- Email: [email protected]
Overcoming the difficulties of bougie-assisted endotracheal intubation
Correspondence / American Journal of Emergency Medicine 32 (2016) 100–112
Yoichi Katayama, MD Department of Emergency Medicine Sapporo Medical University, Sapporo, Japan E-mail address: [email protected] Seizan Tanabe, MD, PhD Emergency Life-Saving Technique Academy of Tokyo, Tokyo, Japan E-mail address: [email protected] Yasuhiro Yamamoto, MD, PhD Foundation for Ambulance Service Development, Tokyo, Japan E-mail address: [email protected]
http://dx.doi.org/10.1016/j.ajem.2015.10.016
References [1] Joynt KE, Orav EJ, Jha AK. The association between hospital volume and processes, outcomes, and costs of care for congestive heart failure. Ann Intern Med 2011; 154(2):94–102. [2] Kajino K, Iwami T, Daya M, Nishiuchi T, Hayashi Y, Kitamura T, et al. Impact of transport to critical care medical centers on outcomes after out-of-hospital cardiac arrest. Resuscitation 2010;81(5):549–54. [3] Kontos MC, Wang Y, Chaudhry SI, Vetrovec GW, Curtis J, Messenger J, et al. Lower hospital volume is associated with higher in-hospital mortality in patients undergoing primary percutaneous coronary intervention for ST-segment-elevation myocardial infarction: a report from the NCDR. Circ Cardiovasc Qual Outcomes 2013;6(6): 659–67. [4] McGrath PD, Wennberg DE, Dickens Jr JD, Siewers AE, Lucas FL, Malenka DJ, et al. Relation between operator and hospital volume and outcomes following percutaneous coronary interventions in the era of the coronary stent. JAMA 2000;284(24): 3139–44. [5] The Ministry of Health, Labour and Welfare. Kyumeikyukyu-center no hyokakekka nit suite (Heisei 26 nendo). Available at: http://www.mhlw.go.jp/stf/seisakunitsuite/ bunya/0000063335.html. [Accessed on September 28, 2015]. [6] Fire and Disaster Management Agency. Heisei26 Kyukyukyujono genkyo. http://www. fdma.go.jp/neuter/topics/fieldList9_3.html. [Accessed on September 28, 2015]. [7] The Japanese Circulation Society. Japanese Registry of All Cardiac and Vascular Diseases 2013 data. Available at: http://jroadinfo.ncvc.go.jp/?page_id=13. [Accessed on September 28, 2015]. [8] Rathore SS, Curtis JP, Chen J, Wang Y, Nallamothu BK, Epstein AJ, et al. Association of door-to-balloon time and mortality in patients admitted to hospital with ST elevation myocardial infarction: national cohort study. BMJ 2009;338:b1807. [9] Peberdy MA, Callaway CW, Neumar RW, Geocadin RG, Zimmerman JL, Connino M, et al. Part 9: post-cardiac arrest care: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2010;122(18 Suppl. 3):S768–86. [10] Fagnoul D, Combes A, De Backer D. Extracorporeal cardiopulmonary resuscitation. Curr Opin Crit Care 2014;20(3):259–65.
Overcoming the difficulties of bougie-assisted endotracheal intubation☆ To the Editor, Pirotte and colleagues [1] reported on 2 cases where a bougie was successfully placed by a direct laryngoscopy; however, after failure of troubleshooting measures, digital manipulation was required to overcome difficulty in advancing the endotracheal tube (ETT) past the vocal cords. In the first case, rapid sequence induction and neuromuscular blockade was used. The second patient was intubated during cardiac arrest with ongoing chest compressions. Laryngoscopy is performed to expose the larynx and overcome the collapse of the laryngeal opening (when anesthesia and/or muscle relaxation is used, as was the case in the first patient) [2,3]. In patients with a CL1 or CL2 view, these 2 goals are usually accomplished simultaneously by experienced anesthesiologists, which has been shown in one ☆ Financial disclosures: none.
