bluuebunny/crossref_metadata_2025 huggingface dataset:
Lung volumes measured by helium dilution and by body plethysmography with mouth and oesophageal pressures: A comparative study in patients with lung disease
Authors: Dahlqvist Monica , Hedenstierna Goran
Published: April 2008

Summary. A comparison was made between the helium dilution technique and body plethysmography‐using both mouth pressure and oesophageal pressure against box pressure‐for measuring functional residual capacity (FRC). In patients with restrictive lung disease (n= 9) no major differences in FRC were noted between the techniques. In patients with obstructive lung disease (n= 17), helium dilution underestimated FRC by a mean of 0–9 1 and conventional body plethysmography (mouth‐box pressure) overestimated it by 0.4 1 in comparison with FRC obtained by oesophageal pressure against box pressure. The difference between the techniques increased with increasing lung volumes. It is concluded that conventional body plethysmography measures FRC more accurately than the helium dilution technique in patients with obstructive lung disease.
NONINVASIVE PULMONARY BLOOD FLOW FOR OPTIMAL PEEP
Authors: Gedeon A.
Published: April 2008

Recent data in the literature suggest that effective pulmonary blood flow (Q) measured invasively as cardiac output minus shunt flow, assumes its largest value at a PEEP level that is optimal in the sense that it also provides close to maximal oxygen delivery. Qp obtained noninvasively from simultaneous measurements of mixed expired and end‐tidal CO2‐concentrations is therefore proposed as a simple clinical indicator of the effects of PEEP on the cardio‐pulmonary system. It is shown that modern respiratory equipment can be easily adapted to implement such a noninvasive evaluation of PEEP therapy. If the method is proven useful an automatic search for optimal PEEP becomes a future possibility.
Autonomic cardiovascular responses in old age
Authors: Kaijser Lennart , Sachs Charlotte
Published: April 2008

Summary. The effect of age on autonomically mediated cardiovascular responses to certain manoeuvres was studied in 15, healthy, old men and women (60–80 years). The results were compared with groups of healthy young (about 25 years) and middle‐aged (about 45 years) subjects. There was no significant reduction in cardiovascular responses between the young and middle‐aged groups. Respiratory sinus arrhythmia, and heart rate, blood‐pressure and contralateral forearm blood flow increases to isometric hand grip, as well as the heart rate decrease during a dive reflex test, were significantly attenuated in the old age group. The Valsalva ratio, and the heart rate and blood‐pressure changes during an 8 min orthostatic test did not differ between the old and the two younger age groups.

There seems to be only a moderate attenuation of autonomic cardiovascular responses to about 60 years, after which there is a more rapid decline. The difference in reduction between different responses, even those mediated by the same type of autonomic nerve, suggests that the decreased responses are not due to an isolated impaired function of the peripheral autonomic nerve. The impairment may be due to the receptor organ or a combination of defects in function of several parts of the autonomic nervous system in old age.
Arterial blood‐pressure change and endogenous circulating substance P in man
Authors: Henriksen Jens H. , Kastrup Jens , Muckadell Ove B. Schaffalitzky De
Published: April 2008

Summary. Substance P (SP) is a powerful vasodilator and this peptide is today considered to be a chemical messenger. The potential effects on circulating SP of acute changes in arterial blood‐pressure were investigated in nine subjects. An increase in arterial mean blood‐pressure (+33%, P<0–001, n=9) was obtained by infusion of angiotensin II and a decrease in pressure (‐10%, P, <0–005, n=6) was obtained by ganglionic blockade. The concentration of SP in plasma, from supine subjects in the normotensive condition, ranged from 3 to 13 pmol/1 (with a mean of 5–6 pmol/1). SP was thus within the reference interval: 3–16 pmol/1 (n.s.). Plasma SP remained very constant in each subject during the changes in blood‐pressure (mean variation in plasma concentration of SP was 0–97 (SD) pmol/1). The results show that acute changes in arterial blood‐pressure do not result in any detectable change in plasma SP, this seems to indicate that endogenous circulating SP has no significant role in the vascular tonus controlled by the arterial baroreflex.
Serum lipoprotein lipids and haematological variables in veteran runners, before and after a 2100 km relay run
Authors: Nye E. R. , Sutherland W. H. F. , Jefferson N. R. , Robertson M. C.
Published: April 2008

Summary. Plasma lipids and lipoprotein lipids, body characteristics, serum insulin concentration, distance run during training and haematological variables were determined in nine men aged between 62 and 72 years and who were regular runners. Multiple regression analysis showed that much of the variation in HDL cholesterol levels was explained by plasma triglycerides, and, to a lesser extent, by the distance run during training; although these variables contributed about equally to the variation in plasma HDL2 cholesterol levels. The effects on measured variables of a 2100 km relay, run over a 17‐day period, were also studied. During the relay the men were running an average 20% further, per week, than during their training before the relay. Plasma LDL cholesterol concentration, red blood cell volume, red cell count and haemoglobin levels fell significantly during the relay, and in three men raised serum insulin levels were reduced to within the normal range. Reticulocyte counts were not raised after the relay which suggests that the anaemia, seen in these men, was not due to erythrocyte destruction. The results indicate that in elderly runners, plasma triglycerides are an important predictor of plasma HDL cholesterol levels.
Cardiovascular responses and plasma catecholamines in old age
Authors: Sachs Charlotte , Hamberger Bertil , Kaijser Lennart
Published: April 2008

