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. 2024 Apr;38(2):539-551.
doi: 10.1007/s10877-023-01107-0. Epub 2024 Jan 19.

A non-invasive continuous and real-time volumetric monitoring in spontaneous breathing subjects based on bioimpedance-ExSpiron®Xi: a validation study in healthy volunteers

Stefano Gatti #  1 , Emanuele Rezoagli #  1   2 , Fabiana Madotto  3 , Giuseppe Foti  1   2 , Giacomo Bellani  4   5
Affiliations

A non-invasive continuous and real-time volumetric monitoring in spontaneous breathing subjects based on bioimpedance-ExSpiron®Xi: a validation study in healthy volunteers

Stefano Gatti et al. J Clin Monit Comput. 2024 Apr.

Abstract

Tidal volume (TV) monitoring breath-by-breath is not available at bedside in non-intubated patients. However, TV monitoring may be useful to evaluate the work of breathing. A non-invasive device based on bioimpedance provides continuous and real-time volumetric tidal estimation during spontaneous breathing. We performed a prospective study in healthy volunteers aimed at evaluating the accuracy, the precision and the trending ability of measurements of ExSpiron®Xi as compared with the gold standard (i.e. spirometry). Further, we explored whether the differences between the 2 devices would be improved by the calibration of ExSpiron®Xi with a pre-determined tidal volume. Analysis accounted for the repeated nature of measurements within each subject. We enrolled 13 healthy volunteers, including 5 men and 8 women. Tidal volume, TV/ideal body weight (IBW) and respiratory rate (RR) measured with spirometer (TVSpirometer) and with ExSpiron®Xi (TVExSpiron) showed a robust correlation, while minute ventilation (MV) showed a weak correlation, in both non/calibrated and calibrated steps. The analysis of the agreement showed that non-calibrated TVExSpiron underestimated TVspirometer, while in the calibrated steps, TVExSpiron overestimated TVspirometer. The calibration procedure did not reduce the average absolute difference (error) between TVSpirometer and TVExSpiron. This happened similarly for TV/IBW and MV, while RR showed high accuracy and precision. The trending ability was excellent for TV, TV/IBW and RR. The concordance rate (CR) was >95% in both calibrated and non-calibrated measurements. The trending ability of minute ventilation was limited. Absolute error for both calibrated and not calibrated values of TV, TV/IBW and MV accounting for repeated measurements was variably associated with BMI, height and smoking status. Conclusions: Non-invasive TV, TV/IBW and RR estimation by ExSpiron®Xi was strongly correlated with tidal ventilation according to the gold standard spirometer technique. This data was not confirmed for MV. The calibration of the device did not improve its performance. Although the accuracy of ExSpiron®Xi was mild and the precision was limited for TV, TV/IBW and MV, the trending ability of the device was strong specifically for TV, TV/IBW and RR. This makes ExSpiron®Xi a non-invasive monitoring system that may detect real-time tidal volume ventilation changes and then suggest the need to better optimize the patient ventilatory support.

Keywords: Bioimpedance; Healthy volunteers; Non-invasive monitoring; Non-invasive respiratory support; Non-invasive ventilation; Respiratory failure; Tidal volume.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Scatter plot of A TVExSpiron and B TVspirometer in non-calibrated and calibrated steps. TV tidal volume, rm repeated measures correlation coefficient
Fig. 2
Fig. 2
Scatter plot of A TV/IBWExSpiron and B TV/IBWspirometer in non-calibrated and calibrated steps. TV tidal volume, IBW ideal body weight, rm repeated measures correlation coefficient
Fig. 3
Fig. 3
Scatter plot of A RRExSpiron and B RRspirometer in non-calibrated and calibrated steps. RR respiratory rate, rm repeated measures correlation coefficient
Fig. 4
Fig. 4
Scatter plot of A MVExSpiron and B MVspirometer in non-calibrated and calibrated steps. MV minute ventilation, rm repeated measures correlation coefficient
Fig. 5
Fig. 5
Bland-Altam plots for each parameter estimated by ExSpiron and measured by spirometry. Tidal volume (TV) in non-calibrated (A) and calibrated (B) steps. Respiratory rate (RR) in non-calibrated (C) and calibrated (D) steps. Minute ventilation (MV) in non-calibrated (E) and calibrated (F) steps. TV/ideal body weight (TV/IBW) in non-calibrated (G) and calibrated (H) steps. In each plot percentage error (PE) is reported. LoA limits of agreement
Fig. 6
Fig. 6
2-way ANOVA differences for each parameter measured by spirometry and by ExSpiron®Xi over increasing tidal volume. On the left are reported graphs for non-calibrated steps, on the right for calibrated. *, p-value<0.05 versus spirometer at a specific target TV. TV tidal volume, RR respiratory rate, MV minute ventilation, IBW ideal body weight
Fig. 7
Fig. 7
4-quadrant plots reporting trending ability for each parameter estimated by ExSpiron and measured by spirometry. Change in tidal volume (ΔTV) in non-calibrated (A) and calibrated (B) steps. Change in respiratory rate (ΔRR) in non-calibrated (C) and calibrated (D) steps. Change in minute ventilation (ΔMV) in non-calibrated (E) and calibrated (F) steps. Change in TV/ideal body weight (ΔTV/IBW) in non-calibrated (G) and calibrated (H) steps. In each plot concordance rate (CR) and concordance correlation coefficient (CCC) are reported
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