Download Respiratory impairment and Disability

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.