The ErgoMask

 

 
 
 

Adrian A. Matioc, MD | | Thursday, November 6, 2008


As anyone reading this article likely knows, the bag-valve mask (BVM) is the standard prehospital ventilation device. Timely and successful oxygenation and ventilation of patients is the provider's essential duty.

Every provider is familiar with the challenges and rewards encountered with the BVM technique. The two-hand ("two-person") BVM technique is considered optimal, while the one-hand ("one-person") BVM technique is considered challenging with suboptimal results. Nevertheless, the one-hand technique is the most frequently used by health-care providers in the prehospital and hospital environment.

This article introduces the new ergonomic face mask -- the ErgoMask (King Systems, Noblesville, Ind.) -- designed to optimize the one-hand BVM ventilation technique.

Face Masks -- Then & Now

Since its introduction in the practice of anesthesia in 1847, the face mask design had all the current characteristics: a dome with left/right symmetry, a cushioned interface and a connector. The changes made to the face mask after the introduction of muscle relaxants, positive pressure ventilation and the self-inflating resuscitator bag improved the material (i.e., more transparent, softer and disposable) but not its functionality. The generic face mask has a neutral dome with a symmetrical design that gives no indication for an optimal one-hand grip.

The clinical marker of a good face mask seal is the absence of a leak, and the clinical marker of an effective airway maneuver is the maximal increase of the distance between the chin and sternum. This translates in adult patients to a maximum head extension of 42 degrees measured between the longitudinal axis of the head and the longitudinal axis of the face mask (see photo 1).

When a provider uses a one-hand technique, they apply a unilateral, asymmetrical (left) grip to generate the airway maneuver and the seal. The generic left-hand grip with the 5th finger at the left mandibular angle doesn't generate a jaw thrust, and the 3rd and 4th finger on the left mandibular ramus will not generate a chin lift (see photo 2). Experts have long considered support of the angle of the mandible by one hand insufficient for the maintenance of a patent airway.

Thus, this one-hand face mask technique is not optimally served by the symmetrical design of the generic face mask. The one-hand face mask technique would be more effective with an asymmetrical face mask.

The Adult Ergonomic Face Mask

The adult ergonomic face mask, ErgoMask, has an asymmetrical dome with the left side larger than the right. The airway connector is off center (to the front right of the mask), and the dome has grooves and edges, creating an asymmetrical dome to accommodate the asymmetrical left-hand grip: the chin-lift grip (see photo 3).

The dome has a teardrop rim around the airway connector to allow the grip by the thumb and index finger. These fingers reach maximally and control the seal on the right side of the mask. The hypothenar area rests on the posterior contoured ridge controlling the posterior seal. The rest of the palm controls the left side of the mask while fingers three, four and five reach for the chin and control the anterior seal (see photo 4).

Full contact between the hand and a handheld device is a fundamental ergonomic principle. The chin-lift grip controls the whole mask. The ergonomic hand placement on the dome combines a 45 degree hand pronation with a neutral wrist position (the hand and forearm in straight line).

'Chin Lift' Grip & the ErgoMask

The generic face mask technique -- first "push" the mask and then "pull" the mandible -- is reversed with the ErgoMask technique: the provider first "pulls" the mandible (chin lift-head tilt) then "pushes" the mask (seal). The airway maneuver is applied before the seal and maintained throughout the ventilation.

The "chin lift" grip is implemented by first applying the chin lift to the mentum with the left middle and ring finger, stretching the chin- sternum space and extending the neck (see photo 5). After placing the mask on the patient's face the thumb and the index finger engage the rim and reach maximally on the right side of the mask. The wrist is straight. The transparent window between the thumb and the index finger will allow observation of the patient and the fogging of the mask.

Photo 6 presents an optimized left hand "chin lift" grip with the ErgoMask applied to a patient. The angle between the longitudinal axis of the head surface and the longitudinal axis of the face mask is approximately 30 degrees. The head extension was limited because of cervical pathology. This is less than the ideal 42 degrees. A rough estimate of the 42 degrees can be achieved by the angle between the index and middle fingers making the "V" sign. The adherence is low between the gloved hand and the beard. This deteriorates even more with a wet beard (rain, lubricant, vomit). A short chin masked by the beard adds to the challenge. The low adherence and the short chin can be addressed by using a towel, gauze or any cloth between the hand and the beard.

Two-Hand ErgoMask Technique

The ErgoMask dome is asymmetrical, but the cushion and circumference are symmetrical, allowing jaw thrust and bilateral pressure on the mask for the two-hand technique.

Cervical Spine Injury & Airway Management

Cervical spine injury accompanies 2% of blunt traumas. In trauma care, the priority is still adequate airway management. All airway maneuvers will result in some degree of neck movement. If cervical movement is required in an uncleared cervical spine to open an airway this must be done with minimum movement possible. This can be accomplished with the one-hand ErgoMask technique -- as with any airway management technique -- with manual in line stabilization that will minimize neck extension.

Optimized BVM Attempt

Further steps to improve the one-hand face mask ventilation attempt:

  • Adjust the bed height to allow the hand grip with a straight wrist, elbow close to the chest and straight back. This position can be used also when the patient is on the ground and the provider is kneeling.
  • Place the patient's head in sniffing position (if not contraindicated).
  • Appropriately use of an oropharyngeal or nasopharyngeal airway in the unconscious patient who seems difficult to bag (e.g., male, edentulous, obese, head in neutral position).

Conclusion

The BVM is losing the popularity contest to the more glamorous supraglottic airways and intubation devices. Nevertheless, the one-hand BVM is the standard ventilation technique in the prehospital environment. Continuous efforts should be made to improve face mask ventilation technique and training. An optimized one-hand face mask attempt will increase the ventilation success rate, reduce the complication rate and enable the user to recognize failure quickly and move to the next airway technique (e.g., two-hand face mask ventilation, endotracheal intubation, supraglottic airway).

Adrian A. Matioc, MD, is a clinical associate professor in the Department of Anesthesiology at the University of Wisconsin Hospital and Clinics and William S. Middleton Memorial Veterans Hospital, Madison, Wis. He's also a former MedFlight physician at the University of Wisconsin Hospital and Clinics. Contact him atadrian.matioc@va.gov.

Author Disclosure: Dr. Matioc receives royalties for the ergonomic face mask product from King Systems.

References

1. Safar P, Escarraga LA, Chang F: "Upper airway obstruction in the unconscious patient."Journal of Applied Physiology. 14(9): 760Ï764, 1959.

2. Schneider RE, Murphy MF: "Bag/mask ventilation and endotracheal intubation."Manual of Emergency Airway Management, Second Edition. Lippincott Williams and Wilkins: Philadelphia, 2004. pp. 43Ï69.

3. Paal P, von Goedecke A, Brugger H, et al: "Head position for opening the upper airway."Anaesthesia. 62(3): 227Ï230, 2007.




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