Individualized Positive End-expiratory Pressure and Regional Gas Exchange in Porcine Lung Injury.

Background: In acute respiratory failure elevated intraabdominal pressure aggravates lung collapse, tidal recruitment, and ventilation inhomogeneity. Low positive end-expiratory pressure (PEEP) may promote lung collapse and intrapulmonary shunting, whereas high PEEP may increase dead space by inspiratory overdistension. The authors hypothesized that an electrical impedance tomography-guided PEEP approach minimizing tidal recruitment improves regional ventilation and perfusion matching when compared to a table-based low PEEP/no recruitment and an oxygenation-guided high PEEP/full recruitment strategy in a hybrid model of lung injury and elevated intraabdominal pressure.

Regional lung ventilation and perfusion by electrical impedance tomography compared to single-photon emission computed tomography.

Objective: Electrical impedance tomography (EIT) is a noninvasive imaging modality that allows real-time monitoring of regional lung ventilation ([Formula: see text]) in intensive care patients at bedside. However, for improved guidance of ventilation therapy it would be beneficial to obtain regional ventilation-to-perfusion ratio ([Formula: see text]) by EIT.

Approach: In order to further explore the feasibility, we first evaluate a model-based approach, based on semi-negative matrix factorization and a gamma-variate model, to extract regional lung perfusion ([Formula: see text]) from EIT measurements.

Gamma-variate modeling of indicator dilution curves in electrical impedance tomography.

Electrical impedance tomography (EIT) is a non-invasive imaging technique, that can be used to monitor regional lung ventilation (V̇) in intensive care units (ICU) at bedside. This work introduces a method to extract regional lung perfusion (Q̇) from EIT image streams in order to quantify regional gas exchange in the lungs. EIT data from a single porcine animal trial, recorded during injection of a contrast agent (NaCl 10%) into a central venous catheter (CVC), are used for evaluation.

Pumpless extracorporeal CO(2) removal restores normocapnia and is associated with less regional perfusion in experimental acute lung injury.

Background: Lung protective ventilation may lead to hypoventilation with subsequent hypercapnic acidosis (HA). If HA cannot be tolerated or occurs despite increasing respiratory rate or buffering, extracorporeal CO2-removal using a percutaneous extracorporeal lung assist (pECLA) is an option. We hypothesised that compensation of HA using pECLA impairs regional perfusion.

The effect of pumpless extracorporeal CO2 removal on regional perfusion of the brain in experimental acute lung injury.

Background: Lung-protective mechanical ventilation with low tidal volumes (V(T)) is often associated with hypercapnia (HC), which may be unacceptable in patients with brain injury. CO2 removal using a percutaneous extracorporeal lung assist (pECLA) enables normocapnia despite low V(T), but its effects on regional cerebral blood flow (rCBF) remain ambiguous. We hypothesized that reversal of HC by pECLA impairs rCBF in a porcine lung injury model.

Tidal recruitment assessed by electrical impedance tomography and computed tomography in a porcine model of lung injury*.

Objectives: To determine the validity of electrical impedance tomography to detect and quantify the amount of tidal recruitment caused by different positive end-expiratory pressure levels in a porcine acute lung injury model.

Design: Randomized, controlled, prospective experimental study.

Setting: Academic research laboratory.

Effect of PEEP on regional ventilation during laparoscopic surgery monitored by electrical impedance tomography.

Background: Anesthesia per se and pneumoperitoneum during laparoscopic surgery lead to atelectasis and impairment of oxygenation. We hypothesized that a ventilation with positive end-expiratory pressure (PEEP) during general anesthesia and laparoscopic surgery leads to a more homogeneous ventilation distribution as determined by electrical impedance tomography (EIT). Furthermore, we supposed that PEEP ventilation in lung-healthy patients would improve the parameters of oxygenation and respiratory compliance.

Impedance tomography as a new monitoring technique.

Purpose Of Review: Electrical impedance tomography (EIT) noninvasively creates images of the local ventilation and arguably lung perfusion distribution at bedside. Methodological and clinical aspects of EIT when used as a monitoring tool in the intensive care unit are reviewed and discussed.

Recent Findings: Whereas former investigations addressed the issue of validating EIT to measure regional ventilation, current studies focus on clinical applications such as detection of pneumothorax.

Experimental case report: development of a pneumothorax monitored by electrical impedance tomography.

Electrical impedance tomography (EIT) is a non-invasive, radiation-free functional imaging technique, which allows continuous bedside measurement of regional lung ventilation. Pneumothorax is an uncommon but nevertheless potentially dangerous incident that may arise unexpectedly. We report an incident of an accidental tension pneumothorax during an experimental ventilation study in a pig that was continuously monitored by EIT.

Dynamic separation of pulmonary and cardiac changes in electrical impedance tomography.

In spontaneously breathing or ventilated subjects, it is difficult to image cardiac-related conductivity changes using electrical impedance tomography (EIT) due to the high amplitude of the ventilation component. Previous attempts to separate these components included either electrocardiogram-gated averaging, frequency domain filtering or holding the breath while performing the measurements. However, such methods are either not able to produce continuous real-time images or to fully separate cardiac and pulmonary changes.

Robust closed-loop control of the inspired fraction of oxygen for the online assessment of recruitment maneuvers.

Recruitment maneuvers are commonly used in patients suffering from acute respiratory failure. A continuous measurement of PaO(2) would help to assess the proper execution of such maneuvers. Unfortunately, there are only static offline measurement devices available.

Protective ventilation using electrical impedance tomography.

Dynamic thoracic EIT is capable of detecting changes of the ventilation distribution in the lung. Nevertheless, it has yet to become an established clinical tool. Therefore, it is necessary to consider application scenarios wherein fast and distinct changes of the tissue conductivities are to be found and also have a clear diagnostic significance.

Assessment of regional lung recruitment and derecruitment during a PEEP trial based on electrical impedance tomography.

Objective: To investigate whether electrical impedance tomography (EIT) is capable of monitoring regional lung recruitment and lung collapse during a positive end-expiratory pressure (PEEP) trial.

Design: Experimental animal study of acute lung injury.

Subject: Six pigs with saline-lavage-induced acute lung injury.