Is it possible to measure treatment response after airway clearance therapy with a new and easy lung function test?
Why is this important?
Airway clearance treatments (physiotherapy or inhaled salbutamol, atrovent or hypertonic saline) are standard in the routine care of patients with CF. Until now no test has been found that is able to measure objectively short-term effects of physiotherapy, as a result treatment is mostly adapted based on patients’ subjective impressions. If there was an easy and fast way to assess effectiveness of treatment, airway clearance techniques could be optimized and adapted for the individual patient.
What did you do?
25 children (between 4 and 16 years) with CF performed lung function before and after inhalation of salbutamol/atrovent/saline and chest physiotherapy. Lung function consisted of lung function tests (spirometry) and gas washout tests. For gas washout tests subjects breathed 100% oxygen or a mixture of two gases (sulfur hexafluoride and helium) during one normal breath. The shape of the graph of the results of the measurement of these gases reflects how well the gas is mixed in the small airways of the lung, a very sensitive marker of CF lung disease severity.
What did you find?
Spirometry and the gas washout test using 100% oxygen improved after inhalation of salbutamol/atrovent/saline alone. These tests did not further improve after chest physiotherapy. The new gas washout test using sulfur hexafluoride and helium improved only slightly after inhalation of salbutamol/atrovent/saline, but improved significantly after chest physiotherapy. In general, all lung function tests showed a very mixed response, suggesting different changes in the individual.
What does this mean and reasons for caution?
The study suggests that the new gas washout test using sulfur hexafluoride and helium might be used to assess treatment response of chest physiotherapy. However, the intervention was not standardized, the study was not designed to compare different lung function tests, and there was a lot of short-term variability in lung function tests in individual patients.
We aim to better characterize those patients in whom the new lung function test may be especially useful and to better understand the underlying causes of the observed changes in gas mixing.