The Cardiovascular Consequences of Sleep Apnea Plus COPD (Overlap Syndrome)

Summary

Major progress has been made in the area of cardiovascular disease, but we believe that further progress will involve mechanistically addressing underlying respiratory causes including chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (OSA). The most common cause of death in COPD is cardiovascular, although mechanisms are unknown. OSA has been associated with major neurocognitive and cardiovascular sequelae, the latter likely a function of autonomic nervous system abnormalities, oxidative stress, inflammation, and other pathways. Recent data suggest that individuals with OVS die preferentially of cardiovascular disease compared to OSA or COPD alone, although mechanisms are again unclear. The combination of OSA and COPD may lead to profound hypoxemia. Individuals with COPD can develop pulmonary hypertension via disturbances in gas exchange and parenchymal injury leading to loss of pulmonary vasculature. OSA has been associated with mild to moderate pulmonary hypertension, but the situation may be worse if combined with parenchymal lung disease. The biological response to sustained hypoxemia has been carefully studied as has the topic of intermittent hypoxemia; however, to our knowledge, very little research has occurred regarding the combination of sustained plus intermittent hypoxia as seen in OVS. For example, we do not really know whether individuals with OVS develop coronary disease, right or left heart failure, dysrhythmias or some combination of abnormalities predisposing them to cardiovascular death. Thus, design of interventional studies is challenging as causal pathways are poorly understood despite our considerable preliminary data addressing these issues. The purpose of this study is to examine vascular mechanisms in individuals with COPD/OSA overlap syndrome (OVS) compared with matched individuals with obstructive sleep apnea (OSA) alone or chronic obstructive pulmonary disease (COPD) alone and to perform a phase II pilot mechanistic clinical trial in OVS to examine the effect size of nocturnal bi-level positive airway pressure (PAP) vs. nocturnal oxygen therapy in cardiovascular outcomes.

Description

Eligibility

Age range

40–79 years

Sex

All

Healthy volunteers

No

Interventions

• Device
  bi-level positive pressure non invasive ventilation

  Participants randomized to the bi-level arm will be provided with an auto bi-level device that automatically delivers the required pressure. The settings in the auto bi-level will be minimum EPAP of 4 cmH2O, maximum IPAP of 24 cmH2O, and a range of pressure support between 6-10 cmH2O. For those participants who have been randomized to the bi-level group but have not successfully acclimated to the device with the automatic bi-level settings, we will conduct an in-lab titration of the bi-level therapy during the optional Overnight visit 2.

• Drug
  Oxygen gas

  The dose of nocturnal oxygen in all participants in the oxygen therapy arm will be 2 liters/minute. Patients with daytime hypoxemia, measured as sustained desaturations below 89% during wake time and/or arterial blood PO2 ≤ 55 mmHg, will be excluded from this study (as specified in the exclusion criteria) for ethical reasons since withholding oxygen in hypoxemic patients would be at odds with standard of care.

Location