Prevalence and diagnosis of severe pulmonary hypertension in patients with chronic obstructive pulmonary disease

How to integrate multiple comorbidities in guideline development: article 10 in Integrating and coordinating efforts in COPD guideline development. An official ATS/ERS workshop report

BACKGROUND

Professional societies, like many other organizations around the world, have recognized the need to use more rigorous processes to ensure that health care recommendations are informed by the best available research evidence. This is the 10th of a series of 14 articles that were prepared to advise guideline developers in respiratory and other diseases. This article deals with how multiple comorbidities (co-existing chronic conditions) may be more effectively integrated into guidelines.

METHODS

In this review we addressed the following topics and questions using chronic obstructive pulmonary disease (COPD) as an example. (1) How important are multiple comorbidities for guidelines? (2) How have other organizations involved in the development of guidelines for single chronic disease approached the problem of multiple comorbidities? (3) What are the implications of multiple comorbidities for pharmacological treatment? (4) What are the potential changes induced by multiple comorbidities in guidelines? (5) What are the implications of considering a population of older patients with multiple comorbidities in designing clinical trials? Our conclusions are based on available evidence from the published literature, experience from guideline developers, and workshop discussions. We did not attempt to examine all Clinical Practice Guidelines (CPGs) and relevant literature. Instead, we selected CPGs generated by prominent professional organizations and relevant literature published in widely read journals, which are likely to have a high impact on clinical practice.

RESULTS AND CONCLUSIONS

A widening gap exists between the reality of the care of patients with multiple chronic conditions and the practical clinical recommendations driven by CPGs focused on a single disease, such as COPD. Guideline development panels should aim for multidisciplinary representation, especially when contemplating recommendations for individuals aged 65 years or older (who often have multiple comorbidities), and should evaluate the quality of evidence and the strength of recommendations targeted at this population. A priority area for research should be to assess the effect of multiple concomitant medications and assess how their combined effects are altered by genetic, physiological, disease-related, and other factors. One step that should be implemented immediately would be for existing COPD guidelines to add new sections to address the impact of multiple comorbidities on screening, diagnosis, prevention, and management recommendations. Research should focus on the possible interaction of multiple medications. Furthermore, genetic, physiological, disease-related, and other factors that may influence the directness (applicability) of the evidence for the target population in clinical practice guidelines should be examined.

Chronic obstructive pulmonary disease phenotype desaturator with hypoxic vascular remodelling and pulmonary hypertension obtained by cluster analysis

Significant heterogeneity of clinical presentation and disease progression exists within chronic obstructive pulmonary disease (COPD). This article discusses and refines the concept of desaturator phenotypes in COPD with pulmonary hypertension (PH) obtained by cluster analysis and presents a pattern of phenotypic markers that could be used as a framework for future diagnosis and research. Nocturnal oxygen desaturation results in sleep disturbances which predispose to nocturnal cardiac dysrhythmias, PH and possibly nocturnal death, particularly during acute exacerbations. We assume that in patients with COPD at least two factors play a role in PH: the severity of pulmonary impairment, and the severity of systemic nocturnal hypoxaemia due to reduced pulmonary functions. Establishing a common language for future research will facilitate our understanding and management of such a disease. This knowledge could lead to different pharmacological treatments and other interventions directed at specific phenotypic groups.

Exercise intolerance in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is associated with symptoms of dyspnea and fatigue, which contribute to exercise limitation. The origins and significance of dyspnea and fatigue in PAH are not completely understood. This has created uncertainly among healthcare professionals regarding acceptable levels of these symptoms, on exertion, for patients with PAH. Dysfunction of the right ventricle (RV) contributes to functional limitation and mortality in PAH; however, the role of the RV in eliciting dyspnea and fatigue has not been thoroughly examined. This paper explores the contribution of the RV and systemic and peripheral abnormalities to exercise limitation and symptoms in PAH. Further, it explores the relationship between exercise abnormalities and symptoms, the utility of the cardiopulmonary exercise test in identifying RV dysfunction, and offers suggestions for further research.

Use of cluster analysis to describe desaturator phenotypes in COPD: correlations between pulmonary function tests and nocturnal oxygen desaturation

BACKGROUND

Significant heterogeneity of clinical presentation and disease progression exists within chronic obstructive pulmonary disease (COPD). Although forced expiratory volume in 1 second (FEV(1)) inadequately describes this heterogeneity, a clear alternative has not emerged. This article discusses and refines the concept of phenotyping desaturators in COPD and shows a possible pattern which could be used as a framework for future research.

RECENT FINDINGS

COPD is a complex condition with pulmonary and extrapulmonary manifestations. We suggest that COPD phenotypes should be associated with clinically meaningful outcomes. The innovation of COPD phenotyping is defined as COPD desaturators. Sleep-related hypoxemia and hypercapnia are well recognized in COPD and the development of systemic inflammation during sleep. These sleep-related changes predispose to nocturnal cardiac arrhythmias, pulmonary hypertension, and possibly death, particularly during acute exacerbations.

CONCLUSION

A more focused definition makes possible a classification of patients into two distinct subgroups for both clinical and research purposes. Establishing a common language for future research will facilitate our understanding and management of such diseases. Even if different treatment strategies have different outcomes for these groups, we will have confirmation, or otherwise, of the clinical value of cluster analysis. This knowledge could lead to pharmacological treatment and other interventions directed to specific phenotypic groups.

The increase in pulmonary arterial pressure caused by hypoxia depends on iron status

Hypoxia is a major cause of pulmonary hypertension. Gene expression activated by the transcription factor hypoxia-inducible factor (HIF) is central to this process. The oxygen-sensing iron-dependent dioxygenase enzymes that regulate HIF are highly sensitive to varying iron availability. It is unknown whether iron similarly influences the pulmonary vasculature. This human physiology study aimed to determine whether varying iron availability affects pulmonary arterial pressure and the pulmonary vascular response to hypoxia, as predicted biochemically by the role of HIF. In a controlled crossover study, 16 healthy iron-replete volunteers undertook two separate protocols. The ‘Iron Protocol’ studied the effects of an intravenous infusion of iron on the pulmonary vascular response to 8 h of sustained hypoxia. The ‘Desferrioxamine Protocol’ examined the effects of an 8 h intravenous infusion of the iron chelator desferrioxamine on the pulmonary circulation. Primary outcome measures were pulmonary artery systolic pressure (PASP) and the PASP response to acute hypoxia (ΔPASP), assessed by Doppler echocardiography. In the Iron Protocol, infusion of iron abolished or greatly reduced both the elevation in baseline PASP (P < 0.001) and the enhanced sensitivity of the pulmonary vasculature to acute hypoxia (P = 0.002) that are induced by exposure to sustained hypoxia. In the Desferrioxamine Protocol, desferrioxamine significantly elevated both PASP (P < 0.001) and ΔPASP (P = 0.01). We conclude that iron availability modifies pulmonary arterial pressure and pulmonary vascular responses to hypoxia. Further research should investigate the potential for therapeutic manipulation of iron status in the management of hypoxic pulmonary hypertensive disease.