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Biomedical subjects

B Y Lee

Publications and source records attributed to B Y Lee.

At least 73 records · Page 4Linked to original sources
PubMed1990

In vivo reflectance of blood and tissue as a function of light wavelength.

Light reflectance from soft tissue has been utilized in noninvasive clinical measurement devices such as the photoplethysmograph and the reflectance pulse oximeter. Incident light on the skin travels into the underlying layers and is in part reflected back to the surface. This paper describes the reflectance of light from in vivo tissue for wavelengths in the range from 420 to 940 nm, based on photon diffusion theory and on experimental results from studies of 17 subjects. The results show a minimum reflectance and a peak sensitivity to the blood pulsations in the wavelength range from 510 to 590 nm. Skin pigmentation is seen to attenuate reflectance rather than altering the character of the modulation spectra. Based on the model introduced in this paper, the dependence of modulation spectra on mean blood fractional volume as well as wavelength is also described theoretically, and corroborated by further experimental data at 570 and 630 nm. At these latter wavelengths, the signal-to-noise ratio was calculated for the blood volume pulsation signal in the presence of physiological noise. The median for calculated ratios of reflectance modulation by blood pulsation and ratios of signal to noise between the two wavelengths were 13.1 and 7.5, respectively, for 93 sites in nine subjects. These results are seen to be consistent with the theory.

Blood Volume↗
PubMed1990

Paraplegic pressure sore frequency versus circulation measurements.

Paraplegic subjects (N = 34) were examined to determine the association of pressure sore history with respect to ankle pressure ratio and buttocks cutaneous plethysmographic harmonic persistence. No relationship was found between pressure sore history and ankle pressure ratio. No significant difference in ankle pressure ratios exists for those who have a pressure sore history as compared to those who have not experienced a pressure sore in 5 years. Those subjects with a diminished buttocks circulation harmonic persistence are more likely to have experienced one or more pressure sores than those subjects with normal circulation characteristics. A Poisson distribution analysis of multiple pressure sore occurrence suggests that repeated pressure sores are unlikely to arise as the result of chance.

Ankle↗
PubMed1990

Monitoring skin fluorescein delivery independent of skin pigmentation.

This study evaluated two changes in fluorometric assessment of fluorescein dye delivery: (1) monitoring the proportional, rather than the absolute, increase above the preinjection background reading at each site to obviate the effect of skin color and (2) employing gradual means of dye administration to facilitate monitoring uptake kinetics and to lessen the likelihood and severity of histamine-mediated reactions. In 15 beagles, background and postdye readings were obtained with the fiberoptic fluorometer at 27 pairs of matched light- and dark-skin sites of intact perfusion. After dye administration, the absolute increase in fluorescence at light sites averaged more than twice (approximately 225%) that at dark sites. However, the newly introduced proportional increase (PI) was independent of pigmentation. The PI of comparably perfused light and dark sites differed by an average of 3.9% (p greater than 0.05 for difference between PIdark and PIlight). This consistency was maintained after each of three methods of fluorescein administration. After the color independence of the PI was established, its relation to perfusion was assessed in nine 3 X 12 cm pedicle flaps of varied pigmentation. Background fluorometric readings were obtained at eight sites along the longitudinal axis of each flap. Dye was administered as a 20-minute 0.25 mg/kg/min infusion. The PI clearly delineated gradations in perfusion, correlating highly with more time-consuming kinetic indexes and accurately predicting viability. The pedicle row, last viable row (V1), and first nonviable row (N1) had mean PI values of 10.5 +/- 4.5, 4.2 +/- 2.6, and 0.1 +/- 0.1, respectively, at 25 minutes after the start of infusion (p less than 0.05 for pedicle vs V1, pedicle vs N1, and V1 vs N1).

Animals↗
PubMed1989

The optimal dose of atropine via the endotracheal route.

Fifty ASA class I or II patients, undergoing general or gynecological surgery under general anesthesia with endotracheal intubation, were randomly divided into five groups. Group I received 10 ug/kg atropine intravenously, group II to V received 10 ug/kg, 20 ug/kg, 30 ug/kg, 40 ug/kg, respectively via endotracheal route through an epidural catheter. All were given five manual deep breaths after the injection of atropine. The maximum increase in heart rate (MIHR) and the time to maximum heart rate (TMHR) were evaluated. There was no marked MIHR in group II. Group III had a MIHR similar to that of group I (17.5/min vs 20/min, p greater than 0.05), but had a longer TMHR than group I (120 sec vs 82.5 sec, p less than 0.005). Groups IV and V had greater MIHR than group I (28.7 and 29.5 vs 20/min, p less than 0.005), and a TMHR similar to that of group I (85 and 90.2 vs 82.5 sec, p greater than 0.05). For emergency procedures, if atropine must be given without an intravenous catheter, 30 ug/kg or more given endotracheally can achieve an effect comparable to that of 10 ug/kg given intravenously.

Adult↗
PubMed1989

Constant infusion fluorometry to predict flap survival.

