Skip to content


  • Commentary
  • Open Access

Pulmonary hypertension associated with COPD

Critical Care20015:286

Published: 3 November 2001


Pulmonary hypertension is a common complication of chronic obstructive pulmonary disease (COPD). The increase in pulmonary artery pressures is often mild to moderate, but some patients may suffer from severe pulmonary hypertension, and present with a progressively downhill clinical course because of right-sided heart failure added to ventilatory handicap. The cause of pulmonary hypertension in COPD is generally assumed to be hypoxic pulmonary vasoconstriction leading to permanent medial hypertrophy. However, recent pathological studies point, rather, to extensive remodeling of the pulmonary arterial walls, with prominent intimal changes. These aspects account for minimal reversibility with supplemental oxygen. There may be a case for pharmacological treatment of pulmonary hypertension in selected patients with advanced COPD and right-sided heart failure. Candidate drugs include prostacyclin derivatives, endothelin antagonists and inhaled nitric oxide, all of which have been reported of clinical benefit in primary pulmonary hypertension. However, it will be a challenge for randomized controlled trials to overcome the difficulties of the diagnosis of right ventricular failure and the definition of a relevant primary endpoint in pulmonary hypertensive COPD patients.


chronic obstructive pulmonary diseasedobutamineexercisenitric oxideoxygenpulmonary hypertensionright ventricular failure


The article by Vizza and colleagues in this issue of Critical Care [1] raises interesting questions about the clinical relevance of pulmonary hypertension in chronic obstructive pulmonary disease (COPD) This form of pulmonary hypertension is generally believed to be hypoxic in origin and to be associated with only mild to moderate increases in mean pulmonary artery pressures (Ppa), amenable to supplemental oxygen. However, recent studies suggest a rather more complex pathobiology, leading to severe pulmonary hypertension in some patients, who might therefore benefit from more active and specific therapy.

Nature of pulmonary hypertension in COPD

Pulmonary vascular remodeling in COPD is more than just medial hypertrophy from long-lasting hypoxic vasoconstriction [2,3]. In fact, as illustrated in Fig. 1, all layers of the vessel wall appear to be involved, with intimal changes being the most prominent. This peculiar pathological picture could be explained by the combined effects of hypoxia, mechanical stress and/or inflammatory reaction due to repeated stretching of hyperinflated lungs [2], and, very importantly, the toxic effects of cigarette smoke [3]. Chronic hypoxia at high altitudes induces isolated medial hypertrophy (with, sometimes, longitudinal deposition of a few smooth muscle fibers in the intima) and is associated with complete reversal of pulmonary hypertension a few weeks after return to sea level [4]. Pulmonary hypertension in COPD often is not, or is only minimially, reversible by supplemental oxygen, acutely [5] or chronically [6].
Figure 1
Figure 1

Optic-microscopic view of a pulmonary artery from a patient with pulmonary hypertension secondary to COPD. All three vessel wall layers are remodeled, with prominent intimal thickening.

Pulmonary hypertension in COPD is generally limited to an increase in mean pulmonary artery pressure (Ppa) to 25–35 mmHg in the face of a normal cardiac output (Q) [7]. However, as illustrated in Table 1, mean pulmonary artery pressures higher than 40 mmHg are not uncommon, especially in patients with at least one previous episode of acute respiratory failure [7]. The experience of patients with primary pulmonary hypertension, in whom the disease process is limited to the pulmonary vasculature, shows that pulmonary artery pressures higher than 35–40 mmHg are associated with clinical right ventricular failure and limited exercise capacity [8].
Table 1

Hemodynamics at rest in 74 patients with advanced chronic obstructive pulmonary disease (from [7])






of normal

Q (l/min per m2)

3.8 ± 0.8



Pra (mmHg)

4 ± 4



Pla (mmHg)

6 ± 4



Ppa (mmHg)

35 ± 12



PVR (dyne·s·cm-5 per m2)

660 ± 284



Values are mean ± SD. Pla = left atrial pressure (estimated from a pulmonary artery occluded pressure); Ppa = mean pulmonary artery pressure; Pra = right atrial pressure; PVR = pulmonary vascular resistance; Q = cardiac output.

