Endothelin-1 levels in interstitial lung disease patients during sleep

Untreated Obstructive Sleep Apnea in Interstitial Lung Disease and Impact on Interstitial Lung Disease Outcomes

Subjects with interstitial lung disease (ILD) often suffer from nocturnal cough, insomnia, and poor sleep quality. Subjects with ILD and obstructive sleep apnea (OSA) seem to have relatively mild symptoms from sleep fragmentation compared to subjects with only ILD. The overlap of ILD, OSA, and sleeping hypoxemia may be associated with poor outcome, even though there is no agreement on which sleep parameter is mostly associated with worsening ILD prognosis. Randomized controlled trials are needed to understand when positive airway pressure (PAP) treatment is required in subjects with ILD and OSA and the impact of PAP treatment on ILD progression.

The Association between Idiopathic Pulmonary Fibrosis and Obstructive Sleep Apnea: A Systematic Review and Meta-Analysis

The prevalence of obstructive sleep apnea (OSA) has greatly increased in recent years. Recent data suggest that severe and moderate forms of OSA affect between 6 and 17% of adults in the general population. Many papers are reporting the significantly increased prevalence of OSA in patients suffering from fibrotic diseases, including idiopathic pulmonary fibrosis (IPF). Therefore, we performed a systematic review and meta-analysis regarding the dependency between IPF and OSA. Due to the lack of papers focusing on IPF among OSA patients, we focused on the prevalence of OSA among IPF patients. In the search strategy, a total of 684 abstracts were identified, 496 after the removal of duplicates. After the screening of titles and abstracts, 31 studies were qualified for further full-text analysis for eligibility criteria. The final analysis was performed on 614 IPF patients from 18 studies, which met inclusion criteria. There were 469 (76.38%) IPF patients with OSA and 145 (23.62%) without. The mean age varied from 60.9 ± 8.1 up to 70.3 ± 7.9. The obtained prevalence was 76.4 (95% CI: 72.9–79.7) and 75.7 (95% CI: 70.1–80.9) for fixed and random effects, respectively. The median prevalence of OSA among non-IPF patients for all the ethnics groups included in this study was 16,4% (IQR: 3.4%–26.8%). The study provides strong evidence for the increased prevalence of OSA in IPF patients when comparing with the general OSA prevalence.

Nocturnal hypoxaemia in interstitial lung disease: a systematic review

BACKGROUND

Patients with interstitial lung disease (ILD) are at risk of developing nocturnal hypoxaemia due to ventilatory restriction and impaired gas exchange that worsen with supine posture and reduced ventilatory drive during sleep. This systematic review synthesised literature on the diagnostic evaluation, epidemiology, associations, management and prognosis of nocturnal hypoxaemia in ILD.

METHODS

Ovid MEDLINE, Embase and CENTRAL databases were searched for eligible studies. Meta-analyses with subgroup analyses were conducted, where possible.

RESULTS

Fifty-three studies were included (total participant number=2590). The most common definition for clinically significant nocturnal hypoxaemia was ≥10% of total sleep time with oxyhaemoglobin saturation <90%, with pooled prevalence of 37%. There were no significant differences in pooled prevalence according to ILD subtype and comorbid obstructive sleep apnoea status. Study heterogeneity precluded meta-analysis of associations and prognosis. Diffusing capacity for carbon monoxide (DLCO) and echocardiographic features for pulmonary hypertension were consistently associated with nocturnal hypoxaemia. There were inconsistent associations between nocturnal hypoxaemia with ILD subtype and severity. Multivariable analyses in most studies demonstrated significant associations of nocturnal hypoxaemia with survival. Two small short-term intervention studies demonstrated that supplemental oxygen of 1-3 L/min corrected nocturnal hypoxaemia, with improved heart rate control during in-laboratory observation and increased serum antioxidant levels after 1 month of therapy.

CONCLUSION

Nocturnal hypoxaemia is common, associated with DLCO impairment and markers suggestive of pulmonary hypertension, and a potential prognostic factor in patients in ILD. There is a need to establish a consensus definition of nocturnal hypoxaemia and evaluate long-term effects of nocturnal supplemental oxygen in ILD.

Prevalence and profile of sleep-disordered breathing and obstructive sleep apnea in patients with interstitial lung disease at the pulmonary medicine department of a tertiary care hospital in Mumbai

Background:

Sleep-disordered breathing (SDB), predominantly obstructive sleep apnea (OSA), is a frequent phenomenon in interstitial lung disease (ILD) and may be associated with significant morbidity and mortality.

