College Answer

Reasons supporting the statement

Physiological:
a) In cardiac arrest heart dilates acutely. Decompression  of the heart occurs with good compressions
b) Ventilation can lead to decreased venous return
c) Passive ventilation still occurs with compression only CPR
d)  Gasping  can  provide  adequate  ventilation  and  in  presence  of  a  partial  airway obstruction may lead to increased venous return

Logistic reasons:

a) Reluctance  to perform  mouth  to mouth  by rescuers  therefore  some  people  do not attempt CPR.
b) Interruption to compressions therefore limiting their effectiveness

c) Easier to teach compression only CPR.
d) Out of hospital arrests it will minimise time to hospital.

e) Useful particularly in the setting of a single rescuer

Studies:

Mostly observational or animal. Some RCT
No difference in outcome using compression only versus standard CPRs in most studies
Evidence of value of good compressions

Against:

Most studies are observational.
Reported survival is no better with compression only therefore why change.
Data for most studies are prior to the change in recommendation   to 30:2 RATIO Ventilation is important for many arrests EG drowning/children/in hospital arrests ARC not recommend as standard practice

Present position: 
Not standard currently. Wait further studies. It can be used if rescuer is reluctant to use mouth to mouth

Discussion

This discussion is written in late 2014, with the benefit of four ensuing years of research and policy change.

Introduction

• Compression-only CPR dispenses with recommendation to interrupt CPR for breaths.

Rationale

• In cardiac arrest, ardiac output is the rate-limiting step of oxygen delivery
• Compressions create enough passive circulation for adequate gas mixing to occur
• Breath pauses in compressions may be counterproductive (as they allow cardiac output to decrease)
• Reluctance to provide mouth-to-mouth may discourage all CPR attempts in lay rescuers

Advantages

• Easier to teach
• Easier to perform as a single rescuer
• Definitely better than no CPR
• May encourage grossed-out lay rescuers to provide some CPR, rather than no CPR
• Uninterrupted compressions may be of better quality

Disadvantages

• Supporting data is mainly from animal studies
• Positive pressure ventilation may be essential in drowning, pulmonary oedema, airway obstruction, etc.

Evidence

• In 2007, two observational studies published in Circulation (Iwami, Taku, et al. and Bohm, Katarina, et al.) did not find any survival benefit (or if you rather, confirmed equivalent efficacy) for compression-only CPR.
• A 2010 RCT from NEJM compared the two strategies and again found no mortality difference.
• A larger observational study published in 2011 found some difference, favouring conventional CPR.
• A 2014 meta-analysis confirmed that there is no difference in mortality between conventional and compression-only CPR, but admitted that the issue "is unclear for the patients with noncardiac cause of arrest and with long periods of untreated arrest."

Current status of recommendations

• The ARC still recommends a 30:2 compression-ventilation ratio. "The ARC has extensively reviewed the recently published evidence and does not consider it to be of sufficient magnitude to warrant a change in the current guidelines"
• The ARC also recommends you provide compression-only CPR if you are for some reason unwilling to provide proper CPR.