Airway ultrasound for patients anticipated to have a difficult airway: Perspective for personalized medicine

Airway ultrasound allows for precise airway evaluation, particularly for assessing the difficult airway and the potential for front of neck access. Many studies have shown that identification of the cricothyroid membrane by airway ultrasound is more accurate than digital palpation. However, no reports to date have provided clinical evidence that ultrasound identification of the cricothyroid membrane increases the success rate of cricothyroidotomy. This is a narrative review which describes patients with difficult airways for whom airway ultrasound may have been useful for clinical decision making. The role of airway ultrasound for the evaluation of difficult airways is summarized and an approach to the use of ultrasound for airway management is proposed. The goal of this review is to present practical applications of airway ultrasound for patients predicted to have a difficult airway and who undergo cricothyroidotomy.     

Airway management in the critically ill patient

Decisions regarding the application and care of airways in respiratory failure are important determinants of outcome in critically ill patients. Specialized procedures for institution of translaryngeal intubation in difficult circumstances, such as fiberoptic intubation, and provision of immediate surgical airway access, such as cricothyroidotomy, are requisite skills for the intensivist. The evolving application of standard techniques and advent of newer procedures for airway cannulation require extensive experience and cognitive skills in the management of tracheal intubation to enhance patient benefit and limit adverse effects from tracheal intubation.     

Usage of airway ultrasound as an assessment and prediction tool of a difficult airway management

Airway assessment is important in emergency airway management. A difficult airway can lead to life-threatening complications. A perfect airway assessment tool does not exist and unanticipated difficulty will remain unforeseen. Current bedside clinical predictors of the difficult airway are unreliable but airway ultrasound can be used as an adjunct to predict difficult laryngoscopy.We report a case of a 60-year-old man presenting to the emergency department with shortness of breath, hoarseness of voice and stridor. Airway ultrasound revealed a large laryngeal mass narrowing the upper airway, extending to bilateral vocal cords with heterogenous echogenicity. In view of impending complete upper airway obstruction, acute respiratory distress and airway ultrasound findings, urgent emergency tracheostomy was chosen as definitive airway over endotracheal intubation or surgical cricothyroidotomy.Point of care ultrasound (POCUS) was used to evaluate this patient with severe upper airway obstruction. A laryngeal mass was detected by ultrasound and this pointed towards the presence of a difficult airway. POCUS was a good non-invasive tool used for airway assessment in this uncooperative and unstable patient. Ultrasound predictors of the difficult airway include the inability to visualize the hyoid bone, short hyomental distance ratio, high pretracheal anterior neck thickness and large tongue size. Besides airway assessment, ultrasound can also help to predict endotracheal tube size, confirm intubation and guide emergency airway procedures such as cricothyroidotomy and tracheostomy.Point of care ultrasound of the upper airway can be used in airway assessment to identify distorted airway anatomy, pathological lesions and guide treatment decisions.     

Prehospital management of the difficult airway: a prospective cohort study

The role of prehospital endotracheal intubation (ETI) remains controversial, with significant national variability in practice. The purpose of this project was to evaluate ETI management in a system of advanced life support (ALS) providers experienced in ETI and other advanced airway techniques, and describe management and outcomes of patients with a "difficult airway." Data were collected prospectively for all ETIs performed by the fire department over a 4-year period (2001-2005), and included demographics, number of laryngoscopy attempts, airway procedures, complications, and outcomes. Of 80,501 ALS patient contacts, 4091 (5.1%) underwent attempted oral ETI, with a 96.8% success rate in four or fewer attempts. The difficult airway cohort included 130 patients (3.2%), whose airway management consisted of oral ETI after more than four attempts (46%), bag-valve-mask ventilation (33%), cricothyroidotomy (8%), retrograde ETI (5%), and digital ETI (1%). Procedural success rates ranged from 14% (digital ETI) to 91% (cricothyroidotomy). Nine patients (7%) had failed airway management, of whom 5 were found in cardiac arrest. The two most common reasons subjectively reported by ALS providers for airway difficulty were anterior trachea (39%) and small mouth (30%). Overall mortality for the difficult airway cohort was 44%. Prehospital ETI can be performed with a high success rate by experienced ALS providers, but may still require advanced airway techniques in a small subset of patients. Patient anatomy is a primary factor in failed ETI. Among the advanced procedures, cricothyroidotomy had the highest success rate and should not be delayed by other interventions.     

