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Carbon monoxide diffusing capacity
For some patients, airway problems are not their primary condition. Children diagnosed with cancer routinely visit the pulmonary function lab for testing before, during, and after undergoing chemotherapy. "Carbon monoxide diffusing capacity is a great tool to assess lung damage," Cooper said.
Doctors expect a DLCO above 80 percent when a child begins chemotherapy. But during the course of treatment, the chemotherapy agents can harden lung tissue or increase pulmonary inflammation, which reduces the diffusion of oxygen through the membranes and lowers the DLCO percentage.
If the number drops significantly during treatment, then the oncologist may request oxygen therapy or breathing treatments, or even change the patient's treatment.
If the doctor and child's family decide to finish the chemotherapy course, the pulmonary function lab will again assess the child's lung damage to see if the numbers begin to reverse.
While most advances in pediatric pulmonary function testing focus on airway function, some studies concentrate on utilizing DLCO to assess infants' lung parenchymal function and gas transport.
These measurements could determine whether normal alveolarization is affected by premature birth or the secondary respiratory care required by premature birth, said Robert S. Tepper, MD, PhD, a professor of pediatric pulmonology and critical care at Indiana University School of Medicine and James Whitcomb Riley Hospital for Children in Indianapolis. DLCO testing could lead to more appropriate definitions of early lung disease and better tools to evaluate early therapeutic interventions' efficacy.
Exhaled nitric oxide
Clinicians routinely use DLCO testing to determine the presence and severity of exercise-induced asthma. They rely on its data to see how long it takes the patient to be affected by and recover from EIA, and whether the patient responds to a bronchodilator to determine the asthma severity.
A relatively new measure, exhaled nitric oxide testing, adds valuable clinical data about the severity of EIA. Exhaled nitric oxide reflects eosinophilic inflammation in the airways.
"High nitric oxides are associated with an increased incidence and severity of exercise-induced asthma," Dr. Weiss said.
These values also reveal a rare subpopulation - about 10 percent of patients with EIA - with normal exhaled nitric oxide levels. The patients may not have underlying atopy, which makes them different from those who are allergic and have underlying persistent asthma. Further research is needed to determine the cause of these patients' EIA, but Dr. Weiss pointed to air pollution, exercise, and genetic predisposition as potential culprits.
Kristen Ziegler is assistant editor of ADVANCE. She can be reached at kziegler@advanceweb.com.
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