Pulmonary hypertension in chronic lung disease and hypoxia

Abstract

Pulmonary hypertension (PH) frequently complicates the course of patients with various forms of chronic lung disease (CLD). CLD-associated PH (CLD-PH) is invariably associated with reduced functional ability, impaired quality of life, greater oxygen requirements and an increased risk of mortality. The aetiology of CLD-PH is complex and multifactorial, with differences in the pathogenic sequelae between the diverse forms of CLD. Haemodynamic evaluation of PH severity should be contextualised within the extent of the underlying lung disease, which is best gauged through a combination of physiological and imaging assessment. Who, when, if and how to screen for PH will be addressed in this article, as will the current state of knowledge with regard to the role of treatment with pulmonary vasoactive agents. Although such therapy cannot be endorsed given the current state of findings, future studies in this area are strongly encouraged.

FIGURE 1

Evaluation of pulmonary hypertension (PH) in chronic lung disease (CLD). FEV₁: forced expiratory volume in 1 s; FVC: forced vital capacity; CT: computed tomography; PAH: pulmonary arterial hypertension; RCT: randomised controlled trial; D_LCO: diffusing capacity of the lung for carbon monoxide; K_CO: transfer coefficient of the lung for carbon monoxide. ^#: suggestive findings include: 1) symptoms and signs (dyspnoea out of proportion, loud P2, signs of right heart failure, right axis deviation on ECG, elevated natriuretic peptide levels); 2) pulmonary function test abnormalities (low D_LCO (e.g. <40% of predicted), elevated %FVC/%D_LCO ratio (low K_CO)); 3) exercise test findings (including decreased distance, decreased arterial oxygen saturation or increased Borg rating on 6-min walk test and decreased circulatory reserve, preserved ventilatory reserve on cardiopulmonary exercise testing); and 4) imaging findings (extent of LD, enlarged pulmonary artery segments, increased pulmonary artery/aorta diameter ratio >1 on CT). ^¶: signs supporting the diagnosis of PH include elevated systolic pulmonary arterial pressure and signs of right ventricular dysfunction. However, echocardiography measures are only suggestive and have limited accuracy in patients with CLD. ⁺: strongly consider referring the patient to a PH expert centre. ^§: expert centres should comprise multidisciplinary teams. Any decision for individualised treatment should follow a goal-orientated approach with predefined treatment targets, to be stopped if these targets are not met after a predefined time period.