Prediction of surgical flap survival in a dog model was evaluated by using the technique of fluorometry. The model provides a graded variation of flap ischemia with tissue necrosis occurring at the distal end. The indicator sodium fluorescein was administered via the saphenous vein at a constant infusion rate for 20 minutes. Quantitative fluorescence measurements were obtained with surface illumination of the flap at 132 sites for 15 flaps in the five animals. Wash-in slopes and wash-out clearances, both measures of tissue perfusion, were compared with the survival of flap regions observed at seven days. The sensitivity and specificity of fluorometric wash-in and wash-out measurements were compared in their ability to predict flap survival. The study showed sensitivities of 100% and 95% and specificities of 97% and 86%, respectively for the two methods. The wash-in procedure with constant infusion may be preferable to the wash-out technique since it requires less time to complete. In addition, it avoids bolus injections thus reducing the risk of anaphylactoid reactions.

Animals↗
PubMed1987

Effect of lumbar sympathectomy on muscle blood flow: distribution of perfusion measured by hydrogen clearance in skeletal muscle.

Measurements of local tissue blood flow using a technique of hydrogen clearance were used to examine the effect of lumbar sympathectomy on skeletal muscle blood flow. Polarographic recordings on 25 hydrogen desaturations were obtained with platinized platinum electrodes. Lumbar sympathectomies were done on five canines leaving the contralateral limb as a control. The hydrogen clearance data were modeled with biexponential curves: the initial rapid component and the second slow component yielded a weighted average perfusion through tissue. Average volumetric blood flow in the control limb was 6.08 +/- 0.45 ml/min/100 g tissue while the sympathectomized limb averaged 9.54 +/- 0.61 ml/min/100 g tissue (p less than 0.005). Average blood flow increases ranged from 33 to 83 percent in the sympathectomized limb over the control limb. This significant increase in muscle blood flow following lumbar sympathectomy, if of prolonged duration, may be cause for re-evaluation of the role of sympathectomy in the management of arteriosclerotic occlusive disease.

Animals↗
PubMed1986

Echocardiographic demonstration of outlet strut fracture of a Björk-Shiley mitral prosthesis.

Fracture of the outlet strut of the Björk-Shiley mitral valve prosthesis has been recognized with increasing frequency, prompting recall of unimplanted valves manufactured before March 1982. Presenting dramatically with acute severe pulmonary edema and low cardiac output, strut fracture is frequently a fatal complication. This case report documents the first reported echocardiographic demonstration of occluder disc dislodgment secondary to outlet strut fracture with survival after emergency valve replacement.

Adult↗
PubMed1985

Pentoxifylline treatment of moderate to severe chronic occlusive arterial disease.

A pilot study of the effects of pentoxifylline in 19 patients with moderate to severe chronic occlusive arterial disease (COAD) is described. The severity of disease was assessed by the degree of limitation in the walking distance on the flat surface (less than 100 m), the absence of peripheral pulses on palpation, the diminished Doppler tibial/brachial pressure (the ischemic index) at rest, and by contrast arteriography, when available. After a 2-week washout phase, all subjects received pentoxifylline (1200 mg/day) in an open-label manner for a total of 12 weeks. Twelve of the nineteen patients showed a definite increase in exercise tolerance by the end of the study, with a concomitant reduction in ischemic symptoms. All except 3 patients felt they had derived benefit from the medication. In contrast to the clear improvements in walking distance and symptoms, only small effects on noninvasive vascular laboratory measurements were noted. Platelet aggregation, induced by ADP, epinephrine, and collagen, gradually decreased over the study period. Pentoxifylline appears to be useful in the medical management of patients with moderate to severe chronic occlusive arterial disease; future controlled trials in such patients are now justified.

Aged↗
PubMed1985

Assessment of nutritional and metabolic status of paraplegics.

Nutritional and metabolic assessment using anthropometric, biochemical, immunological, and indirect calorimetric techniques was performed on 17 healthy paraplegic males with a mean age of 44.2 +/- 14.6 years and mean duration of injury of 17.8 +/- 12.3 years. Significant differences in energy expenditure were observed; only 29.4 percent were normometabolic [measured resting energy expenditure: (MREE) 90-110 percent of predicted resting energy expenditure (PREE)], 35.3 percent were hypermetabolic (MREE greater than 110 percent of PREE) and 35.3 percent were hypometabolic (MREE less than 90 percent of PREE). Obesity (weight greater than 110 percent ideal body weight) was maximum in hypometabolic patients (83.3 percent) due to the imbalance between caloric intake and energy expenditure (p less than 0.05). None of the patients had normal values for all four objective measurements of nutritional assessment (albumin, transferrin, total lymphocyte count, and cutaneous hypersensitivity). Mild malnutrition was evidenced in 47 percent of patients; 53 percent of patients demonstrated some index of moderate malnutrition. We conclude that nutritional therapy based on measurements of energy expenditure instead of predictive equations will benefit these patients. A larger long-term study is needed to determine the ideal predictive measurements of nutritional assessment with their optimal cutoff values applicable to the spinal cord-injured patient.

