Table 3. Summary of the reference equations of IO indices for adults.
| Equations | Area | N | F/M | Age range (years) | Ethnicity | Predictors | ||||
|---|---|---|---|---|---|---|---|---|---|---|
| Sex | R5 | R20 | X5 | fres | ||||||
| Present study | China | 567 | 1.10 | 18–82 | 99.3% Han | M | –H, W | –H, W | H, A | –H, W |
| F | –H, W, –A | –H, | H, A | –H, W | ||||||
| Vogel et al. (9), 1994 | Germany | 506 | 0.70 | 18–69 | NA | M | A | A | –A | NA |
| F | A | A | –A | NA | ||||||
| Zhao et al. (11), 2002 | Xinjiang, China | 457 | 0.80 | 16–81 | Han, Uygur | M | W, –H | W, –H, –A | H | W, –H |
| F | W, –H | –H, –A | H, W | W, –H | ||||||
| Fang et al. (12), 2005 | Kunming, China | 185 | 0.73 | 19–68 | NA | M | –W *H | –W *H | NA | –eH |
| F | –eW | –eW | NA | –LogH, LogW | ||||||
| Shiota et al. (13), 2005 | Japan | 166 | 1.40 | 20–83 | NA | – | –LogH | –LogH | LogH, –A | – |
| Ni et al. (14), 2006 | Nantong, China | 120 | 0.69 | 20–79 | Han | M | –H, W, A | –H, W, A | H, W, A | H, W, A |
| F | H, W, A | H, W, –A | H, W, A | H, W, A | ||||||
| Newbury et al. (15), 2008 | Australia | 125 | 1.12 | 25–74 | Caucasian | M | –H, W, –A | –H, W, –A | H, A | NA |
| F | –H, A | –H, A | H, –A | NA | ||||||
| Wang et al. (16), 2011 | Shenyang, China | 100 | 0.69 | 19–80 | NA | M | –lgH, –lgA | –H2, –eA | –A2 | A2 |
| F | –lgH | –H2 | H2, –eA | –lgH, A*W | ||||||
| Li et al. (26), 2012 | Lanzhou, China | 920 | 1.04 | >18 | NA | M | –lgH, W | –H, W | –A2 | –H, W |
| F | –H, W | W | –A2 | –H, W | ||||||
| Schulz et al. (18), 2013 | Germany | 397 | 1.58 | 45–85 | Caucasian | M | –H, W, –A | –H, W, –A | H, –W, –A | –H, W, A |
| F | –H, W, –A | –H, W, –A | H, –W, –A | –H, W, A | ||||||
| Zhang et al. (19), 2015 | Macau, China | 362 | 1.02 | 18–78 | Han | M | W, –H | –H | H | A, –H |
| F | CW, –W, A | –H | H, A | A, CW, –W | ||||||
| Shu et al. (20), 2016 | Jianghan Plain, China | 431 | 1.03 | 18–79 | NA | M | –AH, A, –A2, eW, –eA | –AH, A, –A2, –lgA | A*H, –A | –H2, W2 |
| F | –H2, W, –eW | W, –H2 | H2 | W, –H2, –eW | ||||||
H, W, A respectively indicate height, weight and age as predictors of the equations; “–” indicates a negative effect of the predictor; M: equations for males; F: equations for female. IO, impulse oscillometry; N, the number of the study sample; F/M, ratio of female subjects to male subjects; R5, resistance at 5 Hz; R20, resistance at 20 Hz; X5, reactance at 5 Hz; fres, resonant frequency; NA, information was not available in the published paper.