Spirometric detection of esophageal intubation

In endotracheal intubation, it is essential that the trachea is intubated and
not the esophagus. In suboptimal situations (outside an operating theatre),
malpositioning of the endotracheal tube occurs frequently and is often fatal.
The diagnostic tools that are available in the operating theatre are not
appropriate for out-of-hospital situations because of several reasons.
Moreover, these methods mostly take some time to provide the desired
information and don*t have optimal specificity and sensitivity. In order to
allow fast diagnosis of this potentially fatal complication, we are developing
a fully-automatic detection device to diagnose endotracheal tube malpositioning
within 2 seconds.
A high sensitivity/specificity of the algorithm for waveform-analysis was
demonstrated in a first study5.
A new device with integrated sensors and microprocessor was developed as a
first step to a stand-alone device. This device performs the
pressure-registration and the data are sent via Bluetooth to a PC for later
analysis. This device was evaluated in intensive care to demonstrate the high
sensitivity in patients with pulmonary disease and to demonstrate the
feasibility of a battery-powered handheld device for this purpose. These
results clearly prove the feasibility and confirm the high sensitivity6.
Now we developed an advanced next generation device, based on the same
electronics as the first stand-alone device, but where the waveform analysis is
performed in real-time and a diagnosis is provided immediately. In addition, an
extra algorithm is added to the waveform analysis to detect tube location
without the need for test ventilation.
A red or green light is activated depending on oesophageal or tracheal tube
location. Before it can be reliably used in out-of-hospital emergency
situations, a final study in a controlled environment must be performed to
evaluate the new electronic system and integrated software. In addition, a
higher number of patients needs to be included to more reliably determine
sensitivity and specificity.

Determination of the sensitivity and specificity of the algorithm to detect
esophageal intubation. (green/red/no light and numerical value of the
calculated D-value

interventional study

In these patients, automatic pressure waveform is performed during the first
three test ventilations after tracheal intubation. After securing of the
airway, the oesophagus will also be intubated and three conventional thoracic
pushes will be performed. Thereafter, three test ventilations will be performed
on both tubes. The sequence (either first 3 times oesophageal followed by 3
times tracheal or conversely) will be determined by randomisation. The
responses from the automatic detection device will be recorded. Also all
pressure waveforms and computed numbers will automatically be recorded in the
internal memory of the device. Thereafter, normal tracheal ventilation will be
resumed, any residual gastric air will be evacuated and the oesophageal tube
will be removed. Then the procedure can be continued as planned. The whole
period of research interventions will take no more than 3 minutes
Main study parameters/endpoints: determination (and automatic recording) of red
or green light on the detection device after tracheal and oesophageal test
ventilation. Automatic recording of all calculated values by the algorithm and
all pressure waveforms during the procedure of test ventilation and thoracic
pushes.

All measurements will be under anaesthesia. Tracheal ventilation is routine
clinical practice. A soft *thoracic push* is harmless and frequently performed
for clinical assessment of appropriate tube location in patients where
spirometry is available on the anesthesia ventilator. Test ventilations are
also always performed during routine clinical practice. Oesophageal intubation
with an endotracheal tube, performed under laryngoscopy by a trained
anesthesiologist should be considered harmless. It happens *accidentally*
several times a day in any hospital without reported injuries. During the
procedure of oesophageal intubation and ventilation, the free airway will
already be protected by the tracheal tube with inflated cuff that is already in
place. Even during normal clinical practice, manual ventilation using a
ventilation mask often causes insufflated gastric air, which is in many cases
left *untreated*. In patients included in the study, insufflated gastric air
will be removed using a conventional gastric tube.
The total time of the investigational procedure will take maximally 3 minutes
in will cause no burden for the patient.