Cardiovascular performance in chronic obstructive pulmonary diseases

Evaluation of Pulmonary Hypertension in Chronic Obstructive Pulmonary Disease

Background: Pulmonary hypertension (PH) is frequently underdiagnosed and under-evaluated in chronic obstructive pulmonary diseases (COPD) patients. As PH is linked to a high rate of mortality from disease-related complications like cor pulmonale, it is critical to have a unified approach to diagnosing and treating it with the aim of improving the patient's quality of life and prognosis in terms of therapeutic considerations. Early identification of this comorbidity in patients with COPD can lead to early initiation of treatment and better prognostic implications. This study was undertaken with the aim of estimating the prevalence of PH in COPD as well as assessing any statistically significant associations between the severity of PH and the severity of COPD.

Methods: This was an observational study undertaken at the Department of Respiratory Medicine, Acharya Vinoba Bhave Rural Hospital (AVBRH) in Wardha, Maharastra, India, from August 2019 to September 2021. A total of 100 patients diagnosed with COPD on the basis of spirometry were evaluated with two-dimensional (2D) echocardiography to screen for echocardiographic signs and evidence of PH and severity staging of PH if present.

Results: In our study, out of 100 diagnosed cases of COPD, the prevalence of PH was found to be 40% (40 patients) and amongst these, mild, moderate, and severe PH was seen in 26 patients (26%), nine patients (9%), and five patients (5%), respectively. The frequency of PH in moderate COPD was 25% and in severe COPD was 51.5%.

Conclusions: PH was found in almost half the COPD patients in the study. Also, the degree and frequency of PH increased with the increase in COPD severity and this was found to be statistically significant.

Enhanced systolic function of the right ventricle during respiratory distress syndrome in newborn lambs

Respiratory distress syndrome (RDS) causes pulmonary hypertension. It is often suggested that this increased afterload for the right ventricle (RV) might lead to cardiac dysfunction. To examine this, we studied biventricular function in an experimental model. RDS was induced by lung lavages in seven newborn lambs. Five additional lambs served as controls. Cardiac function was quantified by indexes derived from end-systolic pressure-volume relations obtained by pressure-conductance catheters. After lung lavages, a twofold increase of mean pulmonary arterial pressure (from 15 to 34 mmHg) was obtained and lasted for the full 4-h study period. Stroke volume was maintained (5.2 +/- 0.6 ml at baseline and 6.1 +/- 1.4 ml at 4 h of RDS), while RV end-diastolic volume showed only a slight increase (from 6.5 +/- 2.3 ml at baseline to 7.7 +/- 1.3 ml at 4 h RDS). RV systolic function improved significantly, as indicated by a leftward shift and increased slope of the end-systolic pressure-volume relation. Left ventricular systolic function showed no changes. In control animals, pulmonary arterial pressure did not increase and right and left ventricular systolic function remained unaffected. In the face of increased RV afterload, the newborn heart is able to maintain cardiac output, primarily by improving systolic RV function through homeometric autoregulation.

Improved contractile performance of right ventricle in response to increased RV afterload in newborn lamb

Pulmonary hypertension results in an increased afterload for the right ventricle (RV). To determine the effects of this increased afterload on RV contractile performance, we examined RV performance before and during 4 h of partial balloon occlusion of the pulmonary artery and again after releasing the occlusion in nine newborn lambs. RV contractile performance was quantified by indexes derived from systolic RV pressure-volume relations obtained by a combined pressure-conductance catheter during inflow reduction. An almost twofold increase of end-systolic RV pressure (from 22 to 38 mmHg) was maintained during 4 h. Cardiac output (CO) (0.74 +/- 0.08 l/min) and stroke volume (4.3 +/- 0.4 ml) were maintained, whereas end-diastolic volume (7.9 +/- 1.3 ml) did not change significantly during this period. RV systolic function improved substantially; the end-systolic pressure-volume relation shifted leftward indicated by a significantly decreased volume intercept (up to 70%), together with a slightly increased slope. In this newborn lamb model, maintenance of CO during increased RV afterload is not obtained by an increased end-diastolic volume (Frank-Starling mechanism). Instead, the RV maintains its output by improving contractile performance through homeometric autoregulation.