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study to occur in 570 of 587 patients [4]. In CL3 patients (only 17 of 587 patients); however, if the Macintosh laryngoscope could overcome the collapse of the laryngeal aperture (13 of 17 patients), tracheal intubation by blind probing was relatively easy (difficult laryngoscopy, but easy intubation). However, if the laryngoscope could not expand the laryngeal aperture (4 of 17 patients), intubation was difficult (difficult laryngoscopy, difficult intubation); therefore, requiring jaw thrust by an assistant to allow easy passage of the tube. During general anesthesia with/without muscle relaxation, any loss of tone in the laryngeal muscles causes collapse of the laryngeal inlet; therefore, without the jaw-thrust maneuver, it is collapsed completely in 10% of patients and partially in 90% [3]. When the jaw-thrust is applied, the laryngeal inlet is completely expanded. One possible explanation for the differences in the size of the laryngeal aperture seen during laryngoscopy versus during a jaw thrust maneuver in patients with difficult intubation may be that the direction of the force applied to the Macintosh laryngoscope differs from that required to lift the laryngeal soft tissues [4]. Even if the tip of the laryngoscope blade is placed correctly in the vallecula, the laryngoscope may not exert force on the hyo-epiglottic ligament (which is required to both lift the epiglottis and expand a collapsed laryngeal opening). On the contrary, a jaw thrust maneuver may lift the laryngeal soft tissues by applying the force in a different direction from that applied by the laryngoscope blade. In some patients in whom the glottis cannot be seen during laryngoscopy (ie, CL3 view), the trachea can still be intubated when an ETT is advanced behind the epiglottis blindly [5,6]. If, in this situation, the tapered tip (or leading edge of a standard bevel tube) can be introduced accurately into the glottis opening (even if only very small), the ETT will spread the opening and will advance into the trachea because the glottis is not small anatomically or pathologically [4]. One possible explanation for failure of bougie-assisted intubation in the first case, despite taking measures known to overcome the difficulties preventing the ETT from being advanced, is that the gap between the bougie and the inside diameter/leading edge of the standard bevel ETT was still too large even after downsizing the ETT to size 6.5 [7], which likely prevented the bevel tip from being accurately introduced into the likely small space between the bougie and glottis opening (due to anesthesia-induced partial collapse of the laryngeal inlet), which prevented the ETT from being advanced into the trachea. Therefore, digital manipulation of the ETT likely closed the gap between the bougie and ETT enough such that the bevel tip was accurately aimed into the space surrounding the bougie thereby spreading the glottis opening when advanced and allowing passage of the tube into the trachea. One possible explanation for failure of bougie-assisted intubation in the second case, despite troubleshooting measures, is as follows. Because rapid sequence intubation was not used, the glottis was not collapsed; however, although the glottis opening was normal, the gap between the bougie and the inside diameter/leading edge of the bevel of the standard 7.5 ETT was substantially large (because it was not downsized, as was done in the first case), which prevented advancement of the tube past the vocal cords, despite use of standard troubleshooting measures, thereby requiring digital manipulation to close the gap and allow advancement of the tube. Reducing the gap without digital manipulation requires using a larger diameter bougie and/or reasonably smaller size ETT to fill the space between the inside diameter/leading edge of the standard bevel tube and the bougie [7]. Another solution to this problem is use of an ETT designed to overcome difficulties encountered during endotracheal intubation. The Parker flex-tip tube (Parker Medical, Englewood, CO) has been shown to be useful in a bougie-assisted endotracheal tube exchange after lung lavage [8] because of its soft, flexible, curved, centered, distal tip, which significantly reduces the gap between the bougie (or tracheal tube exchanger [7] or fiberscope [9]) and the inside surfaces of the tube, which reduces the risk of impinging on laryngeal structures during insertion in trachea. The
112
Correspondence / American Journal of Emergency Medicine 32 (2016) 100–112
