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Completed

NCT Number: NCT03129386

Defining the Normal Range for Maximal Sniff Diaphragm Thickening Fraction

This study is investigating the normal range of maximal diaphragm thickness during a sniff inspiratory manoeuvre using ultrasound in healthy subjects stratified by age and gender.

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Key information

Conditions

Diaphragm

Age range

18 year and older

Sex eligibility

All sexes

Study type

Observational

Primary location

University Health Network

Toronto, Ontario, M5G 2N2, Canada

About this study

Diaphragm dysfunction is associated with poor clinical outcomes in critically ill patients but is difficult to diagnose. Traditionally, diaphragm function is measured by evaluating inspiratory muscle strength via maximal inspiratory pressure (MIP). However, this technique relies on a volitional maximal effort and can be challenging for patients to perform.

An alternative to measuring inspiratory muscle strength is the sniff inspiratory pressure approach. During short, sharp sniffs, the diaphragm is maximally activated.

Currently, there are no reported values of the normal range of maximal diaphragm thickness during a sniff maneuver. This study will define the normal range of values for sniff maximal diaphragm thickening fraction, maximal thickening against an occluded airway, and diaphragm thickening during resting tidal breathing in healthy subjects.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Over 18 years of age

Exclusion criteria

  • Antecedent history of neuromuscular or cardiorespiratory disease

Treatment and study plan

Primary outcomes

  1. Sniff diaphragm thickening fraction

    Time frame: Day 1

    Thickening of the diaphragm during an inspiratory sniff

  2. Maximal diaphragm thickening fraction

    Time frame: Day 1

    Thickening of the diaphragm during a maximal inspiratory effort

  3. Resting tidal thickening fraction

    Time frame: Day 1

    Thickening of the diaphragm during resting tidal breathing

Sponsors and collaborators

Lead sponsor

University Health Network, Toronto

Other

Registry information

Acronym: SNIFF II

Important dates

Study start
2016
Primary completion
2018
Study completion
2019
First posted
Apr 26, 2017
Registry last updated
Jun 23, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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