Sedentary Work Exerting up to 10 pounds (4.5 kg) of force occasionally and/or a negligible amount of force frequently or constantly to lift, carry, push, pull, or otherwise move objects, including the human body. Sedentary work involves sitting most of the time, but may involve walking or standing for brief periods of time. Jobs are sedentary if walking and standing are required only occasionally and other sedentary criteria are met.

Light Work Exerting up to 20 pounds (9.1 kg) of force occasionally and/or up to 10 pounds (4.5 kg) of force frequently, and/or negligible amount of force constantly to move objects. Physical demand requirements are in excess of those for Sedentary Work. Light Work usually requires walking or standing to a significant degree. However, if the use of the arm and/or leg controls requires exertion of forces greater than that for Sedentary Work and the worker sits most the time, the job is rated Light Work.

Medium Work Exerting up to 50 (22.7 kg) pounds of force occasionally, and/or up to 25 pounds (11.3 kg) of force frequently, and/or up to 10 pounds (4.5 kg) of forces constantly to move objects.

Heavy Work Exerting up to 100 pounds (45.4 kg) of force occasionally, and/or up to 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Very Heavy Work Exerting in excess of 100 pounds (45.4 kg) of force occasionally, and/or in excess of 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Job Classification

In most duration tables, five job classifications are displayed. These job classifications are based on the amount of physical effort required to perform the work. The classifications correspond to the Strength Factor classifications described in the United States Department of Labor's Dictionary of Occupational Titles. The following definitions are quoted directly from that publication.

Sedentary Work Exerting up to 10 pounds (4.5 kg) of force occasionally and/or a negligible amount of force frequently or constantly to lift, carry, push, pull, or otherwise move objects, including the human body. Sedentary work involves sitting most of the time, but may involve walking or standing for brief periods of time. Jobs are sedentary if walking and standing are required only occasionally and other sedentary criteria are met.

Light Work Exerting up to 20 pounds (9.1 kg) of force occasionally and/or up to 10 pounds (4.5 kg) of force frequently, and/or negligible amount of force constantly to move objects. Physical demand requirements are in excess of those for Sedentary Work. Light Work usually requires walking or standing to a significant degree. However, if the use of the arm and/or leg controls requires exertion of forces greater than that for Sedentary Work and the worker sits most the time, the job is rated Light Work.

Medium Work Exerting up to 50 (22.7 kg) pounds of force occasionally, and/or up to 25 pounds (11.3 kg) of force frequently, and/or up to 10 pounds (4.5 kg) of forces constantly to move objects.

Heavy Work Exerting up to 100 pounds (45.4 kg) of force occasionally, and/or up to 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Very Heavy Work Exerting in excess of 100 pounds (45.4 kg) of force occasionally, and/or in excess of 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Hypersensitivity Pneumonitis


Related Terms

  • Air Conditioner Lung
  • Bird Fancier's Disease
  • Byssinosis
  • Cork Worker's Lung
  • Cotton Worker's Disease
  • Extrinsic Allergic Alveolitis
  • Farmer's Lung
  • Hot Tub Lung
  • Humidifier Lung
  • Industrial Bronchitis
  • Machine Operator's Lung
  • Mushroom Worker's Lung
  • Pigeon Breeder's Disease
  • Sugar Cane Disease (Bagassosis)
  • Ventilation Pneumonitis

Differential Diagnosis

Specialists

  • Allergist/Immunologist
  • Internal Medicine Physician
  • Preventive Medicine Specialist
  • Pulmonologist

Comorbid Conditions

Factors Influencing Duration

The type of treatment and the individual's response to it, as well as the individual's occupation and the availability of another job without the presence of the inhaled agent, will influence duration. Age, general state of health, physical condition, and nutritional status may influence the individual's ability to undergo treatment and recover. Permanent lung damage, such as scarring from long-term exposure, will also affect duration. Disability depends on whether or not the hypersensitivity pneumonitis is chronic and whether the individual can avoid the offending agent.

