PubMed Health⌕ Search

Biomedical subjects

D M Choi

Publications and source records attributed to D M Choi.

8 recordsLinked to original sources
PubMed2001

Investigation of the human oesophagus as a new monitoring site for blood oxygen saturation.

Pulse oximeter probes placed peripherally may fail to give accurate values of arterial blood oxygen saturation (SpO2) when peripheral perfusion is poor. Since central blood flow may be preferentially preserved, the oesophagus was suggested as an alternative monitoring site. A reflectance oesophageal photoplethysmographic (PPG) probe and a multiplexed data acquisition system, operating simultaneously at two wavelengths and incorporating an external three-lead electrocardiogram (ECG) reference channel, has been developed. It has been used to investigate the suitability of the oesophagus as a possible monitoring site for SpO2 in cases of compromised peripheral perfusion. Oesophageal PPG signals and standard ECG traces were obtained from 16 anaesthetized patients and displayed on a laptop computer. Measurable PPG signals with high signal-to-noise ratios at both infrared and red wavelengths were obtained from all five oesophageal depths investigated. The maximum PPG amplitude occurred at 25 cm from the upper incisors in the mid-oesophagus. The measured pulse transit times (PTTs) to the oesophagus were consistent with previous measurements at peripheral sites and had a minimum value of 67 +/- 30 ms at a depth of 30 cm. There was broad agreement between the calculated values of oesophageal SpO2 and those from a commercial finger pulse oximeter.

Adult↗
PubMed2001

Diagnosis of hemophilia made after intraoperative bleeding during attempted penetrating keratoplasty in an elderly patient.

PURPOSE: To report an unusual case where the diagnosis of hemophilia was made after attempted penetrating keratoplasty in an elderly patient. METHODS: A 75 year old white male with a full-thickness corneal scar in the visual axis and a visually significant cataract OD was to undergo penetrating keratoplasty and cataract extraction with lens implantation for visual rehabilitation. There was no history of bleeding diathesis given. RESULTS: During placement of the Flieringa ring, a progressively enlarging 360 degrees subconjunctival hemorrhage was observed. Given the unusual bleeding,the procedure was aborted and the patientwas referred to the hematology service for further evaluation. Laboratory studies revealed a diagnosis of atypical hemophilia of mild severity. CONCLUSIONS: The initial diagnosis of hemophilia in any elderly patient is unusual. This case is even more unusual asthe diagnosis of a bleeding disorder was first considered after excessive subconjunctival hemorrhage developed during attempted penetrating keratoplasty.

Aged↗
PubMed2001

Fungal keratitis in a daily disposable soft contact lens wearer.

PURPOSE: To report the first case of fungal keratitis in a patient wearing daily disposable soft contact lenses. METHODS: Case Report. A 20-year-old white female in good health developed a corneal ulcer in her lefteye associated with daily disposable soft contact lens wear. There was no history of trauma to the left eye, and she denied overnight wear. Corneal scrapings were taken, and the patient was started on intensive tobramycin 14 mg/mL and cefazolin 50 mg/mL topical therapy for suspected bacterial keratitis. After 3 days of antibacterial therapy, the ulcer worsened. The cultures were negative as were the Gram stain and Gomori's methenamine silver stain. Initial cultures and stains were then repeated with the addition of a culture for herpes simplex virus. The developing clinical picture was suspicious for fungal keratitis. The patient was then started on intensive vancomycin 2%, natamycin 5%, and continued on fortified tobramycin. Three days after the second corneal scrapings were performed, a positive fungal culture was obtained for Fusarium sp. Vancomycin and tobramycin were then discontinued and amphotericin B 0.15% was added to natamycin 5% with the continuation of intensive topical therapy. RESULTS: The patient's keratitis was successfully treated with intensive double antifungal therapy. CONCLUSIONS: Infectious keratitis in daily disposable soft contact lens wear is an unusual occurrence. To our knowledge, there is no previous case of fungal keratitis occurring in patients wearing daily disposable lenses. This case emphasizes the importance of considering fungus in the differential diagnosis for keratitis even in daily disposable contact lens wearers.

Adult↗
PubMed1999

A system for investigating oesophageal photoplethysmographic signals in anaesthetised patients.

