Send letter to journal:
Re: I want to know

Dear Editor,

Send letter to journal:
Re: Assessment score or not !!

Dear Editor:

ASSESSMENT SCORE OR NOT!!

The LOW COST RES-Q-SCOPE(R) where digital video technology makes life a little easier. The patented and FDA Registered RES-Q-SCOPE(R)is readily available and considered essential in the emergency field, where the emergency needs to be dealt with quickly and effectively. The situations commonly found more frecuently by Paramedics, Medics in the military, First responders, Rescue Units, mass casualties personnel and the Emergency Room. The RES-Q- SCOPE(R) stands to the challenge and is readily available at very low cost. A state of the art Hand Held FIELD VIDEO LARYNGOSCOPE, a low cost self contained, self powered device, with disposability advantages which enables rapid serial intubations in the field. The RES-Q-SCOPE(R) is the only Laryngoscope in the world which is designed to avoid free hand ET uncertainty by actually PRE-LOADING A STANDARD ENDOTRACHEAL TUBE 6-8.5 mm prior to intubation.

The RES-Q-SCOPE (R) is a patented and FDA Registered and Listed, multi-function field video laryngoscope, which uses cutting edge digital image technology featuring a multiple positional colour 2.75" LCD screen to externally visualize the intubation process in the field. The RES-Q-SCOPE (R) requires modest learning curve, to slide the device into position to visualize the epiglottis with little effort. The RES-Q-SCOPE(R) is spine injury friendly with minimal need, if any, to re-position the C-spine in case of suspected neck injury. Further, the RES-Q-SCOPE (R) itself, features a channel where a standard endotracheal tube can be easily pre- loaded into the device. SHORT AND OBESE NECKS MAKE LITTLE DIFFERENCE WHEN USING THE RES-Q-SCOPE(R). A light source for external visualization of the intubation process, as the endotracheal tube passes into the trachea. The process can be seen through a small colour LCD screen, which has the ability to adopt multiple positions, so that the PRACTITONEAR CAN BE LOCATED AT THE SIDE OF THE PATIENT OR AT MULTIPLE OTHER POSITIONS AROUND THE PATIENT. A vacuum source can be attached to an external adaptor provided, to assist clearing fluids that may be present in the throat. The same channel can be reversibly, used to provide oxygen if needed. A disposable unit can be easily detached and discarded. Thus, multiple clean intubations, may be performed in the field in a very short time span. The simple attachment of a new disposable unit allows very rapid serial intubation of multiple patients in a disaster theatre or emergency scene. The RES-Q-SCOPE (R) is powered with a rechargeable LiOn long duration battery, also allowing for serial intubations when needed. Additionally an emergency dry cell pack is also available using 4 AA's to power the unit under extreme conditions such as combat settings.

Send letter to journal:
Re: Letter to the Editor

Dear Editor,

We read with interest the recent paper by Reed et al. [1] regarding the LEMON mnemonic [2] and its ability to predict difficult intubation in the ED. We are particularly pleased that the authors concluded that this clinical tool was able to successfully stratify the risk of intubation difficulty in the ED, though this was never the intent in its design.

Predicting a ‘difficult intubation’ has proven to be elusive [3,4]. The first problem is in defining ‘difficult intubation’ [5,6]. The process is composed of two interdependent technical skills: exposing the glottis by employing a conventional laryngoscope; and placing an endotracheal tube through the cords into the trachea. The former is generally termed ‘difficult’ if one gets a poor view of the target (Cormack Lehane grade 3 or 4 view) [2]; the latter, if after an arbitrary number of attempts (usually 3), the tube cannot be placed [2].

Many authors addressing this issue have attempted to identify anatomical predictors, collections of predictors and even weighted scoring systems of identified factors in an attempt to clearly separate those that can be intubated orally following induction and paralysis, from those that cannot [7-11]. This latter group is ordinarily intubated ‘awake’ employing topical anesthesia and sedation and devices such as bronchoscopes. Varying degrees of sensitivity and specificity have been touted. However, the predictive value in defining who can and who cannot be intubated for all of them is so poor as to be clinically useless [10,12]. Of course, such evaluations are predicated on the fact that the intubation is planned using a standard laryngoscope and blade; a premise that is likely to be severely challenged as video and fiberoptic intubation devices come into broader use.

