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Biomedical subjects

M Kothari

Publications and source records attributed to M Kothari.

33 records · Page 2Linked to original sources
PubMed1996

Surface geometry of retrieved McKee-Farrar total hip replacements.

A coordinate measurement machine was used to determine the surface geometry of 22 retrieved McKee-Farrar total hip replacements. The radial clearance of each acetabular cup-femoral head pair was computed to see whether there was potential for hydrodynamic lubrication. The surface geometry was used to estimate the volumetric wear for the acetabular cup and the femoral head, and to assess whether those prostheses that had the potential for fluid film lubrication also displayed lower wear. The volumetric wear rate for each prosthesis was estimated by dividing the volumetric wear by the corresponding service life. Two distinct wear patterns were seen on the femoral head. Prostheses displaying polar wear on the femoral head showed significantly greater service lives than those displaying non-polar wear. Although several prostheses had clearances that provided for the possibility of hydrodynamic lubrication, no correlation could be found between clearance and the measured wear.

Biomechanical Phenomena↗
PubMed1996

Clinical profile of patients with epileptic and nonepileptic seizures.

Epileptic seizures (ES) and nonepileptic seizures (NES) often coexist in patients with treatment-refractory seizures. There are few data on ictal features of these different seizure types in the same patient. We identified 20 patients with ES from a group of 99 NES patients (ES/NES) and compared this group with patients with only ES or NES. All 20 ES/NES patients developed NES after ES. Clinical features of NES clearly differed from ES in 18 of 20 cases. In patients with ES/NES their ES were similar to seizures in patients with only ES, and their NES were similar to spells in patients with only NES. ES/NES patients were similar to ES patients in electrodiagnostic and neuroimaging studies, and similar to NES patients in psychiatric interviews and inventories. The clinical manifestations of ES and NES in the same patient are usually different. Both types of events may be stereotypic and can be distinguished and characterized during video-EEG recording. Determining what events are more prevalent or disturbing is critical. Psychiatric and antiepileptic drug treatment may be provided accordingly.

Amnesia↗
PubMed1995

Presumed vestibular hemorrhage secondary to warfarin.

Hemorrhage secondary to anticoagulant therapy is well documented. We report a patient who presented with acute vertigo and unilateral deafness while on warfarin and was found to have a probable hemorrhage in the labyrinth, identified on MRI.

Aged↗
PubMed1995

Angioscopic evaluation of prolonged vs standard balloon inflations during coronary angioplasty. A randomized study.

UNLABELLED: To study the immediate effects of prolonged total balloon inflation during PTCA, 41 patients (44 lesions) with chronic stable angina were randomized for prolonged sequential inflations (three to five inflations of 3 to 5 min each, for a total duration of > or = 12 min, group 1, n = 20 lesions) or 'standard' sequential inflations (three to five inflations of < or = 1 min each, for a total duration of < or = 3 min, group 2, n = 24 lesions). The mean duration of total balloon inflation time was 958 +/- 129 s in group 1 vs 205 +/- 46 s in group 2. Results of angioplasty were assessed on both angiography and percutaneous transluminal coronary angioscopy performed immediately after the procedure. High quality imaging of the coronary lumen and lesion morphology was possible on angioscopy in all patients without any complications. Post-PTCA angiographic percent diameter stenosis was significantly less in group 1 compared to group 2: 26 +/- 10% vs 36 +/- 8% (P < 0.05). On angioscopy, flaps were seen in 16 patients in group 2, but in only six in group 1 (P < 0.02). There was no difference in the incidence of thrombi on angioscopy between the two groups (group 1: nine cases, group 2: 10 cases). Sensitivity of angiographic detection of flaps and thrombi was poor: 10% and 12% respectively. One patient in each group developed a longitudinal dissection, detected on both angiography and angioscopy. CONCLUSIONS: (1) prolonged sequential balloon inflations lead to less residual luminal stenosis after PTCA, with a decreased incidence of intimal flaps in comparison with standard inflations. (2) Post-PTCA transluminal coronary angioscopy is safe and offers better assessment of luminal effects of PTCA than angiography.

Adult↗
PubMed1994

[Effects of repeated and prolonged inflations on immediate angiographic results and complications of coronary angioplasty. Prospective and randomized study].