Summary. Plasma catecholamines and haemodynamic responses to isometric handgrip, orthostatic body position and dynamic cycle exercise were studied in 10 healthy old men (mean age 71 years) and 10 healthy young men (mean age 26 years). At rest, plasma noradrenaline (NA) was significantly higher in the old age group. During handgrip there were greater increases in heart rate and blood‐pressure in the young rather than in the old men, while forearm blood‐flow increase was similar in the two age groups, and there was no increase in NA in either groups. In the orthostatic position heart rate increased in the young men only, and forearm blood‐flow decreased more in the young than in the old men. NA concentration increased similarly in both age groups. During dynamic exercise the increases in both the heart rate and the blood‐pressure, at similar relative submaximal as well as maximal loads, were smaller in the old men. At maximal work NA and adrenaline (A) concentrations were higher in the young men, while at the lowest load, NA concentration was higher in the old men. Similar increases in exercise heart rate, blood‐pressure or rate of perceived exertion corresponded to lower increases in NA in the old men.

It can be concluded that old men, compared with young men, have a reduced maximal capacity to release NA and A upon provocation. In addition, the sensitivity for catecholamines in the target organ is reduced with age, as suggested by the smaller increases in heart rate and blood‐pressure for a given increase in NA during exercise. The higher basal NA level and the higher NA level, during moderate provocation, may suggest a compensatory increase in activity.
Effects of carbon dioxide and pH on myocardial blood‐flow and metabolism in the dog
Authors: Wexels Jan C. , Myhre Eivind S. P. , Mjøs Ole D.
Published: April 2008

Summary. The relative importance of pCO2 versus pH in regulating myocardial blood‐flow (MBF) is not settled. Therefore, the influence of hypocapnia, hypercapnia and sodium carbonate infusion, on MBF and myocardial metabolism, has been investigated in 10 closed‐chest pentobarbital anaesthetized dogs. The animals were hyperventilated, and CO2 was added to the inspiratory gas to induce normocapnia and hypercapnia. A mass spectrograph continuously measured the ventilatory gas components, and MBF was measured by the hydrogen desaturation technique with a catheter positioned in the coronary sinus. During the experiments, there were no significant alterations in heart rate, mean aortic blood‐pressure, myocardial oxygen consumption or uptake of glucose and free fatty acids. During hypocapnia MBF was insignificantly reduced, while myocardial oxygen extraction increased significantly. During hypercapnia, however, MBF increased more than 40%. This increase in MBF was abolished following an infusion of sodium carbonate. Thus, in the present study, increased MBF, observed during hypercapnia, was due to the reduction in pH and not to the increase in pCO2.
Plasma clearance of noradrenaline does not change with age in normal subjects
Authors: Hilsted J. , Christensen N. J. , Larsen S.
Published: April 2008

Summary.Noradrenaline kinetics (plasma concentrations, plasma clearance and appearance rates) were investigated in seven elderly healthy subjects and in six young healthy subjects. Forearm venous plasma noradrenaline concentrations were higher in the elderly subjects compared with the young subjects. Plasma clearance of noradrenaline was identical in the two groups. The increase in plasma noradrenaline concentration, with age, probably reflects an increased sympathetic nervous activity.
Metabolic effects of low and high doses of insulin during beta‐receptor blockade in dogs
Authors: Reikerås Olav , Gunnes Pål , Sørlie Dag , Ekroth Rolf
Published: April 2008

Summary. Metabolic effects of low and high doses of insulin during beta‐receptor blockade were studied in eight dogs. Beta‐receptor blockade was induced by 0.5 mg/kg propranolol which caused depression of heart performance. This was accompanied by a significant reduction in myocardial blood‐flow and oxygen consumption. There was also a significant reduction in arterial concentrations and myocardial uptake of free fatty acids, while arterial concentrations and myocardial uptake of glucose and lactate were not significantly changed. Fifteen minutes after beta receptor blockade, an intravenous (i.v.) bolus injection of 0.5IU/kg, of insulin, free of glucagon and calcium, was given followed by a continuous infusion of 0.5 IU/kg/h. Glucose and potassium were given to maintain constant levels of these factors. After 30 min another bolus dose of 300 IU insulin was injected. Thirty minutes after a low dose of insulin, a significant increase in heart performance was recorded at unaltered myocardial oxygen consumption. Arterial concentrations of free fatty acids were significantly reduced while levels of glucose and lactate were unchanged. Myocardial uptake of glucose increased significantly while uptake of lactate and free fatty acids was unchanged. After a high dose of insulin there was a considerable improvement in heart performance. Myocardial blood‐flow and oxygen consumption were not changed, nor were there alterations in arterial concentrations and myocardial uptake of glucose, lactate and free fatty acids. It is concluded that, during beta‐receptor blockade high doses of insulin improve the mechanical performance of the heart through mechanisms that are independent of insulin's effects on substrate metabolism.
Effect of hyperthyroidism on fibre‐type composition, fibre area, glycogen content and enzyme activity in human skeletal muscle
Authors: Celsing F. , Blomstrand E. , Melichna J. , Terrados N. , Clausen N. , Lins P.‐E. , Jansson E.
Published: April 2008

