A comparison of the forces exerted during laryngoscopy using disposable and non-disposable laryngoscope blades

Single-use versus reusable metallic laryngoscopes for non-emergent intubation: A retrospective review of 72,672 intubations

STUDY OBJECTIVE

Increased regulatory requirements for sterilization in recent years have prompted a widespread transition from reusable to single-use laryngoscopes. The purpose of this study was to determine if the transition from metallic reusable to metallic single-use laryngoscopes impacted the performance of direct laryngoscopy at an academic medical center.

DESIGN

Single-site retrospective cohort study.

SETTING

General anesthetic cases requiring tracheal intubation.

PATIENTS

Adult patients undergoing non-emergent procedures.

INTERVENTIONS

Data were collected two years before and two years after a transition from metallic reusable to metallic single-use laryngoscopes.

MEASUREMENTS

The primary outcome was need for intubation rescue with an alternate device. Secondary outcomes were difficult laryngeal view (modified Cormack-Lehane grade ≥ 2b) and hypoxemia (SpO2 < 90% for >30 s) during direct laryngoscopy intubations. Subgroup analyses for rapid sequence induction, Macintosh blades, Miller blades, and patients with difficult airway risk factors (Obstructive Sleep Apnea, Mallampati ≥3, Body Mass Index >30 kg/m2) were performed.

MAIN RESULTS

In total, 72,672 patients were included: 35,549 (48.9%) in the reusable laryngoscope cohort and 37,123 (51.1%) in the single-use laryngoscope cohort. Compared with reusable laryngoscopes, single-use laryngoscopes were associated with fewer rescue intubations with an alternate device (covariates-adjusted odds ratio [OR] 0.81 95% CI 0.66-0.99). Single-use laryngoscopes were also associated with lower odds of difficult laryngeal view (OR 0.86; 95% CI 0.80-0.93). Single use laryngoscopes were not associated with hypoxemia during the intubation attempt (OR 1.03; 95% CI 0.88-1.20). Similar results were observed for subgroup analyses including rapid sequence induction, Macintosh blades, Miller blades, and patients with difficult airway risk factors.

CONCLUSIONS

Metallic single-use laryngoscopes were associated with less need for rescue intubation with alternate devices and lower incidence of poor laryngeal view compared to reusable metallic laryngoscopes.

Hemodynamic response related to the Airway Scope versus the Macintosh laryngoscope: A systematic review and meta-analysis with trial sequential analysis

BACKGROUND

It is important to reduce the hemodynamic response during tracheal intubation. We performed a systematic review and meta-analysis of the Airway Scope and Macintosh laryngoscope to determine whether they reduce the hemodynamic responses of heart rate (HR) and mean blood pressure (MBP) after tracheal intubation under general anesthesia.

METHODS

We performed a comprehensive literature search of electronic databases for clinical trials comparing hemodynamic response to tracheal intubation. The primary aim of our meta-analyst is to determine if the Airway Scope reduces hemodynamic responses (HR and mean MBP) 60 seconds after tracheal intubation compared to the Macintosh laryngoscope. We expressed pooled differences in hemodynamic responses between the 2 devices as weighted mean differences with 95% confidence intervals. We conducted trial sequential analysis. Secondarily, we investigated the ability of the Airway Scope and Macintosh laryngoscope to reduce hemodynamic responses at 120 seconds, 180 seconds, and 300 seconds after tracheal intubation.

RESULTS

We identified clinical trials comparing hemodynamic response via a comprehensive literature search. Of 185 articles found in the search, we selected 8. In comparison to the Macintosh laryngoscope, the Airway Scope significantly reduced HR and MBP at 60 seconds after tracheal intubation (HR; weighted mean difference = -7.29; 95% confidence interval, -10.9 to -3.62; P < .0001; I2 = 57%, MBP; weighted mean difference = -11.5; 95% confidence interval, -20.4 to -2.65; P = .01; I2 = 91%). At the secondary outcome, the Airway Scope significantly reduced the fluctuation of HR after 120 seconds and 180 seconds of tracheal intubation. However, the Airway Scope did not significantly reduce MBP 120 seconds, 180 seconds, and 300 seconds after tracheal intubation. Trial sequential analysis suggested that the total sample size reached the required information size for heart rate.

CONCLUSIONS

Our finding suggested that the Airway Scope attenuated hemodynamic responses at 60 seconds after tracheal intubation in comparison with that of the Macintosh laryngoscope. However, the MBP sample size is small and further research is needed.

Comparison of the strength of various disposable videolaryngoscope blades

PURPOSE

Breaking of disposable blades during emergency endotracheal intubation has been reported. Breakage can cause serious injury and foreign body ingestion. We aimed to measure and analyze the strength characteristics of different disposable videolaryngoscope blades with the application of an upward-lifting force.

METHODS

We measured the strength of four disposable videolaryngoscope blades (C-Mac® S Video laryngoscope MAC #3, Glidescope GVL® 3 stat, Pentax AWS® PBlade TL type, and King Vision® aBlade #3) using the fracture test. The strength of 12 samples of each type of disposable videolaryngoscope blade was measured using an Instron 5,966 tensile tester by applying an upward-lifting force.

RESULTS

After the fracture test using C-Mac, Glidescope GVL, Pentax AWS, and King Vision, the number of deformed blades were 0, 12, 3, and 7, respectively, and the number of broken blades were 12, 0, 9, and 5, respectively. The mean (standard deviation) maximum force strengths of Pentax AWS, C-Mac, King Vision, and Glidescope GVL blades were 408.4 (27.4) N, 325.8 (26.5) N, 291.8 (39.3) N, and 262.7 (3.8) N, respectively (P < 0.001).

CONCLUSION

Clinicians should be aware of the varied strength characteristics of the four types of disposable videolaryngoscope blades when they are used in endotracheal intubation.

Use of the GlideScope does not lower the hemodynamic response to tracheal intubation more than the Macintosh laryngoscope: a systematic review and meta-analysis

BACKGROUND

It is presently unclear whether the hemodynamic response to intubation is less marked with indirect laryngoscopy using the GlideScope (GlideScope) than with direct laryngoscopy using the Macintosh laryngoscope. Thus, the aim of this study was to determine whether using the GlideScope lowers the hemodynamic response to tracheal intubation more than using the Macintosh laryngoscope.

METHODS

We performed a comprehensive literature search of electronic databases for clinical trials comparing hemodynamic response to tracheal intubation. The primary aim was to determine whether the heart rate (HR) and mean blood pressure (MBP) 60 s after tracheal intubation with the GlideScope were lower than after intubation with the Macintosh laryngoscope. We expressed pooled differences in HR and MBP between the devices as the weighted mean difference with 95% confidence interval and also performed trial sequential analysis (TSA). Second, we examined whether use of the GlideScope resulted in lower post-intubation hemodynamic responses at 120, 180, and 300 s compared with use of the Macintosh laryngoscope. For sensitivity analysis, we used a multivariate random effects model that accounted for within-study correlation of the longitudinal data.

RESULTS

The literature search identified 13 articles. HR and MBP at 60 seconds post-intubation was not significantly lower with the GlideScope than with the Macintosh (HR vs MBP: weighted mean difference = 0.22 vs 2.56; 95% confidence interval -3.43 to 3.88 vs -0.82 to 5.93; P = .90 vs 0.14; I = 77% vs 63%: Cochran Q, 52.7 vs 27.2). Use of the GlideScope was not associated with a significantly lower HR or MBP at 120, 180, or 300 s post-intubation. TSA indicated that the total sample size was over the futility boundary for HR and MBP. Sensitivity analysis indicated no significant association between use of the GlideScope and a lower HR or MBP at any measurement point.

CONCLUSIONS

Compared with the Macintosh laryngoscope, the GlideScope did not lower the hemodynamic response after tracheal intubation. Sensitivity analysis results supported this finding, and the results of TSA suggest that the total sample size exceeded the TSA monitoring boundary for HR and MBP.

Lower maximum forces on oral structures when using gum-elastic bougie than when using endotracheal tube and stylet during both direct and indirect laryngoscopy by novices: a crossover study using a high-fidelity simulator

BACKGROUND

Applying excessive force during endotracheal intubation (ETI) is associated with several complications, including dental trauma and hemodynamic alterations. A gum-elastic bougie (GEB), a type of tracheal tube introducer, is a useful airway adjunct for patients with poor laryngoscopic views. However, how the use of a GEB affects the force applied during laryngoscopy is unclear. We compared the force applied on the oral structures during ETI performed by novices using the GEB versus an endotracheal tube + stylet.

METHODS

This prospective crossover study was conducted from April 2017 to March 2019 in a public medical university in Japan. In total, 209 medical students (4th and 5th grade, mean age of 23.7 ± 2.0 years) without clinical ETI experience were recruited. The participants used either a Macintosh direct laryngoscope (DL) or C-MAC video laryngoscope (VL) in combination with a GEB or stylet to perform ETI on a high-fidelity airway management simulator. The order of the first ETI method was randomized to minimize the learning curve effect. The outcomes of interest were the maximum forces applied on the maxillary incisors and tongue during laryngoscopy. The implanted sensors in the simulator quantified these forces automatically.

RESULTS

The maximum force applied on the maxillary incisors was significantly lower when using a GEB than when using an endotracheal tube + stylet both with the Macintosh DL (39.0 ± 23.3 vs. 47.4 ± 32.6 N, P < 0.001) and C-MAC VL (38.9 ± 18.6 vs. 42.0 ± 22.1 N, P < 0.001). Similarly, the force applied on the tongue was significantly lower when using a GEB than when using an endotracheal tube + stylet both with the Macintosh DL (31.9 ± 20.8 vs. 37.8 ± 22.2 N, P < 0.001) and C-MAC VL (35.2 ± 17.5 vs. 38.4 ± 17.5 N, P < 0.001).

CONCLUSIONS

Compared with the use of an endotracheal tube + stylet, the use of a GEB was associated with lower maximum forces on the oral structures during both direct and indirect laryngoscopy performed by novices. Our results suggest the expanded role of a GEB beyond an airway adjunct for difficult airways.

Airtraq® reduces the hemodynamic response to tracheal intubation using single-lumen tubes in adults compared with the Macintosh laryngoscope: A systematic review and meta-analysis of randomized control trials

STUDY OBJECTIVE

To investigate whether Airtraq® attenuate the hemodynamic responses to tracheal intubation using single-lumen tubes in adults as compared with the Macintosh laryngoscope.

DESIGN

Meta-analysis.

SETTING

Operating room.

MEASUREMENTS

The primary outcome of this meta-analysis was to determine whether laryngoscopy using the Airtraq® reduced hemodynamic responses-heart rate (HR) and mean blood pressure (MBP)-at 60 s (s) after tracheal intubation compared to laryngoscopy with the Macintosh laryngoscope. Pooled differences in these hemodynamic responses between the two devices were expressed as weighted mean difference with 95% confidence intervals. We then conducted trial sequential analysis (TSA). The secondary outcome was to investigate whether the Airtraq® reduce the hemodynamic response at 120 s, 180 s, and 300 s after tracheal intubation compared to the Macintosh laryngoscope. We also conducted sensitivity analysis of the hemodynamic responses to tracheal intubation with the laryngoscopes using a multivariate random effects model accounting for within-study correlation of the longitudinal data.

MAIN RESULTS

From electronic databases, we selected 11 randomized controlled trials for studies that enrolled subjects satisfying our inclusion criteria. Compared with the Macintosh laryngoscope, the Airtraq® significantly reduced both HR and MBP at 60 s after tracheal intubation. In secondary outcome, the Airtraq® significantly reduced both HR and MBP at all measurement points, excluding HR at 300 s after tracheal intubation. TSA showed that total sample size reached the required information size for both HR and MBP. The sensitivity analysis revealed that the Airtraq® reduced both HR and MBP at all measurement points, excluding HR at 300 s after tracheal intubation.

CONCLUSIONS

The Airtraq® attenuates the hemodynamic response at 60 s after tracheal intubation compared with the Macintosh laryngoscope. (GRADE: Low) These results were supported by the sensitivity analysis. TSA suggested that the total sample size was exceeded TSA monitoring boundary both HR and MBP.

Life Cycle Assessment and Costing Methods for Device Procurement: Comparing Reusable and Single-Use Disposable Laryngoscopes

BACKGROUND

Traditional medical device procurement criteria include efficacy and safety, ease of use and handling, and procurement costs. However, little information is available about life cycle environmental impacts of the production, use, and disposal of medical devices, or about costs incurred after purchase. Reusable and disposable laryngoscopes are of current interest to anesthesiologists. Facing mounting pressure to quickly meet or exceed conflicting infection prevention guidelines and oversight body recommendations, many institutions may be electively switching to single-use disposable (SUD) rigid laryngoscopes or overcleaning reusables, potentially increasing both costs and waste generation. This study provides quantitative comparisons of environmental impacts and total cost of ownership among laryngoscope options, which can aid procurement decision making to benefit facilities and public health.

METHODS

We describe cradle-to-grave life cycle assessment (LCA) and life cycle costing (LCC) methods and apply these to reusable and SUD metal and plastic laryngoscope handles and tongue blade alternatives at Yale-New Haven Hospital (YNHH). The US Environmental Protection Agency's Tool for the Reduction and Assessment of Chemical and other environmental Impacts (TRACI) life cycle impact assessment method was used to model environmental impacts of greenhouse gases and other pollutant emissions.

RESULTS

The SUD plastic handle generates an estimated 16-18 times more life cycle carbon dioxide equivalents (CO2-eq) than traditional low-level disinfection of the reusable steel handle. The SUD plastic tongue blade generates an estimated 5-6 times more CO2-eq than the reusable steel blade treated with high-level disinfection. SUD metal components generated much higher emissions than all alternatives. Both the SUD handle and SUD blade increased life cycle costs compared to the various reusable cleaning scenarios at YNHH. When extrapolated over 1 year (60,000 intubations), estimated costs increased between $495,000 and $604,000 for SUD handles and between $180,000 and $265,000 for SUD blades, compared to reusables, depending on cleaning scenario and assuming 4000 (rated) uses. Considering device attrition, reusable handles would be more economical than SUDs if they last through 4-5 uses, and reusable blades 5-7 uses, before loss.

