Table 3.
Electrical Impedance Tomography-derived Measures
| HFNO | Helmet CPAP | Helmet NIV |
P value* HFNO vs. CPAP |
P Value† HFNO vs. NIV |
P value‡ CPAP vs. NIV |
|
|---|---|---|---|---|---|---|
| Tidal impedance variation, arbitrary units§ | 913 (781–1,294) | 1,775 (1,289–2,788) | 1,411 (1,047–1,842) | 0.002 | 0.02 | 0.32 |
| Ventral ROI | 53 (33–74) | 54 (38–82) | 64 (31–95) | >0.99 | >0.99 | >0.99 |
| Midventral ROI | 255 (205–521) | 399 (301–667) | 374 (184–605) | 0.03 | >0.99 | 0.20 |
| Middorsal ROI | 455 (343–618) | 944 (680–1,062) | 770 (468–910) | 0.001 | 0.03 | 0.17 |
| Dorsal ROI | 163 (124–181) | 325 (260–427) | 254 (171–368) | 0.001 | 0.02 | 0.51 |
| Quasistatic lung compliance, arbitrary units/cm H2O§ | 132 (64–143) | 153 (84–239) | 121 (77–190) | 0.16 | >0.99 | >0.99 |
| Quasistatic ventral ROI compliance | 5 (3–10) | 5 (3–8) | 5 (4–9) | >0.99 | >0.99 | >0.99 |
| Quasistatic midventral ROI compliance | 34 (17–51) | 37 (21–68) | 29 (19–70) | 0.82 | >0.99 | >0.99 |
| Quasistatic middorsal ROI compliance | 56 (35–72) | 90 (42–115) | 61 (33–107) | 0.10 | 0.96 | >0.99 |
| Quasistatic dorsal ROI compliance | 17 (10–28) | 27 (16–36) | 19 (12–32) | 0.10 | 0.98 | >0.99 |
| Pendelluft effect, % of tidal impedance variation | 55 (25–68) | 31 (11–44) | 26 (8–44) | 0.01 | 0.004 | 0.16 |
| Estimated EELI, arbitrary units | 1,809 (873–1,964) | 5,028 (3,051–6,738) | 4,301 (2,363–6,358) | 0.001 | 0.001 | 0.47 |
| Estimated EELI, ventral ROI | 45 (17–61) | 141 (69–229) | 95 (70–207) | 0.001 | 0.001 | >0.99 |
| Estimated EELI, midventral ROI | 509 (317–649) | 1,490 (948–2,242) | 1,161 (686–2,021) | 0.001 | 0.001 | 0.29 |
| Estimated EELI, middorsal ROI | 908 (522–1,037) | 2,707 (1,739–3,396) | 2,103 (1,201–3,273) | 0.001 | 0.001 | >0.99 |
| Estimated EELI, dorsal ROI | 221 (154–328) | 712 (523–898) | 581 (332–847) | 0.001 | 0.001 | 0.17 |
| Dynamic lung strain | 0.64 (0.56–0.76) | 0.41 (0.29–0.66) | 0.50 (0.31–0.67) | 0.01 | 0.05 | >0.99 |
| Regional dynamic strain, ventral ROI | 1.14 (0.93–1.8) | 1.54 (0.95–2.5) | 1.79 (0.81–3.06) | 0.30 | 0.24 | 0.52 |
| Regional dynamic strain, midventral ROI | 0.60 (0.55–0.89) | 0.97 (0.70–1.49) | 0.96 (0.48–1.38) | 0.06 | 0.25 | 0.99 |
| Regional dynamic strain, middorsal ROI | 0.62 (0.43–0.77) | 0.33 (0.20–0.52) | 0.37 (0.23–0.57) | 0.007 | 0.16 | 0.68 |
| Regional dynamic strain, dorsal ROI | 0.67 (0.57–0.96) | 0.43 (0.23–0.64) | 0.49 (0.28–0.60) | 0.03 | 0.01 | >0.99 |
| Overstretched pixels,ǁ global, % | 4 (3–9) | 1 (1–3) | 2 (1–3) | 0.02 | 0.40 | 0.50 |
| Overstretched pixels, ventral ROI, % | 20 (16–27) | 9 (6–16) | 10 (4–17) | 0.006 | 0.07 | >0.99 |
| Overstretched pixels, midventral ROI, % | 3 (1–9) | 1 (0–2) | 1 (0–3) | 0.23 | >0.99 | 0.11 |
| Overstretched pixels, middorsal ROI, % | 1 (0–7) | 0 (0–1) | 0 (0–0) | 0.09 | 0.21 | >0.99 |
| Overstretched pixels, dorsal ROI, % | 3 (1–9) | 0 (0–1) | 0 (0–1) | 0.01 | 0.49 | 0.64 |
Definition of abbreviations: CPAP = continuous positive airway pressure; EELI = end-expiratory lung impedance; HFNO = high-flow nasal oxygen; NIV = noninvasive ventilation; ROI = region of interest.
Data are reported as the median (interquartile range). All paired comparisons were adjusted with Bonferroni’s or Dunn’s correction, as appropriate. P values ⩽ 0.05 are considered statistically significant.
Comparison between HFNO and helmet CPAP.
Comparison between HFNO and helmet NIV.
Comparison between helmet CPAP and helmet NIV.
All calculations are based on pixel-by-pixel analysis of the electrical impedance tomography signal. Vt and compliance calculated as the absolute difference between end-inspiratory and end-expiratory lung impedance, which does not take into account the regional inflation/deflation due to pendelluft, is displayed in Table E1.
Overstretched pixels are defined as those with a dynamic strain > 2.