A Beginners Guide to Intubation.
The critical care patient may need intubation for any number of reasons:
– acute airway obstruction
–protection of the airway in those without protective reflexes for example those patients with a neurological problem
–respiratory failure requiring support with high inspired concentrations of oxygen and PEEP.
The process of intubation usually follows the sequence of rapid sequence intubation or RSI. The main issue here is that potentially the patient may have eaten as they are unlikely to have been starved prior to intubation. The main principle behind RSI is prevention of aspiration by the patient during the procedure.
It is important to have all the equipment in place before starting the process. However here I will describe the process in full discussing the equipment needed as it arises. It is probably very important to say at this point that the use of checklists is vital and will prevent many untoward events which may occur.
Time is often of the essence during such an intubation. Once the patient is sedated and paralysed, the practitioner only has a short window in which to insert the endotracheal tube to reinstate the patient’s airway before the oxygen saturations will begin to fall. This is why the start of the procedure begins with the practitioner placing a tight fitting oxygen mask on the patients face to cover the mouth and nose with the flow turned up to at least 15 L per minute. The aim is for the patient to be pre-oxygenated for at least three minutes prior to the drugs being given. This ensures that the patient’s functional residual capacity is washed out of nitrogen and the main constituent is oxygen. This means that the patient’s oxygen saturations will not drop quite so quickly giving the practitioner more time to insert the endotracheal tube.
So the practitioner will require a tight fitting mask attached to a bag valve system which in turn is attached to the wall oxygen.
Once the practitioner is satisfied that the patient is well pre-oxygenated and that his team is ready, each one of them knowing what their role will be, the procedure can begin. Clearly the patient needs to be well monitored during this process and as a minimum should have ECG, oxygen saturations, BP, and capnography. Capnography, and the reasons for its use are discussed below, but it is very important to ensure that this is attached.
Suction may be needed when the patient’s airway is viewed. Preferably this should be wall suction but if this is not available then a portable suction unit will suffice. There should be a Yankeaur sucker attached to this which should be close to hand for the practitioner to use should they need it.
As the drugs are going to be given intravenously and need to be given reasonably quickly it is also important that the patient has good and reliable intravenous access before beginning. There should be two points of access as this will ensure, should one point fail, that there will still be another. The intensive care patient often already has a central line in place, but if they have not then intravenous access should be obtained first.
The patient will then be given firstly a sedative and then secondly a neuro muscular blocking agent. The aim of the sedative is to induce unconsciousness which will ensure cooperation and the patient will not remember this unpleasant experience. The second drug is required to relax the patient’s vocal chords. The vocal cords need to be relaxed in order to ensure that the endotracheal tube can be passed between them. Without the neuro muscular blocking agent the cords potentially will still be together which will not allow passage of the endotracheal tube.
The most common drugs used for this type of procedure are as below:
The advantage of suxamethonium is that it is relatively fast acting and has a very short half life. So the patient will be paralysed within a minute to a minute and a half after its delivery. This also means that if the intubation is not possible for what ever reason, the practitioner can wait for it to wear off and for the patient to begin breathing for themselves again before deciding how to proceed.
Cricoid pressure may need to be applied externally. This is where someone in the team will press down on the cricoid cartilage in the patients trachea. In order to do so effectively they must be aware of the correct landmarks within the patient’s neck. The aim of this pressure is to push the trachea against the oesophagus which will occlude it thereby reducing the chance of aspiration should have the patient vomit during the procedure. It is important that the person doing this knows how to do it properly as when it is done incorrectly it can often make the procedure more difficult for the practitioner trying to insert the endotracheal tube.
Once the practitioner is happy that the patient is both sedated and paralysed they will start the process of inserting the endotracheal tube. This will involve them opening the patient’s airway with a head tilt chin lift manoeuvre and looking into the patients mouth initially. They will then insert the blade of the laryngoscope using their left hand into the patients oral cavity. The curve of the blade ensures that it follows the natural pathway of the bottom of the mouth and tongue. The blade is designed to move the tongue over to the left allowing the practitioner an unobstructed view down to the patient’s epiglottis and larynx. It is at this point that the practitioner may well require the suction in order to clear any secretions that they find.
Once they are happy that they can see the patient’s vocal chords they will ask for the endotracheal tube. Before the process began someone should check the endotracheal tube to ensure that the balloon which maintains the seal once it is in place is intact. The size required should also have been clarified with the practitioner before beginning. In the adult the size commonly used will be something between seven and nine depending on whether the patient is male or female and their size. It is important that the endotracheal tube is placed into the practitioner’s right-hand as they will still be looking down the oral cavity to ensure that they can continue to visualise the vocal cords. Once the tube is handed to them they will then pass it just beyond the vocal cords and ask for the balloon to be inflated.
The bag valve that was used to pre-oxygenated the patient is then attached to the end of the endotracheal tube and the practitioner will attempt to ventilate the patient’s lungs. It is vital at this point that it is ascertained that the endotracheal tube has indeed gone down the trachea and not down the oesophagus, as ventilating into the patient’s stomach will cause them to vomit and possibly aspirate.
Confirmation of Intubation
The main indicator of whether the patient has been successfully intubated is via the use of capnography. This will confirm that carbon dioxide is being returned when ventilating the patient, and the only circumstance under which this is can occur in these conditions is if the endotracheal tube is in the correct position.
The practitioner will also then go on to listen to the bases of the patient’s lungs with a stethoscope. Due to the anatomy of the trachea if the endotracheal tube is pushed into far it will go down the right main bronchus which means that only the right lung is being ventilated. So the practitioner will aim to hear equal air entry. If they do not then the tube may need to be withdrawn slightly to ensure that both lungs are being inflated.
Once the practitioner is satisfies that the endotracheal tube is in the correct position then it should be secured by which ever method used in that department. After that a chest x-ray should be ordered so that the lungs can be properly assessed and the position of the tube can be checked.
Perhaps one of the most important aspects of this procedure is the teamwork required to make the process a smooth one. This is a procedure which is potentially fraught with lots of hazards. However if the pre-intubation checklist is completed, everyone in the team knows their roles and how to perform them correctly, and that the team leader is the only one giving instructions or talking during the procedure then those problems are minimised.