CONCLUSIONS

LCA and LCC are feasible methods to ease interpretation of environmental impacts and facility costs when weighing device procurement options. While management practices vary between institutions, all standard methods of cleaning were evaluated and sensitivity analyses performed so that results are widely applicable. For YNHH, the reusable options presented a considerable cost advantage, in addition to offering a better option environmentally. Avoiding overcleaning reusable laryngoscope handles and blades is desirable from an environmental perspective. Costs may vary between facilities, and LCC methodology demonstrates the importance of time-motion labor analysis when comparing reusable and disposable device options.

Mechanical strain to maxillary incisors during direct laryngoscopy

Background

While most Direct laryngoscopy leads to dental injury in 25–39% of cases. Dental injury occurs when the forces and impacts applied to the teeth exceed the ability of the structures to dissipate energy and stress. The purpose of this study was to measure strain, (which is the change produced in the length of the tooth by a force applied to the tooth) strain rate, and strain-time integral to the maxillary incisors and determine if they varied by experience, type of blade, or use of an alcohol protective pad (APP).

Methods

A mannequin head designed to teach and test intubation was instrumented with eight single axis strain gauges placed on the four maxillary incisors: four on the facial or front surface of the incisors and four on the lingual or back, near the insertion of the incisor in the gums to measure bending strain as well as compression. Anesthesiology faculty, residents, and certified registered nurse anesthetists intubated with Macintosh and Miller blades with and without APP. Using strain-time curves, the maximum strain, strain rate, and strain time integral were calculated.

Results

Across the 92 subjects, strain varied 8–12 fold between the 25th and 75th percentiles for all four techniques, but little by experience, while strain rate and strain integral varied 6–13 fold and 15–26 fold, respectively, for the same percentiles. Intubators who had high strain values with one blade tended to have high strains with the other blade with and without the APP (all pairwise correlation rho = 0.42–0.63).

Conclusions

Strain varies widely by intubator and that the use of the APP reduces strain rate which may decrease the risk of or the severity of dental injury.

Airtraq(®) versus Macintosh laryngoscope: A comparative study in tracheal intubation

Background:

The curved laryngoscope blade described by Macintosh in 1943 remains the most widely used device to facilitate tracheal intubation. The Airtraq^® (Prodol Meditec S.A, Vizcaya, Spain) is a new, single use, indirect laryngoscope introduced into clinical practice in 2005. It has wan exaggerated blade curvature with internal arrangement of optical lenses and a mechanism to prevent fogging of the distal lens. A high quality view of the glottis is provided without the need to align the oral, pharyngeal and tracheal axis. We evaluated Airtraq and Macintosh laryngoscopes for success rate of tracheal intubation, overall duration of successful intubation, optimization maneuvers, POGO (percentage of glottic opening) score, and ease of intubation.

Materials and Methods:

Patients were randomly allocated by computer-generated random table to one of the two groups, comprising 40 patients each, group I (Airtraq) and group II (Macintosh). After induction of general anesthesia, tracheal intubation was attempted with the Airtraq or the Macintosh laryngoscope as per group. Primary end points were overall success rate of tracheal intubation, overall duration of successful tracheal intubation, optimization maneuvers, POGO score and ease of intubation between the two groups.

Results:

We observed that Airtraq was better than the Macintosh laryngoscope as duration of successful intubation was shorter in Airtraq 18.15 seconds (±2.74) and in the Macintosh laryngoscope it was 32.72 seconds (±8.31) P < 0.001. POGO was also better in the Airtraq group 100% grade 1 versus 67.5% in the Macintosh group, P < 0.001. Ease of intubation was also better in the Airtraq group. It was easy in 97.5% versus 42.5% in the Macintosh group, P < 0.001.

Conclusion:

Both Airtraq and Macintosh laryngoscopes are equally effective in tracheal intubation in normal airways. Duration of successful tracheal intubation was shorter in the Airtraq group which was statistically significant.

Comparison of hemodynamic response to tracheal intubation with Macintosh and McCoy laryngoscopes

BACKGROUND

Use of McCoy blade laryngoscope avoids the lifting force in the vallecula and theoretically should lead to a lower hemodynamic response related to laryngoscopy and tracheal intubation. The available literature on the topic is conflicting.

MATERIALS AND METHODS

We studied the hemodynamic response to laryngoscopy and tracheal intubation in 60 ASA 1 AND 2 adult patients using either Macintosh or McCoy laryngoscopes. The change in systolic, diastolic, mean arterial pressure, and heart rate (HR) was observed for 10 min post intubation. Arrhythmias and ST changes were also observed.

RESULTS

The maximum change in HR was 18.7% in the Macintosh and 7.7% in the McCoy group, and in systolic arterial pressure was 22.9% in the Macintosh and 10.3% in the McCoy group. This difference between groups was significant (P < 0.0001). The change lasted for a lesser duration in the McCoy group. No arrhythmias or ST changes were observed in either group.

CONCLUSION

Hemodynamic changes with use of McCoy laryngoscope were lesser in magnitude and of shorter duration.

