European respiratory review : an official journal of the European Respiratory Society
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Review
The need to move from 6-minute walk distance to outcome trials in pulmonary arterial hypertension.
Assessment of change in exercise capacity using the 6-min walk distance (6MWD) test has been the primary end-point in the majority of pulmonary arterial hypertension (PAH) clinical trials. The 6MWD has some advantages as an end-point in such studies. It is simple and inexpensive to perform, reproducible and validated. ⋯ While the 6MWD was initially considered to be a potentially reliable surrogate for disease progression in PAH, there is increasing evidence that this is not necessarily the case. Given this, there is a need to re-examine the role of 6MWD in PAH trials, and to evaluate the evidence supporting whether there is a need to move from 6MWD to more robust measures of clinical outcomes, such as morbidity and mortality. However, in the clinic the 6MWD test, alongside symptoms, haemodynamics and biomarkers, remains a useful tool in the assessment and management of PAH patients.
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Although the causal pathomechanisms contributing to remodelling of the pulmonary vascular bed in pulmonary arterial hypertension (PAH) are still unclear, several analogous features with carcinogenesis have led to the emergence of the cancer-like concept. The major similarities concern the altered crosstalk between cells from different tissue types, unexplained proliferation and survival of pulmonary smooth muscle and endothelial cells, the metabolic (glycolytic) shifts, and the association with the immune system. ⋯ It is clear that PAH is not a cancer, but this cancer-like concept has opened a new field of investigation and raises the possibility that antiproliferative and/or oncological drugs may exert therapeutic effects not only in cancer, but also in PAH. Such analogies and differences are discussed here.
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While obstructive sleep apnoea syndrome dominates discussion of the prevalence of sleep disordered breathing, nocturnal hypoventilation remains extremely prevalent in those with chronic ventilatory disorders and in the natural history of these conditions pre-dates the development of daytime ventilatory failure. In this review the clinical management of chronic hypoventilation in neuromuscular disease will be considered and then compared with that in obesity hypoventilation syndrome. In simple terms these conditions illustrate the polar opposite ends of the spectrum, as in neuromuscular disease the reduced capacity of the respiratory system is unable to withstand a normal respiratory load, and in obesity hypoventilation syndrome the normal capacity of the respiratory system is unable to tolerate a substantially increased ventilatory load.
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Interstitial lung disease (ILD) can occur in any of the connective tissue diseases (CTD) with varying frequency and severity, and an overall long-term prognosis that is less severe than that of idiopathic pulmonary fibrosis (IPF). Because ILD may be the presenting manifestation of CTD and/or the dominant manifestation of CTD, clinical extra-thoracic manifestations should be systematically considered in the diagnostic approach of ILD. When present, autoantibodies strongly contribute to the recognition and classification of the CTD. ⋯ Although it remains to be determined which combination of symptoms and serologic tests best identify the subset of patients with clinically relevant CTD features, available evidence suggests that such patients may have distinct clinical and imaging presentation and may portend a distinct clinical course. However, autoantibodies alone when present in IPF patients do not seem to impact prognosis or management. Referral to a rheumatologist and multidisciplinary discussion may contribute to management of patients with undifferentiated CTD.
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Idiopathic pulmonary fibrosis (IPF) is marked by a very disappointing survival rate and still represents a clinical dilemma. According to the current pathogenic hypothesis, chronic damage of the alveolar epithelium is followed by abnormal tissue repair and impairment of the alveolar structure. This process is driven by pathogenic events very similar to cancer, including epigenetic and genetic changes, altered response to regulatory signals, abnormal expression of microRNAs and activation of specific signalling pathways. ⋯ Viewing IPF as a cancer-like disease may satisfy the need for a better understanding of the pathogenesis of IPF by exploiting the large amount of knowledge that cancer biology evokes. The recognition of common pathogenic pathways between the two diseases may stimulate new clinical trials with cancer drugs, different drug combinations and different lines of drugs, as already experimented in oncology. Moreover, the concept of IPF as a cancer-like disorder may improve the attention given to this dreadful disease on a public, political and healthcare level.