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Biomedical subjects

J C Yap

Publications and source records attributed to J C Yap.

At least 19 recordsLinked to original sources
PubMed1998

A comparison of three fluid-vasopressor regimens used to prevent hypotension during subarachnoid anaesthesia in the elderly.

We aimed to compare the efficacy of fluid preloading with two recently recommended fluid-vasopressor regimens for maintaining blood pressure during subarachnoid anaesthesia in the elderly. Sixty elderly patients requiring surgery for traumatic hip fractures received subarachnoid anaesthesia using 0.05 ml/kg of 0.5% heavy bupivacaine. Hypotension, i.e. systolic arterial pressure < 75% of baseline, was prevented or treated by: A--normal saline 16 ml/kg plus intravenous ephedrine boluses (0.1 mg/kg); B--normal saline 8 ml/kg plus intramuscular depot ephedrine (0.5 mg/kg); or C--Haemaccel 8 ml/kg plus metaraminol infusion. Systolic arterial pressure and heart rate were recorded using custom-written computer software (Monitor, version 1.0). Systolic arterial pressure decreased in all groups after five minutes (P < 0.001). Decreases were greatest in group A (P < 0.05). Heart rate increased by 7% group A and decreased by 9% in group C (P < 0.05). During the first hour, hypotension was present for 47%, 25% and 20% of the time in groups A, B and C respectively and overcorrection of systolic arterial pressure occurred in 19% of the time in group C. We conclude that treatment A was inadequate in preventing hypotension. Treatments B and C were more effective but were associated with an increased heart rate and overcorrection of systolic arterial pressure respectively.

Aged↗
PubMed1998

Effect of oxygen on breathing irregularities during haemodialysis in patients with chronic uraemia.

Hypoxaemia and breathing irregularities have been shown to occur during haemodialysis in patients with chronic renal failure. This study examined the role of hypoxia in the genesis of the irregular breathing during haemodialysis. The ventilatory patterns using respiratory inductance plethysmography and arterial blood gases were studied in seven males with chronic renal failure on long-term haemodialysis. The study was carried out before and during dialysis on one day without (D1) and another day with intranasal oxygen at 4 L x min(-1) (D2). On D1, mean (SD) arterial oxygen tension (Pa,O2) fell 1.9 (0.9) kPa (p<0.001) and mean minute ventilation (V'E) fell 1.9 (1.1) L x min(-1) (p<0.01) during dialysis. The arterial carbon dioxide tension (Pa,CO2) did not show a significant decrease (4.7 (0.2) kPa before and 4.6 (0.2) kPa during dialysis). Cumulative number of apnoeas was 64 and the coefficients of variation (COV) of respiratory frequency (fR) and tidal volume (VT) were 29.6 (11.9) and 38.2 (11.9)%, respectively. On D2, mean Pa,O2 remained stable (20.4 (4.1) kPa before, 21.3 (4.1) kPa during dialysis). There was no significant change in mean V'E (6.4 (0.9) L x min(-1) before, 5.5 (0.5) L x min(-1) during dialysis). Pa,CO2 decrease was not significant but the fall was greater (4.8 (0.1) kPa before, 45 (0.5) kPa during dialysis). Cumulative number of apnoeas was 94 and the COVs offR and VT were 35.8 (5.1) and 40.5 (11.3)%, respectively. Oxygen administration did not significantly affect the haemodialysis-induced changes in ventilation and breathing pattern, despite a significant protective effect from the fall in arterial oxygen tension. It was concluded that the fall in arterial oxygen tension is not the main determinant of breathing irregularities during haemodialysis.

Adult↗
PubMed1998

The obstructive sleep apnoea syndrome--experience of a referral centre.

