Introduction
Respiratory impairment refers to an alteration in lung structure and/or lung function that results in decreased or limited functional ability and is usually manifested by dyspnea on exertion. Many respiratory diseases may cause impairment, from airway disease such as asthma and chronic obstructive pulmonary disease (COPD) to interstitial lung diseases. A pulmonary physician may be asked to evaluate impairment and/or disability, either for his or her own patients or for others in the context of an independent medical examination through a benefits or compensation program and/or to provide a statement about ability to work.
This chapter reviews the elements of an impairment evaluation. An overview of the major programs in the United States is presented. The program details, including how disability and/or impairment is determined under specific programs, is contained in the online version of the chapter. Impairment ratings are described using the framework for the assessment of respiratory impairment set forth by the American Thoracic Society (ATS) along with an overview of the most commonly used impairment rating methodology contained in the American Medical Association ( AMA ) Guides to the Evaluation of Permanent Impairment, hereafter referred to as the AMA Guides. However, the AMA Guides are not used by every benefit and compensation system. The evaluating physician must understand and follow the rules and specific requirements of the program under which the patient is being evaluated. The final determination on the award is usually made by personnel in the program or a judge, but the thoroughness of the medical report and its consistency with the program requirements will increase the weight given to the physician’s medical opinion. Finally, an overview of workplace protections for workers with lung disease is covered.
Definitions
There is a critical distinction between the terms impairment and disability. The terms impairment and disability are often used interchangeably, perhaps made more confusing by the fact that different benefits and compensation programs may use both terms but focus on one more than the other. Impairment occurs at the organ or organ system level. Whole-person impairment refers to the loss relative to the functioning of the body as a whole. Disability, in contrast, refers to the person in terms of limitation in the ability to perform normal activities, including personal, social, and work activities.
Physicians should understand that such determinations are medicolegal decisions, and they can have additional ramifications for the patient beyond that of providing a diagnosis. The physician may be asked to address causation (i.e., the physician may need to opine whether the respiratory condition was caused or at least aggravated by a certain factor, most commonly work, on a more-likely-than-not basis).
Although the terms “impairment” and “disability” are related, it is important that each term be applied in accordance with its precise definition. The definitions used in most existing benefits and compensation programs in the United States are based on the World Health Organization’s (WHO’s) International Classification of Impairment, Disability, and Handicap (ICIDH) model from 1980. This model was replaced by the International Classification of Functioning, Disability, and Health (ICF) in 2001, which uses different definitions of these words. To avoid confusion, the definitions from the ICIDH are presented here. The ICF model and the framework for disability put forth by the Institute of Medicine (IOM) are presented in the “Future Directions” section.
Impairment
Impairment refers to the degree of loss of normal use or function of a body part or organ. It was defined by the WHO as “any loss or abnormality of psychological, physiologic, or anatomic structure or function.” It was defined by the AMA as “a loss, loss of use, or derangement of any body part, organ system or organ function.”
The essential elements that make up an impairment evaluation will vary to some degree according to the program or system through which the evaluation is being performed. Standard components typically include history, with occupational and environmental history and description of limitations in activities of daily living (ADLs); physical examination; and review of medical records and diagnostic test results that establish the respiratory condition.
Although pulmonary function test (PFT) results are the primary factor that determine the presence and degree of pulmonary impairment, some systems will specify that particular tests should be used for assessment of impairment or disability, whereas others allow physician discretion in choosing another test if he or she believes it to be a more accurate reflection of the patient’s true respiratory impairment. Some programs will only allow physicians with certain qualifications to perform impairment ratings. Additional elements that may need to be addressed can include delineation of permanent work restrictions, outline of future medical treatment requirements, and/or consideration of apportionment.
Before a physician can determine that a condition has resulted in permanent impairment or disability, the diagnosis should be well defined, the condition stable, and medical treatment either optimized or reasonable options exhausted. When these criteria are met, this is termed maximum medical improvement (MMI).
Disability
Disability refers to any resulting alteration in the individual’s capacity to perform customary activities. It was defined by the WHO as “any restriction or lack of ability to perform any activity within the range considered normal for a human being.” The AMA defined disability as an “alteration of an individual’s capacity to meet or perform personal, social, or occupational demands or statutory or regulatory requirements because of an impairment.”
Although the degree of impairment frequently correlates with the degree of disability, this is not always the case. The classic example of this is the loss of the fifth finger of the nondominant hand. Under the typical impairment rating system, the loss of this finger would be associated with a small impairment of the whole person. For the average person, this small impairment would result in a correspondingly small disability. For a concert pianist, this small impairment would be associated with significant disability, particularly in the context of work activities.
