January 10th, 2018
Physiological and Anatomical Differences between Children and Adults – cardiovascular system
Anatomical and physiological differences between children and adults also occur in the cardiovascular system. For instance, although after the fourth year the heart repositions downwards to the fifth intercostal space as the thorax elongates, before then, the heart is positioned in the fourth intercostal space midway between the buttocks and the head (Huelke, 1998). In addition, the heart’s width in relation to the chest varies in the infants, toddlers, and adults. Such positional variations may affect effectiveness of clinical evaluations such as providing a guide to the position where auscultation will be most effective (Howlin & Brenner, 2009).
Apart from such positional variation, children and adults also differ in respect to cardiac output. Cardiac output defines the per-minute volume of blood pumped by the heart to the rest of the body (Howlin & Brenner, 2009). Cardiac output is a factor of stroke volume, the per-contraction blood amount ejected from ventricles, and heart rate, which denotes “the number of heart beats per minute” (Howlin & Brenner, 2009, p. 26). The cardiac output in children and infants is determined by heart rate and not stroke volume due to underdeveloped heart muscle (Howlin & Brenner, 2009). Thus, during events such as stress, fever or respiratory distress, increases in cardiac output will come about through tachycardia, thus making heart rate a core marker of physiological state of the child (Howlin & Brenner, 2009). Another difference between children and adults is concerns their lower total blood volume (Raes, Aken, Craen, Donckerwolcke, & Walle, 2006), which may present challenges especially where injury leads to loss of blood.
Other anatomic and physiologic differences between children and adults concern the central nervous system. For instance, a child’s brain, at times up to the age of eight, comprises a massive frontal lobe, which accounts for a bulged and high forehead and a smaller facial portion (Huelke, 1998). Such a structure predisposes children to head injury compared to adults. The brain of a neonate is also a third the size of an adult’s, whereas the blood-brain barrier, a feature that averts the entry of substances (e.g. toxicants and drugs) into the central nervous system, is underdeveloped in children (Miller, et al., 2002). As such, exposure to chemicals will present a more potent danger to children as compared with adults. In infants and toddlers, the neuronal proliferation and migration, which starts in prenatal stages, continue with structural differentiation of neural pathways continuing up to adolescence (Miller, et al., 2002). Exposure to chemicals can significantly alter such processes resulting in impairments absent in adults.
Various differences between children and adults make it challenging to manage children’s conditions in the hospital or pre-hospital stages. Some of these differences are observed in the airway and respiratory system, cardiovascular system and the central nervous system. In the airways and respiratory system, aspects such as narrower airways, smaller-sized nostrils, thinner pharynx and larynx, slenderer nasopharynx, and shorter turbinate region may limit the use of equipment and approaches suitable for adults. In respect to the cardiovascular system, aspects such as variation in heart position, cardiac output determinants, and total blood volume differences necessitate special consideration when attending to paediatric clients. Concerning central nervous system, features such as large frontal lobe in infancy and early childhood, and underdeveloped brain-barrier in children of various ages, predispose children to heightened risk of head injury and chemical toxicity respectfully.
Howlin, F., & Brenner, M. (2009). Cardiovascular assessment in children: Assessing pulse and blood pressure. Paediatric Nursing, 22(1), 25-35.
Huelke, D. F. (1998). 42nd Annual proceedings association for the advancement of automotive medicine October 5-7: An overview of anatomical considerations of infants and children in the adult world of automobile safety design. Charlottesville, Virginia. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3400202/pdf/aam42_p093.pdf
Miller, M. D., Marty, M. A., Arcus, A., Brown, J., Morry, D., & Sandy, M. (2002). Differences between children and adults: implications for risk assessment at California EPA. International Journal of Toxicology, 21, 403-418, DOI:10.1080/1091581029009663 0
Raes, A., Aken, S.V., Craen, M., Donckerwolcke, R., & Walle, J. V. (2006). A reference frame for blood volume in children and adolescents. BMC Pediatrics, 6(3), doi:10.1186/1471-2431-6-3
Santillanes, G., & Gausche-Hill, M. (2008). Pediatric airway management. Emerg Med Clin N Am, 26, 961-975, doi:10.1016/j.emc.2008.08.004
Xi, J., Si, X., Kim, J. W., & Berlinski, A. (2011). Simulation of airflow and aerosol deposition in the nasal cavity of a 5-year-old child. Journal of Aerosol Science, 42, 156-173. doi:10.1016/j.jaerosci.2010.12.004