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Biomedical subjects

H G Welch

Publications and source records attributed to H G Welch.

At least 91 records · Page 5Linked to original sources
PubMed1991

Should the health care forest be selectively thinned by physicians or clear cut by payers?

As the need to set limits in health care becomes more generally accepted, physicians and policymakers need to consider who can best decide how to allocate medical resources among patients. This commentary focuses on the two obvious candidates: payers and physicians. Although payer-based allocation has the advantage of allowing physicians to act strictly on behalf of their patients, it lacks precision and flexibility. Physician-based allocation places allocation decisions in the hands of individuals better positioned and better equipped to make choices that maximize health outputs. To preserve clinical freedom and minimize micromanagement of individual patients, physicians should expand their advocacy role beyond individual patients and recognize their responsibility to populations. In doing so, physicians would acknowledge that societal and patient interests differ and that health care is just one of many important social goods. For physicians willing to make these choices, five general guidelines are offered. Finally, mechanisms to encourage physician-based allocation are considered.

Cost Control↗
PubMed1991

Priority setting: lessons from Oregon.

The state of Oregon has developed a unique method to set priorities for health services. The method is based on a cost-utility formula but also incorporates public attitudes and values. Using an explicit process, the Oregon Health Services Commission has completed the ranking of 714 condition-treatment pairs. The background, methods, and criticisms of the Oregon approach highlight key questions for managers and physicians in other health services when they allocate limited resources.

Community Participation↗
PubMed1991

Comparing apples and oranges: does cost-effectiveness analysis deal fairly with the old and young?

This paper considers the role patient age plays in the type of outcome analysis most germane for policymakers: cost-effectiveness analysis. The magnitude of age bias is quantified and means to modify it are described. In particular, present value analysis (discounting) is demonstrated to markedly attenuate the effect of patient age on cost-effectiveness analysis. As the discount rate gets larger, the difference in potential "life-years" between old and young gets smaller and the age bias is minimized. However, relegating a decision about the importance of patient age to a decision about the discount rate seems inappropriate. Value judgments cannot be avoided; therefore, it is best that they be explicit.

Adolescent↗
PubMed1990

Survival of outpatients with Alzheimer-type dementia.

OBJECTIVE: To study the clinical course of Alzheimer-type dementia and those factors that might predict or influence the length of survival. DESIGN: A prospective cohort study. PARTICIPANTS: One hundred and twenty-six patients diagnosed with Alzheimer-type dementia were selected from among 200 consecutive outpatients evaluated for suspected dementia from 1980 to 1982. All 126 patients had at least 6 years of follow-up. SETTING: All patients were initially seen as outpatients at a university hospital. MEASUREMENTS AND MAIN RESULTS: Survival analysis was done using Kaplan-Meier estimates and the Cox proportional hazards model. The mean age at symptom onset was 73.9 years and at enrollment in the study, 77.6 years. The median survival from time of enrollment in the study was 5.3 years (range, 0.2 to 7.2+ years) and from symptom onset, 9.3 years (range, 1.8 to 16+ years). Dementia severity, as measured by the Mini-Mental State Examination (MMSE), was strongly associated with survival (P less than 0.001); the median survival of patients with scores of 18 or below was 3 years less than that of patients with scores above 18 (relative risk, 2.7; 95% CI, 1.6 to 4.4). Comorbid conditions and symptom duration were not related to survival. A multivariate analysis of age at symptom onset and of historical features showed that the combination of wandering and falling (relative risk, 2.1; 95% CI, 0.9 to 5.2) and the presence of behavioral problems (relative risk, 1.4; 95% CI, 0.7 to 2.9) at the time of evaluation appeared to adversely affect survival. CONCLUSIONS: Length of survival in patients with Alzheimer-type dementia is highly variable; severity of disease (not duration), the combination of wandering and falling, and behavioral problems are associated with shorter survival. Our findings, if confirmed, may provide prognostic information for families and professionals and suggest areas in which interventions to improve survival might be focused.

Accidental Falls↗
PubMed1989

Cost effectiveness of bone marrow transplantation in acute nonlymphocytic leukemia.

