Multicenter, Multinational, Follow-Up Clinical Trial of the Performance of RESPINOR DXT to Identify Patients at Increased Risk of Weaning Failure

Weaning will be conducted by the clinician in charge of the patient, in accordance with the rules of good practice from the international consensus conference on withdrawal from MV (Boles, et al., 2007). Patients eligible for the study will perform a first spontaneous breathing trial (SBT) during which they will remain connected to the ventilator for 30-120 minutes on continuous positive airway pressure up to 5 cm H2O and pressure support up to 7 cm H2O, according to the recommendations of the international consensus conference on intensive care medicine (Boles, et al., 2007) and usual practices of the service.

During the SBT, the diaphragm excursion (DE) and respiratory rate shall be measured continuously using the investigative device, RESPINOR DXT, designed by the sponsor, RESPINOR (Oslo, Norway) for all patients.The continuous measurements shall be initiated 15 minutes prior to the SBT and last until 15 minutes post SBT. The investigator will be blinded to the DXT output. The DXT control unit will only display the signal needed to confirm good quality. During blinding mode, all quantifiable data are hidden from the screen; In the case DXT does not initiate blinding mode, the investigators shall enter this in the eCRF and report to the sponsor. In case of blinding failure, the patient will be excluded from the primary and secondary endpoint analysis (data marked as missing). Sensitivity analyses may, however, be conducted by including data pertaining to such unblinded patients. The patient can still be included in the descriptive secondary endpoints (including safety).

Additionally, information on VT and RR from the ventilator should be noted for the 2nd minute of the SBT.

The SBT will be interrupted and considered a failure in case of any of the SBT failure criteria:

• Respiratory rate > 35 breaths/min
• Increased accessory muscle activity
• SpO2 persistently below 90% on FiO2 < 0.4
• Heart rate persistently above 140 beats/min
• Systolic arterial blood pressure < 90 mmHg or > 180 mmHg
• Appearance of cyanosis or mottling
• Depressed mental status or agitation

A trial is considered successful, and physicians will be asked to approve extubation when the patient can breathe spontaneously for the whole trial. The patient may receive oxygen supplementation by nasal cannula or mask as needed.

The pathophysiology of weaning failure is often complex and multifactorial-respiratory, cardiac, and neurological problems can all cause weaning failure, especially in patients who have had prolonged stays in intensive care. It is therefore important to take a structured approach, identifying each factor and addressing it in turn. The physician will therefore log the failure criteria as well as the underlying reason for weaning failure.

Depressed mental status is one of the failure criteria of spontaneous breathing trials. A patient can have resolution of the acute phase of the disease for which the patient was intubated as well as adequate respiratory and cardiac function, but still have a depressed mental status leading to weaning failure. Depressed mental status will, in most cases, not affect the DE, and as such, DXT cannot predict patients who have weaning failure solely due to depressed mental status. Another cause for weaning failure unrelated to the DE is congestive heart failure. Consequently, if a patient has weaning failure solely due to depressed mental status or congestive heart failure, the patient will be excluded from the primary endpoint analysis.

Inclusion criteria

• Adult patients, defined as >=18 years of age, willing and able to give informed consent (either themselves or next of kin)
• Have undergone invasive mechanical ventilation >= 24 hours
• Ready to wean according to criteria (from the sixth international consensus conference on intensive care medicine):

• Adequate cough.
• Absence of excessive tracheobronchial secretion.
• Resolution of disease acute phase for which the patient was intubated.
• Clinical stability, defined as stable cardiovascular status (i.e., fC < 140 beats·min-1, systolic BP 90-160 mmHg, no or minimal vasopressors) and stable metabolic status.
• Adequate oxygenation, defined as SaO2 > 90% on < FIO2 0.4 (or PaO2/FIO2 > 150 mmHg) and PEEP < 8 cmH2O.
• Adequate pulmonary function, i.e., fR < 35 breaths·min-1.
• Adequate mentation, defined as no sedation or adequate mentation on sedation (or stable neurologic patient), i.e., patient awake, calm and responsive to simple orders (squeeze hand, knock the head, close the eyes), no agitation.

Exclusion criteria

• Not registered with a social security system nor entitled to be.
• Central or spinal neurological injury involving central ventilatory control.
• Presence of a neuromuscular disease involving respiratory muscles.
• Use of muscle-paralyzing agents within 24h before the study, except if given for intubation.
• Known paralysis of a hemidiaphragm or suspicion of paralysis of a hemidiaphragm, defined by the radiographic evidence of elevation of a dome > 2.5 cm compared to the contralateral dome.
• Tracheostomy.
• Body mass index >35 kg/m2.
• Patient with therapeutic limitation, i.e., reduced expectancy to survive, defined by a Charlson Comorbidity Index < 5%.
• Pregnant woman or protected adult.