• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2693-2695
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• 2002

In this paper, the power spectral analysis of heart rate variability(HRV) was performed to evaluate effects of orthostatic stress with head-up tilt on autonomic nervous system(ANS) for 20 healthy male subjects(age : 245 yr.) and a new method was proposed to assess the autonomic balance. The ECG signals wore recorded for 3 minutes in both the supine and 70 head-up tilt positions, and then the HRV signals underwent power spectrum analysis at each position. The results of this study suggest that cardiac autonomic functions, such as sympathetic tone in autonomic balance with the increment of sympathetic tone and the decrement of parasympathetic tone which occur during head-up tilt position, arc not sufficient to overcome tile orthostatic stress arising in Cerebral Palsy.

• The Journal of Korean Society for Radiation Therapy
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• v.18 no.1
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• pp.43-51
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• 2006

Purpose: To resolution of A hospital-handmade modification double tilt angle immobilization system (DTAB immobilization system) and to report the clinical results of it. Material and Methods: It was developed in conjunction with the breast board for patients unable to achieve and maintain the desired uncomfortable respiration and position of set-up needed in the treatment of RT (This custom design provides an alternative to accomplishing this desired head angle needed to relax position treatment area, realizing that the lenses totally protected eye-ball out) By using the angled breast board and SBDD(small bowel device), reproducibility of set-up and patient comfort were addressed throughout the simulation, computed tomography planning and treatment process. Results: Usually patients the error range-within 5 mm. When use of Aqua patients error range-within 3 mm. Conclusion: It was constructed in tandem with a unique custom-built double tilt angle board (DTAB). It was designed to eliminate clinical set-up problems with head immobilization and instability during treatment, thus providing for a more comfortable head rest for the patient.

• The Korean Journal of Physiology
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• v.30 no.2
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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.

• International Journal of Vascular Biomedical Engineering
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• v.3 no.1
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• pp.14-22
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• 2005

In the present study, our aim is to investigate whether responses to the head-up tilt (HUT) on nonlinear properties of heart rate variability (HRV) in young and elderly subjects are different or not. Thirteen young-healthy subjects ($24.5{\pm}3.7$ years) and 18 old-aged healthy subjects ($74.5{\pm}7.4$ years) participated in this study. An electrocardiogram (ECG) in the supine posture, at $0^{\circ}$, and in the standing posture, at $70^{\circ}$ of head-up tilt, was recorded. Detrended fluctuation analysis (DFA) and approximate entropy (ApEn), measures of short-/long-term correlation properties and overall complexity of heart rate (HR) respectively, along with spectral components of HR variability (HRV) were analyzed for both the supine and HUT postures. We observed that the short-term fractal exponent ${\alpha}_1$ increased during HUT posture (F(1, 29) = 39.79, P = 0.000), especially, the young subjects showed a significantly higher values compared to the elderly subjects. ApEn significantly decreased (F(1, 29) = 8.61, P = 0.006) during HUT posture. HUT posture decreased the complexity in HR dynamics and increased short-term fractal exponent values in young subjects but not in elderly subjects. These results imply that there are differences of response to HUT on nonlinear properties between young and elderly subjects.

• Journal of Biomedical Engineering Research
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• v.18 no.1
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• pp.37-44
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• 1997

In this paper, the power spectral analysis of heart rate variability(HRV) was performed to evaluate effects of orthostatic stress with head-up tiIt on autonomic nervous system(ANS) for 25 healthy male subjects(age : 24 $\pm$ 5 yr.) and a new method was proposed to assess the autonomic balance. The ECG and respiration signals were recorded at tiIt angles of $0^{\circ}$, $45^{\circ}$, $90^{\circ}$and $0^{\circ}$ successively for 10 minutes per each stage under the condition of frequency controlled respiration(0.25Hz). Heat rate(HR) gradually increased ils the angle increased Similarly, according to the increment of angle, normalized low frequency component(0.05-0.15Hz) gradually increased, whereas normalized high frequency component (0.20-0.30Hz) was reduce4 From these results it is speculated that orthostatic stress head-up tiLt, results in the prevalence of sympathetic tone in autonomic balance with the increment of sympathetic tone and the decrement of parasympathetic tone, which seems to meanthat autonomic nervous system plays a major role in compensating for disturbances of cardiovascular system due to it.

