Difficult Breathing Clinical Trial
Official title:
Ultrasound is Superior to Conventional Palpation Method in Identification of the Cricothyroid Membrane in Subjects With Poorly Defined Neck Landmarks: A Randomized Clinical Trial
Routine surgery requires artificial breathing through the placement of a plastic tube into
the patient's windpipe via mouth or nose. This tube serves as the source of providing oxygen
to the patients during surgery. Difficulties during insertion of this tube may lead to
serious complications and during this life-threatening crisis the only way to provide oxygen
to the patient is by the help of a procedure called cricothyrotomy (CTY).
CTY is a life saving procedure that involves an incision on the patient neck at a very
precise location called Cricothyroid Membrane (CTM). The current method of identifying this
location is by palpation of neck cartilages by the operator. The incorrect identification of
the CTM could lead to many complications. In certain patients such as obese or distorted neck
features the identification of CTM would be difficult. Ultrasound (US) has improved the
success rate of many anesthesia procedures .Its use has been described for identification of
neck structures; however, this technique of localization has not been validated against the
gold standard which is the use of CT scan. The purpose of our study is to determine the
precision of identifying the CTM using the US versus the conventional finger palpation when
compared to the gold standard.
Inability to secure the airway remains the most frequent cause of anesthesia-related
mishaps.Difficult airway management continues to be the major challenge in anesthesia as it
is responsible for a third of anesthesia-related claims and is the single largest class of
closed claim injury suits. Difficulties in tracheal intubation is the most frequent cause of
anesthesia-related morbidity and mortality.
Repeated attempts of tracheal intubations can result in serious soft tissue injury and
rapidly deteriorate into a life threatening "cannot intubate-cannot ventilate" (CICV) crisis.
The guidelines suggested by the American Society of Anesthesiologists and the Difficult
Airway Society for managing the unanticipated difficult airway recommend the performance of a
cricothyrotomy(CTY) as the next step for a CICV scenario.
Cricothyrotomy is an infrequently performed life saving procedure when facing a difficult
CICV airway.Previous studies quote, the incidence of the CICV scenario to be in the range of
0.01-2 per 10,000 cases. It is therefore imperative that anesthesiologists have the necessary
knowledge and skills in successfully managing this life-threatening airway crisis. However,
several studies demonstrated that many practicing anesthesiologists and anesthesia trainees
(residents/fellows) are uncomfortable with the management of a CICV situation because it is
such a rare event. A recent Canadian survey shows that only a quarter of the residents and
40% of practicing anesthesiologists were comfortable with performing a cricothyrotomy.
Similar findings were reported in a German national survey of academic teaching hospitals
where difficult airway situations, particularly a CICV crisis, were poorly managed and were
postulated to have contributed to adverse patient outcomes.Complications of emergency CTY by
physicians are common, with rates ranging from 9% to 40%.These complications include failure
to cannulate the trachea, false airway passage, severe bleeding, posterior tracheal wall
injuries, pneumothorax and esophageal laceration. All of these major complications may be
related to improper identification of anatomical landmarks used to identify the correct
position of cricothyroid membrane (CTM). The current method of CTY relies solely on digital
palpation of these landmarks to accurately identify the CTM.
Several studies have identified independent predictors for patients with difficult airway.
These include characteristics such as high body mass index, presence of beard, short bull
neck, distorted neck anatomy either due to congenital or acquired pathology such as goiters
or radiation to the neck. These are the same factors which may lead to improper
identification of neck landmarks for the CTY.
The outcome and accuracy of CTY may be improved with better preparedness and pre-procedural
identification of the neck landmarks for CTY before deciding the method of anesthetic. This
is especially true in patients with anatomical features of difficult airway, who may be the
ones more likely to have a difficult airway or require an emergency CT. In this patient
population, incorrect localization of the CTM may lead to significant airway morbidity or
failure to quickly establish an airway.
The role of ultrasound in airway management:
Bedside ultrasound is increasingly being used to assist anesthesiologists in performing
various procedures.The use of ultrasonography (US) has been shown to significantly reduce
complications and improve outcomes. Diagnostic application of US for upper airway anatomy and
its role for the performance of CTY and bedside tracheostomy has been previously described.
However, little is known on the reliability and validity of the US when compared to the gold
standard CT scan in identifying the CTM.
The methods used to identify CTM are based on identification of anatomical landmarks and
digital palpation. This may be difficult in patients with poorly defined anatomy, the very
same population in which the likelihood of a difficult intubation/emergency surgical airway
are higher.
The trachea and paratracheal soft tissues of the neck can be examined at the highest
resolution with US probes of high frequency due to their superficial position. The anterior
tracheal wall, thyroid and cricoid cartilages, tracheal rings, and pre-tracheal tissue may
all be well visualized , which allows the clinician to select the optimal space for CTY tube
placement. The use of US for assisting with airway management in anesthesia and in the
intensive care unit is directly related to the availability of low-cost and portable US
capabilities. Clinicians initially described US-guided central venous catheterization,
followed by US-guided regional anesthesia techniques. Recently, a few studies examined the
role of US for emergency airway procedures. Nichollas et al developed a standardized US
technique to identify the CTM. The findings in this study suggest that the CTM and relevant
structures can be quickly identified by emergency physicians using US technique. However this
study was limited to patients with normal airway and mainly focused to the standardization of
technique. it did not validate the technique against a gold standard. In another study
Muhammad et al, reported four cases in which ultrasound was successfully used to perform
percutaneous tracheostomy in the ICU. Cricothyroid membrane can easily be located on CT scan.
In summary, inability to secure the airway remains the most frequent cause of
anesthesia-related morbidity and mortality. CTY is highly dependent on proper identification
of anatomical land-marks.
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