<SNIP>
There is a school of thought that says that ventilation during CPR is
wasting valuable cardiac compression time and that sufficient oxygenated air
is entrained into the lungs during compressions.
<SNIP>

Thats something I've not really heard of, is there a reference anywhere I
can read a little more about it - interesting thought though.

Thanks

Ian S.

Below are various papers supporting and not supporting this theory
Best wishes
Andy


Authors
Kern KB, Hilwig RW, Berg RA, Ewy GA.
Institution
University of Arizona Sarver Heart Center, University of Arizona College of
Medicine, Tucson 85724-5037, USA. [log in to unmask]
Title
Efficacy of chest compression-only BLS CPR
in the presence of an occluded airway.
Source
Resuscitation. 39(3):179-88, 1998 Dec.
Abstract
Reluctance of the lay public to perform bystander CPR is becoming an
increasingly worrisome problem in the USA. Most bystanders who admit such
reluctance concede that fear of contagious disease from mouth-to-mouth
contact is what keeps them from performing basic life support. Animal models
of prehospital cardiac arrest indicates that 24-h survival is essentially as
good with chest compression-only CPR as with chest compressions and assisted
ventilation. This simpler technique is an attractive alternative strategy
for encouraging more bystander participation. Such experimental studies have
been criticized as irrelevant however secondary to differences between human
and porcine airway mechanics. This study examined the effect of chest
compression-only CPR under the worst possible circumstances where the airway
was totally occluded. After 6 min of either standard CPR including
ventilation with a patent airway or chest compressions-only with a totally
occluded airway, no difference in 24 h survival was found (10/10 vs. 9/10).
As anticipated arterial blood gases were not as good, but hemodynamics
produced were better with chest compression-only CPR (P < 0.05). Chest
compression-only CPR, even with a totally occluded airway, is as good as
standard CPR for successful outcome following 6.5 min of cardiac arrest.
Such a strategy for the first minutes of cardiac arrest, particularly before
professional help arrives, has several advantages including increased
acceptability to the lay public.


Authors
Idris AH.
Institution
Department of Surgery, Anesthesiology, University of Florida College of
Medicine, Gainesville, USA.
Title
Reassessing the need for ventilation during
CPR. [Review] [52 refs]
Source
Annals of Emergency Medicine. 27(5):569-75, 1996 May.
Abstract
In the United States debate continues about the necessity of ventilation
during CPR because of fear of contracting infectious diseases. Three
questions will be considered in this article. First, is ventilation
necessary for the treatment of cardiac arrest? Second, is mouth-to-mouth
ventilation any better than no ventilation at all? Third, are other
techniques of ventilation as effective or more effective than mouth-to-mouth
ventilation during basic life support CPR? Although research is still
inconclusive with regard to the need for ventilation during CPR, recent
findings have clarified the effect of ventilation during low blood flow
states and how ventilation influences resuscitation. Ventilation affects
oxygenation, carbon dioxide elimination, and pH during times of low rates of
blood flow. Ventilation may be unnecessary during the first few minutes of
CPR. Under conditions of prolonged, untreated cardiac arrest, ventilation
during CPR affects return of spontaneous circulation. Isolated hypoxemia and
hypercarbia independently have adverse effects on survival of cardiac
arrest. Because ventilation with exhaled gas contains as much as 4% CO2 and
less oxygen than air, it may have adverse effects during CPR. Spontaneous
gasping may provide sufficient ventilation during CPR. Chest compression
alone provides some pulmonary ventilation and gas exchange. Active chest
compression-decompression may improve gas exchange better than does standard
chest compression. Other forms of manual ventilation may also have a role in
CPR. [References: 52]



