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.
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.
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.
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Treatment groupsSee each treatment group below.