Clinical Trial Details
— Status: Recruiting
Administrative data
| NCT number |
NCT02639897 |
| Other study ID # |
EC/10/15/901 |
| Secondary ID |
|
| Status |
Recruiting |
| Phase |
|
| First received |
|
| Last updated |
|
| Start date |
October 2016 |
| Est. completion date |
July 2025 |
Study information
| Verified date |
December 2023 |
| Source |
Sir Ganga Ram Hospital |
| Contact |
Nitin Sethi, DNB |
| Phone |
00919717494498 |
| Email |
nitinsethi77[@]yahoo.co.in |
| Is FDA regulated |
No |
| Health authority |
|
| Study type |
Observational
|
Clinical Trial Summary
Direct laryngoscopy and intubation is an essential initial aspect of airway access during
general anesthesia. To perform the procedure effectively, it requires adequate mouth opening,
head and neck movement, and a normal temporo-mandibular joint mobility. Any issue with the
above three results in a compromised upper airway at the outset and the condition is known as
anticipated difficult airway, i.e. an airway that is difficult to access with conventional
laryngoscopy and intubation methods. To overcome the difficulty, either one has to resort to
newer advanced technique and equipment or the available conventional technique needs to be
refined and modified to suit the requirement. While the former requires extraordinary
expertise and finances, an option difficult to achieve in developing countries; the latter
warrants focused interest to develop alternative approach with the same set of equipments.
Since submucous fibrosis and the associated restricted mouth opening have taken the
proposition of an epidemic owing to widespread use of betel nut and tobacco; these patients,
when requiring surgery, are difficult candidates for GA and airway control. The fact that,
when they arrive as pre-surgical candidates, they have variable degree of mouth opening
restriction, which if approached with a strategy, may be amenable to conventional control of
airway. If investigators paint all the patients with mouth restriction as difficult airway,
it will result in uncalled surgical, economic, health system and psychological burden.
Therefore, it is prudent to undertake research relating to refinement of airway access
techniques with the easily available, cheap and user- friendly equipment (conventional
laryngoscope), such that a proportion of above stated burden can be reduced.
In view of the above, investigators plan to undertake a study to enhance our working
knowledge with a conventional laryngoscope (Macintosh) to facilitate ways to control the
airway difficulty secondary to mouth opening restriction. Investigators believe that the
prospective knowledge thus generated would help us identify whether there is a feasibility of
conventional airway management or an alternative advanced access technique is needed in the
first place. This will prevent undue cancellations, delayed surgeries, and patient morbidity.
Description:
Upper airway access is one of the essential components of general anaesthesia, and more often
than not, it is gained by direct laryngoscopy followed by tracheal intubation. While direct
laryngoscopy depends on laryngoscope blade design and the anesthetists' skill set, the ease
of tracheal intubation is influenced by the line-of-view to the glottis gained by the
laryngoscopy maneuver. In patients with normal mouth opening (≥4.0 cm), the act of
conventional airway access is not difficult given that the neck extension and the TMJ joint
mobility is within normal limits. Conversely, it becomes difficult in patients who have mouth
opening restriction, and hence they are adjudicated as 'anticipated difficult airway' (ADA).
The ADA, attracts several issues that, not uncommonly, converges on to time inefficiency,
heightened equipment cost, operator anxiety, and unfortunately, patient morbidity. There are
many causes of restricted mouth opening, defined technically as reduced inter-incisor
distance (IID) including trauma, TMJ movement limitation, intra/extra-oral pathology
resulting in pain, or the most common pathology in the Indian subcontinent, oral submucosal
fibrosis (SMF). While the pathology itself is a forerunner of oral mitosis, it is the
associated restricted mouth opening component that put conventional airway access efforts of
the anaesthesiologist in spot, and consequently, a whole, sometimes unnecessary rigmarole has
to be activated under the heading of 'advanced approach to ADA'.
Oral submucous fibrosis (SMF) is a well-recognized, potentially malignant progressive
condition afflicting the oral cavity that is characterised by a reduced mouth opening. The
reduction in mouth opening occurs due a vertical reorientation of collagen fibrils that are
normally haphazardly arranged. Of the currently available multiple classifications to
identify disease stage/severity, the functional classification based on the inter-incisor
distance (IID) seems to be most relevant.
IID forms an important component of airway examination and a value of less than 3-cm is
suggestive of difficulty in airway management. However, despite the above, SMF is largely
unrecognized as a cause of airway difficulty, and even when recognized, no set protocol is
available to ensure (as far as possible) a favourable outcome in terms of least morbidity to
the patient, and stress to the anaesthesiology team in question.
