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Biomedical subjects

D Weiler-Ravell

Publications and source records attributed to D Weiler-Ravell.

35 records · Page 2Linked to original sources
PubMed1984

Aerobic parameters of exercise as a function of body size during growth in children.

To examine the relationship between body weight in children and aerobic parameters of exercise, we determined the anaerobic threshold (AT), maximum O2 uptake (VO2max), work efficiency, and response time for O2 uptake (RT-VO2) in 109 healthy children (51 girls and 58 boys, range 6-17 yr old) using a cross-sectional study design. Gas exchange during exercise was measured breath by breath. The protocol consisted of cycle ergometry and a linearly increasing work rate (ramp) to the limit of the subject's tolerance. Both AT and VO2max increased systematically with body weight, whereas work efficiency and RT-VO2 were virtually independent of body size. The ratio of AT to VO2max decreased slightly with age, and its mean value was 60%. AT scaled to body weight to the power of 0.92, not significantly different from the power of 1.01 for VO2max. Thus both the AT and the VO2max increase in a highly ordered manner with increasing size, and as judged by AT/VO2max, the onset of anaerobic metabolism during exercise occurred at a relatively constant proportion of the overall limit of the gas transport system. We conclude that in children cardiorespiratory responses to exercise are regulated at optimized values despite overall change in body size during growth.

Adolescent↗
PubMed1984

Gas exchange response to exercise in children.

We measured the gas exchange response to exercise in 109 normal children (51 girls and 58 boys, ranging in age from 6 to 17 yr old) using noninvasive breath-by-breath techniques. The protocol consisted of cycle ergometry in which the work rate increased in a linear manner (ramp forcing function) until the limit of the subject's tolerance was reached. We measured the maximal oxygen uptake (VO2max) and the VO2 at the anaerobic threshold (AT). We found that both of these parameters were highly correlated with increasing height, and that for both the AT and VO2max, the values for boys were significantly higher than girls. We compared our results of VO2max to those obtained by Astrand over 30 years ago using different techniques. When boys and girls were considered together, there were no significant differences between our study and Astrand's; however, girls in our study had significantly lower values for VO2max than did girls in Astrand's study. These data provide normal values for both VO2max and AT and can be used to evaluate the exercise impairment resulting from disease in children.

Adolescent↗
PubMed1984

Growth-related changes in oxygen uptake and heart rate during progressive exercise in children.

Although body size and muscle mass increase considerably during growth in children, certain aerobic responses to exercise appear to be regulated so that the delivery of oxygen to muscle is maintained at optimized levels. We proposed that the relationship between oxygen uptake, (VO2) and heart rate (HR) was one of the regulated responses. We further hypothesized that the increase in VO2 per increase in HR during progressive exercise would differ in subjects of different size, but when normalized to body weight would be constant since changes in muscle mass are highly correlated to changes in body mass. To test this, we performed a cross-sectional study of 107 normal children, 50 girls and 57 boys ranging in age from 6 to 17 years. The protocol consisted of a continuously increasing work rate on a cycle ergometer, to the limit of the child's tolerance (ramp forcing function). Gas exchange was measured breath-by-breath for the determination of VO2, and heart rate was measured beat-by-beat. We used linear regression techniques to determine M, the slope, and B, the y intercept of the equation: VO2 = M X HR - B. In both boys and girls, M increased significantly with body weight, but when normalized for body weight (M/kg), there was no systematic change with increasing weight or age, the mean value being 0.33 +/- 0.10 ml/min/kg (SD). The mean value for the boys was 0.37 +/- 0.10 which was significantly greater than that of the girls (0.29 +/- 0.08, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1983

Effect of a twelve-hour hiatus in propranolol therapy on exercise tolerance in patients with angina pectoris.

To determine whether propranolol can be administered twice daily without any loss of antianginal effect, we studied nine men receiving long-term propranolol therapy for stable angina pectoris. Each patient performed bicycle exercise to the point of angina on two consecutive mornings. By means of double-blind placebo-propranolol administration before the test, the study created a situation whereby on one day the exercise took place 12 hours after the last dose of propranolol, and on the other day 1 1/2 hours after a dose. Despite markedly lower blood levels of propranolol on the day that exercise was performed 12 hours after the last dose, exercise time to angina was nearly identical on the 2 days. We conclude that long-term therapy with propranolol for angina pectoris can be administered on a twice daily basis with no loss of effectiveness.

Adult↗
PubMed1983

Control of breathing at the start of exercise as influenced by posture.

