Pulmonary Hypertension Associated with Chronic Respiratory Disease
Section snippets
Chronic obstructive pulmonary disease
The exact prevalence of PH in chronic obstructive pulmonary disease (COPD) is unclear, but it is more common among patients who have severe airflow limitation. In a recent large French series of patients referred for lung volume reduction surgery or transplantation with a mean force expiratory volume in 1 second (FEV1) of 24% predicted, half had a mean pulmonary artery pressure (MPAP) greater than 25 mm Hg [8]. On average, PH is mild in severity (25–35 mm Hg MPAP) with preserved right
Connective tissue diseases
Interstitial lung disease is the most common pulmonary manifestation of scleroderma (systemic sclerosis). The impact of concomitant PH on the course of interstitial lung disease in systemic sclerosis is becoming increasingly appreciated. A typical pattern is that of mild dyspnea in the setting of stable or slowly declining pulmonary function tests over many years. An abrupt worsening of symptoms, hypoxemia, and DLCO heralds the onset of PH. A recent review of 619 patients by the Johns Hopkins
Sleep-disordered breathing
Episodic and potentially dramatic increases in pulmonary artery pressure accompany apneic episodes in obstructive sleep apnea (OSA), particularly during rapid eye movement sleep [44]. This finding has been largely attributed to hypoxia, although other factors related to large swings in intrathoracic pressure may also be important, such as increased venous return and left ventricular afterload [45]. In contrast to certain animal models, however, intermittent hypoxia does not generally produce PH
Diagnostic evaluation of pulmonary hypertension in respiratory disease
Clinicians traditionally have not aggressively pursued the diagnosis of PH in chronic respiratory diseases, largely because of the lack of specific therapy. However, the increasing array of drugs for pulmonary arterial hypertension may potentially be useful in treating these conditions. A diagnostic evaluation for PH is also clinically important to (1) identify other treatable causes for PH (eg, left heart disease, chronic thromboembolic disease), (2) help delineate the basis for symptoms, (3)
Oxygen therapy and positive pressure ventilation
Correction of hypoxemia with long-term oxygen therapy clearly improves survival in COPD, but only modest, if any, improvements in pulmonary hemodynamics occur. Long-term oxygen therapy prevents progression of PH in COPD [65], [66]. Although no data support the use of long-term oxygen therapy in other hypoxemic lung diseases [67], most clinicians prescribe it, particularly with complicating PH for which a Pao2 of less than 60 mm Hg is required for Medicare coverage, compared with less than 56 mm
Summary
PH is a common, although often overlooked, complication of chronic respiratory diseases. Although often mild and overshadowed by the underlying condition, PH and right ventricular dysfunction can dominate the clinical picture, particularly in certain interstitial lung diseases. A diagnosis of PH has important prognostic implications and helps delineate the basis for symptoms. Further research is needed to improve the diagnostic accuracy of noninvasive testing and to understand the pathogenesis
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