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Abstract
Background Current neonatal guidelines endorse both the two-thumb and the two-finger techniques for performing chest compressions. It remains unclear whether one method is superior to the other in achieving consistent depth.
Objective To compare the compression depth, variability, rate and finger placement of the two-thumb and two-finger techniques using a compression to ventilation (CV) ratio of 3:1.
Methods 25 subjects (physicians and neonatal nurses) participated with compressions performed on a manikin. Subjects were video recorded. Evaluations included continuous compression administered for 60 s, followed by 2 min of compressions using a 3:1 CV ratio for each of the two techniques.
Results Depth during 60 s of uninterrupted compressions was greater for the two-thumb than the two-finger technique (27.2±5.7 vs 22.1±4.6 mm; p=0.0008), variability was less (6.7%±3.2% vs 9.0%±2.8%; p=0.002) and rate was comparable (118±22 vs 116±24 compressions/min). With a 3:1 CV ratio, depth was greater for the two-thumb compared to the two-finger method (29±5.4 vs 23.7±5.8 mm; p=0.0009), variability was less (6.1%±2.9% vs 9.8%±3.1%; p=0.00002) and rate was comparable (192±26 vs 197±31 compressions/2 min). Correct positioning was accomplished more often with the two-thumb than the two-finger technique (21/25 vs 3/25; p=0.0005).
Conclusions The two-thumb technique is superior to the two-finger technique, achieving greater depth and less variability with each compression. The two-finger technique was incorrectly applied in most cases and deviations in technique may have contributed to the significant differences in depth.
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Background
Chest compressions are an infrequent intervention during delivery room resuscitation in newborn infants, and are estimated to occur in approximately 1 in 1000 term deliveries, with a higher frequency in preterm infants.1 Chest compressions achieve only a fraction of native perfusion even under optimal conditions, and so optimising compressions could be critical in improving outcomes.2 3 Because they are infrequently required, acquiring and retaining the skills to competently perform chest compressions remains a challenge. Moreover, the most effective method of administration to achieve adequate cardiac output remains unclear. The neonatal resuscitation program (NRP) in the USA currently endorses two methods for applying chest compressions, namely a two-thumb and a two-finger method.4 It remains unclear whether one method is superior to the other during neonatal cardiac compressions in terms of the depth and/or consistency of force applied, both of which are likely to modulate the effectiveness of compressions.
What is already known on this topic
▶ Animal and manikin studies have demonstrated more effective compressions with the two-thumb than the two-finger method using ratios other than 3:1.
▶ These studies utilised ratios that were different from the 3:1 ratio used in this study.
What this study adds
▶ This study shows that the two-thumb technique achieves greater depth, less variability between compressions, better positioning and a better technique (all novel findings) compared to the two-finger method.
▶ The two-thumb technique achieves greater depth and less variability between compressions compared to the two-finger method using a ratio of 3:1.
Previous experimental studies in a swine model comparing the two-thumb with the two-finger compression technique suggest that the former may be superior to the two-finger method through achieving a higher mean arterial pressure, systolic blood pressure and diastolic blood pressure.5 6 These experimental studies were performed using a swine model and a 5:1 compression to ventilation (CV) ratio. However, there are no studies comparing the two-thumb and two-finger techniques using the current recommended ratio of three compressions to one ventilation. We hypothesised that the two-thumb technique would be superior to the two-finger method in terms of achieving a greater depth and less variability with each compression. Thus, the current study was designed to compare the depth of compression, compression-to-compression variability, rate and finger placement and alignment between the two-thumb and two-finger techniques during uninterrupted cardiac compressions while delivering a 3:1 CV ratio.
Methods
The Institutional Review Board of Weill Cornell Medical College approved this study and informed consent was obtained from each subject. Twenty-five NRP trained providers consented and participated in the study. The subjects consisted of neonatal attending (n=2), neonatal fellow (n=6), paediatric resident (n=12), neonatal nurse practitioner (n=2) and neonatal nurses (n=3). Each subject was briefly instructed on the proper application of the two-thumb and the two-finger compression techniques regarding positioning, depth and frequency. The study had two components. First, the subjects were asked to perform 60 s of continuous compressions using each method. Second, the subjects were asked to perform 2 min of compressions using a 3:1 CV ratio, again using each method. Instead of providing a breath, the investigator called out “breath” following the three compressions. The subjects did not receive feedback regarding their performance during the study period. The subjects were randomised to begin with either the two-thumb or the two-finger method. Chest compressions were performed on a Laerdal HeartCode BLS manikin (Laerdal, Stavanger, 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 study was designed to evaluate the data after 25 subjectshad been recorded to determine a projected sample size. Data were analysed using t tests (unpaired and paired) and χ2 analysis. To assess variability between compressions, a coefficient of variation derived from the SD/mean and expressed as a percentage was calculated. All data are presented as mean±SD.
Results
Continuous chest compressions for 60 s
During the 60 s of continuous chest compressions, depth was greater for the two-thumb than the two-finger technique (27.2±5.7 vs 22.1±4.6 mm; p=0.0008). The coefficient of variability between compressions was less (6.7%±3.2% vs 9%±2.8%; p=0.002) (table 1). When the data were analysed using each subject as his/her own control, 22 (88%) of the 25 subjects achieved a greater mean depth of 5±4.9 mm (p=0.00005) and 18 of the 25 subjects had less variability between compressions (p=0.002) with the two-thumb as compared to the two-finger technique. The number of compressions performed during the 60 s was comparable between the two methods with 118±22 versus 116±24 compressions/min for the two-thumb compared to the two-finger method.