• The Journal of Korean Society for Radiation Therapy
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• v.22 no.2
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• pp.85-95
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• 2010

Purpose: The degradation of an image quality and error of the beam dose calculation can be caused because the metal artifact is generated during the CT simulation of head and neck patient. The usability of the gantry tilt scan for reducing the metal artifact tries to be appraised. Materials and Methods: The inferior $20^{\circ}$ gantry tilt scan was made in order to reduce the metal artifact and $0^{\circ}$ reconstruction image was acquired. The AAPM CT performance Phantom was used in order to compare the CT number of the reconstructed image and Original image. the difference of volume was compared by using the acrylic phantom. The homogeneity of the CT number was evaluated the Intensity volume Histogram (IVH) as in order to evaluate an influence by the metal artifact. A dose was evaluated as the Dose Volume Histogram (DVH). Results: in the comparison of the CT number and volume, the difference showed up less than 0.5%. As to the comparison of IVH, in the gantry tilt scan, influence by an artifact was reduced and the homogeneity of the CT number was improved. The comparison of DVH result reduced the mean dose error of the both sides parotid 0.2~6%. Conclusion: In the Head & Neck radiation therapy, It is difficult and to distinguish tumor and normal tissue and the error of dose is generated by the metal artifact. The delineation of the exact organization was possible if the Gantry tilt scan was used. The CT number homogeneity was improved and the error of dose could be reduced. The Gantry tilt scan confirmed in the Head & Neck radiation therapy to be very useful in the exact radiation therapy.

• Anxiety and mood
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• v.16 no.2
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• pp.83-90
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• 2020

Objective : Heart rate variability (HRV) is known to reflect autonomic nervous system activity. Individuals with posttraumatic stress disorder (PTSD) are reported to have lower HRVs. We attempted to find HRV indices with head up tilt position that reflect the symptoms well in order to evaluate PTSD symptoms. Methods : Sixty-seven patients with PTSD and 72 patients without PTSD were assessed using the PTSD Checklist for DSM-5 (PCL-5), the Beck Depression Inventory, the Beck Anxiety Inventory and the Pittsburgh Sleep Quality Index. HRV was measured in the head-up tilt position. We collected data regarding heart rate (HR), standard deviation of the NN intervals (SDNN), the square root of the mean squared differences of successive NN intervals (RMSSD), log low-frequency (LNLF) and log high-frequency (LNHF). Results : The value of LNHF was different according to presence or absence of PTSD after head-up tilt position. In the findings of the association between PTSD symptoms and HRV indices as based on head-up tilt, LNHF had a significant correlation with the total score of PCL-5. Conclusion : The reduction of the high-frequency component of HRVs in the PTSD group might reflect more PTSD symptoms.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.406-409
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• 1997

In this paper, the power spectral analysis and fractral dimension analysis of heart rate variability(HRV) were performed to evaluate effects of orthostatic stress with head-up tilt on autonomic nervous system(ANS) for 24 young and healthy subjects(age: $24{\pm}5yr$.). The ECG and respiration signals were recorded at the tilt angle of $0^{\circ},\;15^{\circ},\;30^{\circ},\;45^{\circ},\;70^{\circ}$ and $90^{\circ}$ successively for 5 minutes per each stage under the condition of frequency controlled respiration (0.25Hz). Heart rate(HR) gradually increased as the angle increased. Similarly, according to the increment of angle, normalized low frequency(LF) component(0.05-0.15Hz) gradually increased, whereas normalized high frequency(HF) component (0.20-0.30Hz) was reduced. From these results it is speculated that orthostatic stress, head-up tilt, results in the prevalence of sympathetic tone in autonomic balance with the increment of sympathetic tone and the decrement of parasympathetic tone, which seems to mean that autonomic nervous system plays a major role in compensating for disturbances of cardiovascular system due to it.

