When a patient has been given anesthesia he becomes paralyzed and will not be capable of breathing. To allow breathing to occur artificially a tube (endotracheal tube) is inserted into the patient's trachea (intubation) and connected to a respiration machine. Sometimes the tube is accidentally inserted into the esophagus and if this goes undetected the patient will receive no oxygen and have permanent brain damage within a few minutes and will die within several minutes. As the patient runs out of oxygen they start to turn blue and their life signs start to falter so the anesthesiologist or doctor usually are aware of the problem but canít always reintubate correctly quick enough to save the patient. An external hole can be cut or punctured through the neck into the trachea but things happen so quickly that this often is not done in time to save the patient. The process of intubation requires considerable training and skill. The tube must be inserted through the glottis, which is often very difficult to see. Generally, a laryngoscope is used to contort the shape of the patientís mouth and provide light to allow direct visualization of the glottis but the geometry of the patient is such that often this is not possible particularly if the person intubating hasnít had years of practice.
When a person is under cardiac arrest they are generally intubated to gain control of the breathing. This is often done by paramedics and other people who have less experience and skill than an anesthesiologist.
To aid in detecting esophageal intubations devices are used that detect the presence of carbon dioxide in the airway (end-tidal CO2 monitors). These are either electronic (capnography) or are disposable and have some chemicals which change color as the CO2 content changes (colormatic). End-tidal CO2 monitors only produce a reliable result after the intubation is completed and several breaths of air have been forced into the patient. If the endotracheal tube is in the esophagus this air being pumped into the stomach will heavily increase the chance of regurgitation especially if it is an emergency situation and the patient has not fasted in preparation of being given anesthesia. If anesthesia has been given the glottis may also be paralyzed heavily increasing the chances of aspiration of gastric contents. Taking vomit into the lungs is very serious and can cause severe complications within several days including death. If the person is being intubated because of cardiac arrest then intidal CO2 monitoring does not work since there is no gas exchange with no heartbeat.
In the past few years emergency physicians have started performing Rapid Sequence Intubations where they very quickly give the patient anesthesia and intubate them to allow them to have control of the patient and treat them more quickly and efficiently. These intubations generally have more problems because the skill level of the person intubating is generally lower than that of an anesthesiologist and the patient has not fasted in preparation and is generally already under considerable trauma. The legal considerations are also heavier since the emergency physician has opted to introduce the risks of anesthesia usually without the patientís consent.
Undetected Esophageal Intubation remains one of the biggest risks to anesthesiology today. Capnography has improved things in the operating rooms in the United States somewhat but will probably never become commonplace in the operating rooms in most countries because of its high cost, about $8,000 to $10,000. It also will probably never be used in ambulances and "crash carts" in hospitals also because of its high cost. These emergency intubations generally are done by less experienced people and the patients are already under more stress and can tolerate intubation problems for less time.
Even in operating rooms equipped with capnography equipment the anesthesiologist must connect the respiration equipment after the intubation and wait for 4 or 5 breaths to interpret the result. If it appears the tube is not in the trachea the respiration equipment must be disconnected and the intubation tried again. If the geometry of the patient is such that the anesthesiologist canít get a good view of the glottis then this "hit and miss" method of intubation could use up a lot of precious time when the patient is receiving no oxygen. Since capnography gives no information while the intubation is actually happening it doesnít really help with a difficult intubation, it just confirms the results. In addition, in a cardiac arrest, there will be no carbon dioxide exhaled and thus the capnography will not indicate that the tube is in the trachea even if the intubation was done correctly. This is the case in a high percentage of the emergency intubations!
When capnography isnít available there are other less reliable methods such as listening for breath sounds but they all also require that the patient is being actively respirated and use up similar amounts of precious time. Because so many intubations go smoothly there is a tendency for them to become routine and make the anesthesiologist overconfident and ignore symptoms and information until it is too late.
More recently disposable carbon dioxide detectors have been on the market to address some of these problems but have had some problems with recently ingested carbonated beverages and also require the patient to be actively respirated for 4 or 5 breaths after the intubation before producing a reliable result. This, like capnography, will not work with a cardiac arrest.
These commonly used methods of detecting esophageal intubation entail quantities of gas being pumped into the stomach which could provoke regurgitation and aspiration of gastric contents.
Another method which uses a syringe or self-inflating bulb to detect the esophagusís tendency to restrict air flow has been developed. To date this (Esophageal Detection Device) has not gained much popularity and requires a somewhat tricky process to be performed by the operator.
To date no one has developed a system that actually tells you what you need when you need it, i.e. instant indication of whether the tube is in the trachea or in the esophagus while the intubation is happening!
SCOTI is a small battery operated device that connects to the end of the tracheal tube during intubation. It produces sounds in the normal audio range and determines whether the tube is in the trachea or the esophagus with special algorithms. The result is displayed with a light which is green when the tube is in the trachea and red when it is in the esophagus. The color of the light is updated 10 times a second so the perceived feedback is instant and continuous allowing for the anesthesiologist to make many rapid "trial and error" intubation attempts in a few seconds, a process which would take several minutes without this device. After the intubation SCOTI is disconnected and put away. This is the first device which can actually help with the intubation process while it is happening! In addition, the device also has an LCD readout which displays a number between 0 and 100 which allows the operator to interpret the output of the algorithm himself. This also allows for large amounts of data to be gathered in the field which could be used to improve the device. SCOTI also contains an audible indicator that gives the operator the information of the lights and LCD. SCOTI automatically configures itself when it is turned on to operate with whatever size tube and attachments that are hooked to it.
SCOTI is currently 145.0mm X 63.5mm X 62.5mm and weighs 300 grams. A disposable bacteria filter is used to avoid the risk of contamination between patients. A custom made disposable airway circuit made with a corrugated tube and filter is used to minimize the weight in the operators hand and prevent cross contamination between patients. Because of this flexible tube SCOTI can sit on the operating table by the patients head, be strapped to the operators arm or belt or be held by an assistant. The common 9 volt battery will last several weeks in an operating room and will indicate when it is getting low with enough charge left to do a typical days work.
SCOTI would not have to replace capnography but could supplement it. It could end up in hospitals for less than $500 a piece.