The goal of this interventional study is to evaluate the effect of different positive end-expiratory pressures (PEEP) on lung and diaphragm function in patients mechanically ventilated with pressure support ventilation in the intensive care unit. The main questions aim to answer: Does higher PEEP level affect diaphragm contractions and ventilatory efficiency? Does higher PEEP level limit inspiratory efforts? Does higher PEEP level affect lung compliance? The participants will be subjected to three different PEEP levels during pressure support ventilation: Low PEEP (4 cmH2O), Medium PEEP (10 cmH2O), High PEEP (16 cmH2O). The lung and diaphragm function will be evaluated using high-resolution esophageal manometry, electrical activity of the diaphragm, external diaphragm ultrasound and spirometric ventilator data.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
SUPPORTIVE_CARE
Masking
SINGLE
Enrollment
25
Low (4 cmH2O) positive end-expiratory pressure (PEEP) will be applied during pressure support ventilation. The PEEP level will be kept for 10 minutes prior to data acquisition.
Medium (10 cmH2O) positive end-expiratory pressure (PEEP) will be applied during pressure support ventilation. The PEEP level will be kept for 10 minutes prior to data acquisition.
High(16 cmH2O) positive end-expiratory pressure (PEEP) will be applied during pressure support ventilation. The PEEP level will be kept for 10 minutes prior to data acquisition.
Central intensivvårdsavdelning, Sahlgrenska University Hospital
Gothenburg, Västra Götaland County, Sweden
Thorax intensivvårdsavdelning, Område 6, Sahlgrenska University Hospital, Västra Götalandsregionen
Gothenburg, Västra Götaland County, Sweden
Inspiratory effort
Inspiratory effort will be measured by the tidal change in esophageal pressure (in cmH2O) during assisted breathing. The esophageal pressure will be measured using a high-resolution manometry catheter. The change from expiratory to inspiratory esophageal pressure will represent the tidal change and be used to estimate the inspiratory effort.
Time frame: Measured during 5 uninterrupted breaths 10 minutes after application of interventional PEEP level
Inspiratory drive
The electric activity of the diaphragm (Eadi) will be measured using a NAVA (neurally adjusted ventilatory assist) catheter. The change from end-expiratory to inspiratory Eadi will be calculated. This represents the inspiratory drive. The Eadi will be measured in Voltage.
Time frame: Measured during 5 uninterrupted breaths 10 minutes after application of interventional PEEP level
Effort-to-drive ratio
The effort-to-drive ratio (EDR) will be calculated as the inspiratory effort (tidal change in esophageal pressure) divided by the inspiratory drive (tidal change in electric activity of the diaphragm).
Time frame: Calculated from the measures collected 10 minutes after application of interventional PEEP level
Neuromechanical efficiency
The neuromechanical efficiency will be calculated as the change in airway pressure during an occlusion test (Pocc) (measured from end-expiration to maximum negative pressure during the occlusion manoeuvre) divided by the inspiratory change in electric activity of the diaphragm (from end-expiration to inspiration).
Time frame: Calculated from the measures collected during the occlusion manoeuvre performed 10-15 minutes after application of interventional PEEP level
Thickening fraction of the diaphragm (TFdi)
Measured by ultrasound at the right hemidiaphragm. The thickening fraction of the diaphragm (TFdi) will be calculated as \[ (end-inspiratory diaphragm thickness - end-expiratory diaphragm thickness) / end-expiratory diaphragm thickness) \].
Time frame: Measured 10 minutes after application of interventional PEEP level
Transpulmonary driving pressure
Change in transpulmonary pressure ( airway pressure - esophageal pressure) from end-expiration to end-inspiration will be calculated using ventilator data and high-resolution manometry
Time frame: Measured during 5 breaths 10 minutes after application of interventional PEEP level
Occlusion pressure
The airway pressure drop from end-expiration to minimum pressure during an occlusion manoeuvre will be measured using the ventilator. The pressure drop indicates the inspiratory effort. It will be measured in cmH2O.
Time frame: The occlusion pressure will be measured during an occlusion manoeuvre performed 10-15 minutes after application of interventional PEEP level.
Airway driving pressure
Difference in airway pressure between end-expiration and during an inspiratory hold will be calculated from the ventilator data.
Time frame: Measured during an inspiratory hold performed 10-15 minutes after application of interventional PEEP level
Lung compliance
Lung compliance will be calculated as the tidal volume divided by the change in transpulmonary pressure from end-expiration to end-inspiration.
Time frame: Measured during an inspiratory hold performed 10 - 15 minutes after application of interventional PEEP level
Thickening fraction of the expiratory abdominal muscles (TFabd)
The abdominal muscles will be visualized by ultrasound in the anterior axillary line, midway between the inferior border of the ribcage and the iliac crest. The thickening fraction will be calculated as \[(expiratory thickness - end-inspiratory thickness) / end-inspiratory thickness \].
Time frame: Measured 10 minutes after application of interventional PEEP level
Oxygenation
The PFI (PaO2/FiO2 ratio) will be calculated as arterial PaO2 (partial pressure of oxygen) divided by the FiO2 (fraction of inspired oxygen)
Time frame: The blood gas will be collected 10 minutes after application of interventional PEEP level
Respiratory system compliance
The respiratory system compliance will be calculated as the tidal volume divided by the airway driving pressure during an inspiratory hold.
Time frame: Measured during an inspiratory hold manoeuvre performed 10-15 minutes after the application of interventional PEEP level.
This platform is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional.