Correspondence

Light-emitting diode illuminant and a plastic single-use blade for intubation during cardiopulmonary resuscitation: an infant manikin study^B

To the Editor,

Although plastic single-use Laryngoscope blades avoid preventable contamination that may occur in reusable metal blades [1-3], several studies have reported on their poor performance, presumably because of insufficient rigidity [4,5]. Recently, light-emitting diode light handles, providing bright and bluish-white light, became commer- cially available. We compared the intubation performance of plastic single-use laryngoscope blades using an LED light handle with reusable laryngoscopes in easy and Difficult airways during cardiopulmonary resuscitation (CPR) in an infant manikin.

Twelve certified anesthetists participated in this study. We evaluated intubation with 3 combinations of size 1 Miller-type laryngoscope blades and handles: (1) reusable metal blade (Miller halogen fiber optic blade; Welch Allyn, NY, USA) and conventional halogen light handle (Fiber optic laryngoscope standard handle; Welch Allyn) (control combination); (2) plastic single-use blade (Crystal disposable laryngoscope blade, Miller type; Penlon, Abingdon, UK) with the same halogen light handle (Plast-Hal combination); and (3) Plastic blade (same type) with an LED light handle (HEINE standard LED laryngoscope handle; HEINE, Herrshing, Germany) (Plast-LED combination). Before the study, the intensity of illumination for each combination was calibrated with a new dry-cell battery (Table 1). Intubation was performed with a 3.0-mm tracheal tube without cuff in an infant manikin (ALS baby trainer 200; Laerdal Medical Japan, Tokyo, Japan). The participating anesthetists intu- bated the manikin’s trachea with 3 combinations of laryngoscope in 2 scenarios: the control scenario and the chest compression scenario. After completing intubations in each scenario, an operator rated the subjective difficulty with each device using a 5-point intubation difficulty scale (IDS).

^? This study was presented at the 58th Annual Meeting of the Japanese Society of Anesthesiologists held on May 19, 2011.

0735-6757/$ - see front matter (C) 2012

We also defined glottic visualization as follows: class I, whole view of vocal cords; class IIa, partial view of vocal cords (more than 50%); class IIb, partial view of vocal cords (up to 50%); class III, only the epiglottis is visible; and class IV, neither the epiglottis nor the glottis is visible [6,7].

There were no significant differences in IDS or glottic visualization between the combinations in the control scenario (Figs. 1 and 2). In the chest compression scenario, the Plast-Hal combination resulted in significantly higher IDS (P = .021) and impeded glottic visualization (P = .038) in comparison with the control combination. There was no significant difference in IDS or glottic visualization between the other combinations (Figs. 1 and 2). Although the differences did not reach statistical significance, in both scenarios, the time to intubate was always the shortest with the conventional combination, second shortest with the Plast-LED combination, and longest with the Plast-Hal combination (Fig. 3).

In the control scenario, a single-use plastic blade was comparable to a reusable metal blade in intubation performance, which was inconsistent with previous studies [4,5]. We assumed that the rigidity of a single-use plastic blade was tolerable in easy airways because laryngoscopy to visualize the glottis in an infant manikin required less force than previous studies using adult patients or manikins. Our results indicated that chest compression impeded the ease of intubation with the Plast-Hal combination. It is likely that the difficult airway associated with chest compression would require additional force during laryngoscopy. Therefore, the insufficient rigidity of a plastic single-use blade became evident, making intubation difficult with reduced glottis visualization. Interestingly, the difficulty of intubation with a plastic single-use blade improved when a LED light handle

Table 1 Illumination by combinations of blades and handles

Code Combination of blade and Intensity of handle illuminant (lux)

Laryngoscope Handle

blade illuminant

3 Plast-LED Plastic single use LED

4570

1 Control	Metal reusable	Halogen	1970
2 Plast-Hal	Plastic single use	Halogen	710

500 Correspondence

Fig. 1 Assessment of difficulty of tracheal intubation with the control combination, the Plast-Hal combination, and the Plast-LED combination, graded by the 5-point IDS, which categorized difficulty into the following ratings: (1) very easy, (2) easy, (3) moderate, (4) difficult, and (5) very difficult. In the control scenario (A), neither chest compressions nor difficult airway was applied. In scenario (B), chest compressions were applied during intubation. The central bold horizontal line indicates the median, and the boxes indicate the lower and upper quartiles. The lower and upper bold horizontal bars indicate the 10th and 90th percentiles, respectively.

*P b .05 compared with the control combination.

Fig. 2 Glottic visualization during laryngoscopy with the control combination, the Plast-Hal combination, and the Plast-LED combination. These are graded, as follows: class I, full view of the vocal cords; class IIa, partial view of the vocal cords (more than 50%); class IIb, partial view of the vocal cords (up to 50%); class III, only the epiglottis is visible; and class IV, neither the epiglottis nor the glottis is visible. In the control scenario (A), neither chest compressions nor difficult airway was applied. In scenario (B), chest compressions were applied during intubation. The central bold horizontal line indicates the median, and the boxes indicate the lower and upper quartiles. The lower and upper bold horizontal bars indicate the 10th and 90th percentiles, respectively. *P b .05 compared with the control combination.

was used. The light irradiance of LEDs was prominent in the blue/green region of the spectrum (400-550 nm) [8], which would be preferable for intubation [9]. It is plausible that this feature of an LED illuminant provided superior conditions for intubation with a plastic single-use blade, which resulted in improved performance comparative to that of a metal reusable blade during chest compression. In addition, the lower light intensity of the Plast-Hal combination might be another possible cause of difficult intubation; however, light intensity of greater than 700 lux is reportedly not necessary for intubation in manikin [10]. Although the light intensity of the Plast-Hal combination was nearly equal to 700 lux during the initial calibration, it was less than half that of the conventional laryngoscope. Therefore, it is possible that the light intensity of the Plast-Hal combination is suboptimal for visualization of a bouncing glottis during chest compression and that the brighter illumination of LEDs is effective for difficult laryngoscopy associated with CPR.