Additional Terms
Temporary impairment refers to impairment that exists only for a limited period of time after an injury or illness.
Temporary disability insurance covers partial compensation for loss of wages due to a non–work-related injury or illness. Partial compensation for lost wages, as well as medical benefits, are covered by workers’ compensation for work-related injuries and illness.
Permanent impairment can be assessed only once the patient has reached MMI. MMI is defined in the AMA Guides, Sixth Edition, as the “point in time in the recovery process … when further formal medical or surgical intervention cannot be expected to improve the underlying impairment” and “symptoms can be expected to remain stable with the passage of time, or can be managed with palliative measures that do not alter the underlying impairment substantially.” This is termed “permanent and stationary” in some systems.
Whole-person impairment refers to the alteration in the functioning of the body as a whole and therefore can range from 0% (no impairment) to 100% (essential cessation of all body functions).
Permanent partial impairment is the numeric percentage of the loss of body functioning due to the loss or limitation in the functioning of the organ or organ systems affected. For most respiratory conditions, the primary organ involved is the lung, but at times, the pulmonary arteries or nose and throat may be affected.
Permanent total disability is the medicolegal determination that a person’s impairment precludes future gainful employment.
Handicap refers to the societal disadvantage caused by an impairment or disability. It was defined by the WHO in the ICIDH model as “a disadvantage for a given individual that limits or prevents fulfillment of that person’s normal role depending on sex, age, social and cultural factors.”
Clinical Approach to Impairment Evaluations
Although the term impairment rating is sometimes used interchangeably with the term impairment evaluation, the impairment rating itself is but a small part of what should be a comprehensive medical evaluation ( Table 28-1 ). The physician must first fully understand the purpose and requirements of the program for which the evaluation is being conducted. The initial goal of the impairment evaluation should be to confirm the medical diagnosis, through a thorough, detailed patient history, physical examination, and review of diagnostic testing results that established the diagnosis. The diagnosis or diagnoses should be clearly stated, along with extrapulmonary conditions that may be contributory to symptoms, limitations in ADLs, and/or impairment. A statement of MMI is often required. Factors important to the impairment rating itself include items from history, physical examination, and diagnostic testing results that reflect disease severity, including impact on normal ADLs, and current treatment requirements. The physician may be asked to make a statement on causation or apportionment. An outline of reasonably anticipated future medical course and treatment requirements should be given. The following sections describe the various aspects of an impairment evaluation, including the history to be taken, the examination to be conducted, and the testing to be obtained depending on the diagnosis considered and the type of evaluation being performed.
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History
The history of present illness (HPI) is the standard, detailed respiratory history used by most pulmonologists, including symptoms of cough, cough with phlegm, wheeze, chest tightness, and shortness of breath. If present, details should be provided that include when the symptom started, exacerbating and alleviating factors along with temporal relationship, progression over time, and current status including frequency, severity, and response to any medication that is used. A scale for the rating of dyspnea is suggested in the AMA Guides, based on the Epidemiology Standardization Project, which also provides standardized questions for the assessment of other symptoms. Questions about conditions such as chronic rhinitis, postnasal drip, gastroesophageal reflux disease, cardiac disease, and other lung diseases, including smoking-related lung disease, may help the physician understand other possible contributors to respiratory symptoms. Although dyspnea is the primary limiting symptom of respiratory impairment, dyspnea can also result from nonpulmonary causes including cardiovascular disease, obesity, and deconditioning. Frequency, severity, treatment requirements, and duration of periodic exacerbations of diseases such as asthma and bronchiectasis should be well documented. Medications used or tried in the past for the treatment of the respiratory conditions should be described, along with a description of the relief afforded.
Constitutional symptoms are relevant in the HPI in patients with certain diseases, such as fever, sweats, chills, and fatigue in patients with hypersensitivity pneumonitis; chest pain, weight loss, and malaise in patients with asbestos-related lung disease; and night sweats and fatigue in patients with chronic beryllium disease.
A standard detailed past medical and surgical history, list of medications and allergies, family history, and review of systems will provide a good understanding of the patient as a whole. It will also allow the physician to identify other possible diseases that may be contributory to the patient’s current status, as well as to assess potential treatment-related side effects. The standard social history should include smoking history, including amount, duration, and current smoking status.
