|
Pediatric pulmonary function labs are pioneering new techniques to help tailor treatments to slow or halt the pulmonary changes from asthma, cystic fibrosis, chemotherapy, and other diseases.
Clinicians at Yale University School of Medicine, New Haven, Conn., for instance, are adapting a test commonly used to measure lung volume and functional residual capacity to more specifically monitor lung changes and track the effect of prescribed interventions in patients with cystic fibrosis.
In a typical helium dilution test, a patient breathes a mixture of helium and oxygen in the closed circuit of the spirometer. Functional residual capacity is then calculated by subtracting the volume of air in the spirometer following the test from the original volume of air in the spirometer. In this new method, clinicians use the same test but interpret the data differently.
"You look in the population of patients to see whether it takes a longer time for the helium to equilibrate in patients who otherwise might have a normal pulmonary function," said Pnina Weiss, MD, FAAP, medical director of Yale University School of Medicine's pediatric pulmonary function lab. "Perhaps there is some very small airway disease that you can't see, and this may be reflected in the longer period for inert gases to equilibrate."
If their research identifies early markers of cystic fibrosis, it would allow clinicians to start therapies sooner and target children with more subtle disease symptoms. "It would be really nice to prevent some of the lung disease," Dr. Weiss said.
Impulse oscillometry
Accurately assessing pediatric patients' smaller lung volumes is not always easy in squirmy children. Impulse oscillometry (IOS) circumvents these difficulties, allowing clinicians to track similar changes in their most difficult to assess patients: children between age 3 and 5, and patients with muscular dystrophy who are too weak to sustain the five to six second continuous blow of spirometry.
With IOS, all the children have to do is sit still while the "thuh, thuh, thuh" soundwaves of IOS pulse in their small lungs. But even sitting still can be a challenge for youngsters.
"Some of them tend to not pay attention because they are smaller," said Michael Cooper, CRT, coordinator of the pediatric pulmonary function laboratory at Rush University, Chicago. "They don't want to keep (the device) in their mouth for a very long time, and they tend to put their tongue in the mouthpiece."
When his two-clinician teams can coach the patient to keep still for the full 60 to 90 seconds, the results provide valuable information to fine-tune medication. IOS sometimes can identify changes produced by a bronchodilator in a cystic fibrosis patient's airway that traditional spirometry will not. It also can look at airway resistance in the airways to determine whether the patient is having a flare-up.
This increased sensitivity helps keep patients with cystic fibrosis healthier longer, with fewer infections that could decelerate them into the end stage of chronic lung disease, said Ellen Moran, RRT, RPFT, AE-C, coordinator of Rush University's adult pulmonary function lab.
This same sensitivity can help weed out patients who have been falsely diagnosed with asthma. By analyzing the return frequencies of the IOS soundwaves, clinicians can determine if it is the high-high hertz combination of vocal cord dysfunction and upper airway issues or the high-low combination of a smaller diffuse airway problem such as asthma. "It is the number one way to get a handle on this type of complaint," Moran said.
|