Though we are pleased that the authors have found LEMON useful clinically in stratifying risk, we have several comments:

> The issue of access through the oral cavity, and exactly how much of the posterior pharynx one can see employing simple manoeuvres like the Mallampati Scale, has been repeatedly demonstrated to be of value in evaluating the airway for difficulty [7,8,13-15]. While Mallampati’s classically described manoeuvre, which requires the patient to sit T M up and cooperatively open the mouth and protrude the tongue, is not generally possible in emergency situations, we believe that evaluation of the tongue/oropharynx ratio is still important. Thus, we advocate using a tongue blade to examine the oropharynx and estimate the Mallampati score, even when the patient is uncooperative or unconscious. The key element is whether the tongue is believed to be too large to permit oral, direct laryngoscopy.

> The failure to evaluate the airway prior to employing paralytic agents is the single most important contributor to airway management failure and a poor outcome. LEMON is primarily intended to ensure and expedite as complete an evaluation as possible recognizing the realities of emergency airway management [5,6,16,17]. The most important aspect of the guideline, though, lies in sensitivity, not specificity. The intent is not to determine, with precision, whether the patient will, or will not be a difficult laryngoscopy. Rather, the goal is to identify every patient for whom laryngoscopy might be difficult, recognizing that in many identified cases, laryngoscopy may well turn out to be reassuringly routine.

> Clarify the dimensions intended to be evaluated by the ‘Evaluate 332’ rule (Fig 1 ‘E’ and Table 1). The intent of this portion of the mnemonic is to focus one’s attention on the geometric principles inherent in direct laryngoscopy.

> The first ‘three’ addresses access to the airway by the oral route and provides information supplemental to that of the Mallampati score

> The second ‘three’ is meant to direct the evaluator’s attention to the volume of the mandibular space, though we recognize that the length from the tip of the chin to the 'chin-neck' junction is but one of the three dimensions.

> The ‘two’ is intended to focus the evaluator on the location of the larynx with respect to the base of the tongue. A distance less that two finger breadths may indicate that the larynx is too high and will be obscured by the base of the tongue; a larynx further down the neck may place it beyond the ‘horizon’ that can be established during oral laryngoscopy.

In closing, we applaud the investigators in performing this study and demonstrating that LEMON was useful as it was intended. However, we also wish to forward a cautionary note with respect to the Mallampati maneuver: we recognize that it may not be possible to perform in all comers, but it is a valuable part of the airway exam, particularly when a patient is found to have a class 3 or 4 view, and it is worth seeking, even if the search is somewhat difficult.

Sincerely,

Michael F. Murphy, MD, FRCPC(Anes), FRCPC(EM)
Departments of Emergency Medicine and Anesthesia
Carolinas Medical Center
University of North Carolina
Charlotte, NC

Ron M. Walls, MD, FRCPC (EM), FAAEM, FACEP
Department of Emergency Medicine
Brigham and Women’s Hospital
Harvard Medical School
Boston, MA

References

1. Reed M, Dunn M, McKeown DW. Can an airway assessment score predict difficulty at intubation in the emergency department? Emerg Med J 2005;22:99-102.

2. Murphy M, Walls RM. Identification of the difficult and failed airway. In: Walls RM, Murphy MF, Luten R, eds. Manual of emergency airway management. Philadelphia: Lippincott, Williams, Wilkins; 2004:70-81.

3. Karkouti K, Rose DK, Ferris LE, Wigglesworth DF, Meisami-Fard T, Lee H. Interobserver reliability of ten tests used for predicting difficult tracheal intubation. Can J Anaesth 1996;43(6):554-9.

4. Rose DK, Cohen MM. The airway: problems and predictions in 18,500 patients. Can J Anaesth 1994;41(5 Pt 1):372-83.

5. Practice guidelines for management of the difficult airway. A report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Anesthesiology 1993;78(3):597-602.

6. Practice guidelines for management of the difficult airway: an updated report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Anesthesiology 2003;98(5):1269-77.

7. Frerk CM. Predicting difficult intubation. Anaesthesia 1991;46(12):1005-8.

8. el-Ganzouri AR, McCarthy RJ, Tuman KJ, Tanck EN, Ivankovich AD. Preoperative airway assessment: predictive value of a multivariate risk index. Anesth Analg 1996;82(6):1197- 204.