To compare the cost effectiveness of bone marrow transplantation and conventional chemotherapy, we evaluated the resources used in the care of adult patients with acute nonlymphocytic leukemia who were enrolled in a prospective trial and received induction chemotherapy at a single university hospital. Nineteen patients were subsequently treated with chemotherapy and 17 with transplantation. Cost accounting began with induction chemotherapy and extended over a five-year period. Costs were estimated by means of a resource-based, multivariate prediction model. The transplantation and chemotherapy groups had virtually equivalent use of resources (hospital days, laboratory tests, blood products, and radiologic and operative procedures) over five years, except for a 10-fold increase in the use of the intensive care unit for the patients who underwent transplantation (P less than 0.001). The total costs over five years were estimated at $193,000 per patient for transplantation and $136,000 per patient for chemotherapy (P = 0.02). At five years, the costs per year of life saved ("life-year") were nearly equal ($62,500 per life-year for transplantation vs. $64,000 per life-year for chemotherapy) because of the better rate of disease-free survival in patients who underwent bone marrow transplantation. We conclude that the cost effectiveness of bone marrow transplantation to treat acute nonlymphocytic leukemia compares favorably with that of chemotherapy and could be further enhanced if intensive care resources were used more selectively.

Adolescent↗
PubMed1988

A pictographic essay on blood and tissue oxygen transport.

This review describes the transport of oxygen from ambient air to mitochondria in the cells. Using simple equations and diagrams, the presentation illustrates the variables which determine the magnitude of each of the three major steps in the partial pressure of O2 along the passage, from: (i) ambient air to alveolar gas; (ii) arterial blood to venous blood; and (iii) capillary blood to tissue. The emphasis is on steps (ii) and (iii), and how they are modified from the normoxic case by ischemia, anemia, hypoxia, and increased VO2. The basic context of step (iii) is the Krogh model. This model, despite its limitations, is proposed as conceptually useful in analyzing whole-body or tissue O2 transport.

Atmospheric Pressure↗
PubMed1986

Effect of altered arterial O2 tensions on muscle metabolism in dog skeletal muscle during fatiguing work.

These experiments were conducted to determine whether changes in arterial O2 tension are related to changes in muscle metabolism during fatiguing contractions. Arterial and venous circulation to the gastrocnemius muscle (n = 8) was isolated, and the Achilles tendon was attached to a force transducer. Each muscle was electrically stimulated through the sciatic nerve for three 2-min periods of fatiguing contractions separated by 8 min of rest. The arterial O2 tensions were altered for each work period (mean PO2 = 44, 72, 391 Torr). Arterial and venous samples were drawn to measure lactate, O2 and CO2 concentrations (Van Slyke analysis), and [H+]. Muscle biopsies were taken to measure muscle [H+] (homogenate method) and lactate. Fatigue was evaluated as the decline in tension from peak initial tension. At the end of the contraction periods, values were significantly different (P less than 0.05) between the low arterial O2 tension and the high for flow [84 +/- 6 (mean +/- SE) vs. 70 +/- 8 ml X 100 g-1 X min-1], muscle lactate contraction (44 +/- 10 vs. 26 +/- 4 mmol/kg dry wt), and lactate release (122 +/- 12 vs. 57 +/- 14 mumol X 100 g-1 X min-1). O2 uptake and the rate of fatigue were not different among treatments during contractions. Muscle [H+] increased (work [H+] minus rest [H+]) to a significantly greater extent during low arterial O2 tensions compared with high (P less than 0.05). We conclude that alterations in arterial O2 tension during fatiguing contractions induce changes in blood and muscle acid-base status and in muscle metabolism that are independent of O2 uptake.

Acid-Base Equilibrium↗
PubMed1986

Optimal pedalling rate in prolonged bouts of cycle ergometry.

This study was designed to investigate the variables which contribute to the determination of optimal pedalling rate in cycling. Five trained bicycle racers were used as subjects for the study. The experiment consisted of five 20- to 30-min tests at about 85% of each subject's pre-determined VO2max. Pedal rates of 40, 60, 80, 100, and 120 rpm were used. In the experiment, efficiency, heart rate, and perceived exertion measures were obtained at 10 and 20 min of exercise. Blood lactate concentration and plasma levels of epinephrine and norepinephrine were measured at rest, during the exercise sampling periods, and at 5 min of recovery following the exercise bout. When compared across pedal rates, gross efficiency, heart rate, and perceived exertion all were minimal at 60 or 80 rpm for each sampling period. Blood lactate showed the same relationship to pedal rate as the preceding variables at 10 min of exercise but not late in the test. The catecholamine values appeared to follow a similar trend but not significantly. The experiment showed that for this group of cyclists an optimal pedal rate existed for a prolonged period of exercise and was evident in measures of both efficiency and perceived exertion. The experiment indicates that, for researchers and for cyclists who use high power outputs, the choice of pedal rate is an important one.

Adult↗
PubMed1985

Linear increase in optimal pedal rate with increased power output in cycle ergometry.

