IJCS | Volume 32, Nº4, July/August 2019

345 Almeida et al. Cardiorespiratory fitness classification Int J Cardiovasc Sci. 2019;32(4):343-354 Original Article Figure 1 - Flow chart of patients’ recruitment. CPET: cardiopulmonary exercise testing; TBC: total blood count; SAH: systemic arterial hypertension (use of drugs with cardiovascular action); CAD: coronary artery disease; CHF: congestive heart failure; VHD: valvular heart disease; COPD: chronic obstructive pulmonary disease; W/o: without; Tech. probl.: technical problems. CPET n = 11,350 Excluded n = 4,448 Without TBC n = 407 Disease 4,041 Anemia n = 301 SAH n = 1,475 CAD n = 1,089 CHF n = 324 Vasculopathy n = 361 VHD n = 287 Asthma n = 204 Normal subjects n = 6,902 Excluded n = 334 W/o criteria for CPET - n = 311 Tech. Probl. n = 23 Study Sample n = 6,568 Male n = 3,320 Female n = 3,248 exercise/activity (time, regularity, frequency, duration and intensity), past household and occupational activities focusing on energy expenditure. All participants signed the informed consent form. The study was approved by the ethics committee of Hospital de Clínicas de Porto Alegre , approval number 13-0474). Cardiopulmonary exercise testing A CPET device (Metalyzer 3B; Cortex, Leipzig, Germany) combined with ErgoPC Elite (Micromed, Brasília, Brazil), was used with breath-by-breath measurements. All CPET procedures were performed in the same room, with environmental conditions monitored by an Oregon Scientific BAR 208 HGA advanced weather station - mean temperature of 24.47 o C, relative humidity of 61.33 and atmospheric pressure of 1009.25 kPa (757 mmHg). Ventilation was regularly calibrated using a 3L-syringe, to apply the correction factor for respiratory volume. Measurements of the oxygen fraction in the expiratory gas (FEO 2 ) were made through highly accurate (0.1 Vol.%), fast- response electrochemical cells, and the expired fraction carbon dioxide (FECO 2 ) was measured using a highly- sensitive, ND infrared gas analyzer. Calibration of gas analyzers was made weekly (or according to the software recommendations), using a known gas mixture of O 2 (12%) and CO 2 (4.99%) balanced with nitrogen. Ventilatory variables were immediately recorded, and the means were subsequently calculated every 10 seconds with electrocardiographic monitoring. All tests were performed using a treadmill ergometer (Centurion-200 Micromed, Brasilia, Brazil), by the same cardiologist, specialized in exercise testing from the Brazilian Society of Cardiology. A ramp protocol was used, adapted to each participant according to the medical history, biomechanical analysis and physician’s expertise, with a planned CPET duration of 8-12 minutes. The subjects were instructed about the test protocol and performed a symptom-limited exercise testing. A modified 10-point Borg scale and the respiratory quotient > 1.10 were used as criteria for maximal exercise. 21-24 Oxygen uptake Oxygen uptake was determined based on the agreement between the two specialists in CPET, both independent and blind to study. Test results were sent to the investigators, who identified the peak VO 2 point on the graph. Peak VO 2 was measured at the highest point reached during final stages of maximum effort, considering a sampling interval of two ten-second consecutive periods, and one-minute extrapolation for most participants. For this reason, the term VO 2peak was adopted throughout the article. 21,23,24 It is worth mentioning that most individuals reached the highest VO 2 value at the plateau of the curve, regardless of the increase in workload (VO 2 max). 22,24,25