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P P Hsu

Publications and source records attributed to P P Hsu.

12 recordsLinked to original sources
PubMed2005

Clinical predictors in obstructive sleep apnoea patients with calibrated cephalometric analysis--a new approach.

AIM: Utilization of a new method to accurately quantify differences in cephalometric parameters between obstructive sleep apnoea (OSA) and normal patients, and to identify good predictors for OSA. To illustrate the ethnic differences in cephalometry. METHOD: This prospective study involves 106 South-east Asians. A calibrated catheter is inserted into the upper airway during standard cephalometry to obtain the precise magnification and allow exact measurement of anatomical parameters of cephalometry in both erect and supine positions. RESULTS: The OSA patients have longer lower-facial length, narrower skull base, shorter and receding mandible, smaller posterior airway space (PAS), narrower retropalatal space, longer and thicker soft palate, smaller hard and soft palate angles longer tongue length and more inferiorly displaced hyoid. For the palatal level, retropalatal distance of 11.2 mm cut-off/predictive value for male (receiver operating characteristics (ROC) = 0.8414 with PPV = 77.46, NPV = 90.00) and 5.5 mm for female (ROC = 0.9180 with PPV = 100.00, NPV = 84.21) at erect position were selected. For retrolingual level, erect PAS of 10.1 mm cut-off/predictive value for male (ROC = 0.7000 with PPV = 78.38, NPV = 37.78), 5.3 mm for female (ROC = 0.7227 with PPV = 75.00, NPV = 75.00) were selected. Our study showed that South-east Asians have different cephalometric values compared with White people, Black people and Hispanics. CONCLUSION: This new method of cephalometry using a calibrated catheter provides an accurate and simple method of obtaining precise cephalometric measurements. There is no cephalometric data on OSA from South-east Asia available. These results suggested that surgeons managing OSA patients and using cephalometry as a diagnostic method should have a set of normative and OSA cephalometric values that apply to their local populations.

Adult↗
PubMed2005

Migrating esophageal foreign bodies.

UNLABELLED: Ingested foreign bodies which migrate extraluminally, although rare in occurrence, are fraught with the potential to cause life-threatening complications. PURPOSE OF THE STUDY: To discuss the management of this pathology. MATERIAL AND METHODS: A series of four patients with such occurrences is presented. CONCLUSION: A discussion on the safe management of such seemingly innocuous foreign bodies allows the authors to propose a therapeutical algorythm.

Adult↗
PubMed2005

10th Yahya Cohen Memorial Lecture: Clinical predictors in obstructive sleep apnoea patients with computer-assisted quantitative videoendoscopic upper airway analysis.

AIM: To identify the clinical predictors and assist surgeons in their clinical management of obstructive sleep apnoea (OSA) - a prospective study with a new approach to analyse the static and dynamic upper airway morphology between patients with OSA and normal subjects. To introduce a new method of assessment for surgical outcome. MATERIALS AND METHODS: Quantitative computer-assisted videoendoscopy (validated with upper airway magnetic resonance imaging) was performed in 49 (43 males, 6 females) patients with OSA and compared with 39 (22 males, 17 females) controls (apnoea-hypopnoea index <5). Absolute cross-sectional areas, transverse and longitudinal diameters at the retro-palatal and retro-lingual levels were measured during end of quiet respiration and during Mueller's manoeuvre in the erect and supine positions, allowing us to study static and dynamic morphology (collapsibility) of the upper airway. We analysed 3744 parameters. RESULTS: In males, retro-palatal and retro-lingual areas during Mueller's manoeuvre in the supine position of 0.7981 cm2 [receiver operating characteristics (ROC) = 0.9284, positive predictive value (PPV) = 86.05%, negative predictive value (NPV) = 84.62%] and 2.0648 cm2 (ROC = 0.8183, PPV = 76%, NPV = 83.33%), respectively, were found to be good predictors/ cut-off values for OSA. Retro-palatal area measured in the supine position during Mueller's manoeuvre (AS1M) and collapsibility of retro-palatal area in the supine position calculated (CAS1) were found to have significant correlations with severity of OSA. In females, areas measured during Mueller's manoeuvre in the supine position of 0.522 cm2 at retropalatal level (ROC = 1, 100% PPV and NPV) and transverse diameter at retro-lingual level during erect Mueller's manoeuvre of 1.1843 cm (ROC = 0.9056, PPV = 100%, NPV = 83.33%) were found to be predictive. All measurements at the retro-palatal level and in the supine position had higher predictability. Area measurements obtained during Muller's manoeuvre were more predictive (ROC >0.9910) than resting measurements (ROC >0.8371). Several gender and anatomical-site specific formulas with excellent predictability (ROC close or equal to 1) were also devised. Examples of surgical outcome assessment were introduced. CONCLUSION: Upper airway Mueller's studies are predictive and useful (independent samples t-test/Mann Whitney U test, ROC) in identifying patients with OSA. With these gender and anatomical-site specific OSA predictors/formulas and this innovative clinical method, we hope to assist other surgeons with quantitative clinical diagnosis, assessment, surgical planning and outcome assessment tools for OSA patients.