OBJECTIVE: The aims of this study were: (i) to document the presence and severity of obstructive sleep apnoea (OSA) in patients who complained of heavy snoring and other symptoms suggestive of the OSA syndrome; (ii) to examine the correlation between the clinical and polygraphic findings, and (iii) to document the efficacy and compliance of nasal continuous positive airway pressure (CPAP) among these Asian snorers with OSA. METHODS: We analysed our clinical and nocturnal polysomnographic data between January 1986 and December 1995 for physician-referred patients who had complained of snoring and other symptoms suggestive of OSA. RESULTS: A total of 277 diagnostic studies were performed of which 145 (52%) were positive to OSA. For studies performed in the last 2 years (n = 125), 72 of the 125 were positive for OSA. Anthropometric data was not discriminative between the OSA positive snorers and the OSA negative snorers. We found that hypertension and choking were the most significantly related to OSA, conferring a 7 and 4 times relative risk respectively. Nasal CPAP eliminated snoring, apnoeas and oxygen desaturations completely in almost all cases and there were only minor mask-related side effects. CONCLUSION: OSA may not be uncommon among Asian snorers. Of the major traits for OSA risk among our local population, a history of hypertension and reports of nocturnal choking were the most significantly related. We have also shown that nasal CPAP is safe and effective among our local snorers and should be considered a first-line treatment for OSA.

Adult↗
PubMed1995

Rapid application development in small unit settings.

Small units with specialised functions often have difficulty in developing information systems because of their unique and dynamic requirements, the smallness of their applications relative to the large inter-organisational networks, and the sheer numbers of such units, especially in government. Personal experience with the difficulty of establishing a suitable information system has led to the development of a methodology for endusers to develop their own applications with only the guidance of information technology professionals (ITPs)--here entitled 'Small Unit Enduser Rapid Application Development' or SERAD. A data base management system (DBMS) is used to manage data about 'focal objects' with status flags and queries/views at interface points through UDA (UserAction, DataEntry, ApplicationAction) cycles. The system which permits data entry almost immediately, not only eventually creates a full application, but also trains endusers in the process. The methodology leads ITPs and ensuers through a sequence of exercises in systems analysis, tailored to minimise the time and effort input of ITPs despite the relative lack of IT training and concepts in endusers, with a view to rapidly creating dynamic, robust and sound information systems.

Computer Communication Networks↗
PubMed1995

Effects of posture on respiratory mechanics in obesity.

Increased abdominal mass in obesity should enhance normal gravitational effects on supine respiratory mechanics. We have examined respiratory impedance (forced oscillation over 4-26 Hz applied at the mouth during tidal breathing), maximum inspiratory and expiratory mouth pressures (MIP and MEP), and maximum effort flow-volume curves seated and supine in seven obese subjects (O) (mean age 51 yr, body mass index 43.6 kg/m2) and seven control subjects (C) (mean age 50 yr, body mass index 21.8 kg/m2). Seated mean total lung capacity was smaller in O than in C (82 vs. 100% of predicted); ratio of functional residual capacity (FRC) to total lung capacity averaged 43% in O and 61% in C (P < 0.01). Total respiratory resistance (Rrs) at 6 Hz seated was higher in O (4.6 cmH2O.l-1.s) than in C (2.2 cmH2O.l-1.s; P < 0.001); total respiratory reactance (Xrs) at 6 Hz was lower in O than in C. In C, on changing to the supine posture, mean Rrs at 6 Hz rose to 2.9 cmH2O.l-1.s, FRC fell by 0.68 liter, and Xrs at 6 Hz showed a small fall. In O, despite no further fall in FRC, supine Rrs at 6 Hz increased to 7.3 cmH2O.l-1.s, and marked frequency dependency of Rrs and falls in Xrs developed. Seated, MIP and MEP in C and O were similar; supine there were small falls in MEP and maximum expiratory flow in O. The site and mechanism of the increase in supine Rrs and reduction in supine Xrs and the mechanism maintaining supine FRC in obesity all need further investigation.

Airway Resistance↗
PubMed1995

Evaluation of the efficacy of sequential intravenous-oral administration of pefloxacin in community-acquired lower respiratory tract infections in patients with underlying conditions.