The monitoring of arterial blood oxygen saturation in patients with compromised peripheral perfusion is often difficult, because conventional non-invasive techniques such as pulse oximetry (SpO2) can fail. Poor peripheral circulation commonly occurs after major surgery including cardiopulmonary bypass. The difficulties in these clinical situations might be overcome if the sensor were to monitor a better perfused central part of the body such as the oesophagus. A new oesophageal photoplethysmographic (PPG) probe and an isolated processing system have been developed to investigate the pulsatile signals of anaesthetised adult patients undergoing routine surgery. Measurements were made in the middle third of the oesophagus, 25 cm to 30 cm from the upper incisors. The AC PPG signals are sampled by a data acquisition system connected to a laptop computer. The signals recorded correspond to infrared and red AC PPGs from the middle third oesophagus and the finger. Preliminary results from 20 patients show that good quality AC PPG signals can be measured in the human oesophagus. The ratio of the oesophageal to finger AC PPG amplitudes was calculated for the infrared and red wavelengths for each patient. The mean (+/- standard deviation) of this ratio was 2.9 +/- 2.1 (n = 19) for the infrared wavelength and 3.1 +/- 2.4 (n = 16) for the red wavelength. The red and infrared wavelengths used are appropriate for pulse oximetry and this investigation indicates that the mid-oesophagus may be a suitable site for the reliable monitoring of SpO2 in patients with poor peripheral perfusion.

Adult↗
PubMed1998

Intraocular light scatter in patients with choroideremia.

OBJECTIVE: This study aimed to evaluate the extent of intraocular light scatter in patients with choroideremia. DESIGN: Prospective case-control study. PARTICIPANTS: Twelve male patients with choroideremia who had predominantly minimal or no posterior subcapsular cataract (PSC) lens opacities and visual acuities of 20/40 or better and 30 age-similar control subjects with normal vision and no lens opacities were studied. INTERVENTION: Intraocular light scatter was measured using a van den Berg Straylightmeter. MAIN OUTCOME MEASURES: Visual acuities, letter contrast sensitivities, Goldmann visual fields using a II4e target, and straylight parameters were obtained for each patient. Lenses were assessed by slit-lamp biomicroscopy to determine whether there were PSC opacities. The degree of retinal pigment epithelial and choroidal degenerative changes was evaluated from color fundus photographs. RESULTS: Three of the patients with choroideremia who had clinically apparent PSC lens opacities showed an increase in intraocular light scatter. More notable was the fact that seven of the remaining nine patients who did not have any clinically apparent changes in the lens also had a considerable increase in the intraocular light scatter as compared to the control subjects. The relative elevations of the log straylight parameters of the patients with choroideremia, as compared to age-similar control subjects, were correlated significantly with their log visual field areas (r = -0.69, P < 0.05). CONCLUSIONS: Intraocular light scatter may be increased in patients with choroideremia, even in the absence of clinically observable PSC opacities. It is hypothesized that the increase in light scatter may be caused by changes in the posterior subcapsular region of the lens before the formation of frank PSC cataracts. The increased straylight could, at least in part, account for the disability glare reported by these patients.

Adult↗
PubMedDate not supplied

Soy fiber delays disease onset and prolongs survival in experimental Clostridium difficile ileocecitis.

Clostridium difficile colitis is a disabling complication in critically ill patients who commonly receive broad-spectrum antibiotics and liquid diets. To date, there is no experimental model specifically designed to investigate the effects of liquid diets on this type of colitis. The addition of fiber to liquid diets normalizes gut structure and improves absorptive function in selected conditions of intestinal dysfunction. The purposes of this study were the following: (1) to develop a reproducible model to examine the interaction of acute C difficile-induced colitis and liquid diets, (2) to determine whether the addition of soy fiber to a liquid diet improves disease, and (3) to investigate possible mechanisms of fiber-mediated disease improvement. Syrian hamsters were pair-fed with either a polymeric liquid diet or the same diet with 1.4% soy fiber for 10 days. Animals were given either clindamycin and C difficile (to produce ileocecitis), or equivalent volumes of saline. Mean survival time and systematic stool examinations for C difficile toxin positivity, liquidity, and percent water were performed to determine the effect of soy fiber on disease. Survival time was prolonged by 34% (p < .05), and C difficile toxin positivity and stool liquidity were significantly reduced (p < .05) with fiber. Additional animals were studied to determine possible mechanisms for improved survival in fiber-supplemented animals. Cecal histology, colonic water absorption, cecal microflora, and gastric to anus transit time were measured in these animals. Colonic water absorption and gastric to anus transit time were significantly increased (p < .05) and decreased (p < .05) with fiber, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