A medical hand tool physical interaction evaluation approach for prototype testing using patient care simulators

The purpose of this study was to develop and test a physical ergonomics assessment approach for medical device handles. The method assesses wrist posture and force of exertion simultaneously by task element. Electrogoniometers and EMG sensors were connected through a data acquisition module for synchronization with video recordings of trials. Task analysis of video recordings were performed offline with Observer XT software. Average posture and force data across several repetitions of individual task elements were calculated and presented in a format suitable for informing product designers of specific issues during a test trial. A handle comfort questionnaire is proposed to survey subjective responses. The evaluation approach was applied to an endoscope needle in sampling a biopsy from the stomach wall using a gastrointestinal track simulator with ten physician surrogates. The results showed that for all task elements the wrist was in extension (33(°)-45(°)). Peak muscle forces ranged from 28% to 68% MVC across the three muscles studied. Muscle peak forces were above ACGIH HAL maximum threshold limits for four of the seven task elements, and above the action limit for all seven task elements for two muscles. The handle comfort questionnaire data also supported the high muscle force findings, and also on force distribution on the handle due to contact stresses. This combined approach could be used to collect and report detailed early stage ergonomics data from user trials on patient care simulators. The approach is proposed for use by medical device designers at the design stage of new products using prototypes, but it could also be used on existing products with real patients.

Measurement of forces applied during Macintosh direct laryngoscopy compared with GlideScope® videolaryngoscopy

Laryngoscopy can induce stress responses that may be harmful in susceptible patients. We directly measured the force applied to the base of the tongue as a surrogate for the stress response. Force measurements were obtained using three FlexiForce Sensors(®) (Tekscan Inc, Boston, MA, USA) attached along the concave surface of each laryngoscope blade. Twenty-four 24 adult patients of ASA physical status 1-2 were studied. After induction of anaesthesia and neuromuscular blockade, laryngoscopy and tracheal intubation was performed using either a Macintosh or a GlideScope(®) (Verathon, Bothell, WA, USA) laryngoscope. Complete data were available for 23 patients. Compared with the Macintosh, we observed lower median (IQR [range]) peak force (9 (5-13 [3-25]) N vs 20 (14-28 [4-41]) N; p = 0.0001), average force (5 (3-7 [2-19]) N vs 11 (6-16 [1-24]) N; p = 0.0003) and impulse force (98 (42-151 [26-444]) Ns vs 150 (93-207 [17-509]) Ns; p = 0.017) with the GlideScope. Our study shows that the peak lifting force on the base of the tongue during laryngoscopy is less with the GlideScope videolaryngoscope compared with the Macintosh laryngoscope.

A Comparison of the Forces Applied to a Manikin during Laryngoscopy with the Glidescope® and Macintosh Laryngoscopes

The force applied during laryngoscopy can cause local tissue trauma and can induce cardiovascular responses and cervical spine movement in susceptible patients. Previous studies have identified numerous operator and patient factors that influence the amount of force applied during intubation. There are few studies evaluating the effect of different laryngoscope blades and no study involving video laryngoscopes. In this study we measured the forces using two laryngoscopic techniques. Three FlexiForce Sensors® (A201-25, Tekscan, Boston, MA, USA) were attached to the concave blade surface of a Macintosh and a GlideScope® laryngoscope. Experienced anaesthetists performed Macintosh and GlideScope intubations on the Laerdal® Airway Management Trainer manikin. Compared to Macintosh intubations, the GlideScope intubations had equal or superior views of the glottis with 55%, 58% and 66% lower median peak, average and impulse forces applied to the tongue base. The distal sensor registered the most force in both devices and the force distribution pattern was similar between the devices. The findings suggest that the GlideScope requires less force for similar or better laryngoscopic views, at least in a manikin model.

Force and pressure distribution using Macintosh and GlideScope laryngoscopes in normal and difficult airways: a manikin study

BACKGROUND

The forces applied to the soft tissues of the upper airway may have a deleterious effect. This study was designed to evaluate the performance of the GlideScope compared with the Macintosh laryngoscope.

METHODS

Twenty anaesthetists and 20 trainees attempted tracheal intubation of a Laerdal SimMan manikin. Forces and pressure distribution applied by both laryngoscope blades onto the soft upper airway tissues were measured using film pressure transducers. The minimal force needed to achieve a successful intubation, in the same simulated scenario, was measured; additionally, we considered the visualization score achieved by using the Cormack-Lehane grades.

RESULTS

All participants applied, on average, lower force with the GlideScope than with the Macintosh in each simulated scenario. Forces [mean (sd)] applied in the normal airway scenario [anaesthetists: Macintosh 39 (22) N and GlideScope 27 (15) N; trainees: Macintosh 45 (24) N and GlideScope 21 (15) N] were lower than forces applied in the difficult airway scenario [anaesthetists: Macintosh 95 (22) N and GlideScope 66 (20) N; trainees: Macintosh 100 (38) N and GlideScope 48 (16) N]. All the intubations using the GlideScope were successful, regardless of the scenario and previous intubation experience. The average pressure on the blades was 0.13 MPa for the Macintosh and 0.07 MPa for the GlideScope, showing a higher uniformity for the latter.

