epinephrine level were remarkably increased. However, arterial pressure was not maintained at the level for the appropriate compensation of the reduced venous return. It seems that the tolerance to orthostasis is more effective after the short-term head-down bedrest than after the supine bedrest, and the secretion of epinephrine induces the higher cardiac performance as a compensatory mechanism fur the reduced venous return during the orthostasis following the head-down bedrest than the supine bedrest.

• The Korean Journal of Physiology
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• 제19권2호
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• pp.139-153
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• 1985

기립 및 도립의 체위면화가 두부 및 하지의 혈액순환계에 미치는 영향을 관찰하고, atropine의 정주에 의한 부교감신경의 차단이 체위변화에 대한 심맥관계의 내성을 증가시키는 지를 보기위하여 개를 경사대에 수평위로 고정하여 수동적으로 기립 및 도립위로 체위를 변화시키고, 각 체위에서 10분간 유지시켜 경동맥, 외경정맥, 고동맥 및 고정맥의 분시 혈류량, 분시 심박수 및 분시 호흡수, 그리고 혈액의 pH, $PCO_2$, $PO_2$ 및 Hct를 측정하였다. 다시 수평위에서 atropine 0.5mg을 1회 정주한 후 위의 실험과정을 반복하여 시행하고 atropine투여전과 비교 관찰하였던 바 다음과 같은 결과를 얻었다. 기립시 두부 및 하지 동정맥혈의 분시 혈류량은 감소하였고, 특히 두부로 가는 혈류량의 감소가 더 컸으나, atropine의 투여는 경동맥의 분시 혈류량의 감소를 억제하였다. 도립시 두부 및 하지의 분시 혈류량은 유의한 변화를 보이지 않았고, 개체에 따라 변화양상도 다르게 나타났다. atropine의 투여는 투여전에 비하여 유의한 차이를 보이지 않았다. 분시 심박수는 기립 및 도립시 모두 증가하였다. atropine의 투여는 수평위에서 분시 심박수는 투여전 보다 증가하나, 체위변화에 의한 분시 심박수의 증가를 경감시켰다. 분시 호흡수는 개체에 따라 변화양상에 차이가 있으나, 대체로 기립시는 감소하고 도립시는 증가하였다. atropine의 투여는 기립 및 도립시 다 같이 분시 호흡수의 변화를 억제하였다. 혈액소견은 기립시 정맥철의 pH 및 $PO_2$는 감소하였고, $PCO_2$는 증가하나 동맥혈의 $PCO_2$는 감소하였다. 도립시 동정맥혈의 소견은 수평위에 비해 별 변화가 없었으며 , atropine의 투여후도 기립 및 도립시 모두에서 투여전에 비하러 유의한 변하는 없었다. Hct는 기립 및 도립시 증가하였으며 atropine투여에 의한 변화는 관찰할 수 없었다. 이상에서와 같이 atropine의 투여는 기립시 두부로 가는 혈류량을 증가시키며, 기립 및 도립시 발생할 수 있는 분시 심박수의 과도한 증가를 억제함으로서 체위변화에 대한 심맥관계의 내성을 증가시키는데 어느정도 효과가 있다고 하겠다.

• 항공우주기술
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• 제8권1호
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• pp.207-214
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• 2009

본 연구는 미세중력 모델인 머리하향기울기(Head Down Tilt; HDT) 자세에서 운동 중저산소호흡이 심혈관계 반응에 미치는 영향을 알아보는데 있었다. 8명의 건강한 남성($23{\pm}2$ 세, 신장 $176{\pm}4$ cm, 체중 $75{\pm}8$ kg)은 4가지 조건(앉은 자세에서 정상공기 호흡: SN, 앉은 자세에서 13% 산소호흡; SH, HDT 자세에서 정상공기 호흡; SH, HDT 자세에서 13% 산소호흡; HH)에서 최대산소섭취량의 약 40% 운동강도로 15분간 싸이클링을 실시하였다. 심박수는 SH그룹이 SN그룹보다 높았고(p<0.05), HH그룹이 SH그룹보다 높게 나타났다(p<0.05). 혈중산소포화도는 SH그룹이 SN그룹보다 유의한 감소를 나타내었다(p<0.05). 이완기혈압(p<0.05) 및 평균동맥압(p<0.05)은 안정시 앉은 자세에서보다 HDT 자세에서 유의하게 낮아졌다. 체액변인인 Hb, Hct과 전해질 변인인 나트륨, 칼륨, 염소는 모든 그룹에서 차이가 나타나지 않았다(p>0.05). 대사적 변인 중 Lactate는 SH그룹이 SN그룹보다 유의한 증가를 나타내었다(p<0.05). 결론적으로, 저산소호흡과 자세의 이중자극은 심혈관계반응에 영향을 주지 않았다.

