Regional ventilation distribution determined by electrical impedance tomography: reproducibility and effects of posture and chest plane.

BACKGROUND AND OBJECTIVE: Reliable assessment of regional lung ventilation and good reproducibility of electrical impedance tomography (EIT) data are the prerequisites for the future application of EIT in a clinical setting. The aims of our study were to determine (i) the reproducibility of repeated EIT measurements and (ii) the effect of the studied transverse chest plane on ventilation distribution in different postures. METHODS: Ten healthy adult subjects were studied in three postures on two separate days. EIT and spirometric data were obtained during tidal breathing and slow vital capacity (VC) manoeuvres. EIT data were acquired in two chest planes at 13 scans/s. Reproducibility of EIT findings was assessed by Bland-Altman analysis and Pearson correlation in 16 regions of interest in each plane. Regional ventilation distribution during tidal breathing and deep expiration was determined as fractional ventilation in four quadrants of the studied chest cross-sections. RESULTS: Our study showed a good reproducibility of EIT measurements repeated after an average time interval of 8 days. Global tidal volumes and VCs determined by spirometry on separate days were not significantly different. Regional ventilation in chest quadrants assessed by EIT was also unaffected. Posture exerted a significant effect on ventilation distribution among the chest quadrants during spontaneous breathing and deep expiration in both planes. The spatial distribution patterns in the two planes were not identical. CONCLUSIONS: We conclude that regional EIT ventilation findings are reproducible and recommend that the EIT examination location on the chest is carefully chosen especially during repeated measurements and follow-up.

Deletions in 16p13 including GRIN2A in patients with intellectual disability, various dysmorphic features, and seizure disorders of the rolandic region.

Seizure disorders of the rolandic region comprise a spectrum of different epilepsy syndromes ranging from benign rolandic epilepsy to more severe seizure disorders including atypical benign partial epilepsy/pseudo-Lennox syndrome,electrical status epilepticus during sleep, and Landau-Kleffner syndrome. Centrotemporal spikes are the unifying electroencephalographic hallmark of these benign focal epilepsies, indicating a pathophysiologic relationship between the various epilepsies arising from the rolandic region. The etiology of these epilepsies is elusive, but a genetic component is assumed given the heritability of the characteristic electrographic trait. Herein we report on three patients with intellectual disability, various dysmorphic features, and epilepsies involving the rolandic region, carrying previously undescribed deletions in 16p13. The only gene located in the critical region shared by all three patients is GRIN2A coding for the alpha-2 subunit of the neuronal N-methyl-D-aspartate(NMDA) receptor.

Regional lung opening and closing pressures in patients with acute lung injury.

PURPOSE: In acute lung injury (ALI), the application of positive end-expiratory pressure (PEEP) is known to prevent the alveoli from cyclic collapse and reopening and to homogenize ventilation. The setting of adequate PEEP could be optimized by the knowledge of regional lung opening and closing pressures at the bedside. The aim of our study was to determine regional opening and closing pressures in ventilated patients by electrical impedance tomography (EIT). MATERIALS AND METHODS: Eight patients with healthy lungs and 18 patients with ALI were studied. A low-flow inflation and deflation maneuver with constant gas flow was performed. Regional opening and closing pressures were calculated for every pixel of the EIT scan. These pressures were defined as those values of global airway pressure at which the lung areas opened up or started to close. RESULTS: Injured lungs exhibited significantly higher regional opening pressures compared with healthy lungs (P < .05). In ALI, significantly higher opening pressures were found in the dependent lung regions. Regional closing pressures did not significantly differ between healthy and injured lungs. CONCLUSIONS: Regional lung opening and closing pressures can be assessed by EIT. This information may facilitate the setting of adequate PEEP levels in patients in future.

Patient examinations using electrical impedance tomography--sources of interference in the intensive care unit.

Electrical impedance tomography (EIT) is expected to become a valuable tool for monitoring mechanically ventilated patients due to its ability to continuously assess regional lung ventilation and aeration. Several sources of interference with EIT examinations exist in intensive care units (ICU). Our objectives are to demonstrate how some medical nursing and monitoring devices interfere with EIT measurements and modify the EIT scans and waveforms, which approaches can be applied to minimize these effects and how possible misinterpretation can be avoided. We present four cases of EIT examinations of adult ICU patients. Two of the patients were subjected to pulsation therapy using a pulsating air suspension mattress while being ventilated by high-frequency oscillatory or conventional pressure-controlled ventilation, respectively. The EIT signal modulation synchronous with the occurrence of the pulsating wave was 2.3 times larger than the periodic modulation synchronous with heart rate and high-frequency oscillations. During conventional ventilation, the pulsating mattress induced an EIT signal fluctuation with a magnitude corresponding to about 20% of the patient's tidal volume. In the third patient, interference with EIT examination was caused by continuous cardiac output monitoring. The last patient's examination was disturbed by impedance pneumography when excitation currents of similar frequency to EIT were used. In all subjects, the generation of functional EIT scans was compromised and interpretation of regional ventilation impossible. Discontinuation of pulsation therapy and of continuous cardiac output and impedance respiration monitoring immediately improved the EIT signal and scan quality. Offline processing of the disturbed data using frequency filtering enabled partial retrieval of relevant information. We conclude that thoracic EIT examinations in the ICU require cautious interpretation because of possible mechanical and electromagnetic interference.