bluuebunny/crossref_metadata_2025 huggingface dataset:
Limiting factors for exercise at extreme altitudes
Authors: West J. B.
Published: April 2008

Summary. Man can only survive and do work in the severe oxygen deprivation of great altitudes by an enormous increase in ventilation which has the advantage of defending the alveolar Po2 against the reduced inspired Po2. Nevertheless the arterial Po2 on the summit of Mt Everest at rest is less than 30 Torr, and it decreases with exercise because of diffusion limitation within the lung. One of the consequences of the hyperventilation is that the marked respiratory alkalosis increases the oxygen affinity of the haemoglobin and assists in loading of oxygen by the pulmonary capillary. Although ventilation is greatly increased, it is a paradox that cardiac output for a given work level is the same in acclimatized subjects at high altitude as at sea level. Stroke volume is reduced but not because of impaired myocardial contractility because this is preserved up to extreme altitudes. Indeed the normal myocardium is one of the few tissues whose function is unimpaired by the very severe hypoxia. There is evidence that oxygen delivery to exercising muscle is diffusion limited along the pathway between the peripheral capillary and the mitochondria. At the altitude of Mt Everest, maximal oxygen uptake is reduced to 20–25% of its sea level value, and it is exquisitely sensitive to barometric pressure. Seasonal variations of barometric pressure affect the ability of man to reach the summit without supplementary oxygen. In spite of the greatly reduced aerobic capacity, anaerobiosis is greatly curtailed, and it is predicted that above 7500 m, there is no rise in blood lactate on exercise. The paradoxically low lactate is possibly related to plasma bicarbonate depletion.
Prognosis and diagnostic work‐up in patients admitted for, but without, myocardial infarction — the value of nuclear medicine examinations
Authors: Launbjerg J. , Fruergaard P. , Jørgensen F. B. , Madsen J. Kyst , Hesse B.
Published: April 2008

Summary. Patients admitted for acute myocardial infarction that is not confirmed (non‐AMI) have a prognosis only slightly better than that of patients with confirmed infarction. In a prospective, prognostic study of 158 patients with non‐AMI the combination of exercise ECG and transient defects demonstrated at 201thallium scintigraphy identified low‐ and high‐risk groups better than either examination alone.

The purpose of a new, still ongoing study of non‐AMI patients is to establish a relevant, cost‐effective examination programme in order to arrive at a positive diagnosis in each non‐AMI patient. Preliminary results of lung perfusion/ventilation scintigraphy suggest a rather low frequency of pulmonary embolism. Preliminary data of oesophageal scintigraphy suggest that about 25% of the non‐AMI patients have abnormal mean transit times. The clinical significance of these data are discussed.
Sympathetic activation during the cold pressor test: influence of stimulus area
Authors: Seals D. R.
Published: April 2008

Summary. The purpose of this study was to determine the effect of the size of the stimulus area on the muscle sympathetic nerve activity (MSNA), systolic arterial blood pressure (SAP), and heart rate responses to the cold pressor test. To accomplish this, these variables were measured before (control), during, and after 1·5 min of ice water immersion of either one or both hands in nine healthy subjects (aged 19–27 years). The cold stimulus elicited significant increases above control levels in all three variables under both conditions (P<0·05). Immersion of both hands produced a much greater increase in total MSNA (+366%) than immersion of a single hand (+187%) (P<0·05). However, the magnitudes of the increases in SAP and heart rate during two‐hand immersion (29±6 mmHg and 10±2 beats min‐1) were not significantly different from the responses during the one‐hand trials (24±5 mmHg and 6±2 beats min‐1, P>0·05). There was a strong, direct relationship between total MSNA and SAP responses during one‐hand immersion (r= 0·93, P<0·001) but not during immersion of both hands (r= 0·66, P= 0·08). These findings indicate that during the cold pressor test the magnitude of the increase in sympathetic discharge to skeletal muscle, but not the systolic blood pressure response, is influenced by the size of the tissue area exposed to the stimulus.
Regional perfusion in hearts with acute coronary artery occlusion and subsequent β2‐ and α1‐adrenergic blockade
Authors: Kvitting P. , Westby J. , Birkeland S. , Lekven J. , Grong K.
Published: April 2008

Summary. Blockade of cardiac adrenoceptor subtypes, coronary or myocardial, might elicit compensatory interaction from remaining unblocked subtypes. An attempt to explore this interplay was made by studying regional myocardial blood flow alterations associated with β2‐adrenergic blockade followed by β1‐adrenergic blockade in anaesthetized cats with acute coronary occlusion. In order to maintain constant needs for perfusion, atrial pacing was established and the aortic blood pressure was kept constant. In myocardium remote from the ischaemic region, β2‐adrenergic blockade produced higher endocardial blood flow whereas no flow changes were observed close to the ischaemic region. With subsequent β1‐adrenergic blockade, blood flow increased endocardially in non‐ischaemic regions, but remained unchanged in epicardial tissue. Control experiments without coronary ligation revealed no increase in left ventricular oxygen consumption during the experiments and support the theory that the observed blood flow increase in the coronary ligation group, following drug interventions, was not caused by increased cardiac work. This study indicates that combined β2‐ and α1‐adrenergic blockade alters the balance between receptor subtypes. Unopposed β1‐mediated vasodilation is the most likely candidate to explain why endocardial flow was increased.
Dissociation between vascular and metabolic effects of nicotinic acid in Gilbert's syndrome
Authors: Gentile S. , Marmo R. , Persico M. , Faccenda F. , Orlando C. , Rubba P.
Published: April 2008