CONCLUSIONS

The GlideScope allowed the participants to obtain a successful intubation applying a lower force. A flatter and more uniform pressure distribution, a higher successful rate, and a better glottic view were observed with the GlideScope.

Equipment to manage a difficult airway during anaesthesia

Airway complications are a leading cause of morbidity and mortality in anaesthesia. Effective management of a difficult airway requires the timely availability of suitable airway equipment. The Australian and New Zealand College of Anaesthetists has recently developed guidelines for the minimum set of equipment needed for the effective management of an unexpected difficult airway (TG4 [2010] www.anzca.edu.au/resources/professionaldocuments). TG4 [2010] is based on expert consensus, underpinned by wide consultation and an extensive review of the available evidence, which is summarised in a Background Paper (TG4 BP [2010] www.anzca.edu.au/ resources/professional-documents). TG4 [2010] will be reviewed at the end of one year and thereafter every five years or more frequently if necessary. The current paper is reproduced directly from the Background Paper (TG4 BP [2010]).

Out-of-hospital tracheal intubation with single-use versus reusable metal laryngoscope blades: a multicenter randomized controlled trial

STUDY OBJECTIVE

Emergency tracheal intubation is reported to be more difficult with single-use plastic than with reusable metal laryngoscope blades in both inhospital and out-of-hospital settings. Single-use metal blades have been developed but have not been compared with conventional metal blades. This controlled trial compares the efficacy and safety of single-use metal blades with reusable metal blades in out-of-hospital emergency tracheal intubation.

METHODS

This randomized controlled trial was carried out in France with out-of-hospital emergency medical units (Services de Médecine d'Urgence et de Réanimation). This was a multicenter prospective noninferiority randomized controlled trial in adult out-of-hospital patients requiring emergency tracheal intubation. Patients were randomly assigned to either single-use or reusable metal laryngoscope blades and intubated by a senior physician or a nurse anesthetist. The primary outcome was first-pass intubation success. Secondary outcomes were incidence of difficult intubation, need for alternate airway devices, and early intubation-related complications (esophageal intubation, mainstem intubation, vomiting, pulmonary aspiration, dental trauma, bronchospasm or laryngospasm, ventricular tachycardia, arterial desaturation, hypotension, or cardiac arrest).

RESULTS

The study included 817 patients, including 409 intubated with single-use blades and 408 with a reusable blade. First-pass intubation success was similar in both groups: 292 (71.4%) for single-use blades, 290 (71.1%) for reusable blades. The 95% confidence interval (CI) for the difference in treatments (0.3%; 95% CI -5.9% to 6.5%) did not include the prespecified inferiority margin of -7%. There was no difference in rate of difficult intubation (difference 3%; 95% CI -7% to 2%), need for alternate airway (difference 4%; 95% CI -8% to 1%), or early complication rate (difference 3%; 95% CI -3% to 8%).

CONCLUSION

First-pass out-of-hospital tracheal intubation success with single-use metal laryngoscopy blades was noninferior to first-pass success with reusable metal laryngoscope blades.

Static forces variation and pressure distribution in laryngoscopy performed by straight and curved blades

A theoretical analysis of the forces acting on the laryngoscope during the lifting of the epiglottis is carried out by applying the basic principles of statics. The static model of a laryngoscope equipped with a straight and a curved blade and the forces variation, as a function of the introduction angle and of tissue reaction application point, are described. The pharyngeal tissues and epiglottis pressure distribution on the blade is obtained, with a 1mm(2) resolution, by measurements performed in-vitro on a simulation mannequin, using straight and curved blades. The straight blade requires more effort than the curved one to obtain the same visualization of vocal cords, however forces exerted by using a laryngoscope with a curved blade do not vary linearly with the application point of tissue reaction. Average intensity of the tissue reaction has been found in the order of 32+/-11 N. Pressure distribution is maximally concentrated on the tip of curved blades (0.5 MPa on 5mm axial length), whereas it is more dispersed on straight blades (0.2 MPa on 10mm axial length). The inclination of the handle also influences the effort of the operator: for both blades, from 0 rad to 1.57 rad, the lifting force shows a total variation of about 13% of the top value, the transversal forces vary less than 6% of the top value.

The Influence of Gender and Experience on Intubation Ability and Technique: A Manikin Study

Female anaesthetists in early training commonly question whether their strength is adequate for tracheal intubation. This study investigated the influence of gender and experience on intubation ability and laryngoscopic technique.

A manikin model and purpose-designed force-transducing laryngoscope was used to test three cohorts at different levels of experience (novice, intermediate and experienced males and females, n = 65) for the axial force and torque exerted, best laiyngoscopic view obtained, success with and time for intubation and laryngoscopic technique.