Respiratory muscle function in patients with chronic obstructive pulmonary disease

Respiratory muscle (RM) dysfunction is a progressive process, including both RM weakness and fatigue, that may advance to the point of respiratory failure. It occurs as a result of increased RM workloads, altered length-tension relationship of respiratory muscles, malnourished states, and altered cellular environment in chronic obstructive pulmonary disease (COPD). Consideration of multiple patient factors is necessary when identifying patient risk for RM dysfunction and designing plans of care. This article discusses the RM pump, including its measurement, in patients with COPD.

Exercise Doppler: functional evaluation of right heart dynamics

Exercise echocardiography is a versatile technique that includes not only two-dimensional imaging, but also Doppler of aortic, mitral, and tricuspid valves. Doppler echocardiography can be useful in the evaluation of global left ventricular systolic and diastolic function, valvular function, transvalvular gradients, and pulmonary artery pressure. The technique lends itself to the study of the cardiac response to exercise in a variety of disease states, including pulmonary, coronary artery, valvular, and congenital heart disease. We review our experience using agitated saline-enhanced Doppler of tricuspid insufficiency to determine pulmonary artery pressure throughout exercise in chronic lung disease.

Cardiovascular-pulmonary interaction in chronic obstructive pulmonary disease with special reference to the pathogenesis and management of cor pulmonale

Chronic obstructive pulmonary disease (COPD), which here refers to a group of diseases that have in common the physiologic defect of airway obstruction, is often associated with severe hemodynamic consequences. This article provides an overview of cardiovascular function in COPD with emphasis on recent advances in detecting, quantifying, and treating pulmonary hypertension and its major cardiac complication, cor pulmonale.

Pulmonary hemodynamics, gas exchange, and the severity of emphysema as assessed by quantitative CT scan in chronic bronchitis and emphysema

We have used the CT transthoracic scan to measure regional lung density in vivo, as our previous studies have shown that this correlates with the increase in size of distal air spaces, which is a defining characteristic of emphysema. We have studied 32 patients with chronic airflow limitation (FEV1, 15 to 68% predicted) caused by chronic bronchitis and emphysema (synonym, COPD), with a wide range of arterial PO2 (38 to 90 mm Hg) and PCO2 (32 to 63 mm Hg) while breathing air at rest. We could find no significant relationships between the extent of emphysema (as assessed in vivo by the EMI number defining the lowest fifth percentile of the CT density histogram of the lung fields) and either arterial blood gas tensions, mean pulmonary arterial pressure, cardiac output, or calculated total pulmonary vascular resistance while at rest (n = 32) or during supine leg exercise (n = 29). We conclude that the extent of emphysema does not correlate with the clinical or pathologic features of the "pink and puffing" (i.e., mild hypoxemia, no CO2 retention, no pulmonary hypertension, etc.) or "blue and bloated" (i.e., hypoxemia, CO2 retention, pulmonary hypertension) pattern of patients with COPD nor to the spectrum of hemodynamic and gas exchange abnormalities that commonly occur in patients between these two extreme examples. Thus, "pink puffers" should not be equated with "the emphysematous" pattern of this disease. Although these clinicophysiologic patterns remain valid as descriptions, they do not relate to the extent of underlying emphysema in COPD.

Improved recognition of cor pulmonale in patients with severe chronic obstructive pulmonary disease

To compare sensitivity of clinical methods (physical examination, electrocardiogram, and chest radiograph) to echocardiography in the detection of cor pulmonale, and to determine the role of nocturnal oxygen desaturation in its development, 33 non-hypoxemic patients who had severe chronic obstructive pulmonary disease (COPD) were evaluated by clinical methods, echocardiography, and overnight ear oximetry. Compared to 25 age-matched control subjects, COPD patients had higher peak pulmonary systolic pressures by contrast-enhanced Doppler (40 +/- 13 versus 22 +/- 5 mm Hg, or 5.3 +/- 1.7 versus 2.9 +/- 0.7 kPa) and ratios of right to left ventricular volume (1.1 +/- 0.6 versus 0.6 +/- 0.1, both p less than 0.05). Defining cor pulmonale as pulmonary hypertension, right ventricular enlargement, or right ventricular hypertrophy, 25 COPD patients (75 percent) had cor pulmonale by echocardiography and 13 (39 percent) by clinical methods (p less than 0.05). Nocturnal desaturation was present in only 21 percent of patients. Echocardiographic measurements were similar between patients with emphysema and patients with bronchitis, and between patients with and without sleep desaturation. In patients who have severe COPD without waking hypoxemia, cor pulmonale is detected nearly twice as often by echocardiography as by clinical methods, but is usually not associated with sleep desaturation.

Human atrial natriuretic peptide secretion in precapillary pulmonary hypertension. Clinical study in patients with COPD and interstitial fibrosis

Human atrial natriuretic peptide (hANP) is stored by granules of both human atria. Atrial distension appears to be a major stimulus for hANP secretion. Precapillary pulmonary hypertension increases right ventricular afterload and may thus cause right atrial distension. We therefore hypothesized that hANP plasma concentrations (1) are higher in the right atrium than in the peripheral vein, (2) are increased in patients with precapillary pulmonary hypertension, and (3) correlate with right atrial pressure. Thirty-three adult patients with chronic obstructive pulmonary disease (COPD) or interstitial fibrosis were examined by right heart catheterization. Mean pressures were measured in the right atrium, pulmonary artery, and pulmonary capillary wedge position, and blood was drawn from the right atrium and from a peripheral vein for determination of hANP levels. In general, hANP plasma levels in the right atrium were significantly higher than in a peripheral vein. Seventeen out of 33 patients had pulmonary hypertension, whereas 16 patients exhibited normal pulmonary artery mean pressures. In all patients, pulmonary arterial wedge pressure was normal. Plasma hANP concentrations were significantly higher in patients with pulmonary hypertension than in patients with normal pulmonary artery pressure. A strong correlation between central or peripheral hANP plasma levels (or both) and mean right atrial pressure could be observed (r = 0.75; p less than 0.001). From these data, we conclude that the increased secretion of hANP in our patients with precapillary pulmonary hypertension appears to be mediated by right atrial distension.

Pulmonary hypertension in chronic obstructive pulmonary disease. Multivariate analysis

The severity of pulmonary hypertension was evaluated by right cardiac catheterization in 89 patients with stable chronic obstructive pulmonary disease, both at rest and during maximum treadmill exercise. Thirty-one patients were found to have pulmonary hypertension at rest, defined as a mean pulmonary arterial pressure of 20 mm Hg or more. Although the remaining 58 patients had normal mean pulmonary arterial pressure at rest, three developed pulmonary hypertension during exercise (mean pulmonary arterial pressure greater than or equal to 35 mm Hg). Multiple anthropometric, spirometric, radiographic, and gas-exchange variables were analyzed and correlated with the hemodynamic data to define their value in predicting mean pulmonary arterial pressure. While arterial oxygen pressure (PaO2) at maximum exercise was the variable most highly correlated with resting mean pulmonary arterial pressure (r = -0.67), stepwise multiple linear regression analysis indicated that measurement of the diameter of the right descending pulmonary artery and arterial carbon dioxide tension (PaCO2) also contributed to the prediction of mean pulmonary arterial pressure. Spirometric indices of airflow obstruction, hyperinflation, and the diffusing capacity of the lung for carbon monoxide correlated poorly with the severity of pulmonary hypertension and consequently were not useful predictors of mean pulmonary arterial pressure. The threshold criteria of a PaO2 less than 60 mm Hg or a PaCO2 more than 40 mm Hg were reasonably accurate for a diagnosis of pulmonary hypertension. These arterial blood gas criteria were superior to the spirometric and radiographic variables examined in predicting pulmonary hypertension prior to the development of clinically overt cor pulmonale.

