Describe the four classes of respiratory impairment.



  • Class 1- This individual will have a zero percent impairment rating upon examination. Although the person’s roentgenogram will appear negative, there may be evidence of mild or inactive chest disease. The patient might have difficulty breathing when doing heavy activity of an unusual nature. This person will generally not have any severe functional limitations.
  •  Class 2- This individual will generally have an impairment rating of 10 to 20 percent. Dyspnea does not occur when the person is at rest and generally rarely occurs when the person is accomplishing his or her general activities of daily living. The person may have difficulties with heavier exertion, prolonged walking, and prolonged physical activity, they can keep pace with individuals their own age when the activity takes place on level ground. However, the individual with a Class 2 impairment will have difficulty keeping up with persons in the same age group and body build on hills or uneven terrain. Stair climbing generally produces symptoms of respiratory distress. The individual with this level of impairment should avoid dust, odors, fumes, poor ventilation, and irritating inhalants.
  •  Class 3- An individual with a Class 3 impairment will generally have an impairment rating of 25 to 35 percent and will have abnormalities in lung structure on their roentgenogram. The person may experience dyspnea while performing ordinary activities of daily living. These individuals can generally walk up to one mile without symptoms, but are generally unable to keep pace with individuals of their own age and body type. They may experience significant psychological distress. Vocational handicaps include: avoidance of walking two or more blocks, lifting no more than 10-20 pounds, and occasionally climbing one flight of stairs.
  • Class 4- An individual with a Class 4 diagnosis will have a respiratory impairment rating of 50 to 70 percent. These individuals will likely experience labored or difficulty breathing when they climb one flight of stairs, walk 100 yards on an even surface, and even on limited exertion. The individual with a Class 4 diagnosis will likely experience dyspnea when at rest. An individual with this level of respiratory impairment may prove to be a poor candidate for vocational rehabilitation. Vocational restrictions include: avoid walking 25 yards on occasion, avoid stair climbing or lifting over several pounds, avoid activities of daily living, avoid postural positions that increase symptoms, and avoid extremes of temperature.


Deutsch. “Evaluation of Respiratory Impairment.” In P. Deutsch and H. Sawyer (Ed.) A Guide to Rehabilitation. White Plains, NY: AHAB Press.

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