Positive end-expiratory pressure induced changes in airway driving pressure in mechanically ventilated COVID-19 Acute Respiratory Distress Syndrome patients

Table 2 Respiratory mechanics and EIT data

Respiratory mechanics	J-shaped n = 126	U-shaped n = 40	Inverted J-shaped n = 18	p value
Tidal volume, mL/kg of IBW (mean, sd)	6.03 ± 0.03	5.86 ± 0.92	5.97 ± 0.14	0.098
Baseline Crs, mL/cmH₂O (mean, sd)	33.47 ± 7.25^a	29.24 ± 8.70^a,b	25.64 ± 8.45^b	< 0.001
Baseline dP_aw, cmH₂O (mean, sd)	12.65 ± 2.66^a	13.21 ± 3.94^a,b	15.03 ± 3.72^b	< 0.05
Baseline PaO₂/FiO₂, mmHg (mean, sd)	139.32 ± 52.67^a	120.72 ± 57.68^a,b	92.43 ± 40.43^b	< 0.05
PEEPmin_dP_aw, cmH₂O (median, IIQ)	7.52 ± 1.9^a,c	12.2 ± 2.64^a,b	14.6 ± 2.38^b,c	< 0.001

EIT assessment	N = 28	N = 12	N = 1
Hyperdistention at the optimal PEEP, % (mean, sd)	1.58 ± 2.34	6.34 ± 10.22	1.3 ± 0	0.071
AUC for hyperdistention, %.cmH₂O (mean, sd)	216.75 ± 81.44^a	116.17 ± 77.53ª	6.3 ± 0	< 0.001
Collapse at the optimal PEEP, % (mean, sd)	13.86 ± 13.38	10.81 ± 10.38	0.0 ± 0	0.473
AUC for collapse, %.cmH₂O (mean, sd)	96.95 ± 70.40^a	149.42 ± 95.54^a	418 ± 0	< 0.001
EIT optimal PEEP, cmH₂O, (mean, sd)	9.17 ± 2.53^a	12.96 ± 3.29ª	14.22 ± 0	< 0.001

Continuous variables are expressed as mean and standard deviation or median and interquartile range, according to normality distribution. A one-way ANOVA or the Kruskal–Wallis test was used for the comparison between three groups with a respective post hoc analysis. A t-test was used for the comparison between pairs. The letters a, b and c express values that are statistically different. IBW, ideal body weight; Crs, respiratory system compliance; dP_aw, airway driving pressure; PaO₂/FiO₂, ratio of partial pressure of arterial oxygen and fraction of inspired oxygen; PEEPmin_dP_aw, lowest PEEP that minimized dP_aw; PEEP, positive end-expiratory pressure; EIT, electrical impedance tomography; AUC, area under the curve

ISSN: 1364-8535