Managing the difficult airway: a survey of residency directors and a call for change

This study examines airway management issues in Emergency Medicine residency programs (EMRP) including; airway adjunct availability and frequency of use, number of pediatric intubations, approach to trauma airways, and teaching methods. Surveys were distributed to all accredited EM program directors, who were asked about these issues. Availability of airway adjuncts among respondents included: cricothyrotomy kits (94.9%), fiberoptic scopes (76.3%), Bougies (69.5%), LMAs (66.1%), intubating LMAs (61.0%), lighted stylets (54.2%), retrograde intubation kits (49.2%), Combitube (45.8%), and esophageal obturator airways (15.3%). Responses indicated that 93.6% of airways were orotracheal intubations. A small percentage of intubations used airway adjuncts. Programs use didactics, mannequins, cadavers, direct care and operating rooms for airway training. Emergency Physicians (EPs) are responsible for trauma airways in 89.9% of programs. Most programs have multiple airway adjuncts available, but they are rarely utilized. EPs must become proficient with airway adjuncts. EMRPs must increase resident exposure by using airway adjuncts during routine intubations.     

An Unanticipated Complication of a Novel Approach to Airway Management

Background: The King LT (King Systems Corporation, Noblesville, IN) is a rescue airway device that is gaining favor in the pre-hospital setting. Unlike other rescue airway devices, such as intubating laryngeal mask airways, the King LT does not allow for the placement of an endotracheal tube through the device. Emergency physicians who receive patients with the King LT in place will be presented with the challenge of converting to a definitive airway. Methods: We attempted a strategy that would allow for conversion from the King LT to the endotracheal tube using a gum elastic bougie. During an airway skills maintenance session utilizing non-embalmed cadavers, Emergency Medicine faculty attempted to convert a King LT to an endotracheal tube using a gum elastic bougie. Results: The technique was not successful, and in fact, resulted in an unanticipated complication. Conclusion: We cannot recommend using the gum elastic bougie as an aid to convert the King LT to an endotracheal intubation based on our experience with a non-embalmed cadaver.     

New needle cricothyroidotomy setup

We propose a simple and flexible connection setup for needle cricothyroidotomy. Needle cricothyroidotomy is a life-saving procedure. It is technically easy to perform, but it cannot provide adequate ventilation for a long period of time. The standard recommended ventilation equipment for needle cricothyroidotomy consists of a jet insuflator connected to a source of oxygen with 50 psi pressure. Such a setup is not always available in emergency situations. Alternative setups using ventilation with a bag-valve had been proposed. All of them are either too bulky or rigid, which increase the chance of cricothyroidotomy catheter dislodgment. Connection proposed by us is flexible, readily available, and easy to set up.     

A new strategy for difficult airway management with visual needle cricothyroidotomy: a manikin study

Background

Conventional needle cricothyroidotomy uses blind manipulation. We investigated the feasibility and efficiency of a new visually guided needle cricothyroidotomy technique.

Methods

A 0.9-mm microimaging fiber was delivered into a 14G needle to develop a visual puncture system. 10 inexperienced physicians were randomly assigned to perform 10 repeated needle cricothyroidotomy in each group with both conventional method and visual puncture in a manikin. Tracheal lumen puncture time and number of procedure-related complications were recorded.

Results

Under visual guidance, the needle successfully reached the tracheal lumen. The anatomy of the upper and lower airways was acquired by further advancing the microimaging fiber into the tracheal lumen of the visual group. The tracheal lumen puncture time was significantly less in the visual group than in the conventional group (3.85 ± 1.54 vs. 9.84 ± 1.08 seconds, P < .001). Damage to the posterior tracheal wall was not observed in the visual group; however, 21% of manikins in the conventional group had procedure-related complications.

