Adult Lungs Capable of Sprouting New Growth

After surgery and chemotherapy, her lung capacity had dropped substantially from a baseline of at least 100% forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC), down to 35% and 49% of the predicted value, respectively.

By the end of a 15-year follow-up period, progressive improvements in spirometry brought the FEV1 back up to 60% and FVC to 73%, representing 51% and 35% relative improvements, respectively, compared with the expected 11% and 9% declines expected with aging. Annual surveillance computerized tomography (CT) imaging showed that the remaining lung progressively enlarged, herniating partially into the right hemithorax. The lung expansion included both gas and total lung volume increases along with a gradual, sustained rise in tissue volume to about double what it had been immediately after the surgical resection.

An experimental magnetic resonance imaging (MRI) scan using hyperpolarized helium-3 gas to measure apparent diffusion of inhaled gas showed dimensions in the part of the airways where the alveoli that were consistent with a 64% increase in the number of alveoli, rather than in the size of existing alveoli. The alveolar depth in the growing lung, though, was shallower than in normal lungs (70 µm versus 138). The study was published in the July 19, 2012, issue of the New England Journal of Medicine (NEJM).

“Factors that may have contributed to the growth were the relatively young age of the patient at the time of surgery and stretching of the lung from postpneumonectomy syndrome and exercise. After getting a prosthetic volume expander in the right lung cavity to ease dyspnea at 18 months, the patient exercised daily with a regimen of walking, cycling, and yoga,” concluded lead author Steven Mentzer, MD, and colleagues. “We hypothesize that reminiscent of the role of stretch in lung development, cyclic stretch as such may be an important trigger for new lung growth.”

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