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Biomedical subjects

W MacNee

Publications and source records attributed to W MacNee.

At least 145 records · Page 8Linked to original sources
PubMed1990

Assessment of the right ventricle by magnetic resonance imaging in chronic obstructive lung disease.

Right ventricular wall and chamber volume were measured by magnetic resonance imaging in 16 patients with stable chronic obstructive lung disease who subsequently underwent measurement of pulmonary haemodynamics by right heart catheterisation. The patients had a forced expiratory volume in one second of 0.7 (SD 0.3) litres, a forced vital capacity of 2.4 (1.0) l, an arterial oxygen tension (PaO2) of 6.5 (1.3) kPa, an arterial carbon dioxide tension (PaCO2) of 6.5 (1.0) kPa, and a mean pulmonary arterial pressure 30 (10) mm Hg. The mean right ventricular free wall volume was 57.1 (22.6) cm3, compared with a mean value of 115.0 (44.3) cm3 for the left ventricle and interventricular septal volume. The right ventricular chamber volume at end systole was 44.8 (23.4) cm3, whereas the left ventricular end systolic chamber volume was 51.1 (35.1) cm3. The right ventricular free wall volume correlated with the right ventricular chamber volume (r = 0.71), systolic (r = 0.74) and mean (r = 0.72) pulmonary arterial pressure, pulmonary vascular resistance (r = 0.67), and PaCO2 (r = 0.56). There was no significant correlation between the right ventricular free wall volume and PaO2 or the right ventricular ejection fraction, measured by radionuclide ventriculography. Assessment of the right ventricle by magnetic resonance imaging may help to better define patients with cor pulmonable and assess the long term effects of treatment in such patients.

Adult↗
PubMed1989

The effect of cigarette smoking on neutrophil kinetics in human lungs.

Neutrophils may play a part in the pathogenesis of the centrilobular emphysema associated with cigarette smoking. The capillary bed of the lungs concentrates neutrophils approximately 100-fold with respect to erythrocytes, producing a large pool of marginated cells. We examined the effect of cigarette smoking on the kinetics of this pool of cells, using 99mTc-labeled erythrocytes to measure regional blood velocity and 111In-labeled neutrophils to measure the removal of neutrophils during the first passage through the pulmonary circulation, their subsequent washout from the lungs, and the effect of local blood velocity on the number of neutrophils retained in each lung region. We observed no difference in these measurements between subjects who had never smoked (n = 6) and smokers who did not smoke during the study (n = 12). However, subjects who did smoke during the study (n = 12) had a significantly slower rate of washout of radiolabeled neutrophils from the lung (0.08 +/- 0.04 of the total per minute, as compared with 0.13 +/- 0.06 in smokers who did not smoke during the experiment and 0.14 +/- 0.08 in non-smokers) (P = 0.02). We also observed an increase in the regional retention of labeled neutrophils with respect to blood velocity in 5 of the 12 subjects who smoked during the study, but in none of the other subjects. We conclude that the presence of cigarette smoke in the lungs of some subjects increases the local concentration of neutrophils, and suggest that the lesions that characterize emphysema may be a result of the destruction of lung tissue by neutrophils that remain within pulmonary microvessels.

Adult↗
PubMed1989

Regional pulmonary transit times in humans.

We measured the frequency distribution of erythrocyte (RBC) transit times in resected lobes of lungs in eight human subjects undergoing thoracotomy for peripheral lung tumors. RBC transit times were measured by the injection of radiolabeled blood flow and volume markers, which were counted in samples from the resected lung. In five of these subjects, the measurements from the resected lung were compared with preoperative measurements of the transit times of radiolabeled RBCs with a gamma camera-computer system. Time-activity curves from the cardiac chambers and the lung or its regions were obtained from which transit times were calculated by the centroid and deconvolution techniques. The reproducibility of transit times measured by this technique was assessed in another eight normal subjects, after sequential bolus injections of radiolabeled cells. The mean transit time of the upper lung region was longer (5.1 +/- 0.5 s) than that of the lower (4.1 +/- 0.6 s, P less than 0.05) in the preoperative study. Similarly, the mean transit time of the upper lung slice was longer (5.5 +/- 0.3 s) than that of the lower slice (3.8 +/- 0.3 s, P less than 0.05) in the resected lung specimens. We conclude that there was good agreement between these techniques and that there are long transit times in the upper regions of human lungs.