Summary. Seven hyperthyroid patients were studied by repeated muscle biopsies (vastus lateralis) before and after a period of medical treatment which averaged 10 months. The biopsies were analysed with regard to fibre‐type composition, fibre area, capillary density, glycogen content and enzyme activities representing the glycolytic capacity (hexokinase, 6‐phosphofructokinase), oxidative capacity (oxoglutarate dehydrogenase, citrate synthase) and Ca2+‐ and Mg2+‐stimulated ATPase in muscle. In the pretreatment biopsy (hyperthyroid state), there was a significantly lower proportion of type I fibres (30% vs. 41%), a higher capillary density (23%), lower glycogen content (33%), and higher hexokinase activity (32%) compared with the post‐treatment biopsy. No significant changes in the activity of the remaining enzymes were observed. The present study indicates that hyperthyroidism induces a transformation from type I to type II fibres in human skeletal muscle. The increase in hexokinase activity probably reflects a higher glucose utilization by skeletal muscle in order to compensate partially for the reduced glycogen content.
Glucose uptake and binding of digoxin to skeletal muscle
Authors: Joreteg T. , Efendic S. , Jogestrand T.
Published: April 2008

Summary. Physical exercise induces increased uptake of both digoxin and glucose in exercising skeletal muscle. Glucose uptake could be a regulatory factor for the digoxin binding to skeletal muscle, since in dogs, insulin and glucose infusion have been reported to increase the uptake of digoxin in muscle. In the present study on eight healthy digitalized subjects (0·5 mg digoxin daily) the uptake of glucose in skeletal muscle was achieved by infusion of 6 mg/kg body weight/min glucose, 0·004 IE/kg body weight/min insulin and 300 μg/h somatostatin. Serum and skeletal muscle digoxin levels were analysed before and during the infusion. We found no changes in the digoxin levels in serum and skeletal muscle in spite of an increased uptake of glucose in the muscle. Thus, glucose uptake in skeletal muscle is probably not an important regulatory factor for the change in muscle digoxin binding induced by exercise.
Ramp‐function work test suitable for automatic computation
Authors: Samuelsson P. J. , Gill H. , Lassvik C. , Linnarsson D. , Wigertz O.
Published: April 2008

Summary.Heart rate (HR) response to step‐function and ramp‐function (20 W/min) work tests was compared in 12 healthy subjects. For a given power output (P),HRwas substantially lower in the ramp tests. TheHRdifference increased with power output and increasing difference in work time between the test types. TheHRdifference can be explained in terms of a drift component (which accounts for 1/3 of the difference) and a lag component (2/3). As a consequence of theHRdifferences,Pfor a givenHRis higher in ramp tests. Work capacity expressed, for example as P170, can be determined in ramp tests, and the result can be translated to step‐function P170. The precision in this translation is markedly improved if a steady‐state period is incorporated into the ramp test.
Capillary filtration coefficient in the forearm of patients with essential hypertension
Authors: Roztočil K. , Přerovský I. , Oliva I.
Published: April 2008

Summary.The capillary filtration coefficient (CFC) in the forearm was followed in patients with essential hypertension and compared with controls, using the method of venous occlusion plethysmography and simultaneous recording of intravenous pressure in the measured segment of the extremity. Arterial blood‐pressure was obtained in the contralateral arm by auscultation. The CFC averaged 0.0039±0.009 ml/ 100 ml/min/mmHg and 0.0095±0.0018 ml/100 ml/min/mmHg in hypertensives and controls respectively. The relation between CFC and arterial blood‐pressure values was inversely non‐linear. The results suggest reduction of the capillary area due to hypertension and possibly functional or structural changes in the microcirculatory bed accompanying systemic blood‐pressure increase.
Pulmonary clearance of inhaled 99mTc‐DTPA: effect of surfactant depletion in rabbits
Authors: Wollmer P. , Evander E. , Jonson B. , Lachmann B.
Published: April 2008

Summary. We examined the effect of surfactant depletion on the rate of pulmonary clearance of inhaled 99mTc‐diethyl‐triamino‐penta‐acetate (DTPA). 99mTc‐DTPA was administered as a fine aerosol to four control animals and to four animals after wash‐out of pulmonary surfactant. Care was taken to minimize structural damage to the lavaged lungs. Clearance of 99mTc‐DTPA was measured over the right lung by external counting. The clearance rate was substantially increased in the lavaged animals compared to the control animals.

We conclude that the pulmonary surfactant system is a rate‐limiting factor for the absorption of inhaled 99mTc‐DTPA. Measurement of the pulmonary clearance of 99mTc‐DTPA may provide a new means for studying the pathogenetic role of the surfactant system in a variety of lung diseases.
A laser Doppler technique for measuring distal blood‐pressure: a comparison with conventional strain‐gauge technique
Authors: Andersson S. , Linderholm H. , Rinnström O. , Burlin L.
Published: April 2008

Summary. Twenty‐five patients with peripheral circulatory disorders were examined by laser Doppler and strain‐gauge techniques to compare these methods of measuring distal systolic blood‐pressure. The correlation coefficients for simultaneous measurement of toe and ankle systolic blood‐pressures were high, 0·98 and 0·99 respectively. The correlation coefficient for successive measurements of toe pressure was lower, 0·83, probably because of a variation in blood‐pressure with time. The laser Doppler method seems to be more sensitive than the strain‐gauge method in the low‐pressure range. The laser Doppler probe is easy to attach to most skin surfaces and the laser Doppler technique may be, therefore, an alternative and a complement to the strain‐gauge method when the strain‐gauge is difficult to use on damaged or ulcerous toes and feet.
Repeatability of fibre type and enzyme activity measurements in human skeletal muscle
Authors: Simoneau J.‐A. , Lortie G. , Boulay M. R. , Thibault M.‐C. , Bouchard C.
Published: April 2008