Conclusions

Our results demonstrate that visual needle cricothyroidotomy is feasible, and may lead to a decrease in procedure time and procedure-related complications compared to the conventional procedure. In addition, this strategy may also provide useful information for diagnostic purposes; therefore, visual needle cricothyroidotomy may be a new strategy for the management of difficult airways in future care.     

A Randomized Trial Comparing Two Cuffed Emergency Cricothyrotomy Devices Using a Wire-Guided and a Catheter-Over-Needle Technique

Background: According to different algorithms of airway management, emergency cricothyrotomy is the final step in managing the otherwise inaccessible airway. As an alternative to an open surgical procedure, minimally invasive approaches exist. Various sets for different methods are commercially available. QuickTrach™ (VBM Medizintechnik GmbH, Sulz am Neckar, Germany) contains a plastic cannula over a metal needle for direct placement in the trachea, whereas a guide-wire is used for the actual placement of the cannula in the Melker Set™ (Cook Group Incorporated, Bloomington, IN). Objective: We hypothesize that the direct puncture involving less discrete steps is faster to perform. However, it will lead to more complications due to the higher force needed to place the relatively thick needle. Method: After approval of the local ethics committee, the study was performed on cadavers of 16 adult sheep. A wire-guided cricothyrotomy was compared with a catheter-over-needle technique. Successful placement and performance time were compared. Complication rate and maximal achieved airway pressure were evaluated. Data is given as mean and interquartile range, and Mann-Whitney U-test (p < 0.05) for significant differences. Results: With the wire-guided technique, successful placement was possible in all attempts. The catheter-over-needle method was successful in 63% and had a higher complication rate (75% vs. 13%). The cannula-over-needle method allowed a faster cricothyrotomy (32 [2–34] vs. 53 [52–56] s). Both methods allowed the delivery of similar maximal airway pressures (50 [44–51] vs. 48 [43–53] mbar). Conclusion: The wire-guided method proved to be the more reliable technique, leading to fewer complications. However, the direct puncture was faster to perform. Placed accurately, both devices allowed sufficient ventilation.     

喉罩在非常规手术麻醉应用的新进展

喉罩作为一种声门上气道工具,由于无法完全保障气道的安全,临床应用受到某些患者特殊情况、手术类型和体位的限制。气管导管一直作为这类特殊患者或者手术术中维持气道的首选方法,近年来,随着喉罩设计的改进与技术的成熟,越来越多的麻醉医生选择喉罩代替气管导管用于非常规手术,有证据显示,只要谨慎选择患者和做好术中管理同样可以保障气道安全,并且更有利于维持循环稳定和减少气道并发症。本文通过讨论喉罩在剖宫产、俯卧位、妇科腹腔镜和胸腔镜手术中应用的优缺点,为临床应用提供参考意见。     

Surgical cricothyroidotomy in trauma patients

BACKGROUND: Surgical airway intervention is occasionally necessary due to contraindicated or failed endotracheal intubation. In cricothyroidotomy patients, a choice exists between continued long-term ventilation via the cricothyroidotomy portal or conversion to tracheostomy. We examined whether conversion to tracheostomy reduces the risk of acute complications. METHODS: We retrospectively identified 46 patients with cricothyroidotomies performed at our level I trauma center over a 63-month period. We reviewed the success rate, indications, etiology, and complications. RESULTS: An airway was obtained in all cases. The most common indicator for surgical airway intervention was unsuccessful endotracheal intubation. The cause of death among nonsurvivors was not due to airway complications. Of the 15 surviving patients, 8 had conversions to tracheostomy and 7 patients did not have conversions but had decannulations. The converted group had a greater percentage of acute complications than the nonconverted group. CONCLUSION: Rate of acute complications with prolonged ventilation via cricothyroidotomy portal is equal to, if not lower than, via converted tracheostomy. Cricothyroidotomy in trauma patients may be used long term without any increase in acute complications.     

