Diaphragmatic Physiology Similarity Index May Titrate HFNC Flow Setting: A Prospective Observational Study

Overview

Study Objective This prospective observational study aims to investigate the role of the Diaphragmatic Physiology Similarity Index (DPSI) derived from speckle tracking ultrasound in titrating high-flow nasal cannula (HFNC) flow settings, and to evaluate its application in patients with acute respiratory failure. Primary Research Questions To characterize the features of the DPSI in healthy individuals and in patients with acute respiratory failure. To assess the behavior of the DPSI under different HFNC flow settings in patients with acute respiratory failure. Secondary Research Questions Feasibility and inter-operator reproducibility of diaphragmatic speckle tracking. Assessment of the Diaphragmatic Contraction Synchrony Index. Evaluation of End-Diaphragmatic Residual Contraction (EDRC). Additional fundamental parameters, including diaphragmatic displacement velocity and maximum displacement.

Interventions

• Other High-flow adjustment sequence
  Delivers heated, humidified blended oxygen via HFNC with real-time titration based on diaphragmatic speckle-tracking metrics (e.g., DPSI, contraction synchrony). Flow is adjusted in predefined increments to reach target diaphragmatic physiology while FiO₂ is titrated to maintain target SpO₂. Ultrasound feedback is used for bedside decisions; safety triggers allow clinical override.

Primary outcome measures

• Diaphragmatic Physiology Similarity Index (DPSI) [Time frame: Healthy Participants: Baseline； Baseline evaluation at the time of enrollment change with each change in ventilation parameters.]

Secondary outcome measures (7)

• Adverse events including pneumothorax, hemodynamic instability, and other complications [Time frame: At baseline (upon enrollment), 1 hour / 6 hours / 24 hours after intervention, and during daily morning assessments until extubation or day 28.]
• Arterial blood gas analysis (ABG analysis) [Time frame: At baseline (upon enrollment), 1 hour / 6 hours / 24 hours after intervention, and during daily morning assessments until extubation or day 28.]
• Diaphragmatic Contraction Synchrony Index [Time frame: After each HFNC flow adjustment: Measure contraction synchrony during each flow setting period.]
• ICC (Intraclass Correlation Coefficient) [Time frame: At each ultrasound assessment, record the percentage of analyzable images. Compare measurements at the beginning and throughout the study among operators.]
• Evaluation of End-Diaphragmatic Residual Contraction (EDRC) [Time frame: After each mechanical ventilation period: Measure EDRC at the end of the mechanical ventilation phase, noting the diaphragm's ability to recover.]
• Diaphragmatic Displacement Velocity and Maximum Displacement [Time frame: At each flow setting change: Measure the diaphragm's displacement velocity and maximum displacement at each HFNC flow rate adjustment.]
• Diaphragmatic ultrasound parameters (maximum displacement, thickening fraction, etc.) [Time frame: At baseline (upon enrollment), 1 hour / 6 hours / 24 hours after the intervention, and daily morning assessments until extubation or day 28.]

Eligibility criteria

Feasibility and reproducibility：adult ICU patients

Methodology for diaphragmatic motion synchrony:healthy adults and adult ICU patients Between-group comparisons and flow-titration study

Inclusion criteria

• Age ≥18 years old.
• Clear diagnosis of respiratory failure requiring respiratory support.
• Expected duration of respiratory support ≥24 hours or (high-flow/non-invasive ventilation) ≥48 hours.
• Voluntary participation in this study and signed informed consent. If the participant is unable to read or sign the informed consent form due to incapacity (e.g., unconsciousness), the legal guardian must act as a proxy in the informed consent process and sign the form. If the participant cannot read the consent form (e.g., illiterate participants), a witness must observe the informed consent process and sign the form.

Exclusion criteria

• Severe chest wall deformities or diaphragmatic paralysis.
• End-stage disease with a predicted life expectancy of less than 24 hours.
• Inability to acquire STE (strains and echoes) images (e.g., severe subcutaneous emphysema, position limitations).
• Vulnerable groups other than critically ill patients/elderly/illiterate individuals, including those with mental disorders, cognitive impairments, pregnant women, etc.

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: Yes

Study design

Allocation

Randomized

Model

Crossover

Masking

Double blind

Primary purpose

Treatment

Study locations

China · 2 centers

• Sir Run Run shaw Hospital Zhejiang University — Hangzhou
• Sir Run Run Shaw Hospital, Zhejiang University School of Medicine — Hangzhou

Publications

• Goutman SA, Hamilton JD, Swihart B, Foerster B, Feldman EL, Rubin JM. Speckle tracking as a method to measure hemidiaphragm excursion. Muscle Nerve. 2017 Jan;55(1):125-127. doi: 10.1002/mus.25380. Epub 2016 Aug 22. PMID 27533320
• Santana PV, Cardenas LZ, Albuquerque ALP. Diaphragm Ultrasound in Critically Ill Patients on Mechanical Ventilation-Evolving Concepts. Diagnostics (Basel). 2023 Mar 15;13(6):1116. doi: 10.3390/diagnostics13061116. PMID 36980423
• Li R, Zhou Y, Chen W, Lyu L, Qiu G, Pan C, Tang Y. Speckle tracking ultrasound as a new tool to predict the weaning outcome of mechanical ventilation patients: a prospective observational study. Front Med (Lausanne). 2024 Dec 6;11:1449938. doi: 10.3389/fmed.2024.1449938. eCollection 2024. PMID 39712177
• Ye X, Liu Z, Ma Y, Song Y, Hu L, Luo J, Xiao H. A Novel Normalized Cross-Correlation Speckle-Tracking Ultrasound Algorithm for the Evaluation of Diaphragm Deformation. Front Med (Lausanne). 2021 Mar 12;8:612933. doi: 10.3389/fmed.2021.612933. eCollection 2021. PMID 33777969
• van den Berg MJW, Heunks L, Doorduin J. Advances in achieving lung and diaphragm-protective ventilation. Curr Opin Crit Care. 2025 Feb 1;31(1):38-46. doi: 10.1097/MCC.0000000000001228. Epub 2024 Nov 14. PMID 39560149
• Watanabe S, Sekiguchi K, Suehiro H, Yoshikawa M, Noda Y, Kamiyama N, Matsumoto R. Decreased diaphragm moving distance measured by ultrasound speckle tracking reflects poor prognosis in amyotrophic lateral sclerosis. Clin Neurophysiol Pract. 2024 Oct 22;9:252-260. doi: 10.1016/j.cnp.2024.10.002. eCollection 2024. PMID 39534515
• Xu Q, Yang X, Qian Y, Hu C, Lu W, Cai S, Hu B, Li J. Comparison of assessment of diaphragm function using speckle tracking between patients with successful and failed weaning: a multicentre, observational, pilot study. BMC Pulm Med. 2022 Dec 1;22(1):459. doi: 10.1186/s12890-022-02260-z. PMID 36456940
• Goligher EC, Jonkman AH, Dianti J, Vaporidi K, Beitler JR, Patel BK, Yoshida T, Jaber S, Dres M, Mauri T, Bellani G, Demoule A, Brochard L, Heunks L. Clinical strategies for implementing lung and diaphragm-protective ventilation: avoiding insufficient and excessive effort. Intensive Care Med. 2020 Dec;46(12):2314-2326. doi: 10.1007/s00134-020-06288-9. Epub 2020 Nov 2. PMID 33140181

Identifiers

NCT: NCT06996665 · 20250271

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