Table 5. Diameters and areas of tracheal cannulae, and proportion of obstruction.

	Tracheal cannula
Inner bore, mm	7	7.5	8	8.5	9
Area, mm2	38.5	44.2	50.3	56.7	63.6
Cannula area ratio obstructed,%
BF-P160*	49	43	38	33	30
BF-XT160†	81	71	62	55	49

* diameter: 4.9mm; área: 18.8mm²; ^† diameter: 6.3mm; area 31.2 mm².