Summary. In order to assess the variability in repeated determination of human muscle fibre type distribution, fibre area and enzyme activity measurements, two biopsies were taken within 10 days in the same vastus lateralis for 12 females and 13 males, and in the right and in the left muscles for 25 other subjects (13 females and 12 males). Within muscle, intraclass reliability coefficients were 0·88, 0·82 and 0·56 for type I, IIa and IIb per cent fibres, respectively, and ranged from 0·74 to 0·82 for fibre areas and from 0·71 to 0·90 for enzyme markers of different metabolic pathways. Correlations between right and left muscle measurements were also high for fibre areas (from 0·85 to 0·91) and enzyme activities (from 0·71 to 0·87), except for phosphofructokinase (r=0·63). In contrast, the right and left thigh muscle correlation reached 0·67, 0·40 and 0·64 for type I, IIa and IIb fibre distribution, respectively. Thus, the variation in muscle sampling and technical procedures reached about 15% of the total variation (i.e. total differences between subjects) for the proportion of fibre type I and IIa and about 20–25% for fibre areas and enzyme activities. On the other hand, the technical error for the proportion of fibre type I and IIa is about 6–7%. This implies that differences brought about by any experimental treatment on these skeletal muscle characteristics in human studies have to be of a relatively large magnitude before being detectable. On the other hand, fibre areas and enzyme activities measured in single needle biopsy sample, from one of the vastus lateralis muscles, are quite representative of the other vastus lateralis. Similarity in fibre type proportion between right and left vastus lateralis cannot be postulated, however, without investigating both muscles.
Forearm composition and muscle function in trained and untrained limbs
Authors: Maughan R. J. , Abel R. W. , Watson J. S. , Weir J.
Published: April 2008

Summary. The influence of a period of training, which lasts for several years, on the proportions of muscle, fat and bone present in the human forearm has been investigated by comparing trained and untrained limbs of nine experienced male tennis players. Ten healthy but untrained males of similar age served as a control group. Computed tomography (CT) scans of the forearm were made at intervals along its length to identify fat, muscle and bone and to calculate the volumes occupied by each of these components. Total forearm volume was greater in the dominant limb compared with the contralateral side in both trained (by 135±59 cm3, mean±SD, P<0·001) and untrained subjects (by 41±45 cm3, P<0·02). Forearm muscle volume was also greater in dominant limbs of trained (by 117±52 cm3, P<0·001) and untrained by 35±41 cm3, P<0·025) subjects. Muscle accounted for 75·4±2·7% of the total volume in the dominant arm of trained subjects compared with 71·4±4·2% in the control group (P<0·05). There was a greater proportion of muscle (P<0·05) and a smaller proportion of fat (P<0·001) in the trained limb compared with the contralateral limb of the same subjects. No differences in proportions of fat, muscle and bone were observed in dominant and non‐dominant limbs of the control subjects. Trained subjects were able to exert a greater isometric force with the dominant limb (549±76N) than with the non‐dominant limb (496±48N; P<0·005). There was no difference in grip strength between the arms of the untrained group (dominant: 516±107N; non‐dominant: 491±91N). The ratio of strength to muscle volume was, however, the same in dominant and non‐dominant arms of both groups of subjects.
Repeatability of the single‐breath method for estimation of pulmonary blood‐flow: comparison among four data‐reduction procedures
Authors: Christensen P. , Grønlund J.
Published: April 2008

Summary. The single‐breath method of Kim, Rahn and Farhi (1966) enables the estimation of the pulmonary blood‐flow from the Pco2 vs. Pco2 curve recorded during a prolonged expiration. Studies on the repeatability of the method have given very different results. At one extreme the estimated pulmonary blood flows ranged from —47 to 173 litre/min and at the other extreme the repeatability was found to be better than that usually reported for invasive methods. A possible explanation for these important differences is the use of different data‐reduction procedures to calculate the pulmonary blood‐flow from the measured Pco2 and Po2 values.

In the present study we have investigated the repeatability of the single‐breath method in 20 test subjects using four previously published data‐reduction procedures. Furthermore, we have studied the sensitivity of the estimated pulmonary blood‐flow to measurement noise for each of the four data‐reduction procedures, by using a previously described technique based on computer simulations. Three of the data‐reduction procedures gave standard deviations on repeated single determinations of the pulmonary blood‐flow of about 1 litre/min whereas the last method gave results which fluctuated wildly from one determination to the next. The simulation showed that about 1/3 of the random variations can be ascribed to the measurement noise in Pco2 and Po2.
Evaluation of a modified acetylene rebreathing method for the determination of cardiac output
Authors: Nyström J. , Celsing F. , Carlens P. , Ekblom B. , Ring P.
Published: April 2008

