HEAVEN Knows This Airway Will Be Hard

With more than 300 bases in 48 states and around 4,500 team members, Air Methods is the country’s largest air-medical provider. It carries around 100,000 seriously ill and injured patients per year, many of whom require airway management.

But across the company a few years back, intubation was proving a problem. It just wasn’t happening as quickly and trouble-free as anyone wanted. First-attempt success rates needed improvement, and adverse events needed to be minimized. 

There was plenty of data to scrutinize, and top company leaders burrowed into it. What they discovered ultimately led to the development of a new tool that’s showing promise in streamlining airway care in the flight and other difficult environments. 

“We saw it wasn’t just one area or one region having problems—it was across the country,” says Dave Olvera, NRP, FP-C, CMTE, the company’s clinical education manager. “And when we really looked at it, we realized the LEMON criteria is phenomenal—it really works well—but there’s little to no research that shows it’s successful in the prehospital or emergent setting. We wanted to find something that could accommodate all of the flight setting, the ground setting, and what I call the ‘out of the operating room experience,’ where you have that crash airway in the NICU, in the emergency department, in the air—any of those situations—and address them all together.”

The result was HEAVEN, an acronym for six key attributes that can help crews determine the likelihood an emergency-intubation patient will pose a difficult airway. 

HEAVEN stands for:

• Hypoxemia 
• Extremes of size 
• Anatomic challenges 
• Vomit/blood/fluid 
• Exsanguination/anemia 
• Neck mobility issues. 

The criteria were derived through a retrospective review of records for more than 500 patients who’d needed rapid sequence intubation in an air-med setting.¹ Sixty-three of those required more than one intubation attempt; the reasons for that were grouped to discern the main categories. 

The resulting criteria “represent a set of difficult airway predictors that may be applied prospectively by emergency airway personnel, facilitating airway decision making,” Olvera and coauthor Daniel Davis, MD, wrote, but should also be validated prospectively.¹ 

Built to Evolve

HEAVEN rolled out in 2015, and it’s now used companywide by Air Methods and has been adopted by several other groups in the U.S. and Latin America. Further research has helped flesh out its strengths and areas for potential sharpening: For presaging first-attempt failure, it showed a sensitivity (true positive rate) of 80%, specificity (true negative rate) of 43%, positive predictive value (the probability subjects with positive screenings truly have difficult airways) of 19%, and negative predictive value (the probability subjects without positive screenings truly don’t have difficult airways) of 93%. That’s a strong NPV, but “overall test characteristic performance was moderate,” investigators found.² 

Fortunately it’s built to evolve. 

“The tool is meant to change every five years,” Olvera says. “Say we learn that neck mobility is a huge issue. So we’ll learn to combat that, whether we do inline stabilization or move the anterior part of the c-collar, or whatever we do. Then it may not be one of the main predictors anymore, so we can take the N out and put something else in. Say we find saturation becomes an issue—we just can’t maintain our saturations appropriately. Then we can call it HEAVES.

“It’s made so that every five years or so, as we improve practice, we can improve the mnemonic and make it more applicable to current issues and standards.” 

The Role of Video

The familiar mnemonic for predicting a difficult intubation is of course LEMON (look externally, evaluate using the 3-3-2 rule, Mallampati score, obstruction, and neck mobility; some add S for saturation). The problem with LEMON in the field is that LEMON wasn’t meant for the field. It was designed for the operating room and migrated outward. In an EMS setting it has drawbacks. Obviously, 3-3-2 evaluations and Mallampati scores can be difficult to obtain if a patient is unresponsive or combative. And LEMON was never really built for video intubation. 

HEAVEN averts those mouth problems but may have even greater utility as an indicator for videoscopic intubation. 

Says Olvera: “I think HEAVEN helps guide us down a path where we can look and say, ‘OK, we’re going to be more successful with video in this case than direct laryngoscopy.’ There just hasn’t been research, prehospital or in-hospital, in the emergent airway to be able to validate that one way or the other. But we’ve found that depending on which criteria you’re falling into, one could be more successful than the other.” 

Air Methods supplemented its HEAVEN rollout with videoscopic intubation training, integrating also Dr. James DuCanto’s SALAD (suction-assisted laryngoscopy and airway decontamination) technique for clearing the contaminated airway and use of an RSI checklist. The aggregate result has been improved first-pass success—as a company, Air Methods’ rate is over 90%—and more comfortable, confident providers. 

“The flight setting’s kind of interesting,” Olvera says. “We’ll have nurses come in who have never touched a laryngoscope blade, and then they finish orientation, and their first call may require them to intubate. Providing this HEAVEN criteria allows them to slow things down, figure out what they want to do, and develop a plan. It works well with our ground crews and our hospital crews and lets us all work well together to mitigate these potential disasters.”

Keys to Success

A key adjunct to the HEAVEN tool is an RSI checklist Air Methods designed to help manage that process successfully. Development took several years as the company whittled three pages’ worth of initial instruction down to usable form. 

A key aspect is that the checklist isn’t actually used by the flight crew—it’s given to someone else. 

“Our crew members don’t read it to each other—they hand it to one of the other providers on scene to read aloud,” Olvera says. “That could be a nurse at the hospital or a member of the ground crew—it could even be a tow truck driver. As long as the person can read, that’s all we need. 

“What that does is prevent cutting corners. If you and I work together all the time, and I know you set up your suction and put it under the head of the bed and you always have it ready and it’s good to go, I might skip that step on the checklist. Then the one time you don’t have your suction ready, we’ll have a bad outcome. So to prevent that bias, we hand it to somebody who’s not part of the flight crew. And that’s been named a best practice by CAMTS.” 

Other new research examined air-med intubation success during transport vs. on scene.³ Stationary settings yielded a first-pass success rate of 90.5%, transport attempts a rate of 91.1%. Transport attempts did, however, have a higher rate of oxygen desaturations (30.6% vs. 23.2%). 

Video intubation has helped raise that transport success rate, which likely would have been much lower a few years ago. 

“With the advance of videoscopic intubation and opportunity to intubate in different areas, you will eventually get the airway,” Olvera says. “But I think what we’re finding as we analyze the data is that while our first-pass success is better in those situations, we may not properly prepare: We don’t have enough sets of hands, we may not have the optimum opportunity to preoxygenate the patient, suction, do all that appropriately, and we may kind of rush into it.”

That’s led to a preference, within Air Methods and increasingly across the industry, for intubating on scene, even if it takes an extra few minutes. 

“The trend is turning that way,” Olvera adds. “It’ll be a challenge to change what we’ve always done, but I think for the safety of patients and crews and better patient outcomes, it’s what we need to do.”  

References

1. Davis DP, Olvera DJ. HEAVEN Criteria: Derivation of a New Difficult Airway Prediction Tool. Air Med J, 2017 Jul–Aug; 36(4): 195–7. 

2. Olvera DJ, Davis D, Wolfe AC, Jr. Test Characteristics of a Novel Difficult Airway Prediction Algorithm for Emergency Airway Management. World Airway Management Meeting 2015, www.epostersonline.com/wamm2015/node/448. 

3. Olvera DJ, Davis D, Wolfe AC, Jr., Swearingen CF. Abstract 1: Airway Intubation Stationary vs. Transport. Air Med J, 2016 Jul–Aug; 35(4): 206–7. 

John Erich is senior editor of EMS World. Reach him at john.erich@emsworld.com.