APAGBI Small Research Grant
Endoscopic evaluation of the paediatric airway after prior prolonged (>24hrs)tracheal intubation
Dr Helen Hume-Smith
Background: When a child has an anaesthetic for surgery or requires life-support in intensive care, it is vital for their safety that breathing is controlled. In order to do this a breathing tube (tracheal tube) is placed in the windpipe (intubation). In adults the tube has a balloon (cuff) on the end, which when inflated seals the windpipe (trachea). This allows the lungs to be ventilated effectively, prevents harmful stomach contents that may be regurgitated from entering the lungs, and prevents atmospheric contamination with anaesthetic gases. Despite the advantages of a cuffed tube, in children, tubes without a cuff have traditionally been used because the area beneath the voice box is very delicate and prone to damage if too much pressure is applied by an overinflated cuff. Excess pressure may cause swelling and scarring leading to difficulty in breathing once the tube is removed. New tracheal tubes with a cuff, designed for children, have been produced and are being routinely used by some centres. Currently all research into their safety has focused on the absence of increased breathing difficulty once the tube is removed. In order to more carefully check that these tubes are not causing swelling and exposing children to increased risk it is necessary to look into the trachea, with a telescopic camera, and compare the effects of the two different types of tube (i.e. with or without a cuff) in children intubated for a prolonged period of time.
Aims: The aim of the study is to get high quality video recordings of children's tracheas who have been intubated for more than 24 hours. This will allow us to gain more information about differences in type and degree of airway damage caused by cuffed versus uncuffed tubes as well as other risk factors for airway injury in children.
Methods: This is a prospective, observational multi-centre study. We are the UK centre and the site that uses uncuffed tubes. Children who have previously been intubated for more than 24 hours who are attending for planned surgery that requires intubation will be recruited. A standard anaesthetic will be administered. A telescopic camera will be guided down the trachea and video recorded for approximately 30 seconds prior to intubation occurring. 1000 of these recordings have been performed in healthy children in a separate study without problem. The video will then be uploaded to a remote site where they will be evaluated by an international panel of airway experts unaware of patient history. If clinically significant airway pathology is seen the family would be informed.
Expected Outcomes: The information will provide important data relating to the safety of cuffed tracheal tubes in children. It may also identify other risk factors for airway injury in children such as blood pressure instability or respiratory tract infections.
Implications: This study will help guide paediatric anaesthetists and intensivists in choosing the type of tracheal tube to use in individual cases. We hope this will reduce complications in this vulnerable group of patients.
A case-crossover study investigating alternations of the ECG baseline in ventilated children undergoing thoracoscopic surgery: a reliable indicator of pneumothorax?
Dr Michael Macmahon
Background: When patients are anaesthetised there is the potential for air to leak into the space between the lung and chest wall (the pleura). This is called a pneumothorax and can be very serious as the air compresses the lungs and blood vessels in the chest. The only treatment is to empty the air from within the pleura using a drain, however if this treatment is delayed, serious harm can ensue. At the moment the diagnosis of pneumothorax relies upon listening to the chest and a chest x-ray. This is much more difficult when a patient is anaesthetised and in theatre as the nature of the operation often prevents access to the chest.
Aims: If there was another reliable sign of a pneumothorax then it would make it much easier for anaesthetists looking after children (and adults) to make the diagnosis of a pneumothorax and treat it rapidly. There is some evidence from reported cases that the electrical signal from the heart (the ECG) gets bigger and smaller as the patient breaths in and out. This gives the appearance that the ECG is 'swinging' up and down in time with breathing. However case reports are not enough to demonstrate that this change in the ECG trace is useful in the theatre environment. A scientific study to investigate this change in the ECG when there is a pneumothorax has not yet been done.
Methodology: We are undertaking a study to look at the relationship between pneumothorax and the ECG trace. Pneumothorax occurs so infrequently that it is very difficult to study. However, there is an operation in children where the air is injected between the lung and the chest wall to allow the surgeon to operate on the lung. This provides an opportunity to study this relationship. We will record the heart tracing for a period before and during these operations and look if the heart tracing changes when the air is injected into the pleura. These ECG tracings will then be compared to see if there is a significant increase in swing when the pneumothorax is present.
Expected outcomes: We expect that there will be a significant change in the ECG trace when the pneumothorax is created.
Implications: If the study shows a significant change in the ECG tracing then a useful piece of clinical information can be added to the anaesthetist's decision-making process. It will hopefully allow more rapid identification of pneumothorax and a possible reduction in the associated morbidity and mortality of this condition.
