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Abstract
Background Most cases of delivery room cardiopulmonary arrest result from an asphyxial process. Experimental evidence supports an important role for ventilation during asphyxial arrest. The optimal compression: ventilation (CV) ratio remains unclear and recommendations for newborns have varied from 3:1, 5:1 and 15:2.
Objective Compare 3:1, 5:1 and 15: 2 CV ratios using the two-thumb technique in relationship to depth of compressions, decay of compression depth over time, compression rates and breaths delivered.
Methods Thirty-two subjects, physicians and neonatal nurses, participated with compressions performed on a manikin. Evaluations included 2 min of compressions using 3:1, 5:1 and 15:2 CV ratios.
Results Compression depth was comparable between groups. By paired analysis per subject, the depth was only greater for 3:1 versus 15:2 (ie, 0.91±2.2 mm) (p=0.01) and greater for women than men. Comparing the initial and second minute of compressions, no decay in compression depth for 3:1 ratio was noted, however significant decay was observed for 5:1 and 15:2 ratios (p<0.05). The compression rates were least and ventilations breaths were highest for 3:1 as opposed to the other ratios (p<0.05).
Conclusions Providers using a 3:1 versus 15:2 achieve a greater depth of compressions over 2 min with a greater difference noted in women. More consistent compression depth over time was achieved with 3:1 as opposed to the other ratios. Thus, the 3:1 ratio is appropriate for newly born infants requiring resuscitation.
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What is known on the subject
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The most effective chest compression to ventilation ratio in newborns remains controversial. Recommendations include a 3:1 and 15:2 ratio.
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Experimental studies in piglets of asphyxia-induced cardiac arrest demonstrate that the addition of rescue breathing to compressions results in significantly improved outcomes than with compressions alone.
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Some manikin studies have demonstrated the ability to deliver more ventilations with a 3:1 ratio, and that lower ratios result in better quality cardiac compressions.
What this study adds
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Although compression depth is comparable between ratios, there is a wide range of inter-subject compression depth for each ratio.
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For each subject a greater depth was achieved when using a 3:1 versus 15:2 ratio. This difference was most evident in women.
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Decay in compression depth over time was less with a 3:1 as opposed to a 15:2 ratio.
Background
Chest compressions with or without epinephrine are an infrequent intervention during delivery room resuscitation in newborn infants, with an estimated occurrence of about 1 in 1000 term deliveries with a higher frequency in preterm infants.1 ,2 There are many facets to optimising compressions including the method of administration as well as the optimal ratio. We recently demonstrated in a manikin model the superiority of the two-thumb over the two finger technique for administration of compressions.3 However the most effective chest compression to ventilation ratio (C:V) in newborns remains controversial.
As a basic physiological principal, cardiac arrest or profound bradycardia in the neonate is invariably secondary to asphyxia, whereas in the adult it is secondary to ventricular fibrillation. During the asphyxial event, blood continues to flow to tissues and arterial and venous oxygen saturations decrease while carbon dioxide and lactate increases for many minutes. In addition, continued pulmonary blood flow before the cardiac arrest depletes the pulmonary oxygen reservoir. By contrast with ventricular fibrillation, effective cardiac output ceases immediately while oxygen levels in the blood remain relatively high for many minutes. Thus, the emphasis during neonatal cardiopulmonary resuscitation (CPR) is on ventilation with increased oxygenated blood to the heart, correction of hypercarbia and improvement in the acidotic state with less emphasis on supporting the relatively resilient heart.
Experimental studies in piglets of asphyxia-induced cardiac arrest demonstrate that the addition of rescue breathing to compressions results in significantly improved outcomes than when compressions are administered alone.4 ,5 Manikin studies show varied results when comparing ratios influenced by the manikin used, whether there was a single or dual rescuer, and whether mouth-to-mouth or bag/mask ventilation was provided. Some studies demonstrate the ability to deliver more ventilations with a 3:1 than with higher C:V ratios.6 ,7 Other studies suggest that lower ratios of 5:1 result in better quality cardiac compressions than higher ratios, but can be tiring to the rescuer.8 ,9 The current neonatal resuscitation programme (NRP) guidelines call for a 3:1 ratio, while the recommendation from the Paediatric Advanced Life Support is for a 15: 2 ratio. We hypothesised that the 3:1 as compared with the 5:1 and in particular the 15:2 ratio would be most advantageous to newborns because of the ability to deliver more consistent chest compressions and provide more ventilations over time. The study objective was to compare a 3:1, 5:1 and 15: 2 C:V ratio using the two-thumb (TT) technique in relationship to depth of compressions, decay of compression depth over time, compression rates and number of delivered breaths.