• The Korean Journal of Physiology
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• v.19 no.2
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• pp.139-153
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• 1985

The passive tilt has been performed to study the orthostasis on the cardiovascular system. The orthostasis due to upright tilt was demonstrated as follows: the venous return, cardiac output and systemic arteiral blood pressure were decreased, whereas there was concomitant increase of heart rate, through the negative feedback mediated by such as the baroreceptor . Previous investigators have suggested that the tolerance to the orthostasis could he increased by blocking the cholinergic fiber with atropine which prevented vasodilation and bradycardia through the vasovagal reflex during the orthostasis. However, this hypothesis has not been clearly understood. This study was attempted to clarify the effect of atropine on the tolerance of the cardiovascular system to the upright and head-down tilt, and to investigate the change of the blood flow through head and lower leg with Electromagnetic flowmeter in both tilts before and after atropine state. Fourteen anesthetized dogs of $10{\sim}14kg$ were examined by tilting from supine position to $+77^{\circ}$ upright position (orthostasis), and then to $-90^{\circ}$ head-down position (antiorthostasis) for 10 minutes on each test. And the same course was taken 20 minutes after intravenous administration of 0.5mg atropine. The measurements were made of the blood flow(ml/min.) on the carotid artery, external jugular vein, femoral artery and femoral vein. At the same time pH, $PCO_2$, $PO_2$ and hematocrit (Hct) of the arterial and venous blood, and heart rate(HR) and respiratory rate (RR) were measured. The measurements obtained from upright and head-down tilt were compared with those from supine position. The results obtained are as follows: In upright tilt, the blood flow both on the artery and the vein through head and lower leg were decreased, however the decrement of blood flow through the head was greater than the lower leg And the atropine attenuated the decrement of the blood flow on the carotid artery, but not on the vessels of the lower leg. HR was moderately increased in upright tilt, but slightly in head-down tilt. The percent change of HR after the atropine administration was smaller than that before the atropine state in both upright and head-down tilts. Before the atropine state, RR was decreased in upright tilt, whereas increased in head-down tilt. However after the atropine state, the percent change of RR was smaller than that of before the atropine state in both upright and head-down tilts. In upright tilt, venous $PCO_2$ was increased, but arterial $PO_2$ and venous $PO_2$ were slightly decreased. Hct was increased in both upright and head-down tilts. The findings of blood $PCO_2$, $PO_2$ and Hct were not interferred by the atropine. In conclusion, 1;he administration of atropine is somewhat effective on improving the cardiovascular tolerance to postural changes. Thus, atropine attenuates the severe diminution of the blood flow to the head during orthostasis, and also reduces the changes of HR and RR in both orthostasis and antiorthostasis.

• Annals of Clinical Neurophysiology
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• v.1 no.1
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• pp.64-69
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• 1999

Background : Syncope was defined as transient loss of consciousness and postural tone. The mechanisms of changes in cerebral hemodynamics during syncope have not been fully evaluated. Transcranial Doppler Ultrasonography can continuously monitor the changes in cerebral hemodynamics during head-up tilt (HUT). TCD could reveal the different patterns of changes in cerebral hemodynamics during syncope. Syncope without hypotension or bradycardia could be detected by TCD. We investigated the changes in cerebral blood flow velocity during HUT using TCD in 33 patients with a history of recurrent syncope or presyncope of unknown origin. Methods & Results : The positive responses were defined as presyncope or syncope with hypotension, bradycardia, or both. During HUT without isoproterenol infusion, there were a $86{\pm}23%$ drop in DV and a $41{\pm}34%$ drop in SV in 5 patients with positive reponses, and mean changes in those were less than 10% in patients with negative reponses (p=.00, p=.00). During HUT with isoproterenol infusion, TCD showed a $80{\pm}18%$ drop in diastolic velocity in 14 patients with positive reponses, and a $47{\pm}10%$ drop in that in patients with negative reponses (p=.00), however the change in systolic velocity did not differ. TCD showed three patterns during positive responses; loss of all flow, loss of end diastolic flow, and a decrease in diastolic velocity. Loss of consciousness occurred in the patients with loss of all flow or end-diastolic flow during positive reponses. Conclusions : TCD shows different patterns of changes in cerebral hemodynamics during HUT. TCD can be used to investigate the pathophysiology of neurocardiogenic syncope.