Blood Circulation Time↗
PubMed1989

The effect of six months of daily treatment with the beta-2 agonist oral pirbuterol on pulmonary hemodynamics in patients with chronic hypoxic cor pulmonale receiving long-term oxygen therapy.

We studied the acute and long-term effect of the oral beta-2 agonist pirbuterol on pulmonary hemodynamics and right and left ventricular ejection fractions in 11 patients with stable hypoxic chronic bronchitis and emphysema who were maintained on long-term oxygen therapy. We have used a double-blind study with random allocation of patients to receive either pirbuterol or an identical-appearing placebo. Six patients received 15 mg pirbuterol thrice daily, and five patients received a similar placebo thrice daily, over a 6-month period. The first 15-mg dose of pirbuterol by mouth at the beginning of the study raised the heart rate from 84 +/- 13 to 100 +/- 16 beats/min (mean +/- SD) (p less than 0.01), and cardiac output from 5.2 +/- 0.9 to 6.4 +/- 0.8 L/min (p less than 0.01) and right ventricular ejection fraction (RVEF) from 0.28 +/- 0.10 to 0.33 +/- 0.12 (p less than 0.01) within 120 min after receiving the drug, but without significant change in the mean pulmonary arterial pressure. None of these variables changed significantly after an acute dose of placebo in another four patients. Repeated measurements after 6 months of chronic oral therapy with either pirbuterol or placebo showed that 16 h after the last 15-mg oral dose of pirbuterol or placebo, the heart rate, mean pulmonary arterial pressure, cardiac output, total pulmonary vascular resistance, and RVEF were all not significantly different from the values 6 months previously, before receiving either pirbuterol or the placebo.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Agonists↗
PubMed1988

Does right ventricular function predict survival in patients with chronic obstructive lung disease?

Non-invasive measurements of the right ventricular ejection fraction by radionuclide ventriculography were made in 115 patients with chronic obstructive lung disease. Survival was assessed over a mean period of 918 days. The right ventricular ejection fraction was reasonably normal in most patients (mean 0.42, range 0.10-0.66) but was lower in those with peripheral oedema, indicating cor pulmonale (mean 0.31 (SD 0.07); p less than 0.0001). Right ventricular ejection fraction was related to survival, but the relationship was weak (p = 0.03) by comparison with the association between the arterial oxygen and carbon dioxide tensions and survival (both p less than 0.0001). It is concluded that, although right ventricular function is predictive of survival in patients with chronic obstructive lung disease, it is probably a reflection of severity of disease and does not directly affect the prognosis.

Adult↗
PubMed1988

Right ventricular function in cor pulmonale.

Traditionally the right ventricle has been thought to function poorly in the presence of an increased afterload. Indeed, the presence of pulmonary arterial hypertension, or cor pulmonale, has been associated with a poor prognosis in patients with hypoxic chronic obstructive pulmonary disease (COPD). Recent data suggest that right ventricular contractility as measured by the right ventricular end-systolic pressure/volume relationship is relatively normal in patients with COPD, despite the presence of pulmonary arterial hypertension if the patients are studied when clinically stable, but reduced when the patients present with oedema. Continuous oxygen therapy is the only treatment which has been shown to improve survival in patients with COPD and cor pulmonale. However, the effects of oxygen therapy may not be directly related to an improvement in cardiac function.

Heart Failure↗
PubMed1988

CT measurements of lung density in life can quantitate distal airspace enlargement--an essential defining feature of human emphysema.

We used a computerized microscopic image analysis system to directly measure the surface area of distal air spaces in methacrylate-embedded blocks randomly selected from inflation-fixed lobes that were resected from 45 patients as treatment of their peripheral lung tumors. In 28 of these patients, a preoperative computer tomography (CT) scan, at 6 and 10 cm below the sternal notch, was used to generate frequency histograms of CT numbers (measured as EMI units), a measure of lung density, in pixels from the lung or lobe that was subsequently resected. A similar CT number histogram was also derived from the lateral two fifths of the area of lobe/lung that was to be resected. The EMI unit that defined the lowest fifth percentile of this latter histogram correlated (n = 28, r = -0.77, p less than 0.001) with the mean value of the surface area of the walls of distal airspaces per unit lung volume (AWUV) in the five 1 mm x 1 mm microscopic fields with the lowest AWUV values, out of the 20 to 35 such fields examined in each patient. In the 34 of the 45 patients in whom we also measured volume-corrected diffusing capacity (DLCO/VA), this also correlated (n = 34, r = 0.84, p less than 0.001) with this value of AWUV, which measures the surface area of airspaces distal to the terminal bronchioles--reflecting an increase in airspace size, a defining characteristic of emphysema. However, a low DLCO/VA is nonspecific, whereas an abnormally low regional lung density is more likely to be specific for emphysema. In addition, highlighting those pixels of the CT display with low CT numbers (i.e., EMI units -500 [air] to -450, where zero = water) can locate areas of macroscopic emphysema, as shown by subsequent pathologic examination. Thus the quantitative CT scan can diagnose, quantitate, and locate mild to moderate emphysema, in humans, in life, noninvasively.

