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This week's question will focus on some of the differences between the airway of the newborn and the adult.
1.  Newborns are obligate nasal or oral breathers?
2.  The tongue of the newborn is relatively larger or smaller in the normal newborn compared to the normal adult?
3.  The head of the normal newborn is relatively larger or smaller compared to the adult?
4.  The larynx of the normal newborn is located at cervical vertebrae # __, while the larynx of the normal adult is located at cervical vertebrae # __.
5.  The epiglottis of the newborn is softer or stiffer than the adult?
6.  The narrowest portion of the newborn's upper airway is the ______?
7.  The vocal cords of the newborn are more or less anteriorly angled than in the adult?

本周重点讨论新生儿与成人的呼吸道差异：
1.  新生儿通过口还是鼻呼吸？
2.  与正常成人相比，正常新生儿的舌体相对较大还是较小？
3.  与正常成人相比，正常新生儿的头颅相对较大还是较小？
4.  正常新生儿喉部位于第几颈椎？成人呢？
5.  与成人相比，新生儿的会厌柔软还是僵硬？
6.  新生儿上呼吸道最狭窄部分位于何处？
7.  与成人相比，新生儿的声带前倾角度更大还是更小？

参考答案：

1.  新生儿通过口还是鼻呼吸？
新生儿通过鼻呼吸。

2.  与正常成人相比，正常新生儿的舌体相对较大还是较小？
与正常成人相比，正常新生儿的舌体相对较大。

3.  与正常成人相比，正常新生儿的头颅相对较大还是较小？
与正常成人相比，正常新生儿的头颅相对较大。

4.  正常新生儿喉部位于第几颈椎？成人呢？
正常新生儿喉部位于第3-4颈椎，成人位于第6-7颈椎，因此，新生儿喉部相对成为位置更靠前，更偏向头侧。

5.  与成人相比，新生儿的会厌更柔软还是坚硬？
与成人相比，新生儿的会厌更坚硬。

6.  新生儿上呼吸道最狭窄部分位于何处？
环状软骨。

7.  与成人相比，新生儿的声带前倾角度更大还是更小？
与成人相比，新生儿的声带前倾角度更大。

教科书[1]提醒在复苏期间或全麻诱导期间，应避免新生儿头部过度屈曲或过伸，因为可导致呼吸道梗阻。但是有研究数据对该内容提出了异议。Wheeler等[2]对全麻气管插管下的健康婴儿处于中立位、伸展位、屈曲位的气管直径进行了测量，通过纤维支气管镜、计算机数字化技术测量后前位、侧位和横截面。即使头部处于极度屈曲或伸展位，作者也未发现有气管梗阻。因为气管导管位于声门下，该研究未对声门上呼吸道直径进行测量。此外，研究只选择了10名婴儿，且全部健康。

Newborns are obligate nasal or oral breathers?
Newborns are obligate nasal breathers.

The tongue of the newborn is relatively larger or smaller in the normal newborn compared to the normal adult?
The tongue of the newborn is relatively larger in the normal newborn compared to the normal adult.

The head of the normal newborn is relatively larger or smaller compared to the adult?
The head of the normal newborn is relatively larger compared to the adult.

The larynx of the normal newborn is located at cervical vertebrae # __, while the larynx of the normal adult is located at cervical vertebrae # __.
The larynx of the normal newborn is located at cervical vertebrae C 3-4 , while the larynx of the normal adult is located at cervical vertebrae C 6-7 . Hence, the larynx of the newborn is more cephalad and anterior than that of the adult.

The epiglottis of the newborn is softer or stiffer than the adult?
The epiglottis of the newborn is stiffer than the adult.

The narrowest portion of the newborn's upper airway is the _____?
The narrowest portion of the newborn's upper airway is the cricoid.

The vocal cords of the newborn are more or less anteriorly angled than in the adult?
The vocal cords of the newborn are more anteriorly angled than in the adult.

Standard teaching (1) cautions against extreme extension or flexion of a newborn's head during resuscitation or induction of general anesthesia, since it its believed that airway obstruction may result. However, data supporting this contention is scarce. Wheeler et al. (2) examined the dimensions of the tracheal lumen in neutral, extended, and flexed head positions in healthy infants undergoing general endotracheal anesthesia. Using a bronchoscopic, computer-digitized technique the investigators measured anterior-posterior and lateral dimensions and cross sectional area. The authors were unable to demonstrate obstruction at the level of the trachea, even with extreme position of the head. Interestingly, infants were as equally likely to have a small increase as they were to have a small decrease in tracheal dimension with changes in head position. Of note, since the endotracheal tube was placed just below the level of the vocal cords, this study did not examine changes in airway dimensions above the level of the glottis. Additionally, only 18 infants were studied, and all were healthy.

References:
1.  Standards and guidelines for cardiopulmonary resuscitation and emergency cardiac care. JAMA 1986;255:2905-87.
2.  Wheeler M, Roth AG, Dunham ME, Rae B, Cote CJ. A bronchoscopic, computer assisted examination of the changes in dimension of the infant tracheal lumen with changes in head position. Anesthesiology 1998;88:1183-7


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