Summary. The relationship between the vasodilating and the hyperbilirubinaemic effect of low and high doses (50 and 300 mg i.v.) of nicotinic acid was studied in baseline conditions and after indomethacin pretreatment in healthy controls and patients with Gilbert's syndrome (a condition characterized by fluctuating, nonhaemolytic unconjugated hyperbilirubinaemia). The hyperbilirubinaemic effect of nicotinic acid was confirmed to be more pronounced in Gilbert's syndrome patients than in controls. The magnitude of hyperbilirubinaemia in the two groups was not dependent on the dose of nicotinic acid or indomethacin pretreatment. A dose‐dependent vasodilation which was inhibited by indomethacin could be demonstrated in both controls and Gilbert's syndrome subjects. Vasodilating properties of nicotinic acid were therefore found to be dissociated from the effect on bilirubin.
Pulmonary clearance of inhaled [99Tcm]DTPA: effects of ventilation pattern
Authors: Evander E. , Wollmer P. , Jonson B.
Published: April 2008

Summary. While a rise in lung volume is known to increase the pulmonary clearance of technetium‐99m‐labelled dietylene triamine pentaacetate ([99Tcm]DTPA), little interest has been focused on the effects of changes in ventilation frequency, tidal volume and airway pressure. We studied adult, anaesthetized and intubated rabbits during three ventilation patterns (VP) using pressure controlled ventilation (Servo Ventilator 900C). VP was either deep slow (f=20 min‐1, tidal volume (VT) = 30 ± 4 ml kg‐1 and positive end‐expiratory pressure (PEEP) = 0·2 kPa [VP 20/ 0·2, n= 8]) or rapid shallow (f=80 min‐1, VT= 11 ±2 ml kg‐1 and PEEP = 0·2 or 0·4 kPa [VP 80/0·2, n= 6 and VP 80/0·4, n= 6]). The mean airway pressure was similar at VP 20/0·2 and VP 80/0·4. During administration of [99Tcm]DTPA aerosol all animals were ventilated under the same conditions (f=40 min‐1 and PEEP = 0·2 kPa). The pulmonary clearance rate expressed as the half‐life time (T1/2) of [99Tcm]DTPA was at VP 80/0·2 = 113 ± 31 min, at VP 80/0·4 = 70 ± 24 min (P < 0·01 compared to VP 80/0·2) and at VP 20/0·2 = 36± 18 min (P <0·001 compared to VP 80/0·2 and P <0·01 compared to VP 80/0·4).

We conclude that the pulmonary clearance of [99Tcm]DTPA increases

 during rapid shallow ventilation when PEEP is increased from 0·2 to 0·4 kPa;

 during deep slow ventilation relative to rapid shallow ventilation even when the mean airway pressure is similar.
Combined left and right ventricular volume determination by radionuclide angiocardiography using double bolus and equilibrium technique
Authors: Stokholm K. H. , Stubgaard M. , Møgelvang J. , Henriksen O.
Published: April 2008

Summary. Eighteen patients with ischaemic heart disease were studied. Left and right ventricular volumes including cardiac output (forward flow) were determined by radionuclide angiocardiography using a double bolus and equilibrium technique. As reference, cardiac output was simultaneously measured by indicator dilution. The radionuclide technique comprised four steps:

a first‐pass study of right ventricle;

a bolus study of left ventricle;

an equilibrium study of left ventricle;

determination of the distribution volume of red blood cells.

Absolute volumes of left ventricle were determined from steps 2+3+4. Absolute volumes of right ventricle were calculated from stroke volume and right ventricular ejection fraction (EF) which in turn was determined from step 1 by creating composite systolic and composite diastolic images. There was an acceptable agreement between stroke volume determinations by radionuclide angiocardiography and indicator dilution (r= 0.74; P<0.001). Stroke volume determination by radionuclide was 83±20 ml (mean±SD) and by indicator dilution 84±20 ml with a difference of ‐1±15 ml (NS). Cardiac output determination by radionuclide was 5.24±1.37 1 min‐1 and by indicator dilution 5.28±1.23 1 min‐1 with a difference of ‐0.04±0.95 1 min‐1 (NS). Left ventricular EF was 0.44 ±0.14 and right ventricular EF 0.57 ±0.10. The intra‐observer coefficient of variation for duplicate calculations of the radionuclide determinations was 5.5% for stroke volume, 2.5% for left ventricular EF and 4–8% for right ventricular EF.
Reflex actions of knee joint afferents during contraction of the human quadriceps
Authors: Iles J. F. , Stokes M. , Young A.
Published: April 2008

The spinal reflex actions of afferents stimulated by knee joint distension have been investigated in man.

Cannulation of the knee and infusion of saline raised intra‐articular pressure, especially during quadriceps contraction. High pressures did not induce any sensation of pain. Pressure was taken as an index of joint proprioceptor activation.

Increased pressure progressively depressed the quadriceps H‐reflex, both at rest and during quadriceps contraction. There was no indication of a threshold pressure for this inhibitory action.

It is concluded that joint distension inhibits quadriceps motoneurons through spinal pathways that still operate during voluntary contraction. These pathways could thus contribute to pathological weakness after joint injury.