四种外科气道技术的对比研究

目的：对比环甲膜穿刺反向引导气管切开术（ cricothyroid membrane puncture guided tracheostomy, CMPGT ）、气管切开术（ surgical tracheostomy, ST ）、环甲膜切开术（ surgical cricothyroidotomy, SC）和Griggs经皮导丝扩张钳气管造口术（ guide wire dilating forceps, GWDF）四种技术建立紧急气道的时间、效果和并发症。方法将20只小型猪随机（随机数字法）分为四组,麻醉后气管插管,通过阻塞插管使其血氧饱和度（ SpO2）降至80％。应用上述四种方法建立紧急气道,记录手术时间,监测并记录血氧饱和度等心电监护仪及动脉血气指标,记录术中及术后并发症并根据并发症评分表评分。结果所有小型猪均成功建立气道, SC、 GWDF、 CMPGT和ST的手术时间分别为（86±12） s,（165±63） s,（174±34） s和（519±128） s,但是CMPGT组的恢复通气时间最短,为（23±4） s , P＜0.01。心电图显示停止供氧后T波降低和Q-T间期缩短, SpO2下降,通气后快速恢复正常水平。四组心电图和动脉血氧指标的术前和术后差异有统计学意义（ P＜0.05）。并发症方面,每组均有两只出现轻度出血。 ST组另有3只术中中度出血,3只出现低血压,1只术后轻度出血,并导致了创口周围感染。 SC组中,1只可见术中中度出血,1只有轻微的环状软骨损伤。通过纤维支气管镜发现 GWDF 组中1只小型猪有中度的气管内壁损伤。CMPGT、 GWDF、 SC和ST四组的并发症评分为3、5、9、19。结论动物实验证实相比ST、 SC和GWDF, CMPGT在建立紧急气道方面更具有时效性和安全性。     

The technique of tracheotomy and cricothyroidotomy. When to operate--and how to manage complications

Tracheotomy can relieve upper airway obstruction, improve pulmonary hygiene, and support long-term mechanical ventilation. Consider performing a tracheotomy whenever the need for more than 14 days of ventilatory support is anticipated. When emergent airway access is needed and translaryngeal intubation is not possible, consider cricothyroidotomy. For a tracheotomy, make a transverse incision 1 cm above the suprasternal notch or, for cricothyroidotomy, through the superficial cricothyroid membrane. Accidental tube displacement within 5 days of surgery is potentially tracheotomy's most lethal early complication. Many late complications can be prevented by careful management and expert nursing support.     

Difficulties with portable suction equipment used for prehospital advanced airway procedures

Introduction. Airway management is the highest priority for prehospital personnel. While different modalities for airway management are under investigation, endotracheal intubation remains the standard for definitive airway protection. Currently, airway adjuncts such as portable suction remain relatively unstudied.

Objective. To identify utilization and complications associated with portable suction equipment used by prehospital medical personnel.

Methods. Fifty-one paramedics serving a Level I urban trauma center were anonymously surveyed to determine types of equipment used, maintenance and utilization patterns, difficulties encountered, and training received with that equipment.

Results. The paramedics reported carrying suction equipment to the scene of medical aid calls less than 25% of the time. Once on scene, suction equipment is utilized during 50% of advanced airway procedures. Half of the paramedics reported complications affecting patient care at least once during their careers due to equipment malfunction. Ninety-eight percent of the paramedics reported having some type of training with the suction equipment for prehospital advanced airway procedures.

Conclusions. The results of this study suggest that suction equipment is carried to the scene infrequently and, when employed, is often found to be functioning suboptimally. Suggestions for improvement and further investigation are provided.     

Emergency skill training--a randomized controlled study on the effectiveness of the 4-stage approach compared to traditional clinical teaching

Introduction

The “4-stage approach” has been widely accepted for practical skill training replacing the traditional 2 stages (“see one, do one”). However, the superior effectiveness of the 4-stage approach was never proved.

Objectives

To evaluate whether skill training with the 4-stage approach results in shorter performance time needed for a successful percutaneous needle-puncture cricothyroidotomy, and consequently in a reduced number of attempts needed to perform the skill in <60 s compared to traditional teaching.