There were no significant differences between novice or experienced female and male intubators in markers of their ability to intubate or in the forces generated. For novice females compared with novice males, mean success rate was 90% (80.2 to 99.9) versus 97% (91.1 to 100, P=0.29); and mean time to intubate 24 seconds (19 to 29 seconds) versus 18 seconds (14 to 21 seconds, P=0.057). With experience, the forces generated during intubation reduced and ability improved. Proximal laiyngoscope grips (close to the blade) generated lower forces than distal grips.

Female and male intubators did not differ in ability to intubate or in the forces they exerted during direct laiyngoscopy.

A Comparison of Plastic Single-Use With Metallic Reusable Laryngoscope Blades for Out-of-Hospital Tracheal Intubation

STUDY OBJECTIVE

The objective of this study was to compare, in the emergency out-of-hospital environment, intubation success rates during the first laryngoscopy for 2 laryngoscope blade types: a metallic reusable and a plastic single-use.

METHODS

An observational before-and-after study was conducted during 2 1-year periods. Adult patients were intubated by emergency physicians, anesthesiologists, or anesthesia nurses in the out-of-hospital setting with metallic reusable (first period) or a plastic disposable (second period) Macintosh 3 or 4 laryngoscope blades. Immediately after intubation, data were collected on success rate of intubation at the first attempt, intubation difficulty score, quality of laryngeal visualization, and the need for alternative airway techniques. To compare the 2 periods of the study, Wilcoxon's test was used for quantitative variables, and the chi2 or Fisher's exact test was used for qualitative variables.

RESULTS

Patients intubated with a metallic blade (594/1,177; 50.5%) and with a plastic blade (583/1,177; 49.5%) were included in the study. The first-attempt intubation success rate was higher in the metallic blade group (497/594, 84%) than in the single-use group (76%); difference 7% (95% confidence interval [CI] 3% to 12%) (P<.002). The incidence of difficult intubation, defined by an intubation difficulty score greater than 5, was lower (6% [95% CI 4% to 8%] versus 15% [95% CI 12% to 18%]) when metallic blades were used. A good laryngeal view (Cormack and Lehane classes I and II) was more frequently observed with metallic blade use (83% [95% CI 80% to 86%] versus 67% [95% CI 64% to 70%]). Alternative airway techniques such as the use of a Gum elastic bougie or an intubating laryngeal mask airway were more frequently used in the plastic blade period (12% [95% CI 10% to 14%] versus 4% [95% CI 2% to 6%]).

CONCLUSION

In out-of-hospital emergency care, the use of a plastic disposable laryngoscope blade decreased the success rate of tracheal intubation at the first attempt performed by emergency care providers.

The use of single-use devices in anaesthesia: balancing the risks to patient safety

Single-use devices are designed, manufactured and sold to be used once and then discarded. This paper addresses growing concerns about the quality of some devices. Single-use devices, manufactured at a lower cost to justify their disposal, are perceived to have a lesser efficacy, which may threaten patient safety through iatrogenic harm. There is, in addition, growing scepticism about the actual risk of contracting variant Creutzfeldt-Jakob disease and other blood-borne diseases from reused surgical instruments. Interview data suggests that when choosing to use a single-use device, clinicians balance concerns about the risk of infection against those about the risk of injury. However, despite reservations about induced harm and the unknown risk of an iatrogenic disease, most clinicians would want single-use devices used on themselves and their family if they were patients.

Changes in the Light Intensity of the Fiberoptic Laryngoscope Blade by Steam Sterilization

BACKGROUND

I investigated the effects of steam sterilization on light intensity of reusable fiberoptic laryngoscope blades.

METHODS

Six new reusable fiberoptic Macintosh laryngoscope blades were steam sterilized. The light intensity was measured, the tip of the blades was photographed, and the light intensity of six new plastic disposable Macintosh laryngoscope blades was also measured.

RESULTS

The light intensity of reusable blades exceeded that of the disposable blades after 20 sterilizations, but was significantly lower after 80 sterilizations. The photographs showed irregular lighting of the blades, which increased with repeated sterilization.

CONCLUSIONS

Disposable plastic blades provide more illumination than reusable fiberoptic blades subjected to repeated sterilization.

A comparison of tracheal intubation using the Airtraq�or the Macintosh laryngoscope in routine airway management: a randomised, controlled clinical trial

The Airtraq laryngoscope is a novel single use tracheal intubation device. We compared the Airtraq with the Macintosh laryngoscope in patients deemed at low risk for difficult intubation in a randomised, controlled clinical trial. Sixty consenting patients presenting for surgery requiring tracheal intubation were randomly allocated to undergo intubation using a Macintosh (n = 30) or Airtraq (n = 30) laryngoscope. All patients were intubated by one of four anaesthetists experienced in the use of both laryngoscopes. No significant differences in demographic or airway variables were observed between the groups. All but one patient, in the Macintosh group, was successfully intubated on the first attempt. There was no difference between groups in the duration of intubation attempts. In comparison to the Macintosh laryngoscope, the Airtraq resulted in modest improvements in the intubation difficulty score, and in ease of use. Tracheal intubation with the Airtraq resulted in less alterations in heart rate. These findings demonstrate the utility of the Airtraq laryngoscope for tracheal intubation in low risk patients.

