Search

A monochromatic beam obtained from laboratory based instrumentation has been used for the first time to carry out a microtomographic x-ray scan of a small segment of osteoporotic bone. The resulting tomograph provides an accurate map of the x-ray linear attenuation coefficient at the characteristic energy for Cu K alpha x-rays. The bone segment was imaged in a variety of ways which are common to microtomography in order to compare the efficacy of different experimental configurations. A Si crystal monochromator was placed before the x-ray detector in order to reject radiation scattered by the sample. In addition, polychromatic scans were compared with monochromatic scans. The effects of multiple scatter can be seen upon comparison of scans with and without the second monochromator. The results indicate that beam-hardening and x-ray scattering can significantly alter an image, thereby distorting the interpretation of what is physically present in the specimen. An accurate, monochromatic tomographic scanning facility is being developed in an attempt to map meaningful physical constants for various materials.

This study examined the relationships between thigh muscle volume (TMV) and aerobic and anaerobic performance in children. A total of 32 children, 16 boys and 16 girls, aged 9.9 (0.3) years completed a treadmill running test to exhaustion for the determination of peak oxygen uptake (peak VO2) and a Wingate Anaerobic Test (WAnT) for the determination of peak power (PP) and mean power (MP). The volume of the right thigh muscle was determined using magnetic resonance imaging. TMV was not significantly different in boys and girls [2.39 (0.29) l vs 2.18 (0.38) l, P > 0.05]. Peak VO2 and MP were significantly higher in boys than girls (P < 0.01) whether expressed in absolute, mass-related or allometrically scaled terms. Absolute PP was not significantly different in boys and girls but mass-related and allometrically scaled values were higher in boys (P < 0.01). TMV was correlated with absolute peak VO2, PP and MP in both sexes (r = 0.52-0.89, P < 0.01). In boys, mass-related PP was correlated with TMV (r = 0.53, P < 0.01), and in girls mass-related peak VO2 was correlated with TMV (r = -0.61, P < 0.01). However, in neither sex were allometrically scaled peak VO2, PP or MP correlated with TMV (P > 0.05). There were no significant differences between boys and girls in terms of peak VO2, PP or MP when expressed in a ratio to TMV or allometrically scaled TMV. In conclusion, this study has demonstrated that, when body size is appropriately accounted for using allometric scaling, TMV is unrelated to indices of aerobic and anaerobic power in 10-year-old children. Furthermore, there appear to be no qualitative differences in the muscle function of boys and girls in respect of aerobic and anaerobic function.

This study was designed to enhance understanding of the assessment and interpretation of the aerobic fitness of prepubertal children. Written informed consent to participate was obtained from 70% of the children in year six of the 15 state schools in the city of Exeter. Twenty-five per cent of the eligible children in each school were randomly selected from those who volunteered. The data reported here are those obtained from the 111 boys (11.1 SD 0.4 years) and 53 girls (10.9 SD 0.3 years) classified as Tanner stage 1 in both pubic hair rating and either genitalia rating (boys) or breast rating (girls). Peak oxygen uptake (peak VO2) was determined using a discontinuous, incremental protocol on a treadmill. Only a minority of children demonstrated a levelling-off or plateau in VO2 despite an increase in exercise intensity. There was no evidence to suggest that the children who demonstrated a VO2 plateau had significantly (p < 0.05) higher peak VO2, peak heart rate, peak respiratory exchange ratio or peak blood lactate than those children who did not demonstrate a plateau in VO2. These findings indicate that a VO2 plateau should not be used as a requirement for defining a maximal exercise test with prepubertal children. Boys had a significantly (p < 0.01) higher peak VO2 than girls, whether expressed in 1.min-1 (1.78 vs 1.46) or in relation to body mass (51 vs 45 ml.kg-1.min-1). The results compare favourably with those of similarly aged children from other countries, but why prepubescent boys have significantly higher (13.3%) mass-related peak VO2 than prepubescent girls is not readily apparent. Although conventional, the expression of peak VO2 as per body mass ratio may not adequately partition out body-size differences. The influence of body mass was therefore removed using a linear adjustment scaling model and a log-linear model, but the boys' peak VO2 remained significantly (p < 0.01) higher than the girls' peak VO2 with the difference now being 16.0% and 16.2%, respectively.