Joint distension produced spatial facilitation of non‐reciprocal inhibition of quadriceps H‐reflexes from afferents in the tibia1 nerve.
Coronary artery constriction is enhanced with nicotine and propranolol, particularly after endothelial damage
Authors: Sousa P. De , Cherian G. , Thomas J. , Thulesius O.
Published: April 2008

Summary. Coronary artery ring preparations from sheep were used for in vitro assessment of isometric tension after stimulation with adrenaline (NA), serotonin (5‐HT)and nicotine (NC). From concentration‐response curves the following observations were made on potency of agonists: 5‐HT>NC>NA and efficacy: 5‐HT = NC>NA. Removal of the intima increased sensitivity to stimulation with NA and 5‐HT (lower EC50 values) and augmented the maximal response. Preincubation of the vessels with NC and propranolol (PR) resulted in a leftward shift of the concentration‐response curves to NA and 5‐HT. Sensitivity and maximal response to NA and 5‐HT were further enhanced by endothelial removal and pre treatment with NC and PR. It can be concluded that vasoconstriction to NA and 5‐HT is enhanced by nicotine (smoking) and administration of β‐blockers (propranolol), particularly in coronary arteries with endothelial damage.
Effects of dobutamine and salbutamol on haemodynamics and atrial natriuretic factor in patients with severe congestive heart failure
Authors: Keller N. , Sykulski R. , Larsen J.
Published: April 2008

Summary. The influence of two cardiac inotropic drugs, dobutamine and salbutamol, on plasma atrial natriuretic factor (ANF) was investigated in 20 patients with congestive heart failure. All were in New York Heart Association class‐III or IV. The patients underwent right heart catheterization with determination of central pressures, cardiac output, and pulmonary arterial plasma ANF during incremental infusions with dobutamine or salbutamol. Fourteen patients completed the study. Both drugs induced comparable increases in cardiac index and decreases in total systemic vascular resistance (P < 0·01) without significant changes in central pressures. Heart rate rose after salbutamol (P < 0·05), but not after dobutamine. No changes in plasma ANF were observed after either of the drug infusions. ANF secretion rate was calculated from simultaneous measurements of ANF in right atrial and pulmonary arterial plasma before and after salbutamol infusion, and median values rose more than seven‐fold (P < 0·05). The results demonstrate that ANF secretion rate is augmented after β‐adrenergic agents, possibly by a direct β2‐adrenergic stimulation, in patients with severe congestive heart failure, and that changes in plasma ANF are an insufficient measure of ANF release when patient samples are small.
Initial circulatory responses to changes in posture: influence of the angle and speed of tilt
Authors: Sprangers R. L. H. , Veerman D. P. , Karemaker J. M. , Wieling W.
Published: April 2008

Summary. To assess if changes in the angle or speed of tilt could account for the differences between the initial (first 30 s) circulatory responses induced by active and passive changes in posture, as found in previous studies, we investigated the initial heart rate and blood pressure responses induced by stand up from supine and various head‐up tilt manoeuvres in 12 healthy, male subjects. Comparison was made between 70° head‐up tilt in 3 s, 90° head‐up tilt also in 3 s and 70° head‐up tilt in 1·5 s, using an automatic pneumatic‐driven tilt table with foot support.

It was found that the initial heart rate and blood pressure responses induced by the three tilt manoeuvres were almost identical in time course and amplitude, but significantly different from those induced by stand up.

The results of this study prove that regardless of the angle and speed of tilt, the initial circulatory responses induced by passive changes in posture are essentially different from the responses induced by active changes in posture.
Circulatory responses to stand up: discrimination between the effects of respiration, orthostasis and exercise
Authors: Sprangers R. L. H. , van Lieshout J. J. , Karemaker J. M. , Wesseling K. H. , Wieling W.
Published: April 2008

Summary. The initial circulatory responses to an active change in posture (stand up from supine) were compared with the responses induced by a passive change in posture (head‐up tilt) and a burst of muscular exercise on a bicycle ergometer (upright cycling) in order to differentiate between exercise‐ and orthostasis‐induced effects. In eight subjects heart rate responses and in four subjects intra‐arterial pressure transients were measured. In addition the effects of respiration on heart rate responses to the three manoeuvres were assessed.

Both stand up and cycling induced almost superimposable and pronounced heart rate responses lasting for about 30 s. This contrasts with the more gradual increases following head‐up tilt. Changing the respiratory phase during the performance of the manoeuvres exerted its effect on heart rate responses in the first 5 s only.

Like stand up, cycling induced a transient blood pressure fall lasting for 30 s on average. As both manoeuvres were performed during inspiration the transients observed are not caused by involuntary Valsalva straining.

In conclusion, the maximum and duration of the heart rate responses induced by stand up, cycling and head‐up tilt are not influenced by respiratory activity.

The initial fall in blood pressure following stand up is probably the result of the muscular effort of the manoeuvre and not due to the effects of orthostasis or Valsalva straining.
Left and right ventricular diastolic function during acute pericardial tamponade
Authors: Smiseth O. A. , Frais M. A. , Junemann M. , Kingma I. , Refsum H. , Smith E. R. , Lipton M. J. , Tyberg J. V.
Published: April 2008

Summary. The aim of the study was to determine the effect of acute pericardial tamponade on left (LV) and right ventricular (RV) intracavitary and transmural pressure‐volume (P–V) relations and to assess the effect of changing blood volume during tamponade on LV and RV volumes. The experiments were done in 11 acutely instrumented anaesthetized dogs in which LV and RV volumes were determined by computed tomography (CT) (n= 5) and LV and RV diameters by sonomicrometry (n= 6). Pressures were measured in the pericardium (balloon transducer), in the aorta and in the ventricles. Incremental pericardial infusion (up to 180 ml) caused a progressive left and upward shift of the LV and the RV intracavitary P–V relationship. This shift was entirely due to increased pericardial prressure (PP). The induction of tamponade caused no change in the LV and RV transmural P–V relationship. During tamponade with ventricular filling pressures above 10–15 mmHg, blood volume expansion caused only minimal increase in LV and RV volumes.

