Jacob Loke

Assessment of cardiac performance with quantitative radionuclide angiocardiography: Right ventricular ejection fraction with reference to findings in chronic obstructive pulmonary disease

A reproducible noninvasive technique for measuring righ ventricular ejection fraction was developed using first pass quantitative radionuclide angiocardiography. Studies were obtained in the anterior position with a computerized multicrystal scintillation camera with high count rate capabilities. Right ventricular ejection fraction was calculated on a beat to beat basis from the high frequency components of the background-corrected right ventricular time-activity curve. In 50 normal adults, right ventricular ejection fraction averaged 55 percent (range of 45 to 65 percent). This radionuclide measure of right ventricular function was reproducible, with minimal inter- and intraobserver variability, and was sensitive to changes in inotropic state induced with isoproterenol. In 36 patients with chronic obstructive pulmonary disease, right ventricular ejection fraction ranged from 19 to 71 percent. All 10 patients with corpulmonale, as well as 9 additional patients, had an abnormal right ventricular ejection fraction. Arterial oxygen tension and forced expiratory volume were depressed significantly more in patients with abnormal right ventricular ejection fraction than in subjects with normal right ventricular function. There was no relation between abnormalities in right and left ventricular ejection fraction.

Right and Left Ventricular Exercise Performance in Chronic Obstructive Pulmonary Disease: Radionuclide Assessment

Right and left ventricular pump performance was assessed at rest and during upright bicycle exercise in 30 patients with chronic obstructive pulmonary disease and in 25 normal control subjects. Right ventricular and left ventricular ejection fractions were ascertained noninvasively using first-pass quantitative radionuclide angiocardiography. The normal ventricular response to exercise was at least a 5% absolute increase in the ejection fraction of either ventricle. In patients the predominant cardiac abnormality involved performance of the right ventricle. Right ventricular ejection fraction was abnormal at rest in eight patients. Twenty-three patients demonstrated an abnormal right ventricular response to submaximal exercise. Airway obstruction and arterial hypoxemia were significantly more severe in patients with abnormal right ventricular exercise reserve than in those with normal reserve. Abnormal left ventricular performance was infrequent either at rest (four patients) or during exercise (six patients). Thus, this radionuclide technique allows noninvasive assessment of biventricular exercise reserve in chronic obstructive pulmonary disease.

Effects of aminophylline upon right and left ventricular performance in chronic obstructive pulmonary disease: Noninvasive assessment by radionuclide angiocardiography

Abstract Although aminophylline is a widely used bronchodilator in chronic obstructive pulmonary disease (COPD), its effects upon cardiac performance have not been fully established. The effect of aminophylline upon right ventricular and left ventricular ejection fraction and the left ventricular ejection rate was evaluated by first-pass quantitative radionuclide angiocardiography in 15 patients with COPD, including four with cor pulmonale, and in five control subjects without cardiopulmonary disease. Aminophylline infusion (9 mg/kg) significantly increased the right ventricular ejection fraction (45 to 52 per cent), left ventricular ejection fraction (60 to 67 per cent) and left ventricular ejection rate (3.4 to 4.1 sec −1 ) in patients with COPD (all parameters, p −1 ) (p 1 ) and forced vital capacity (FVC) increased significantly in patients with COPD but not in control subjects. Arterial carbon dioxide tension decreased significantly in both groups (p These data indicate that aminophylline acutely enhances biventricular performance in COPD. Since comparable cardiovascular changes are induced in normal subjects in whom ventilatory function was not altered, the beneficial effects of aminophylline upon global ventricular performance appear to be independent of the degree of pulmonary compromise.

Improvement in cardiac performance by oral long-acting theophylline in chronic obstructive pulmonary disease

Although oral theophylline is a widely used bronchodilator in chronic obstructive pulmonary disease (COPD), its effects upon cardiac performance have not been fully established. The effect of slow release oral theophylline upon right ventricular and left ventricular ejection fraction was evaluated using first-pass quantitative radionuclide angiocardiography in 15 patients with COPD. After 72 hours of therapy, oral theophylline significantly increased right ventricular ejection fraction (42% to 48%, p less than 0.005). In 7 of 10 patients with depressed baseline right ventricular performance, including two with cor pulmonale, right ventricular ejection fraction normalized (greater than or equal to 45%). After long-term therapy, an average of 16 weeks, right ventricular fraction also increased (43% to 48%, p less than 0.005). Left ventricular ejection fraction improved significantly from 64% to 68% (p less than 0.05) at 72 hours and from 61% to 65% (p less than 0.025) after long-term therapy. These data indicate that oral theophylline produces a sustained modest enhancement of resting biventricular performance in COPD.