Trial design

Randomized controlled single-blinded parallel group study at the University Hospital Bern.

Methods

With IRB approval and informed consent 128 undergraduate medical students were randomized in four groups: traditional teaching, no stage 2, no stage 3, and 4-stage approach for the training of cricothyroidotomy. Everyone watched a video of the cricothyroidotomy as stage 1 followed by skill training in the respective teaching group. Participants had to perform the cricothyroidotomy 10 times on skin-covered pig larynxes. Performance time was measured from skin palpation to trachea ventilation. Study participants filled out a self-rating on competency during the training.

Results

Performance time for each attempt was comparable in all groups and improved similarly to reach a performance time of <60 s. Self-rating revealed that all groups felt equally competent throughout.

Conclusions

Even if the 4-stage approach is widely accepted and used as a didactic method for skill teaching we could not find evidence that its use or omitting stage 2 or 3 results in superior learning of an emergency skill compared to traditional teaching.     

Using ultrasound to teach anatomy in the undergraduate medical curriculum: an evaluation of the experiences of tutors and medical students

This paper describes the experiences of staff and students at two UK medical schools, who introduced portable ultrasound (PU) as an imaging technology to deliver clinical anatomy teaching and to aid skill development in interpretation of cross-sectional anatomy (CSA). A sonographer contributed to curriculum design and teaching, but mostly anatomy tutors delivered the teaching. This case study method evaluates staff and student perspectives on the ultrasound-based anatomy teaching. Quantitative data and qualitative data were collected and analysed. Staff were positive about the experience. They described their expectations for students and solutions for practical issues regarding the teaching, but were concerned about their competency in scanning and wanted bespoke training for sonoanatomy teaching. Curriculum development was accelerated through engagement with a sonographer and an ultrasound champion. Students were extremely positive about their experience; they valued the expertise of a sonographer who taught more challenging sonoanatomy, but were equally positive regarding teaching sessions led by well-trained anatomy tutors who taught more simple sonoanatomy. Students affirmed most tutors’ expectations that ultrasound could reinforce existing anatomical knowledge, added clinical contextualisation, but not that use of ultrasound (US) assisted in interpreting CSA. Students valued the introduction to the technology and found sonoimage interpretation challenging, but not insurmountable. Students wanted more instruction on ultrasound physics, an expansion of ultrasound curriculum, with smaller groups and opportunities to scan volunteers. These data support the case for the use of PU to deliver anatomy teaching and to prime medical students for later clinical encounters with PU.     

The influence of hemorrhagic shock on ventilation through needle cricothyroidotomy in pigs

Background

The aim of this study was to examine the effects of controlled hemorrhage and shock on oxygenation and ventilation using needle cricothyroidotomy and jet ventilation in an animal model.

Methods

Twenty-four male pigs were randomly allocated into 4 groups: SHOCK (animals in hemorrhagic shock only), CRICH (animals that underwent needle cricothyroidotomy only), SHOCK+CRICH (animals in hemorrhagic shock + needle cricothyroidotomy), and SHAM (anesthetized animals submitted to surgical preparation only). All animals were surgically prepared and were observed for a period of 40 minutes (T0 − T40). Hemodynamic and blood gas variables were compared using analysis of variance and Bonferroni post hoc testing at a level of significance of 95%.

Results

CRICH and SHOCK+CRICH developed respiratory acidosis, with a progressive decrease of arterial pH after T20, and they presented a significant increase of PaCO₂ levels after T10, when compared with SHAM and SHOCK (P < .001). When SHOCK+CRICH was compared with CRICH, it presented a larger increase of PaCO₂ after T10 (P = .036) and an even more significant increase after T20 (P = .009).

Conclusion

Hemorrhagic shock anticipated and intensified the retention of carbon dioxide and respiratory acidosis during manual jet ventilation through needle cricothyroidotomy in comparison with animals with jet ventilation but without shock. The results found in this work should be considered in future protocols for the assistance of victims of trauma in prehospital settings.     