Methods
The Institutional Review Board of Weill Cornell Medical College approved this study and informed consent was obtained from each subject. Thirty-two NRP-trained providers consented and participated in the study. The subjects consisted of neonatal fellows (n=6), paediatric residents (n=8), neonatal nurses (n=11), nurse practitioners (n=5) and neonatal attending (n=2). There were 27 female and five male subjects. Each subject was briefly instructed on the proper application of the TT technique and was asked to perform a C:V ratio of 3:1, 5:1 and 15:2 for 2 min in random order. The subjects did not receive feedback regarding their performance during the study period. Following the study the subjects were asked questions as to which ratio was preferred and the reason for a specific preference.
Chest compressions were performed on a Laerdal Heart Code BLS manikin (Laerdal Corporation, Norway) that records compression depth in millimetres. The manikin approximates a 6-kg infant. The data were continuously recorded into a computer for subsequent analysis. Subjects were also video-recorded for analysis of proper finger placement and alignment.
The sample size was one of convenience. Data were analysed using t tests (unpaired and paired), using parametric and non-parametric measures where appropriate, analysis of variance for repeat measures and χ2 analysis. To assess variability between compressions, a coefficient of variation derived from the SD/mean and expressed as a percentage was calculated. The potential effect of decay in depth over time was examined comparing the first versus the second minute of compressions as well as the initial 25 versus the last 25 s of compressions. The latter was tested to assess progressive and maximum decay. All data are presented as a mean±SD.
Results
Compression depth was comparable between ratios, that is, 27±5.3 versus 26.7± 5.4 versus 26.2±6.1 mm for 3:1, 5:1 and 15:2, respectively (table 1). There was a wide range of inter-subject compression depth for each ratio: 3:1 (range 15.6 to 33.8 mm), 5:1 (range 13.6 to 33.8 mm) and 15:2 (range 13.7 to 34.9 mm) (figure 1). By paired analysis using each subject as his/her control, the depth was only greater for 3:1 versus 15:2: 0.91±2.2 mm (p=0.01) (table 2). This difference was significant for women, 1.00±2.37 (p=0.01), but not for men, 0.16±1.32 (p=0.16). There were no subject or sex differences between 3:1 versus 5:1 or 5:1 versus 15:2 ratios.
Compression depth for 3:1, 5:1 and 15:2 compression:ventilation ratios. Note that the mean depths for each ratio are comparable however within each ratio note the wide range of inter-subject depth.
Compression depth, coefficient of variation (COV), decay in compression depth comparing the initial versus the last 60 s and initial and last 25 s using a 3:1, 5:1 and 15: 2 ratio number of compressions and ventilator breaths/2 min with a 3:1, 5:1 and 15:2 ratio
Paired comparisons of depth and number of compressions and ventilator breaths/2 min with a 3:1, 5:1 and 15:2 ratio
Decay in compression depth over time was examined next (table 1). For the 3:1 ratio there was no difference between the first and second minutes of compression depth, 0.36±1.72 mm (p=0.11), but a significant difference was noted when comparing the first and last 25 s, that is, 0.54±1.64 (p=0.036). For the 5:1 ratio, there was a significant difference between the first and second minutes, 0.58±1.1 (p=0.02), as well when comparing the first and last 25 s of compression depth, 0.98±2.47 (p=0.01). For the 15:2 ratio a similar significant difference between the first and second minutes of compression depth, 0.86±1.88 (p=0.0009), as well when comparing the first and last 25 s of compression depth, 1.29±2.71 mm (p=0.007).
The compression rates per 2 min were different for 3:1 versus 5:1 versus 15:2, 194±36 versus 213±41 (p=0.02) and versus 225±41 beats per minutes (BPM) (p=0.001), but not for 5:1 versus 15:2 (table 1). Ventilation breaths were significantly greater for 3:1 versus 5:1 versus 15:2, 64±12 versus 42±8 versus 30±5. Four breaths/2 min, respectively (p=0.00005). By paired analysis compression and ventilation rates were different between the ratios (p<0.05) (table 2).
By self-assessment, 24/32 (75%) providers preferred the 3:1 ratio over the 5:1 or the 15:2 ratios; 8/32 (25%) preferred the 5:1 ratio or found it equivalent to the 3:1 ratio and no subject preferred the 15: 2 ratio. Specific issues related to the 15:2 included that this ratio was mentally more difficult (70%), more tiring (30%) and forced the provider to stay focused (30%).