Depth of compressions and coefficient of variation (COV) with continuous compressions for 60 s using the two-thumb versus the two-finger technique
Chest compressions using a 3:1 ratio
The depth when using the 3:1 ratio was similarly greater (29±5.4 vs 23.7±5.8 mm; p=0.0009) and the coefficient of variation between compressions was less (6.1%±2.9% vs 9.8%±3.1%; p=0.00002) for the two-thumb as compared to the two-finger technique (table 2). When the data were analysed using each subject as his/her own control, 24 (96%) of the 25 subjects achieved both a greater depth as well as less variability with the two-thumb technique (p=0.00005). The number of compressions over the 2 min was comparable between the two groups (192±26 vs 197±31 compression/2 min for the two-thumb and two-finger methods, respectively; NS).
Depth of compressions and coefficient of variation (COV) utilising a 3:1 compression to ventilation ratio for 2 min using the two-thumb compared with the two-finger technique
Proper application
For the two-thumb technique, 21 out of 25 subjects had the proper technique compared to only three out of 25 subjects for the two-finger technique (p=0.0005). The two most common failures were incorrect application of the fingers such that subjects applied the pads of fingers instead of the tips, and incorrect positioning of fingers such that they were not in the centre of the chest. Not a single provider supported the back when using the two-finger technique.
Discussion
The data in this report indicate that when a newborn manikin is used, cardiac compressions using the two-thumb method are superior to the two-finger technique in achieving a greater depth as well as decreased variability with each compression using the currently recommended ratio of 3:1. Moreover, providers correctly positioned and applied the fingers using the two-thumb method significantly more often than with the two-finger technique.
The initial report demonstrating the value of closed chest compressions for asystolic or severely bradycardic infants suggested that the two-finger method was effective in achieving an adequate systolic blood pressure.7 The authors reported on five cases, one of whom had an intra-arterial catheter in place facilitating the measurements of blood pressure, and demonstrated that a systolic blood pressure >70 mm Hg was achieved using the two-finger method. A single-thumb method was also utilised and only achieved a mean blood pressure of 40 mm Hg. Regardless of the method, a diastolic blood pressure of 20 mm Hg was achieved. Importantly, an adequate diastolic blood pressure is critical to achieving adequate coronary perfusion during cardiopulmonary resuscitation (CPR). Subsequently, two experimental studies using an infant swine model with adult and paediatric resuscitation paradigms compared the two-thumb to the two-finger method.5 6 Both studies suggest that the two-thumb technique is superior to the two-finger method by demonstrating that the former with lateral chest wall compression provided significantly higher arterial pressures than did the two-finger method. Limitations of the first study included non-standardised compression forces and short 1 min intervals for evaluation of compressions.5 The second study utilised a standardised sternal compression force in paralysed and mechanically ventilated swine. The two-thumb method produced significantly higher systolic blood pressures. However, the diastolic blood pressures were not significantly different.6 These data suggest that in this swine model of infant CPR, two-thumb chest compression is an easier and more effective method.8 The same investigators subsequently compared the two techniques over a longer 10 min compression interval using a modified manikin with a fixed volume arterial system attached to a neonatal monitor via an arterial pressure transducer. Using a 5:1 CV ratio, the two-thumb method produced higher mean, systolic and diastolic arterial blood pressures compared to the two-finger method.8 A single case report of two newborns describes improved mean and systolic arterial blood pressure using a 5:1 chest CV ratio with the two-thumb compared to the two-finger technique.9
The data in this study are consistent with these observations, indicating that the two-thumb method achieves a greater depth and less variability with each compression as compared to the two-finger technique even when using the neonatal paradigm of a 3:1 ratio. The greater depth achieved with the two-thumb technique is also consistent with a recent manikin study of infant cardiac compressions.10 Since providers more often applied and positioned the fingers appropriately with the two-thumb as compared to the two-finger technique, it is possible that this contributed to the greater depth generated by the two-thumb technique. Although the mean rate of compressions was comparable with the predicted rate for both continuous compressions (120 compressions for 60 s) as well as for compressions over 2 min (180 compressions), and did not differ by method, there was a wide variation in rates for both techniques. This factor may also influence the effectiveness of compressions.
There are limitations to the study. First, we used a manikin model that is somewhat larger and potentially offers more resistance than a term neonate, which may have accounted for some of the differences noted. However, this potential factor should have been minimised as each subject served as his/her own control in a random manner. Second, the sample size is relatively small. However, the almost uniform greater depth and less variability with the two-thumb technique resulted in our stopping the study after examining the data once 25 subjects had been recorded, as per the original design. Third, the duration of time for administering compressions was relatively short.
In conclusion, the two-thumb technique was almost uniformly associated with greater depth, less variability and more correct positioning, as compared to the two-finger technique during cardiac compressions in a neonatal manikin model. These observations suggest a greater likelihood of enhanced cardiac output in neonates with each compression using the two-thumb technique. Thus, the two-thumb method should be the preferred technique for initiating and maintaining chest compressions in neonates.
Footnotes
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Funding This study was funded by a grant from the American Academy of Pediatrics, Elk Grove, Illinois, USA.
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Competing interests None.
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Ethics approval This study was conducted with the approval of the Institutional Review Board of Weill Cornell Medical College.
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Provenance and peer review Not commissioned; externally peer reviewed.