Individualization of PEEP and tidal volume in ARDS patients with electrical impedance tomography: a pilot feasibility study

Annals of Intensive Care

Table 2 Ventilator data and physiological parameters after mechanical ventilation according to the ARDS Network protocol low positive end-expiratory pressure (PEEP) table (ARDSNet) and after 4 h of mechanical ventilation according to the electrical impedance tomography based protocol (EIT Protocol)

Parameter (unit)	ARDSNet	EIT Protocol	p
Stress (mbar)	14.1 ± 3.9	17.2 ± 4.4	0.0007
Strain_release (ratio)	0.80 [0.70–1.10]	1.13 [0.96–1.59]	0.015
E_lung,spec (mbar)	15.9 ± 5.8	14.2 ± 4.8	0.26
Strain_recr. (ratio)	0.56 ± 0.14	0.55 ± 0.19	0.77
PaO₂/FiO₂ (mmHg)	151 ± 31	209 ± 53	0.0001
PaCO₂ (mmHg)	58 ± 11	61 ± 9	0.28
pH	7.31 ± 0.07	7.29 ± 0.05	0.17
V_T (ml/kg PBW)	5.8 ± 0.47	5.7 ± 0.92	0.96
P_aw.plat (mbar)	20.3 [18.5–22.4]	27.9 [25.4–29.1]	0.0001
PEEP (mbar)	10 [8–10]	16.5 [14–18]	0.0001
C_rs (ml/mbar)	38.2 ± 8.8	37.9 ± 11.4	0.83
V_PEEP (ml)	348 [311–457]	603 [400–809]	0.0004
C_lung (ml/mbar)	60.07 ± 23.48	63.53 ± 26.38	0.33
ΔP_aw (mbar)	10.4 ± 2.2	10.4 ± 2.0	0.96
ΔP_TP (mbar)	7.0 ± 2.3	6.6 ± 2.1	0.19
SD_RVD (%)	8.3 ± 2.8	6.6 ± 1.9	0.022
P_tp,plat (mbar)	4.9 [1.4–6.9]	17.9 [15.6–19.0]	< 0.0001
P_tp,exp (mbar)	-3.5 [-5.9–1.1]	3.25 [-0.7–4.7]	0.0002
Tidal power (J/min)	4.96 ± 1.87	4.24 ± 1.24	0.047
EELV (ml)	1637 [1450–2228]	2348 [2034–3201]	< 0.0001
FRC_release (ml)	1176 ± 439	1317 ± 443	0.17
FRC_recr. (ml)	1267 [1141–1803]	1704 [1496–2512]	0.0001
Cardiac Index* (l/min/m²)	3.4 [2.4–4.5]*	3.4 [2.5–5.0]*	0.19*
NE (µg/kg/min)	0.12 [0.01–0.26]	0.12 [0.01–0.26]	0.55

Normally distributed variables are presented as mean ± standard deviation, whereas non-normally distributed variables are presented as median [interquartile range]
PaO₂ arterial partial pressure of oxygen, FiO₂ inspired fraction of oxygen, C_rs respiratory system compliance, C_lung lung compliance, ΔP_aw airway driving pressure, ΔP_TP transpulmonary driving pressure, NE norepinephrine dosage, P_aw.plat airway plateau pressure, PEEP positive end-expiratory pressure (measured at airway opening), V_PEEP PEEP volume (calculated by multiplying PEEP with C_rs), P_tp,plat transpulmonary plateau pressure (calculated as difference between P_aw.plat and plateau esophageal pressure), P_tp,exp end-expiratory transpulmonary pressure (calculated as difference between PEEP and end-expiratory esophageal pressure), SD_RVD standard deviation of regional ventilation delay, EELV end-expiratory lung volume, FRC_recr. recruitment-adjusted functional residual capacity, calculated as EELV–C_rs * PEEP, FRC_release release-derived functional residual capacity, calculated as EELV–released volume during an exhalation to ambient pressure, PBW predicted body weight, Strain_release release-derived strain, calculated as volume change above FRC_rel, normalized to FRC_rel, Strain_recr. recruitment-adjusted strain, calculated as volume change above FRC_recr., normalized to FRC_recr, V_T tidal volume
^*Cardiac output measurements were available in 14 patients