superior beveled tip design was shown to have a tendency to allow the tube to smoothly advance through the laryngeal structures into the trachea without a laryngoscope after lung lavage. During fiberoptic intubation using the standard tube, some manipulation was needed to pass the tube in 34 (89%) of 38 patients [9]. The corresponding number of patients for the Parker tube was 11 (29%) of 38 patients (P b .0001). Eric M. Rottenberg, AAS 301B Fenway Road, Columbus OH 43214 Tel.: +1 614 291 4594 E-mail address: [email protected] http://dx.doi.org/10.1016/j.ajem.2015.10.014 References [1] Pirotte M, Pirotte A, Trueger NS. Two cases of digitally assisted bougie intubation: a novel technique for difficult airway management. Am J Emerg Med 2015. http://dx. doi.org/10.1016/j.ajem.2015.04.052 [pii: S0735-6757(15)00319-8]. [2] Benumof JL. Management of the difficult adult airway. With special emphasis on awake tracheal intubation. Anesthesiology 1991;75:1087–110. [3] Murashima K, Fukutome T. Effect of jaw-thrust manoeuvre on the laryngeal inlet. Anaesthesia 1998;53:203–4. [4] Takenaka I, Aoyama K, Kadoya T, Sata T, Shigematsu A. Fibreoptic assessment of laryngeal aperture in patients with difficult laryngoscopy. Can J Anaesth 1999; 46:226–31. [5] Williams KN, Carli F, Cormack RS. Unexpected, difficult laryngoscopy: a prospective survey in routine general surgery. Br J Anaesth 1991;66:38–44. [6] Benumof JL. Difficult laryngoscopy: obtaining the best view (Editorial). Can J Anaesth 1994;41:361–5. [7] Makino H, Katoh T, Kobayashi S, Bito H, Sato S. The effects of tracheal tube tip design and tube thickness on laryngeal pass ability during oral tube exchange with an introducer. Anesth Analg 2003;97:285–8. [8] Kitagawa H, Imashuku Y, Yamazaki T. The Parker Flex-Tip tube is useful in a bougieassisted endotracheal tube exchange after lung lavage. J Cardiothorac Vasc Anesth 2010;24:901. [9] Kristensen MS. The Parker Flex-Tip tube versus a standard tube for fiberoptic orotracheal intubation: a randomized double-blind study. Anesthesiology 2003;98: 354–8.
The use of ultrasound in ocular diseases☆ To the Editor We read with great interest the recent published article by Budhram et al [1] in which authors aimed to determine the prevalence of monocular and binocular mobile vitreous opacities in the vitreous chamber in an asymptomatic population at normal and high gain levels. In conclusion, the authors stated that mobile vitreous opacity in the vitreous ☆ Conflict of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
chamber was uncommon at normal gain levels but relatively common at high gain settings and found both unilaterally and bilaterally. Although it is a well-designed and straightforward study, there is a point that we would like to add for a proper understanding of the issue, to avoid giving a wrong message to readers. Ophthalmic ultrasound (A-scan and B-scan) is performed primarily for the 3 following reasons: First, when opaque media prevent direct view of the ocular fundus and periphery, ultrasound determines the presence or absence of ocular tumors, retinal detachment, foreign bodies, or other pathologic abnormality. Second, when media are clear, ultrasound allows imaging of intraocular and extraocular structures, such as optic nerve head drusen, orbital structures and lesions, and internal structure of intraocular lesions. Third, ultrasound allows the measurement of axial length before cataract surgery to determine intraocular lens power [2]. In ophthalmology practice, we perform ultrasonography only if it is necessary to make the diagnosis regarding above conditions. Furthermore, although quite prevalent, as determined in the original study, vitreous opacities have not been considered a significant problem meriting therapeutic intervention, especially if they are not symptomatic [3]. So, the main idea of the original study should be understood correctly and physicians should not perform ocular ultrasonography instead of the ophthalmic examination. Cem Ozgonul, MD Department of Ophthalmology, Van Military Hospital, Van, Turkey Corresponding author at: Department of Ophthalmology, Van Military Hospital, Iskele Ave, Van, Turkey. Tel.: +90 555 558 44 36 E-mail address: [email protected] Murat Kucukevcilioglu, MD Department of Ophthalmology, Gulhane Military Medical Academy Ankara, Turkey Gokcen Gokce, MD Department of Ophthalmology, Kayseri Military Hospital, Kayseri, Turkey
http://dx.doi.org/10.1016/j.ajem.2015.10.047 References [1] Budhram G, Cronsell J, Schroeder M, Sautner J, Schoenfed E, Elia T, et al. Mobile vitreous opacities on ocular ultrasound are not always pathologic: a cross-sectional survey in an asymptomatic population. Am J Emerg Med 2015. http://dx.doi.org/10.1016/j. ajem.2015.09.017. [2] Kendall CJ, Prager TC, Cheng H, Gombos D, Tang RA, Schiffman JS. Diagnostic ophthalmic ultrasound for radiologists. Neuroimaging Clin N Am 2015;25(3): 327–65. [3] Mamou J, Wa CA, Yee KM, Silverman RH, Ketterling JA, Sadun AA, et al. Ultrasoundbased quantification of vitreous floaters correlates with contrast sensitivity and quality of life. Invest Ophthalmol Vis Sci 2015;56(3):1611–7.