We carried out a prospective survey of the outcome of patients with 'suspected myocardial infarction', in order to determine where they should be nursed. The delay between onset, admission, transfer to the CCU, the sequelae and side-effects of thrombolytic therapy were noted and were documented prospectively. Of 217 admissions to CCU with a history of chest pain and suspected acute myocardial infarction during a four-month period (mean age was 62.8 years range 31 to 86 years) 202 fulfilled the criteria for suspected myocardial infarction. Streptokinase was given in 129 and alteplase in one patient. The delay between onset of pain and admission was < 4 h in 73, 4 to 12 h in 30 and > 12 h in 23. Elderly patients were just as likely as younger ones to receive thrombolytic therapy (Chi 2 = 3.6; P = 0.6). An eventual diagnosis of acute myocardial infarction was made in 133 of whom 100 received streptokinase. Dysrhythmia or shock was encountered in one-third of those given streptokinase and a quarter of the remainder. Reactions to streptokinase were recorded in 32 mainly hypotension or bradycardia alone or in combination. Forty-five per cent experienced either cardiac complications or drug reactions or both. During one month there were 57 admissions, 50 of whom arrived by ambulance. The mean delay between call out and arrival in the A&E department was 55 min. We concluded patients who are given thrombolytic therapy need close supervision and they should be nursed in a CCU or its equivalent.

Unlabelled: This paper reports the findings of two investigations into methodological problems associated with the interpretation of blood lactate (BLa) in the sports sciences. In Experiment 1, brachial artery (A), antecubital venous (V) and fingertip capillary (C) blood samples were drawn simultaneously from nine subjects (mean age 21.1 +/- 1.3 years) during an incremental treadmill protocol and immediately assayed for BLa concentration. Experiment 2 investigated the extent of lactate concentration differences in whole blood (WB), lysed blood (LB) and plasma (P) measured using a YSI 23 AM analyser. In Experiment 1, a comparison of the mean BLa concentrations obtained from the three sites revealed no significant differences (P greater than 0.05). Correlations between BLa samples from different sites were very high, with r values ranging from 0.858 to 0.983. In Experiment 2, the mean lactate concentrations were: WB, 4.7 +/- 2.7 mM; LB, 5.0 +/- 3.0 mM; P, 7.0 +/- 3.8 mM. Plasma (P) values were significantly higher than WB and LB. Values from all sites were highly correlated with coefficients ranging from 0.963 to 0.987., In Conclusion: (1) Significant arterial and venous BLa concentration differences do not exist during incremental treadmill exercise. (2) As capillary BLa concentrations reflect arterial values, their use in laboratory and field settings is recommended. (3) Lactate concentration differences in whole blood, lysed blood and plasma will influence the assessment of performance at fixed lactate reference values. (4) If the inter-laboratory test procedures are to be standardized and results compared, precise reporting of lactate sampling and assay techniques is critical.

The aim of this study was to assess the use of the 4 mM blood lactate level measured during incremental treadmill exercise as an indicator of exercise performance in 11-13 year old children. Fifty girls and 53 boys (means age 12.2 +/- 0.6 years) gave informed consent to participate in the study. The children completed a discontinuous, incremental running test on a motorized treadmill. A 1 min pause separated the 3 min exercise stages during which time duplicate capillary blood samples were taken for immediate assay of whole blood lactate concentration. Cardiorespiratory variables were measured continuously during exercise using a computerized on-line system. Mean values for peak oxygen uptake were 48 +/- 7 ml kg-1 min-1 and 42 +/- 7 ml kg-1 min-1 in boys and girls respectively. The exercise intensity corresponding to a blood lactate concentration of 4 mM was interpolated from plots of % peak oxygen uptake vs blood lactate and was reached at 91 +/- 7% peak oxygen uptake in both boys and girls. The results indicate that children can exercise at intensities close to their peak oxygen uptake without accumulating high levels of blood lactate and the use of the 4 mM blood lactate level to assess and monitor exercise performance in children of this age may therefore be inappropriate.

We have studied the cardiorespiratory effects of the rapid infusion (100 ml/min) of 2 liters of saline in four normal seated subjects. Cardiac output and pulmonary arterial pressure increased, while vital capacity (VC) and total lung capacity (TLC) decreased. There was an increase in closing volume (CV) without any detectable change in lung compliance or flow-volume characteristics. There was an increase in Pao2 during infusion period which can be related to better matching of ventilation to perfusion and to improved hemoglobin transport. In the recovery stage as cardiac output, pulmonary arterial pressure, TLC, and VC all returned toward control values CV remained high. In two subjects CV occurred within the normal tidal range of ventilation and in these two subjects Pao2 fell significantly below values obtained in the control period. The results suggest that rapid saline infusion in man can cause interstitial edema and lead to premature airway closure and hypoxemia.

