Can pulmonary vasodilators improve survival in cor pulmonale due to hypoxic chronic bronchitis and emphysema?

Pulmonary vascular effects of pulsed inhaled nitric oxide in COPD patients with pulmonary hypertension

Introduction

Severe chronic obstructive pulmonary disease (COPD) is often associated with secondary pulmonary hypertension (PH), which worsens prognosis. PH can be lowered by oxygen, but also by inhaled nitric oxide (NO), which has the potential to improve the health status of these patients. NO is an important mediator in vascular reactions in the pulmonary circulation. Oral compounds can act through NO-mediated pathways, but delivering pulsed inhaled NO (iNO) directly to the airways and pulmonary vasculature could equally benefit patients. Therefore, a proof-of-concept study was performed to quantify pulmonary blood vessel caliber changes after iNO administration using computed tomography (CT)-based functional respiratory imaging (FRI).

Methods

Six patients with secondary PH due to COPD received “pulsed” iNO in combination with oxygen for 20 minutes via a nasal cannula. Patients underwent a high-resolution CT scan with contrast before and after iNO. Using FRI, changes in volumes of blood vessels and associated lobes were quantified. Oxygen saturation and blood pressure were monitored and patients were asked about their subjective feelings.

Results

Pulmonary blood vessel volume increased by 7.06%±5.37% after iNO. A strong correlation (Ω²₀=0.32, P=0.002) was obtained between ventilation and observed vasodilation, suggesting that using the pulsed system, iNO is directed toward the ventilated zones, which consequently experience more vasodilation. Patients did not develop oxygen desaturation, remained normotensive, and perceived an improvement in their dyspnea sensation.

Conclusion

Inhalation of pulsed NO with oxygen causes vasodilation in the pulmonary circulation of COPD patients, mainly in the well-ventilated areas. A high degree of heterogeneity was found in the level of vasodilation. Patients tend to feel better after the treatment. Chronic use trials are warranted.

Normalization of deranged signal transduction in lymphocytes of COPD patients by the novel calcium channel blocker H-DHPM

Investigations on the role of intracellular Ca(2+) ion concentration in the mechanism of development of COPD in smokers and non-smokers were carried out. The intracellular Ca(2+) levels were found to be increased in human lymphocytes in patients with COPD as compared to non-smokers and smokers without COPD. The investigations reveal an association in altered intracellular Ca(2+) regulation in lymphocytes and severity of COPD, by means of significant activation of Protein kinase C and inducible nitric oxide synthase (iNOS). The effect of a novel calcium channel blocker ethyl 4-(4'-heptanoyloxyphenyl)-6-methyl-3,4-dihydropyrimidin-2-one-5-carboxylate (H-DHPM) as a potential candidate for the treatment of COPD was also investigated. H-DHPM treated cells showed a decrease in intracellular Ca(2+) level as compared to the control cells. Molecular studies were carried out to evaluate the expression profile of NOS isoforms in human lymphocytes and it was shown that H-DHPM decreases the increased iNOS in COPD along with reestablishing the normal levels of endothelial nitric oxide synthase (eNOS). The results of H-DHPM were comparable with those of Amlodipine, a known calcium channel blocker. Calcium channel blocker H-DHPM proves to be a potential candidate for the treatment of COPD and further clinical studies are required to prove its role in the treatment of pulmonary hypertension (PH).

Use of nitric oxide inhalation in chronic obstructive pulmonary disease

BACKGROUND

Inhalation of nitric oxide with oxygen could be a promising treatment in patients with chronic obstructive pulmonary disease (COPD) and pulmonary hypertension. However, the current methods of delivery of NO are cumbersome and unsuitable for long term use. The present study was undertaken to investigate the safety and efficacy of a mixture of nitric oxide (NO) and oxygen administered via a nasal cannula for 24 hours in patients with oxygen dependent COPD.

METHODS

Twenty five parts per million (ppm) of NO was administered by inhalation combined with supplemental oxygen at a flow rate of 2 l/min via a nasal cannula for 24 hours to 11 ambulatory men with stable, oxygen dependent COPD. Room air with supplemental oxygen at 2 l/min was administered in an identical manner for another 24 hours as control therapy in a randomised, double blind, crossover fashion to all patients. Pulmonary function tests, exercise tolerance, dyspnoea grade, and lung volumes were measured at baseline, 24, and 48 hours. Pulmonary artery pressure (PAP), cardiac output (CO), pulmonary vascular resistance (PVR), arterial blood gas tensions, and minute ventilation were measured at baseline, after 30 minutes and 24 hours of breathing NO and oxygen. Venous admixture ratio (Qs/Qt) and dead space ratio (Vd/Vt) were also calculated. Concentrations of nitrogen dioxide (NO(2)) and NO in the inhaled and ambient air were monitored continuously. Differences in pulmonary function, arterial blood gas tensions, pulmonary haemodynamics, exercise tolerance, and dyspnoea between oxygen and NO breathing periods were analysed for significance using paired t tests.

