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Open Access 01-12-2019 | Acute Respiratory Distress-Syndrome | Research

Heterogeneity of regional inflection points from pressure-volume curves assessed by electrical impedance tomography

Authors: Gaetano Scaramuzzo, Savino Spadaro, Andreas D. Waldmann, Stephan H. Böhm, Riccardo Ragazzi, Elisabetta Marangoni, Valentina Alvisi, Elena Spinelli, Tommaso Mauri, Carlo Alberto Volta

Published in: Critical Care | Issue 1/2019

Abstract

Background

The pressure-volume (P-V) curve has been suggested as a bedside tool to set mechanical ventilation; however, it reflects a global behavior of the lung without giving information on the regional mechanical properties. Regional P-V (PVr) curves derived from electrical impedance tomography (EIT) could provide valuable clinical information at bedside, being able to explore the regional mechanics of the lung. In the present study, we hypothesized that regional P-V curves would provide different information from those obtained from global P-V curves, both in terms of upper and lower inflection points. Therefore, we constructed pressure-volume curves for each pixel row from non-dependent to dependent lung regions of patients affected by acute hypoxemic respiratory failure (AHRF) and acute respiratory distress syndrome (ARDS).

Methods

We analyzed slow-inflation P-V maneuvers data from 12 mechanically ventilated patients. During the inflation, the pneumotachograph was used to record flow and airway pressure while the EIT signals were recorded digitally. From each maneuver, global respiratory system P-V curve (PVg) and PVr curves were obtained, each one corresponding to a pixel row within the EIT image. PVg and PVr curves were fitted using a sigmoidal equation, and the upper (UIP) and lower (LIP) inflection points for each curve were mathematically identified; LIP and UIP from PVg were respectively called LIPg and UIPg. From each measurement, the highest regional LIP (LIPr_MAX) and the lowest regional UIP (UIPr_MIN) were identified and the pressure difference between those two points was defined as linear driving pressure (ΔP_LIN).

Results

A significant difference (p < 0.001) was found between LIPr_MAX (15.8 [9.2–21.1] cmH₂O) and LIPg (2.9 [2.2–8.9] cmH₂O); in all measurements, the LIPr_MAX was higher than the corresponding LIPg. We found a significant difference (p < 0.005) between UIPr_MIN (30.1 [23.5–37.6] cmH₂O) and UIPg (40.5 [34.2–45] cmH₂O), the UIPr_MIN always being lower than the corresponding UIPg. Median ΔP_LIN was 12.6 [7.4–20.8] cmH₂O and in 56% of cases was < 14 cmH₂O.

Conclusions

Regional inflection points derived by EIT show high variability reflecting lung heterogeneity. Regional P-V curves obtained by EIT could convey more sensitive information than global lung mechanics on the pressures within which all lung regions express linear compliance.

Trial registration

Clinicaltrials.gov, NCT02907840. Registered on 20 September 2016.

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Title: Heterogeneity of regional inflection points from pressure-volume curves assessed by electrical impedance tomography
Authors: Gaetano Scaramuzzo
Savino Spadaro
Andreas D. Waldmann
Stephan H. Böhm
Riccardo Ragazzi
Elisabetta Marangoni
Valentina Alvisi
Elena Spinelli
Tommaso Mauri
Carlo Alberto Volta
Publication date: 01-12-2019
Publisher: BioMed Central
Keyword: Acute Respiratory Distress-Syndrome
Published in: Critical Care / Issue 1/2019
Electronic ISSN: 1364-8535
DOI: https://doi.org/10.1186/s13054-019-2417-6

At a glance: The ONWARDS insulin icodec trials

Springer Medicine

Heterogeneity of regional inflection points from pressure-volume curves assessed by electrical impedance tomography

Abstract

Background

Methods

Results

Conclusions

Trial registration

At a glance: The ONWARDS insulin icodec trials

Springer Medicine

Abstract

Background

Methods

Results

Conclusions

Trial registration

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