Rationale: Lung function tests are often underutilized in assessing children hospitalized
with asthma prior to discharge. We hypothesized that children with status asthmaticus may have more
airflow obstruction and air trapping on lung functions than is apparent by physical examination alone.
Methods: We retrospectively reviewed pulmonary function tests (airflow and lung volumes) of
children admitted to Norton Children’s Hospital (a tertiary care center) with asthma over a two-year
period. Patients performed pulmonary function testing, according to ATS criteria, when the treating
physician felt the patient was ready for discharge based on clinical improvement and the respiratory
assessment score. Patients (ages 6-17, mean 12 years) were included if they had an admitting
diagnosis of asthma and were able to perform lung function testing (both spirometry pre- and postbronchodilator
and lung volumes). Lung function tests were excluded if they showed poor to variable
effort based on flow-volume loop or a purely restrictive pattern in airflows.
Results: We analyzed one hundred sixty-three lung function tests obtained over a two-year period.
The mean FEV1/FVC ratio measured 0.78 (range 0.46 to 1.0), while the mean RV/TLC ratio
measured 0.32 (range 0.14-0.53). Lung function testing showed moderate to severe air trapping
(RV/TLC >31) in 55% of tests. 44% of tests had FEV1 less than 80 percent predicted. 58% of tests
showed FEV1/FVC ratio less than or equal to 0.8. A negative correlation was seen between FEV1 and
RV/TLC as well as between age and RV/TLC. We observed no correlation between the FEV1/FVC
and RV/TLC. The highest RV/TLC ratio (0.53) had a normal FEV1/FVC ratio (0.91).
Conclusions: We found children admitted with asthma to have more severe airflow obstruction and
air trapping on spirometry than was apparent on physical assessment. Assessment of lung volumes
may provide physiologic information which is not evident by spirometry alone. Further study on its
role in clinical inpatient care is warranted.