*1.3.1 Body mass index (BMI)*

Body mass index (BMI) should be mounted on a wall using standard hospital calibration scales, because these parameters are very useful and fruitful in respiratory treatment as an indicator of health status. BMI is calculated as body mass (kg) divided by squared body height (m<sup>2</sup> ). However, this mostly applies to patients with severe COPD where an increasing BMI is linearly associated with better survival, while in patients with mild to moderate COPD the lowest mortality risk occurs in normal to overweight or weight loss in these patients. The World Health Organization criteria were used to classify the subjects as low-weight (BMI < 18.5), eutrophic (18.5 < BMI ≤ 24.99), overweight (25 ≤ BMI ≤ 29.99) or obese (BMI ≥ 30.00) [19]**.** This index and division for respiratory patients can also be cited and so for all population recognized. The biggest problem with BMI is that when patients with chronic respiratory disease have a normal weight, they are unable to recognize the percentage of the muscles of this patient, which is the main cause of her movement and activity, and in this situation, we need to use more precise equipment the body composition by BIA (Bioelectrical Impedance Analysis), including the percentage of muscle, fat, bone, lean mass, hole body mass, is more accurately measured, and this can be useful in a more accurate diagnosis of sarcopenia in these patients [20]**.**
