Objectives: Investigate the acute NIV effects on CBF and cognitive functions in COPD patients. Methods: Nine non-hypercapnic stable COPD subjects (FEV1/FVC < lower limit of normal) and twelve healthy controls were enrolled. CBF (transcranial Doppler), cognitive functions, respiratory and cardiovascular response were tested at baseline, during and after non-invasive ventilation.

Nine COPD patients were screened from the Respiration Laboratory (RespLab) of Federal University of Ceará, and twelve sedentary controls from the general population were also assessed. All patients were under stable medical treatment at least two months, and COPD diagnosis was made according to GOLD guidelines. Patients were excluded if they had heart disease, arterial hypertension, other debilitating pulmonary or non-pulmonary diseases, depression, preexisting psychiatric or neurologic disorders, stroke, motor impairment, visual or hearing disabilities, mini-mental scale examination score below 20 points, and any disease that could influence the effectiveness of NIV application or the performance of cognitive tests. The control group consisted of healthy and nonsmoking volunteers.

After study enrollment, 15 days before the performance of the experimental protocol, patients performed neurocognitive tests (Digit Span Test, Digit Symbol-Coding, Corsi Block-tapping, Trail Making Test A and B and Stroop Test) and NIV adaptation. Pulmonary function (spirometry) was measured in all subjects after a thorough medical history and physical examination. Before initiating the protocol, patients were asked about discomfort related to NIV or any aspect of the experiment. CBF, capnometry, arterial blood gases (ABG) and neurocognitive tests were performed before, during and after NIV.

CBF was measured by transcranial Doppler by mean of LMCAFV immediately before NIV, during NIV at 5, 30 and 60 minutes and after NIV removal at 5 and 30 minutes. ABG were collected immediately before the experiment, after one hour of NIV breathing and 30 minutes after NIV discontinuation. Respiratory rate (RR), tidal volume (VT), oxygen saturation by pulse oximetry (SpO2), heart rate (HR), minute ventilation (VE) and mean systemic arterial blood pressure (MAP) were continuously measured by a multiparameter monitor (Dixtal DX-2010™, Dixtal, Manaus, Brazil) both on spontaneous respiration and NIV.

Subjects were tested in the morning and investigated while awake and at the supine position, throughout the experiment.

Inclusion Criteria:

• All patients were under stable medical treatment at least two months
• COPD diagnosis was made according to GOLD guidelines

Exclusion Criteria:

• heart disease, arterial hypertension, other debilitating pulmonary or non-pulmonary diseases, depression, preexisting psychiatric or neurologic disorders, stroke, motor impairment, visual or hearing disabilities, mini-mental scale examination score bellow 20 points, and any disease that could influence the effectiveness of NIV application or the performance of cognitive tests