Methodology:

A prospective, observational, hospital-based study was conducted in a tertiary care hospital after ethics committee permission. The study group consisted of 100 consecutive ILD patients diagnosed by a multidisciplinary diagnosis. They were evaluated for the prevalence of SDB with a polysomnography after a comprehensive history, detailed clinical examination, calculation of various pretest probability scores, and relevant prerequisite workup.

Results:

Out of the total 100 ILD patients, 44 were male (44%) and 56 were female (56%). SDB was present in 57 (57%) patients. Of these, 29 (29%) were found to have only nocturnal oxygen desaturation (NOD), while 28 (28%) had OSA. The 28 cases of OSA were distributed as 15 mild OSA (53.57%), 10 moderate OSA (35.71%), and 3 severe OSA (10.71%). The patients were divided into the following four groups: total study Group (A), patients with OSA (Group B), patients with NOD without OSA (Group C), and no SDB (Group D). The mean forced vital capacity values predicted in the four groups were 53.67%, 50%, 45.56%, and 57.87%, respectively. The mean body mass index in the four groups was 24.56, 27, 26.98, and 24.89 kg/m², respectively. The mean 6-min walk distance in the four groups was 280.7, 250, 256.65, and 311.4 m, respectively. The mean partial pressure of oxygen in the four groups was 65.65, 60, 62.10, and 75.66 mmHg, respectively. The mean apnea–hypopnea index in the study group was 2.98/h, 8.6/h with mild OSA, 21.69/h with moderate OSA, 48.78/h with severe OSA, 3.89/h in patients having NOD without OSA, and 2.54/h in patients with no SDB.

Conclusion:

SDB in ILD is associated with a significant impact on the cardinal determinants of functional capacity, lung function, and quality of life.

Under-recognised co-morbidities in idiopathic pulmonary fibrosis: A review

Co-morbidities in idiopathic pulmonary fibrosis are common. These co-morbidities include obstructive sleep apnoea, gastro-oesophageal reflux disease, pulmonary hypertension and depression. The presence of co-morbidities among patients with idiopathic pulmonary fibrosis contributes to worse quality of life, morbidity and mortality. Despite the high prevalence of certain co-morbidities in idiopathic pulmonary fibrosis, the optimal screening and management of many of these conditions remains unclear. The impact of co-morbidities on this patient population is becoming more apparent. Their relevance will only increase as significant effort is being made to develop novel therapeutics that will alter the disease trajectory of patients with idiopathic pulmonary fibrosis. The purpose of this review is to focus on the epidemiology, pathophysiology, diagnosis and management of select co-morbidities, including obstructive sleep apnoea, gastro-oesophageal reflux disease, pulmonary hypertension and depression, in idiopathic pulmonary fibrosis.

Sleep and respiratory sleep disorders in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is an interstitial lung disease (ILD) characterized by inflammation and progressive scarring of the lung parenchyma. IPF profoundly affects the quality of life (QoL) and fatigue is a frequently disabling symptom. The cause of fatigue is not well understood but patients with IPF often report extremely poor sleep quality and sleep-related breathing disorders (SRBD) that correlate with QoL. IPF patients present alterations in sleep architecture, including decreased sleep efficiency, slow wave sleep and rapid eye movement (REM) sleep, and increased sleep fragmentation. Moreover, sleep related hypoventilation during the vulnerable REM sleep period and obstructive sleep apnea-hypopnea syndrome (OSAHS) are frequent, but remain usually underdiagnosed. These SRBD in IPF are associated with alterations of the sleep structure, reduction of QoL and increased risk of mortality. In the absence of an effective therapy for IPF, optimizing the QoL could become the primary therapeutic goal. In this perspective the diagnosis and treatment of SRBD could significantly improve the QoL of IPF patients.

Sleep disordered breathing in interstitial lung disease: A review

Patients with interstitial lung disease commonly exhibit abnormal sleep architecture and increased sleep fragmentation on polysomnography. Fatigue is a frequent complaint, and it is likely that poor sleep quality is a significant contributor. A number of studies have shown that sleep disordered breathing is prevalent in this population, particularly in the idiopathic pulmonary fibrosis subgroup. The factors that predispose these patients to obstructive sleep apnoea are not well understood, however it is believed that reduced caudal traction on the upper airway can enhance collapsibility. Ventilatory control system instability may also be an important factor, particularly in those with increased chemo-responsiveness, and in hypoxic conditions. Transient, repetitive nocturnal oxygen desaturation is frequently observed in interstitial lung disease, both with and without associated obstructive apnoeas. There is increasing evidence that sleep-desaturation is associated with increased mortality, and may be important in the pathogenesis of pulmonary hypertension in this population.