Summary. In order to evaluate a computerized modified acetylene rebreathing method for the determination of cardiac output, 15 healthy subjects were studied at different levels of their maximal oxygen uptake (V̇o2max). Submaximal exercise was performed on a cycle ergometer and maximal exercise on a treadmill. Oxygen uptake, heart rate, and cardiac output (acetylene method) were determined in all test situations. In seven subjects simultaneous determinations of cardiac output were made by a modified acetylene rebreathing method (Q̇A) and a dye dilution method (Q̇D) Furthermore, a new resting rebreathing technique was used. The methodological error for (Q̇A)(means of double samples) was 0·37 litre min‐1 (2·8%) in the same individual at 150 W. The corresponding values between individuals were 0·71 (rest), 0·41 (50 W), 0·69 (150 W), and 0·40 litre min‐1 (V̇o2max). Thus the methodological error of the modified acetylene method was very low. There was a significant difference (P<0·01), however, between the acetylene method and the dye dilution method, which showed a lower value for Q̇A at all levels. This was probably due to the long response time of the mass spectrometer combined with anatomical and physiological arteriovenous shunt effects in the lungs during exercise. When these factors were considered the correcting formula was:Q̇Ac=Q̇A+0·005·Q2A There was no significant difference between the corrected cardiac output values (Q̇Ac) and the corresponding Q̇D values. In conclusion, this modified acetylene rebreathing method is a very useful non‐invasive method for measuring cardiac output at rest as well as during heavy exercise.
Left main or proximal left anterior descending coronary artery disease: detection by echocardiographic evaluation of interventricular septal function during exercise
Authors: Andersen K. , Vik‐Mo H. , Hoff P. I.
Published: April 2008

Summary. Forty patients with coronary artery disease were studied prospectively to investigate whether stenosis of the left main (LMCA) or left anterior descending coronary artery, proximal to the first septal branch (proximal LAD), could be detected by M‐mode echocardiography during exertion. The interventricular septum was visualized in 30 of the patients during bicycle exercise in the semisupine position, all with simultaneous occurrence of electrocardiographic evidence of myocardial ischaemia. Fifteen of these had LMCA or proximal LAD stenosis. Systolic motion and thickening of the septum decreased significantly from rest to peak exercise in patients with LMCA or proximal LAD disease while it increased in those without. The results suggest that M‐mode echocardiography during exercise in patients with coronary artery disease might identify those with LMCA or proximal LAD stenosis.
Venous plasma adrenaline response to orthostatic syncope during tilting in healthy men
Authors: Tatár P. , Bulas J. , Kvetňanský R. , Štrec V.
Published: April 2008

Summary. The effect of transient cerebral ischaemia connected with acute orthostatic hypotension on plasma adrenaline and noradrenaline levels was studied in seven healthy male volunteers during tilt. Sublingual administration of 1 mg nitroglycerin was used to block peripheral vascular reflexes and thus to provoke orthostatic intolerance. A consistent increase in plasma adrenaline concentrations (from 19·2 to 104·3 pg/ml on average, P<0·01) was found in six subjects who developed clinical signs of collapse after tilting. Plasma adrenaline never changed after tilting without collapse. Posturally stimulated plasma noradrenaline increases were similar yet irrespective of the presence of collapse.
Transthoracic electrical impedance at 1 and 100 kHz ‐ a means for separating thoracic fluid compartments?
Authors: Larsen F. F. , Mogensen L. , Tedner B.
Published: April 2008

Summary. The electrical impedance of biological tissues varies with their water and electrolyte contents. Alternating current above 5–10 kHz passes both intra‐ and extracellular fluid, and lower frequency current preferentially extracellular fluid. In an attempt to evaluate thoracic fluid in different compartments, transthoracic electrical impedance (TEI) was measured at 1 and 100 kHz in 15 consecutive patients, without overt left heart failure and under haemodynamic surveillance, during the first two days of myocardial infarction. To achieve different states of hydration the patients were given i.v. furosemide, either 40 mg t.i.d. (high dose group—HDG) or 20 mg once daily (low dose group—LDG). Effects of altered body position and the respective furosemide injections, were evaluated on both days.

Mean 24‐h‐diuresis was 3·9 1 in the HDG and 2·5 I in the LDG. After 24 h mean pulmonary arterial diastolic pressure had decreased by 30% in the HDG but remained almost unchanged in the LDG. By then mean basal TEI was increased only in the HDG, by 17% at 1 kHz and 13% at 100 kHz. On Day 1, within one hour after furosemide, TEI increased temporarily by 3–5%, at both frequencies and in both groups. On Day 2, this short‐term increase was similar in the LDG at both frequencies and in the HDG at 100 kHz, but not at 1 kHz, consistent with a major extracellular fluid loss in the HDG. TEI at 1 and 100 kHz may thus reflect extracellular and total thoracic fluid, respectively.
Heart rate response to breathing: dependency upon breathing pattern
Authors: Mehlsen J. , Pagh K. , Nielsen J. S. , Sestoft L. , Nielsen S. L.
Published: April 2008

