TABLE 1

Characteristics of included studies that developed reference equations for oscillometric parameters of interest

Study	Study country	Study population	Oscillometry device(s)	Signal type	Frequencies considered (Hz)	Reference parameters	Smoker inclusion
*Shiota et al. [22]*	Japan	Non-Caucasian	MasterScreen IOS	Recurrent impulses	5, 20	R₅, R₂₀, X₅	Never-smokers, active smokers, ex-smokers
*Newbury et al. [20]*	Australia	Caucasian	MasterScreen IOS	Recurrent impulses	5, 10, 15, 20, 25, 35	Z₅, R_rs, X_rs	Never-smokers, ex-smokers
*Brown et al. [18]*	Australia	Caucasian	Custom-made	Pseudorandom	6, 11, 19	R_rs, X_rs	Never-smokers, ex-smokers
*Aarli et al. [24]*	Norway	Caucasian	MasterScreen IOS	Recurrent impulses	5, 20	R₅, R₂₀, X₅, Fres, AX	Never-smokers, ex-smokers
*Schulz et al. [23]*	Germany	Caucasian	MasterScreen IOS	Recurrent impulses	5, 20	Z₅, R₅, R₂₀, R_5–20, X₅, Fres, AX	Never-smokers only
*Oostveen et al. [16]*	Belgium, the Netherlands, Hungary, Australia	Caucasian	Custom-made (C1, C3), ROS Oscilink (C2), Quark i2m (C4), MasterScreen IOS (C5)	Pseudorandom (C1–C4), recurrent impulses (C5)	4, 5, 6, 8, 10, 12, 14, 15, 16, 18, 20, 22, 24, 26	R_rs, R_m, X_rs, Fres, AX	Never-smokers, ex-smokers
*Ribeiro et al. [21]*	Brazil	Caucasian, Non-Caucasian	Custom-made	Pseudorandom	4, 6, 8, 10, 12, 14, 16, 18, 20, 22	Z_rs, R_rs, R_m, R₀, X_rs, Fres, Xm	Never-smokers only
*De et al. [19]*	India	Non-Caucasian	Resmon Pro	Pseudorandom, relative primes	5, 19	R₅, R₁₉, R_5–19, X₅	Never-smokers only
*Moitra et al. [15]*	India	Non-Caucasian	MasterScreen IOS	Recurrent impulses	5, 20	Z₅, R₅, R₂₀, R_5–20, X₅, Fres, AX	Never-smokers only
*Berger et al. [17]*	USA	Caucasian	MasterScreen IOS	Recurrent impulses	5, 10, 15, 20	R₅, R₁₀, R₁₅, R₂₀, R_5–15, R_5–20, X₅, X₁₀, Fres, AX	Never-smokers only

IOS: impulse oscillometry; R₅: resistance at 5 Hz; R₂₀: resistance at 20 Hz; X₅: reactance at 5 Hz; Z₅: impedance at 5 Hz; R_rs: respiratory resistance; X_rs: respiratory reactance; Fres: resonant frequency; AX: reactance area; R_m: mean respiratory resistance; R₀: resistance at 0 Hz; R₁₉: resistance at 19 Hz.