COPD: Listening to the 'silent' zone
Chronic Obstructive Pulmonary Disease Exciting technological progress focusing on the small airways in the lungs is transforming both testing for and treatment of Chronic Obstructive Pulmonary Disease (COPD).
The large and small airways in our lungs are like a tree, explains Dr Omar Usmani, Reader in Respiratory Medicine and Consultant Physician at the National Heart and Lung Institute, Imperial College London & Royal Brompton Hospital. “The large airways represent the trunk and bigger branches, and the small airways are like the much smaller branches extending into the leaves. In COPD, we call those small airways ‘quiet’ or ‘silent’ – not because they actually are, but because our listening tools haven’t been that sensitive to pick up the noisy disease of COPD.”
Traditional COPD diagnosis has relied on symptoms – such as increasing breathlessness, coughing or sputum – and conventional lung function testing using spirometry, which has tended to identify the large airways, leaving problems in the small airways undetected. To put this in perspective, the larger airways, if condensed, would occupy an A5 piece of paper, while the small airways would account for a staggering 140 square metres.
“Spirometry’s not always an easy test,” says Usmani, “because it requires a forced exhalation effort that doesn’t really reflect how the lungs normally work. New methods of lung function testing using oscillometry is much more comfortable: you sit in a chair breathing normally and get results immediately.”
Another part of the challenge has been the size of drug particles used in treatment devices: COPD is caused by noxious, large particles (for example, as ingested by smoking) which can get into all the airways, and the particles in inhalers have been fairly large too, which means that only 10-15% gets down into the lungs.
Over recent years, there’s been a lot of innovation in meeting the challenge of improving treatment delivery, says Usmani. “Aerosol and formulation scientists got together with device engineers, with the result that we now have inhalers which can achieve a hugely improved rate of 30-40% deposition in the lungs. That’s thanks to the use of smaller particles which can also go deeper into the small airways, but it also depends on how fast you inhale from the device.”
Correct use of devices key in COPD management
How to use the inhaler is a key area where there is still a lot of education to be done, he says, both among the general public and practitioners. “The first things practitioners should do when a COPD patient isn’t responding to treatment is not just to increase the dosage, but to teach the patient how to use the device correctly,” says Usmani. “The fact is that healthcare practitioners themselves are still poorly trained in how to use devices.”
However, education among practitioners is ongoing, and GPs may also have pharmacists or nurses on hand to help patients, which eases the restriction on the doctor’s time. “It has to be a shared, informed decision between healthcare practitioner and patient,” stresses Usmani.
Further developments he and other specialists are working on include the use of stents or coils to collapse damaged parts of the lung, allowing healthy lung tissue to grow into that area.
“These are ‘watch this space’ developments,” Usmani explains. Despite continuing challenges, “these are exciting times in COPD testing and treatment.”