Yoichi Katayama, MD Department of Emergency Medicine Sapporo Medical University, Sapporo, Japan E-mail address: [email protected] Seizan Tanabe, MD, PhD Emergency Life-Saving Technique Academy of Tokyo, Tokyo, Japan E-mail address: [email protected] Yasuhiro Yamamoto, MD, PhD Foundation for Ambulance Service Development, Tokyo, Japan E-mail address: [email protected]
http://dx.doi.org/10.1016/j.ajem.2015.10.016
References [1] Joynt KE, Orav EJ, Jha AK. The association between hospital volume and processes, outcomes, and costs of care for congestive heart failure. Ann Intern Med 2011; 154(2):94–102. [2] Kajino K, Iwami T, Daya M, Nishiuchi T, Hayashi Y, Kitamura T, et al. Impact of transport to critical care medical centers on outcomes after out-of-hospital cardiac arrest. Resuscitation 2010;81(5):549–54. [3] Kontos MC, Wang Y, Chaudhry SI, Vetrovec GW, Curtis J, Messenger J, et al. Lower hospital volume is associated with higher in-hospital mortality in patients undergoing primary percutaneous coronary intervention for ST-segment-elevation myocardial infarction: a report from the NCDR. Circ Cardiovasc Qual Outcomes 2013;6(6): 659–67. [4] McGrath PD, Wennberg DE, Dickens Jr JD, Siewers AE, Lucas FL, Malenka DJ, et al. Relation between operator and hospital volume and outcomes following percutaneous coronary interventions in the era of the coronary stent. JAMA 2000;284(24): 3139–44. [5] The Ministry of Health, Labour and Welfare. Kyumeikyukyu-center no hyokakekka nit suite (Heisei 26 nendo). Available at: http://www.mhlw.go.jp/stf/seisakunitsuite/ bunya/0000063335.html. [Accessed on September 28, 2015]. [6] Fire and Disaster Management Agency. Heisei26 Kyukyukyujono genkyo. http://www. fdma.go.jp/neuter/topics/fieldList9_3.html. [Accessed on September 28, 2015]. [7] The Japanese Circulation Society. Japanese Registry of All Cardiac and Vascular Diseases 2013 data. Available at: http://jroadinfo.ncvc.go.jp/?page_id=13. [Accessed on September 28, 2015]. [8] Rathore SS, Curtis JP, Chen J, Wang Y, Nallamothu BK, Epstein AJ, et al. Association of door-to-balloon time and mortality in patients admitted to hospital with ST elevation myocardial infarction: national cohort study. BMJ 2009;338:b1807. [9] Peberdy MA, Callaway CW, Neumar RW, Geocadin RG, Zimmerman JL, Connino M, et al. Part 9: post-cardiac arrest care: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2010;122(18 Suppl. 3):S768–86. [10] Fagnoul D, Combes A, De Backer D. Extracorporeal cardiopulmonary resuscitation. Curr Opin Crit Care 2014;20(3):259–65.
Overcoming the difficulties of bougie-assisted endotracheal intubation☆ To the Editor, Pirotte and colleagues [1] reported on 2 cases where a bougie was successfully placed by a direct laryngoscopy; however, after failure of troubleshooting measures, digital manipulation was required to overcome difficulty in advancing the endotracheal tube (ETT) past the vocal cords. In the first case, rapid sequence induction and neuromuscular blockade was used. The second patient was intubated during cardiac arrest with ongoing chest compressions. Laryngoscopy is performed to expose the larynx and overcome the collapse of the laryngeal opening (when anesthesia and/or muscle relaxation is used, as was the case in the first patient) [2,3]. In patients with a CL1 or CL2 view, these 2 goals are usually accomplished simultaneously by experienced anesthesiologists, which has been shown in one ☆ Financial disclosures: none.
