Airway Tapering in Patients With COPD

In this podcast, Sandeep Bodduluri, PhD, talks about using a chest computed tomography imaging-based measurement of airway tapering to help improve early detection of chronic obstructive pulmonary disease.

Additional Resource:

Sandeep Bodduluri, PhD, is an instructor of pulmonary and critical care medicine at the University of Alabama at Birmingham and a researcher at the UAB Lung Imaging Lab in Birmingham, Alabama.

Published in partnership with The American Thoracic Society.



Jessica Bard: Hello everyone, and welcome to another installment of "Podcast 360." Your go‑to resource for medical news and clinical updates. I'm your moderator, Jessica Bard, with Consultant360 Specialty Network.

Cigarette smoking is a major risk factor for COPD. Cigarette smoke causes inflammation, and the airway becomes narrower or the airway becomes lost.

Dr Sandeep Bodduluri is here to speak with us about a CT‑based measure of airway tapering. Dr Bodduluri is an instructor of Pulmonary and Critical Care Medicine at the University of Alabama, Birmingham. He's also a researcher at the UAB Lung Imaging Lab in Birmingham, Alabama.

Thank you for joining us today, Dr Bodduluri. You're presenting your research airway tapering in chronic obstructive pulmonary disease at ATS 2021. Can you please give us an overview of your session?

Dr Sandeep Bodduluri: Sure. Airway tapering. COPD consists of two main components. One is emphysema which is a lung parenchymal disease, and another is an airway disease. The major components of airway disease are either the airway gets narrowed or airway gets lost, especially the small airways.

With the use of CT imaging in a lot of studies a lot of teams have developed a new measures to measure the diameter of the branch, so that they know that when the airway gets narrowed over time with the disease, or they also try and started to count the number of branches in your airway tree.

Through that metric, you could know how many airways got lost with the disease or with the progression of COPD. Both of these metrics are separate where we are trying to come up with a summative metric that could get influenced by both airway narrowing and airway loss, because narrowing and loss are not separate phenomenons in COPD.

Both can happen simultaneously, or one can be predominantly ominous compared to the other. We're trying to come up with an imaging‑based metrics where that metric can be influenced by both narrowing and loss. We've used airway tapering.

Airway tapering is nothing, but it's not a new concept. People have used airway tapering to differentiate bronchiectasis patients from non‑bronchiectasis patients. Airway tapering is, you measure the cross‑sectional area of the airway tree, starting at the top of the trachea to all the way down, and you plot it against the distance from the start of the trachea to all the way down.

Essentially, as we go down from the tone into an airway tree, the cross‑section area keeps decreasing because it keeps branching out more and more. It starts with one big tube. It becomes two children, and again those two become four. Four becomes eight, but those all four will get decreased in terms of cross‑sectional area.

Once you plot that and take a slope of that curve, that tell you how much tapering happened. When I say tapering is how much narrowing happened in an airway tree.

A lot of the previous studies have used touch airway tapering in COPD subjects. We tried to use and show that, because airway tapering captures narrowing. Essentially, the airway gets lost, the tapering, there is no cross‑section area to measure, so the slope also changes.

This slope of the tapering can combine both airway narrowing effect and also airway loss effect. We were able to show that in COPD with increase in disease, the slope does decrease as expected, and for those people who have a lower airway tapering slope had worse survival after five years.

Jessica: What causes airway tapering in patients with COPD? How can it be prevented? What are some treatment options?

Dr Bodduluri: Airway disease in COPD, again, is caused by multitude of factors. Again, cigarette smoking is a major primary risk factor for COPD. It starts with inflammation from the cigarette smoke. Eventually, like in any asthma or any airway disease patient, airway starts getting narrowed.

Eventually in some airways, due to the surrounding tissue damage, airway gets lost. Some of the small airway gets lost. This a major cause of airway disease in COPD.

What tapering captures is a narrowing of these airways, especially at the distal down of the airway tree, or the distal generation of the airway tree. There is no prevention as I said, the cigarette smoking is the primary factor.

There is no prevention or treatment at this time for the COPD, but major prevention is quitting smoking and making sure that once quit smoking is how do you manage the COPD once you get diagnosed with COPD?

Jessica: How does airway tapering affect how healthcare providers care for their patients with COPD?

Dr Bodduluri: To diagnose COPD, spirometry is the current gold standard where through lung function or through lung volumes, we diagnose a patient has a COPD or not. Also, with the imaging, we can know at what anatomical level or what areas of the lung are getting damaged with the COPD.

The airway tapering metric, which we're proposing right now, can be used as a prognostic marker to detect these patients early prior to the loss of a lot of lung function, because by the time they reach the diagnostic level of spirometry, a lot of people already have damage in their lungs, or damage in their airways.

We're trying to use this metric. Whenever somebody comes in and get a CT scan available for this patient, we can quickly get the airways out. From these airways, we could show that there is tapering happening or the narrowing of airways happening in this patient, so they can get diagnosed early. It's more often early imaging marker or a prognostic disease marker.

It also can be used in disease progression. If a patient is returning after five years or 10 years, we could use a tapering slope at the baseline and we can also calculate the slope at the tapering value at the follow‑up CT scan, and try to compare these two measures and see how much airways got damaged.

Jessica: What are the overall take‑home messages for our audience today?

Dr Bodduluri: Overall take‑home message here is that CT imaging, especially in COPD, has enabled extensive phenotyping of COPD population. Before with only using spirometry, we don't know somebody's predominantly affected by lung damage or airway damage.

With the imaging or with these new markers or the new measures, we can now differentiate partially. Not completely yet, we are not there yet, but partially we can now differentiate.

Certain population are affected by lung damage, especially by emphysema or by an airway damage. There are two groups of thinking right now. One is airway predominant population of COPD, and emphysema predominant or a lung damage predominant population of COPD.

The overall take‑home message is CT imaging can help us improve early detection of COPD, and also can help us in tracking disease progression.

Jessica: Is there anything else that you'd like to add today?

Dr Bodduluri: Other point we all face, especially in developing these markers are, how reproducible are these metrics? I know here is a big debate going on in terms of how reproducible are these CT imaging markers.

That's something we all as a research group or as a research scientist, we all have to work on because multiple scanners are the way somebody acquires an image of a patient might differentiate or might influence the values of these numbers.

It is critical to have a baseline or conduct these markers, studies in a baseline and a nonsmoker population, and use that information to differentiate COPD population from the normal population. I think the next steps would be achieving the reproducibility of these metrics.

Jessica: Thank you so much for your time today. It was a pleasure speaking with you.

Dr Bodduluri: Thank you, Jessica.