Video laryngoscopy may improve overall and first-pass success rates for ET intubation by paramedics
Medic 14 and Engine 27 respond to a report of breathing difficulty at a private residence. The engine arrives first to find a 68-year-old male experiencing severe shortness of breath. The patient’s wife states the patient has not been feeling well all day but suddenly became worse about 30 minutes before she called 911.
The patient is slumped over in a recliner in the living room. Although the patient has a palpable radial pulse, he is displaying an agonal breathing pattern. The firefighters quickly move the patient to the floor and begin assisting ventilations with 100 percent oxygen. The patient’s blood pressure is 108/64, the heart rate is 120, SpO2 is 82 percent, and the ETCO2 is 68 mm Hg.
Paramedic Owens decides to insert an endotracheal tube but is unable to visualize the vocal cords. As the team resumes assisted ventilation, his partner retrieves the video laryngoscope. Medic Campbell is able to quickly visualize the glottis opening and insert the tube. The team verifies correct placement and resumes assisted ventilation.
During transport to the hospital, both the pulse oximetry and capnography values improve. There are no complications during transport.
Later in the station, Campbell admits that he does not think he would have been able to successfully place the tube without the video laryngoscope. He mentions he is glad the department spent the money to place one on every apparatus. He believes it will make a big difference in intubation success rates for the department.
Study review of video laryngoscope use
Researchers in California performed the first meta-analysis of data comparing intubation success rates between direct laryngoscopy and video laryngoscopy in a clinical setting .
When measuring overall intubation success, seven studies met the inclusion criteria with a combined sample size of 3,422 participants. The authors prospectively defined overall intubation success as placement of an ET tube into the trachea of a single patient regardless of the number of attempts.
Physicians in the out-of-hospital environment were about 95 percent less likely to correctly place an ET tube when using a video laryngoscope compared to the traditional intubation procedure using direct laryngoscopy. In contrast, non-physicians (which include nurses and paramedics) were twice as likely to have a successful intubation (regardless of the number of attempts) when using a video laryngoscope instead of the direct laryngoscope technique.
For the outcome measure of first-attempt success, eight studies met the inclusion criteria with a combined sample size of 3,552 participants. The researchers defined first-attempt success as tracheal placement of the tube in a single patient on the first attempt.
Similar to the overall outcome, physicians were 68 percent less likely to successfully place the ET tube on the first attempt when using video laryngoscopy instead of direct laryngoscopy. On the other hand, non-physicians were about twice as likely to successfully place the tube on the first attempt when using video laryngoscopy instead of direct laryngoscopy.
What the results mean for you
ET intubation is an infrequent procedure in the out-of-hospital environment, accounting for less than 1 percent of all procedures performed . EMS systems can expect about 8 cases requiring ET intubation for every 1,000 emergency responses . Despite the infrequent opportunity to perform ET intubation, some argue it is an essential out-of-hospital procedure for improving the care of critically ill patients [4,5].
One key component of efficacious out-of-hospital ET intubation is that paramedics secure the airway as early as possible, ideally placing the tube correctly on the first attempt.
In an Australian prehospital study of advanced airway management during cardiac arrest, successful intubation on the first attempt resulted in a 52 percent increase in the odds of achieving return of spontaneous circulation (ROSC) and a 26 percent increase in the odds of survival to hospital discharge .
Making multiple ET attempts places the patient at an increased risk for adverse events. A study conducted at a level one trauma center found a nine-fold increase in hypoxemia (10.5 percent vs. 70 percent) and a 14-fold increase in severe hypoxemia (1.9 percent vs. 28 percent) when anesthesiologists performed three or more intubation attempts compared to two or less .
This meta-analysis suggests overall and first attempt intubation success rates improve for paramedics and nurses who use video rather than direct laryngoscopy. This is in contrast to a more recent observational analysis where introduction of video laryngoscopy into an urban EMS system did not improve first pass success rates over direct laryngoscopy for patients who suffered out-of-hospital cardiac arrest .
Similarly, a recent pilot trial involving suburban and rural EMS systems could demonstrate no improvements in overall or first time success rates between intubation with a video laryngoscope or with direct laryngoscopy . The researchers in the pilot trial reported that medics in the participating EMS agencies averaged less than one intubation per medic per year. Thus, the pilot trial represents the introduction of video laryngoscopy into an area providing infrequent opportunity for medics to perform the skill.