• The Korean Journal of Physiology
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• 제12권1_2호
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• pp.35-40
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• 1978

경사대에 의한 수등적체위 변화시 분시 호흡수, 혈액 pH, $PCO_2$ 및 $PO_2$의 변화를 관찰하고 다음과 같은 성적을 얻었다. 체위변화시 호흡수는 기립위에서는 수평대조치에 비해 감소하고 도립위에서는 많은 증가를 보였다. 혈액 pH는 기립위에서 수평대조치에 비해 동맥혈은 0.2%가 증가되었고 정맥혈은 0.3%가 감소하였다. 도립위에서는 수평대조치와 거의 변화가 없는 값을 나타내었다. $PCO_2$는 기립위에서 수평대조치에 비해 동맥혈은 8.3%, 정맥혈은 0.3%가 감소되었고 도립위에서는 동맥혈은 20.1%가 감소되고 이것은 통계적으로 의의있는 변화였다. 정맥혈은 7%가 감소되었다. $PO_2$는 기립위에서 동맥혈은 2%가 증가, 정맥혈은 21.7%가 감소되었으며 이것은 통계적으로 의의있는 변화였다. 도립위에서는 동맥혈은 11.4%가 증가되고 정맥혈은 14.1%가 감소되었다. 도립위에서 동맥혈의 $PO_2$가 증가 되는 원인은 도립중의 과도호흡하에 의한 것이라 사료되며 정맥혈의 $PO_2$의 감소는 도립중의 근육수축에 연유하는 산소소비량의 증가가 그 원인이라고 사료된다. 또 도립위에서 $PO_2$가 감소하고 수소ion의 감소가 예상됨에도 불구하고 pH가 증가하지 않는것은 산소소비가 증가되고 정맥혈의 $PO_2$가 감소되는 것으로 봐서 염기성해당으로 젖산이 증가된것이 아닌가 생각된다.

• The Korean Journal of Physiology
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• 제7권1호
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• pp.13-21
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• 1973

An attempt was made to study circulatory and respiratory responses to the passive tilt. Anesthetized dogs were tilted from horizontal to upright $(+90^{\circ})$ and head down $(-90^{\circ})$ position. The arterial blood pressure was decreased in the upright position and was decreased slightly in the head down position comparing to that in the horizontal position. Cardiac index also decreased in the both upright and head down positions. The total systemic vascular resistance was slightly increased in the upright position and was markedly increased in the head down position. The mean pulmonary arterial pressure was significantly decreased in the both upright and head down positions. The total pulmonary vascular resistance was decreased in the both upright and head down positions. Oxygen consumption was slightly decreased in the upright position, whereas it was slightly increased in the head down position. The A-V $O_2$ difference (vol. %) was slightly increased in the upright position and increased in the head down position. From the above results, process of the circulatory compensation to the gravity in the Passive tilting test was discussed. Neuronal cardiovascular regulation to the gravity and tile adaptation of capacitance vessles to hydrostatic stress and oxygen consumption concerning anoxic endurance of the brain were also discussed.

• The Korean Journal of Physiology
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• 제5권2호
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• pp.71-78
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• 1971

Anesthetized dogs were tilted from horizontal to the upright and head down position. Tilting to the upright position was followed by an increase in heart rate. In the head down position a decreased heart rate was obtained. The arterial blood pressure was decreased in the upright position and was decreased markedly in the head down position. The central venous pressure was decreased in the upright position and was markedly decreased down to the negative pressure in the head down position. The respiratory rate was slightly increased in the upright position comparing to that in the horizontal position. No remarkable changes were noted in the head down position. From the above results the following factors were discussed The decreased arterial blood pressure during the upright position was supposed to be the secondary effect from the diminished venous return that was suggested by the decreased central venous pressure. The decreased arterial blood pressure in the head down position was also supposed as the above reason as the diminished central venous pressure during the tilt. In addition the cardioinhibitory effects originated from the baroreceptors might have been operated during head down tilting. In the heart rate there was slight tachycardia in the upright position this was assumed as the abolished cardioinhibitory impulses from the baroreceptor in the upright position. On the contrary, despite of the decrease of arterial blood pressure in the head down position as well as in the upright, the bradycardia have been appeared. This was suggestive of cardioinhibitory impulses from the baroreceptors which was stretched during head down tilting. From the above findings there is a possibility of continous cardioinhibitory responses during head down tilting for this kind of the short period of 10 minutes which was chosed in this study.

