Regional ventilation distribution in healthy lungs: can reference values be established for electrical impedance tomography parameters?

Abstract

Background: Although electrical impedance tomography (EIT) is widely used for monitoring regional ventilation distribution, reference values have yet to be established for clinical use. The present study aimed to evaluate the feasibility of creating reference values for standard EIT parameters for potential clinical application.Methods: A total of 75 participants with healthy lungs were included in this prospective study (male:female, 48:27; age, 34±14 years; height, 172±7 cm; weight, 73±12 kg). The subjects were examined during spontaneous breathing in the supine position. EIT measurements were performed at the level of the 4 th intercostal space. Commonly used EIT-based parameters, including the center of ventilation (CoV), dorsal and most dorsal fractions of ventilation distribution (TV D and TV ROI4 respectively), global inhomogeneity (GI) index, and standard deviation of regional ventilation delay index (RVD SD ) were calculated.Results: Following outlier detection, EIT data from 71 subjects were finally evaluated. The values of the evaluated parameters were: CoV, 48.7%±1.7%; TVD, 48.1%±5.4%; TV ROI4 , 7.1%±1.8%; GI, 0.49±0.04; and RVD SD , 7.0±2.0. The coefficients of variation for CoV and GI were low (0.03 and 0.07, respectively), but those for TV ROI4 and RVD SD were comparatively high (0.26 and 0.28, respectively). None of the evaluated parameters showed a significant correlation with age. The GI index showed a weak but significant correlation with body mass index (R=0.29, P=0.01). The RVD SD was slightly higher in males than in females.Conclusions: Our study indicated that CoV and GI were stable parameters with small coefficients of variation in participants with healthy lungs. The creation of EIT parameter reference values for setting treatment targets may be feasible.

First Attempt at Using Electrical Impedance Tomography to Predict High Flow Nasal Cannula Therapy Outcomes at an Early Phase

“…We suspect that, during spontaneous breathing, the inspiration time is too short to have a stable RVD value. A recent study has shown that the coefficient of variation for RVD in healthy subjects was high (30), which might be the reason why no significant difference could be found in the present study.…”

The global inhomogeneity index assessed by electrical impedance tomography overestimates PEEP requirement in patients with ARDS: an observational study

“…Changes in GI at higher PEEP levels are very small. Yang et al found that GI varies ~ 4% in healthy, spontaneously breathing volunteers [ 31 ]. Taken this into account, PEEP is still higher but considerable lower in ARDS patients in our population (12.6 cmH 2 O versus 17.1 cmH 2 O).…”

Electrical Impedance Tomography in Acute Respiratory Distress Syndrome Management

“…Smaller indexes mean more homogeneous ventilation (45). GI was validated retrospectively in ARDS patients (46, 47), prospectively in healthy lungs (48), and recently used as a “tiebreaker” for determining the optimal PEEP when the ODCL is equal among different PEEPs (35).…”

“…Smaller indexes mean more homogeneous ventilation (45). GI was validated retrospectively in ARDS patients (46,47), prospectively in healthy lungs (48), and recently used as a "tiebreaker" for determining the optimal PEEP when the ODCL is equal among different PEEPs (35). 2) Center of Ventilation (CoV): CoV is a geometric reference within the EIT matrix that represents the distribution of ventilation in the vertical and horizontal axes (49).…”