Discussion
The findings in this manikin study demonstrate that providers using a 3:1 ratio as compared with a 15:2 ratio achieve a greater depth of compression over 2 min with a greater difference noted in female as compared with male subjects. No differences in compression depth were noted between 3:1 versus 5:1 or 5:1 versus 15:2 ratios. There was more consistent compression depth over the 2 min using the 3:1 method although there was decay with increasing time as providers achieved a greater depth during the first than during the last quarter of compressions. By contrast for the 5:1 and 15:2 ratios there was a significant decay in compression depth over time which was accentuated when comparing the first and last quarter of compressions. Importantly, there was a wide range of compression depth among providers of almost 20 mm irrespective of the compression ratios used. As anticipated, the compression rates were highest with the 15:2 ratio and least with the 3:1 ratio with the opposite noted for the ventilation breaths, that is, highest for the 3:1 ratio and lowest for the 15:2 ratio. By self-assessment the majority of providers preferred the 3:1 ratio over the other two ratios.
The use of a ratio that favours ventilation over compressions in the newborn period stems from the fact that the aetiology of asystole or profound bradycardia is invariably secondary to a respiratory rather than a cardiac cause. In this situation progressive bradycardia typically precedes the need for resuscitation with a markedly reduced cardiac output resulting in a further decrease in oxygen, a rise in carbon dioxide and lactate levels. By contrast with ventricular fibrillation or asystole typical of adult cardiac arrest, effective forward pumping of blood ceases and blood oxygen levels remain relatively high for many minutes. Thus, the focus in this situation is on chest compressions with infrequent ventilations. These physiological considerations are supported by experimental studies in newborn piglets subjected to asphyxia-precipitated cardiac arrest that demonstrate the value of additional rescue breathing to compressions which result in far better outcomes than when compressions are used alone.4 ,5 Furthermore, mathematical modelling studies suggest that using higher compression to ventilation ratios will result in underventilation of asphyxiated infants.10
The compression to ventilation ratio for neonatal resuscitation that will optimise coronary and cerebral perfusion while providing adequate ventilation of an asphyxiated newborn remains unknown. The longstanding recommendation of three compressions to one ventilation during neonatal cardiac compressions is consensus derived, based in part on the observation that the newly born infant breathes at about 40 per min with a heart rate of about 120 beats/min. However, in a recent piglet study comparing 3:1 versus 15:2 a comparable time to recovery of spontaneous circulation was demonstrated.11 Manikin studies show varied results when comparing ratios and are dependent on the manikin used, whether there was a single or dual rescuer, whether mouth-to-mouth or bag/mask ventilation was provided. Some studies demonstrate the ability to deliver more ventilations with a 3:1 compression to ventilation ratio which is consistent with the observations in this study.6 ,7 Lower ratios, 5:1, result in better quality cardiac compressions than higher ratios but can be tiring to the rescuer.8 ,9
Despite these experimental and manikin observations, intellectual debate continues as to the optimal ratio to administer during neonatal CPR. Some progress was made during the most recent International Liaison Committee on Resuscitation (ILCOR) consensus on science conference, where it was acknowledged that the cause of the arrest is critical when considering the most appropriate ratio.12 Thus, with an asphyxial aetiology, a ratio that facilitates more ventilations should be the goal, whereas with a cardiac arrest more compressions than ventilations should be administered.
The data in this report raise additional educational aspects to this debate. Thus, providers vary widely in the depth achieved during a 2-min paradigm, and some are unlikely to achieve the ‘desired one-third anterior posterior diameter depth’.13 Moreover, significant decay occurs over time particularly with a 5:1 and 15:2 ratio and for all ratios during the last phase of compressions. Since delivery room CPR is rare, reported in about 1 per 1000 deliveries, it becomes critically important for providers to become competent in achieving a consistent and appropriate depth over time irrespective of the ratio used. Otherwise, if the emphasis is on compressions during an asphyxia-related arrest, the administration of suboptimal compressions may further compromise recovery of spontaneous circulation.
There are several limitations to this study. First, we used a manikin model that is somewhat larger and potentially offers more resistance than a newborn, and may have accounted for some of the observed findings in this study. However, this potential factor should have been minimised as each subject served as his/her own control in a random manner. Second, this study did not evaluate the impact of the different ratios on the ability to provide effective ventilation breaths. Third, since all the participants were healthcare professionals and most from the neonatal area, it is entirely possible that this may have biased the subjective findings towards favouring a 3:1 ratio.
In conclusion providers achieve a greater compression depth with a 3:1 as opposed to a 15:2 ratio and demonstrate a significant and progressive decay in compression depth over time particularly with higher ratios. When considering the optimal compression to ventilation ratio in the neonatal period, consideration should also be given to the presumed aetiology of the arrest.
References
Footnotes
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Competing interests None.
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Funding Funded in part by a grant from the Academy of Pediatrics.
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Ethics approval Institutional Review Board of Weill Cornell Medical College.
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Provenance and peer review Not commissioned; externally peer reviewed.
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