Medical Codes

ICD-9-CM:
495 - Allergic Alveolitis, Extrinsic
495.0 - Allergic Alveolitis, Extrinsic; Farmers Lung
495.1 - Allergic Alveolitis, Extrinsic; Bagassosis
495.2 - Allergic Alveolitis, Extrinsic; Bird-Fanciers Lung
495.3 - Allergic Alveolitis, Extrinsic; Suberosis; Cork-handlers Disease or Lung
495.4 - Allergic Alveolitis, Extrinsic; Malt Workers Lung; Alveolitis Due to Aspergillus Clavatus
495.5 - Allergic Alveolitis, Extrinsic; Mushroom Workers Lung
495.6 - Allergic Alveolitis, Extrinsic; Maple bark-strippers lung; Alveolitis Due to Cryptostroma Corticale
495.7 - Allergic Alveolitis, Extrinsic; "Ventilation" Pneumonitis
495.8 - Allergic Alveolitis, Extrinsic; Allergic Alveolitis and Pneumonitis, Other Specified
495.9 - Allergic Alveolitis, Extrinsic; Hypersensitivity Pneumonitis
506.9 - Respiratory Conditions due to Fumes or Vapors, Unspecified

Overview

Hypersensitivity pneumonitis is an immune reaction to antigens found on a variety of inhaled agents small enough to enter the terminal airways in the lungs (bronchioles and alveoli). This immune reaction or allergic response results in inflammation of the bronchial tree.

There are a number of substances that can cause hypersensitivity pneumonitis, including bacteria, molds, fungi, pollen, dust mites and other insects, animal dander (tiny scales from fur, feathers, or skin), and nonbiological substances such as chemicals. The most common type of hypersensitivity pneumonitis is related to exposure to pet birds (known as bird fancier's disease). Other examples of hypersensitivity pneumonitis result from exposure to mold spores in hay (known as farmer's lung disease), to protein particles found in pigeon droppings (known as pigeon breeder's disease), to mold growing in wet containers (known as sauna takers' disease), to moldy compost (known as mushroom worker's disease), and to moldy sugar cane (known as bagassosis), and to forced air ventilation systems or humidifiers (known as air conditioner lung or humidifier lung). The list of nonbiological substances (i.e., chemicals) that can cause hypersensitivity pneumonitis is virtually limitless. The disease is often occupational.

In acute cases, symptoms typically appear 4 to 12 hours after exposure and usually disappear within a few days after the individual avoids the agent that caused the reaction. Chronic hypersensitivity pneumonitis can develop after months or years of low-grade exposure to the offending substances, is more difficult to diagnose and treat, and can lead to pulmonary fibrosis. A very severe reaction can cause low blood oxygen (hypoxia) and respiratory failure.

Incidence and Prevalence: Resistance and susceptibility to infection vary with the types of exposure. The incidence of hypersensitivity pneumonitis among farmers ranges from 8 to 540 cases per 100,000 annually, whereas among pigeon breeders, the incidence ranges from 6,000 to 21,000 cases per 100,000 annually. In two specific clusters of cases, 52% of office workers in one office experienced hypersensitivity pneumonitis after exposure to an infected humidifier, and in another, 27% of workers at a molding plant for polyurethane foam parts experienced the same (Sharma).

The same source suggests that prevalence also varies by region, climate, and farming practices, ranging from 0.4% to 7% in farmers and 20 to 20,000 cases per 100,000 bird fanciers.

Source: Medical Disability Advisor



Causation and Known Risk Factors

Farmers (because of exposure to moldy hay and grain) and pigeon breeders and bird fanciers (because of exposure to serum proteins of the birds) are at the highest risk for hypersensitivity pneumonitis. Individuals who work in energy-efficient, sealed office buildings are also at risk, particularly if the building is new or recently remodeled.

In the case of allergy-based pneumonitis, risk depends on two things: the individual's unique allergic response to the offending agent (allergen), and the degree of exposure to and nature of the agent. Although many people may be exposed to an allergen, only a few will exhibit signs of disease.

Source: Medical Disability Advisor



Diagnosis

History: Hypersensitivity pneumonitis exists in two basic clinical forms: acute and chronic. Acute hypersensitivity pneumonitis is characterized by fever, chills, cough, difficulty in breathing (dyspnea), nausea, loss of appetite, muscle aches, fatigue, and malaise that typically occurs 4 to 8 hours after antigenic exposure. In chronic hypersensitivity pneumonitis, there are usually no systemic symptoms; rather, chronic and frequently progressive shortness of breath, along with cough on exertion, mark the symptom complex.

Physical exam: Typical findings in acute hypersensitivity pneumonitis include fever, mild-to-moderate respiratory distress, cough, and rales. In the chronic form, muscle wasting, weight loss, rapid respiration (tachypnea), and thickened/widened fingertips (clubbing) may be observed.

Tests: Blood tests, including a complete blood count (CBC) and examination for specific antigens, may be performed. Chest x-rays, pulmonary function studies, and/or aspiration of lung fluid for microscopic examination and culture should be done. Samples of lung tissue may be taken (biopsy) for examination for infectious organisms.