Adult↗
PubMed2004

Quantitative computer-assisted digital-imaging upper airway analysis for obstructive sleep apnoea.

This was a prospective study of a new objective method which quantitatively analyses the upper airways in patients with obstructive sleep apnoea (OSA). Video-nasopharyngoscopic examinations of the upper airways of 45 patients were carried out with an endoscopic calibrator. Images of the upper airway during quiet respiration and Mueller's manoeuvre in erect and supine positions were digitized by computer to generate the actual dimensions of obstructive sites. Measurements by the new method were validated by comparing 90 pairs of videoendoscopic images with upper airway magnetic resonance imaging (MRI) measurements at two identical levels. Quantitative precision is 100% for the retropalatal level and 95.6% for the retrolingual level with a tolerance of 0.5 cm(2) between the two methods. The absolute mean of the difference between the two methods of measurement is 0.08 cm(2) at the retropalatal level and 0.18 cm(2) at the retrolingual level. The agreement between the digital-imaging videoendoscopic and MRI measurements was 93.3% for the retropalatal level and 95.6% for the retrolingual level. Quantitative computer-assisted digital imaging is a reliable, cost-effective clinical method of upper airway evaluation in OSA patients. This method allows us to examine the dynamic and static morphology objectively, measure surgical outcomes of upper airway, opening up new avenues for OSA management.

Body Mass Index↗
PubMed2004

Auricular pseudocyst in the tropics: a multi-racial Singapore experience.

Endochondral pseudocyst of the auricle is an uncommon condition that affects predominantly Chinese males, with many reports studying this condition in homogenous Chinese populations. There have been few large-scale reports describing the features of this disease among the other Asian groups. In one of the largest series described to date, we report the epidemiological features, clinico-pathologic characteristics, and success of surgical treatment in 40 patients of different Asian groups presenting with pseudocyst of the auricle. Results showed a Chinese predominance (90 per cent), followed by Malays (five per cent) and Eurasians (five per cent). All had unilateral presentations apart from one patient. Most (55 per cent) presented within two weeks of auricular swelling. Few (10 per cent) had a history of trauma. The pseudocysts predominantly affected the concha (61 per cent). Surgery comprised excision of the anterior wall followed by local pressure application. Only 2.5 per cent had recurrence after surgery. These findings confirm earlier understood features of this disease while revealing some notable variations.

Adult↗
PubMed2002

A new method of evaluation of upper airway in patients with obstructive sleep apnoea--computer-assisted quantitative videoendoscopic analysis.

INTRODUCTION: Prospective study to quantitatively examine the static and dynamic changes of upper airways in patients with obstructive sleep apnoea (OSA) by engaging a new inexpensive clinical method which accurately evaluates the morphology of obstructive sites of upper airway. The aim was to minimise the subjective visual estimations and eliminate individual variations of the traditional method of nasopharyngoscopic assessment of upper airway. METHOD: Videoendoscopic (video-nasopharyngoscopic) examinations of upper airways of 15 patients were carried out with a calibrator inserted through the scope and placed at the levels of interest. Images of upper airways during quiet respiration, muller manoeuvre at erect and supine positions were obtained, digitalised and analysed by computers to generate the actual dimensions, surface areas and hence collapsibility of obstructive sites of upper airways. These measurements were validated by comparing videoendoscopic measurements (supine, quiet respiration) with upper airway magnetic resonance imaging (MRI) scans. We compared the area measurements of 30 videoendoscopic images with MRI scans of 15 patients at two levels (points above uvula and epiglottis) and calculated the accuracy percentage by examining the differences of surface areas of these two methods of measurement. The MRI scan measurements were used as standard, and the differences were presented as an accuracy percentage. RESULTS: The accuracy for the first level was 89.50% and the second level was 88.15%; the mean accuracy was 88.82%. The mean area of MRI was 1.50 cm2 (SD = 0.69) and the mean area of videoendoscopic images was 1.45 cm2 (SD = 0.64), with a correlation of 0.93 and a P value of less than 0.001. CONCLUSION: This new cost-effective and convenient clinical method of upper airway evaluation enables us to quantitatively and accurately examine the morphology of obstructive sites of upper airway, so that we could further research the pathophysiology of upper airway obstruction, engage the most appropriate treatment and provide accurate pre and postoperative assessments for patients with obstructive sleep apnoea.

Adult↗
PubMed2001

Effects of flow patterns on endothelial cell migration into a zone of mechanical denudation.

