The TONES trial aims to evaluate the neuroventilatory efficiency (NVE = tidal volume / peak voltage of diaphragm contraction) measured during a zero-assist manoeuvre (ZAM, i.e. with PEEP but without pressure support). This novel parameter, NVE-ZAM, will be studied in a blocked, crossover, repeated measures design. Possible confounders, such as activity of respiratory muscles other than the diaphragm, are included. The investigators hypothesized that * the NVE during a zero-assist maneuver has a low variability and high repeatability at the same level of PEEP (within subjects, within blocks) * NVE-ZAM trends differ between participants (between subjects, within blocks) and between PEEP levels (within subjects, between blocks) The primary aim is to study the variability and repeatability of the NVE-ZAM within subjects and within blocks. Additionally, the effect of PEEP, muscle fatigue and recruitment of the accessory and expiratory muscles of respiration on the NVE-ZAM will be studied in an exploratory analysis (in multiple combinations of within and between subjects and/or blocks).
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
DIAGNOSTIC
Masking
NONE
Enrollment
1
A short period (\< 30 seconds) during which both inspiratory and expiratory valves of the ventilator circuit are closed at the end of inspiration. It is used to asses expiratory force generation (maximal expiratory pressure, MEP) and frequently used in clinical practice.
A short period (\< 30 seconds) during which both inspiratory and expiratory valves of the ventilator circuit are closed at the end of expiration. It is used to asses static PEEP and inspiratory force generation (maximal inspiratory pressure, MIP \& occlusion pressure, ∆Pocc) and is frequently used in clinical practice.
Ultrasound of the diaphragm, parasternal intercostal muscle and internal oblique muscle will be performed during each block. Thickening fractions, calculated as thickness at end-inspiration minus thickness at end-expiration divided by thickness at end-expiration, are used to assess the contribution of the muscle to the tidal volume. A median over 5 breaths will be calculated.
Positive End-Expiratory Pressure of 10cmH2O for 30 minutes
Positive End-Expiratory Pressure of 5cmH2O for 30 minutes
Positive End-Expiratory Pressure of 0cmH2O for 30 minutes
Antwerp University Hospital
Edegem, Antwerp, Belgium
Neuroventilatory efficiency (NVE) during a zero-assist breath in neural pressure support mode with a pressure support level of 7cmH2O and a PEEP of 10 cmH2O
Measured using an Edi catheter (Maquet, Solna, Sweden) each 3 minutes as tidal volume / delta Edi. Zero assist is defined as a pressure support of 0 cmH2O during a single breath.
Time frame: Measured each 3 mintues during blocks A1 and B1: initial 30 minutes of training in both trainings A and B (cumulative: 2x 30 minutes)
Neuroventilatory efficiency (NVE) during a zero-assist breath in neural pressure support mode with a pressure support level of 7cmH2O and a PEEP of 5 cmH2O
Measured using an Edi catheter (Maquet, Solna, Sweden) each 3 minutes as tidal volume / delta Edi. Zero assist is defined as a pressure support of 0 cmH2O during a single breath.
Time frame: Measured each 3 mintues during blocks A2 and B2: second next 30 minutes of training in both trainings A and B (cumulative: 2x 30 minutes)
Neuroventilatory efficiency (NVE) during a zero-assist breath in neural pressure support mode with a pressure support level of 7cmH2O and a PEEP of 5 cmH2O
Measured using an Edi catheter (Maquet, Solna, Sweden) each 3 minutes as tidal volume / delta Edi. Zero assist is defined as a pressure support of 0 cmH2O during a single breath.
Time frame: Measured each 3 mintues during block A3: third next 30 minutes of training in training A (cumulative: 1x 30 minutes)
Neuroventilatory efficiency (NVE) during a zero-assist breath in neural pressure support mode with a pressure support level of 7cmH2O and a PEEP of 0 cmH2O
Measured using an Edi catheter (Maquet, Solna, Sweden) each 3 minutes as tidal volume / delta Edi. Zero assist is defined as a pressure support of 0 cmH2O during a single breath.
Time frame: Measured each 3 mintues during block B3: third next 30 minutes of training in training B (cumulative: 1x 30 minutes)
Neuroventilatory efficiency (NVE) during a zero-assist breath in neural pressure support mode with a pressure support level of 7cmH2O and a PEEP of 5 cmH2O
Measured using an Edi catheter (Maquet, Solna, Sweden) each 3 minutes as tidal volume / delta Edi. Zero assist is defined as a pressure support of 0 cmH2O during a single breath.
