The test-retest reliability of gas exchange kinetics in humans using a pseudo random binary sequence exercise test.

The purpose of this study was to compare the test-retest reliability of oxygen uptake (VO2) kinetics with carbon dioxide output (VCO2) kinetics using a pseudo random binary sequence (PRBS) exercise test. A reliable test of gas exchange kinetics would have the potential of being applied as a sports fitness test. Ten healthy male subjects agreed to participate in the study and all subjects completed two identical PRBS exercise tests (test 1 and test 2), separated by a 30 min period of inactivity. Three consecutive 300 s PRBS cycles were completed in each test with 20 s exercise intensity changes between 25 and 85 W using an electrically braked cycle ergometer. Fourier analysis was computed for frequencies 3.3, 6.7 and 10 mHz. Statistical analysis by two-way ANOVA with repeated measures did not reveal significant differences between test 1 and test 2 for either VO2 kinetics or VCO2 kinetics. Static gain of VO2 for test 1 [9.11 (SD 0.59) ml.min-1.W-1] and test 2 [9.23 (SD 0.64) ml.min-1.W-1] did not differ significantly between tests. The 95% limits of agreement for VCO2 kinetics displayed increased variability in comparison to VO2 kinetics at each frequency of amplitude ratio and phase shift. Systematic bias ranged between 0% and 4%, except at frequency 10 mHz of VCO2 kinetics phase shift which showed a 10% bias for slower VO2 kinetics in test 2. It is possible that the increased variability of VCO2 kinetics compared to VO2 kinetics might be attributable to a lower signal to noise ratio in VCO2 kinetics, variations in ventilation or the storage mechanisms of CO2. The lower variability of VO2 kinetics compared with VCO2 kinetics suggests that the PRBS test of VO2 kinetics has the greater potential for further development as an indicator of aerobic fitness.

Exercise testing in children: an alternative approach.

In recent years there has been a call for new methods of evaluating the cardiorespiratory responses of children to exercise that complement their everyday exercise patterns. One potential method would be to use a sub-maximal, intermittent, pseudo-random binary sequence (PRBS) exercise test protocol to measure oxygen uptake kinetics (VO2 kinetics). Ten children of mean (SD) age 10.8 (+/- 1.5) years completed a 20 - 50 W cycle ergometer protocol of 17-min duration. An estimate of alveolar oxygen uptake (VO2) was calculated on a breath-by-breath basis. The VO2 kinetic parameters were expressed in the frequency domain as amplitude ratio and phase delay using standard Fourier techniques. Analysis was restricted to the frequency range 2.2 to 8.9 mHz. The mean (SD) amplitude ratio responses decreased from 10.33 (+/- 0.73) to 7.42 (+/- 0.99) ml min(-1) W(-1) and the mean phase delay increased from -26.78 degrees (+/- 6.37 degrees) to -81.93 degrees (+/- 10.45 degrees) over the frequency range 2.2-8.9 mHz. Significant correlations (p < 0.05) were found between chronological age and amplitude ratio (r = 0.68 and 0.62), and chronological age and phase delay (r = -0.62 and -0.69) at the frequencies of 2.2 and 4.4 mHz, respectively. No significant correlations were found between VO2 kinetics and stature or VO2 kinetics and body mass. The observations demonstrated the use of the PRBS technique to measure VO2 kinetics in the frequency domain in children. This approach may be a useful addition to the tests that are used to quantify the oxygen uptake responses to exercise in children.

VO2 kinetics determined by PRBS techniques differentiate elite endurance runners from elite sprinters.

The aim of the study was to examine whether a measure of oxygen uptake (VO2) kinetics could differentiate between 12 elite male endurance (3000-10,000 m) runners and 12 elite male sprint (100-400 m) runners using a pseudo random binary sequence (PRBS) exercise protocol. All exercise tests were performed on an electrically braked cycle ergometer at a constant pedal frequency of 1 Hz. The PRBS exercise intensities alternated between 25 W and 85 W for three consecutive PRBS cycles of 300 s. VO2 was measured breath-by-breath and results were analysed by Fourier techniques in the frequency domain. Blood lactate concentrations taken pre and post testing were below 2 mM. Significantly greater amplitude components were observed in the endurance runners than sprinters at frequencies 6.7 mHz (6.71 +/- 1.09 and 5.47 +/- 0.95 ml x min(-1) x W(-1), respectively) P<0.05 and 10 mHz (4.97 +/- 0.98 and 3.56 +/- 0.69 ml x min(-1) x W(-1) respectively) P<0.01. Phase shift components were significantly shorter in the endurance runners compared to the sprinters at frequency 3.3 mHz (-35.45 +/- 4.31 and -41.26 +/- 5.82 degrees respectively) P<0.05. The results of this study show that VO2 kinetics are differentially faster in elite endurance runners than in elite sprinters. This supports the development of the PRBS technique as a test of sports performance.

Myocardial revascularization using the "no-touch" technique, with mild systemic hypothermia, in patients with a calcified ascending aorta.