Summary. Heart rate responses to stepwise and periodic changes in lung volume were studied in seven young healthy males. Stepwise inspiration and expiration both resulted in an increase in heart rate followed by a rapid decrease in heart rate. The fastest heart rate was reached in 1·6 ± 0·5 s and in 3·6 ± 1·4 s in response to inspiration and expiration, respectively (P < 0·01). The slowest heart rate was reached in 4·8± 1·0 s and in 7·6± 1·9 s in response to inspiration and expiration, respectively (P < 0·01). Following this biphasic change the heart rate returned to a steady level. The difference between the fastest and the slowest heart rates was significantly larger in response to inspiration (21·7 ± 7·3 beats per minute) than in response to expiration (12·0±7·3 beats per minute; P < 0·01). Periodic changes in lung volume were performed with frequencies from 3·0 to 12·0 respirations per minute (r.p.m.). The changes in heart rate showed a constant amplitude in the frequency range below 5·5 r.p.m. Maximal heart rate changes were found at frequencies of 5·5 to 7·0 r.p.m. Changes in heart rate decreased in a linear manner on a log‐log scale in the frequency range above 7·0 r.p.m. The relation between frequency and changes in heart rate is explained by interference between the transient changes in heart rate induced both by inspiration and by expiration. It is concluded that if heart rate changes in response to periodic changes in lung volume are to be used as a measure of vagal function a number of factors have to be taken into consideration and to simplify the analysis of heart rate responses to breathing we recommend, instead, the use of the transient changes in heart rate induced by stepwise changes in lung volume.
Organ extraction of atrial natriuretic peptide (ANP) in man. Significance of sampling site
Authors: Schütten H. J. , Henriksen J. H. , Warberg J.
Published: April 2008

Summary. Arterial plasma immunoreactivity of endogenous human α‐atrial natriuretic peptidei1–28 (ANP) underwent mean 54%, 28% and 40% extraction during one passage through the circulation in the kidney (n= 12), liver‐intestine (n=14) and lower limb (n= 8), respectively, in supine fasting subjects with no detectable disease or subjects with cardiovascular or hepatic disorders of minor degree undergoing a haemodynamic investigation. No extraction was identified across the lungs as evaluated by the same concentration of ANP in pulmonary and femoral arteries (n= 7). The concentration of ANP in a superficial arm vein relative to the femoral artery varied considerably and extractions from 0% up to 58% were identified (mean 18%). The results suggest a high degree of, but only to some extent selective, extraction of ANP, which may account for its proposed short plasma half‐life. Due to the different concentrations of ANP in various vascular beds, sampling site should be thoroughly specified.
Contractile properties of the human triceps surae following prolonged exercise and β‐blockade
Authors: Alway S. E. , Hughson R. L. , Green H. J. , Patla A. E. , Frank J. S.
Published: April 2008

Summary. Sixteen healthy males volunteered to perform both an incremental maximal and prolonged submaximal treadmill test with β‐blockade (2 × 80 mg oral propranolol per day) or matched placebo in a blind crossover design. Prior to and following the prolonged exercise, electrical stimulation of the triceps surae was performed to examine contractile properties. During the maximal test, the heart rate (HR) was reduced at all times by β‐blockade. The time to exhaustion in this test was significantly reduced by β‐blockade (P < 0·03), while the maximal oxygen uptake (VO2max) was not significantly lower (P= 0·06). In response to prolonged treadmill walking at 60% of VO2max, the HR was reduced but VO2, respiratory quotient and ventilation were not affected by β‐blockade relative to placebo. Plasma concentrations of free fatty acids increased during exercise in the placebo but not β‐blocked treatment (P < 0·0001). Plasma noradrenalin and adrenalin increased with exercise; the increase in adrenalin with β‐blockade was greater than that with placebo (P < 0·001). The RPE obtained at intervals during the prolonged exercise were greater for β‐blockades than placebo. Eight of 16 subjects were unable to complete full 90 min with β‐blockade; but all 16 completed the test with placebo. The electrically evoked twitches in the triceps surae muscle group after exercise did not differ in peak torque or one‐half relaxation time compared to pre‐exercise. The time to peak twitch torque was significantly shorter after exercise. No differences in twitch were observed due to β‐blockade. The tetanic responses at 10, 20, 50 and 100 Hz were not affected by either exercise or the β‐blockade. In conclusion, an increased subjective estimate of fatigue (RPE) was observed during prolonged exercise with β‐blockade. This subjective fatigue did not relate to altered peripheral muscle force production during electrical stimulation. The results suggest either a central rather than peripheral origin of fatigue, or fatigue in a muscle group not examined by stimulation of the triceps surae.
Renal fraction of cardiac output cleared of radioactive indicator in 123iodine‐hippuran gamma camera renography
Authors: Carlsen O. , Nathan E.
Published: April 2008

Summary. The renal images recorded during 1–2 min post‐injection in 121I‐hippuran gamma camera renography were used for determination of the total cleared renal fraction (TCRF) of cardiac output with respect to the radioactive indicator. In a study of sixty‐seven normal children over two years old TCRF was 0·178 ± 0·026 (x̄± 1 SEE). This was in agreement with the estimation of TCRF from values of renal fraction of cardiac output and renal extraction ratio of hippuran in the literature. The left and right cleared renal fractions of cardiac output were determined directly, i.e., assessment of single kidney uptake function within a few minutes post‐injection was also possible. TCRF was closely related to the glomerular filtration rate (GFR) in a group of twenty‐two subjects with GFR in the interval 20–130 ml/min/1·73 m2. Intra‐observer variability of TCRF was unbiased and equal to 4%. TCRF is proposed to represent an alternative to renal clearance for evaluation of renal uptake function.
Insulin sensitivity in patients with arterial insufficiency. Re‐evaluation with the Multilevel Glucose Clamp Technique
Authors: Lundgren F. , Lundholm K. , Ekroth R. , Holm J. , Scherstén T.
Published: April 2008