We studied the efficacy of sequential intravenous-oral pefloxacin therapy in community-acquired lower respiratory tract infection in 24 patients with one or more underlying conditions. Twenty-eight patients were enrolled into the study but only 24 patients were evaluated. There were 16 males and 8 females with a mean age of 66.9 +/- 11.2 years (mean +/- SD, range 46 to 87 years). The underlying conditions present were bronchiectasis, chronic obstructive lung disease and diabetes mellitus. Patients who were older than 70 years but without any underlying condition were also enrolled. All received 4 days of intravenous pefloxacin 400 mg twice a day followed by oral pefloxacin 400 mg twice a day for another 10 days. Assessment of success was based on clinical, microbiological and radiological improvement. Pefloxacin produced 79.2% clinical cure rate. Another 8.3% showed improvement. Pefloxacin was well tolerated. There were few adverse effects and none of the patients required a change of antibiotic. Pefloxacin was an effective and well tolerated treatment for respiratory tract infection and had the advantage of broad in-vitro antibacterial activity, twice daily dosing and sequential availability in an intravenous and oral formulation.

Administration, Oral↗
PubMed1994

Effect of induced bronchoconstriction on nasal airflow resistance in patients with asthma.

1. Reflex bronchial changes have been demonstrated after nasal stimulation in both man and experimental animals. The existence of a pulmonary-nasal reflex is less established. We have examined whether induced narrowing of the intrathoracic airways leads to increases in nasal airflow resistance (Rnaw) in patients with asthma. 2. We have used a non-invasive forced oscillation method to measure total respiratory resistance (Rrs) at 8 Hz during tidal breathing sequentially via the nose (Rrs, na) and via the mouth (Rrs, mo) and derived Rnaw by subtracting Rrs, mo from Rrs, na. We examined whether changes in Rnaw occurred when increases in Rrs, mo were induced by inhaling histamine aerosol via the mouth with the nose occluded in 11 patients with stable, mild asthma (six males, age 28.1 +/- 2.1 years, forced expiratory volume in 1 s 97 +/- 6% of predicted, means +/- SEM). Six of the patients had a history of rhinitis. The patients were first challenged with doubling concentrations of histamine via a dosimeter to establish the dose which reduced the forced expiratory volume in 1 s by > or = 20%. Two hours later when the forced expiratory volume in 1 s had returned to baseline, they were challenged with saline and again 2 h later with the concentration of histamine that had earlier caused a > or = 20% fall in the forced expiratory volume is 1 s. 3. Between 0.5 and 10 min after histamine inhalation, a sustained increase in Rrs, mo was achieved with mean increases averaging 68-77% above baseline over this period (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

A case of occupational asthma due to barley grain dust.

We report a case of occupational asthma due to barley grain dust, species Hordeum Vulgare L, in a 32-year-old storeman of a trading company's department that dealt with packaging of flour, barley and peanuts. He developed immediate symptoms of sneezing, cough and dyspnoea on exposure to barley only. These symptoms showed work relationship. He became asymptomatic after his transfer to another department dealing with sales only. Bronchial provocation testing to the barley confirmed the diagnosis.

Adult↗
PubMed1994

A case of late dumping syndrome.

We report a case of late dumping syndrome in a 49-year-old lady who had partial gastrectomy for bleeding peptic ulcer 11 years ago. She presented with unexplained syncopal attacks which did not have any apparent relationship to meal or posture. An unusual reaction to oral glucose tolerance test ordered by her gynaecologist who was seeing her for uterine fibroid led to the diagnosis. Late dumping syndrome was confirmed by a repeat oral glucose tolerance test. At the second hour of the test, she developed hypoglycaemic coma with a blood glucose level of 50 mg/dL and a hypocount of 47 mg/dL. She regained full recovery after dextrose infusion which raised the hypocount to 123 mg/dL. The dizzy spells and syncopal attacks disappeared with dietary adjustment.

Diagnosis, Differential↗
PubMed1992

A case of primary diffuse tracheobronchial amyloidosis treated by laser therapy.

We report a case of primary diffuse tracheobronchial amyloidosis in a 72-year-old lady who presented with a long history of recurrent cough, dyspnoea, wheezing, haemoptysis and chest infection. She was treated successfully with three sessions of laser therapy. There were improvements in both clinical symptoms and measurements of airway obstruction. Bronchodilators and oral prednisolone were not required after treatment.

Amyloidosis↗
PubMed1991

Occupational asthma in Singapore--a review of cases from 1983 to 1990.