An element that may be new to most pulmonologists is the need to obtain a detailed occupational and environmental history. This is necessary to help the physician address whether there is a relationship between a respiratory condition and past or ongoing workplace exposures. The occupational history is most easily performed in chronological order starting from childhood. Details about the period of time spent at each job, the job title, description of the work performed, and details about jobs or processes that may have produced dust, fumes, gas, or smoke should be described, including estimation of intensity, frequency, and duration of exposure. Questions about ventilation and use of respiratory protection can provide helpful clues, as well as whether or not there were any immediate symptoms noted. Chemical exposures, particularly any heavy exposures or exposures that resulted in symptoms, should be detailed. If available, the Safety Data Sheet (SDS), formerly called Material Safety Data Sheet (MSDS), may be reviewed because it can provide helpful information on the components of the chemicals used in the workplace and potential associated health effects. Unfortunately, MSDSs are not required to provide complete information, and thus some are more reliable than others.
An environmental history includes questions about heating, cooling, and humidification sources; pets including birds; hot tubs; water-damaged areas; and exposures from hobbies should also be obtained to determine whether there is a relationship between the disease and any environmental exposures.
In addition to the just-discussed components, the history should also include a description of how the condition affects the person’s ability to perform normal ADLs. Questions most relevant to patients with pulmonary disease include ability to perform basic self-care such as showering; ability to walk, including estimated distance at own pace and at a fast pace or up a hill, estimated pace compared with others one’s own age, and number of flights of stairs that can be climbed; and ability to perform indoor and outdoor home maintenance chores, as well as customary hobby, exercise, and job-related activities. There are a number of standardized methods by which to assess ability to perform ADLs, some of which are disease specific. A list of ADLs suitable for all conditions is outlined in the AMA Guides. Symptoms and limitations in ADLs that are consistent with the lung disease and objective testing data provide useful supporting information for the impairment rating. Dyspnea scales are often used and can be a helpful way to summarize the relative degree of symptomatology or activity limitation. However, the degree to which dyspnea correlates with objective measures of pulmonary function and exercise performance is variable.
Physical Examination
A complete physical examination should be performed, with focus on the respiratory and cardiovascular systems. A detailed description of the chest should be made, including any deformities or scars, abnormal motion, respiratory rate and effort, breath sounds, and percussion, which can help support the diagnosis. Vital signs should be documented including blood pressure and heart rate, which may affect ability to perform pulmonary function and exercise tests, as well as height and weight, because obesity can cause PFT and exercise test abnormalities and contribute to pulmonary symptoms. Signs of hypoxemia, such as cyanosis and clubbing, should be documented. Signs of cor pulmonale, such as jugular venous distention, right ventricular heave, and liver engorgement, and peripheral edema provide evidence of severe respiratory impairment in patients with respiratory disease.
Diagnosis, Causation, and Maximum Medical Improvement
Any available or provided medical records should be summarized, with focus on the results of the diagnostic testing that help establish the diagnosis and/or severity of the condition. Medicolegal cases may often involve the review and summarization of large volumes of records. Some independent medical examinations require that only the records provided through the program be reviewed.
The list of medical diagnoses should start with the diagnosis of the condition for which the patient is being evaluated, including disease severity. The diagnosis of asthma associated with workplace exposures may fall under one of three different diagnoses: occupational asthma (new-onset asthma caused by a workplace exposure), work-aggravated asthma (existing asthma aggravated by a workplace exposure), and reactive airways dysfunction syndrome (RADS), which can result from a single high-level irritant exposure. Other diagnoses that may be contributory to symptoms, limitations in ADLs, or testing abnormalities should be clearly delineated.
If relevant, the diagnosis should also include a statement on causation, the physician’s opinion as to whether or not a given workplace exposure has caused or aggravated an illness. This is a medicolegal determination, also known as attribution, made on a medically probable basis, also known as a “more-likely-than-not” basis. That is, the physician should be able to opine with greater than 50% certainty that the exposure(s) in the workplace caused the respiratory condition or worsened an underlying condition on the basis of objective criteria, such as change in treatment requirements. This criterion is less rigorous than would be required for scientific proof of a hypothesis (i.e., 95% certainty). This is important because in cases of respiratory illness, there may be multifactorial causation, frequently a long latency between initial exposure and clinical onset of disease, nonspecific clinical manifestations, incomplete understanding of dose-response relationships from epidemiologic studies, and lack of individual exposure data. Although recognition of these limitations is necessary, causation can be attributed in most cases on a more-probable-than-not basis by simply applying reasonable judgment. This process is easier when the exposure is known, the dose-response relationship is well characterized, and competing diagnoses are unlikely. The physician should clearly describe the specific substances at the workplace; their known health effects according to the medical literature; the relative dose, in terms of estimated intensity, frequency, and/or duration of exposure; and finally, why it is medically probable that the exposure(s) caused or resulted in permanent aggravation of the diagnosed medical condition in this worker. When one or more of these conditions are not met, attribution should be based on the answers to the following questions.