Modifications in the standard technique for coronary artery bypass grafting are recommended in presence of a calcified ascending aorta, to avoid clamp injury or atheroembolism. Between January 1991 and August 1994, we used a "no-touch" technique in 18 patients undergoing myocardial revascularization, who had a heavily calcified and atherosclerotic ascending aorta. Their mean age was 76.1 years (range 63 to 82 years). Cardiopulmonary bypass with mild systemic hypothermia (32 degrees C) was employed in 16 patients; 2 other patients were operated upon without cardiopulmonary bypass. The "no-touch" technique avoids all types of clamps in the aorta. No cardioplegia was given, and no grafts were anastomosed to the aorta. Fifty-two distal anastomoses (mean: 2.9 per patient) were performed, using 37 pedicled arterial grafts (22 internal mammary and 15 gastroepiploic arteries), and 15 free grafts, which were anastomosed proximally to the internal mammary artery. There were no postoperative cerebrovascular accidents. Three patients died (16.7% overall mortality): 1 died of pneumonia, one patient with a large left ventricular aneurysm died in congestive heart failure, and one patient with associated aortic insufficiency died in low cardiac output. Our experience suggests that using pedicled arterial grafts for myocardial revascularization is safe and effective to avoid clamp injury or atheroembolism in patients with a calcified aorta. Deep hypothermia is not necessary when using the "no-touch" technique.

Cardiovascular effects of static and dynamic exercise.

The cardiovascular response to static exercise has often been quantified on the basis of a comparison between static handgrip and dynamic cycling exercise. It is then difficult to make precise comparisons because the physical units of work are not compatible. If the data from dynamic exercise can be used to predict the cardiovascular response to zero movement (static exercise) this would suggest that static exercise is not fundamentally different from dynamic exercise. Using leg extension exercise which lasted for 1 min, a set of weights was lifted repeatedly 50 times/min, through three different distances. On each occasion, the heart rate, systolic time intervals (STI) and systemic arterial blood pressure were monitored non-invasively. Regression analysis of heart rate (HR) or blood pressure (BP) against the distance moved by the weights was used to predict the heart rate or blood pressure that would be expected for static exercise. In addition the same responses were measured following 1 min of static exercise during which the weights were held up but not moved. Five subjects, trained in leg extension exercise, completed the four exercise sessions in a random order. A constant force was produced in each variant of the protocol and in the static exercise it amounted to 50% maximal voluntary contraction (MVC). The forces developed and the distance the weights were lifted were monitored. During this sustained static exercise at relatively low intensity the cardiovascular changes could be predicted from the responses induced by dynamic exercise. It is suggested that other factors are important in determining the cardiovascular response to exercise, not simply the mode.

Ruptured aortic valve cusp: a complication of the Heimlich maneuver.

A case of traumatic rupture of the aortic valve as a complication of the Heimlich maneuver is presented. Conformation was made by comparative echocardiographic studies available from three months before and immediately following the incident. The patient refused surgical intervention and died one month later with severe congestive heart failure despite vigorous medical therapy.

Frequency of occurrence, mode of development, and significance or rice bodies in rheumatoid joints.

The incidence of rice bodies (RB) in synovial effusions has been studied in 36 patients with rheumatoid arthritis (RA) and in 12 patients with seronegative inflammatory arthritis (7 cases of Still's disease, 3 of psoriatic arthritis, and 2 of ankylosing spondylitis). In the RA group 50 joints were aspirated before and after saline lavage with a specially designed wide-bore needle. RB were found in 72% overall of the joints studied in this group, 14% on initial simple aspiration and an additional 58% after lavage. In contrast no rice bodies were found in 31 aspirations with lavage by an identical technique in the 12 patients with seronegative synovitis. The RB in RA synovitis occurred both early and late in the course of the disease and were not related to the severity of clinical or radiological changes. However, removal of rice bodies was accompanied by clinical improvement and reduction of synovitis. Macroscopically RB varied in shape and size, some being so large as to preclude effective removal by needles of the gauge customarily employed for joint aspirations. Microscopically the majority of RB were composed of coarsely reticular material reacting immunologically with antifibrinogen and antifibronectin and containing mononuclear cells. Some showed vacuolation suggestive of fibrinolysis, but many showed organisation like that seen in established connective tissues, with the formation of mature collagen, reticulin, and elastin. These findings are discussed in relation to the origin, development, and significance of rice bodies in rheumatoid synovitis.

Intermittent left bundle branch block in the athletic heart syndrome.

A 30-year-old man with typical findings of the athletic heart syndrome is presented because of the unique feature of intermittent left bundle branch block. Observations during right atrial pacing and exercise support the concept of autonomic control of intraventricular conduction, both adrenergic and cholinergic.

Idiopathic ventricular tachycardia. An intracardiac electrical, hemodynamic and angiographic assessment of six patients.

Six patients with idiopathic paroxysmal ventricular tachycardia were investigated by external electrocardiography, intracardiac electrography and pacing, exercise testing, cardiac catheterization and coronary angiography. All had normal hemodynamics and coronary arteries. His bundle electrography proved ventricular origin in five; one had no paroxysmal ventricular tachycardia during His bundle electrography. Treatment with diphenylhydantoin, 4.2 to 8.0 mg/kg/day, and propranolol, 0.8 to 2.7 mg/kg/day, appeared effective, well tolerated therapy in three, and procainamide and propranolol in one requiring medical treatment. Abstinence from tobacco and coffee abolished paroxysmal ventricular tachycardia in one of two who required no medication. The other has no recurrence of paroxysmal ventricular tachycardia since study.