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Respiratory Impairment and Disability A. H. Mehrparvar, M.D. References Anderson, Cocchiarella; Guides to the evaluation of permanent impairment, 5th edition, 2001. “Guidelines for the evaluation of impairment / disability in patients with asthma”, ATS criteria, 2003. W. N. Rom; Environmental and occupational medicine, 3rd. Edition, 1997. Abramson, Burden, Field; “Evaluation of impairment, disability, and handicapcaused by respiratory disease” Thoracic society of Australia and New Zealand, 1992. Respiratory system consists of: Tracheobronchial tree Pulmonary parenchyma Rib cage Impairment and Disability Impairment: a loss, loss of use, or derangement of any body part, organ system or organ function (a medical issue) Disability: absence from work or loss of work attributed to a medical condition (a non-medical issue) (disability is a term used to indicate the total effect of impairment on the patient’s life) Impairment percentage or rating Estimates that reflect the severity of the medical condition and the degree to which the impairment decreases an individual’s ability to perform common daily activities, excluding work. Important data for impairment evaluation History (occupational and nonoccupational) Physical examination Imaging Lab data PFT Symptoms associated with respiratory diseases Dyspnea: The most common, non-specific Cough, Sputum, Hemoptysis Wheezing Thoracic cage abnormalities Examinations Respiratory rate Use of accessory muscles Respiratory sounds (crakle, Wheezing,…) Respiratory pattern (e.g. pursed lips,…) Chest wall abnormalities And … Imaging Chest X ray (AP and lateral in full inspiration) CT, HRCT Other tests Spirometry (the most beneficial test in evaluating functional changes) DLCO Cardiopulmonary exercise testing (VO2 max) ABG Cardiopulmonary exercise testing (Vo2 max) Exercise capacity is measured by oxygen consumption per unit time (Vo2) in ml/(kg.min) or in metabolic equivalents (METS) 1 METS = 3.5 ml/(kg.min) An individual can sustain a work level equal to 40% of Vo2 max for an 8-hour period. Cardiopulmonary exercise testing (Vo2 max, Cont.) Work intensity O2 consumption Excess energy expenditure Light work 7ml/kg; 0.5 L/min <2 METS Moderate work 8-15ml/kg; 0.6-1.0L/min 2-4 METS Heave work 16-20 ml/kg; 1.1-1.5L/min 5-6 METS Very heavy work 21-30ml/kg; 1.6-2.0L/min 7-8 METS Arduous work >30ml/kg; >2.0 L/min >8 METS Permanent impairment due to respiratory disorders (whole person) Class 1 (0% impairment) Class 2 (10%– 25% impairment) Class 3 (26%– 50% impairment) Class 4 (51%-100% impairment) Class 1 FVC and FEV1 and FEV1/FVC ≧ lower limit of normal And DLCO ≧ lower limit of normal Or VO2 max ≧ 25 ml/ kg.min (7.1 METS) Class 2 FVC or FEV1 ≧ 60% of predicted and < lower limit of normal or DLCO ≧ 60% of predicted and < lower limit of normal or 20 ≦VO2 max < 25 ml/ kg.min (5.7-7.1 METS) Class 3 51% ≦ FVC ≦59% of predicted or 41%≦ FEV1 ≦ 59% of predicted or 41%≦ DLCO ≦ 59% of predicted or 15≦VO2 max≦20 ml/ kg.min (4.3 < METS < 5.7) Class 4 FVC ≦ 50% of predicted or FEV1 ≦ 40% of predicted or DLCO ≦ 40% of predicted or VO2 max< 15 ml/ kg.min (< 4.3 METS) Asthma Diagnosis of asthma requires: 1. Relevant symptoms and signs (cough, sputum, wheeze,…) 2. Evidence of airflow obstruction (partially or completely reversible) or airway reactivity to methacholine Evaluation of impairment in asthma 1. Spirometry (before and after bronchodilator) 2. Challenge test Measurement of spirometry Spirometric measurements should be made after withholding inhaled bronchodilators for 8 hours and long-acting bronchodilators for 24 hours. Antiinflammatory drugs such as cromolyn, inhaled or systemic corticosteroids should not be withheld. Measurement of spirometry (Cont.) FEV1, FVC and FEV1/FVC is measured If: FEV1/FVC < lower limit of normal Then: repeat spirometry after administration of an inhaled bronchodilator Improvement in FEV1 of 12%, with an absolute change of 200 ml from baseline indicates reversibility Measurement of spirometry (Cont.) If: improvement in FEV1 <12% Then: Begin steroid therapy (>800 mcg beclomethasone /day) Improvement in FEV1 of 20%, indicates reversibility Airway hyperresponsiveness (bronchial challenge test) Measurement of airway responsiveness is needed for diagnosis and impairment rating if subject has no current evidence of airflow limitation. The test should be done after withholding inhaled short-acting bronchodilators for 6 hours and longacting for 24 hours. The provocation concentration to cause a fall in FEV1 of 20% (PC20). Airway hyperresponsiveness (bronchial challenge test, Cont.) If PC20 is ≦ 8 mg/ml methacholine or histamine, hyperresponsiveness is considered. Parameters for impairment evaluation in asthma FEV1 % of FEV1 change (reversibility) PC20 mg/ml Minimum medications Score 0 FEV1 ≧ lower limit of normal Reversibility <10% PC20 > 8 mg/ml No medication Score 1 FEV1 ≧ 70% of predicted 10% < Reversibility < 19% 0.6 mg/ml < PC20 < 8 mg/ml Occasional but not daily bronchodilator or cromolyn Score 2 60% < FEV1< 69% 20% <Reversibility < 29% 0.125 mg/ml <PC20 < 0.6 mg/ml Daily bronchodilator or cromolyn or daily low-dose inhaled corticosteroid Score 3 50% < FEV1< 59% 20% ≦ Reversibility PC20 ≦ 0.125 mg/ml Bronchodilator (PRN) or daily high-dose inhaled corticosteroid (800mcg beclomethasone) or occasional systemic corticosteroid Score 4 FEV1 < 50% of predicted Bronchodilator (PRN) or daily high-dose inhaled corticosteroid (>1000 mcg beclomethasone) or daily or every other day systemic corticosteroid Impairment rating for asthma Total asthma score 0 % Impairment Class 1 Imp. Of the whole person 0% 1-5 2 10-25% 6-9 3 26-50% 10-11 (or asthma 4 51-100% uncontrollable despite maximal treatment) Types of impairment/disability in asthma 1. Temporary: after diagnosis of occupational asthma, the patient is 100% impaired for the job that has caused the symptoms and treatment is to remove the worker from exposure. 2. Permanent: assessment for permanent impairment should be done 2 years after the removal from exposure. Sleep apnea For grading sleep apnea: 1. Number of apnea / hypopnea episodes in polysomnography 2. Severity of hypoxia There is no standard for impairment rating. , only judgment of a sleep specialist is important.