Lung growth and aging

Neonate exhales incompletely

Neonate exhales incompletely, thus elevating the FRCYou will recognize the breathing pattern of a neonate you saw earlier. At certain moments in time the end-expiratory level is higher than average. Also, now and then ventilation just seems to cease; during the expiratory pause the lung deflates to a low volume. In the latter case the neonate's muscles are quite relaxed. These phenomena give away that in the neonate end-expiratory lung volume is normally grater than that obtained when the muscles are relaxed, and thus different from the volume at elastic equilibrium. The elevated end-expiratory lung volume (the FRC) is achieved by 2 mechanisms:

These are very useful mechanisms, because at higher end-expiratory lung volume there will be fewer lung compartments that do not contribute much to gas exchange due to occluded airways during (part of the) expiration.

Conclusion

In newborns hypoxemia due to breathing at a low lung volume at which airway closure occurs, is minimized by:

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