Time frame: Measured each 3 mintues during blocks A4 and B4: fourth next 30 minutes of training in both trainings A and B (cumulative: 2x 30 minutes)
Change in RSBI (ml*min)
Rapid shallow breathing index, calculated as tidal volume divided by respiratory rate
Time frame: Measured at each breath during 30 minutes in block B3 (at zero PEEP; cumulative 30 minutes)
Change in P0.1 (cmH2O)
Airway pressure at the first 100 milliseconds of a breath
Time frame: Measured at each breath during 30 minutes for each training block (A1-4 & B1-4; cumulative 4hours)
Change in Cdyn (ml / cmH2O)
Dynamic respiratory system compliance, calculated as tidal volume divided by driving pressure
Time frame: Measured at each breath during 30 minutes for each training block (A1-4 & B1-4; cumulative 4hours)
Change in Raw (cmH2O * L / s)
Respiratory system resistance, calculated as (peak inspiratory pressure - plateau pressure) / flow
Time frame: Measured at each breath during 30 minutes for each training block (A1-4 & B1-4; cumulative 4hours)
Change in PIP (cmH2O)
Peak Inspiratory Pressure
Time frame: Measured at each breath during 30 minutes for each training block (A1-4 & B1-4; cumulative 4hours)
Change in DTF
Diaphragm thickening fraction, calculated as (diaphragm thickness at end-inspiration - diaphragm thickness at end-expiration) / diaphragm thickness at end-expiration \[dimensionless\]. Muscle thickness will be measured in millimeters using M-mode ultrasound with the probe placed perpendicular to the muscle (not including the thickness of fascial muscle layers).
Time frame: Measured for 5 breaths in the 30 minutes for each training block (A1-4 & B1-4; cumulative 4hours)
Change in ICTF
Parasternal intercostal muscle thickening fraction, calculated as (parasternal intercostal muscle thickness at end-inspiration - parasternal intercostal muscle thickness at end-expiration) / parasternal intercostal muscle thickness at end-expiration \[dimensionless\]. Muscle thickness will be measured in millimeters using M-mode ultrasound with the probe placed perpendicular to the muscle (not including the thickness of fascial muscle layers).
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Time frame: Measured for 5 breaths in the 30 minutes for each training block (A1-4 & B1-4; cumulative 4hours)
Change in IOTF
Internal oblique muscle thickening fraction, calculated as (internal oblique muscle thickness at end-inspiration - internal oblique muscle thickness at end-expiration) / internal oblique muscle thickness at end-expiration \[dimensionless\]. Muscle thickness will be measured in millimeters using M-mode ultrasound with the probe placed perpendicular to the muscle (not including the thickness of fascial muscle layers).
Time frame: Measured for 5 breaths in the 30 minutes for each training block (A1-4 & B1-4; cumulative 4hours)
Change in MIP (cmH2O)
Maximal inspiratory pressure
Time frame: Measured during an expiratory hold of ≤ 30 seconds between each training block (AH0-4 & BH0-4; cumulative ≤ 5 minutes)
Change in MEP (cmH2O)
Maximal expiratory pressure
Time frame: Measured during an inspiratory hold of ≤ 30 seconds between each training block (AH0-4 & BH0-4; cumulative ≤ 5 minutes)
Change in ∆Pocc (cmH2O)
Airway occlusion pressure
Time frame: Measured during an expiratory hold of ≤ 30 seconds between each training block (AH0-4 & BH0-4; cumulative ≤ 5 minutes)
Change in NVE (ml/µv)
Neuroventilatory efficiency, calculated as tidal volume divided by delta Edi. It is measured at a pressure support of 7 cmH2O, i.e. NOT during a zero assist manoeuvre.
Time frame: Measured at each breath during 30 minutes for each training block (A1-4 & B1-4; cumulative 4hours)
Change in TV (ml)
Tidal volume
Time frame: Measured at each breath during 30 minutes for each training block (A1-4 & B1-4; cumulative 4hours)
Change in ∆Edi (µV)
Increase in electrical activity of the diaphragm (Edi) during inspiration, calculated as Edi high - Edi low.
Time frame: Measured at each breath during 30 minutes for each training block (A1-4 & B1-4; cumulative 4hours)
Change in Pplat (cmH2O)
Airway plateau pressure
Time frame: Measured at each breath during 30 minutes for each training block (A1-4 & B1-4; cumulative 4hours)
Change in static PEEP (cmH2O)
Postive end-expiratory pressure as measured during an expiratory hold.
Time frame: Measured during an expiratory hold of ≤ 30 seconds between each training block (AH0-4 & BH0-4; cumulative ≤ 5 minutes)