RESULTS

A significant (p<0.05) fall was observed in PVR (183.1 (116.05) and 137.2 (108.4) dynes.s.cm(-3) before and after breathing NO for 24 hours, respectively) with NO administration without significant changes in symptoms, pulmonary function, arterial oxygen tension, or exercise tolerance.

CONCLUSIONS

NO at a concentration of 25 ppm blended with oxygen can be safely administered by nasal cannula for 24 hours without significant adverse effects and lowers PVR in stable patients with COPD receiving long term oxygen therapy.

A comparison of two long-acting vasoselective calcium antagonists in pulmonary hypertension secondary to COPD

STUDY OBJECTIVES AND PATIENTS: Pulmonary hypertension (PH) is common in COPD and may predict mortality in this disorder. We have compared the pulmonary vasodilator effects, dose-response characteristics, and tolerability of two calcium channel blockers, amlodipine and extended-release (ER) felodipine, in 10 patients (seven men, age 68+/-4.8 [SD] years) with clinically stable COPD and PH.

DESIGN

Drugs were given in equal single daily oral doses (2.5, 5, and 10 mg), increasing weekly for 3 weeks, in a randomized investigator-blinded crossover manner with a 1-week wash-out period between the two treatments.

MEASUREMENTS

Doppler measurements of pulmonary hemodynamics were made on the seventh day of treatment at each drug dose. Lung function, arterial blood gases, and adverse events were also monitored weekly.

RESULTS

A dose-dependent decline of pulmonary artery pressure (PAP) was observed with each drug. A dose of 2.5 mg produced a significant decrease in PAP compared with baseline (20% amlodipine, 17% felodipine ER). Additional decreases in PAP were observed at 5 mg and 10 mg that were similar for both drugs, but did not reach statistical significance compared with 2.5 mg. There was a dose-related decrease in pulmonary vascular resistance and increase in oxygen delivery with amlodipine and felodipine ER. Lung function and blood gas values were stable throughout. Side effects (headache and ankle edema) were less frequent during amlodipine treatment (p<0.05).

CONCLUSIONS

Both amlodipine and felodipine ER, given as a single daily oral dose of > or = 2.5 mg, are effective pulmonary vasodilators in COPD patients with PH. Their dose-response characteristics are similar, but amlodipine treatment was associated with fewer side effects.

Haemodynamic effects of atrial natriuretic peptide in hypoxic chronic obstructive pulmonary disease

BACKGROUND

Pulmonary artery pressure is elevated in patients with advanced chronic obstructive pulmonary disease (COPD). Release of atrial natriuretic peptide (ANP) is increased in pulmonary hypertension and this hormone may both selectively vasodilate pulmonary vessels and inhibit pulmonary vascular remodelling. The hypothesis that ANP has a physiological role in protection of the pulmonary circulation from pressure overload, and that it may be beneficial in patients with COPD, has been examined.

METHODS

Ten patients with hypoxic COPD were infused for 30 minute periods with saline followed by ANP at 0.4, 2, and 10 pmol/kg/min respectively via a pulmonary artery catheter whilst monitoring haemodynamics and oxygenation.

RESULTS

Levels of immunoreactive ANP (irANP) increased from a mean (SD) of 23 (15) pmol/l to a maximum of 94 (41) pmol/l. Neither systemic blood pressure, cardiac output nor total systemic vascular resistance showed any correlation with irANP levels. There were negative correlations between levels of ANP and mean pulmonary artery pressure which fell from 28.7 to 25.9 mm Hg, pulmonary artery wedge pressure which fell from 6.5 to 4.6 mmHg, and total pulmonary vascular resistance which fell from 489 to 428 dynes s cm-5. There was a small fall in PaCO2 from 6.2 to 5.9 kPa, whilst venous admixture and oxygen delivery both increased non-significantly.

CONCLUSIONS

At these pathophysiological concentrations there was evidence that ANP selectively reduced right ventricular afterload. These data support the hypotheses that increased plasma levels of ANP may be beneficial in hypoxic COPD, and that endogenous ANP may ameliorate pulmonary hypertension in humans.