In conclusion, pericardial tamponade shifted the LV and the RV intracavitary diastolic P–V relation by increasing PP. However, there was no change in the transmural P–V relationship, indicating unchanged myocardial compliance. Volume loading caused only minimal increase in LV and RV volumes during tamponade.
Ventilatory response and arterial potassium concentration during incremental exercise in patients with chronic airways obstruction
Authors: Yoshida T. , Chida M. , Ichioka M. , Makiguchi K. , Tojo N. , Udo M.
Published: April 2008

Summary. The relationship of ventilation response (V̇E) to arterial potassium concentration (K+) during ramp incremental exercise was assessed in nine patients with chronic obstructive pulmonary disease (COPD), and in 10 healthy subjects. For COPD patients the maximum oxygen uptake (VOmax) was 19.6±3.8 ml kg‐1 min‐1 (± SD), and percentage of forced expired volume at 1 s (% FEV1) was 47.8 ± 10.4%. In healthy subjects, Vo2max was 44.4±7.0 ml kg‐1 min‐1 and FEV1, was 89.7 ± 7.4%. Breath‐by‐breath determinations for V̇E, oxygen uptake (V̇o2) and carbon dioxide output (V̇co2), as well as determinations for K+, partial pressure of oxygen (Po2), partial pressure of carbon dioxide (Pco2), pH and lactate in arterial blood were performed during a workout on an exercise bicycle at a ramp function work rate of 20 W min‐1, preceded by a 40 min warm‐up period. The major findings in the present study are: (1) that there is a linear relation between ventilation and arterial K+ concentration during ramp exercise in both healthy subjects and COPD patients; (2) that the slope of the V̇E‐K+ relationship is significantly lower in COPD patients (16.2 ± 7.31 min‐1 mM‐1) than in normal subjects (37.4 ± 6.91 min‐1 mM‐1, P<0.01); and, (3) that the slope of the V̇E‐K+ relationship is significantly related to the ability to ventilate during maximal exercise in both healthy subjects and COPD patients (P<0.05). It is thought that the significantly reduced slope of the V̇E‐K+ relationship in the COPD patients could be interpreted as a reduced sensitivity to the stimulus and/or as a mechanical impairment of the ventilation.
The effect of resistance training on blood pressure in normotensive women
Authors: Gilders R. M. , Malicky E. S. , Falkel J. E. , Staron R. S. , Dudley G. A.
Published: April 2008

Summary. The purpose of the present study was to determine whether conventional resistance training alters 24‐h ambulatory and manually determined casual blood pressure of normotensive women. Seven individuals (23 ± 2 years old) trainined 2 days week1 for 20 weeks emphasizing the hip and knee extensor muscle groups. Three sets to exhaustion of the knee extension, squat, knee flexion and leg press exercises were performed. The load for each exercise represented approximately 8045% of the one‐repetition maximum. Average values for 24‐h ambulatory blood pressure were not different (P>0·05) pre‐ and post‐training (systolic, 107 ± 4 vs. 109±1 mmHg; diastolic, 73±2 vs. 71±2 mmHg). Ambulatory values over 8‐h segments of the 24 h (day, evening, night) and casual resting determinations of blood pressure were also not affected. The lack of change in blood pressure cannot be explained by an insufficient training response. Knee extensor strength during dynamic or isokinetic actions increased (˜43%, P<0·05). In addition, biopsies from the vastus lateralis muscle showed an increase (P<0·05) in average muscle fibre cross‐sectional area of 32%. This hypertrophic response was further substantiated by an increase (P<0·05) in lean body mass (41·2±1·3 kg to 43·4±1·5 kg). These results indicate that resistance training, which increases muscular strength, muscle fibre area and lean body mass, does not alter ambulatory or casual blood pressure. Thus, the concern that conventional resistance training may chronically elevate blood pressure does not appear warranted, at least in normotensive women.
Validation of body composition by dual energy X‐ray absorptiometry (DEXA)
Authors: Haarbo J. , Gotfredsen A. , Hassager C. , Christiansen C.
Published: April 2008

Summary. The present study validates the use of dual energy X‐ray absorptiometry (DEXA) for measurement of body composition. The precision error was expressed as the SD (CV%) for fat mass, FAT%, lean tissue mass, and total body bone mineral: 1·1 kg (6·4%), 1·6% (5·7%), 1·4 kg (3·1%), and 0·03 kg (1·2%), respectively. The accuracy study in vitro used (1) mixtures of water and alcohol, (2) mixtures of ox muscle and lard, and (3) dried bones. In the clinically relevant range of values there were only small influences on DEXA measurements of variations in amount and composition of the soft tissue equivalents. The accuracy study in vivo compared the components of body composition measured recently by DEXA and earlier by dual photon absorptiometry, counting of naturally occurring total body 40K, and body density by underwater weighing in 25 healthy adult subjects. We found agreement between fat percentage (and lean body mass) by DEXA and the three established measurements modalities; mean differences were (‐5·3 to ‐0·4%) and (‐0·7 to 2·5 kg) for fat percentage and lean body mass, respectively. We conclude that DEXA provides a new method of measuring body composition with precision and accuracy errors, which are compatible with the application of DEXA in group research studies and probably also in clinical measurements of the single subject.
Metabolism in exercising arm vs. leg muscle
Authors: Ahlborg G. , Jensen‐Urstad M.
Published: April 2008

