Calculation of Transpulmonary Pressure From Regional Ventilation Displayed by Electrical Impedance Tomography in Acute Respiratory Distress Syndrome

Transpulmonary driving pressure (DPL) corresponds to the cyclical stress imposed on the lung parenchyma during tidal breathing and, therefore, can be used to assess the risk of ventilator-induced lung injury (VILI). Its measurement at the bedside requires the use of esophageal pressure (Peso), which is sometimes technically challenging. Recently, it has been demonstrated how in an animal model of ARDS, the transpulmonary pressure (PL) measured with Peso calculated with the absolute values method (PL = Paw—Peso) is equivalent to the transpulmonary pressure directly measured using pleural sensors in the central-dependent part of the lung. We hypothesized that, since the PL derived from Peso reflects the regional behavior of the lung, it could exist a relationship between regional parameters measured by electrical impedance tomography (EIT) and driving PL (DPL). Moreover, we explored if, by integrating airways pressure data and EIT data, it could be possible to estimate non-invasively DPL and consequently lung elastance (EL) and elastance-derived inspiratory PL (PI). We analyzed 59 measurements from 20 patients with ARDS. There was a significant intra-patient correlation between EIT derived regional compliance in regions of interest (ROI1) (r = 0.5, p = 0.001), ROI2 (r = −0.68, p < 0.001), and ROI3 (r = −0.4, p = 0.002), and DPL. A multiple linear regression successfully predicted DPL based on respiratory system elastance (Ers), ideal body weight (IBW), roi1%, roi2%, and roi3% (R2 = 0.84, p < 0.001). The corresponding Bland-Altmann analysis showed a bias of −1.4e-007 cmH2O and limits of agreement (LoA) of −2.4–2.4 cmH2O. EL and PI calculated using EIT showed good agreement (R2 = 0.89, p < 0.001 and R2 = 0.75, p < 0.001) with the esophageal derived correspondent variables. In conclusion, DPL has a good correlation with EIT-derived parameters in the central lung. DPL, PI, and EL can be estimated with good accuracy non-invasively combining information coming from EIT and airway pressure.

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Electrical impedance tomography can monitor dynamic hyperinflation in dogs

Journal of Applied Physiology ◽

10.1152/jappl.1998.84.2.726 ◽

1998 ◽

Vol 84 (2) ◽

pp. 726-732 ◽

Cited By ~ 28

Author(s):

Andy Adler ◽

Norihiro Shinozuka ◽

Yves Berthiaume ◽

Robert Guardo ◽

Jason H. T. Bates

Keyword(s):

Electrical Impedance Tomography ◽

Lung Volume ◽

Measurement Errors ◽

Electrical Impedance ◽

Esophageal Pressure ◽

Dynamic Hyperinflation ◽

Average Volume ◽

Impedance Tomography ◽

Lung Inflation ◽

Volume Increase

Adler, Andy, Norihiro Shinozuka, Yves Berthiaume, Robert Guardo, and Jason H. T. Bates. Electrical impedance tomography can monitor dynamic hyperinflation in dogs. J. Appl. Physiol. 84(2): 726–732, 1998.—We assessed in eight dogs the accuracy with which electrical impedance tomography (EIT) can monitor changes in lung volume by comparing the changes in mean lung conductivity obtained with EIT to changes in esophageal pressure (Pes) and to airway opening pressure (Pao) measured after airway occlusion. The average volume measurement errors were determined: 26 ml for EIT; 35 ml for Pao; and 54 ml for Pes. Subsequently, lung inflation due to applied positive end-expiratory pressure was measured by EIT (ΔVEIT) and Pao (ΔVPao) under both inflation and deflation conditions. Whereas ΔVPaowas equal under both conditions, ΔVEITwas 28 ml greater during deflation than inflation, indicating that EIT is sensitive to lung volume history. The average inflation ΔVEITwas 67.7 ± 78 ml greater than ΔVPao, for an average volume increase of 418 ml. Lung inflation due to external expiratory resistance was measured during ventilation by EIT (ΔVEIT,vent) and Pes (ΔVPes,vent) and at occlusion by EIT (ΔVEIT,occl), Pes, and Pao. The average differences between EIT estimates and ΔVEIT,occlwere 5.8 ± 44 ml for ΔVEIT,ventand 49.5 ± 34 ml for ΔVEIT,occl. The average volume increase for all dogs was 442.2 ml. These results show that EIT can provide usefully accurate estimates of changes in lung volume over an extended time period and that the technique has promise as a means of conveniently and noninvasively monitoring lung hyperinflation.

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Continuous Negative Abdominal Pressure Reduces Ventilator-induced Lung Injury in a Porcine Model

Anesthesiology ◽

10.1097/aln.0000000000002236 ◽

2018 ◽

Vol 129 (1) ◽

pp. 163-172 ◽

Cited By ~ 9

Author(s):

Takeshi Yoshida ◽

Doreen Engelberts ◽

Gail Otulakowski ◽

Bhushan Katira ◽

Martin Post ◽

...

Keyword(s):

Lung Injury ◽

Interleukin 6 ◽

Weight Ratio ◽

Transpulmonary Pressure ◽

Dry Weight ◽

Esophageal Pressure ◽

Abdominal Pressure ◽

Impedance Tomography ◽

Ventilator Induced Lung Injury ◽

Novel Approach

Abstract Background In supine patients with acute respiratory distress syndrome, the lung typically partitions into regions of dorsal atelectasis and ventral aeration (“baby lung”). Positive airway pressure is often used to recruit atelectasis, but often overinflates ventral (already aerated) regions. A novel approach to selective recruitment of dorsal atelectasis is by “continuous negative abdominal pressure.” Methods A randomized laboratory study was performed in anesthetized pigs. Lung injury was induced by surfactant lavage followed by 1 h of injurious mechanical ventilation. Randomization (five pigs in each group) was to positive end-expiratory pressure (PEEP) alone or PEEP with continuous negative abdominal pressure (−5 cm H2O via a plexiglass chamber enclosing hindlimbs, pelvis, and abdomen), followed by 4 h of injurious ventilation (high tidal volume, 20 ml/kg; low expiratory transpulmonary pressure, −3 cm H2O). The level of PEEP at the start was ≈7 (vs. ≈3) cm H2O in the PEEP (vs. PEEP plus continuous negative abdominal pressure) groups. Esophageal pressure, hemodynamics, and electrical impedance tomography were recorded, and injury determined by lung wet/dry weight ratio and interleukin-6 expression. Results All animals survived, but cardiac output was decreased in the PEEP group. Addition of continuous negative abdominal pressure to PEEP resulted in greater oxygenation (Pao2/fractional inspired oxygen 316 ± 134 vs. 80 ± 24 mmHg at 4 h, P = 0.005), compliance (14.2 ± 3.0 vs. 10.3 ± 2.2 ml/cm H2O, P = 0.049), and homogeneity of ventilation, with less pulmonary edema (≈10% less) and interleukin-6 expression (≈30% less). Conclusions Continuous negative abdominal pressure added to PEEP reduces ventilator-induced lung injury in a pig model compared with PEEP alone, despite targeting identical expiratory transpulmonary pressure.

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