Vascular endothelial cells (ECs) in vivo are subject to different flow conditions due to the variation in vessel geometry. The aim of this study is to elucidate the effects of different flow conditions on EC monolayer migration into a mechanically denuded zone and their underlying mechanisms. Both laminar and disturbed flows significantly enhanced EC migration. EC migration speed was the fastest under laminar flow, which preferentially promoted directional EC migration from the upstream side of the wounded monolayer. C3 exoenzyme (a Rho inhibitor) inhibited EC migration under static and flow conditions, and markedly reduced the effects of flow on EC migration. These results indicate that flow promotes EC migration through the Rho signaling pathway. Genistein (a tyrosine kinase inhibitor) selectively retarded EC migration under disturbed flow, suggesting that tyrosine phosphorylation may play a role in EC migration under disturbed flow. This study has demonstrated that different flow patterns differentially affect EC monolayer migration into the denuded zone involving multiple mechanisms.

ADP Ribose Transferases↗
PubMed2001

Multiple level pharyngeal surgery for obstructive sleep apnoea.

The aim of the study is to evaluate the results of multiple level pharyngeal surgery in patients with moderate to severe obstructive sleep apnoea in Changi General Hospital, Singapore. 13 patients who failed non-surgical treatment underwent surgery which includes uvulopharyngopalatoplasty, genioglossal advancement and modified hyoid myotomy and suspension. Epworth sleepiness scale, Cephalometric analysis and Sleep study were performed pre- and post-operatively to evaluate the results. 76.9% of the patients achieved more than 50% reduction in AHI with post-operative AHI of less than 20. Cephalometric analysis showed an average of 5.2 mm increase in posterior airway space. All patients achieved improvement in Epworth sleepiness scale with an average improvement of 11.8 points. The mean follow-up period of the 13 patients is 12.6 months. Our preliminary results suggest that multiple level pharyngeal surgery is an effective option in the treatment of moderate to severe obstructive sleep apnoea.

Female↗
PubMed2000

Molecular mechanism of endothelial growth arrest by laminar shear stress.

This study was designed to elucidate the mechanism underlying the inhibition of endothelial cell growth by laminar shear stress. Tumor suppressor gene p53 was increased in bovine aortic endothelial cells subjected to 24 h of laminar shear stress at 3 dynes (1 dyne = 10 microN)/cm(2) or higher, but not at 1.5 dynes/cm(2). One of the mechanisms of the shear-induced increase in p53 is its stabilization after phosphorylation by c-Jun N-terminal kinase. To investigate the consequence of the shear-induced p53 response, we found that prolonged laminar shear stress caused increases of the growth arrest proteins GADD45 (growth arrest and DNA damage inducible protein 45) and p21(cip1), as well as a decrease in phosphorylation of the retinoblastoma gene product. Our results suggest that prolonged laminar shear stress causes a sustained p53 activation, which induces the up-regulation of GADD45 and p21(cip1). The resulting inhibition of cyclin-dependent kinase and hypophosphorylation of retinoblastoma protein lead to endothelial cell cycle arrest. This inhibition of endothelial cell proliferation by laminar shear stress may serve an important homeostatic function by preventing atherogenesis in the straight part of the arterial tree that is constantly subjected to high levels of laminar shearing.

Animals↗
PubMed1991

MEDLINE end-user survey: the University of Florida experience.

The University of Florida Health Science Center Library (UF-HSCL) surveyed MEDLINE end-user activities of the faculty from the six colleges which the UF-HSCL serves. A questionnaire was developed and sent to all faculty members. The Basic SAS program was used to analyze the collected data. This survey was intended to identify the users, the reasons for faculty members not being end users, the purpose for searching MEDLINE, the information retrieval methods, the level of end-user satisfaction, and the librarian's role in information retrieval activities. Many findings from this survey were in agreement with those of the 1988 study by the National Library of Medicine.

Attitude to Computers↗
PubMedDate not supplied

Measurement of orientation and distribution of cellular alignment and cytoskeletal organization.

Endothelial cells elongate and align with the direction of applied fluid shear stress. Previously, automated methods for analysis of cell orientation distribution have used Fourier- or fractal-based methods. We used intensity gradients in images of control and sheared endothelial cells to measure orientation distributions. Automated measurements of mean orientation and angular deviation compared favorably with manual measurements. There was a significantly greater angular deviation in images of control cells compared with sheared cells. Automated methods were also used to quantify organization of cytoskeletal fibers using the local angular deviation and a measure of the local coalignment of fibers called the coalignment ratio. The local angular deviation of microtubules and microfilaments was significantly smaller in sheared cells compared with control. The coalignment of cytoskeletal fibers was significantly greater in sheared cells. We conclude that image intensity gradients can be used rapidly, accurately, and objectively to measure cell orientation distributions and cytoskeletal filament organization.

Algorithms↗