Summary. Arm and leg metabolism were compared by arterial and venous catheterization and blood flow measurements (by dye dilution techniques) in two groups of subjects performing 30‐min continuous arm or leg exercise of increasing intensity corresponding to approximately 30, 50 and 80% of max oxygen uptake for arm or leg exercise. The absolute work‐loads were 2·5‐3 times higher during leg compared to arm exercise. Heart rates were the same in both types of exercise. r‐Values were 0·97‐1·07 during arm exercise. Arterial noradrenaline and adrenaline levels became higher during leg compared to arm exercise (P< 0·05401). Arterial lactate concentration was 50% higher for arm exercise at the two lower intensities (P< 0·001) and the same at the highest intensity compared to leg exercise. Arm lactate release was three times higher (P< 0·01) or the same as leg lactate output at corresponding exercise intensities. Arm and leg glucose uptake during exercise were of the same magnitude at the lower intensities. In contrast to the leg substrate exchange, arm lactate output was higher than the simultaneous glucose uptake (P< 0·05–0·001), indicating a relatively higher rate of glycogen degradation. In conclusion, exercising arm compared to leg muscles working at the same relative intensities utilize more carbohydrate, mainly muscle glycogen resulting in higher lactate release by the exercising extremity. This cannot solely be explained on the basis of differences in the degree of training and occurs with lower catecholamine levels compared to leg exercise.
Correlation between computer‐assisted femoral arteriography and physiological tests in hypercholesterolaemic patients: a methodological study with special reference to clinical trials
Authors: Nilsson S. , Kaijser L. , Erikson U. , Johansson J. , Walldius G.
Published: April 2008

Summary. The validity of computer‐assisted femoral arteriography, for the study of regression/progression of atherosclerosis in follow‐up clinical trials, was investigated by comparison with routine physiological estimates of peripheral circulatory function. Thus, in 114 hypercholesterolaemic patients, the results of aorto‐femoral arteriography were compared with those of leg segmental blood pressure measurement, oscillometry, digital pulse plethysmography, and bicycle and treadmill exercise tests. In 107 patients, 18 with symptoms of peripheral vascular disease (PVD) and 89 asymptomatic, magnification arteriograms of a 20 cm segment of the right or left superficial femoral artery were obtained. These arteriograms were digitized and the following variables were calculated: arterial lumen volume (corrected for body size), per cent stenosis, and edge roughness. The correlation between arteriographic and physiological variables was investigated with a linear regression model, taking into account the possible interaction with sex, and presence or absence of symptoms of PVD. Lumen volume correlated significantly with all five physiological variables, and per cent stenosis correlated significantly with four of the physiological variables. For the roughness measure, however a significant correlation was found only with plethysmography.

By using logistic multiple regression analysis linear functions of physiological variables were constructed to detect ilio‐femoral arterial occlusion. The sensitivity specificity for detection of right‐sided, left‐sided, and bilateral occlusion was 0.83/0.98, 0.78/0.98, and 0.60/1.00 respectively (N = 108–111). Systolic blood pressure (ankle‐arm ratio) was the single variable most closely correlated to the likelihood of arterial occlusions.

It is concluded that arterial lumen volume and per cent stenosis, measured for the digitized femoral arteriogram, correlate well with physiological variables, which
Longitudinal systolic shortening of the left ventricle: an echocardiographic study in subjects with and without preserved global function
Authors: Alam M. , Höglund C. , Thorstrand C.
Published: April 2008

Summary The atrioventricular (AV) plane displacement was studied by echocardiography in 79 subjects (45 healthy subjects and 34 patients with acute myocardial infarction or chronic congestive heart failure). From apical 4‐ and 2‐chamber views the displacement of the AV plane towards the apex in systole was recorded at 4 sites in the left ventricle (LV) corresponding to the septal, anterior, lateral, and posterior walls and the mean value from the above 4 sites (AV‐mean) was calculated. In addition, in healthy subjects, the AV plane displacement at right ventricular free wall was also recorded. The AV‐mean correlated well with the echocardiographic ejection fraction determined by biplane area‐length method (r= 0.96, P<0–001). The correlation was also high when the percentage of the left ventricular shortening along the long axis was used (r= 0–97, P<0–001). The correlation between ejection fraction and AV‐mean was also good when separate analysis was made for the subjects with preserved ejection fraction (r= 0.86, P<0–001) and decreased ejection fraction (r= 0.82, P< 0.001). The right ventricle had a significantly higher AV plane displacement (P< 0.001) than the LV. The study also includes determination of the muscular excursions of the septal and posterior walls along the short axis of the left ventricle from the parasternal long axis view. The AV plane displacement of the respective walls was relatively greater (P<0.001) compared to concentric contractions. The septal and posterior wall excursions along the short axis correlated poorly with the AV plane displacement of the respective walls (r= 0.55, P<0.01 and r= 42, P<0.05).
Testing arterial baroreflex function in acutely unwell patients
Authors: Anderson I. D. , Little R. A.
Published: April 2008