Dobutamine versus exercise stress tests

How to detect COPD patients prone to the development of severe pulmonary hypertension? One could imagine a dobutamine stress test would be revealing, with the rationale that an increase in flow would be associated with an abnormal increase in Ppa because of a restricted pulmonary vascular bed. However, in most patients with COPD, the increase in Ppa with blood flow is less than predicted by the pulmonary vascular resistance (PVR) equation. Unilateral balloon occlusion studies have shown that the passive Ppa:Q curve in COPD is shifted to higher pressures with a decreased slope and an increased extrapolated pressure intercept [9], suggesting vascular closure [10]. The same phenomenon was observed with dobutamine in Vizza's study [1], which is not surprising, because a low dose of dobutamine increases flow without having an intrinsic effect on pulmonary vascular tone [11]. Vascular closure in COPD can be explained by high pulmonary volume-induced stretching of alveolar vessels and dynamic hyperinflation, as well as by remodeling of the pulmonary arteries. As illustrated in Fig. 2, a Ppa:Q relationship with decreased slope makes calculated PVR unreliable for the estimation of changes in the functional state of pulmonary resistive vessels at variable flow. In other words, a decrease in PVR brought about by dobutamine should not be interpreted as a pulmonary vasodilation.
Figure 2
Figure 2

Relations between mean pulmonary artery pressure (Ppa) minus left atrial pressure (Pla) and pulmonary blood flow in a representative patient with COPD at rest (A) and at exercise (C), redrawn from reference 9. Dobutamine is supposed to induce a passive increase in flow. Pulmonary vascular resistance (PVR) is the slope of the (Ppa-Pla)/Q relation. Passive increases in flow (A to B and C to D) increase pressure less than predicted by the PVR equation. Exercise (A to C and B to D) increases pressure more than predicted by the PVR equation.

Exercise has been used to detect familial susceptibility to pulmonary hypertension [12]. Exercise in COPD may be associated with marked increases in Ppa, especially when there is pre-existing pulmonary hypertension at rest [13]. Patients with exercise-induced pulmonary hypertension are particularly prone to develop resting pulmonary hypertension in the long term [14]. As illustrated in Fig. 2, the increase in Ppa in exercising COPD patients is greater than predicted by the PVR equation, indicating pulmonary vasoconstriction [15]. This unexpectedly large increase may be due to enhancement of hypoxic pulmonary vasoconstriction by decreased mixed venous partial pressure of oxygen, increased tone of the sympathetic nervous system, and decreased arterial pH due to aggravated hypercapnia or lactic acidosis or both. Changes in intrathoracic pressures may also play a role. An exercise-induced increase in ventilation may aggravate dynamic hyperinflation and thereby increase alveolar pressure at expiration. Increased ventilation in the presence of obstructed airways is associated with markedly negative inspiratory pleural pressures. Negative pleural pressures are associated with decreased ventricular pressures relative to alveolar pressure and therefore correspond to an increase in right ventricular afterload.

Right ventricular failure and its treatment

Severe pulmonary hypertension increases right ventricular afterload and eventually leads to the clinical syndrome of right-sided heart failure with systemic congestion and inability to adapt right ventricular output to peripheral demand at exercise. Many patients with advanced COPD present with ankle edema but normal right atrial pressures (at rest) [16]. This apparent paradox has stimulated speculation that edema in COPD might be a renal rather than a right ventricular problem [17]. However, edema in COPD is probably explained by repeated stretching of the right atrium because of increased right ventricular diastolic pressures at exercise or conceivably during sleep apneas, causing increased tone of the sympathetic nervous system and activation of the renin–angiotensin–aldosterone system, with resultant renal retention of salt and water [18]. Such retention may be aggravated by hypercapnia [17,18].

What could be done to relieve the overloaded right ventricle in COPD? In addition to optimal bronchodilation to limit dynamic hyperinflation and negative pleural pressure swings, oxygen to correct hypoxemia, and diuretics to limit salt and water retention, it might be possible to limit pulmonary vascular remodeling by pharmacological interventions. Pulmonary arteries from patients who have COPD show impaired endothelium-dependent vasorelaxation [19,20]. Pulmonary arteries from heavy smokers present show a reduction in expression of endothelial nitric oxide synthase [21]. Altered endothelial function, with a vasodilator–vasoconstrictor imbalance, appears to play a role in the progression of primary pulmonary hypertension [8]. Accordingly, prostacyclin derivatives, given intravenously [22], subcutaneously [23], by inhalation [24] or even orally [25], and endothelin-receptor antagonists [26], have been reported to improve the condition of patients with primary pulmonary hypertension. Inhaled nitric oxide, given as pulses together with supplemental oxygen, might also be effective [27]. It thus appears possible to restore the endothelial vasoconstrictor–dilator imbalance.


At this stage, a randomized, controlled trial with one of these agents might be justified in patients with advanced COPD and clinically significant right-sided heart failure. There could be concern that vasodilators might aggravate hypoxemia by increasing ventilation/perfusion mismatching through an inhibition of hypoxic vasoconstriction or/and an increase in blood flow [15,28,29]. However, since most of the hypoxemia in COPD is caused by low ventilation/ perfusion ratios, rather than by an intrapulmonary shunt, this can be easily corrected by a slight increase in supplemental oxygen [30].



