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. 2022 Jan 1;50(1):e61-e70.
doi: 10.1097/CCM.0000000000005183.

Noninvasive Tidal Volume Measurements, Using a Time-of-Flight Camera, Under High-Flow Nasal Cannula-A Physiological Evaluation, in Healthy Volunteers

Guillaume Le Moigne  1 , Souha Nazir  2 , Victoire Pateau  3 , Emmanuelle Courtois  4 , Erwan L'Her  2   3
Affiliations

Noninvasive Tidal Volume Measurements, Using a Time-of-Flight Camera, Under High-Flow Nasal Cannula-A Physiological Evaluation, in Healthy Volunteers

Guillaume Le Moigne et al. Crit Care Med. .

Abstract

Objectives: The mechanisms of high-flow nasal cannula are still debated but may be mediated by the generation of low positive end-expiratory pressure and a washout of the airway dead space. The aims of this study were to assess the effects of high-flow nasal cannula on tidal volume using a noninvasive method using a time-of-flight camera, under various conditions.

Design: A physiologic evaluation in healthy volunteers.

Setting: An university hospital ICU.

Subjects: Ten healthy volunteers were included in a physiologic study (CamOpt study, ClinicalTrials.gov identifier: NCT04096183).

Interventions: All volunteers were submitted to 12 different conditions (i.e., gas flow [baseline = 0; 30-60 L/min]; mouth [open/closed]; respiratory rate [baseline; baseline + 10 breaths/min]). Tidal volume measurements were performed every minute, during a 6-minute recording period. In all combinations, reference respiratory rate was measured by using chronometric evaluation, over a 30-second period (RRREF), and by using the time-of-flight camera (RRTOF).

Measurements and main results: Tidal volume increased while increasing gas flow whatever the respiratory rate and mouth condition (p < 0.001). Similar results were observed whatever the experimental conditions (p < 0.01), except one (baseline respiratory rate + 10 breaths/min and mouth closed). Tidal volume increased while decreasing respiratory rate (p < 0.001) and mouth closing (p < 0.05). Proportion of tidal volume greater than 10, 15, and 20 mL/kg changed while increasing the flow. RRTOF was in agreement with RRREF (intraclass correlation coefficient, 0.96), with a low mean bias (0.55 breaths/min) and acceptable deviation.

Conclusions: Time-of-flight enables to detect tidal volume changes under various conditions of high-flow nasal cannula application. Tidal volume increased significantly while increasing gas flow and mouth closing. Such technique might be useful to monitor the risk of patient self-inflicted lung injury or under assistance.

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Conflict of interest statement

Dr. L’Her is the cofounder and shareholder of Oxynov, a biomedical R&D Canadian Company; he received support for article research from Brest University Hospital. He is also consultant for GE Healthcare, Smiths, Sedana Medical, and Vygon. Drs. Nazir and L’Her disclosed they have a patent pending for the time-of-flight monitoring system. Dr. Nazir disclosed work for hire. Ms. Pateau is part of employee for Oxynov. The remaining authors have disclosed that they do not have any potential conflicts of interest.

Comment in

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