9. Savva D, Maroof M. Predicting difficult endotracheal intubation. Anesth Analg 1996;83(5):1129.

10. Wilson ME, Spiegelhalter D, Robertson JA, Lesser P. Predicting difficult intubation. Br J Anaesth 1988;61(2):211-6.

11. Cass NM, James NR, Lines V. Difficult direct laryngoscopy complicating intubation for anaesthesia. Br Med J 1956(4965):488-9.

12. Tse JC, Rimm EB, Hussain A. Predicting difficult endotracheal intubation in surgical patients scheduled for general anesthesia: a prospective blind study. Anesth Analg 1995;81(2):254-8.

13. Langenstein H, Cunitz G. [Difficult intubation in adults]. Anaesthesist 1996;45(4):372- 83.

14. Mallampati SR. Clinical sign to predict difficult tracheal intubation (hypothesis). Can Anaesth Soc J 1983;30(3 Pt 1):316-7.

15. Mallampati SR, Gatt SP, Gugino LD, et al. A clinical sign to predict difficult tracheal intubation: a prospective study. Can Anaesth Soc J 1985;32(4):429-34.

16. Cheney FW, Posner KL, Caplan RA. Adverse respiratory events infrequently leading to malpractice suits. A closed claims analysis. Anesthesiology 1991;75(6):932 -9.

Send letter to journal:
Re: A limited place for the LEMON score in airway assessment

Dear Editor,

We read with interest the article by MJ Reed et al. As they have mentioned there have been numerous attempts to devise scoring systems for airway assessment, however these scores have been undermined by low sensitivity and specificity. Furthermore Positive predictive values for these tests range from 4 – 60% [1], we believe that such a low predictive value has significant implications for airway management particularly in the Emergency Department. With a positive predictive value of 50% at least half of difficult intubations are likely to be unexpected. Whilst the morbidity associated with a difficult intubation is clear to all, some patients may be subjected to unnecessarily invasive techniques that may not be required.

In the words of Levintine “Direct Laryngoscopy with pharmacological adjuncts is very successful, very fast and has low complication rates” [2]. The authors of the study do not state at which LEMON score a patient’s airway is anticipated to be difficult. Assuming a score of >3 the positive predictive value would be 47%. The study quotes a rate of 2% difficult intubations in the Emergency Department; the study rate of 42 difficult intubations in 156 patients therefore seems to be abnormally high, possibly due to the inclusion of grade II laryngoscopic view as difficult. We would question the classification of Cormack and Lehane grade II laryngoscopy as “difficult”, most Emergency Departments are equipped with bougies making it possible to easily intubate with this view [3].

Although the LEMON score is referred to as an “airway assessment” it is in fact an intubation assessment. No patient dies from failure to intubate, rather it is failed oxygenation. In the absence of an airway assessment with 100% accuracy then airway assessment needs to be holistic. The American Society of Anaesthesiologists published guidelines suggesting airway assessment must also take into account difficulty in ventilation, patient co-operation, potential surgical airway access and maintaining oxygenation throughout airway management procedures as these problems may occur alone or in combination [4]. Whilst anaesthestists have the luxury of time when assessing an airway we feel the limited time in the Emergency department would be better spent considering these issues rather than calculating a LEMON score.

The harsh reality is that there will be no test that has 100% specificity and sensitivity. The only way to deal with the airway in the Emergency department is to be prepared for the unanticipated difficulties: with experienced assistants, difficult airway trolleys and a plan B, all of which should be standard practice. There is little margin for error in airway management. We believe that a test that makes airway management “more likely” to be difficult is of limited value in the emergency department.

Dr S. Dorrian
SHO Critical Care New Cross hospital
Wolverhampton

Dr S. Nagaiyan
SpR Anaesthetics New Cross hospital
Wolverhampton

References

1. Das S, Pearce A. Pre-operative airway evaluation Anaesthesia 2002 Aug; 57(8):824.

2. Levitan RM, Kush S, Hollander JE Devices for difficult airway management in academic emergency departments: results of a national survey Annals of Emergency Medicine 1999 Jun; 33(6): 694-8.

3. Morton T, Brady S, Clancy M Difficult airway equipment in English Emergency Departments Anaesthesia 2000 May; 55(5):485-8.