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. 2023 Aug 30;24(1):215.
doi: 10.1186/s12931-023-02517-z.

Quantifying ventilation by X-ray velocimetry in healthy adults

Trishul Siddharthan  1 , Kyle Grealis  2 , Jason P Kirkness  3 , Tamás Ötvös  3 , Darko Stefanovski  4 , Alex Tombleson  2 , Molly Dalzell  2 , Ernesto Gonzalez  2 , Kinjal Bhatt Nakrani  2 , David Wenger  3 , Michael G Lester  5 , Bradley W Richmond  5   6   7 , Andreas Fouras  3 , Naresh M Punjabi  2
Affiliations

Quantifying ventilation by X-ray velocimetry in healthy adults

Trishul Siddharthan et al. Respir Res. .

Abstract

Rationale: X-ray velocimetry (XV) has been utilized in preclinical models to assess lung motion and regional ventilation, though no studies have compared XV-derived physiologic parameters to measures derived through conventional means.

Objectives: To assess agreement between XV-analysis of fluoroscopic lung images and pitot tube flowmeter measures of ventilation.

Methods: XV- and pitot tube-derived ventilatory parameters were compared during tidal breathing and with bilevel-assisted breathing. Levels of agreement were assessed using the Bland-Altman analysis. Mixed models were used to characterize the association between XV- and pitot tube-derived values and optimize XV-derived values for higher ventilatory volumes.

Measurements and main results: Twenty-four healthy volunteers were assessed during tidal breathing and 11 were reassessed with increased minute ventilation with bilevel-assisted breathing. No clinically significant differences were observed between the two methods for respiratory rate (average Δ: 0.58; 95% limits of agreement: -1.55, 2.71) or duty cycle (average Δ: 0.02; 95% limits of agreement: 0.01, 0.03). Tidal volumes and flow rates measured using XV were lower than those measured using the pitot tube flowmeter, particularly at the higher volume ranges with bilevel-assisted breathing. Under these conditions, a mixed-model based adjustment was applied to the XV-derived values of tidal volume and flow rate to obtain closer agreement with the pitot tube-derived values.

Conclusion: Radiographically obtained measures of ventilation with XV demonstrate a high degree of correlation with parameters of ventilation. If the accuracy of XV were also confirmed for assessing the regional distribution of ventilation, it would provide information that goes beyond the scope of conventional pulmonary function tests or static radiographic assessments.

Keywords: Functional lung imaging; Ventilation heterogeneity; X-ray velocimetry.

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Conflict of interest statement

TS, BR and NP received unrestricted research grants from 4D Medical. DW reports employment for 4D Medical. MK reports grants from the American Thoracic Society and Analog Devices Incorporated, and consulting fees from Ryme Medical. JK, TO reports employment and stock for 4D Medical. AF reports, employment, stock and is on the board of 4D Medical. All other authors report no conflicts of interest. AF additionally reports a patent (PCT/AU2010/001199).

Figures

Fig. 1
Fig. 1
Schematic of the experimental setup illustrating the breathing circuit used for monitoring spontaneous tidal breathing and bilevel assisted breathing along with position of the fluoroscopy C-arm source and detector
Fig. 2
Fig. 2
Scatterplot of XV- and pitot tube-derived respiratory rate (left panel) and a Bland-Altman plot with average difference and the corresponding 95% limits of agreement (right panel). Circles and triangles represent values derived from spontaneous (tidal) and bilevel assisted breathing, respectively
Fig. 3
Fig. 3
Scatterplot of XV- and pitot tube-derived duty cycle (left panel) and a Bland-Altman plot with average difference and the corresponding 95% limits of agreement (right panel). Circles and triangles represent values derived from spontaneous (tidal) and bilevel assisted breathing, respectively
Fig. 4
Fig. 4
Scatterplot of observed XV- and pitot tube-derived peak flow (left panel) and mixed model adjusted XV-peak flow compared to observed pitot tube-derived peak flow (right panel). Circles and triangles represent values derived from spontaneous (tidal) and bilevel assisted breathing, respectively
Fig. 5
Fig. 5
Scatterplot of observed XV- and pitot tube-derived average flow (left panel) and mixed model adjusted XV-average flow compared to observed pitot tube-derived peak flow (right panel). Circles and triangles represent values derived from spontaneous (tidal) and bilevel assisted breathing, respectively
Fig. 6
Fig. 6
Bland-Altman plot of pitot tube-derived and adjusted XV peak flow (left panel) and average flow (right panel) with mean difference and the corresponding 95% limits of agreement. Circles and triangles represent values derived from spontaneous (tidal) and bilevel assisted breathing, respectively
Fig. 7
Fig. 7
Scatterplot of observed XV- and pitot tube-derived tidal volumes (left panel) along with scatterplot of mixed model adjusted XV-tidal volumes compared to observed pitot tube-derived tidal volumes (right panel). Circles and triangles represent values derived from spontaneous (tidal) and bilevel assisted breathing, respectively
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