Some argue that video laryngoscopy may prove useful for difficult airway situations, which commonly occur in the out-of-hospital environment . Researchers using a manikin simulated a victim with a threatened airway trapped upside-down in an overturned vehicle and found no difference in first attempt success rates when experienced paramedics and prehospital registered nurses used a video laryngoscope or inserted a supraglottic airway . In contrast, first attempt success rates were significantly lower when using direct laryngoscopy.
One interesting outcome of this study suggests that physicians using video laryngoscopes do not enjoy the same degree of improvement in intubation success rates that paramedics do when using the same devices. One possible reason may lie in the training and experience levels of the two groups. The physicians in this meta-analysis reported a baseline of at least 80 intubations per year per provider while the paramedics and nurses reported between 2.9 and 12 intubations per year per provider. This difference in skill level and comfort with direct laryngoscopy could account for the results.
Similarly, video laryngoscopy may not have added value over direct laryngoscopy in EMS agencies with highly trained personnel. Researchers in Pennsylvania studied the non-randomized use of a video laryngoscope in a helicopter EMS agency . Each member of the medical flight crew in that system performed more than 12 ET intubations per year on actual patients. Additionally, each member had to pass a yearly skills review and participate in high-fidelity airway simulations. Although use of the video laryngoscope did improve the glottic view for the crew, it did not improve first time or overall success rates compared to direct laryngoscopy. This is similar to the results of an in-hospital study in which improvement in first attempt success rates decreased as the skill and experience level of the medics increased .
The out-of-hospital use of video laryngoscopy in children remains poorly studied. Video laryngoscopy in children 18 years of age or younger by trained anesthetists may help improve visualization of the glottis when compared to direct laryngoscopy, however, video laryngoscopy also increases the time it takes to successfully place the ET tube .
A meta-analysis of in-hospital elective or emergency intubation performed by anesthetists involving children between the ages of 28 days and 18 years found longer intubation times, no difference in first attempt success rates, and an increased number of unsuccessful intubation attempts associated with video laryngoscopy when compared to direct laryngoscopy .
There is some concern that the cost of some models of video laryngoscopes could prohibit their widespread adoption in systems with few yearly advanced airway cases and limited budgets, especially in rural or volunteer systems . However, if adoption results in improved efficacy, a reduction in medical errors, and improved documentation, the expense may be justified.
Limitations of the present study
As regards to this study, it is important to briefly define a meta-analysis. Where a published research article often reports the results from a single experiment, a meta-analysis can combine the data from many similarly conducted experiments and report the outcome results as if they were one experiment. By combining the data from many smaller studies, researchers can effectively simulate the results of a single experiment with a much larger sample, which can provide a clearer picture of whether the intervention in question is beneficial or harmful.
A well-conducted meta-analysis requires the research team to prospectively define the criteria each published research article must meet for inclusion in the analysis. This is called a systematic review. For this analysis, the research term only included articles published in the English language involving out-of-hospital ET intubation on living human patients (no cadavers). The authors excluded case reports or series, and further excluded studies limited to children, animals, manikins or cadavers. The researchers did not limit their analysis to specific brands of video laryngoscopes.
One potential problem of choosing out-of-hospital studies conducted in other parts of the world is that some countries staff ambulances with physicians rather than paramedics. This can make it difficult to compare the results of a study involving physicians to the results of a study involving paramedics. To provide clarity, the research team analyzed and reported outcomes separately for physician EMS providers.
There are a number of limitations in this meta-analysis that effect how far one can generalize the results. First, all of the studies involving paramedics and nurses (non-physicians) used in the meta-analysis were either non-randomized or retrospective. These study designs have an increased risk of introducing a type of measurement error known as bias. When used in a research context, the word bias does not have the same meaning as when used in everyday language. Bias in research simply means an unintended tendency to achieve a certain outcome .
In contrast, the risk of bias was much lower for the studies involving physicians. This is because all of the research designs for the studies involving physicians involved randomization, a design strategy that can reduce bias. Thus, the research designs for the studies involving paramedics and nurses had more measurement error than did the studies involving physicians.
Summary of video laryngoscope usage results
This meta-analysis suggests that video laryngoscopy may improve overall and first-pass success rates for ET intubation by paramedics. This benefit may be less pronounced (or even non-existent) in settings with highly trained and skilled medics. Despite the potential benefit demonstrated here, there is still no evidence indicating that advanced airway control in the out-of-hospital environment using video laryngoscopy by paramedics improves survival outcomes. More research is needed in this area.
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