• The Korean Journal of Physiology
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• 제24권1호
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• pp.51-65
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• 1990

The purpose of the present study was to examine the hemodynamic responses, especially in arterial and skin blood flows, in conjunction with the changes of plasma catecholamine levels as an indirect marker of adrenergic tone during the early stage of head-down tilt (HDT), and to evaluate the early physiological regulatory mechanism in simulated weightlessness. Ten mongrel dogs, weighing8\;{\sim}\;14\;kg, were intravenously anesthetized with nembutal, and postural changes were performed by using the tilting table. The postural changes were performed in the following order: supine, prone, HDT $(-6^{\circ}C)$ and lastly recovery prone position. The duration of each position was 30 minutes. The measurements were made before, during and after each postural change. The arterial blood flow $({\.{Q}})$ at the left common carotid and right brachial arteries was measured by the electromagnetic flowmeter. Blood pressure (BP) was directly measured by pressure transducer in the left brachial artery. To evaluate the peripheral blood flow, skin blood flow $({\.{Q}})$ was calculated by the percent changes of photoelectric pulse amplitude on the forepaw, and skin temperature was recorded. The peripheral vascular resistance (PR) was calculated by dividing respective mean BP values by ${\.{Q}}$ of both sides of common carotid and brachial arteries. Heart rate (HR), respiratory rate (f) and PH, $Po_{2},\;Pco_{2}$ and hematocrit of arterial and venous blood were also measured. The concentration of plasma epinephrine and norepinephrine was measured by radioenzymatic method. The results are summarized as follows: Tilting to head-down position from prone position, HR was initially increased (p<0.05) and BP was not significantly changed. While ${\.{Q}}$ of the common carotid artery was decreased (p<0.05) and PR through the head was increased, ${\.{Q}}$ of the brachial artery was increased (p<0.05) and PR through forelimbs was decreased. ${\.{Q}}$ of the forepaw was initially increased (p<0.05) and then slightly decreased, on the whole revealing an increasing trend. Plasma norepinephrine was slightly decreased and the epinephrine was slightly increased. f was increased and arterial pH was increased (p<0.05). In conclusion, the central blood pooling during HDT shows an increased HR via Bainbridge reflex and an increased ${\.{Q}}$ of the forepaw and brachial ${\.{Q}}$, due to decreased PR which may be originated from the depressor reflex of cardiopulmonary baroreceptors. It is suggested that the blood flow to the brain was adequately regulated throughout HDT $(-6^{\circ}C)$ in spite of central blood pooling. And it is apparent that the changes of plasma norepinephrine level are inversely proportional to those of ${\.{Q}}$ of the forepaw, and the changes of epinephrine level are paralleled with those of the brachial ${\.{Q}}$.

• The Korean Journal of Physiology
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• 제21권2호
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• pp.211-223
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• 1987