It has been suggested that the initial phase of the ventilatory response to exercise is governed by a mechanism which responds to the increase in pulmonary blood flow (Q)--cardiodynamic hyperpnea. Because the initial change in stroke volume and Q is less in the supine (S) than in the upright (U) position at the start of exercise, we hypothesized that the increase in ventilation would also be less in the first 20 s (phase I) of S exercise. Ten normal subjects performed cycle ergometry in the U and S positions. Inspired ventilation (VI), O2 uptake (VO2), CO2 output (VCO2), corrected for changes in lung gas stores, and end-tidal O2 and CO2 tensions were measured breath by breath. Heart rate (HR) was determined beat by beat. The phase I ventilatory response was markedly different in the two positions. In the U position, VI increased abruptly by 81 +/- 8% (mean +/- SE) above base line. In the S position, the phase I response was significantly attenuated (P less than 0.001), the increase in VI being 50 +/- 6%. Similarly, the phase I VO2 and VO2/HR responses reflecting the initial increase in Q and stroke volume, were attenuated (P less than 0.001) in the S posture, compared with that for U; VO2 increased 49 +/- 5.3 and 113 +/- 14.7% in S and U, respectively, and VO2/HR increased 16 +/- 3.0 and 76 +/- 7.1% in the S and U, respectively. The increase in VI correlated well with the increase in VO2, (r = 0.80, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

Comparison of the antianginal effectiveness of nifedipine, verapamil, and isosorbide dinitrate in patients receiving propranolol: a double-blind study.

Ten men with stable angina not fully relieved by optimal doses of propranolol were given on each of four mornings a single dose of 10 mg nifedipine, 120 mg verapamil, isosorbide dinitrate (5 to 30 mg, previously titrated to lower systolic blood pressure by 15 to 20 mm Hg), or placebo, in double-blind fashion. Bicycle exercise to angina was performed hourly for 8 hr thereafter. All three vasodilators increased exercise time by at least 50% by the first hour (p less than .001), with a gradually diminishing effect persisting for 6 to 8 hr (p less than .01). Although for the group there were no differences in magnitude and duration of effect among the three drugs, in five of the individual patients there were important differences in response favoring one or another vasodilator. We conclude that nifedipine, verapamil, and isosorbide dinitrate are equally effective and reasonably long-acting antianginal supplements to propranolol, although some patients may benefit more from one than another of the three.

Adult↗
PubMed1983

The additive antianginal action of oral isosorbide dinitrate in patients receiving propranolol. Magnitude and duration of effect.

Ten men with stable angina not completely relieved by full doses of propranolol (mean, 218 mg daily) were given double-blind, on alternate mornings, a placebo or an oral dose (5 to 30 mg) of isosorbide dinitrate (ISDN) previously titrated to lower sitting systolic blood pressure by 20 mm Hg. Patients had been trained in a protocol which precipitated angina after three to six minutes of bicycle exercise. On test days, with propranolol continued, bicycle exercise was performed until the appearance of angina before ISDN or placebo administration, and hourly thereafter for eight hours. Mean exercise duration was greater one hour after ISDN than after placebo by 182 sec (423 +/- 39 vs 241 +/- 13, p less than 0.001), and a difference of 63 sec was still present at six hours (p less than 0.002). At one hour, ISDN lowered resting systolic blood pressure by 26 mm Hg (from 114 +/- 5 mm Hg to 88 +/- 4 mm Hg; p less than .001) without appreciably changing heart rate. We conclude that ISDN is a very effective and reasonably long-acting antianginal supplement to propranolol.

Administration, Oral↗
PubMed1982

Additive antianginal effect of verapamil in patients receiving propranolol.

Ten men with stable angina pectoris not fully relieved by optimal doses of propranolol (mean 218 mg daily) were given a single oral dose of 120 mg verapamil or a placebo on alternate mornings; the order of treatment was double blind. Patients had trained in a protocol that precipitated angina after three to six minutes of exercise on a bicycle ergometer. On test days, and with continued propranolol treatment, bicycle exercise was performed just before the administration of verapamil or placebo and hourly thereafter for eight hours. Mean exercise tolerance was 118 seconds greater one hour after verapamil than one hour after placebo (p <0.001), and a significant though somewhat diminished difference of 66 seconds was still present at six hours (p <0.01). Verapamil lowered resting systolic blood pressure by 12 mm Hg (p <0.01) without changing heart rate. None of the 10 patients showed adverse effects from the verapamil-propranolol combination.The results of this study suggest that verapamil is a highly effective antianginal supplement to propranolol.

Angina Pectoris↗
PubMed1982

The additive antianginal action of oral nifedipine in patients receiving propranolol: magnitude and duration of effect.