One of the newer occupational diseases in Singapore is occupational asthma. As on 31 December 1990 there were 35 confirmed cases of occupational asthma in the official statistics on occupational disease. We report in this paper our observations and experience based on these cases. The problem of under-reporting and the importance of early diagnosis are discussed.

Adolescent↗
PubMed1990

Waldenstrom's macroglobulinemia presenting with pleuropulmonary and gastric manifestations.

A case of Waldenstrom's macroglobulinemia is reported in which the main clinical presentation was related to pulmonary infiltrations and pleural effusion. Serum protein studies demonstrated the characteristic monoclonal increase in immunoglobulin M (IgMK). Pleural and percutaneous lung biopsies showed dense lymphocytic infiltration. Gastric biopsy also showed focal atypical lymphoid hyperplasia. There was good clinical and radiological response to treatment with chlorambucil and prednisolone.

Aged↗
PubMed1990

Occupational asthma due to spot-welding.

A case of occupational asthma from fumes due to spot-welding is described. The hazards from resistance welding have been considered minimal as compared to other types of welding. This paper illustrates the possible hazards of occupational asthma among welders including those doing spot-welding. It also illustrates the difficulties encountered in identifying the specific causative agent in such cases.

Adult↗
PubMed1990

The effect of fresh orange juice on bronchial hyperreactivity in asthmatic subjects.

We studied 16 mild stable asthmatic subjects to determine if orange juice increases nonspecific bronchial hyperreactivity (NSBH). In 9 subjects, bronchial responsiveness to histamine was assessed before and after water ingestion on the control day, and orange ingestion on a consecutive day. The mean (+/- SD) ratio of log10 PD20 FEV1 after water: log10 PD20 FEV1 before water (1.00 +/- 0.13) was not significantly different from the mean (+/- SD) ratio of log10 PD20 FEV1 after orange: log10 PD20 FEV1 before orange (0.97 +/- 0.12). To avoid the possibility of histamine tachyphylaxis, 7 subjects participated in a second protocol in which histamine PD20 FEV1 was determined on a control day (geometric mean 0.11 mg.) and again two days later, thirty minutes after ingestion of orange juice (geometric mean 0.06 mg). There was no significant difference in the PD20 FEV1 (p = 0.344). Our data show that ingestion of fresh orange juice per se did not heighten NSBH in our subjects. (PD20 FEV1 is the dose of histamine required to produce a twenty percent fall in forced expiratory volume in one second [FEV1]).

Adolescent↗
PubMed1990

The breathing patterns in Chinese and Indian adult males in the supine posture.

The breathing patterns in the supine posture during inspiration from functional residual capacity (simulating the "liver palpation" manoeuvre) were studied in two groups of young adult male Chinese and Indians with each group comprising 30 subjects. Both groups were matched for age, height and weight. Although the findings did not reach a statistically significant level, Indian subjects were found to breathe more with their abdomen compared to the Chinese during the manoeuvre. The two groups behaved similarly when they breathed with increasing amplitude from their resting tidal volume to full inspiratory capacity. There was also no difference between the two groups when they performed the total lung capacity manoeuvre.

Adult↗
PubMed1983

Clinical evaluation of a depth electroencephalography electrode.

Stereo depth electroencephalography (EEG) is of proven benefit in lateralizing and localizing seizure origin in select cases of epilepsy. There are potential hazards and technical considerations inherent with depth EEG, however, that have limited the general applicability of this technique. A new depth EEG electrode with materials and design features that facilitate safe insertion and artifact-free recording has been developed. The design features and technique for inserting the electrode are described. The electrode was evaluated during 2600 hours of implantation and recording in seven patients. With the use of stereotactic techniques, the electrode could be positioned accurately within precise anatomical landmarks such as the amygdaloid nucleus and the hippocampus. After insertion, no hemorrhage or edema was detected along the electrode tracts by third generation computed tomographic scanning. There was no evidence of pyrogenicity or infection. Electrode migration was not observed. A large electrical field could be sampled because of the relatively large surface of the cylindrical depth electrode contacts.

Electrodes, Implanted↗