Authors
Idris AH, Banner MJ, Wenzel V, Fuerst RS, Becker LB, Melker RJ.
Institution
Department of Surgery (Division of Emergency Medicine, University of Florida
College of Medicine, Gainesville 32610-0392.
Title
Ventilation caused by external chest
compression is unable to sustain effective gas exchange
during CPR: a comparison with mechanical
ventilation.
Source
Resuscitation. 28(2):143-50, 1994 Oct.
Abstract
OBJECTIVE: To compare the tidal volume, minute ventilation, and gas exchange
caused by mechanical chest compression with and without mechanical
ventilatory support during cardiopulmonary resuscitation (CPR) in a
laboratory model of cardiac arrest. DESIGN: A laboratory swine model of CPR
was used. Eight animals with and eight animals without mechanical
ventilation received chest compression (100/min) for 10 min. Coronary
perfusion pressure, tidal volume, and minute ventilation were recorded
continuously. INTERVENTIONS: Ventricular fibrillation for 6 min without CPR,
then mechanical chest compression for 10 min. RESULTS: During the first
minute of chest compression, mean (+/- S.D.) minute ventilation was 11.2 +/-
5.9 l/min in the mechanically ventilated group and 4.5 +/- 2.8 l/min in the
group without mechanical ventilation (P = 0.01). Minute ventilation
gradually declined to 5.8 +/- 1.4 l/min and 1.7 +/- 1.6 l/min, respectively,
during the last minute of chest compression (P < 0.0001). After 10 min of
chest compression, mean arterial pH was significantly more acidemic in the
group without mechanical ventilation (7.16 +/- 0.13 compared with 7.30 +/-
0.07 units) and PCO2 was higher (62 +/- 19 compared with 35 +/- 9 mmHg).
Mixed venous PCO2 was also higher (76 +/- 15 compared with 61 +/- 8 mmHg).
CONCLUSION: Standard chest compression alone produced measurable tidal
volume and minute ventilation. However, after 10 min of chest compression
following 6 min of untreated ventricular fibrillation, it failed to sustain
pulmonary gas exchange as indicated by significantly greater arterial and
mixed venous hypercarbic acidosis when compared with a group receiving
mechanical ventilation.

Authors
Tang W, Weil MH, Sun S, Kette D, Kette F, Gazmuri RJ, O'Connell F, Bisera J.
Institution
Institute of Critical Care Medicine, Palm Springs, CA 92262.
Title
Cardiopulmonary resuscitation by precordial
compression but without mechanical
ventilation.
Source
American Journal of Respiratory & Critical Care Medicine. 150(6 Pt
1):1709-13, 1994 Dec.
Abstract
It is widely held that mechanical ventilation is essential for
cardiopulmonary resuscitation (CPR). However, cardiac output and therefore
pulmonary blood flow is reduced to less than one-third of normal during CPR.
We therefore reasoned that ventilatory requirements are correspondingly
reduced and postulated that gas exchange may be maintained during precordial
compression with oxygen passively delivered to the airway in the absence of
mechanical ventilation. After tracheal intubation, Sprague-Dawley rats were
randomized. Fifteen animals were maintained on positive-pressure ventilation
with room air and an additional 15 animals breathed spontaneously. Cardiac
arrest was induced by electrical fibrillation. The inspired gas
concentration of oxygen was then increased to 100% in both groups.
Precordial compression was begun after 4 min of untreated ventricular
fibrillation. After an additional 6 min of precordial compression,
resuscitation was attempted by DC countershock. During cardiac
resuscitation, there were no significant differences in coronary perfusion
pressure between mechanically ventilated and spontaneously breathing
animals, but arterial PO2 was significantly lower and arterial PCO2 was
significantly higher in the absence of positive-pressure ventilation.
However, neither resuscitability nor 24-h survival were affected.
Postresuscitation myocardial contractility, reflected in the maximally
generated dP/dt40, was also not adversely affected. In the unventilated
group, only resuscitated animals developed spontaneous gaspings at an
average frequency of 17 +/- 2/min-1. The current emphasis on mechanical
ventilation as the highest priority for cardiopulmonary resuscitation is
therefore not fully supported under the experimental conditions of this
study.





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