Sleep oxygen desaturation predicts survival in idiopathic pulmonary fibrosis

BACKGROUND

Recent studies suggest poor sleep quality in patients with idiopathic pulmonary fibrosis (IPF). However, so far, the impact of IPF-related sleep breathing disorders (SBDs) on survival has not been extensively studied.

METHODS

In a cohort of 31 (24 males) treatment-naïve, newly diagnosed consecutive IPF patients, we prospectively investigated the relationship of SBD parameters such as apnea-hypopnea index (AHI), maximal difference in oxygen saturation between wakefulness and sleep (maxdiff SpO2), and lowest sleep oxygen saturation (lowest SpO2) with clinical (survival, dyspnea, daytime sleepiness), pulmonary function, submaximal (6-min walk test [6MWT]) and maximal exercise variables (cardiopulmonary exercise test [CPET]), and right ventricular systolic pressure (RVSP).

RESULTS

Sleep oxygen desaturation exceeded significantly that of maximal exercise (p < 0.001). Maxdiff SpO2 was inversely related to survival, DLCO%, and SpO2 after 6MWT, and directly with dyspnea, AHI, and RVSP. The lowest SpO2 was directly related to survival and to functional (TLC%, DLCO%) as well as submaximal and maximal exercise variables (6MWT distance, SpO2 after 6MWT, peak oxygen consumption/kg, SpO2 at peak exercise), while an inverse association with dyspnea score, AHI, and RVSP was observed.

CONCLUSIONS

Our findings provide evidence that intermittent sleep oxygen desaturation significantly exceeds that of maximal exercise and is associated with survival in IPF patients. Furthermore, they imply the existence of a link between lung damage and apnea events resulting to the induction and severity of intermittent sleep oxygen desaturation that aggravate pulmonary arterial hypertension and influence IPF survival.

Plasma endothelin-1 and vascular endothelial growth factor levels and their relationship to hemodynamics in idiopathic pulmonary fibrosis

BACKGROUND

Pulmonary hypertension (PH) is associated with a poor prognosis in idiopathic pulmonary fibrosis (IPF). Endothelin-1 (ET-1) and vascular endothelial growth factor (VEGF) are important in both fibrosis and vascular remodeling.

OBJECTIVES

We sought to determine the relationship between ET-1 and VEGF levels and hemodynamics in patients with IPF. We hypothesized that higher levels of ET-1 and VEGF would be associated with higher pulmonary artery pressures (PAP) and pulmonary vascular resistance (PVR) in patients with IPF.

METHODS

We performed a cross-sectional analysis of 52 adults with IPF enrolled in a prospective cohort with available clinical data, platelet-free plasma, and hemodynamics. ET-1 and VEGF levels were measured via immunoassay. The associations of ET-1 and VEGF with PAP and PVR were examined using generalized additive models adjusted for age, gender, race/ethnicity, and forced vital capacity (% predicted).

RESULTS

Sixteen of 52 (30.8%) had PH (mean PAP ≥25 mm Hg). After multivariable adjustment, higher ET-1 levels were significantly associated with higher systolic (p = 0.01), diastolic (p = 0.02), and mean (p = 0.01) PAP and possibly higher PVR (p = 0.09). There were no significant associations between VEGF levels and hemodynamics.

CONCLUSIONS

Higher levels of ET-1 were associated with higher PAP and possibly higher PVR in participants with IPF. In a subgroup of patients, ET-1 may be a contributor to pulmonary vascular disease burden in IPF.