Summary Cardiovascular function is deranged in acute illnesses but specific details of this pathophysiological phenomenon are poorly understood. With advances in intensive care it is now necessary to define these changes. Existing tests of cardiovascular reflex function are ill‐suited to the study of acutely unwell patients. The arterial baroreflex is the principal cardiovascular homeostatic reflex. We have modified the neck suction test of baroreflex function such that it can be performed in 30 min using portable equipment. The protocol was validated on control subjects. Testing of injured patients showed that this test and protocol could be used sequentially, beginning within 2 h of injury, to demonstrate acute changes in baroreflex function and to follow these changes through the disease process. Patient tolerance of the test was excellent. Subsequently, further modification developed an even shorter protocol whereby similar information could be obtained within 15 min. The cardiac response to deep respiration can be measured with minimal patient upset or compliance and is ideal for repetitive testing in critically ill patients. This is not a specific test of baroreflex function but responses to it show interesting parrallels with changes in baroreflex function which merit further study.
Does diffuse coronary atherosclerosis affect the relation between coronary stenoses and uptake of Thallium‐201 after exercise?
Authors: Ericsson C.‐G. , Erhardt L. , Hamsten A. , Mesko L. , Szamosi A. , Zetterquist S. , de Faire U.
Published: April 2008

Summary It has been proposed that diffuse coronary atherosclerosis influences the myocardial perfusion. We performed a study of 94 young men with previous myocardial infarction in order to find out whether the presence and extent of diffuse coronary atherosclerosis affected the relation between maximal stenosis and myocardial perfusion in areas remote from the infarction. The patients were examined by planar‐imaging thallium‐201 scintigraphy, following exercise, and coronary angiography within 6 months after myocardial infarction. The maximal distinct stenosis and diffuse coronary atherosclerosis, comprising both plaque size and extent, were semi‐quantitatively assessed. The correlation coefficients between maximal stenosis within the LAD, RCA, and LCX vascular territories and the corresponding initial uptake of thallium were 0.52 (P= 0.0001), 0.30 (P= 0.04), and 0.46 (P = 0.02), respectively. No change of the correlations was found, except for a slight increase of the r‐value from 0.30 to 0.37 in regions corresponding to RCA, after controlling for the diffuse atherosclerosis score in a multiple stepwise regression analysis. These findings indicate no impact of diffuse coronary atherosclerosis on regional myocardial perfusion in areas remote from the infarction.
Changes in autonomic cardiovascular control in mid‐pregnancy
Authors: Ekholm E. M. K. , Erkkola R. U. , Piha S. J. , Jalonen J. O. , Metsälä T. H. , Antila K. J.
Published: April 2008

Summary. Spectral analysis of heart rate variability was used to study autonomic nervous control in mid‐pregnancy. Fifty women (age 22–36 years) with singleton pregnancies (mean duration of gestation 27.7 weeks) and 39 non‐pregnant female controls (age 21–39 years) were studied using controlled breathing and orthostatic tests. During spontaneous breathing the overall heart rate variability was lower in pregnant subjects indicating a decreased parasympathetic tone at rest. The decreased parasympathetic tone probably counts for the increased heart rate in pregnancy. The parasympathetic efferent capacity of autonomic cardiac control was found to be similar in pregnant and non‐pregnant subjects, as no difference was seen during controlled breathing in periodic heart rate variability between the groups. Standing up caused a similar change in low frequency and mid‐frequency bands in both groups, but high frequency heart rate variability increased in pregnant subjects and decreased in the controls indicating an increased sympathetic tone at rest in mid‐pregnancy.
Exercise echocardiography: a methodological study comparing peak‐exercise and post‐exercise image information
Authors: Blomstrand P. , Engvall J. , Karlsson J. E. , Björkholm A. , Wallentin L. , Wranne B.
Published: April 2008

Summary. It is unclear whether echocardiography at peak bicycle exercise adds information to registrations obtained recumbent immediately after the test and what factors influence image quality. Therefore, exercise echocardiography was performed consecutively and prospectively in 66 men, unselected with regard to echocardiography, one month after an episode of unstable coronary artery disease.

Of 594 segments (9 × 66), 569 (96%) were adequately visualized recumbent at rest. The corresponding figures recumbent directly after exercise, seated before exercise, and seated at peak exercise were 544 (92%), 474 (80%), and 428 (72%), respectively. In the majority of our patients, acceptable images at peak exercise were obtained for the septal region, while for the anterior, lateral, and inferior segments the success rate varied from 50 to 70%. Recumbent after exercise, the success rate was acceptable for most segments, possibly with the exception of the apical and lateral segments.

Fifty‐five patients developed new wall motion abnormalities or worsening of wall motion in connection with exercise. Echocardiography at peak exercise provided more information than afterwards in patients with images of good quality. However, in patients with inferior image quality, the registrations obtained recumbent after the test revealed wall motion abnormalities which were not obtained seated at peak exercise. Patients with worse image quality had significantly higher respiratory rate and weight, and rated a higher degree of dyspnoea at peak exercise than those with good quality.