Need Assessment for the Study Generally, in a tertiary level centre, with all facilities at
hand, cases with a reduced IID are normally tackled using a fiberoptic bronchoscope guided
tracheal intubation. However, in India, the burden of this disease lies to a great extent in
rural/suburban settings where access to a fiberoptic bronchoscope is unlikely. As a result
these cases are referred to 'higher' centres for management. This imposes undue burden
(logistics/ financial) onto patients and their families. Hence, there is a great need for
anaesthesiologists working at the primary/secondary level healthcare set up to get oriented
to this problem and be able to manage it with conventional options (direct laryngoscopy &
intubation) available to them.
Scientific Contention Direct laryngoscopy remains the foremost among the various techniques
available to access the upper airway and the Macintosh blade has been the most preferred
blade type. In order to improve direct laryngoscopy, many modifications of blade design have
been tested/ compared with the Macintosh blade, but apparently, the clarity as to which
laryngoscope blade is most suited for a given airway remains low. For the majority of
practicing anaesthesiologists, the availability of different laryngoscope designs has only
increased the hit-and-trial option for laryngoscopy.
Since the time it was first introduced, the Macintosh blade (size 1, 2, 3, 4, and 5) has
weathered many newer laryngoscope blade designs and stood by our side with consistent/optimal
performance. Per se, from a technical standpoint, although shaped the same, various sizes of
the Macintosh blade are not exactly similar, the discrepancy becomes obvious when comparing
sizes 1, 2 with 3 & 4. Unfortunately, investigators are still unclear as to how design
characteristics and the various sizes of the Macintosh blade impact the process of direct
laryngoscopy. Generally, the selection of laryngoscope blade (type and sizes) is largely a
function of individual experience and preferences. The absence of predefined parameters for
the selection of the most appropriate laryngoscope blade for a given airway remains
arbitrary. Apparently, an anaesthesiologist will be able to intubate an adult trachea with
any of the laryngoscope blade, however, blade type and size selection assumes significance in
the presence of a difficult airway.
The three factors which influence successful direct laryngoscopy performance are:
i) The ability to place the laryngoscope blade tip in vallecular recess and engage the hyoid
bone. This requires an adequate length of the blade to be introduced orally to reach the
vallecula (transition space between base of the tongue and the epiglottis) position.
ii) The ability to displace the tongue aside for clear view to the glottic-epiglottic region
iii) Achieving a clear line-of-sight to the glottis-opening. To ensure that the tip of the
laryngoscope blade engages the hyoid by placement in the vallecula, an adequate blade length
must be inserted into the oral cavity. Normally, this is easily achieved. However, when faced
with a situation involving reduced mouth opening/inter-incisor distance (e.g.as in case of
SMF), the length of blade that can be inserted into the oral cavity (functional length)
becomes a function of the width of the blade's flange at the incisor point. Thus the size of
the flange, corresponding to the width of the blade that must be accommodated in the oral
cavity assumes particular significance in patients with reduced inter-incisor gap. Typically,
for the Macintosh blade's curved design confers different length to its flange's glossal
(concave) and the palatal (convex) surface, the functional width of its flange increases from
the tip towards the heel [Figure]. Based on the degree of mouth opening restriction and the
available IID (in cm), during preoperative evaluation, one can predict and plan how long a
Macintosh blade length will be required and what size of the blade would suffice to be placed
orally through the available IID.
Hypothesis Development Marks et al, utilized an x-ray based method to devise a method to
evaluate laryngoscope blade design during active laryngoscopy procedure. Technically, they
found that Macintosh sizes 3 and 4 have a more refined blade design that provides greater
degree of forward space enhancement (FSE, allows greater mandibular space for the tongue to
be moved into) than other conventional blades (Miller, Soper, etc.). This FSE-effect gets
further magnified with increase in functional length of the blade (the length of the blade
inside the oral cavity during active laryngoscopy).
Their elaborate work addressed the performance of the laryngoscope blade (size, type)
selection in a theoretical setting. The information gleaned from their assessment offered
valuable suggestions on optimal blade position during direct laryngoscopy and included:
i) Mandibular space 'encroachment/enhancement' with the use of different blade types/sizes,
and ii) 'Line-of-vision' (view to the glottis) versus 'mandibular space restriction' (space
for tongue displacement during laryngoscopy).
However, still, the clinical feasibility of knowledge thus gained from performance assessment
facilitated by x-ray/fluoroscopy is difficult to translate into routine clinical practice.
As the investigator prepares to take the conventional direct laryngoscopy process into
difficult airway situations where the primary difficulty is due to reduced mouth opening,
there is a need to convert theoretical knowledge into clinical suggestions. Investigators
thus contend that unless they get accustomed with greater clarity on the use of routine
equipments, and analyse their practical feasibility in difficult situations, the element of
randomness and subjectivity will continue to be a setback.