Cardiac output during exercise in patients with COPD

Cardiac output response was examined to determine its relationship to exercise and arterial hypoxia, pulmonary hemodynamics, and the clinical/lung mechanics profile of patients with chronic obstructive pulmonary disease (COPD). Twenty patients with COPD were examined on the treadmill at rest and during steady state exercise at the highest workload comfortably tolerable to the subjects (60-70% VO2 max). In eight patients, the exercise cardiac output was less than 80% of predicted, while in the remainder (n = 12), the cardiac output response was normal (greater than 80% of predicted). It was concluded that hyperinflation and severe expiratory airflow limitation may be important determinants of the low exercise cardiac output response in some patients with COPD.

Cardiovascular-pulmonary monitoring in the intensive care unit (Part 2)

Proliferation of technology in the ICU likely will continue at a rapid pace. This presents a strong challenge to the clinician's task of "above all, do not harm." While invasive techniques carry obvious direct risks, both invasive and noninvasive monitoring present a more subtle threat. Pitfalls in the acquisition and interpretation of data must be recognized before appropriate therapeutic decisions can be made. Advanced monitoring devices and techniques must supplement and not supplant clinical assessment.

Pulmonary hypertensive diseases

Pulmonary hypertension may occur as a primary disorder of the pulmonary vasculature or secondary to a variety of cardiac or pulmonary diseases. The reversibility of pulmonary hypertension is dependent on the relative contribution of reversible vasoconstriction and irreversible structural changes in the pulmonary vessels. Despite recent advances in the understanding of pulmonary vascular physiology, knowledge of the pathogenesis and natural history of pulmonary hypertension has been limited by an inability to measure pulmonary arterial pressure noninvasively. Thus, when patients have symptoms or signs of pulmonary hypertension, the disease is usually at an advanced stage. It is possible that early in the course of hypoxic pulmonary disease, pulmonary hypertension may be protective in optimizing matching of ventilation and perfusion. It is not known at what point pulmonary hypertension per se becomes harmful. Certainly, treatment directed at underlying cardiac or pulmonary disease is indicated. It also seems reasonable to treat severe degrees of pulmonary hypertension complicated by right ventricular dysfunction. With the advent of orally effective pulmonary vasodilators, direct treatment of primary and secondary pulmonary hypertension may now be possible. Hopefully, with careful clinical evaluation of the response to vasodilator therapy, we will learn whether these drugs prolong life and reduce morbidity in primary and secondary pulmonary hypertension. In the meantime, much more information is needed regarding the mechanisms of acute pulmonary vasoconstriction and sustained pulmonary hypertension. In addition, a means of early identification of patients with mild hypertension is needed.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of digoxin on exercise capacity and right ventricular function during exercise in chronic airflow obstruction

We evaluated 12 patients with stable chronic airflow obstruction (CAO) and no clinical evidence of left ventricular disease to determine the effects of oral digoxin on exercise capacity (VO2 max) and on right ventricular pump function during exercise. In this randomized, double blind, placebo controlled, cross-over study, patients performed exercise tests and underwent measurement of ejection fractions after two weeks of therapy with oral digoxin (0.25 mg/day) and after two weeks of placebo. Incremental upright exercise testing to a symptom-limited maximum was performed on a cycle ergometer. Right and left ventricular ejection fractions (RVEF, LVEF) were obtained in the supine position at rest and at approximately 75 percent of the maximum workload by gated equilibrium radionuclide angiography. All patients had abnormal right ventricular function, manifested either by a low resting RVEF (less than 45 percent) or a subnormal response to exercise (less than 5 percent increase). The small increases in RVEF with digoxin (mean +/- SE) at rest (44 +/- 5 vs 41 +/- 4 percent) and during exercise (46 +/- 4 vs 44 +/- 3 percent) did not achieve statistical significance. With digoxin, small increases in exercise duration (10.0 +/- 1.5 vs 9.0 +/- 1.4 min), maximum workload achieved (48 +/- 6 vs 42 +/- 5 W), VO2 max (0.85 +/- 0.06 vs 0.81 +/- 0.06 L/min), and oxygen-pulse (O2-P) (6.6 +/- 0.5 vs 6.3 +/- 0.4 ml/beat) occurred. Only the increase in O2-P was significant (p less than 0.05). From this study we conclude that digoxin does not significantly improve exercise capacity in severe chronic airflow obstruction with impaired right ventricular function, nor does it improve RVEF either at rest or during supine submaximal exercise.