Ventilator Weaning and Extubation in Neurocritical care

Background  

Patients admitted to neuro intensive care units (NICUs) following a traumatic brain injury cannot breathe by themselves. Their breathing is therefore supported by a breathing machine. Tubing connects the patient's lungs to the breathing machine. However, if clinicians leave the patient on the breathing machine for longer than needed, they can develop complications including pneumonia, muscle weakness and lung injury. This can delay recovery and increase the length of stay in ICUs. On the other hand, if the breathing machine is taken away too quickly, the heart and the lungs can be put under stress and this can lead to complications, even death. Usually to prevent this, the breathing tube is reintroduced. This, in turn, can cause infections and injury. Clinicians, therefore, need to be very skilled at knowing the best time to start reducing support from the breathing machine (known as ‘weaning’) and when to remove the tube altogether (known as extubation). Mostly, clinicians use their experience, judgement, and existing knowledge to make their decisions on reducing breathing support and removing the breathing tube. However, some research studies show that clinicians are either too cautious or too aggressive in weaning. This could explain why there are still many patients that do not come off the breathing machine on the first try (known as weaning failure) in the UK. About one third of patients needing breathing machines end up in having the breathing tube put back in within 48 hours or remain on the breathing machine when it is no longer needed. Unfortunately, one in 5 patients cannot cope and the rates of failure range between 20-40% in patients.   

This led to my DPhil project “How can we safely get patients off the ventilators after a traumatic brain injury?”.  

Aims and objectives  

To establish respiratory and non-respiratory predictors of weaning outcomes. 
 
Research Question 

What are the changes in heart and lung function in patients dependent on invasive mechanical ventilation following a traumatic brain injury? 

What is the link between brain injury and neural control of upper airway muscles? 

Plan of Investigation  

Work package 1 
Objective: To establish heart and lung function in patients following a traumatic brain injury and dependent on invasive mechanical ventilation 

Method: We use Inspired sinewave technique using a novel equipment called Inspiwave to measure variables such as lung volume, ventilatory dead space, ventilatory distribution and pulmonary blood flow.  An oscillatory signal is created by making the oxygen concentration oscillate slowly. This signal is passed through the gas mixture the participant breathes. We then analyse the composition of the gas which is exhaled by the participant. Useful heart and lung function parameters could be determined through comparing the size of the inspired and expired gas signals. 

Work package 2 
Objective: To establish link between brain injury and upper airway muscles 

Method: This would be done by studying the neuroanatomy and physiology of control of upper airway muscles and the pathophysiology of the same following a traumatic brain injury. In parallel, we are currently developing a prototype for recording the electrical activity of these muscles through electromyography. 

Inclusion Criteria  

• Age >16 years. 
• Patients who have received IMV more than 24 hours from the time of intubation. 
• Patients who are ready to undergo a weaning trial with set criteria practised at the individual units. 
• Informed consent from patient or relative 
Exclusion Criteria 
• Pregnancy 
• Presence of tracheostomy 
• Lack of consent 
Sample size :Currently our Neurosciences ICU have an average of 600 admissions with 4000 ventilator days. We are hoping to recruit at least 60 patients in each work package.  
Setting 
The study will be conducted at the Neurosciences Intensive care unit (NICU) at the John Radcliffe Hospital, Oxford. 

Ethics  

As the study involves adults lacking capacity to consent, the study will be submitted to the Clinical Trials and Research Governance (CTRG) at the University of Oxford for sponsorship. The research project involves recruitment of critically ill NHS patients at the NICU at the Oxford University Hospitals NHS Foundation Trust (OUH). Hence the study will be submitted to the NHS National Research Ethics Service (NRES) and the Health Research Authority (HRA) for approval. A submission will be made to the Integrated Research Application System (IRAS) and its guidelines will be followed. Ethics has been granted for the Inspiwave study. 

Dissemination 
The proposed study addresses five high priorities and a topmost priority set by the James Lind Alliance priority setting partnerships for ICU patients. Identification of improved prediction of weaning success in this study may facilitate early rehabilitation in conjunction with weaning plans and enhance patient comfort.