Summary. Previous studies have claimed that changes in insulin and glucose metabolism in patients with peripheral arterial insufficiency indicate an increased sensitivity to insulin for glucose uptake. We have re‐evaluated this concept in 11 patients with intermittent claudication and 11 matched controls with a multilevel euglycaemic glucose clamp technique. The groups were matched for age, sex and body composition but not completely for smoking habits and physical fitness. Although the control group had a normal physical fitness the patients had 40% lower maximal exercising capacity. The patients' maximal walking capacity was 186 ± 27 m evaluated on a treadmill. No patient with ischaemic ulcers or rest pain were included. The euglycaemic glucose clamp was performed at five insulin plateau levels (70, 110, 190, 590 and 1440 mU/l) of one h duration each and whole body glucose uptake during the last 20 min was calculated. No differences in maximal glucose uptake (Vmax) or insulin level for half maximal glucose uptake (Km) between the groups were observed. The concentration or the magnitude of the decrease in arterial FFA levels did not differ significantly between the groups at any physiological insulin level.

This study can not confirm previously described changes in insulin sensitivity in patients with arterial insufficiency. Although the discrepancy between present and previous results remains unclear it may reflect the combined effects of different methods used, including the selection of reference patients, rather than an increased insulin sensitivity in patients with arterial insufficiency. This study suggests that previous conclusions based on glucose tolerance tests should be interpreted with caution.
Radionuclide left ventricular volume determination. Influence of scattered radiation and surrounding activity
Authors: Boström P. Å. , Hemdal B. , Ahlgren L. , Svensson M. , Lecerof H. , Lilja B.
Published: April 2008

Summary. Radionuclide measurements of left ventricular volumes, ejection fractions and stroke volumes were performed by an equilibrium technique in nine patients using left anterior oblique projection and individual depth correction. Phantom studies were made in order to evaluate attenuation and scattering of the radiation. It was found that a simple depth correction factor, k(d)= eμd, can be used under certain conditions. However, the determination of left ventricular volume by radionuclide techniques is not a truly absolute method. The depth correction factor to be used is dependent on the condition of measuring and evaluation, for instance how the region of interest for the left ventricle is selected. Therefore, this method should be carefully standardized, evaluated and compared to other techniques. Stroke volume measured by radionuclide and dye‐dilution technique showed a correlation coefficient of 0·76 (nine patients) at rest and 0·77 (seven patients) at work. This method can be easily performed during routine ejection fraction determination and can thus be useful in clinical studies.
Effects of triglycyl‐lysine‐vasopressin on cardiovascular responses to orthostatic stress
Authors: Baer R. , Eiken O. , Balldin U.
Published: April 2008

Summary. The influence of triglycyl‐lysine‐vasopressin (TGLVP) on cardiovascular responses to orthostatic stress was studied. Arterial pressures, heart rate (HR) and stroke volume (SV) were measured in eight healthy males subjected to 20 min 70° head‐up tilt. On different days they received either 0·01 mg/kg b.w. of TGLVP or a corresponding volume of 0·9% saline i.v. after 15 min supine rest. After the drug injection, in supine subjects, HR had decreased from 58 to 50 beats min‐1, total peripheral resistance (TPR) was elevated by 29%, systolic (SAP) and diastolic pressure (DAP) had increased by 7 and 8 mmHg, respectively. During tilt, values for HR and SAP were similar with and without TGLVP whereas DAP and MAP were elevated 8 and 7 mmHg, respectively, by the drug. 4–8 min into the tilt, TGLVP caused an 8% sustained curtailment of SV. Both with and without the drug TPR increased by about 30% in response to head‐up tilt. Thus, the marked peripheral arteriolar constriction after vasopressin in the supine position was not affected by head‐up tilt. Tilting also abolished the drug‐induced elevation in SAP, most likely explained by the reduction in SV. Although TPR was markedly increased by TGLVP during head‐up tilt, reflected in the behaviour of DAP, the response of SV speaks against any beneficial effect of this drug on orthostatic tolerance in healthy subjects.
The transfer factor (diffusing capacity) as a predictor of hypoxaemia during exercise in restrictive and chronic obstructive pulmonary disease
Authors: Nordenfelt I. , Svensson G.
Published: April 2008

Summary. Thirty patients (17 with restrictive, eight with chronic obstructive pulmonary disease and five with combined pulmonary changes) were studied. Ordinary pulmonary function tests were made and in addition the transfer factor (diffusion capacity) was measured at rest and compared to the arterial oxygen tension at rest and during maximal exercise. There was a significant correlation (r = 0–89) between the transfer factor at rest and the oxygen tension during maximal exercise in both the patients with restrictive and those with obstructive lung disease, but no correlation was found between the transfer factor and the resting oxygen tension. Exercise induced hypoxaemia (Po2< 8‐8‐5 kPa) occurred in some patients and this could be predicted with an excellent sensitivity and specificity if a discrimination point for the transfer factor of 50 per cent of predicted or less was chosen. Determination of the transfer factor at rest is thus a good screening test for exertional hypoxaemia and can be used to select patients for exercise testing when the purpose is to detect hypoxaemia.
Glucose tolerance and lipid‐lipoprotein levels in middle‐aged powerlifters
Authors: Hurley B. F. , Hagberg J. M. , Seals D. R. , Ehsani A. A. , Goldberg A. P. , Holloszy J. O.
Published: April 2008