111
study to occur in 570 of 587 patients [4]. In CL3 patients (only 17 of 587 patients); however, if the Macintosh laryngoscope could overcome the collapse of the laryngeal aperture (13 of 17 patients), tracheal intubation by blind probing was relatively easy (difficult laryngoscopy, but easy intubation). However, if the laryngoscope could not expand the laryngeal aperture (4 of 17 patients), intubation was difficult (difficult laryngoscopy, difficult intubation); therefore, requiring jaw thrust by an assistant to allow easy passage of the tube. During general anesthesia with/without muscle relaxation, any loss of tone in the laryngeal muscles causes collapse of the laryngeal inlet; therefore, without the jaw-thrust maneuver, it is collapsed completely in 10% of patients and partially in 90% [3]. When the jaw-thrust is applied, the laryngeal inlet is completely expanded. One possible explanation for the differences in the size of the laryngeal aperture seen during laryngoscopy versus during a jaw thrust maneuver in patients with difficult intubation may be that the direction of the force applied to the Macintosh laryngoscope differs from that required to lift the laryngeal soft tissues [4]. Even if the tip of the laryngoscope blade is placed correctly in the vallecula, the laryngoscope may not exert force on the hyo-epiglottic ligament (which is required to both lift the epiglottis and expand a collapsed laryngeal opening). On the contrary, a jaw thrust maneuver may lift the laryngeal soft tissues by applying the force in a different direction from that applied by the laryngoscope blade. In some patients in whom the glottis cannot be seen during laryngoscopy (ie, CL3 view), the trachea can still be intubated when an ETT is advanced behind the epiglottis blindly [5,6]. If, in this situation, the tapered tip (or leading edge of a standard bevel tube) can be introduced accurately into the glottis opening (even if only very small), the ETT will spread the opening and will advance into the trachea because the glottis is not small anatomically or pathologically [4]. One possible explanation for failure of bougie-assisted intubation in the first case, despite taking measures known to overcome the difficulties preventing the ETT from being advanced, is that the gap between the bougie and the inside diameter/leading edge of the standard bevel ETT was still too large even after downsizing the ETT to size 6.5 [7], which likely prevented the bevel tip from being accurately introduced into the likely small space between the bougie and glottis opening (due to anesthesia-induced partial collapse of the laryngeal inlet), which prevented the ETT from being advanced into the trachea. Therefore, digital manipulation of the ETT likely closed the gap between the bougie and ETT enough such that the bevel tip was accurately aimed into the space surrounding the bougie thereby spreading the glottis opening when advanced and allowing passage of the tube into the trachea. One possible explanation for failure of bougie-assisted intubation in the second case, despite troubleshooting measures, is as follows. Because rapid sequence intubation was not used, the glottis was not collapsed; however, although the glottis opening was normal, the gap between the bougie and the inside diameter/leading edge of the bevel of the standard 7.5 ETT was substantially large (because it was not downsized, as was done in the first case), which prevented advancement of the tube past the vocal cords, despite use of standard troubleshooting measures, thereby requiring digital manipulation to close the gap and allow advancement of the tube. Reducing the gap without digital manipulation requires using a larger diameter bougie and/or reasonably smaller size ETT to fill the space between the inside diameter/leading edge of the standard bevel tube and the bougie [7]. Another solution to this problem is use of an ETT designed to overcome difficulties encountered during endotracheal intubation. The Parker flex-tip tube (Parker Medical, Englewood, CO) has been shown to be useful in a bougie-assisted endotracheal tube exchange after lung lavage [8] because of its soft, flexible, curved, centered, distal tip, which significantly reduces the gap between the bougie (or tracheal tube exchanger [7] or fiberscope [9]) and the inside surfaces of the tube, which reduces the risk of impinging on laryngeal structures during insertion in trachea. The
112
Correspondence / American Journal of Emergency Medicine 32 (2016) 100–112
