Erythrocytes Membrane Stability in COPD Patients in Long-Term Home Oxygen Therapy

The stability of erythrocytes is an inverse function of their osmotic fragility and can be measured by erythrocyte osmotic fragility test (FSO). The test of the FSO provides four parameters for the cell stability of measurement: dX, H50, Amax and Amin. Dx parameter expresses variation in salt concentration necessary to take intact erythrocytes (Amin) to a complete lysis state (Amax), with a 100% hemolysis. Increased dX values expresses greater stability of erythrocytes. The H50 parameter is related to the salt concentration required to produce 50% hemolysis. H50 larger values expresses lower stability of erythrocytes.

The analysis of the following parameters: hematological evaluation (complete blood count), serum levels of folic acid, cobalamin (vitamin B12), homocysteine, lipid profile, lactate dehydrogenase, serum iron, ferritin, transferrin capacity index, uric acid, glucose, albumin, reticulocytes, C-reactive protein (CRP), total bilirubin (TB), direct bilirubin (DB), indirect bilirubin (IB) and glycated hemoglobin (HbA1c).

Will be obtained: potential hydrogen (pH); arterial oxygen tension (PaO2), arterial carbon dioxide tension (PaCO2); and arterial oxyhemoglobin saturation (SaO2). The location and the puncture technique, sample handling and other technical considerations will be made according to the recommendation of specific guidelines of the Brazilian Thoracic Society.

British Medical Research Council developed this scale in order to predict future risk of mortality. The grades vary from 0 to 4, considering 0 better clinical condition and 4 worse health state.

The CAT consists of eight questions assessing cough, sputum, chest tightness, dyspnea, limitations in home activities, confidence in leaving home, sleep and energy. For each item, the patient chooses only one answer option, whose score ranges from zero to five. At the end of the test, the sum of the scores results in clinical impact of COPD, according to the stratification score of development study and validation of the CAT. The results vary according to the range of the scores, ranked as follows in relation to the clinical impact: 6-10 points, light; 11-20, moderate; 21-30, severe; and 31-40, very serious.

The CCQ is a self-administered questionnaire used routinely for clinical evaluation of COPD patients, but was also accepted as simple and a useful tool to be used in clinical trials evaluating response treatments and interventions. It consists of 10 items that must be answered based on the last seven days of the patient, and the results indicates their clinical condition based on an intensity scale in which zero represents the minimum possible limitation or absence of breathlessness, and six maximum limitation possible. The CCQ has three domains: symptoms, functional status and mental state.

The SF-36 is a generic tool often used as a measure of health-related quality of life, easy to administer and understand, is composed of 36 items covering eight domains: physical functioning, role limitations due to physical health, pain, general health perception, vitality, social functioning, role limitations due to emotional problems and mental health. It presents a score of 0 (zero) to 100, where zero corresponds to the worst general state of health and 100 corresponds to the best state of health.

The SGRQ is a 50-item questionnaire developed to measure health status (quality of life) in patients with diseases of airways obstruction. It is self-administered and consists of three domains: symptoms, activity and impact of disease. Each domain has a maximum possible score and the total is expressed as a percentage of that maximum, where values above 10% reflects changes on quality of life. A minimum change in score of 4 units was established as clinically relevant after patient and clinician testing.

AQ20 is a specific questionnaire for obstructive respiratory diseases, consisting of only 20 questions, derived from a longer questionnaire: Asthma Quality of Life Questionnaire (AQLQ). On its validation, it was compared to two other more complexes questionnaires (SGRQ and AQLQ) and showed good correlation with these instruments and clinical presentation of the patient. It is self-administered and its great advantage is the short time required to answer it, only 4 minutes, and simplified answers (yes, no or not applicable).

The spirometric measures pre and post inhalation of 400 µg of salbutamol via metered-dose inhalers will be held in the system Clinical Pulmonary Function-Spirometry. Airflow is measured using a Pitot tube (PreVentPneumotachTM), with flow and volume, and a 3L syringe calibration performed daily, considering the temperature, the humidity and the local barometric pressure. The volunteers completed at least three forced expiratory maneuvers and slow acceptable and at least two reproducible, according to the criteria of the Brazilian Thoracic Society.

The measurements of static lung volumes will be taken using plethysmography with the Elite Platinum DX system (MGC, Minnesota, USA). Consisting of the following elements: (A) a box with volume of 699 l, that becomes airtight by closing the door; (B) manometer to measure the pressure inside the box; (C) mouthpiece for breathing, consisting of flowmeter by pneumotachography; (D) manometer to measure the pressure in the mouth (equal to alveolar pressure in the absence of airflow and with an open glottis); and (E) of the airflow switch electrically controlled.

DLCO (Carbon Monoxide Diffusion) examine the amount of carbon monoxide (CO) that diffuses from the pulmonary capillaries through alveolar-capillary barrier. The system used for this evaluation will be Platinum Elite DX (MGC, Minnesota, USA), applying the modified Krogh technique (single breath).

The system used is the Cardio 2 (MGC, Minnesota, USA), which consists of a flow module, a gas analyzer and a computer with the software "Breeze Suite 7.2". This controls the ergometer and provides the graphical presentation and examination reports. The gas analyzer determines, breath by breath, the mixed expired fraction of respiratory gases. The analysis of the oxygen (O2) concentration is made using zirconium cell and analysis of the carbon dioxide (CO2) concentration is done in optical analyzer by absorption of infrared light. This module is calibrated before each test, using a reference sample gas (21% of O2 in nitrogen balance) and calibration mixture (12% of O2 and 5% of CO2 in nitrogen balance of the mixture).

The six-minute walk test (6MWT) is performed in accordance to the American Thoracic Society (ATS) guidelines. The equipment required for the test are: timer, pulse oximeter, heart rate monitor, sphygmomanometer and stethoscope. The tests will be conducted on a 30 meters enclosed corridor, free of obstacles, with chairs positioned at each of its ends, always by the same examiners who will be previously trained. Participants will be instructed to walk as fasten as possible during six minutes, being encouraged with standardized phrases every minute. If necessary, participants can rest, but the timer will remain on and they will be instructed to continue the test as soon as possible until the end of the sixth minute.