The natural history of new and worsening angina pectoris was studied in 251 men aged under 70 years. Most were ambulant and all were referred by selected general practitioners to a special hospital clinic over two and a half years. Heart attacks developed in 39 patients, nine of whom died. Seventy-two per cent of the attacks occurred within six weeks of the onset or worsening of angina. Of the 212 patients who did not suffer myocardial infarction and who were clinically reviewed six months after their first attendance 66 had been pain free for the previous three months and 14 had experienced only infrequent attacks of angina. Of the 128 men aged under 65 years who were previously in employment 81% had returned to full-time work six months after their first attendance. A discriminant function analysis using many variables was made to develop a predictive index that would allow patients with new or worsening angina who were likely to develop serious cardiac complications to be identified. This did not prove possible, and the only predictive factor of significance was an increased cardiothoracic ratio. The syndrome of new and worsening angina has a low risk of early death, and many patients are symptom free six months later. In general, emergency coronary arteriography and surgery is not indicated.

Direct measurements of the factors determining blood oxygen transport in 10 patients with chronic hypoxic respiratory failure led to the conclusion that wide differences in the position of their oxygen binding curves, due to spontaneous differences in red-cell 2, 3-diphosphoglycerate, had little effect on oxygen delivery to the tissues, as assessed by the mixed venous oxygen tension when they were breathing air. This result arises from the shape of the oxygen binding curve. A drug which could shift the curve to the right would help tissue oxygenation in cardiogenic and other forms of shock, when a low cardiac output can not be improved though arterial blood can be well oxygenated.

1. We measured the minute ventilation and arterial blood catecholamine concentrations in four normal men standing and at two levels of moderate treadmill exercise breathing 14% oxygen or air. 2. Minute ventilation was significantly higher during hypoxic exercise than during normoxic exercise at an oxygen uptake of 1500 ml/min. 3. Arterial plasma noradrenaline during hypoxic exercise at an oxygen uptake of 1500 ml/min was significantly greater than at rest. 4. Arterial plasma noradrenaline during normoxic exercise at an oxygen uptake of 1500 ml/min was not elevated above the resting concentration. 5. The results are compatible with the suggestion that increased concentrations of arterial plasma noradrenaline contribute to the hypoxic potentiation of the respiratory response to moderate exercise.

Ten patients with cor pulmonale complicating severe chronic bronchitis and emphysema have been treated with 2 litres/min of oxygen for prolonged periods in the day, at home, over 12 to 62 months. Two patients died after 12 and 36 months of treatment. Pulmonary arterial pressure was reduced in seven patients, and red cell mass in eight, when the oxygen was given for over 15 hours in the day. Hospital inpatient treatment was greatly reduced following the start of long-term oxygen treatment in all patients. This treatment is expensive, and a controlled trial is necessary to establish its definitive place and cost-effectiveness, but the results of such a current Medical Research Council trial will not be available for a further two years.

Eighteen patients with severe chronic obstructive lung disease (arterial PCO2 greater than 45 mmHg arterial PCO2 less than 55 mmHg) were studied during a stable period of their disease. Samples of arterial blood and blood from the main pulmonary artery, internal jugular vein, hepatic vein, renal vein and femoral vein were taken by manipulating a Cournand catheter to each of these sites in rapid succession. An estimate of the regional distribution of blood flow was derived from the arterio-venous oxygen content difference of each organ. Expired air was collected into a spirometer. There was a redistribution of blood flow in these patients with chronic lung disease in accord with the observations made by others in the past. Carbon dioxide concentration in the venous blood depends on 1. the blood flow to an organ, and 2. the carbon dioxide production by the organ. The total body CO2 production was within normal limits and there is no reason to suspect any alteration in carbon dioxide production by individual organs in these resting patients. Thus the venous CO2 levels are intimately linked with organ blood flow but even a substantial increase in organ blood flow cannot always compensate for the disorder in the lung. The exact role of CO2 in regulating the peripheral circulation cannot be assessed from this study but they do emphasize the importance of regional blood flow in regulating the concentration of CO2 in the venous blood and presumably in the tissues making up the organ.