Adult↗
PubMed1984

Blue digit syndrome: urgent indication for digital salvage.

The sudden onset of digital ischemia due to microembolization from a proximal source (the blue digit syndrome) requires immediate attention because not only the digit, but also the entire extremity, may be at risk. In our experience, 11 patients with the blue digit syndrome were encountered. Treatment consisted of eradication of the proximal embolic source followed by lumbar sympathectomy in four patients, direct arterial surgery alone in five patients, and lumbar sympathectomy alone in two patients. The addition of lumbar sympathectomy was beneficial as it provides an additional increase in blood flow and tissue perfusion over and above that due to direct arterial surgery alone. Our experience indicates that the benefits of lumbar sympathectomy leads to enhancement of healing of pregangrenous lesions and digital salvage.

Aged↗
PubMed1984

Management of compartmental syndrome. Diagnostic and surgical considerations.

Compartmental syndrome is a condition in which swelling within a closed anatomic space increases the intracompartmental pressure to compromise the circulation and function of tissue within that space. Unless this condition is recognized early and treated by prompt surgical decompression, permanent neuromuscular deficits may result. In those instances in which early clinical evidence of this syndrome is difficult to assess, monitoring of intramuscular pressures may be valuable adjunct in the clinical evaluation of patients at risk for this syndrome. The association of compartmental syndrome with a wide variety of circumstances and the importance of an early diagnosis make it essential that all physicians be familiar with this condition. As physician awareness and recognition of this condition increase, the complications associated with it can be greatly reduced.

Adult↗
PubMed1984

Pentoxifylline in the treatment of intermittent claudication of the lower limbs.

Pentoxifylline, a methyl xanthine analogue was evaluated for treatment of intermittent claudication in a double-blind placebo controlled parallel group study in seven centers in the United States. Tests were performed on 128 cases, including 42 who took pentoxifylline (600 mg by mouth daily, increased stepwise to 1200 mg daily at the end of one month) and 40 who took placebo for 24 weeks. Twenty-five patients on pentoxifylline and 21 on placebo were dropped from the study for reasons unrelated to the drug. Walking ability on a treadmill was increased significantly after 2 weeks and remained so throughout the study in the pentoxifylline vs. the placebo group. Ability to walk until first experiencing intermittent claudication was a more sensitive index than the maximum ability to walk. The drug did not cause changes in blood pressure or in heart rate. Other than mild nausea, there were no significant side effects.

Clinical Trials as Topic↗
PubMed1984

Loa loa: ocular filariasis in an African student in Missouri.

Ocular filariasis was observed in an African student living in Missouri. The adult female Loa loa worm was seen migrating under the conjunctiva. There was 34% eosinophilia and a high microfilaremia. The patient was successfully treated with diethylcarbamazine (Hetrazan) with no appearance of allergic manifestations.

Adult↗
PubMed1984

Skin stress and blood flow in sitting paraplegic patients.

Sitting paraplegic subjects, tested on a hard seat at a location 2 to 3cm lateral to the ischial tuberosities, develop roughly the same median pressure values (range 52 to 60mmHg) as groups of normal subjects and hospitalized geriatric patients. However, median paraplegic and hospitalized geriatric shear values are roughly three times median normal values. Median rates of pulsatile skin blood flow volumes for sitting paraplegic subjects, while roughly equal to those of hospitalized geriatric subjects, are only one third those of comparable normal subjects.

Adult↗
PubMed1983

Effect of suture technique on blood velocity waveforms in the microvascular anastomosis of autogenous vein graft.

In using autogenous vein grafts in microvascular surgery, maintenance of compliance at the site of anastomosis is of importance in achieving patency. Using high-frequency, 20 MHz, pulsed Doppler ultrasonography to monitor blood flow velocity through the vein graft, we have evaluated the effects of continuous and interrupted suture technique on anastomotic compliance in vessels less than 1.5 mm in diameter. In 15 dogs, 15 procedures of each technique, using the continuous technique in one limb and the interrupted technique on the contralateral limb, patency rates for both techniques, documented by arteriography, are 100% at a mean follow-up of 11 weeks. There were no significant differences in the blood velocity profile and pulsatility proximally, distally, and at the graft site between continuous and interrupted technique. This study confirms the suggestion that autogenous vein graft has sufficient elasticity to maintain normal arterial blood velocity waveforms.

Animals↗
PubMed1983

Lumbar sympathectomy for toe gangrene. Long-term follow-up.

We carried out a retrospective review of 45 patients (50 limbs) with toe gangrene not amenable to direct arterial surgery, and thus managed by lumbar sympathectomy alone. Follow-up data regarding toe salvage, limb salvage, and limb loss were compiled. At 5 and 8 year follow-up cumulative limb salvage was 71 percent and cumulative toe salvage was 51 percent. The presence of diabetes did not significantly influence limb or toe salvage. Mortality during the immediate postoperative period was 2 percent. In the majority of patients with digital gangrene who are not amenable to arterial surgery, lumbar sympathectomy is of benefit for salvaging the limb and the toes.

Aged↗