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Is the diagnosis clearly established, and is it biologically plausible (or consistent with the available epidemiologic data) that the disease could have been caused or aggravated by the exposure in question?
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Have competing diagnoses been adequately considered?
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Is the exposure of sufficient intensity and duration to have caused or aggravated the disease?
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Has there been an adequately long latent period, or is there a temporal relationship between onset of exposure and clinical manifestation of disease?
Some systems, such as most state workers’ compensation and a Department of Labor Program, the Energy Employees Occupational Illness Compensation Program (EEOICP), require the physician to make a statement that the patient has reached MMI before performing an impairment rating. If the examining physician believes the condition is not stable or believes that there may be additional treatment reasonably likely to improve the condition, it is medically prudent to state this. What will happen logistically following determination of the MMI will depend on the specific program requirements. The examining physician should be aware of the ramifications of making these medicolegal determinations. For example, in the state workers’ compensation system, determination of MMI will allow the worker to be awarded permanent impairment but will also result in the cessation of temporary benefits such as compensation for lost wages, as the case is closed by the workers’ compensation insurance company.
Guides to Respiratory Impairment Ratings
American Thoracic Society Guidelines for Evaluation of Impairment or Disability
A number of systems have been used to determine respiratory impairment. Most base impairment primarily on lung function. In their “Guidelines for the Evaluation of Impairment/Disability Secondary to Respiratory Disorders,” the ATS recommends that impairment due to most lung diseases be rated on the basis of pulmonary function test (PFT) results. Pulmonary function testing is described in Chapter 25 . The results of the ATS impairment system, based on PFTs, place individuals into four impairment categories. Each of these categories provides a corresponding description of the associated ability to perform job demands ( Table 28-2 ). The ATS did not include a system by which to assign an associated numerically derived percentage of whole-person impairment, on which monetary awards are typically based. Therefore the ATS guidelines did not lend themselves to use in most compensation systems.
| Category | Criteria | Ability to Perform Job Demands |
|---|---|---|
| Normal | FVC ≥ 80% of predicted and FEV 1 ≥ 80% of predicted and FEV 1 /FVC×100 ≥ 75% and D l CO ≥ 80% of predicted | |
| Mildly impaired | FVC 60–79% of predicted or FEV 1 60–79% of predicted or FEV 1 /FVC×100 60–74% or D l CO 60–79% of predicted | Usually not correlated with diminished ability to perform most jobs |
| Moderately impaired | FVC 51–59% of predicted or FEV 1 41–59% of predicted or FEV 1 /FVC×100 41–59% or D l CO 41–59% of predicted | Progressively lower levels of lung function correlated with diminishing ability to meet the physical demands of many jobs |
| Severely impaired | FVC ≤ 50% of predicted or FEV 1 ≤ 40% of predicted or FEV 1 /FVC×100 ≤ 40% or D l CO ≤ 40% of predicted | Unable to meet the physical demands of most jobs, including travel to work |
American Medical Association Guides to the Evaluation of Permanent Impairment
The AMA Guides, Fifth Edition, adapted the ATS Guidelines by adding a system through which to assign a numerically derived percentage of whole-person impairment within each of the four impairment classes. Although the AMA Guides, Fifth Edition, is no longer the most current edition, the methodology is presented here because it is directly based on ATS Guidelines and because many compensation systems have not yet adopted the Sixth Edition. The AMA Guides, Fifth Edition, assigned the following associated ranges of whole-person respiratory impairment to each of the four ATS classes: class 1 impairment is equal to 0% whole-person impairment, class 2 (mild) impairment ranges from 10% to 25% impairment, class 3 (moderate) ranges from 26% to 50% impairment, and class 4 (severe) ranges from 51% to 100% whole-person impairment. After determining the class of impairment based on forced vital capacity (FVC), forced expiratory volume in the first second (FEV 1 ), FEV 1 /FVC, single-breath diffusing capacity (D l CO , or 
, the physician determines the final numeric percentage whole-person impairment on the basis of where the test results fall within that range of impairment, as well as other factors, including impact of the respiratory condition on the ability to perform ADLs.
The AMA Guides, Sixth Edition, adopts a different methodology, defining 4 classes of impairment: class 0: 0% whole-person impairment, class 1 (minimal) ranges from 2% to 10% impairment, class 2 (mild) ranges from 11% to 23% impairment, class 3 (moderate) ranges from 24% to 40% impairment, and class 4 (severe) ranges from 45% to 65% whole-person impairment. The “key factor” is the objective test data, FVC, FEV 1 , FEV 1 /FVC, and D l CO , using the measurement most relevant to the disease process. 
may be considered as the key factor if one of the other pulmonary function test results is abnormal. The specific value within the impairment class is determined by the physical examination findings, dyspnea, and treatment requirements. The maximum whole-person impairment in the AMA Guides, Sixth Edition, for most respiratory disorders is 65% whole-person impairment, rather than 100% whole-person impairment in previous editions, although this rating may still be combined with impairment in other organ systems.
