Nocturnal Hypoxemia, a Key Parameter in Overlap Syndrome

Abstract

The overlap syndrome (OS) is defined as a synergic relation between obstructive sleep apnea (OSA) and chronic obstructive pulmonary disease (COPD). Patients with overlap syndrome present the clinical features of each disorder to a greater or a lesser extend depending on the predominant disease. We assessed the main differences between patients with OS and patients with OSA and we highlight the importance of nocturnal hypoxemia on clinical status and management of the patients with overlap syndrome, in order to simplify OSA screening tests in patients with COPD. The study population included 62 selected patients divided in two groups: the first group � subjects diagnosed with OS and the second group - subjects with OSA, without the diagnostic of COPD. The majority of the patients were male, with a mean age of 55�9.84 years in the OSA group and 65.5�10.32 years in the OS group. The nocturnal hypoxemia was more important in the OS grup, with 276.83 minutes spent at a SpO2 below 90% versus 132.98 minutes in the OSA group. The mean AHI was 57.7�29.244 events/hour of sleep in the OS group and 50.7�26.01 events/hour of sleep in the OSA group. At the diagnosis, the mean daytime SpO2 was 90.9�3.59% in the OS group and 95.9�1.57 % in the OSA group. There were statistically significant differences between the two groups concerning age, AHI, Epworth Slepiness Scale, nocturnal desaturation, medium and minimum SpO2 during sleep, daytime SpO2 at the diagnosis and at 1-year follow-up, the presence of cardiovascular comorbidities such as pulmonary hypertension and heart failure. Our study showed that patients with COPD have OSA predictors that differ from those usually recognise in the general population. In OS patients, the most important parameter is the nocturnal hypoxemia. So, it is very useful that the clinicians be trained to include in the management of selected obese COPD patients, comprehensive sleep history, sleep hygiene and OSA screening because, in clinical practice, OSA is quite often underdiagnosed in these patients.