Pulmonary hypertension in idiopathic pulmonary fibrosis: a review

Idiopathic pulmonary fibrosis (IPF) is a progressive diffuse parenchymal disease with a poor prognosis. Pulmonary hypertension (PH) often complicates the course of IPF and may even be found in patients with preserved lung function. Possible pathogenetic mechanisms of PH in IPF include vascular destruction, pulmonary hypoxic vasoconstriction and vascular remodeling due to overexpression of cytokines and growth factors. PH in IPF patients is associated with decreased exercise capacity and a worse prognosis. Due to its prognostic significance, it seems important to investigate for PH in these patients. As the symptoms of PH in IPF are nonspecific, the development of PH in a patient with known IPF can be easily overlooked. Noninvasive methods provide clues for the diagnosis, but their sensitivity is limited. Doppler echocardiography is a useful tool for the detection of PH which also provides additional information regarding associated cardiac abnormalities. However, right heart catheterization remains the gold standard diagnostic test. Therapeutic options for PH in IPF are limited. Long-term oxygen administration for the correction of hypoxemia should be recommended. The availability of new pharmacological agents in the treatment of PH has raised the possibility of therapy in patients with IPF and associated PH. Whether these PH-targeted therapies may be of benefit in this patient group, in terms of improving functional outcomes and survival, remains uncertain.

Improvement of bleomycin-induced pulmonary hypertension and pulmonary fibrosis by the endothelin receptor antagonist Bosentan

RATIONALE

There is evidence that endothelin plays a key role in the development of pulmonary hypertension (PH) in pulmonary fibrosis (PF). However, the functional consequence of the unselective endothelin receptor antagonist Bosentan in PH and PF has not yet been studied. Therefore, we investigated the effects of Bosentan on the development of PH in the model of Bleomycin-induced PF in rats.

METHODS

Adult male Wistar rats were randomly assigned to the following groups: untreated animals (controls), Bleomycin-induced PF (Bleomycin) and Bleomycin-induced PF treated with Bosentan (Bleomycin+Bosentan). Exercise capacity was evaluated by treadmill exercise testing. PH was assessed by right ventricular systolic pressure (RVSP) and right ventricular hypertrophy. For quantification of PF the hydroxyproline content in lung tissue (HPC) was measured.

RESULTS

Compared to controls, animals with Bleomycin-induced PF showed a significant reduction in exercise capacity (44% vs. 100%), significantly higher RVSP (65 mmHg vs. 23 mmHg), significantly more right ventricular hypertrophy (0.55 vs. 0.24) and significantly higher HPC (60.5 vs. 14.8). Bosentan treatment in animals with Bleomycin-induced PF resulted in significantly greater exercise capacity (98% vs. 44%) and a trend towards lower RVSP (52 mmHg vs. 65 mmHg), significantly less right ventricular hypertrophy (0.34 vs. 0.55) and significantly lower HPC (16.7 vs. 60.5) compared to untreated Bleomycin-induced PF.

CONCLUSION

Application of Bosentan in Bleomycin rats resulted in significantly higher exercise capacity as a result of improvements in PH and PF.

Vaso-active therapy can improve 6-min walk distance in patients with pulmonary hypertension and fibrotic interstitial lung disease

BACKGROUND

Dyspnea and functional limitation in interstitial lung diseases (ILD) are not always adequately explained by the degree of compromise in pulmonary function alone. Pulmonary hypertension (PH) is felt to be a major contributor to morbidity and mortality in these patients. It is not clear whether treatment with newer vaso-active agents benefits patients with PH in the setting of moderate or severe ILD.

METHODS

Medical records of patients followed at our institution between July 2001 and June 2005 were reviewed to identify patients with moderate or severe fibrotic ILD and PH. Data regarding demographics, hemodynamics, and clinical characteristics at baseline and during follow-up were collected.

RESULTS

We identified 19 patients who met our inclusion criteria and in whom vaso-active therapy [epoprostenol (N=10), bosentan (N=9)] was initiated. Most patients [(15/19(79%)] showed an initial positive response to therapy and improved their 6-min walk distance (6MWD) by >50m (responders) and 12/15 (80%) improved by at least 1 WHO functional class. At 1-year follow-up, 7 of 15 (47%) 'responders' had deteriorated significantly. None of the patients died during 1 year of follow-up.

CONCLUSIONS

Epoprostenol and bosentan produced short-term functional benefit in our patients with PH and moderate or severe restrictive ILD. The generalizability of these results awaits the results of larger, prospective, randomized trials in such patients.