Normal arterial oxygen saturation with the ear oximeter in patients with leukemia and leukocytosis

Leukemic patients with severe leukocytosis experience a spurious lowering of the arterial oxygen tension if the arterial blood samples are not immediately analyzed. Arterial oxygen tensions were measured in three patients with acute leukemia; actual oxygen saturation was simultaneously measured with an ear oximeter. Blood gases demonstrated significant arterial hypoxemia even with immediate blood gas analysis in all patients. The ear oximeter in two patients revealed a relatively normal oxygen saturation while there was a simultaneous decrease in the calculated oxygen saturation. With reduction of the leukocyte count following chemotherapy in one patient, the calculated arterial oxygen saturation and the ear oximetry reading approximated one another. The ear oximeter is of value in the assessment of the true oxygenation status of patients who have leukemia and severe leukocytosis.

Oral Terbutaline Augments Cardiac Performance in Chronic Obstructive Pulmonary Disease

In previous research, we have demonstrated that parenterally administered terbutaline can augment resting cardiac function in patients with chronic obstructive pulmonary disease (COPD). Because the oral form of terbutaline is more widely utilized, a double-blind, randomized, crossover, placebo-controlled trial of the cardiopulmonary effects of oral terbutaline was conducted in ten patients with COPD. Right and left ventricular ejection fractions (RVEF and LVEF) were determined by first pass radionuclide angiography. There were no differences in spirometry and hemodynamic measurements between treatment and placebo days. Following 5 mg of oral terbutaline, there was a small but statistically significant increase in forced expiratory volume in 1 second and in heart rate, but no significant change in forced vital capacity or blood pressure. LVEF improved significantly with terbutaline both at rest (62% +/- 6% vs. 67% +/- 9%, mean +/- SD) and during submaximal steady state exercise (61% +/- 5% vs. 67% +/- 10%). RVEF improved significantly at rest (64% +/- 6% vs. 69% +/- 5%), but not during submaximal steady state exercise (65% +/- 6% vs. 68% +/- 7%). Thus, oral terbutaline produces significant improvement in biventricular systolic pump performance at rest, and increases left ventricular ejection fraction during submaximal exercise in patients with moderate to severe COPD.

Exercise performance in marathon runners with airway obstruction

While evaluating lung function prior to four long-distance races (20-100 km), we found that nine of 127 marathon runners (7.1%) had airway obstruction (mean FEV1/FVC, 63.3%). Since obstruction to air flow may limit exercise performance, we compared selected cardiorespiratory parameters during exercise on a cycle ergometer in runners with airway obstruction (RAO), nine non-athletic control subjects (CON), and nine marathon runners with normal lung function (RNL). As the chemical drive to breath affects exercise hyperpnea, the ventilatory responses to hypercapnia and hypoxia were measured. All RAO were males with a mean age of 35.6 yr (range of 20-44 yr). Eight of nine RAO had a significant increase in flow rates after inhalation of isoproterenol. In the RAO and CON groups exercise ventilation was similar when oxygen consumption (VO2) was less than 2.0 l/min; as VO2 exceeded this level, significantly greater ventilation was required by the RAO. Carbon dioxide production was highest in RAO, intermediate in CON, and lowest in RNL. There was no significant difference in the mean ventilatory responses among CON, RAO, and RNL. Despite pulmonary dysfunction, the RAO achieved moderate-to-high levels of exercise performance.

Site of airway obstruction in asymptomatic asthmatic children

The site of airway obstruction in asthmatics may be in the central or peripheral airways. Recent studies with air and 80% helium/20% oxygen maximal expiratory flow-volume curves have suggested that this obstruction was predominantly in the central airways unless there were complicating clinical factors such as chronic bronchitis, recurrent respiratory infection or smoking. Others have indicated that peripheral airway obstruction is present in some asymptomatic asthmatics. Using air and 80% helium-20% oxygen maximal expiratory flow-volume curves and measurements of pulmonary mechanics, we studied the site of airway obstruction in asthmatic children without the above clinical factors and found it to be in the central or peripheral airways or both.

Carboxyhemoglobin levels in fire fighters

The occupational effect of carbon monoxide on blood carboxyhemoglobin levels (COHb) from smoke inhalation was studied in 51 fire fighters. Nonsmoking fire fighters had a baseline mean blood COHb saturation higher (P<.005) than non-smoking controls, while there was no difference in the blood COHb between smoking fire fighters and smoking control subjects. The blood COHb was repeated in 16 fire fighters after three building fires and there was a significant increase (P<.001) in the mean blood COHb level over the baseline values. Fire fighters should avoid cigarette smoking after a fire to prevent further increases in blood COHb levels. The use of the self-contained air breathing apparatus is protective against undue exposure to carbon monoxide during fire fighting.

The Physiology of Marathon Running.

In brief: The marathon is one of the greatest tests of human endurance. This review article describes the physiological demands and responses of the respiratory, cardiovascular, and muscular systems to marathon running, focusing on the chain of oxygen transport needed to fulfill the aerobic requirements of marathon running. During the race, runners use about 75% of VO2 max. Increased levels of ventilation (> 80 liters· min(-1)) have been observed during the marathon. This can lead to decrements in forced vital capacity and respiratory muscle fatigue. Prolonged muscle activity during the run can cause muscle injury such as inflammation and necrosis of muscle fibers. Techniques for augmenting performance include endurance and interval training, diet manipulation, and racing strategy.