Felodipine improves pulmonary hemodynamics in chronic obstructive pulmonary disease

Pulmonary hypertension in chronic obstructive pulmonary disease (COPD) is associated with a poor prognosis. Reduction of pulmonary artery pressure in COPD by prolonged oxygen treatment has been shown to be associated with increased survival. In an attempt to find a suitable pharmacologic method of reducing pulmonary artery pressure and pulmonary vascular resistance in COPD, we enrolled 13 stable pulmonary-hypertensive, hypoxemic COPD patients in a study to test the effects of felodipine, a relatively new, vascular-selective calcium antagonist. Doppler echocardiography was used to estimate pulmonary artery pressure and cardiac output before treatment, 2, 7, and 12 weeks during felodipine treatment (10 to 20 mg/d), and after a 1-week placebo washout period. Measurements of lung function, arterial blood gases, and exercise capacity during an incremental bicycle ergometer test were also performed at intervals during the study period. Three patients withdrew from the study and of the remaining 10, 8 had some side effects of medication (peripheral edema or headache) that improved either spontaneously or following a reduction in drug dose. In the 10 patients who completed the study (8 male; mean age, 67 years), felodipine resulted in significant reductions in mean pulmonary artery pressure (22 percent) and total pulmonary (vascular) resistance (30 percent) and increases in cardiac output (15 percent) and stroke volume (13 percent) compared with baseline measurements and those taken after placebo washout. These effects were sustained over the 12 weeks of felodipine treatment. There was no adverse effect of felodipine treatment on pulmonary gas exchange at rest or during exercise and no change in lung function or exercise capacity. We conclude that in pulmonary hypertensive, hypoxemic COPD patients, felodipine substantially improves pulmonary hemodynamics.

Effect of nifedipine on physiologic shunting and oxygenation in chronic obstructive pulmonary disease

PURPOSE

To assess changes in physiologic shunting and oxygenation following short-term treatment with nifedipine in patients with pulmonary hypertension secondary to chronic obstructive pulmonary disease.

PATIENTS AND METHODS

Changes in pulmonary vascular pressure, pulmonary vascular resistance, venous admixture, and systemic arterial oxygen tension following sublingual administration of 20 mg of nifedipine were studied in 18 patients (13 men, 5 women; mean age of 59.7 [SD 7.2] years) using Swan-Ganz catheterization. These patients had a mean peak expiratory flow rate of 112 (SD 27) L/min (mean 22.2 [SD 12.2]% of predicted value), mean forced expiratory volume in 1 second (FEV1) of 0.84 (SD 0.23) L (mean 31.2 [SD 8.5]% of predicted value), mean FEV1/forced vital capacity ratio of 31.6 (SD 4.5), and mean carbon monoxide diffusing capacity of 6.8 (SD 1.96) mmol/min/kPa.

RESULTS

There was a significant decrease in mean pulmonary vascular resistance (562 to 371 dyne sec.cm-5) and a significant reduction in the mean pulmonary arterial pressure (mean 32.8 to 23.6 mm Hg). Pulmonary venous admixture, however, increased significantly from the baseline mean of 44.6% (SD 16.1) to a mean of 56% (SD 15.6), and the mean arterial oxygen tension decreased from 5.8 (SD 1.3) kPa to 4.5 (SD 0.8) kPa at 60 minutes following drug administration (p < 0.001).

CONCLUSION

The role of nifedipine in the treatment of pulmonary hypertension secondary to chronic bronchitis may be limited because of its deleterious effect on venous admixture.

Long-term prazosin therapy for COPD pulmonary hypertension

A 51-year-old patient with COPD, obesity, and pulmonary hypertension underwent long-term prazosin therapy after a successful hemodynamic response to 1 mg of oral prazosin. The 18-month administration of prazosin, in a dose of 3 mg a day, resulted in continued hemodynamic and echocardiographic benefits.

Right ventricular dysfunction in chronic obstructive pulmonary disease. Evaluation and management

Cor pulmonale is an important consequence of COPD. Although the incidence is not precisely known, it is seen more frequently in patients with hypoxemia, CO2 retention and severely reduced FEV1. When present, it limits peripheral oxygen delivery, increases shortness of breath, and reduces exercise endurance. It is also associated with higher mortality rates independent of other prognostic variables. Numerous factors may contribute to the development of cor pulmonale in patients with COPD, but its primary cause is chronic alveolar hypoxia resulting in pulmonary vasoconstriction, vascular remodeling and pulmonary hypertension. The physical exam, chest radiograph and ECG may be helpful in detecting the presence of cor pulmonale, but because of anatomic changes that occur in the chest, these tests are often insensitive in patients with COPD. Noninvasive diagnostic techniques utilizing Doppler echocardiography and radionuclide angiography allow for detection of RV dysfunction at an earlier stage and in most cases, preclude the need for right heart catheterization. LTO2 is the only therapy shown to improve survival in patients with COPD. However, statistical proof correlating improvements in pulmonary hemodynamics with increased survival is lacking. Bronchodilators, such as the beta 2 agonists and especially theophylline, may have beneficial effects on pulmonary hemodynamics in addition to their effect on respiratory function and are useful in COPD when RV dysfunction is present. Diuretics and phlebotomy are also useful in improving symptoms in appropriate patients. Vasodilators such as calcium channel blockers and ACE-inhibitors may improve pulmonary hemodynamics acutely, but may lower arterial PO2 by worsening ventilation-perfusion matching or blunt the improvement in pulmonary hemodynamics seen with supplemental oxygen. The long-term benefits of these agents have not been proven and their routine use in patients with cor pulmonale due to COPD cannot be recommended.

