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

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