The impact of mechanical ventilation on intracranial perfusion is still not completely clarified. It is often assumed that raising airway pressure will invariably elevate the intracranial pressure, but this is not always the case. The effects of airway pressure on intracranial pressure can depend on several factors, and among others, an uncontrolled expiration and consequent lung collapse may have an influence on cerebral perfusion. This study will investigate the incidence and the consequences of an uncontrolled expiration and expiratory lung collapse in critically ill neurosurgical patients during controlled mechanical ventilation. Electrical impedance tomography measurements , oesophagus and gastric pressure, electrical activity of the diaphragm and intracranial pressure will be acquired in a synchronised manner during controlled mechanical ventilation. Moreover, airway opening pressure, expiratory flow limitation and recruitment/inflation ratio will be determined during controlled mechanical ventilation, on a daily bases until the patient recover his/her own spontaneous breathing.
Study Type
OBSERVATIONAL
Enrollment
30
Observational study where respiratory variables and intracranial pressure will be measured during mechanical ventilation and during specific respiratory manoeuvres. No intervention is planned.
The incidence of lung collapse
The incidence of an uncontrolled expiration and consequent expiratory lung collapse (determined by expiratory flow limitation, airway opening pressure and expiratory thoracic impedance) increased chest-wall elastance in neurosurgical patients.
Time frame: during the period of controlled mechanical ventilation, an average of 14 days
Correlation between lung recruitability and intracerebral pressure
The influence of lung recruitability (determined by recruitment/inflation ratio and changes of thoracic impedance) on intra cerebral pressure in neurosurgical patients.
Time frame: during the period of controlled mechanical ventilation, an average of 14 days
Correlation between lung collapse and intracerebral pressure
The correlation between an uncontrolled expiration (determined by expiratory flow limitation, airway opening and expiratory thoracic impedance), increased chest-wall elastance and intracranial pressure in neurosurgical patients.
Time frame: during the period of controlled mechanical ventilation, an average of 14 days
Intensive care unit (ICU) and hospital length of stay (LOS);
Correlation between lung collapse and LOS
Time frame: At ICU/hospital discharge, an average of 30 days
Number of days of mechanical ventilation
Correlation between lung collapse and days of mechanical ventilation
Time frame: At ICU discharge, an average of 20 days
90-days mortality from intensive care unit admission
Correlation between lung collapse and 90-days mortality
Time frame: 90 days after hospital discharge
30-day and 90-days neurological and functional outcomes
Correlation between lung collapse and 30-day and 90-days neurological and functional outcomes (Disability Rating Scale, clinical frailty score, Glasgow Outcome Scale)
Time frame: 90 days after hospital discharge
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