The Validity of Maximal Diaphragm Thickening Fraction to Measure Diaphragm Function in Mechanically Ventilated Patients (SNIFF III)

This study is designed to determine whether maximal diaphragm thickening fraction measured by ultrasound during volitional maximal inspiratory efforts is a valid measure of diaphragm function in mechanically ventilated patients.

Study Overview

• Status: Completed
• Conditions: Mechanical Ventilation Complication; Weaning Failure; Diaphragm Injury

Detailed Description

Classically, assessing diaphragm function requires direct measurements of transdaphragmatic pressure generation. A critical requirement for valid measurements is a maximal volitional patient effort. An alternative is to standardize the stimulus to the diaphragm using magnetic twitch stimulation fo the phrenic nerve. This is the gold standard technique for diaphragm function measurement in the respiratory physiology laboratory.

Twitch measurements require technical expertise and expensive equipment; this technique is therefore basically limited to the laboratory. Bedside ultrasonography has been proposed as a method for measuring diaphragm function by assessing the thickening of the muscle during a maximal inspiratory effort. In order to achieve a maximal volitional effort in mechanically ventilated patients, several methods may be employed: coached maximal efforts, coached sniffing, and transient airway occlusion to stimulate respiratory drive (Marini maneuver).

The investigators are evaluating the validity of diaphragm functional assessment using bedside ultrasound in combination with coached efforts/sniffing/Marini maneuver against the gold standard technique: twitch transdiaphragmatic pressure.

• Study Type: Observational
• Enrollment (Actual): 29

Contacts and Locations

Study Locations

• Canada
  • Ontario
    • Toronto, Ontario, Canada, M5G 2N2
      • University Health Network

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No

• Sampling Method: Probability Sample

Study Population

Critically ill patients with acute respiratory failure requiring invasive mechanical ventilation who meet readiness-to-wean criteria.

Description

Inclusion Criteria:

• Adult patients (≥ 18 years old) with acute respiratory failure receiving invasive mechanical ventilation via endotracheal tube or tracheostomy
• Patients who meet readiness-to-wean criteria (triggering the ventilator; FiO2 ≤ 50%; PEEP ≤ 8 cm H20; hemodynamic stability)

Exclusion Criteria:

• Contraindication to phrenic nerve stimulation (chest tube; cardiac pacemaker or implanted defibrillator; cervical implants; use of neuromuscular blocking agents within the 24 hours preceding the first diaphragm assessment (with the exception of succinylcholine used during rapid-sequence induction of anaesthesia for intubation); cervical spine injury; known pregnancy)
• Patients experiencing an acute exacerbation of an obstructive lung disease (chronic obstructive pulmonary disease (COPD), asthma, bronchiectasis)

Study Plan

How is the study designed?

Design Details

• Observational Models: Cohort
• Time Perspectives: Prospective

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort
Patients weaning from mechanical ventilation

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Maximal diaphragm thickening fraction	Diaphragm ultrasound to measure thickening fraction	On day of study

Collaborators and Investigators

• Sponsor: University Health Network, Toronto
• Investigators: Principal Investigator: Ewan C Goligher, MD, PhD, University Health Network, Toronto

Study record dates

Study Major Dates

• Study Start (Actual): November 1, 2015
• Primary Completion (Actual): April 1, 2020
• Study Completion (Actual): April 1, 2020

Study Registration Dates

• First Submitted: April 5, 2017
• First Submitted That Met QC Criteria: April 21, 2017
• First Posted (Actual): April 26, 2017

Study Record Updates

• Last Update Posted (Actual): June 23, 2026
• Last Update Submitted That Met QC Criteria: June 18, 2026
• Last Verified: August 1, 2020

More Information

Terms related to this study

• Keywords: Weaning; Acute respiratory failure; Diaphragm function
• Other Study ID Numbers: 15-9644

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Currently, there is no plan to make data available to other researchers.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No