The evaluation of permanent disability and occupational invalidity is a complex process, particularly when assessing the impact of chronic conditions on an individual's functional capacity. In Colombia, Decree 917 of 1999 establishes the "Manual Único para la Calificación de la Invalidez" (Single Manual for Disability Rating), providing a standardized framework for medical professionals to determine the percentage of permanent partial disability or total invalidity. This comprehensive manual ensures consistency and objectivity in the assessment process, covering various bodily systems and their potential impairments. This article, Part I of II, delves specifically into Chapter IV of Decree 917, which is dedicated to the meticulous evaluation of the respiratory system. Understanding these guidelines is crucial for medical evaluators, legal professionals, and individuals seeking disability benefits, as it outlines the precise criteria and methodologies for quantifying re...