TABLE 1

Influence of leak location and breathing cycle on functional residual capacity (FRC) and lung clearance index (LCI): overview of the influence of continuous leaks on FRC and LCI applied at different locations and phases of the breath cycle

	Pre-capillary	Intra-capillary		Post-capillary
	Pre-capillary	Side-stream	Main-stream	Post-capillary
Inspiratory	FRC ↑^#	NA^¶	FRC ↑^#	FRC ↑^#
Inspiratory	LCI ↑^#	NA^¶	LCI ↑^#	LCI ↑^#
Expiratory	FRC ↓	NA^¶	FRC ↓	FRC –
Expiratory	LCI –/↓⁺	NA^¶	LCI –	LCI –
Inspiratory and expiratory	FRC ↑^#	FRC ↑^#	FRC ↑^#	FRC ↑^#
Inspiratory and expiratory	LCI ↑^#	LCI ↑^#	LCI ↑^#	LCI ↑^#

Arrows indicate the direction of change of FRC and LCI from baseline values. NA: not applicable. ^#: in continuous leaks of a certain size, the end of washout criteria were not reached, and FRC and LCI could not be calculated; ^¶: side-stream leaks are independent of inspiration and expiration as there is a constant flow into the side-stream and results are similar to inspiratory and expiratory leaks; ⁺: the change in LCI following pre-capillary expiratory leaks is dependent on when the leak was applied during the washout (further details provided in table 2).