Mechanical ventilation (MV) is a life-saving supportive therapy and one of the most common interventions implemented in intensive care. To date, only the inspiratory phase of breathing has been extensively investigated, and new MV methods have been implemented to reduce its harmful effects. Despite this, lung injury still occurs and propagates, causing multiorgan failure and patient deaths. The expiratory phase is considered unharmful and is not monitored or assisted during MV. In animal experiments, we recently showed that the loss of diaphragmatic contraction during expiration can harm the lungs during MV. During mechanical ventilation, the expiratory phase of breathing is completely disregarded. However, in all conditions that promote lung collapse, peripheral airways gradually compress and close throughout the expiration, potentially worsening lung injury. This cyclical lung collapse and consequent air-trapping may have an impact on the Starling resistor mechanisms that regulate venous return from the brain, potentially affecting cerebral perfusion and intracranial pressure. This study will investigate the incidence and the consequences of an uncontrolled expiration and expiratory lung collapse in spontaneously breathing critically ill neurosurgical patients during 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, on a daily bases during assisted mechanical ventilation.
Study Type
OBSERVATIONAL
Enrollment
30
Observational study where respiratory variables and intracranial pressure will be measured during assisted mechanical ventilation. No intervention is planned.
Incidence of uncontrolled expiration
The incidence of uncontrolled expiration and consequent expiratory lung collapse (determined by changes in expiratory flow and time constant) during assisted ventilation in neurosurgical patients.
Time frame: during the period of assisted mechanical ventilation, an average of 14 days
Correlation between uncontrolled expiration and intracranial pressure
The influence of an uncontrolled expiration (defined by expiratory flow, expiratory EAdi and thoracic impedance) on intracranial pressure in neurosurgical patients.
Time frame: During the period of assisted 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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