In conclusion, intubation performance was inferior when a plastic single-use blade was used with a conventional

halogen light handle during chest compression. However, with the use of the LED light handle, intubation performance improved and was comparable to the metal reusable blade during simulated CPR of infants. This suggests that an LED illuminant makes single-use blades a viable option in difficult intubations. Further studies in the Clinical context are required to confirm these findings.

Yuki Akihisa MD Koichi Maruyama MD, PhD

Rieko Yamada MD Tomoko Higashi MD, PhD Akira Ogura MD, PhD Tomio Andoh MD, PhD Department of Anesthesiology

Teikyo University School of Medicine Mizonokuchi Hospital. 3-8-3 Mizonokuchi

Takatsu-ku, Kawasaki, Kanagawa 213-8507, Japan E-mail address: [email protected]

doi:10.1016/j.ajem.2011.09.009

Correspondence

Fig. 3 Time to intubate with the control combination, the Plast- Hal combination, and the Plast-LED combination. The central bold horizontal line indicates the median, and the boxes indicate the lower and upper quartiles. The lower and upper bold horizontal bars indicate the 10th and 90th percentiles, respectively.

References

1. Foweraker JE. The laryngoscope as a potential source of cross- infection. J Hosp Infect 1995;29:315-6.
2. Miller DM, Youkhana I, Karunaratne WU, et al. Presence of protein deposits on ‘cleaned’ re-usable anaesthetic equipment. Anaesthesia 2001;56:1069-72.
3. Hirsch N, Beckett A, Collinge J, et al. Lymphocyte contamination of laryngoscope blades-a possible vector for transmission of variant Creuzfeldt-Jacob disease. Anaesthesia 2005;60:664-7.
4. Amour J, Marmion F, Birenbaum A, et al. Comparison of plastic single-use and metal reusable laryngoscope blades for orotracheal intubation during rapid sequence induction of anesthesia. Anesthesi- ology 2006;104:60-4.
5. Rassam S, Wilkes AR, Hall JE, et al. A comparison of 20 laryngoscope blades using intubating manikin: visual analogue scores and forces exerted during laryngoscopy. Anaesthesia 2005;60:384-94.
6. Cormack RS, Lehane J. Difficult tracheal intubation in obstetrics. Anaesthesia 1984;39:1105-11.
7. Ochroch EA, Hollander JE, Kush S, et al. Assessment of Laryngeal view: percentage of Glottic opening score vs Cormack and Lehane grading. Can J Anaesth 1999;46:987-90.
8. Lewis E, Sheraton TE, Hampson MA, et al. Optimal spectral irradiance for laryngoscopy. Paediatr Anaesth 2007;17:606-7.
9. Scholz A, Farnum N, Wilkes AR, et al. Minimum and optimum light output of Macintosh size 3 laryngoscopy blades: a manikin study. Anaesthesia 2007;62:163-8.
10. Malan CA, Scholz A, Wilkes AR, et al. Minimum and optimum light requirements for laryngoscopy in paediatric anaesthesia: a manikin study. Anaesthesia 2008;63:65-70.

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subcutaneous emphysema: an immediate call for chest computed tomographic scan or ultrasonography

To the Editor,

I have read the interesting article by Amrein et al [1] in a recent issue of the journal regarding posttraumatic Occult pneumothorax, which is now increasingly recognized due to the widespread availability of computed tomographic scans and the advent of the extended focused assessment with sonography for trauma (eFAST) in most centers. The case not only exemplified the phenomenon of occult pneumothorax but also the predictability of occult pneumo- thorax. The presence of subcutaneous emphysema in the neck or thoracic wall whether clinically or on chest x-ray should be an immediate trigger for obtaining a Chest CT scan or ultrasonography to rule out pneumothorax for 3 reasons. First and most obvious is the low sensitivity of the anteroposterior (AP) chest x-ray in detecting pneumothorax in the Supine patient (in trauma patients, because of restrictions regarding cervical spine immobilization, AP chest x-ray is usually the most feasible initial imaging modality). Second, is the ability of subcutaneous emphysema to predict for the presence of a pneumothorax. In their study, Ball et al [2] concluded that subcutaneous emphysema is the strongest independent predictor for the presence of a pneumothorax (odds ratio, 5.47; 95% confidence interval 1.68-17.75; P = .005). The existence of other predictors such as rib fractures (which was evident in the presented case) and/or pulmonary contusions will further increase the likelihood of the presence of a pneumothorax. Third, the presence of subcutaneous emphysema can obscure any underlying pleural air, further limiting the ability of the chest

x-ray in capturing the pneumothorax.

For these reasons, the presence of subcutaneous emphy- sema should call for a more advanced imaging modality, whether chest CT scan or ultrasonography, which both have a higher sensitivity to detect pneumothorax than the chest x-ray. In centers utilizing the eFAST technology, ultraso- nography might be superior due to its high sensitivity approaching 100%, its availability at bedside without the need for transporting an unstable patient, and its low profile for radiocarcinogenesis [3].

Hesham R. Omar MD Internal Medicine Department Mercy Hospital and Medical Center

Chicago, IL, USA E-mail address: [email protected]

doi:10.1016/j.ajem.2011.10.029

References

[1] Amrein K, Sourij H, Mader J, Amrein S, Robl T. Occult pneumothorax on chest x-ray. Am J Emerg Med 2011;29(8):959.e3-4.