Summary. The purpose of this study was to obtain information regarding the effects of a form of strength training (powerlifting) on certain coronary artery disease (CAD) risk factors in middle‐aged men. The risk factors studied were the plasma lipid‐lipoprotein profile, glucose tolerance and plasma insulin levels, all of which have been shown to be favourably influenced by endurance training in middle‐aged and older men. Five elite powerlifters (52±9 years) were compared to distance runners and sedentary controls of similar age with whom they were matched in terms of body fatness as estimated from skinfold thickness measurements. The powerlifters had a significantly (P < 0·01) lower HDL cholesterol (HDL‐C) level (34±4 mg/100 ml) than the sedentary controls (48±12 mg/100 ml) and runners (54±8 mg/100 ml). The total cholesterol to HDL‐C ratio, a good indicator of CAD risk, was 41% higher in the powerlifters than in the controls, and 57% higher than in the runners (both P<0·01). The total area under the glucose tolerance curve during an oral glucose tolerance test (OGTT) for the powerlifters was 74% higher than for the sedentary controls (P<0·05) and 229% higher than for runners (P<0·01). Similarly, the total area under the OGTT insulin curve for the powerlifters was 68% higher than for sedentary controls and 332% higher than for the runners P<0·01). These findings suggest that middle‐aged powerlifters, in marked contrast to endurance athletes, have an increased risk of developing CAD.
Non‐invasive evaluation of the long‐term results of coarctectomy in childhood
Authors: Wallentin I. , Hanson E. , Eriksson B. O.
Published: April 2008

Summary. Nineteen young men operated upon for coarctation of the aorta in childhood were studied with pulse tracings from the femoral and carotid arteries and echocardiographic examination of the heart with estimation of the degree of hypertrophy and valve anomalies. The results were compared with intra‐arterial blood‐pressure measurements and angiographically measured width of the aortic anastomosis.

Patients with markedly distorted pulse curves had the narrowest anastomoses although no uniform pattern could be detected. Although one of the selection criteria was ‘no other known cardiovascular malformation’, only three of the patients had completely normal aortic and mitral valves. Nine of the patients had left ventricular hypertrophy but the degree of hypertrophy could not be correlated to the degree of arterial hypertension.

The importance of long‐term follow‐up of these patients, who in spite of surgery have a remaining cardiovascular excess mortality, is emphasized. Pulse tracings and echocardiography seem to be of value for this purpose.
Potassium and myoglobin release and ST and QRS vector changes during acute myocardial infarction
Authors: Sylvén C. , Sederholm M.
Published: April 2008

Summary. Thirty‐three consecutive patients aged 39 to 77 years with signs of myocardial infarction with a duration of symptoms of less than 4 h took part in the study. Serial blood sampling was done for the determination of myoglobin (MG), creatine‐kinase (CK) and potassium (K). Continuous vectorcardiography was monitored.

Peak rates of K and MG release occurred 7·0 ± 3·7 and 6·5 ± 3·9 hours, respectively, after the onset of symptoms not different from the end of ST vector change that occurred after 7·6 ± 2·8 h. Following the end of ST vector change there was a 4‐hour delay until the end of QRS vector change and another 8‐hour delay to the end of MG release occurring about 20 h after the onset of symptoms. At the time for peak rate of MG release 48 ± 17% of total MG release had occurred.

In conclusion, the physiologically different indicators of myocardial damage showed signs of maximum release within the same time range, 6–8 h after the onset symptoms and 8–10 h before signs of completed infarction.
The effect of exercise on platelet beta‐adrenoceptor function and platelet aggregation in healthy human volunteers
Authors: Winther K. , Trap‐Jensen J.
Published: April 2008

Summary. Plasma levels of adrenaline and noradrenaline, platelet cyclic‐AMP (cAMP) content, platelet aggregation, platelet release of beta‐thromboglobulin, and platelet factor 4 and serum content of thromboxane B2(TXB2) and 6‐keto‐PGF1α were measured in 12 healthy male volunteers (age 38–72, mean 54·2 years) who were tested at rest and immediately after five min light cycle exercise.

The plasma levels of adrenaline and noradrenaline increased significantly after exercise (P<0·01). The platelet cAMP level was not changed by exercise. The functional capacity of platelet beta‐adrenoceptors, determined as cAMP production after beta‐adrenoceptor stimulation in vitro, decreased highly significantly after exercise in all 12 volunteers (P<0·01). No alteration was observed in platelet aggregation induced by adrenaline or in platelet release of beta‐thromboglobulin or platelet factor 4. No change was observed in the serum levels of TXB2 and 6‐keto‐PGF1α.

In conclusion: light cycle exercise results in a decreased functional capacity of platelet beta‐adrenoceptors, but has no effect on platelet aggregation or platelet release. This might indicate a concomitant and equal decreased functional capacity of platelet alpha‐adrenoceptors.
Comparison of forearm plethysmography methods with brachial artery pulsed Doppler flowmetry in man
Authors: Safar M. E. , Daou J. E. , Safavian A. , London G. M.
Published: April 2008

Summary. Blood flow in the forearm was evaluated using simultaneous measurements of pulsed Doppler flowmetry and strain‐gauge plethysmography in 32 normal subjects and 91 patients with sustained essential hypertension. The two determinations of blood flow were strongly correlated (r = 0·58). Measurements with strain‐gauge plethysmography reflected changes in blood flow velocity but were poorly correlated with changes in arterial diameter as measured by pulsed Doppler flowmetry. The latter method permits evaluation of instantaneous variations in blood flow velocity and detection of active modifications of arterial diameter.