Developmental anatomy of the airway

The airway begins to develop from the primitive foregut at 4 weeks' gestation. Congenital anomalies may result when this process is abnormal. The anatomy of the airway at birth is uniquely different from older children and adults with a large tongue, long floppy epiglottis, large occiput, cephalad larynx, and narrow cricoid cartilage. These features affect the technique required for endotracheal intubation and facemask ventilation. A neutral head position and straight bladed laryngoscope are usually used. Neonates are also obligate nasal breathers and simultaneously suckle and breathe. Minute volume is rate-dependent and the highly compliant chest easily displays sternal and intercostal recession during respiratory distress, and early onset of fatigue. From the neonatal period onwards the anatomy gradually begins to resemble that of adults. The cricoid descends caudally, the epiglottis becomes firmer and shorter, and the large occiput recedes. By 8–10 years the airway is anatomically adult in most ways other than absolute size. The ‘sniffing the morning air’ and curved laryngoscope become appropriate for endotracheal intubation. Conventionally, uncuffed endotracheal tubes have been used in children; however high volume-low pressure cuffed tubes are now available, allowing monitoring of the cuff pressure intermittently throughout use.