COPD = chronic obstructive pulmonary disease


PaO2 = arterial partial pressure of oxygen


Pla = left atrial pressure


Ppa = mean pulmonary artery pressure


PVR = pulmonary vascular resistance


Q = cardiac output.


Authors’ Affiliations

Department of Pathophysiology, Erasme Campus of the Free University of Brussels, Belgium
Department of Pulmonary Medicine, Hospital Clinic, University of Barcelona, Spain


  1. Vizza CD, Della Rocca G, Di Roma A, Iacobini C, Pierconti F, Venuta F, Rendina E, Schmid G, Pietropaoli P, Fedele F: Acute hemodynamic effects of inhaled nitric oxide, dobutamine, and their combination in patients with mild to moderate secondary pulmonary hypertension. Crit Care 2002, in press.Google Scholar
  2. Wilkinson M, Langhorn CA, Heath D, Barer GR, Howard P: A pathophysiological study of 10 cases of hypoxic cor pulmonale. Q J Med 1988, 66: 65-85.PubMedGoogle Scholar
  3. Peinado VI, Barbera JA, Abate P, Ramirez J, Roca J, Santos S, Rodriguez-Roisin R: Inflammatory reaction in pulmonary muscular arteries of patients with mild chronic obstructive pulmonary disease. Am J Respir Crit Care Med 1999, 59: 1605-1611.View ArticleGoogle Scholar
  4. Heath D, Williams DR: Pulmonary hypertension. In High-Altitude Medicine and Pathology. London: Butterworths, 1989, 102-114.Google Scholar
  5. Lejeune P, Mols P, Naeije R, Hallemans R, Mélot C: Acute hemodynamic effects of controlled oxygen therapy in decompensated chronic obstructive pulmonary disease. Crit Care Med 1984, 12: 1032-1035.View ArticlePubMedGoogle Scholar
  6. Timms RM, Khaja FU, Williams GW, and the Nocturnal Oxygen Therapy Trial Group: Hemodynamic response to oxygen therapy in chronic obstructive pulmonary disease. Ann Intern Med 1985, 102: 29-36.View ArticlePubMedGoogle Scholar
  7. Naeije R: Should pulmonary hypertension be treated in chronic obstructive pulmonary disease? In The Diagnosis and Treatment of Pulmonary Hypertension. Edited by Weir EK, Archer SL, Reeves JT. New York: Futura Publishing, 1992, 209-239.Google Scholar
  8. Rubin LJ: Primary pulmonary hypertension. N Engl J Med 1977, 336: 111-117. 10.1056/NEJM199701093360207View ArticleGoogle Scholar
  9. Harris P, Segel N, Bishop JM: The relation between pressure and flow in the pulmonary circulation in normal subjects and in patients with chronic bronchitis and mitral stenosis. Cardiovasc Res 1968, 2: 73-83.View ArticlePubMedGoogle Scholar
  10. McGregor M, Sniderman A: On pulmonary vascular resistance: the need for more precise definition. Am J Cardiol 1985, 55: 217-221.View ArticlePubMedGoogle Scholar
  11. Lejeune P, Naeije R, Leeman M, Mélot C, Deloof T, Delcroix M: Effects of dopamine and dobutamine on hyperoxic and hypoxic pulmonary vascular tone in dogs. Am Rev Respir Dis 1987, 136: 29-37.View ArticlePubMedGoogle Scholar
  12. Grunig E, Janssen B, Mereles D, Barth U, Borst MM, Vogt IR, Fischer C, Olschewski H, Kuecherer HF, Kubler W: Abnormal pulmonary artery pressure response in asymptomatic carriers of primary pulmonary hypertension gene. Circulation 2000, 102: 1145-1150.View ArticlePubMedGoogle Scholar
  13. Riley RL, Himmelstein A, Morley HL, Motley HL, Weiner HM, Cournand A: Studies on the pulmonary circulation at rest and during exercise in normal individuals and in patients with chronic pulmonary disease. Am J Physiol 1948, 152: 372-382.PubMedGoogle Scholar
  14. Kessler R, Faller M, Weitzenblum E, Chaouat A, Aykut A, Ducolone A, Ehrhart M, Oswald-Mammosser M: "Natural history" of pulmonary hypertension in a series of 131 patients with chronic obstructive lung disease. Am J Respir Crit Care Med 2001, 164: 219-224.View ArticlePubMedGoogle Scholar
  15. Agustí AGN, Barberà JA, Roca J, Wagner PD, Guitart R, Rodriguez-Roisin R: Hypoxic pulmonary vasoconstriction and gas exchange during exercise in chronic obstructive pulmonary disease. Chest 1990, 97: 268-275.View ArticlePubMedGoogle Scholar