This experiment was designed to estimate the optimum pedal rates at various power outputs on the cycle ergometer. Five trained bicycle racers performed five progressive maximal tests on the ergometer. Each rode at pedal rates of 40, 60, 80, 100, and 120 rev X min-1. Oxygen uptake and heart rate were determined from each test and plotted against pedal rate for power outputs of 100, 150, 200, 250, and 300 W. Both VO2 and heart rate differed significantly among pedal rates at equivalent power outputs, the variation following a parabolic curve. The low point in the curve was taken as the optimal pedal rate; i.e., the pedal rate which elicited the lowest heart rate or VO2 for a given power output. When the optimum was plotted against power output the variation was linear. These results indicate that an optimum pedal rate exists in this group of cyclists. This optimum pedal rate increases with power output, and when our study is compared to studies in which elite racers, or non-racers were used, the optimum seems to increase with the skill of the rider.

Adult↗
PubMed1985

Effect of respiratory alkalosis on skeletal muscle metabolism in the dog.

These experiments were conducted to determine whether changes in skeletal muscle metabolism contribute to the previously reported increase in whole-body O2 uptake (VO2) during respiratory alkalosis. The hind-limb and gastrocnemius-plantaris preparations in anesthetized and paralyzed dogs were used. VO2 of the hindlimb and gastrocnemius muscle was calculated from measurements of venous blood flow and arterial and venous O2 concentrations (Van Slyke analysis). Whole-body VO2 was measured by the open-circuit method. Minute ventilation (hence blood gases and pH) was controlled by a mechanical respirator. Whole-body, hind-limb, and gastrocnemius muscle VO2 increased 14, 19, and 20%, respectively, during alkalosis (P less than 0.05). In all experiments, arterial lactate concentration increased significantly (P less than 0.05) during alkalosis. A positive venoarterial lactate difference across muscle during alkalosis indicated that skeletal muscle is a source of the elevated blood lactate. We concluded that VO2 of resting skeletal muscle is increased during states of respiratory alkalosis and that this increase can account for much of the increase in whole-body VO2.

Alkalosis, Respiratory↗
PubMed1984

Effect of varied lactate levels on bicycle ergometer performance.

Six subjects exercised on the bicycle ergometer on three separate occasions. Each of the three tests that each subject performed consisted of a 5-min work period [95% maximal O2 uptake (VO2max)], followed by a 4-min rest period, and then a performance task to exhaustion (90% VO2max). Each test varied only in the inspired O2 fraction (FIO2) (16, 21, or 60% O2 in N2) that was breathed during the initial 5-min work period. The remainder of each test was carried out with 21% O2. Total power output was the same for each subject during the initial 5-min work bout. However, the varied FIO2 breathed during this initial work period resulted in significantly different mean blood lactate (and H+) concentrations at the start of the performance task (P less than 0.05). Mean performance time was significantly greater (P = 0.04) after the hyperoxic treatment (14.8 min) when compared with the hypoxic (9.1 min). Mean blood lactate and H+ levels at exhaustion were not significantly different. These data demonstrate that when various blood (or muscle) lactate and H+ levels were induced on different occasions by leg muscles, the subsequent performance of those muscles was significantly affected.

Adult↗
PubMed1983

Effect of hyperoxia on metabolic and catecholamine responses to prolonged exercise.

The use of inspired gas mixtures with an oxygen fraction in excess of 0.3 has been associated with a decrease in the gas exchange ratio (R) during prolonged work in humans. It had been hypothesized that the lower R was due to a lower plasma catecholamine concentration caused by the hyperoxia (Med. Sci. Sports 10: 167-170, 1978). We tested this hypothesis by measuring changes in plasma epinephrine and norepinephrine when the subjects were switched from breathing air to 60% O2 (and vice versa) during 40 min of cycle ergometer exercise at 67% maximal oxygen uptake (VO2max). The subject breathed one gas mixture for the first 30 min and was switched to the other in the last 10 min. The order was reversed in the second test. The switch in gas mixtures from air to 60% O2 resulted in a significant reduction in R, heart rate, minute ventilation, blood lactate concentration, and plasma epinephrine concentration (P less than 0.05). The plasma norepinephrine concentration (0.1 greater than P greater than 0.05) and the plasma free fatty acid concentration were not significantly changed. Although the direction of the epinephrine change was consistent with the change in R, the epinephrine change was quantitatively small (20 pg/ml) and of questionable physiological significance. This suggests a direct effect of PO2 on cellular metabolism as one cause of the change in R when the subjects were switched from air to 60% O2.

Epinephrine↗