Department of Medicine, University of British Columbia; McDonald Research Laboratories/iCAPTURE Centre, and Adult Cystic Fibrosis Clinic, St. Paul's Hospital, Vancouver, British Columbia, Canada
With larger numbers of adult patients with cystic fibrosis (CF)
in the workplace, the issue of disability has arisen increasingly.
We examined relationships between measures of pulmonary impairment
and work/school capability and then determined whether quantification
of aerobic fitness improved predictability of disease-related
disability. We studied 73 patients with CF who performed lung
function and exercise capacity tests, completed a work/education
questionnaire, and were scored for clinical and chest radiographic
status. Patients who were characterized as unemployed and in
poor health had more severe pulmonary disease according to American
Thoracic Society impairment/disability criteria. Subjects were
further classified into three groups based on employment or
education status over the preceding 12 months. FEV
1, maximal
oxygen consumption, Schwachman–Kulczycki clinical and
Brasfield radiographic scores, and frequency of pulmonary exacerbations
over 2 years were associated with disability, but change in
FEV
1 over 2 years and oxygen saturation at rest or exertion
were not. FEV
1 and Schwachman–Kulczycki scores were the
best independent predictors of impairment/disability; specific
thresholds used in other pulmonary diseases were of limited
utility. We conclude that after accounting for either current
level of FEV
1 or Schwachman–Kulczycki scores, no other
physiological or clinical measures contribute to predicting
limitation in a work or school environment.
Key Words: patients with cystic fibrosis • disability • forced expiratory volume • impairment
Advances in both the diagnosis and treatment of cystic fibrosis
(CF) have led to substantial increases in survival of this population.
As a result, adult patients commonly outnumber pediatric patients
with CF. With more adult patients with CF in the workplace and
in light of the progressive nature of the disease, the issue
of disability inevitably arises. The medical assessment of job
performance or determination of potential work restrictions
is particularly challenging. The American Thoracic Society (ATS)
publication concerning evaluation of impairment/disability represents
one of the guidelines used in determining the presence and degree
of impairment caused by respiratory disorders (
1). This approach
uses resting pulmonary function tests and in some instances
measures of exercise capacity. Other national and state guidelines
for making impairment ratings also exist and also use pulmonary
function and exercise test measures. Impairment has been defined
as temporary or permanent change in pulmonary function and/or
maximal oxygen consumption (
O2max) (
1). Disability
is defined as the effect of impairment in an individual's life.
Severe impairment is defined as FEV
1% pred < 40%, FVC % pred
< 50%, FEV
1/FVC < 40%, or diffusing capacity of the lung
for CO (D
LCO) < 40% (
1). Exercise testing is recommended
if any of the resting pulmonary function measurements are abnormal
and above the energy demand threshold. A patient is characterized
as severely impaired if
O2max < 15 ml/kg
per minute, or if the occupational energy demand exceeds 40%
of the patient's
O2max (
1). Ortega and associates
have shown that a combination of resting pulmonary function
measurements and exercise performance assessment can more accurately
determine impairment in patients with chronic obstructive pulmonary
disease (
2). These thresholds have not been specifically evaluated
in patients with CF. Applicability to this patient group is
uncertain given the younger age and effects of other manifestations
of this disease.
The aim of our study was threefold: first, to determine the proportion of a cohort of adult patients with CF who are limited in their employment/education on the basis of current ATS impairment criteria; second, to investigate the utility of different measurements of resting pulmonary function and exercise capacity used to apportion impairment caused by other respiratory diseases in patients with CF; and finally, to evaluate the energy cost of the work of patients as a fraction of their measured O2max and relate this to the ATS impairment criteria.
SampleWe studied 73 stable patients with CF attending the Adult Cystic
Fibrosis Clinic at St. Paul's Hospital (Vancouver, BC, Canada).
We explained experimental procedures and risks before obtaining
written consent, which was approved by the Ethics Committee
of the University of British Columbia and St. Paul's Hospital.
Pulmonary Function
Spirometry (FEV1 and FVC) was performed in accordance with ATS criteria (3). Values were expressed as a percentage of normal values (3) and best postbronchodilator measurements were used. Predicted values were calculated from the equations for adults as derived by Crapo and associates (4). Fractional change in FEV1 (i.e., FEV1 = [FEV1(1998) – FEV1(2000)]/FEV1(2000)) was calculated to compare 2-year rates of change in lung function.
Resting and Exercise Tests
The O2max test was performed on a Monark (Vansbro, Sweden) stationary bicycle as described previously in Frangolias and Wilcox (5). Resting heart rate and oxygen saturation were measured for a 5-minute interval with subjects sitting before exercise testing.
Clinical Scores
We calculated Schwachman–Kulczycki (S–K) scores (6) and Brasfield scores (7) at the time of testing and tallied the number of days treated for pulmonary infections over 2 years.
Questionnaire and Patient Grouping
We obtained information about marital status, living arrangements, income sources, education level, and current status related to attending school or employment. We determined employment (full- or part-time) in or outside the home, postsecondary school attendance, and days missed from work/school due to CF-related illness. We obtained employment/school status from medical charts for the remaining patients attending the clinic to evaluate how representative our study sample was of the clinic population. Study subjects were then categorized on the basis of whether they were employed/attended school full-time, were employed/attended school part-time, or were unemployed due to poor health. Study subjects were further categorized on the basis of the ATS impairment criteria for FEV1% pred and O2max (1) into the following categories:
作者：
Despina D. Frangolias, Caroline L. Holloway, Sverr 2007-5-14