The effects of the duration of balloon inflation on the immediate and mid-term results of angioplasty were assessed in a randomized study initiated in June 1992. To date, 239 lesions in 224 consecutive patients were allocated randomly into 2 groups according to the duration of balloon inflation: short duration (123 lesions): 3 or 4 successive inflations, each < or = 1 mn, for a total duration < or = 3 min; long duration (116 lesions): 3 to 5 inflations, each of 4 to 5 minutes each for a total duration > or = 12 min. Patients with acute myocardial infarction, restenosis and lesions of bypass grafts were excluded. Stenosis (% of reduction of the internal diameter) was calculated with a digitalised Philips DCI system. Success was defined by < 50% residual stenosis in the absence of severe complications: death, emergency bypass surgery, infarction and extensive and/or occlusive dissection. The baseline clinical, haemodynamic and angiographic parameters of the two groups were comparable. The residual stenosis after angioplasty in the "short duration" group was 33 +/- 11% and 29 +/- 11% in the "long duration" group (p < 0.05). The primary success rate was 75% in the "short duration" compared to 89% in the "long duration" group (< 0.001). Angiographic dissection after angioplasty was observed in 38 cases in the "short" but only in 17 cases in the "long duration" group (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

A capacitance pressure sensor using a phase-locked loop.

We are using a Hercules (model #F4-4R, 100 psi) pressure sensor to measure the pressure between the foot and shoe. An interface circuit converts the capacitance change into voltage. Over the pressure range from 0 to 1300 kPa, the capacitance changes from 275 to 580 pF. A 555 timer circuit converts the capacitance into a frequency range from 30 to 63 kHz. A phase-locked loop (PLL) converts this frequency to voltage from 0 to 5 V, which is then filtered using a first-order, low-pass filter, having a corner frequency of 20 Hz to reduce the ripple to 10 mV. The sensor's hysteresis is about 8 percent at 40 degrees Celsius (C) and 12 percent at 20 degrees C. The sensor has a maximal nonlinearity of 8 percent and a worst-case nonrepeatibility of 7 percent. Its temperature coefficient is -0.147 percent per degree C. Its spatial sensitivity decreases nonlinearly from 1 to 0.17 from the center towards the periphery. The sensitivity of the system is 2.77 mV/kPa and the temperature drift is +0.53 percent per degree C. We monitor the pressure at 7 locations under each foot (the rear and the front heel, great toe, and 4 of the 5 metatarsal heads). A portable data-acquisition system permits continuous monitoring for 7 minutes. Test results for pressure distribution for normal walk and run are presented. Results are useful when studying normal and abnormal gait, and for possibly providing feedback (sensory substitution) to diabetic patients with insensate feet in order to help them dynamically adjust pressure distribution under their feet.

Biomechanical Phenomena↗
PubMed1975

Changes in total body composition during normal and diabetic pregnancy. Relation to oxygen consumption.

Serial changes in body composition during pregnancy have been measured in 5 normal and 2 diabetic women on controlled diets to compare with simultaneous measurements of oxygen consumption (V-O2). Total body water (TBW) was measured by D2O dilution, total body fat (TBF) calculated as 100-%TBW/0.732 and body cell mass (BCM) derived from total body 40K count by Moore's formula, BCM equals K-e times 8.33. Two normal subjects in caloric equilibrium lost 1.2 kg TBF, gained 5.5 kg TBW and 4.1 kg BCM. Two obese subjects in negative caloric balance lost 4.7 kg TBF, gained 7.3 kg TBW and 4.3 kg BCM. One subject on ad lib diet gained 7.7 kg TBF, 0.6 kg TBW, and 2.6 kg BCM. She continued to gain fat postpartum. Two diabetic subjects gained fat up to 28 weeks, lost it thereafter, and showed no net gain in BCM. Basal V-O2 correlated with BCM, while 24-hour resting V-O2 related to total body weight. It is concluded that fat storage in human pregnancy depends on food intake, as in the nonpregnant. BCM accumulation is independent of food intake, except protein, and depends on normal physiologic adjustments of pregnancy, which are upset by insulin lack in diabetes. The extra basal energy needs of gestation are determined by BCM acquisition, not total body weight.

Adipose Tissue↗
PubMedDate not supplied

Provocation of nonepileptic seizures by suggestion in a general seizure population.

Nonepileptic seizures (NES) are common and are often diagnosed at epilepsy centers by video-EEG recording of both spontaneous and suggestion-induced episodes, but no study has evaluated provocative testing in a general seizure population. We studied consecutive patients with a tentative diagnosis of epilepsy using saline provocation during video-EEG recording, suggesting that this could produce a typical seizure. Of 52 patients, 40% had no response, 23% had responses unlike their seizures, and 37% had typical episodes (positive test). Patients whose usual episodes resembled complex partial seizures (CPS) were more likely to have NES than were patients with a history of generalized tonic-clonic seizures (GTC). Of patients with positive provocations, the primary physician predicted NES in 68% of cases. This preliminary study suggests that NES are frequent in a general neurology setting, and that saline provocation is a sensitive method of identifying NES.

Adult↗