  16. Bauduin SV: Oedema and cor pulmonale revisited. Thorax 1997, 52: 401-402.View ArticleGoogle Scholar
  17. MacNee W: Pathophysiology of cor pulmonale in chronic obstructive pulmonary disease. Am J Respir Crit Care Med 1994, 150: 833-852.View ArticlePubMedGoogle Scholar
  18. Naeije R: Cor pulmonale. In Pulmonary Diseases. Edited by Grassi C, Brambilla C, Stockley RA, Naeije R, Rodriguez-Roisin R, Fishman AP. McGraw-Hill Clinical Medicine Series. London: McGraw-Hill International (UK) Ltd, 1999, 355-364.Google Scholar
  19. Dinh-Xuan AT, Higenbottam TW, Clelland CA, Pepke-Zaba J, Cremona G, Butt AY, Large SR, Wells FC, Wallwork J: Impairment of endothelium-dependent pulmonary artery relaxation in chronic obstructive lung disease. N Engl J Med 1991, 324: 1539-1547.View ArticlePubMedGoogle Scholar
  20. Peinado VI, Barberà JA, Ramirez J, Gomez FP, Roca J, Jover L, Gimferrer JM, Rodriguez-Roisin R: Endothelial dysfunction in pulmonary arteries of patients with mild COPD. Am J Physiol 1998, 274: L908-L913.PubMedGoogle Scholar
  21. Barbera JA, Peinado VI, Santos S, Ramirez J, Roca J, Rodriguez-Roisin R: Reduced expression of endothelial nitric oxide synthase in pulmonary arteries of smokers. Am J Respir Crit Care Med 2001, 164: 709-713.View ArticlePubMedGoogle Scholar
  22. Barst RJ, Rubin LJ, Long WA, McGoon MD, Rich S, Badesch DB, Groves BM, Tapson VF, Bourge RC, Brundage BH, Koerner SK, Langleben D, Keller CA, Murali S, Uretsky BF, Clayton LM, Jobsis M, Blackburn SD, Shortino D, Crow JW: A comparison of continuous intravenous epoprostenol (prostacyclin) with conventional therapy for primary pulmonary hypertension. N Engl J Med 1996, 334: 296-301. 10.1056/NEJM199602013340504View ArticlePubMedGoogle Scholar
  23. Barst R, Simonneau G, Rich S, Blackburn S, Naeije R, Rubin LJ: Efficacy and safety of chronic subcutaneous infusion of UT-15 in pulmonary arterial hypertension [asbtract]. Circulation 2000, 102(suppl): S100.Google Scholar
  24. Hoeper MM, Schwarze M, Ehlerding S, Adler-Schuermeyer A, Spiekerkoetter E, Niedermeyer J, Hamm M, Fabel H: Long-term treatment of primary pulmonary hypertension with aerosolized iloprost, a prostacyclin analogue. N Engl J Med 2000, 342: 1866-1870. 10.1056/NEJM200006223422503View ArticlePubMedGoogle Scholar
  25. Vizza CD, Naeije R, Sciomer S, Morelli S, Lavalle C, Di Marzio P, Padovani D, Badagliacca R, Vestri R, Fedele F: Long-term treatment of pulmonary arterial hypertension with beraprost, an oral prostacyclin analogue. Heart 2001, in press.Google Scholar
  26. Channick R, Badesch DB, Tapson VF, Simonneau G, Robbins I, Frost A, Roux S, Rainisio M, Bodin F, Rubin LJ: Effects of the dual endothelin receptor antagonist bosentan in patients with pulmonary hypertension: a placebo-controlled study. J Heart Lung Transplant 2001, 20: 262-263. 10.1016/S1053-2498(00)00606-9View ArticlePubMedGoogle Scholar
  27. Snell GI, Salamonsen RF, Bergin P, Esmore DS, Khan S, Williams TJ: Inhaled nitric oxide as a bridge to heart-lung transplantation in a patient with end-stage pulmonary hypertension. Am J Respir Crit Care Med 1995, 151: 1263-1266.PubMedGoogle Scholar
  28. Brimioulle S, Lejeune P, Naeije R: Effects of hypoxic pulmonary vasoconstriction on gas exchange. J Appl Physiol 1996, 81: 1535-1543.PubMedGoogle Scholar
  29. Barberà JA, Roger N, Roca J, Rovira I, Higenbottam TW, Rodriguez-Roisin R: Worsening of pulmonary gas exchange with nitric oxide inhalation in chronic obstructive pulmonary disease. Lancet 1996, 347: 436-440. 10.1016/S0140-6736(96)90011-2View ArticlePubMedGoogle Scholar
  30. West JB: Ventilation-perfusion relationships. Am Rev Respir Dis 1977, 116: 919-943.PubMedGoogle Scholar


© BioMed Central Ltd 2001