|New Method for Endotracheal
October 4, 1994
A new method for endotracheal intubations has been developed by Heart Akerson with the help of Dr. James Riopelle of Charity Hospital in New Orleans and Dr. Wilson León of Hospital San Juan de Diós in San Jose, Costa Rica. The goal of this project has been to develop a device that indicates whether the tube is in the trachea or in the esophagus while the tube is being inserted rather than after the intubation is complete and the respiration equipment is connected and operating. Also, it is hoped that this device could be manufactured for a low enough cost to make it available worldwide wherever intubations are done such as operating rooms, emergency rooms, "crash carts" and ambulances.
Sonomatic Confirmation Of Tracheal Intubation (SCOTI)
SCOTI (U.S. Patent #5,331,967) 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 100 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 the respiration equipment connected. This is the first device which can actually help with the intubation process while it is happening! SCOTI 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 is being 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. The tracheal tube can be hooked directly
to SCOTI or have adaptors and tubes between it and SCOTI. A disposable
bacteria filter can be used to avoid the risk of contamination between
patients. A corrugated tube can be used to minimize the weight in the operators
hand. If this tube is used then 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.
These tests were performed in the operating rooms of Hospital San Juan de Dios in San Jose, Costa Rica. This Hospital has 20 operating rooms for adults and is operated by the Seguro Social of Costa Rica. These tests were approved by the Internal Review Board and encouraged by the Chief Anesthesiologist and the Chief Surgeon. Consent was obtained from the patients after the process and its risks were discussed.
A Hudson bacteria filter was hooked to SCOTI. To this was hooked a 15 mm by 76 cm corrugated flexible tube. To the end of this was hooked a 15mm right angle adaptor. To this was hooked the tracheal tube which was between 6.0 and 10.0 mm as these tests were for adults. SCOTI was taped to the operating table next to the right side of the patients head so that the anesthesiologist could see SCOTI while he was intubating.
When the tracheal tube sterile package was opened the tube was only pulled half way out so that the tip was still in the package. Then the end of the tube and the Murphy's eye were closed by pinching them between the thumb and the forefinger through the sterile package. Then SCOTI was turned on and the holes held closed until the indicator light stopped flashing indicating that configuration was complete. The reading on the LCD readout was recorded with the end of the tube open and with the end of the tube closed (making sure to also cover the Murphy's eye).
Then the tube was intentionally inserted into the patients esophagus and the LCD readout was recorded. Then the tube was inserted into the trachea and the LCD readout recorded. Then SCOTI with its filter, corrugated tube and right angle adaptor were disconnected and the respirator was connected and the operation proceeded. No pulse oxymetry or capnography were available but the tracheal intubation was confirmed and monitored by the normal methods used at this Hospital, i.e. breath sounds, pulse rate, blood pressure, respirator pressure, etc. Since all normal methods of confirming tracheal intubation were used and the results of SCOTI were used for experimental data only, the patients were exposed to no additional risk as a result of this experiment.
The test included 72 patients and the results can be seen in the table and on the graph. With the indicator light level set to show red below 16 and green above 20 SCOTI was red on 100% of the cases in the esophagus and green on 70 of the cases in the trachea. The band between 16 and 20 was considered an error or unreliable band in which the indicator light was yellow as happened on two cases in the trachea.
In addition to the above tests several patients were used to simulate blind intubations. SCOTI was configured in the "Reverse" mode. When the patient was intubated only a small amount of pressure was exerted on the Laryngoscope so that the glottis was not visible. The anesthesiologist used the color of the light from SCOTI to know when the tube was in the trachea. Then enough pressure was exerted on the Laryngoscope to expose the glottis to confirm if the intubation was successful. In 100% of these cases the intubation was successful and did not take any longer than normal.
Although the database is small it is very encouraging. More tests are continuing with the same methods as well as with different configurations of attachments. Also tests are being started with infants and children.
Clinical tests have also been completed by St Barts Hospital in London England and John Radcliff Hospital in Oxford, England with similar results. Their results will be published separately.