Functional morphometry for the estimation of the alveolar surface area in prematurely-born infants

Conventionally, the alveolar surface area (SA) has been measured by using post-mortem morphometry. Such studies have highlighted that SA in prematurely-born infants is markedly smaller when compared to term-born infants as a result of postnatal impairment or arrest of alveolar development. We herein explore how, non-invasive measurements of the ventilation/perfusion ratio (VA/Q) can be used to estimate SA in prematurely-born surviving, convalescent infants. We also compare SA in prematurely-born infants measured at term-corrected age, to term-born infants using previously published datasets of VA/Q. Fick's first law of diffusion is employed for the conversion of VA/Q measurements to SA values after correcting for differences in pulmonary perfusion, thickness of the respiratory membrane and alveolar-arterial gradient. We report that SA is fivefold smaller in prematurely-born compared to term-born infants. We conclude that non-invasive measurements of VA/Q can be used for the functional estimation of SA which could, in turn, be used as a future outcome measure in respiratory studies of prematurely-born infants.