Diaphragm Hibernation and Its Driving Factors in Mechanically Ventilated ICU Patients

Rationale:

Patients with invasive mechanical ventilation (IMV) frequently develop diaphragm dysfunction and experience difficult weaning. Recent ex vivo work suggests that a subset of mechanically ventilated ICU patients may exhibit diaphragm hibernation, an energy conserving myosin state that reduces force generation and may lead to a reversible increase in diaphragm strength over time. However, it is unknown whether diaphragm hibernation can be demonstrated in vivo during IMV and which clinical and biological factors are associated with this phenotype.

Objective:

Primary objective is to determine the driving factors (biomarkers) of diaphragm hibernation during IMV. Secondary objectives are to determine the proportion of ventilated critically ill patients who exhibit diaphragm hibernation during IMV, to investigate inflammatory and metabolic factors and other clinical exposures associated with diaphragm hibernation, and to explore associations between diaphragm hibernation and weaning related and survival outcomes.

Study design:

Prospective, observational, longitudinal cohort study.

Study population:

Adult ICU patients receiving IMV, expected to remain mechanically ventilated for at least 72 hours.

Intervention (if applicable):

Not applicable. This is an observational study. Study specific procedures consist of repeated phrenic nerve magnetic stimulation and additional blood sampling.

Main study parameters/endpoints:

The primary study parameter is the proportion of participants exhibiting diaphragm hibernation during IMV. Diaphragm hibernation is defined as an increase in stimulated twitch tracheal pressure (Ptr,stim), a measure of diaphragm strength, of at least 10% relative to baseline (Day 0-1) at any follow up assessment (Day 2, 3, 5, or 7) obtained before extubation or death. Ptr,stim will be assessed repeatedly on Day 0-1, Day 2, Day 3, Day 5, and Day 7, or until extubation or death, whichever occurs first.

Nature and extent of the burden and risks associated with participation, benefit and group relatedness:

Participant burden is limited and mainly consists of repeated phrenic nerve magnetic stimulation during a ventilator delivered end expiratory occlusion and additional blood sampling of 9.5 mL per time point, up to a total of 47.5 mL across the study period. Magnetic stimulation is non-invasive and expected discomfort is transient. Rare transient physiological changes may occur and measurements are performed under continuous ICU monitoring and will be postponed or omitted if considered unsafe or interfering with clinical care. Direct benefit for participants is limited, but the study may provide clinically relevant knowledge on diaphragm hibernation and its driving factors. The research questions are specific to diaphragm physiology during IMV in critically ill patients, therefore the study is group related and cannot be performed in a different population.