We conclude that in middle aged men with coronary artery disease, image acquisition at peak bicycle exercise and immediately after exercise are of complementary value.
Dependence of maximum performance time on work intensity in patients with a hereditary myopathy with succinate dehydrogenase deficiency
Authors: Linderholm H.
Published: April 2008

Summary. Patients with a hereditary mitochondrial myopathy with succinate dehydrogenase (SDH) deficiency and abnormal lactacidosis during physical exercise have a low work capacity when exercising for about 10–15 min. Their maximum voluntary muscular strength is fairly normal. The relationship between the time (t) and a constant workload (N) that a healthy subject can maximally sustain can be expressed as: log t =β+α log N. For normal subjects the constant a is approximately ‐5 and the constant β has a large interindividual variation. Of four myopathy patients a was determined from two or three maximum bicycle exercise tests of different duration (including ramp‐ and steady‐state tests using a new application of the method of adding submaximal loads to the final maximum workload). The value of a varied between ‐1.0 and ‐1.81 and p had low values, both significantly different from those of healthy subjects. The a values explain the divergent results that may be obtained with different types of exercise tests in some of these patients, i.e. a normal or moderately reduced capacity in exercise tests of short duration (for example a short Tornvall or a ramp type of test) and a very low exercise capacity in tests of longer duration (for example a steady state type of test with workloads chosen to allow at least two loads). The low absolute value of α may be related to the abnormally increased anaerobic metabolism of these patients during exercise, caused by the SDH deficiency.
Ambulatory strain‐gauge plethysmography and blood volume scintimetry for quantitative assessment of venous insufficiency
Authors: Struckmann J. R. , Vissing S. Fløistrup , Hjortsø E.
Published: April 2008

Summary In the present study, a strain‐gauge plethysmographic method (ASGP) is compared to an isotope plethysmographic method (ABVS), in order to evaluate how an externally recorded volume change corresponds to blood displacement within the leg during exercise. The coefficient of correlation for RT (venous return time) was 0.67 (P<0.001) and for EV (expelled volume) it was 0.61 (P<0.001).

The RT values were similar by the two methods both in healthy controls and in patients with Chronic Venous Insufficiency (CVI). The corresponding EV values showed the same pattern in controls and patients but the values differed substantially. By ASGP the value was approximately 2 ml per 100 ml tissue compared to 33 ml per 100 ml blood by the ABVS method.

Both methods could clearly distinguish normal controls from patients with chronic deep venous insufficiency, but ABVS could only make this distinction when the ankle area of measurement was applied.
Scintigraphic detection of gastro‐pulmonary aspiration in patients with respiratory disorders
Authors: Ruth M. , Carlsson S. , Månsson I. , Bengtsson U. , Sandberg N.
Published: April 2008

Summary. The scintigraphic detection of small nocturnal aspirations of radio‐labelled gastric contents is difficult in the presence of high remaining activity in the abdomen, causing a non‐uniform background activity. This problem was examined in phantom experiments and a technique for interpolative background correction was further developed. The accuracy of this technique was found to be influenced by the distance between the lung and the abdominal source of activity, and the minimum detectable ‘aspirated’ activity was determined as 0.1 MBq at a distance of 15 cm and 1 MBq at 5 cm.

The interpolative technique for background correction was evaluated on healthy volunteers and laryngectomized patients, examined 10 h after intragastric instillation of 200 MBq of 99Tcm‐pertechnetate. After background subtraction, their calculated pulmonary mean net count value was comparable to that registered before the radioactive tracer was administered. No localized accumulation of activity was found in any of these controls.

The technique was then applied clinically to 55 patients with chronic respiratory disorders and symptoms of gastroesophageal reflux. Aspiration was detected in 11 patients (20%). Five aspirators had asthma, two a chronic cough of unknown origin, two recurrent pulmonary infections, and one chronic bronchitis and chronic laryngitis respectively. Aspiration was detected among patients with and without demonstrated pathological gastroesophageal reflux.
Variability of the computerized single‐breath nitrogen washout test in healthy adults. Results from a field survey in a French rural area
Authors: Teculescu D. B. , Rebstock E. , Caillier I. , Pham Q. T. , Costantino E. , Bouchy O.
Published: April 2008

Summary. Within‐subject (difference between paired tests, or coefficient of variation [c. var.] of three consecutive measurements) and between‐subjects (standard deviation of the mean group) variability were assessed for the variables derived from the single‐breath nitrogen (SBN2) test in a group of healthy, asymptomatic subjects (n= 289) aged 20–64 years, from a rural area in North‐East France. Duplicate measurements in 99 subjects showed excellent agreement between the two attempts (correlation coefficients between 0.94 and 0.98) for static lung volumes and the alveolar N2 slope (PIII); closing volumes (CV) were more variable (r= 0.77 for absolute value, 0.79 for % VC) while closing capacities (CC) were in intermediate position (r= 0.86 for absolute value, and 0.88 for % TLC). The variability of three consecutive measures in 190 subjects showed the coefficients of variation to be low for static volumes and closing capacity (2.4–7.4%) and higher for PIII (15.1%) and CV or CV7VC (18.2 and 17.8%). The analysis of variance did not detect significant differences between the three sets of measurements, with the exception of a progressive increase of vital capacity (VC), and decrease in residual volume (RV) from test 1 to test 3, the total lung capacity being the same. Variability was uninfluenced by age or sex, except a higher c. var. for female VC as compared to males (2.8 vs. 2.2%, P= 0.02) and a higher variability of TLC (2.9 vs. 2.3%, P= 0.03) and VC (2.8 vs. 1.9%, P= 0.003) in people older than 40 years as opposed to those younger than 40 years.
Circadian variation of cardiac autonomic regulation during 24‐h bed rest
Authors: Hartikainen J. , Tarkiainen I. , Tahvanainen K. , Mäntysaari M. , Länsimies E. , Pyörälä K.
Published: April 2008