Because a person can never have more than 100% impairment of the body, impairment in any additional organ system needs to be combined rather than added to the respiratory impairment. Each edition of the AMA Guides contains a special combining table for this purpose.
Classification of Impairment Resulting From Specific Pulmonary Diseases
Regardless of the rating system used, the greatest weight should be placed on objective data.
Asthma (for details concerning diagnosis and management of asthma, see Chapter 42 )
Rating asthma according to the standard respiratory disorder methodology can both underestimate and overestimate impairment, given the episodic and variable nature of airflow limitation and bronchial hyperresponsiveness. The ATS developed “Guidelines for the Evaluation of Impairment/Disability in Patients with Asthma” in 1993 to reflect the true impairment due to this condition. First, a worker with objectively confirmed asthma must be determined to be at MMI or to have achieved optimal therapeutic goals (i.e., minimum medication that obtains the best overall outcome). To rate asthma impairment according to ATS methodology ( Table 28-3 ), the postbronchodilator FEV 1 , reversibility (% change with bronchodilator), or methacholine challenge results (provocative concentration of methacholine inducing a 20% drop in FEV 1 [PC 20 in mg/mL]), and minimum medications required to maintain this status are assigned scores using Tables 28-3A, B and C . The class of impairment is defined by the sum of the asthma scores based on Table 28-3D . The AMA Guides, Fifth Edition, adopted the ATS methodology and assigned a numeric range of whole-person impairment for each impairment class that is equivalent to the impairment assigned for general respiratory conditions. Additionally, ATS added a fifth class of impairment, defined as asthma not controlled despite maximal treatment (i.e., FEV 1 remaining <50% despite use of ≥20 mg of prednisone daily). The AMA Guides, Sixth Edition, additionally recommends that an impairment rating be performed after the patient has achieved optimal therapeutic goals, and that it is prudent to wait at least 2 years after diagnosis and removal from exposure in cases of occupational asthma. In the AMA Guides, Sixth Edition, PC 20 mg/mL is used as the primary “key factor” by which to determine the class of asthma impairment, although postbronchodilator FEV 1 may be used as an alternative. Minimum medication requirements and frequency of attacks are used to determine the specific numeric rating within the class.
| A. Postbronchodilator FEV 1 | |
|---|---|
| Score | FEV 1 (% predicted) |
| 0 | > lower limit of normal |
| 1 | 70– lower limit of normal |
| 2 | 60–69 |
| 3 | 50–59 |
| 4 | <50 |
| B. Reversibility of FEV 1 or Degree of Airway Hyperresponsiveness * | ||
|---|---|---|
| Score | % FEV 1 change | PC 20 (mg/mL or equivalent) |
| 0 | <10 | >8 |
| 1 | 10–19 | 8– >0.5 |
| 2 | 20–29 | 0.5– >0.125 |
| 3 | ≥30 | ≤0.125 |
| 4 | — | — |
| C. Minimum Medication Need † | |
|---|---|
| Score | Medication |
| 0 | No medication |
| 1 | Occasional bronchodilator, not daily, and/or occasional cromolyn, ‡ not daily |
| 2 | Daily bronchodilator and/or daily cromolyn ‡ and/or daily low-dose inhaled steroid (<800 µg beclomethasone or equivalent) |
| 3 | Bronchodilator on demand and daily high-dose inhaled steroid (>800 µg beclomethasone or equivalent) or occasional course (1–3/year) systemic steroid |
| 4 | Bronchodilator on demand and daily high-dose inhaled steroid (>1000 µg beclomethasone or equivalent) and daily systemic steroid |
| D. Summary of Impairment Rating Classes § | |
|---|---|
| Impairment Class | Total Score |
| 0 | 0 |
| I | 1–3 |
| II | 4–6 |
| III | 7–9 |
| IV | 10–11 |
| V | Asthma not controlled despite maximal treatment (i.e., FEV 1 remaining < 50% despite use of ≥ 20 mg prednisone/day) |
FEV 1 postbronchodilator − FEV 1 prebronchodilator FEV 1 prebronchodilator × 100 %
PC 20 = antilog C 1 + ( log C 2 − log C 1 ) ( 20 − R 1 ) ( R 2 − R 1 )
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