FirstExhalation

Exhalation before the first breath?

Prevailing opinion holds that opening of the alveoli is a passive response to

movements of the diaphragm in the newborn infant – an initial respiratory

effort made immediately following birth in the healthy child. Jäykkä's

experiments included simulation of diaphragm movement, along with

ventilation of one lung and ventilation plus fluid filling of the capillary bed of

the other.

Jäykkä used the un-inflated (atelectatic) lungs of fetuses that had died before

birth. Injection of fluid (macrodex solution) into the pulmonary artery of one

lung resulted in expansion of the alveoli of that lung. Expansion occurred first

in the most distal alveoli, with expansion in three stages of the more proximal

alveoli toward the center of the lung – before initial function of the bronchial

airway the alveoli deepest in the lungs were first to inflate! Consider the

added effect of carbon dioxide released by hemoglobin to be exhaled from

these newly opened alveo

li.

An initial exhalation may precede the first breath.

Carbon dioxide from the circulation may perhaps initiate inflation of the

alveoli. If circulation to and from the placenta is abruptly clamped off, where

will the blood needed for the lungs come from? The lungs take priority at

birth. If the blood needed is drained from the brain, the result may be the

kind of ischemic damage found in monkeys subjected to asphyixa at birth --

and with an Apgar score of 10.

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