• Journal of Korean Ophthalmic Optics Society
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• v.10 no.4
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• pp.347-355
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• 2005

We investigate the distribution of central spot and the encircled energy in order to assess the performance of central obstructed optical system having central obstruction, when the central obstruction and the degree of truncated Gaussian amplitude of incident beam change. When the radius of central obstruction increases the radius of central spot on the image plane decreases, and when the degree of truncated Gaussian amplitude of incident beam increases the radius of central spot on the image plane increases. As the central obstruction and the degree of truncated Gaussian amplitude of incident beam increase, the depth of focus increases and the encircled energy of central spot decreases. We know from theses results that the effect of Gaussian factor is small as the central obstruction increases. These results was applied to develope the large optical reflection system.

• Korea-Australia Rheology Journal
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• v.16 no.2
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• pp.63-73
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• 2004

Flow in a channel with an obstruction at the entry can be reverse, stagnant or forward depending on the position of the obstruction. These flow phenomena have potential applications in the control of energy and various flows in process engineering. Parameters that affect this flow inside and around the test channel are the gap (g) between the obstruction geometry and the test channel, the Reynolds number (Re) and the length (L) of the test channel. The influence of these parameters on the flow behavior was investigated using a flat plate obstruction at the entry of the channel. A low concentration polyacrylamide solution (0.018% by weight) showing a powerlaw fluid behavior was used as the fluid in this investigation. The flow phenomena were investigated by the velocity measurement and the flow visualization and their results were compared with numerical simulation. These results of low concentration polyacrylamide solution are also compared with the results of water published elsewhere (Kabir et al., 2003). The maximum reverse flow inside the test channel observed was 20% - 30% of the outside test channel velocity at a g/w (gap to width) ratio of 1 for Reynolds numbers of 1000 to 3500. The influence of the test channel length (L) and the Reynolds number (Re) on the velocity ratio ($V_i$/$V_o$: inside velocity/outside velocity in the test channel) are also presented and discussed here.

• Tuberculosis and Respiratory Diseases
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• v.64 no.4
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• pp.272-277
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• 2008

Background: The efficacy of the use of the interventional bronchoscope for palliation of patients with central airway obstruction has been established. In the palliative setting to alleviate central airway obstruction, the use of laser resection, electrocautery, argon plasma coagulation, photodynamic therapy and cryotherapy can provide relief of an airway obstruction. Cryotherapy is the therapeutic application of extreme cold for the local destruction of living tissue. Recently, this technique has been used for endoscopic management of central airway obstructions in Korea. We report the role and complications of the use of cryotherapy for airway obstructions in patients with advanced lung cancer. Methods: We used a flexible cryoprobe for cryotherapy using nitrous oxide as a cryogen. The cryoprobe was applied through the working channel of a flexible fiberoptic bronchoscope. The temperature of the tip was approximately $-89^{\circ}C$, and the icing time was 5~20 seconds. Results: Four patients with a central airway obstruction from advanced lung cancer were treated with cryotherapy. Three of the four patients were treated successfully and the airway obstruction was improved after the cryotherapy procedure. Dyspnea, hypoxia and atelectais were improved in three cases. Two patients experienced complications- one patient experienced pneumomediastinum and the other patient experienced massive hemoptysis during the cryotherapy procedure. However, these complications resolved and did not influence mortality. Conclusion: This technique is effective and relatively safe for palliation of inoperable advanced lung cancer with a central airway obstruction.

• Tuberculosis and Respiratory Diseases
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• v.68 no.1
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• pp.6-9
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• 2010

Background: The efficacious use of interventional bronchoscope for patients with central airway obstruction due to malignant or benign lesions has been proven. Among many therapeutic bronchoscopic procedures, endobronchial cryotherapy is an established recanalization method for the obstruction of the respiratory tract. Recently, the use of this procedure has been increasing in Korea. However, limited data are available in the literature regarding its efficacy in Korea. Methods: Thirty patients, who had been treated with a flexible cryoprobe for cryotherapy were enrolled; clinical characteristics and treatment outcomes were analyzed. The patients had been treated with the technique using nitrous oxide as a cryogen under local anesthesia. Objective outcomes were 3 different degrees of therapeutic success by use of follow-up bronchoscopic findings as follows: successful, partially successful, and unsuccessful response. Subjective outcomes were evaluated as an improvement in symptoms. Results: The mean age of enrolled patients was $59{\pm}11$ years and there was a male (22/30) dominance. Twenty-three patients had malignant tumor and 7 patients had benign lesions with central airway obstruction. Successful recanalization was achieved in 11 (37%) patients, and partially successful response was achieved in 15 (50%) patients. Dyspnea was improved in 84.2% (16/19) of patients. At least one respiratory symptom was resolved in 91.3% (21/23) patients. Seven patients (23.3%) needed additional bronchoscopic electrocautery because of the bleeding as a complication of cryotherapy. Conclusion: Endobronchial cryotherapy is an effective and less expensive procedure for the management of central airway obstruction. However, the procedure should be performed under the preparing for an emergency situation, such as massive bleeding.