Aged↗
PubMed1988

The effects of controlled oxygen therapy on ventricular function in patients with stable and decompensated cor pulmonale.

We made simultaneous measurements of pulmonary hemodynamics, cardiac output, and right ventricular ejection fraction (RVEF) to assess the right ventricular function in 14 patients with pulmonary arterial hypertension as a result of chronic obstructive pulmonary disease (COPD). From these measurements, the right ventricular end-systolic pressure/volume relationship could be calculated and used to assess right ventricular contractility. Eight of the patients were clinically stable, without edema, and 6 presented acutely with gross edema, indicating decompensated cor pulmonale. Measurements were made at rest, while breathing air and oxygen. Although mean pulmonary arterial pressure (Ppa) was similar in those with (Ppa = 33 +/- 6 mm Hg) and without edema (Ppa = 30 +/- 8 mm Hg, p greater than 0.05), RVEF was lower in edematous (RVEF = 0.23 +/- 0.11) compared with non-edematous patients (RVEF = 0.47 +/- 0.04, p less than 0.01). Cardiac output was normal in both groups. The mean right ventricular end-systolic pressure/volume ratio (P/V) was lower in those patients with edema (P/V = 0.41 +/- 0.27), as compared with those without edema (P/V = 1.69 +/- 0.35, p less than 0.05), as a result of an increase in right ventricular end-systolic volume index. Similarly, left ventricular end-systolic volumes were higher in edematous than in non-edematous patients. Breathing 1 to 3 L/min of oxygen for 30 min decreased total pulmonary vascular resistance (p less than 0.05) in those patients without edema, but not in patients with edema. Oxygen did not change RVEF, left ventricular ejection fraction (LVEF), or the ventricular end-systolic P/V relationships.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1988

Pulmonary hypertension and right ventricular function in patients with COPD.

In 100 patients with chronic obstructive pulmonary disease (COPD), we found no significant correlation between simultaneous measurements of right ventricular ejection fraction, using radionuclide ventriculography, and pulmonary arterial pressure. There was, however, a weak but significant correlation between right ventricular ejection fraction and the pulmonary vascular resistance (r = 0.40, p less than 0.005). In 52 of these patients, 37 with pulmonary hypertension, right ventricular end-systolic volume index was 53 +/- 21 ml.m-2 and end-diastolic volume index was 86 +/- 27 ml.m-2, compared with a calculated mean of 33 ml.m-2 and 79 ml.m-2, respectively, for normal subjects. In 24 of these patients where the measurements were made at rest and on exercise, the mean right ventricular end-systolic volume increased from 66 +/- 20 ml.m-2 to 87 +/- 32 ml.m-2, with an increase in right ventricular systolic pressure from 28 +/- 9 mm Hg to 55 +/- 15 mm Hg. Analysis of the slope of the right ventricular end-systolic pressure volume relationship at rest and on exercise suggested relatively normal right ventricular contractility in the majority of patients. Thus, in these patients with stable COPD, despite the presence of pulmonary hypertension, right ventricular contractility remained relatively normal.

Blood Pressure↗
PubMed1986

A comparison of the effects of almitrine or oxygen breathing on pulmonary arterial pressure and right ventricular ejection fraction in hypoxic chronic bronchitis and emphysema.