superior beveled tip design was shown to have a tendency to allow the tube to smoothly advance through the laryngeal structures into the trachea without a laryngoscope after lung lavage. During fiberoptic intubation using the standard tube, some manipulation was needed to pass the tube in 34 (89%) of 38 patients [9]. The corresponding number of patients for the Parker tube was 11 (29%) of 38 patients (P b .0001). Eric M. Rottenberg, AAS 301B Fenway Road, Columbus OH 43214 Tel.: +1 614 291 4594 E-mail address: [email protected] http://dx.doi.org/10.1016/j.ajem.2015.10.014 References [1] Pirotte M, Pirotte A, Trueger NS. Two cases of digitally assisted bougie intubation: a novel technique for difficult airway management. Am J Emerg Med 2015. http://dx. doi.org/10.1016/j.ajem.2015.04.052 [pii: S0735-6757(15)00319-8]. [2] Benumof JL. Management of the difficult adult airway. With special emphasis on awake tracheal intubation. Anesthesiology 1991;75:1087–110. [3] Murashima K, Fukutome T. Effect of jaw-thrust manoeuvre on the laryngeal inlet. Anaesthesia 1998;53:203–4. [4] Takenaka I, Aoyama K, Kadoya T, Sata T, Shigematsu A. Fibreoptic assessment of laryngeal aperture in patients with difficult laryngoscopy. Can J Anaesth 1999; 46:226–31. [5] Williams KN, Carli F, Cormack RS. Unexpected, difficult laryngoscopy: a prospective survey in routine general surgery. Br J Anaesth 1991;66:38–44. [6] Benumof JL. Difficult laryngoscopy: obtaining the best view (Editorial). Can J Anaesth 1994;41:361–5. [7] Makino H, Katoh T, Kobayashi S, Bito H, Sato S. The effects of tracheal tube tip design and tube thickness on laryngeal pass ability during oral tube exchange with an introducer. Anesth Analg 2003;97:285–8. [8] Kitagawa H, Imashuku Y, Yamazaki T. The Parker Flex-Tip tube is useful in a bougieassisted endotracheal tube exchange after lung lavage. J Cardiothorac Vasc Anesth 2010;24:901. [9] Kristensen MS. The Parker Flex-Tip tube versus a standard tube for fiberoptic orotracheal intubation: a randomized double-blind study. Anesthesiology 2003;98: 354–8.
The use of ultrasound in ocular diseases☆ To the Editor We read with great interest the recent published article by Budhram et al [1] in which authors aimed to determine the prevalence of monocular and binocular mobile vitreous opacities in the vitreous chamber in an asymptomatic population at normal and high gain levels. In conclusion, the authors stated that mobile vitreous opacity in the vitreous ☆ Conflict of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
chamber was uncommon at normal gain levels but relatively common at high gain settings and found both unilaterally and bilaterally. Although it is a well-designed and straightforward study, there is a point that we would like to add for a proper understanding of the issue, to avoid giving a wrong message to readers. Ophthalmic ultrasound (A-scan and B-scan) is performed primarily for the 3 following reasons: First, when opaque media prevent direct view of the ocular fundus and periphery, ultrasound determines the presence or absence of ocular tumors, retinal detachment, foreign bodies, or other pathologic abnormality. Second, when media are clear, ultrasound allows imaging of intraocular and extraocular structures, such as optic nerve head drusen, orbital structures and lesions, and internal structure of intraocular lesions. Third, ultrasound allows the measurement of axial length before cataract surgery to determine intraocular lens power [2]. In ophthalmology practice, we perform ultrasonography only if it is necessary to make the diagnosis regarding above conditions. Furthermore, although quite prevalent, as determined in the original study, vitreous opacities have not been considered a significant problem meriting therapeutic intervention, especially if they are not symptomatic [3]. So, the main idea of the original study should be understood correctly and physicians should not perform ocular ultrasonography instead of the ophthalmic examination. Cem Ozgonul, MD Department of Ophthalmology, Van Military Hospital, Van, Turkey Corresponding author at: Department of Ophthalmology, Van Military Hospital, Iskele Ave, Van, Turkey. Tel.: +90 555 558 44 36 E-mail address: [email protected] Murat Kucukevcilioglu, MD Department of Ophthalmology, Gulhane Military Medical Academy Ankara, Turkey Gokcen Gokce, MD Department of Ophthalmology, Kayseri Military Hospital, Kayseri, Turkey
http://dx.doi.org/10.1016/j.ajem.2015.10.047 References [1] Budhram G, Cronsell J, Schroeder M, Sautner J, Schoenfed E, Elia T, et al. Mobile vitreous opacities on ocular ultrasound are not always pathologic: a cross-sectional survey in an asymptomatic population. Am J Emerg Med 2015. http://dx.doi.org/10.1016/j. ajem.2015.09.017. [2] Kendall CJ, Prager TC, Cheng H, Gombos D, Tang RA, Schiffman JS. Diagnostic ophthalmic ultrasound for radiologists. Neuroimaging Clin N Am 2015;25(3): 327–65. [3] Mamou J, Wa CA, Yee KM, Silverman RH, Ketterling JA, Sadun AA, et al. Ultrasoundbased quantification of vitreous floaters correlates with contrast sensitivity and quality of life. Invest Ophthalmol Vis Sci 2015;56(3):1611–7.