Head-down tilt (HDT) at $-6^{\circ}$ has been commonly used as the experimental model in both man and animals to induce the blood shift toward the head or central protion of the body, demonstrating similar physiological effect encountered in the weightlessness in the orbital flight. There are few reports about the physiological response upon the cardiovascular regulatory system or the tolerance to the $(-6^{\circ})$ HDT within a relatively short period less than 1 hour. Therefore, the purpose of this study way to observe the effects of $-6^{\circ}$ HDT on cardiovascular system within 30 minutes and to evaluate early regulatory mechanism for simulated hypogravity. Ten mongrel dogs weighing 8-12 kg were anesthetized with the infusion of 1% ${\alpha}-chloralose$ (100 mg/kg) intravenously, and the postural changes were performed from the supine to the $-6^{\circ}$ head-down Position, then from the head-down to the supine (SUP), and each posture was maintained for 30 minutes. Blood flow $({\dot{Q}})$ through common carotid and femoral arteries were determined by the electromagnetic flowmeter. Mean arterial pressure (MAP), heart rate (HR), respiratory rate , and pH, $P_{O_2}$, $P_{CO_2}$ and hematocrit (Hct) of arterial and venous blood were also measured. The peripheral vascular resistance was calculated by dividing respective MAP values by ${\dot{Q}}$ through both sides of common carotid or femoral arteries. The concentration of plasma epinephrine and norepinephrine was determined by Peuler & Johnson's radioenzymatic method. The results are summarized as follows: In the initial 5 minutes in $-6^{\circ}$ HDT, HR was significantly (p<0.05) increased and MAP slightly decreased. Although ${\dot{Q}}$ and carotid peripheral artery resistance were not significantly changed, ${\dot{Q}}$ through femoral artery was diminished and femoral peripheral artery resistance was elevated. In the SUP, the initial changes of MAP and HR were increased (p<0.05), but those of ${\dot{Q}}$ and peripheral vascular resistance through both common carotid and femoral arteries were not significant. After 10 minutes of each postural change in both HDT and SUP, MAP was maintained almost equal to that of the level of pretilting control. During 60 minutes of both postural changes of HDT and SUP, $P_{O_2}$ and Hct were not changed significantly. However pH tended to increase slowly and $P_{CO_2}$ was gradually decreased. The pH and $P_{CO_2}$ seemed to be related to the increased respiratory rate. Plasma epinephrine concentration was not changed significantly and plasma norepinephrine concentration was slightly decreased in the course of HDT and also at 10 minutes of SUP. However these concentration changes were statistically insignificant. From these results, it may be concluded that the effect of $-6^{\circ}$ HDT for 30 minutes on the cardiovascular system and plasma catecholamine levels of the dog is minimum and it is suggestive that the cardiovascular regulatory mechanism, possibly mediated by so called gravity receptors including baroreceptor and volume receptor, has been properly and adequately operated.

• 수산해양기술연구
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• 제41권4호
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• pp.296-305
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• 2005

Acoustic target strength (TS) of 12 commercially important fish species caught in the Korean waters had been investigated and their results were presented. Laboratory measurements of target strength on 12 dominant fish species were carried out at a frequencies of 75 kHz by single beam method under the controlled condition of the water tank with the 241 samples of dead and live fishes. The target strength pattern on individual fish of each species was measured as a function of tilt angle, ranging from $-45^{\circ}$ (head down aspect) to $45^{\circ}$ (head up aspect) in $0.2^{\circ}$ intervals, and the averaged target strength was estimated by assuming the tilt angle distribution as N ($-5.0^{\circ}$, $^15.0{\circ}$). The 75 to fish length relationship for each species was independently derived by a least - squares fitting procedure. Also, a linear regression analysis for all species was performed to reduce the data to a set of empirical equations showing the variation of target strength to fish length and fish species. An empirical model for fish target strength(TS, dB) averaged over the dorsal aspect of 158 fishes of 7 species and which spans the fish length(L, m) to wavelength(${\lambda}$, m) ratio between 6.2 and 21.3 was derived: TS: 27.03 Log(L)-7.7Log(${\kanbda}$)-17.21, ($r^2$=0.59).

• 한국치위생학회지
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• 제12권4호
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• pp.685-693
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• 2012

Objectives : This research was conducted to find the subjective symptoms of musculoskeletal system for main jobs and job posture. Methods : A survey was conducted from September 15, 2011 to October 7, 2011 and 357 dental hygienists were responded. The survey was consisted of the working environment and medical equipments, psycho-social characteristics, health habits and education, job posture, subjective symptoms of musculoskeletal system pain, and so on. Results : In the survey on the frequency of job posture of dental hygienists by jobs, said they cast down or tilt their head by 15 degrees or more or twist or bend their back. The result of the analysis on the subjective symptoms of musculoskeletal system by main job showed that they experienced a pain in neck, shoulder, and back, although the order differed. The order of subjective symptoms of musculoskeletal system for casting down or turning head by 15 degrees or more, twisting or bending back, having shoulders not parallel to the ground, sitting at the end of a chair, and supporting the whole body with one leg or pressing on a pedal for treatment was from the shoulders to the neck to the back. The order of subjective symptoms of musculoskeletal system for having arms too far from the body or hunching for treatment and bending wrists inward or outward for treatment was from the shoulders to the back to the neck. Conclusions : Due to the characteristics of the job which requires one to have a proper view of a patient's oral cavity, most of the postures included casting down of head or bending of back. Therefore a development of new postures is needed to replace the existing job postures which pressure the musculoskeletal system. And shift rotation can be used as a preventive measure.