CT Air Trapping Metric May Predict Post-BLVR Pneumothorax Risk

Functional air trapping measured specifically within emphysematous regions of the lung, rather than across the whole lobe, may offer a meaningful pre-procedural signal for pneumothorax risk following bronchoscopic lung volume reduction (BLVR) in patients with chronic obstructive pulmonary disease (COPD), according to research presented at the American Thoracic Society (ATS) 2026 International Conference in Orlando, Florida.1

The retrospective analysis, presented by Isam Albaba, MBBS, from Temple University, examined quantitative CT (QCT) parameters in 59 patients who underwent BLVR, 27 of whom developed post-procedure pneumothorax and 32 of whom did not. Using Coreline software to analyze paired inspiratory and expiratory CT scans, investigators evaluated a range of metrics, including lobar volumes, fissure completeness, change in mean lung density, and functional air trapping (fAT), defined as the proportion of lung voxels demonstrating air retention between the 2 scans.

Among all evaluated parameters, functional air trapping specifically within emphysematous lung regions (fAT-E) emerged as the strongest predictor of post-BLVR pneumothorax. In the full cohort, fAT-E reached statistical significance (P =.017), with ROC curve analysis identifying an optimal threshold of approximately 25% (AUC 0.68; 67% sensitivity, 75% specificity). Total fAT across the whole lobe did not reach significance.

In an interview with HCPLive, Albaba noted that the analysis evolved after the abstract was submitted.2 Restricting the fAT-E analysis to higher-quality scans, defined as those with at least a one-liter volume change between inspiration and expiration, strengthened the signal considerably (P =.002; AUC 0.79), with specificity rising to 94% at a threshold of approximately 26.5%.1

"When we applied the functional air trapping just in the emphysema areas, not in the whole lung, not in the whole lobe, we found a very statistically significant prediction of pneumothorax," Albaba said.

Many BLVR candidates have 2 viable target lobes, with decisions currently informed by tools such as VQ scanning to assess relative perfusion. A validated fAT-based metric could add another dimension to that calculus—one oriented specifically around pneumothorax risk.

"If I target this lobe, is the chance of pneumothorax happening 50% as opposed to the other one, where there's 10%? That will probably take me more towards the latter target because there's less likelihood of pneumothorax happening, but I will still be able to get the same benefits of the volume reduction and the improvement in quality of life," Albaba said.

Beyond target selection, Albaba outlined a longer-term research question: whether very high fAT in emphysematous areas might predict persistent air leak, which is a more serious and less common outcome than pneumothorax itself. While most post-BLVR pneumothoraces resolve with chest tube drainage and patients are discharged without recurrence, a subset requires prolonged drainage, ultimately necessitating valve removal and forfeiture of procedure benefit. Identifying those patients before the procedure could inform patient selection decisions.

"Trying to identify patients using that metric…could be a future direction," Albaba said. "If somebody has very high functional air trapping in emphysematous areas, that may actually put them out of the [running for] this procedure, and maybe just look at other things that we can do for our COPD patients."

On the question of real-world accessibility, Albaba acknowledged that quantitative CT analysis software, including Coreline, remains unavailable at many institutions, though adoption is growing. He framed prospective validation as the prerequisite for broader clinical uptake.

"We will be able to prospectively validate, but we have to do that first before we can say that we can now just basically make it a standard of care or make it an available tool for physicians to use to predict pneumothorax before the procedure even happens," Albaba said.

Editor’s note: Albaba has no reported disclosures.

References

1. Albaba I, et al. (Poster Board # P354) Quantitative CT Predictors of Pneumothorax After Bronchoscopic Lung Volume Reduction: The Role of Air Trapping and Lobar Volume Interactions. Poster presented at: American Thoracic Society (ATS) International Conference 2026 on May 19 in Orlando, Florida

2. Albaba I, Deller E, Lalwani A, Dachert S, Criner G. Functional air trapping predicts pneumothorax after BLVR. Poster presented at American Thoracic Society International Conference 2026; May 16 –21; Orlando, FL. Poster P354.