Summary. We examined the effect of circadian variation on cardiac autonomic regulation in 11 young and middle‐aged, healthy men during 24‐h bed rest. Cardiac parasympathetic regulation expressed significant circadian variation: sensitivity of baroreceptor reflex, standard deviation of R‐R intervals and the power of high frequency component of R‐R interval variability (HFP) increased during the evening (2000–2100 h), were highest during the night (0200–0300 h), and gradually decreased again towards afternoon (1400–1500 h). Cardiac sympathetic regulation, the power of medium frequency component of R‐R interval variability (MFP), did not show any significant circadian variation. The autonomic response to orthostatic stress changed after the 24‐h bed rest; the sympathetic dominance in response to assuming upright position was before bed rest principally attributable to increased sympathetic activity (MFP increase), whereas after bed rest this was due to withdrawal of parasympathetic activity (HFP decrease). We conclude that the effect of circadian variation must be taken into account, while assessing cardiac autonomic regulation in patients with acute cardiovascular disorders.
Non‐invasive estimates of aortic root pressures: external subclavian arterial pulse tracing calibrated by oscillometrically determined brachial arterial pressures,
Authors: Aakhus S. , Torp H. , Haugland T. , Hatle L.
Published: April 2008

Summary. This investigation assessed the ability of a non‐invasive method to reproduce aortic root pressure waveform and pressures. An external pulse tracing of the subclavian artery was obtained simultaneously with direct aortic root pressures during routine left heart catheterization in 26 patients (aged 39–74 years) with various cardiovascular disorders. Indirect brachial arterial peak‐systolic and nadir‐diastolic pressures were obtained with oscillometry. The direct and indirect peak‐systolic and nadir‐diastolic pressures, were separately used to calibrate the pulse tracing.

Adequate pulse tracing was obtained in 19 patients (73%). The waveforms agreed well with cross‐correlation coefficients for systole and diastole of 0.98. The difference between the pulse trace and the direct pressure curve, when the first was calibrated with the peak‐systolic and nadir‐diastolic pressures of the latter on average was less than 1 mmHg for systole and diastole. At end‐systole the mean difference was 5 mmHg.

Oscillometric brachial arterial peak‐systolic pressures were (meanSD) 37 mmHg below the corresponding direct measurements, while diastolic pressures were 84 mmHg above. The difference between the pulse trace and the direct pressure curve, when the pulse trace was calibrated with oscillometric pressures, was at end‐systole 66 mmHg and for mean arterial pressures 54 mmHg.

Thus, the external subclavian arterial pulse tracing provides a non‐invasive, clinically feasible access to the aortic root pressure waveform. With optimal calibration, good estimates of aortic root pressures throughout systole and diastole can be obtained, while end‐systolic pressure tends to be slightly overestimated.
Changes in skin blood flow in ischaemic limbs after vascular reconstruction measured by fluorescein flowmetry and laser Doppler flowmetry,
Authors: Proano E. , Perbeck L.
Published: April 2008

Summary. It is not known to what extent the skin blood flow increases after vascular reconstruction in ischaemic limbs. Thus, a study was undertaken to measure skin blood flow, using the two techniques laser Doppler flowmetry and fluorescein flowmetry, before and after vascular reconstruction. The skin temperature was measured also. The plantar circulation was assessed in 14 patients (9 non‐diabetics and 5 diabetics; mean age 65 years; range 47.80), with the patient in the supine position, 1–2 days before and 8.10 days after surgery. After vascular reconstruction the skin blood flow increased by 240% (P < 0.01) when measured by fluorescein flowmetry and by 148% (P < 0.01) when measured by laser Doppler flowmetry, and the skin temperature rose by 3.2 P < 0.01). In the contralateral non‐operated limb there was no significant change in skin blood flow as measured by the two methods. The results imply that after vascular reconstruction in ischaemic limbs the skin blood flow increases both in the superficial layer as determined by fluorescein flowmetry (which measures the blood flow down to 0.6 mm) and in deeper layers as determined by laser Doppler flowmetry (which measures flux down to 6 mm).
Cutaneous and subcutaneous blood flow rates in paraplegic humans investigated by 133Xenon wash‐out. Methodological considerations
Authors: Sørensen J. L. , Hauge E. N. , Wroblewski H. , Biering‐Sørensen F.
Published: April 2008

Summary. In a methodological study including 14 paraplegics and seven normal controls cutaneous and subcutaneous blood flow rates were investigated by 133Xenon wash‐out after atraumatic labelling. In paraplegics, areas suffering pressure sores were included. The method was found applicable for the authors' purposes. In seven paraplegics median (95% confidence limits) cutaneous blood flow was 5–2 (2–4–8–5) ml (100 g min)“1 and subcutaneous 4–3 (2–0–13–2) ml (100 g min)‐1. This did not differ from normal controls. In seven paraplegics with ischial pressure sores a trend for increased cutaneous blood‐flow rates from areas adjacent to sores was obvious (P= 0–06).

During 704 head‐up tilt, elimination‐rate constants were reduced by a factor of 0–54 (0–50–0–70). A proximal blockade or infiltration of the 133Xenon depots with lidocaine did not inhibit employment of the method. The proximal block did not alter the local blood flow rate, but infiltration increased it in both paraplegics and normal individuals. Intra‐ and interdepot coefficients of variation were about 11% and 40% respectively. Interindividual coefficients of variation varied between 25% and 46%.