A flow-leak correction algorithm for pneumotachographic work-of-breathing measurement during high-flow nasal cannula oxygen therapy. (April 2018)

• Record Type: Journal Article
• Authors: Montecchia, Francesco; Midulla, Fabio; Papoff, Paola
• Is Part Of: Medical engineering & physics. Volume 54(2018)
• Page Start: 32
• Page End: 43
• Publication Date: 2018-04
• Subjects: Algorithm -- Facemask -- Flow leaks -- High-flow nasal cannula -- Pneumotachography -- Pressure time product -- Respiratory flow -- Tidal volume -- Work of breathing; ANOVA analysis of variance -- CPAP continuous positive airway pressure -- CV coefficient of variation -- DP differential pneumotachography -- e_iWOBtot effective iWOBtot;e_iPTPtot, effective iPTPtot;e_Te, effective Te;e_Ti, effective Ti;e_Vte, effective Vte;e_Vti, effective Vti -- fc flow-corrected -- F-LCA flow-LCA -- HFNC high-flow nasal cannula -- iPTPtot inspiratory total PTP -- iWOBtot inspiratory total WOB -- LCA leak correction algorithm -- mfl mean flow line -- Patm atmospheric pressure -- pc pressure-corrected -- PEEP positive end expiratory pressure -- Peso esophageal pressure -- P-LCA pressure-LCA -- PMask pressure inside the facemask -- PNT pneumotachograph -- PTP pressure time product -- iPTPtot inspiratory total pressure time product -- RE relative error -- RMask_Leak mask leak channel resistance -- RMask_PNT−B mask PNT-B resistance -- RR respiratory rate -- SD standard deviation -- Te expiratory time -- Ti inspiratory time -- V˙HFNC_PNT−A HFNC flow via PNT-A -- V˙Mask_Leak flow leakage from the facemask rim -- V˙Mask_Leak_PNT−C facemask flow leakage via PNT-C -- V˙Mask_PNT−B facemask flow via PNT-B -- V˙Resp respiratory flow -- Vt tidal volume -- Vte expiratory tidal volume -- Vti inspiratory tidal volume -- zfl zero flow line -- WOB work of breathing; Biomedical engineering -- Periodicals; Biomedical Engineering -- Periodicals; Physics -- Periodicals; Génie biomédical -- Périodiques; Biomedical engineering; Electronic journals; Periodicals; 610.28
• DOI: 10.1016/j.medengphy.2018.02.004
• Languages: English
• ISSNs: 1350-4533

Abstract

Highlights: Work of breathing (WOB) is hard to measure during high-flow nasal cannula (HFNC). A monitoring facemask and pneumotachograph simplifies the task apart from leakages. A leak-correction algorithm allows WOB measurement via pneumotachography during HFNC. Tested on a mechanical lung model and in vivo our system reliably computed WOB. Abstract: Measuring work of breathing (WOB) is an intricate task during high-flow nasal cannula (HFNC) therapy because the continuous unidirectional flow toward the patient makes pneumotachography technically difficult to use. We implemented a new method for measuring WOB based on a differential pneumotachography (DP) system, equipped with one pneumotachograph inserted in the HFNC circuit and another connected to a monitoring facemask, combined with a leak correction algorithm (LCA) that corrects flow measurement errors arising from leakage around the monitoring facemask. To test this system, we used a mechanical lung model that provided data to compare LCA-corrected respiratory flow, volume and time values with effective values obtained with a third pneumotachograph used instead of the LCA to measure mask flow leaks directly. Effective and corrected volume and time data showed high agreement (Bland–Altman plots) even at the highest leak. Studies on two healthy adult volunteers confirmed that corrected respiratory flow combined with esophageal pressure measurements can accurately determine WOB (relative error < 1%). We conclude that during HFNC therapy, a DP system combined with a facemask and an algorithm that corrects errors due to flow leakages allows pneumotachography to measure reliably the respiratory flow and volume data needed for calculating WOB.