Loss of the aryl hydrocarbon receptor induces hypoxemia, endothelin-1, and systemic hypertension at modest altitude

The aryl hydrocarbon receptor (AHR) is a basic helix-loop-helix Per-Arnt-Sim transcription factor that mediates induction of metabolic enzymes and toxicity of certain environmental pollutants. Although AHR knockout (KO) mice develop cardiac hypertrophy, conflicting reports associate this pathology with hypotension or endothelin (ET)-1-dependent hypertension. Because hypertension occurred at modest altitude, we tested the hypothesis that loss of AHR increases the sensitivity to hypoxia-induced ET-1, contributing to systemic hypertension. We found that AHR KO mice were hypertensive at modest altitude (1632 m) but hypotensive at low altitude (225 m). When AHR KO mice residing at 1632 m were exposed to the partial pressure of inspired oxygen (PIO(2)) at sea level for 11 days, blood pressure declined to levels measured at 225 m. Although plasma ET-1 in AHR KO mice was significantly elevated at 1632 m and decreased at 225 m and sea level PIO(2), pulmonary prepro-ET-1 mRNA was significantly reduced at 1632 m and decreased further at 225 m and sea level PIO(2). Blood gas analysis revealed that AHR KO mice were hypoxemic, hypercapnic, and acidotic at 1632 m, values that were attenuated and normalized after 24 hours and 11 days under sea level PIO(2), respectively. Lastly, AHR inactivation in endothelial cells by small interfering RNA significantly reduced basal prepro-ET-1 mRNA but did not alter hypoxia-induced expression. Our studies establish the AHR KO mouse as a model in which modest decreases in PIO(2) lead to hypoxemia, increased plasma ET-1, and systemic hypertension without increased pulmonary prepro-ET-1 mRNA expression.

Pulmonary hypertension associated with chronic respiratory disease

Pulmonary hypertension (PH) has long been recognized as a complication of chronic respiratory disease. Recent studies have highlighted the adverse impact PH has on the clinical course of these conditions and have cast doubt on the role of hypoxia in their pathogenesis. Clinicians should carefully consider the possibility of PH during the diagnostic evaluation of chronic respiratory disorders. The usefulness of pharmacologic therapy directed toward PH remains to be determined.

Pulmonary hypertension in patients with interstitial lung diseases

Pulmonary hypertension (PH) in patients with interstitial lung diseases (ILDs) is not well recognized and can occur in the absence of advanced pulmonary dysfunction or hypoxemia. To address this topic, we identified relevant studies in the English language by searching the MEDLINE database (1966 to November 2006) and by individually reviewing the references of identified articles. Connective tissue disease-related ILD, sarcoidosis, idiopathic pulmonary fibrosis, and pulmonary Langerhans cell histiocytosis are the ILDs most commonly associated with PH. Pulmonary hypertension is an underrecognized complication in patients with ILDs and can adversely affect symptoms, functional capacity, and survival. Pulmonary hypertension can arise in patients with ILDs through various mechanisms, Including pulmonary vasoconstriction and vascular remodeling, vascular destruction associated with progressive parenchymal fibrosis, vascular inflammation, perivascular fibrosis, and thrombotic angiopathy. Diagnosis of PH in these patients requires a high index of suspicion because the clinical presentation tends to be nonspecific, particularly in the presence of an underlying parenchymal lung disease. Doppler echocardiography is an essential tool in the evaluation of suspected PH and allows ready recognition of cardiac causes. Right heart catheterization is needed to confirm the presence of PH, assess its severity, and guide therapy. Management of PH in patients with ILDs is guided by identification of the underlying mechanism and the clinical context. An increasing number of available pharmacologic agents in the treatment of PH allow possible treatment of PH in some patients with ILDs. Whether specific treatment of PH in these patients favorably alters functional capacity or outcome needs to be determined.

Pulmonary hypertension in interstitial lung disease

PURPOSE OF REVIEW

Exercise impairment and pulmonary hypertension are common features of interstitial lung disease. Antifibrotic therapies for interstitial lung disease remain unproved; therefore, some interest has been focused on treating the pulmonary vascular impairment these diseases.

RECENT FINDINGS

Patients with pulmonary hypertension secondary to idiopathic pulmonary fibrosis may have normal resting pulmonary artery pressure, but it often rises with exercise. Exercise impairment in idiopathic pulmonary fibrosis has a strong correlation with the degree of pulmonary artery pressure elevation, and hypoxemia, a hallmark of pulmonary hypertension, strongly correlates with survival.

SUMMARY

Small case series have shown that some patients improve on receiving therapy for pulmonary hypertension secondary to interstitial lung disease. These findings suggest that larger treatment trials for medications targeting pulmonary hypertension in interstitial lung disease are warranted.