Current thinking on both BLS and ACLS, if you are to believe the advertising, seems to point to early defibrillation as the great panacea of cardiac arrest management. It has been shown that early defibrillation is essential and should have the highest priority. However, have we neglected the first two letters of the alphabet in favour of the third?

Airway management and Breathing (ventilation) are little discussed and do not seem to stir the emotions as much as the newest defibrillator coming on to the market.

Everyone seems to be satisfied with their "Tried and Trusted" method of ventilation (most commonly the Big-Valve-Mask resuscitator) and they tend to be more reluctant to change to more effective devices.

The AHA Guidelines(1) (as published in The Journal of the American Medical Association - "JAMA" October 28, 1992) clearly raise the concerns over the inability of many rescuers to deliver adequate tidal volumes when using a BVM(2),(3) These guidelines also state that the selected tidal volume should be delivered over 2 seconds. This is to reduce the flowrate to the patient which in turn lowers the airway pressure generated by squeezing the bag.

This reduces the risk of gastric distention and aspiration of stomach contents(4). It should also be noted that the AHA recommends the use of 1005 oxygen during BLS and ACLS which, of course, a standard BVM will not provide unless adjunct equipment is available. the reasoning for this is that hypoxia leads to anaerobic metabolism and metabolic acidosis, which can frequently blunt the beneficial effects of chemical and electric therapy.

Automatic Transport Ventilators (ATVs) are stated by the AHA to offer improved lung inflation with diminished or absent gastric distension when compared to other devices including mouth-to-mask, bag-valve-mask and manually triggered devices(5),(6),(7). In particular they provide superior ventilation to BVMs(8) (especially in unintubated patients where both hands are free for mask and airway maintenance. This is only possible with a BVM if one rescuer holds the mask and a second squeezes the bag).

ATVs do require an oxygen source to enable the device to ventilate the patient which, as the AHA recommends ventilation on 100% oxygen, should already be available. The concern expressed over the lack of "feel" when using an ATV as opposed to a BVM is valid in the mind of the rescuer but this concern has to be taken in context of the AHA's overall statement that BVMs provide insufficient airway problems.

If finance is a concern (which it is to most of us) let's look at the facts:

• ATVs offer superior ventilation (and what good is a $5,000 defibrillator if the patient is inadequately ventilated?
• ATVs reduce the man power requirement of a BVM by half (if you follow the AHA Guidelines1 and published works8 and have two persons ventilating the patient).
• ATVs improve lung inflation and reduce gastric distention.
• ATVs allow both hands to remain on the mask to facilitate a superior mask to face seal and improved airway maintenance.
• By maintaining a constant minute volume and adequate arterial blood gases(9),(10) the patient on an ATV arrives in a more stable condition at the ER improving the patient's chances of survival.
• ATVs free the rescuer for other tasks i.e. I.V. therapy, drug therapy, trauma management, defilbrilation etc.

Defibrillators are an essential part of cardiac arrest management. The use of operator powered devices (BVMs or pocket masks) for patient ventilation do not provide for the best possible outcome and can reduce the effectiveness of electrical stimulation therapy. Also, operator powered devices do not support the patient that is suffering from "shortness of breath" and requires enhanced oxygen concentrations as opposed to positive pressure ventilation. Therefore, when assessing your Cardiac/Respiratory Arrest equipment needs, check the ABCs and make sure you are not taking a dyslexic look at the way in which your patients needs are addressed.

References

1. A.H.A. Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiac Care - J.A.M.A. Oct. 28, 1992:2171-2295
2. Elling R., Politis J. An evaluation of emergency medical technicians' ability to use manual ventilation devices. Ann Emerg Med. 1985; 3:292-296
3. Hess D. Baran C. Ventilatory volumes using mouth to mouth to mask and bag-valve-mask techniques. Am J Emerg Med 1985;3:292-296
4. Fuerst D, Banner MJ, Melker RJ Inspiratory time influences the distribution of ventilation to the lungs and stomach: Implications for Cardiopulmonary Resuscitation. Ann Emerg Med. in press
5. Branson RD, McGough EK. Transport ventilators Probl Crit Care. 1990;4:254-274
6. Melker RJ A clinical evaluation of the pneuPAC ventilator. Presented at the 4th world congress on intensive care medicine July 1985; Jerusalem, Israel
7. Hurst JM, Davis K Jr, Branson RD, Johannigman JA. Comparison of blood gases of ventilated patients during transport. J Trauma. 1989;29:1637-1640
8. Jesudian MC, Harrison RR, Keenan RL, Maull KI. Bag-valve-mask ventilation: two rescuers are better than one preliminary report. Crit Care Med. 1985; 13:122-123
9. Braman SS, Dunn SM, Amico CAS, Millman RP. Complications of intra-hospital transport in critically ill patients: Ann Intern Med. 1987; 107: 469-473
10. Gervais HW, Eberle B. Konietzke D, Hennes HJ, Dick W. Comparison of blood gases of ventilated patients during transport. Crit Care Med 1987; 15:761-763