• Journal of Mechanical Science and Technology
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• v.17 no.6
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• pp.879-887
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• 2003

The flow in a parallel walled test channel, when obstructed with a geometry at the entrance, can be forward, reverse and stagnant depending on the position of the obstruction. This interesting flow phenomenon has potential benefit in the control of energy and various flows in the process industry In this experiment, the flat plate obstruction geometry was used as an obstruction at the entry of the test channel. The parameters that influence the flow inside and around the test channel were the gap (g) between the test channel and the obstruction geometry, the length (L) of the test channel and the Reynolds number (Re). The effect of the gap to channel width ratio (g/w) on the magnitude of the velocity ratio (V$\_$i/ / V$\_$o/ : velocity inside/ velocity outside the test channel) was investigated for a range of Reynolds numbers. The maximum reverse flow observed was nearly 20% to 60% of the outside velocity for Reynolds number ranging from 1000 to 9000 at g/w ratio of 1.5. The maximum forward velocity inside the test channel was found 80% of the outside velocity at higher g/w ratio of 8. The effect of the test channel length on the velocity ratio was investigated for different g/w ratios and a fixed Reynolds number of 4000. The influence of the Reynolds number on the velocity ratio is also discussed and presented for different gap to width ratio (g/w). The flow visualisation photographs showing fluid motion inside and around the test channel are also presented and discussed.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.7
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• pp.921-929
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• 2011

We measured experimentally the properties of fluid dynamics, velocity fields, and the pressure, around stenotic obstruction located inside a circular channel structure. Particle image velocimetry system was employed to obtain velocity fields at the central section of the circular channel in the streamwise direction. The stenosis model used was made of acrylic material with different stenotic aspect ratios. The working fluid was water and it was returned by a centrifugal pump system. Pressure measurements were carried out to validate the effect of a narrow passageway. Results showed that the acceleration of gap flow through stenotic obstruction and the pressure drop in the recirculation regime behind the stenosis model can be observed.

• Korean Journal of Bronchoesophagology
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• v.4 no.1
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• pp.122-126
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• 1998

Laryngomalacia is the most common cause of inspiratory stridor and varying degrees of airway obstruction in infants but rarely occurs in children or adults. However, acquired airway obstruction would be developed due to the presence of redundant mucosa in the aryepjglottic folds similar to that seen in congenital laryngomalacia after central nervous system damage. To this condition, the term“Neurasthenic Laryngomalacia”is applied. We have recently experienced a case of neurasthenic larygomalacia, which has been managed by laser aryepiglottoplasty with good result. We report management and outcome of this patient with a review of the literatures.

• Tuberculosis and Respiratory Diseases
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• v.42 no.5
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• pp.787-792
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• 1995

The obstruction of inferior vena cava(IVC) is uncommon condition. The classification is based on the obstructive sites of major anatomic segments of IVC. The main collateral pathways of interruption of IVC were central channels through ascending lumbar veins, intervertebral veins and azygos-hemiazygos complex. However, the complete obstruction of mid-portion of IVC, accompanying collateral cirulation with pericardiacophrenic vein was rarely reported. We had experienced a case of complete obstruction of mid-portion of IVC with lobulated left cardiac border, which was unforgettable characteristic finding on chest radiograph. It was confirmed by venographic examination that the lobulated left cardiac shadow was a collateral circulation of pericardiacophrenic vein.

• Tuberculosis and Respiratory Diseases
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• v.58 no.3
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• pp.295-298
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• 2005

We report a case of a 48-year-old man with a paradoxic upper airway obstruction and central sleep apnea that developed after an anterior cervical spinal fusion. Nine months before being admitted to this hospital, he was diagnosed with a herniated intervertebral disc between the 5th and 6th cervical spine, and the first operation was carried out. Two months later, a pseudoarthrosis has developed and a second operation, an anterior interbody fusion of the C5 and C6 using autogenous strut bone graft, was performed. After the second operation, he began to complain of snoring, excessive daytime sleepiness, insomnia, and a bizarre sound heard near the upper airway during breathing. Nasopharyngoscope and magnetic resonance imaging disclosed a paradoxical narrowing of the nasopharynx during expiration. On the overnight polysomnography, the apnea index was 8.7/h (central apnea, 7.0/h; obstructive apnea, 1.7/h). Nasal continuous positive airway pressure was applied, but he complained of pressure-intolerance, and laser-assisted uvulopalatoplasty was then performed. Two months after surgery, clinical symptoms as well as the apneas had improved markedly. We suggest that this paradoxic upper airway obstruction might be associated with the anterior cervical spinal surgery even though the mechanism is unclear. This case also emphasizes that an upper airway obstruction can contribute to the development of central sleep apnea.

• Journal of Korean Neurosurgical Society
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• v.55 no.5
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• pp.277-279
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• 2014

Autonomic dysreflexia is a clinical emergency syndrome of uncontrolled sympathetic output that can occur in patients who have a history of spinal cord injury. Despite its frequency in spinal cord injury patients, central nervous system complications are very rare. We report a man with traumatic high level incomplete spinal cord injury who suffered hypertensive right thalamic hemorrhage secondary to an episode of autonomic dysreflexia. Prompt recognition and removal of the triggering factor, the suprapubic catheter obstruction which led to hypertensive attack, the patient had a favorable functional outcome after the resorption of the hematoma and effective rehabilitation programme.