There is no single diagnostic test that can be used to establish an unequivocal diagnosis of hypersensitivity pneumonitis. Therefore, one must rely on a combination of history, radiography, serologic study, and exclusion of other possible causes. A history of previous episodes of acute hypersensitivity pneumonitis is of diagnostic value.

Source: Medical Disability Advisor



Treatment

The first step of treatment is to identify and remove the agent that is causing the problem. If that is not possible, the individual must leave the offending environment; measures to minimize antigen exposure usually result in regression of disease. Some individuals may require emergency treatment and hospitalization. Many individuals with severe symptoms require corticosteroids to reduce inflammation and bronchodilators in order to open up the bronchial tree. Antibiotics are not indicated unless there are accompanying infections.

Source: Medical Disability Advisor



Prognosis

Recovery is usually complete once the offending agent is identified and removed. In the case of individuals who have contracted the disease from their workplace, resolution of the pneumonitis may require a change of location or occupation. Although permanent disability is uncommon from this disease, the chronic form is often progressive and thus a full recovery is often not possible.

Source: Medical Disability Advisor



Complications

Severe hypersensitivity pneumonitis may result in chronic bronchitis and permanent lung damage. Asthma-like allergies could also develop.

Source: Medical Disability Advisor



Ability to Work (Return to Work Considerations)

The individual who contracts hypersensitivity pneumonitis in the workplace often must change his work location to avoid the offending agent. However, socioeconomic factors may preclude a complete change of environment. Restrictions may be necessary for individuals in hazardous waste operations. Some individuals obtain good results by wearing filtered masks or helmets that prevent exposure to offending substances. Chemical sprays may be utilized to prevent the growth of bacteria, molds, or fungi in certain crops (i.e., hay). Preventive maintenance should be performed routinely in all heating, ventilation, and air conditioning equipment.

Source: Medical Disability Advisor



Failure to Recover

If an individual fails to recover within the expected maximum duration period, the reader may wish to consider the following questions to better understand the specifics of an individual's medical case.

Regarding diagnosis:

  • Does individual have an occupation in which inhalation of microorganisms or animal or vegetable protein may be present, particularly those who work on farms and those who work with birds?
  • Has individual recently worked in another organization where chronic exposure is higher?
  • Does individual work in a building that relies on forced air ventilation systems or humidifiers?
  • Is building adequately maintained?
  • Could exposure be occurring outside the workplace; i.e., in the home, community, or recreational activities?
  • Has individual experienced previous episodes of hypersensitivity pneumonitis?
  • Does individual complain of fever, chills, cough, difficulty in breathing (dyspnea), nausea, muscle aches, fatigue, and malaise?
  • Did these symptoms occur 4 to 8 hours after antigenic exposure, suggesting an acute episode?
  • Does individual complain of chronic shortness of breath and cough on exertion, suggesting a chronic condition?
  • Does individual report anorexia or weight loss?
  • Were blood tests done to include a complete blood count (CBC) and examination for specific antigens?
  • Were chest x-ray, pulmonary function studies, and/or aspiration of lung fluid for microscopic examination done?
  • Were samples of lung tissue (biopsy) taken for examination for infectious organisms?
  • Were conditions with similar symptoms (pulmonary fibrosis, chronic bronchitis, pneumonia, tuberculosis) ruled out?
  • Was the diagnosis of hypersensitivity pneumonitis confirmed?

Regarding treatment:

  • Has individual been completely removed from the agent that caused the problem?
  • Did individual require emergency medical treatment and hospitalization?
  • Were corticosteroids given to reduce inflammation?
  • If there was accompanying infection, were appropriate antibiotics prescribed?
  • Was individual compliant with all medications?

Regarding prognosis:

  • Does individual require a change of occupation or work location to prevent exposure to the offending agent?
  • Does individual smoke? If so, would a smoking cessation program be appropriate for this individual?
  • Has individual developed chronic bronchitis and permanent lung damage?
  • If so, how will they be treated and what is the expected outcome?
  • How severe is the lung damage?
  • How will this damage affect individual's activities of daily living?
  • Has individual developed asthma-like allergies?

Source: Medical Disability Advisor



References

Cited

Sharma, Sat. "Hypersensitivity Pneumonitis." eMedicine. Eds. Michael Peterson, et al. 12 Aug. 2004. Medscape. 11 Oct. 2004 <http://emedicine.com/med/topic1103.htm>.

Source: Medical Disability Advisor






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