Obstructive sleep apnea syndrome (OSAS) and chronic obstructive pulmonary disease (COPD)
represent two of the most prevalent respiratory disorders in clinical practice and their
coexistence is often described has "overlap syndrome" (OS) In patients with COPD, the
coexistence of OSA is associated with an increased risk of death from any cause, and
hospitalization because of COPD exacerbation. Treatment with continuous positive airway
pressure (CPAP) has been showed to be effective and associated with improved survival and
decreased hospitalizations. When CPAP became established treatment for overlap syndrome, a
multivariate analysis revealed that the hours of CPAP use were an independent predictor of
mortality. Furthermore, it has been showed that the survival benefit of CPAP favors
hypercapnic patients with overlap syndrome.
Regarding hypercapnic stable COPD patients, the best results with long-term non-invasive
positive pressure ventilation have been noted in studies using more intensive strategies of
ventilation, with higher inspiratory pressures and higher backup rates that improved or even
normalized daytime hypercapnia. In fact, survival benefits occurred when ventilation was
targeted to significantly reduce hypercapnia.
As for typical COPD, overlap syndrome patients might also benefit from optimal daytime
hypercapnia correction, which could be better achieved using bi-level ventilation instead of
CPAP, since it could not only maintain airway patency but also improve alveolar ventilation.
This study aims to compare CPAP therapy to bi-level ventilatory support in overlap syndrome
patients, not only for the efficacy to achieve hypercapnia reduction, but also regarding
acute disease exacerbations, symptoms and treatment compliance. Therefore, the authors
designed a randomized controlled trial with recruitment and power calculations based on the
applicant's own data.
After the diagnosis, patients will be randomized either for CPAP or BPAP treatment.
If CPAP is to be initiated, optimal pressure to maintain upper airway patency will be
determined. If there are continued obstructive respiratory events at 15 cm H2O of CPAP,
patients will cross-over to the BPAP study arm.
Regarding BPAP titration, patients will be treated with ventilators set in pressure support
spontaneous/timed mode, both inspiratory and expiratory positive airway pressures (IPAP and
EPAP) will be manually titrated. EPAP will ensure optimal pressure for maintaining upper
airway patency and IPAP will be defined according to patient tolerance and pressure support
necessary to achieve normal PaCO2 values or to reduce baseline PaCO2 by 20% or more;
Follow-up will be performed at 1, 6 and 12 months. Follow-up will include clinical evaluation
with physical examination and questionnaires (COPD Assessment test, Epworth Sleepiness Scale
and MRC dyspnea score), blood gas analysis, treatment adherence, AHI, nocturnal pulse
oximetry and exacerbations.
12-month follow-up will also include lung function test, 6-min walking test and nocturnal
capnography.