Ten men with stable angina not completely relieved by full doses of propranolol (mean 218 mg/day) were administered an oral dose of 10 mg of nifedipine or placebo on alternate mornings in a double-blind fashion. Patients had been trained in a protocol that precipitated angina after 3-6 minutes of bicycle exercise. On test days, with propranolol continued, bicycle exercise to angina or fatigue was performed before nifedipine or placebo administration, and hourly thereafter for 8 hours. Mean exercise duration was greater 1 hour after nifedipine than after placebo by 123 seconds (372 +/- 21 vs 249 +/- 16 seconds, p less than 0.001). By the fifth hour, the increase in exercise time was reduced to 93 seconds (p less than 0.001), and a significant, though further diminished, difference of 57 seconds was still present at 8 hours (p less than 0.01). Nifedipine lowered resting systolic blood pressure by 20 mm Hg (p less than 0.001) without appreciably changing heart rate. We conclude that nifedipine is a very effective and reasonably long-acting antianginal supplement to propranolol.

Administration, Oral↗
PubMed1981

Do exercise- and antigen-induced asthma utilize the same pathways? Antigen provocation in patients rendered refractory to exercise-induced asthma.

Twelve asthmatics (ages 8 to 33 yr) with proven exercise-induced asthma (EIA) and allergen-induced asthma (AIA) were investigated in an attempt to elucidate the pathways through which each type of attack develops. All patients were rendered refractory to EIA by repeated exercise at short intervals and were then immediately challenged by inhalation with an allergen known to evoke AIA. After an average of three runs all subjects were rendered refractory to EIA (post-exercise fall in FEV1 of 7 +/- 8% SEM compared with the control postexercise fall of 32 +/- 14%). In this refractory state six patients failed to respond to antigen challenge (6 +/- 4% SEM fall in FEV1 compared with the 30 +/- 3% fall in control study, p less than 0.001), suggesting a common pathway for EIA and AIA, such as the exhaustion of stored chemical mediators. Six other patients developed attacks of AIA while refractory to EIA, which were at least as severe as those in their control study (34 +/- 7% SEM fall in FEV1 compared with 29 +/- 3%). The fact that AIA could develop while EIA was blocked in this group requires an alternate pathway or mechanism for their AIA. The only significant difference between the AIA "blocked" and AIA "nonblocked" groups was a lower baseline level of lung function in all tests in the nonblocked group.

Adolescent↗
PubMed1981

Quinine alone versus quinine plus a pyrimethamine-sulfadoxine combination in the treatment of Plasmodium faliciparum cerebral malaria.

Fifty-two patients with severe chloroquine resistant Plasmodium falciparum malaria were treated in a randomized double blind study with either quinine and a single dose of pyrimethamine-sulfadoxine (Fansidar) or quinine alone. Although no statistically significant differences were observed, the 25 patients who received both drugs responded faster and had a more favorable outcome (no deaths) when compared to the 27 who received quinine alone (2 deaths).

Clinical Trials as Topic↗
PubMed1979

Hematin and propranolol in acute intermittent porphyria. Full recovery from quadriplegic coma and respiratory failure.

The authors present a case of acute intermittent porphyria (AIP) in an almost fatal relapse with quadriplegia, bulbar paralysis and coma. Intravenous hematin produced an immediate arousal from coma and allowed a gradual resumption of bulbar and autonomic functions. Persistent tachycardia and hypertension necessitated huge doses of intravenous propranolol. Both hematin and propranolol administrations were followed by a remarkable decrease in urinary amino-levulinic acid and porphobilinogen excretion. Nevertheless, after the acute stage, the patient was left with a severe generalized muscle wasting. After 7 months of intensive physical therapy, complete recovery of all neuromuscular functions was achieved. The modern aspects of the management of AIP are presented; the efficacy and the limits of hematin and propranolol therapy are discussed.

Acute Disease↗
PubMedDate not supplied

Blast injury of the chest. A review of the problem and its treatment.

Primary blast injury of the chest is a potentially lethal entity. Immersion blast is even more damaging than that incurred out of water. Illustrative cases of a group of patients injured by an underwater explosion are presented. The pathogenesis, clinical manifestations and diagnosis of the entity are described. Complications include arterial occlusion by air emboli, affecting the central nervous system and heart, and respiratory insufficiency and failure. Conventional management of respiratory failure with intermittent positive pressure breathing may further aggravate the air embolism. An attempt to circumvent this conflict with the aid of the membrane oxygenator and hyperbaric facilities is discussed. It is suggested that expeditious compression with oxygen in a one-man chamber might be the most favorable emergency measure, to be followed later by more extensive and definitive treatment in a major hospital equipped for such contingencies.

Blast Injuries↗