47. For the purposes of this Division, the following functional respiratory classification is established:
(1) Class I: presence or absence of dyspnea. If dyspnea is present, it is attributable to non-respiratory causes;
(2) Class II: presence of dyspnea while walking briskly on flat ground or while climbing a slope;
(3) Class III: presence of dyspnea while walking on flat ground as compared to a person of the same age or while climbing stairs;
(4) Class IV: presence of dyspnea after a 100-metre walk on flat ground at the person’s own rhythm;
(5) Class V: presence of dyspnea while dressing, undressing or speaking.