The various conditions which affect patient's respirations require a variety of protocols and equipment to treat. Oxygen therapy equipment, Bag-Valve-Mask resuscitators, manually triggered oxygen powered ventilators, Demand Valves and automatic ventilators all currently have a place in the patient care arsenal of the emergency healthcare provider.

No one of these adjuncts to the skill of the healthcare provider can be used in isolation to treat all respiratory conditions. In fact it is standard practice to carry a range of products on the ambulance to suit the specific and ever changing needs of the patient. Consider the patient who, on your arrival at the call, exhibits chest pain and shortness of breath. One of your first reactions would be to reach for the oxygen therapy equipment and commence the delivery of oxygen through a therapy mask.

The patient then begins to show signs of respiratory distress and you decide to assist their own ventilations by providing positive pressure ventilations in time with their inspiratory effort. This can be performed with either a Bag-Valve-Mask or manually triggered, oxygen powered "demand valve".

Here I would like to clear up a misnomer that pervades the EMS market. It is common practice to label all manually triggered ventilators (whether or not they provide demand flow) as "demand valves". This is incorrect and misleading. The true definition of a Demand Valve is:

"A device which will provide a flow of air or oxygen when a negative pressure ( the patient's inspiratory effort) is applied to the outlet of the device. This gas shall be provided at a flowrate and pressure equivalent to that demanded."

This distinction is important. Demand breathing can be extremely useful for severe respiratory distress where allowing the patient to demand breathe on 100% oxygen can be very beneficial. It can also be of great benefit in trauma patients who have a reduced oxygen carrying capacity due to blood loss. The purchase of a resuscitation device which has this "demand breathing" capability should be considered. It is important to note however that the flowrate requirements for demand breathing and manual ventilation differ. The ISO 8382:1988 Standard on "Resuscitators Intended for Use with Humans"¹ states that - the "demand breathing" minimum flowrate must be at least 100 lpm while the manual positive pressure ventilation flowrate shall be a maximum 40 lpm. These parameters are also required by the 1992 American Heart Association "Guidelines for CPR" published in the Journal of the American Medical Association, October 26th 1992². There are devices available which are unable to meet both these requirements. They often have a high demand flow and high manual flow (vastly in excess of the 40 lpm) or both flowrates are set low (demand flowrate being well below the required 100 lpm minimum).

Now. Back to the patient who has just gone into full respiratory and/or cardiac arrest!!! You now have to commence full ventilatory support and cardiac massage ( if in cardiac arrest). If you are alone in the back of a fast moving ambulance you have to perform both chest compressions and ventilations as well as set up an I.V., defibrillate, administer drugs and with your spare hand hang on!

The "Guidelines for CPR"² from the AHA, recommend that two persons ventilate with a bag-valve-mask resuscitator3 to obtain the best possible ventilations. One person should be holding the mask and one squeezing the bag, but you're on your own! Now, what if the patient recommences spontaneous breathing? What piece of equipment will you reach for next? Demand Valve? Therapy kit? What!!! This scenario is not implausible or impossible to visualize. In fact I am sure that most of you reading this article have "been there" more than once. So what is the answer? The A.H.A.² recommends the use of Automatic Transport Ventilators ( ATVs) to replace the bag-valve- mask resuscitator that has been the mainstay of the emergency respiratory care market for nearly 40 years.

The ATV provides automatic ventilations to the patient, helping to free up the healthcare provider (when used in conjunction with either an E.T. tube or head harness system) to perform other tasks. ATVs ventilate in a controlled manner with low flowrates that minimize the risk of gastric distension. They also provide the ability to select delivered tidal volumes and frequencies of ventilation in line with the patient's requirements.

Additional desirable features include:

• Demand Breathing capability with a minimum 100 lpm flowrate.
• Manual ventilation option with a flowrate set at 40 lpm.
• The inclusion of a mechanism that will recognize a patient's spontaneousbreaths and will inhibit automatic ventilations to avoid "stacking" of ventilations while allowing the patient to demand breathe.

These features make the ATV a real asset to the healthcare provider as well as replacing four pieces of equipment (BVM, demand valve, manual ventilator and therapy kit). This one device also does all things more efficiently, with less stress on the healthcare provider and superior care for the patient.

Conclusions

A wealth of clinical evidence supports the discontinuance of the use of Bag-Valve-Mask resuscitators and replacing them with Automatic Transport Ventilators^3456789. Some of the ATVs currently available also have features which replace other devices currently used to support the patient in various stages of respiratory distress.

So why do we continue to use multiple pieces of equipment to provide the care our patients demand? Especially when this can be achieved with one device which offers greater benefits to the patient, improved levels of care and less stress to the healthcare provider. So, when your patients demand 100% make sure your equipment can provide it!

References

1. ISO 8382-1988 "Resuscitators Intended for use with humans"
2. A.H.A Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiac Care - J.A.M.A Oct.28, 1992:2171-2295
3. 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
4. Elling R, Politis J. An evaluation of emergency medical technicians' ability to use manual ventilation devices. Ann Emerg Med. 1983;12:765-768
5. Hess D, Baran C. Ventilatory volumes using mouth to mouth, mouth to mask and bag-valve-mask techniques Am J Emerg Med 1985;3:292-296
6. Fuerst RS, Banner MJ, Melker RJ. Inspiratory time influences the distribution of ventilation to the lungs and stomach: implications for cardiopul- monary resuscitation. Ann Emerg Med. In press.
7. Branson RD, McGough EK. Transport ventilators Probl Crit Care. 1990;4:254-274
8. 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
9. Hurst JM, Davis K Jr, Branson RD, Johannigman JA. Comparison of blood gases of ventilated patients during transport. J Trauma. 1989;29:1637-1640.