Abstract
Chest compression (CC) is an infrequent event (0.08%) in newborns delivered at near-term and term gestation, and occurs at a higher frequency (10%) in preterm deliveries. In addition, outcome studies of deliveries requiring resuscitation or chest compression have reported high rates of mortality and neurodevelopmental impairment in surviving children. A respiratory function monitor (RFM) can help guide a resuscitator during cardiopulmonary resuscitation (CPR) in a neonate and help assess the quality and efficacy of chest compression. Utilizing a non-invasive respiratory function monitor during chest compression may decrease high mortality rates in addition to having many distinct advantages, which will benefit both the newborn and the resuscitators. There are several different ways that a respiratory function monitor can assist a resuscitator during chest compression; these include confirming and ensuring adequate lung ventilation, analyzing the efficacy and quality of chest compression and exhaled CO2 monitoring.
Keywords
- infants
- newborn
- delivery room
- neonatal resuscitation
- chest compression
1. Introduction
Fortunately, the need for chest compression (CC) or medications in the delivery room is rare. Only about 0.1% of term infants receive these interventions, resulting in approximately 1 million newborn deaths annually worldwide. In addition, chest compression or medications is more frequent in the preterm population (~15%) due to birth asphyxia [1, 2]. Fortunately, the majority of newborn infants successfully make the transition from fetal to neonatal life without any help [3]. An estimated 10% of newborns need help to establish effective ventilation (e.g., positive pressure ventilation, PPV), which remains the most critical step of neonatal resuscitation [3]. However, clinicians struggle to deliver an adequate tidal volume (
2. Respiratory function monitor
2.1. VT, gas flow, airway pressure, and exhaled CO2 monitor
Gas flow,
3. Mask leak
Mask ventilation studies in the delivery room have reported variable mask leak during positive pressure ventilation [4], which can be significantly decreased if mask leak is displayed on an RFM [13]. Using a manikin, Binder-Heschl et al. reported that mask leak significantly increased from 15% during positive pressure ventilation to 32% after chest compression was started [6]. This is further supported by a study by Solevåg et al. who reported that tidal volume delivery is significantly decreased using continuous chest compression with non-synchronized ventilation compared to the current 3:1 cardiopulmonary resuscitation (CPR) [7]. However, when a resuscitation used an RFM to asses mask leak, it was significantly reduced [6]. Unfortunately, the data in newborn infants are sparse and limited to a case report by Li et al. [12]. During chest compression, mask leak was 100% and did not result in an increase in heart rate, suggesting that adequate tidal volume was not delivered (Figure 1) [12].
4. Tidal volume
The purpose of inflations during chest compression is to deliver an adequate tidal volume to facilitate gas exchange [3]. A manikin study reported that tidal volume increases once chest compression was started compared to mask ventilation alone [7]. Interestingly, a further manikin study examined different auditory prompts during simulated neonatal cardiopulmonary resuscitation and reported higher tidal volumes in all groups compared to baseline [15]. These studies suggest a change in tidal volume once chest compressions are initiated. An increase or decrease in tidal volume could cause lung derecruitment, which could hamper oxygenation and therefore return of spontaneous circulation (ROSV) [12]. In a porcine model of neonatal resuscitation, Li et al. recently described that using the current recommendation of 3:1 chest compression to ventilation ratio (Figure 2) [3], lung derecruitment occurs [8]. The study further compared continuous chest compressions with asynchronous ventilations and found similar results [8], however, when chest compression superimposed by sustained inflation (CC + SI) (Figure 3) [16] improved tidal volume delivery and continuous lung recruitment was observed, potentially leading to better alveolar oxygen delivery and lung aeration.
5. Exhaled carbon dioxide (ECO2)
There is increasing evidence that continuous monitoring of exhaled carbon dioxide (ECO2) can predict rise of heart rate during neonatal transition [17], monitor lung aeration at birth [11, 18–20], and predict return of spontaneous circulation during neonatal cardiopulmonary resuscitation (Figure 4) [21]. Blank et al. used a Pedi-Cap during mask positive pressure ventilation and reported a significant increase in heart rate once the Pedi-Cap turned yellow [17]. Similar results have been described in animal models and a further delivery room study [18]. During neonatal cardiopulmonary resuscitation ECO2 is a reliable parameter to examine return of spontaneous circulation. Chalak et al. reported that an ECO2 of 14 mmHg was the most reliable indicator for return of spontaneous circulation with 92% sensitivity and 81% specificity [21]. This study suggests that monitoring ECO2 during cardiopulmonary resuscitation would allow uninterrupted chest compression and potentially could be an indirect indicator of the CC effectiveness. This has been further supported by a recent animal study by Li et al., suggesting that either ECO2, rate of elimination of CO2 (VCO2) or partial pressure of exhaled (PeCO2) could be used to monitor the return of spontaneous circulation [12]. A recent case report of neonatal cardiopulmonary resuscitation in an extremely preterm infant supports this hypothesis where a significant increase in ECO2 preceded an increase in heart rate and return of spontaneous circulation [12]. ECO2 monitoring is a non-invasive tool that can be used to predict the return of spontaneous circulation during cardiopulmonary resuscitation.
5.1. Partial pressure of exhaled (PeCO2) and rate of elimination of CO2 (VCO2)
A recent animal study described VCO2 and PECO2 values as a clinical indicator during chest compression to achieve the return of spontaneous circulation. VCO2, or the volume of expired CO2, reflects changes in both ventilation and perfusion, and therefore ventilation/perfusion (V/Q) matching [22]. Palme-Kilander et al. reported that low VCO2 values could be due to residual lung fluid, very low tone, or deficient perfusion of the lungs [23]. A recent study in preterm infants reported that higher VCO2 levels were associated with lung aeration and successful establishment of functional residual capacity [19]. During chest compression, increasing VCO2 values reflects adequate ventilation, perfusion, and lung aeration [22]. Thus, VCO2 potentially provides valuable information during neonatal resuscitation.
PeCO2 is a continuous, non-invasive measurement. Since the physiological dead space/tidal volume (
6. Conclusion
Using a respiratory function monitor to assess mask leak and tidal volume delivery during neonatal cardiopulmonary resuscitation can help improve mask ventilation. In addition, using exhaled carbon dioxide can predict return of spontaneous circulation during neonatal cardiopulmonary resuscitation.
Abbreviations
CPR cardio pulmonary resuscitation
CC chest compression
CC+SI continuous chest compressions with sustained inflations
ECO2 exhaled carbon dioxide
PPV positive pressure ventilation
ROSC return of spontaneous circulation
VT tidal volume
VD/VT physiological dead space/tidal volume
Acknowledgments
MOR is supported by a Molly Towell Perinatal Research Foundation Fellowship. ALS is supported by the Canadian Institute of Health Research (MOP299116) and the South-Eastern Norway Regional Health Authority. GMS is a recipient of the Heart and Stroke Foundation/University of Alberta Professorship of Neonatal Resuscitation and Heart and Stroke Foundation Canada Research Scholar.
Conflict of Interest: None declared by the authors.
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