Table 2.

Pressure drop characteristics of tested and control endotracheal tubes at 60 L/minute.

Type of endotracheal tube	n	Mean pressure drop	Standard deviation	Min. pressure drop	Max. pressure drop	t-test value vs. control	p value	t-test value vs cleared tube	p value
All endotracheal tubes
All controls	3	10.8	0.27			n/a		−8.63	<0.001
Extubated, not cleared (pre)	40	21.8	13.30	10.2	77.8	5.27	<0.001	4.80	<0.001
Extubated, cleared (post)	40	11.8	0.29	9.5	16.8	−8.63	<0.001	n/a
7.0 mm diameter
Control	1	14.5	0.14			n/a		−3.69	0.035
Extubated, not cleared (pre)	4	19.2	1.88	16.4	20.4	4.94	0.016	5.20	0.014
Extubated, cleared (post)	4	15.9	0.75	15.0	16.8	−3.69	0.035	n/a
7.5 mm diameter
Control	1	11.8	0.01			n/a		−3.30	0.004
Extubated, not cleared (pre)	17	24.1	9.12	12.0	46.0	4.33	<0.001	4.13	0.001
Extubated, cleared (post)	17	12.5	0.86	11.4	14.3	−3.30	0.004	n/a
8.0 mm diameter
Control	1	9.1	0.04			n/a		−10.76	<0.001
Extubated, not cleared (pre)	19	23.0	17.42	10.2	77.8	3.55	0.002	3.23	0.004
Extubated, cleared (post)	19	10.3	0.48	9.5	11.3	−10.76	<0.001	n/a