Several nuclear and atomic techniques are available to a scanning proton microprobe for examining the elemental distributions and microstructure within a specimen. The instrument and its techniques are discussed together with some examples of non-destructive elemental microanalysis. The handling and display of quantitative maps and their relationship to regional spectra are shown with an emphasis in this paper on biological applications.

The Valsalva manoeuvre was used to examine circulatory reflexes in 22 patients with acute myocardial infarction. Four patients had the 'square wave' response of cardiac failure and two responded normally to the manoeuvre. In the remaining 18 patients there was a 20 per cent or more fall in pulse pressure during the manoeuvre, but no ensuing rise in diastolic pressure, implying impairment of vasoconstriction. This impairment cannot be explained by acidosis, hypocapnia, or arterial hypoxaemia but may be explained by reflex inhibition of vasoconstriction. This abnormal response has important implications when transporting patients; furthermore, it could explain the rapid deterioration sometimes seen in patients with arrhythmias.

The analgesic effect of self-administered nitrous oxide 50%/oxygen 50% ('Entonox" analgesic apparatus) was compared with air given by the same method in a double-blind trial in 81 patients with myocardial infarction. Self-administered nitrous oxide/oxygen, which was associated with a low frequency of side-effects, proved significantly more effective than air in the early relief of severe cardiac pain, but not in the relief of moderate or slight pain or when administration was continued after ten minutes.

A 49 year old man presented with near-fatal, fulminant, haemorrhagic cardiac tamponade. He responded well to emergency pericardiocentesis and subsequent investigation revealed the cause to be an unknown squamous carcinoma of the bronchus with pericardial involvement. He died 13 weeks later. Such a dramatic presentation of this type of tumour in a male patient has not been previously described.

When breathing air, the average arterial oxygen tension in eight patients with acute pulmonary oedema was significantly higher than in eight other patients suffering from an acute exacerbation of chronic bronchitis, but the mixed venous oxygen tension was very similar in both groups. This largely arose from the smaller arteriovenous difference of oxygen content in the bronchitic cases, presumably due to their higher cardiac output, associated with raised arterial CO(2) tensions. Oxygen therapy (60-90% for pulmonary oedema, 30% for the bronchitics) raised the mixed venous oxygen tensions to a similar level in both groups. We suggest that the major need for oxygen therapy lies in patients who maintain their oxygen consumption but show a reduction in mixed venous tension when breathing air. Although partial correction of arterial hypoxaemia is adequate in chronic bronchitis-in which the cardiac output is maintained-high concentrations of oxygen are necessary in pulmonary oedema, in which the cardiac output is low.

Acid-base balance has been studied in 21 patients with acute upper gastrointestinal bleeding. A low plasma bicarbonate concentration was found in nine patients, accompanied in each case by a base deficit of more than 3 mEq/litre, indicating a metabolic acidosis. Three patients had a low blood pH. Hyperlactataemia appeared to be a major cause of the acidosis. This was not accompanied by a raised blood pyruvate concentration. The hyperlactataemia could not be accounted for on the basis of hyperventilation, intravenous infusion of dextrose, or arterial hypoxaemia. Before blood transfusion it was most pronounced in patients who were clinically shocked, suggesting that it may have resulted from poor tissue perfusion and anaerobic glycolysis. Blood transfusion resulted in a rise in lactate concentration in seven patients who were not clinically shocked, and failed to reverse a severe uncompensated acidosis in a patient who was clinically shocked. These effects of blood transfusion are probably due to the fact that red blood cells in stored bank blood, with added acid-citrate-dextrose solution, metabolize the dextrose anaerobically to lactic acid. Monitoring of acid-base balance is recommended in patients with acute gastrointestinal bleeding who are clinically shocked. A metabolic acidosis can then be corrected with intravenous sodium bicarbonate.

Mixed venous oxygen saturations derived from measurement of mixed venous oxygen tension were compared with dye dilution cardiac output determinations in 26 patients with acute myocardial infarction. Mixed venous oxygen saturation was greatly reduced in patients with shock or failure complicating myocardial infarction. The level of oxygen saturation correlated with cardiac output determinations. The measurement of mixed venous oxygen saturation, which is relatively simple and does not require elaborate equipment, should be an important aid to the rational treatment of patients with low output states complicating acute myocardial infarction.