Prehospital Standardization of Medical Airway Management: Incidence and Risk Factors of Difficult Airway

Objectives: The rate of difficult intubation in prehospital emergency medicine varies greatly among studies already published and depends on several factors. The authors' objective was to determine the rate of difficult intubations and to determine factors associated with prehospital difficult airways when a standard protocol for sedation and intubation was applied. Methods: This 30‐month clinical, observational, prospective study was performed in a suburb of Paris, France (Val de Marne, population 1,300,000) by a prehospital emergency medical unit. Airway management for patients who needed tracheal intubation was standardized. The pharmacological procedure recommended rapid sequence intubation for patients with spontaneous cardiac activity. In cases of difficult, laryngoscopy‐assisted intubation, a predefined algorithm was proposed. The Intubation Difficulty Score (IDS) was calculated for all patients requiring tracheal intubation, and factors associated with difficult intubation, defined by IDS of >5, were identified by using multivariate statistical analysis. Results: During the study period, 1,442 patients were included; 640 (44%) were in cardiorespiratory arrest, and 802 had a spontaneous cardiac activity. Deviation from the pharmacological and airway management procedures occurred in 1% of cases. When the predefined difficult airway management algorithm was followed, failure to intubate was encountered twice (0.1%). One hundred six (7.4%) patients had an IDS of >5, and 60 (4.1%) required first (n= 56) then second (n= 4) alternative techniques for tracheal intubation. Semirigid leaders allowed tracheal access in 93% of difficult‐intubation patients. One patient required a prehospital cricothyroidotomy. Factors associated with difficult intubation were the following: a history of ear, nose, or throat neoplasia or surgery; obesity; facial trauma; the operator's status; and the operator's position. Conclusions: If prehospital medical airway management is standardized and performed by trained operators, failure to intubate is rare (0.1%), and the incidence of difficult tracheal intubation is 7.4%, independent of cardiorespiratory status.     

Alternative ventilation strategies in cardiopulmonary resuscitation

The introduction of the 2000 Guidelines for Cardiopulmonary Resuscitation emphasizes a new, evidence-based approach to the science of ventilation during cardiopulmonary resuscitation (CPR). New laboratory and clinical science underemphasizes the role of ventilation immediately after a dysrhythmic cardiac arrest (arrest primarily resulting from a cardiovascular event, such as ventricular defibrillation or asystole). However, the classic airway patency, breathing, and circulation (ABC) CPR sequence remains a fundamental factor for the immediate survival and neurologic outcome of patients after asphyxial cardiac arrest (cardiac arrest primarily resulting from respiratory arrest). The hidden danger of ventilation of the unprotected airway during cardiac arrest either by mouth-to-mouth or by mask can be minimized by applying ventilation techniques that decrease stomach gas insufflation. This goal can be achieved by decreasing peak inspiratory flow rate, increasing inspiratory time, and decreasing tidal volume to approximately 5 to 7 mL/kg, if oxygen is available. Laboratory and clinical evidence recently supported the important role of alternative airway devices to mask ventilation and endotracheal intubation in the chain of survival. In particular, the laryngeal mask airway and esophageal Combitube proved to be effective alternatives in providing oxygenation and ventilation to the patient in cardiac arrest in the prehospital arena in North America. Prompt recognition of supraglottic obstruction of the airway is fundamental for the management of patients in cardiac arrest when ventilation and oxygenation cannot be provided by conventional methods. "Minimally invasive" cricothyroidotomy devices are now available for the professional health care provider who is not proficient or comfortable with performing an emergency surgical tracheotomy or cricothyroidotomy. Finally, a recent device that affects the relative influence of positive pressure ventilation on the hemodynamics during cardiac arrest has been introduced, the inspiratory impedance threshold valve, with the goal of maximizing coronary and cerebral perfusion while performing CPR. Although the role of this alternative ventilatory methodology in CPR is rapidly being established, we cannot overemphasize the need for proper training to minimize complications and maximize the efficacy of these new devices.