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The Neonatal Neuromechanical Unit: Generalities of Operation

  • Jacopo P. MortolaEmail author
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Abstract

Many examples could be offered to illustrate the concept that the respiratory physiology of the newborn is markedly distinct from that of the adult. Some of the differences are determined by body size, others by the stage of development and maturation, and others yet by the tumultuous events accompanying birth. With respect to body size, the newborn’s small body mass reduces the heat capacitance of the body and the high body surface-to-volume ratio favors heat loss. Hence, a large weight (W)-specific metabolic rate is required to offset the propensity for hypothermia. This translates into high values of oxygen uptake (\( {\dot{V}}_{{\mathrm{O}}_2}/\mathrm{kg} \)), which imply a proportionally large pulmonary ventilation (\( {\dot{V}}_{\mathrm{E}} \)), achieved mostly by breathing at high rates. Indeed, fast breathing is a common characteristic of all newborn mammals. With respect to maturation, the development of the lung and respiratory apparatus is never completed at birth, even in the most precocial species. The lungs continue to grow postnatally, in a centripetal direction, with formation of peripheral airways and alveoli, implying that in newborns the central airways comprise a larger proportion of the total air space and contribute to a relatively large anatomical dead space. The incomplete myelinization and low conduction velocity of neural fibers, including those of the laryngeal, vagi, and carotid sinus nerves, limit the afferent sensory information involved in the regulation of breathing. Finally, with respect to the adaptation to air breathing at birth, a multitude of events among the most dramatic of the whole life occur quite rapidly, such as the transition from filtration to absorption of the pulmonary fluid, the drastic changes in pulmonary circulation, and the rise in oxygenation with its implications on the function of the chemoreceptors.

Keywords

Sudden Infant Death Syndrome Respiratory Muscle Carotid Body Functional Residual Capacity Breathing Pattern 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Authors and Affiliations

  1. 1.Department of PhysiologyMcGill UniversityMontrealCanada

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