Table 3 Whole lung particle deposition patterns (C/P ratio), particle retention values and change in retention values as a function of time after inhalation

	C/P ratio	Whole lung particle retention				Change in retention
	C/P ratio	Average retention in first 120 min	120 min	Post-SI	24 h	0–50 min	50–120 min	120 min to post-SI	Post-SI to 24 h
Normal (n = 8)	1.52 (1.30 to 1.74)	0.93 (0.87 to 0.99)	0.81 (0.71 to 0.91)	0.64 (0.55 to 0.72)	0.60 (0.52 to 0.69)	0.09 (−0.003 to 0.17)	0.11 (0.05 to 0.17)	0.18 (0.10 to 0.25)	0.03 (−0.01 to 0.07)
Asthmatic (n = 10)	1.83 (1.48 to 2.17)	0.81* (0.75 to 0.88)	0.71 (1.61 to 0.80)	0.49† (0.36 to 0.61)	0.43† (0.33 to 0.53)	0.19 (0.13 to 0.27)	0.10 (0.07 to 0.14)	0.25† (0.21 to 0.29)	0.05† (0.02 to 0.09)
p Value	0.146	0.004	0.083	0.027	0.015	0.021	1.000	0.093	0.200

C/P ratio, central to peripheral ratio; SI, sputum induction. Values represent the mean (95% confidence interval). Retention of inhaled sulphur colloid particles was significantly lower in subjects with asthma, due partially to more rapid clearance of particles during the initial 50 min after inhalation. More central particle deposition (ie, higher C/P ratio) in subjects with asthma probably contributed to the more rapid particle clearance.
*Significant correlation with C/P ratio (r = −0.78, p = 0.01).
†n = 9 (retention values beyond 120 min were not included for one subject with asthma who could not produce a sputum sample).