Flexibility and light emission of disposable paediatric Miller 1 laryngoscope blades*

With the emergence of Creutzfeldt-Jakob disease and the discovery of prions in tonsillar material, there has been an increase in the number of available disposable laryngoscope blades. This has led to non-conformity over many aspects of blade design. Miller 1 disposable blades have been produced in both metal and plastic and appear to have different properties of rigidity. We examined the rigidity of 11 disposable Miller 1 blades in three different axes of force. There was a significant difference in flexibility between metal and plastic blades in both primary and torsional axis (p = 0.006). We also studied the blades' light intensity and angle of light emission, finding up to an eightfold difference in the level of illumination provided at a distance of 10 mm from the tips of the blades. The area of maximal illumination varied, with some blades providing narrow beams of light, and others provided a more dispersed field of illumination. In addition, the angle of maximal illumination varied between the blade types from a central position to one directed to the right-hand side.

Evaluation of intubation using the Airtraq or Macintosh laryngoscope by anaesthetists in easy and simulated difficult laryngoscopy--a manikin study

The Airtraq Laryngoscope is a novel intubation device which allows visualisation of the vocal cords without alignment of the oral, pharyngeal and tracheal axes. We compared the Airtraq with the Macintosh laryngoscope in simulated easy and difficult laryngoscopy. Twenty-five anaesthetists were allowed up to three attempts to intubate the trachea in each of three laryngoscopy scenarios using a Laerdal Intubation Trainer followed by five scenarios using a Laerdal SimMan Manikin. Each anaesthetist then performed tracheal intubation of the normal airway a second time to characterise the learning curve. In the simulated easy laryngoscopy scenarios, there was no difference between the Airtraq and the Macintosh in success of tracheal intubation. The time taken to intubate at the end of the protocol was significantly lower using the Airtraq (9.5 (6.7) vs. 14.2 (7.4) s), demonstrating a rapid acquisition of skills. In the simulated difficult laryngoscopy scenarios, the Airtraq was more successful in achieving tracheal intubation, required less time to intubate successfully, caused less dental trauma, and was considered by the anaesthetists to be easier to use.

A comparison of 20 laryngoscope blades using an intubating manikin: visual analogue scores and forces exerted during laryngoscopy

Fifty anaesthetists were recruited to use 20 different laryngoscope blades (one metal re-usable blade, five metal single-use blades and 14 plastic single-use blades, of which eight were bulb-type and 12 were fibreoptic-type) in a manikin to achieve a grade I Cormack and Lehane view. The anaesthetists were asked to provide visual analogue scores (VAS) for: ease of attachment of the blade to the handle; illumination; view of the larynx; and satisfaction for clinical use. The peak force applied and time to achieve the grade I Cormack and Lehane view were also measured. A cluster analysis method was used to group together blades with similar scores or measures. Ease of attachment, illumination, view, clinical use, force and duration were all significantly affected by the blade used (p < 0.0001 for all six). The mean peak force applied and mean duration for the 20 blades were 32-39 N and 4.4-9.5 s, respectively. All five metal single-use and four plastic single-use blades were always placed in the 'best' group in the cluster analysis. Two plastic blades provided a poor view and increased the duration of laryngoscopy.

Évaluation des lames de laryngoscopes à usage unique

OBJECTIVES

To assess the feasibility of switching disposable laryngoscope blades and to compare the disposable blades available on the market to reusable blades within the context of a new variant of Creutzfeldt-Jakob disease.

STUDY DESIGN

Comparative prospective study.

MATERIAL AND METHODS

Study conducted on patients intubated for surgical procedures in all operating theatres of a university hospital. The anaesthetic practitioner filled in an assessment form giving a score on nine criteria for each blade used. Data were recorded on Epi Info software. Satisfaction scores of each criterion were compared for both disposable blades and reusable blades.

RESULTS

Six brands of blades were tested with 225 blades. Disposable blades were evaluated as inferior to the reusable blades in 62% of cases. Two blades were reported as more satisfactory: the 670166 Rusch-Pilling and Vital View blades.

CONCLUSION

The disposable blades were not easily accepted by the anaesthetists particularly for difficult intubations, which is why reusable blades should not be totally removed from practice. Single-use blades proposed by different manufacturers are not identical. We chose 670166 Rusch-Pilling blades, the best adapted to our institution. The switch to disposable blades would require that blade manufacturers improve the quality of the blades.