Almitrine bismesylate is a new, orally administered, respiratory stimulant that improves arterial blood gas tensions in patients with chronic bronchitis and emphysema, and it may have an effect on the pulmonary circulation and on right ventricular performance. We have, therefore, compared the effects of Almitrine with those of oxygen (given as 3 L/min by nasal prongs) on arterial blood gas tensions, mean pulmonary arterial pressure (Ppa), and right ventricular ejection fraction (RVEF) measured both at rest and during exercise in patients with chronic hypoxemia caused by chronic bronchitis and emphysema. Arterial oxygen tension improved significantly both at rest and during exercise after either 100 mg Almitrine by mouth or when breathing oxygen, both at rest and during exercise. Almitrine increased the mean Ppa at rest from 22 +/- 4 to 35 +/- 5 mmHg (p less than 0.001), and mean Ppa rose further during exercise from 38 +/- 5 mmHg before Almitrine to 49 +/- 7 mmHg (p less than 0.001) after Almitrine. In contrast, oxygen breathing did not change Ppa when at rest but reduced the amount of rise in Ppa during exercise. The change in Ppa after Almitrine correlated with the plasma Almitrine concentration (r = 0.69, p less than 0.05) and was associated with a fall in RVEF at rest from 0.38 +/- 0.03 to 0.32 +/- 0.02 (p less than 0.001). In 5 of the patients who received 50 mg of Almitrine by mouth twice daily for 3 months, the Ppa both at rest and during exercise remained significantly higher than in the control study before receiving Almitrine, but RVEF was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Disodium cromoglycate fails to prevent the rise in pulmonary artery pressure in hypoxic chronic bronchitis and emphysema.

Animal studies have suggested that stabilising mast cells may reduce the rise in pulmonary artery pressure which is produced by hypoxia. In six patients with stable hypoxic chronic bronchitis and emphysema, we have compared the pulmonary artery pressure at rest and on exercise before and after inhaling disodium cromoglycate (DSCG). The increase in heart rate was the same after each period of exercise (17 beats/min increase on placebo; 16 beats/min on DSCG), as was fall in arterial oxygen saturation (6% on placebo; 6% on DSCG). The subsequent rise in pulmonary artery pressure (PAP) during exercise was also not significantly different between placebo and DSCG. We conclude that 80 mg of aerosolised DSCG does not modify the pulmonary artery pressure in patients with chronic bronchitis and emphysema either at rest or during exercise.

Aged↗
PubMed1985

Mechanism of transient nocturnal hypoxemia in hypoxic chronic bronchitis and emphysema.

In five patients with hypoxic chronic bronchitis and emphysema we measured ear O2 saturation (SaO2), chest movement, oronasal airflow, arterial and mixed venous gas tensions, and cardiac output during nine hypoxemic episodes (HE; SaO2 falls greater than 10%) in rapid-eye-movement (REM) sleep and during preceding periods of stable oxygenation in non-REM sleep. All nine HE occurred with recurrent short episodes of reduced chest movement, none with sleep apnea. The arterial PO2 (PaO2) fell by 6.0 +/- 1.9 (SD) Torr during the HE (P less than 0.01), but mean arterial PCO2 (PaCO2) rose by only 1.4 +/- 2.4 Torr (P greater than 0.4). The arteriovenous O2 content difference fell by 0.64 +/- 0.43 ml/100 ml of blood during the HE (P less than 0.05), but there was no significant change in cardiac output. Changes observed in PaO2 and PaCO2 during HE were similar to those in four normal subjects during 90 s of voluntary hypoventilation, when PaO2 fell by 12.3 +/- 5.6 Torr (P less than 0.05), but mean PaCO2 rose by only 2.8 +/- 2.1 Torr (P greater than 0.4). We suggest that the transient hypoxemia which occurs during REM sleep in patients with chronic bronchitis and emphysema could be explained by hypoventilation during REM sleep but that the importance of changes in distribution of ventilation-perfusion ratios cannot be assessed by presently available techniques.

Adult↗
PubMed1985

Right ventricular performance during exercise in chronic obstructive pulmonary disease. The effects of oxygen.

Radionuclide ventriculography allows non-invasive assessment of right ventricular performance. This study has confirmed that there is a modest reduction in right ventricular ejection fraction (RVEF) in patients with chronic obstructive pulmonary disease (COPD), as compared to normal subjects. However, occult right ventricular dysfunction also becomes apparent in these patients during exercise. The change in RVEF during exercise is related to the corresponding fall in arterial oxygen saturation in patients with COPD. Oxygen improves the response of the right ventricle to exercise, although the mechanism remains unclear. Long-term oxygen therapy, in patients with respiratory failure, does not appear to have any significant effect on RVEF.

Adult↗