The question sometimes arises: why is the recommended compression-ventilation ratio for infants and children different from adults?
A compression-ventilation ratio (external cardiac compression [ECM] + rescue breathing) of 30:2 for basic (one-rescuer) CPR was chosen in the Consensus on Science and Treatment Recommendations for all infants (except newborns, i.e. at birth) children and adults, but a ratio of 15:2 chosen for CPR performed by two healthcare rescuers for infants (except the newly-born) and children whenever a pause is required between compressions to deliver breaths 1,2. These recommendations replace the previous recommendations of 5:1 for two-person rescue of adults, children and infants.
Unfortunately, no studies to determine the optimum compression-ventilation ratio during CPR have been performed in humans, so the recommendations are by extrapolation from studies done in animals, mannequins and computer simulations in which higher compression-ventilation ratios are favoured over lower ratios.
The rationale to recommend a new ratio higher than 5:1 is the following:
- A ratio of 5:1 may provide unnecessary ventilation. Cardiac output during good CPR is only 1/4 – 1/2 of normal cardiac output so normal minute ventilation is unnecessary for adequate ventilation- perfusion matching in the lungs, and …
- A ratio of 5:1 may obstruct venous return thereby limiting cardiac output
- A ratio of 5:1 may excessively lower blood carbon dioxide levels thereby causing cerebral vasoconstriction, and …
- A ratio of 5:1 frequently interrupts cardiac compressions, causing blood pressure to fall nearly to zero at each interruption, thereby failing to perfuse the cerebral and coronary vascular beds.
Several studies of the performance of adult CPR 3,4 showed that rescuers spent far too much time NOT giving external cardiac compression (‘hands-off time’) largely because of giving excessive ventilation instead. No equivalent studies have been examined paediatric CPR.
The ratio of 30:2 for adult CPR was chosen to encourage uninterrupted cardiac compression sequences and to decrease unnecessary ventilation.
However, children differ from adults in the following important ways:
- The different choice of 15:2 ratio for CPR of infants and children is based largely on the requirement of infants and children for higher ventilation rates than adults, and to a lesser extent on the different aetiology of cardiac arrest in children. Of course, infants and children have a wide range of ventilation during illness, ranging from a normal rate, for example, of up to 60/min at 3 months of age, 40/minute at 1 year and up to 30 minute at 12 years of age. There is also a variability of heart rate among infants and children compared with adults but it is less variable than the respiratory rate. Thus while it is reasonable to choose a fixed cardiac compression rate to suit all infants, children and adults, it is less reasonable to choose a single respiratory rate for infants, children and adults. On the other hand, it is not practical to recommend specific rates of compression and ventilation for each child according to each age.
- A much larger proportion of cardiac arrests due to the sudden onset of ventricular fibrillation occur in adults compared with children. In these victims, the lungs can be expected to contain a store of oxygen and thus ventilation is a lesser priority. In children, the incidence of ventricular fibrillation in children who arrest in hospital is approximately 10% 5,6,7 whereas the majority are due to other rhythms (asystole, hypotensive bradycardia and electromechanical dissociation) which are usually the result of hypoxaemia or hypotension or both.
Consequently, the consensus of opinion among the paediatricians who participated in the 2010 evaluation of science on resuscitation remained that ventilation should be emphasised as a prominent part of CPR for infants and children, and that a ratio of 30:2 would result in insufficient ventilation.
If 30:2 then provides insufficient ventilation for infants and children – what is the right ratio? The ratio of 15:2 was chosen because it had already been taught as a ratio for children (for single rescuer CPR), had been used successfully and thus would be less difficult to teach than a completely new ratio. Moreover, since healthcare rescuers are more likely to effect a smooth changeover from compressions to ventilation (and back to compressions) than the lay person rescuer, a 15:2 ratio may be a less severe interruption to compressions. It is realised however, that the ideal ratio remains unknown and the current recommendations need testing.
Companion questions are:
- How much ventilation is recommended after intubation and:
- How much ventilation is recommended when the circulation returns and ECM is not needed?
- If ventilation is provided with the use of an advanced airway (eg endotracheal tube, Laryngeal Mask Airway) – that is by healthcare rescuers – where no pause is required for ventilation, the ratio of 15:2, will provide excess ventilation because if compressions are given uninterrupted at 100/minute, a ratio of 15:2 would provide about 13-14 breaths per minute. That may be more than needed for ventilation-perfusion matching in the lungs, so in this circumstance, about 10 breaths per minute is the recommendation.
- If some circulation returns during resuscitation, yet spontaneous ventilation remains inadequate, an imposed ventilation rate of 12-20/minute is recommended. If normal circulation returns, a normal ventilation rate for age should be given
- Consensus on science and treatment recommendations. Resuscitation 2010; 81: 213-259.
- Australian Resuscitation Council. Guidelines 7; 12.2.
- Wik L, Kramer-Johansen J, Myklebust H et al. Quality of cardiopulmonary resuscitation during out-of-hospital cardiac arrest. JAMA 2005: 293: 299-304.
- Abella B, Alvarado JP, Myklebust H et al. Quality of cardiopulmonary resuscitation during in- hospital cardiac arrest. JAMA 2005; 293: 305-370
- Samson RA, Nadkarni VM, Meaney PA et al. Outcomes of in-hospital ventricular fibrillation in children. NEJM 2006; 354: 2328-39.
- Young KD, Seidel JS. Pediatric cardiopulmonary resuscitation: a collective review. Anna Emerg med 1999; 33: 195-205.
- Tibballs J, Kinney S. A prospective study of outcome of in-patient paediatric cardiopulmonary arrest. Resuscitation 2006; 71: 310-318.
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