The conventional view is that lung growth and development ends around age 7 but a fascinating article in last week's NEJM (N Engl J Med 2012; 367:244-247July 19, 2012) suggests that lung growth can occur in adults.
A 33-year-old woman underwent a right-sided pneumonectomy in 1995 for treatment of a lung adenocarcinoma. As expected, there was an abrupt decrease in her vital capacity, but unexpectedly, it increased during the subsequent 15 years. Serial computed tomographic (CT) scans showed progressive enlargement of the remaining left lung and an increase in tissue density. Magnetic resonance imaging (MRI) with the use of hyperpolarized helium-3 gas showed overall acinar-airway dimensions that were consistent with an increase in the alveolar number rather than the enlargement of existing alveoli, but the alveoli in the growing lung were shallower than in normal lungs. This study provides evidence that new lung growth can occur in an adult human.
Over the 15 year follow-up following right pneumonectomy, spirometry showed a 50% increase in FEV1 and 35% increase in FVC (versus a predicted age-related decrease in both parameters). In addition, serial surveillance CT scans over the same period showed a gradual increase in tissue volume in the left lung, nearly doubling after surgery. I know it sounds like I'm gushing but the 3-dimensional CT reconstructions of the remaining left lung are just COOL!
But what is really orbital about this brief report is the use of a diffusion MRI study with "hyperpolarized helium-3 gas" to derive a quantitative estimate of acinar microstructure--and thus the development of new septae and evidence for lung regeneration. It took when a couple passes through this section to unwrap the radiology technique and how it relates to a microanatomical dimension (I'm somewhat embarassed to admit)--but check this out. The references on this technique are only a couple of years old, so this is some really cutting edge stuff.
Whether this unique case can be generalized would be an interesting study. The patient was very young when she was diagnosed with lung cancer and apparently had a robust daily exercise regimen--certainly not the typical lung cancer patient. But the evidence presented here is a credible challenge to a long-held assumption that adult lungs do not grow.
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