Should patients have cardiac catheterization prior to long-term oxygen treatment?

Pulmonary arterial pressure predicts survival in patients with hypoxic chronic obstructive pulmonary disease as does the presence of cor pulmonale. Thus, cardiac catheterization has been performed prior to treatment for long-term oxygen therapy (LTOT) in order to 1) assess the suitability of patients for LTOT, 2) predict survival in patients receiving LTOT and 3) for research in cor pulmonale. In this review I will submit the evidence which suggests that these indications for measurement of pulmonary haemodynamics are not justified, and measurements of arterial blood gas values and assessment of airflow limitation are all that is necessary prior to LTOT.

Contractility of papillary muscle from rats exposed to 28 days of hypoxia, hypercapnia, and hypoxia with hypercapnia

The effects of chronic respiratory failure (hypoxia and hypercapnia) on the contractile properties of cardiac muscle are not established. A study was performed of the isometric contractile properties of isolated papillary muscle removed from rats exposed in a normobaric environmental chamber to 28 days of hypoxia (fractional inspired oxygen (FIO2) 10%, fractional inspired carbon dioxide (FICO2) less than 1%), hypercapnia (FIO2 21%, FICO2 5%), and hypoxia with hypercapnia (FIO2 10%, FICO2 5%). Rats exposed to both hypoxia and hypoxia with hypercapnia developed selective right ventricular hypertrophy. Exposure to hypercapnia alone did not alter right ventricular weight. No change in right ventricular papillary muscle contractility per unit muscle mass was observed as measured by maximum active tension, maximum rate of rise or fall of tension, or time to peak tension. Rat cardiac muscle adapts successfully to the altered acid-base environment and increased work load associated with prolonged exposure to hypoxia and mild hypercapnia.

Chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is equated with chronic bronchitis and emphysema as one disease entity. In COPD airflow limitation is relatively persistent--unlike asthma. Tests for "small-airways disease" form no part of routine practice, for their accuracy in detecting pathological change is debatable. The proteolytic theory of the pathogenesis of emphysema highlights the role of neutrophil elastase, antielastases, oxidants, antioxidants, and thus of potential new treatments. Clinical features of COPD include breathlessness, cough, and sputum, with airflow obstruction and lung hyperinflation. The differential diagnosis includes bronchiectasis, cystic fibrosis, and pulmonary hypertension, but pulmonary fibrosis, etc., is distinguished by radiological infiltrates. Plain chest radiography cannot reliably diagnose emphysema in life, but a new method measuring lung density from the computed tomographic (CT) scan allows location, quantitation, and diagnosis of emphysema (defined by enlargement of distal air spaces) in humans in life. "Pink puffers" with breathlessness, hyperinflation, mild hypoxemia, and a low PCO2 are contrasted with "blue bloaters" with hypoxemia, secondary polycythemia, CO2 retention, and pulmonary hypertension and cor pulmonale. Antismoking measures are a major aim in management. A bronchodilator regimen combining a slow-release oral theophylline with an inhaled beta 2-agonist, ipratropium, and high-dose inhaled steroids is proposed because even modest improvement in obstruction can help these patients. In acute exacerbations with purulent sputum, antimicrobials against Streptococcus pneumoniae and Hemophilus influenzae are used with controlled oxygen therapy aiming to keep the arterial PO2 over 50 mm Hg without the pH falling below 7.25. Influenza prophylaxis is recommended, but pneumococcal vaccination remains debatable. Chronic under-nutrition in "emphysema" implies controlled trials of feeding regimens--but these remain to be assessed. Long-term oxygen therapy is the only treatment known to prolong life in blue bloaters, and oxygen concentrators and transtracheal oxygen delivery are discussed. Pulmonary vasodilators (e.g., beta 2-agonists, hydralazine, nifedipine, angiotensin-converting enzyme [ACE] inhibitors, etc.) have not yet been proved to provide long-term reduction in pulmonary arterial pressure. Blue bloaters have severe nocturnal hypoxemia in rapid eye movement (REM) sleep that is corrected by oxygen or the investigational drug almitrine.(ABSTRACT TRUNCATED AT 400 WORDS)