Acta Pædiatrica ISSN 0803-5253
REVIEW ARTICLE
Exhaled carbon dioxide can be used to guide respiratory support in the delivery room Sylvia van Os1, Po-Yin Cheung1,2, Gerhard Pichler1,2,3, Khalid Aziz1,2, Megan O’Reilly1,2, Georg M. Schm€olzer ([email protected])1,2,3 1.Neonatal Research Unit, Alberta Health Services, Royal Alexandra Hospital, Edmonton, AB, Canada 2.Division of Neonatology, Department of Pediatrics, University of Alberta, Edmonton, AB, Canada 3.Division of Neonatology, Department of Pediatrics, Medical University Graz, Graz, Austria
Keywords Delivery room, Neonatal resuscitation, Newborn, Positive-pressure respiration, Respiratory function tests Correspondence €lzer, MD, PhD, Neonatal Research Georg M. Schmo Unit, Royal Alexandra Hospital, 10240 Kingsway Avenue NW, Edmonton T5H 3V9 AB, Canada. Tel: +1 780 735 5179 | Fax: +1 780 735 4072 | Email: [email protected]
ABSTRACT Respiratory support in the delivery room remains challenging. Assessing chest rise is imprecise, and mask leak and airway obstruction are common problems. We describe recordings of respiratory signals during delivery room resuscitations and discuss guidance on positive-pressure ventilation using respiratory parameters and exhaled carbon dioxide (ECO2) during neonatal resuscitations. Conclusion: Observing tidal volume and ECO2 waveforms adds objectivity to clinical assessments. ECO2 could help assess lung aeration and improve lung recruitment immediately after birth.
Received 30 January 2014; revised 4 March 2014; accepted 1 April 2014. DOI:10.1111/apa.12650
INTRODUCTION Approximately 10% of newborn infants require respiratory support at birth (1). An international consensus statement recommends positive-pressure ventilation (PPV) if infants fail to initiate spontaneous breathing (2). In the neonatal intensive care unit, arterial blood gases, transcutaneous partial oxygen saturation, end-tidal carbon dioxide and respiratory functions are used to guide effectiveness of respiratory support. However, these methods are not commonly applied in the delivery room. In the delivery room, PPV is usually guided by changes in heart rate. However, if heart rate does not increase, chest rise should be assessed to gauge PPV (2). Observational studies in the delivery room have shown that assessment of chest rise is imprecise; however, mannequin and observational delivery room studies demonstrated that assessment of chest rise is imprecise (3–5). Recently, oxygen saturation and heart rate have been considered important indirect indicators of adequate transition of newborn infants in the delivery room (6,7). This is supported by two observational studies demonstrating that heart rate is a very reliable indicator of adequate ventilation (8,9).
Furthermore, several observational studies and one randomised trial described how gas flow and tidal volume (VT) waves can be used to guide PPV during neonatal simulation (10), neonatal transport (11) and in the delivery room (12,13). However, parameters to directly assess the efficiency of ventilation are lacking. Hooper et al. (14) recently demonstrated that monitoring exhaled carbon dioxide (ECO2) during PPV identifies lung aeration. In addition, monitoring changes of ECO2 over time has the potential to guide mask PPV in the delivery room (14). Current neonatal resuscitation guidelines comment on the use of colorimetric CO2 detectors during mask PPV, which might help to identify airway obstruction (2). However, it remains unclear whether the use of CO2 detectors during mask PPV adds objectivity and has any additional benefit above clinical assessment alone (2).
Key notes
Abbreviations CO2, Carbon dioxide; ECO2, Exhaled carbon dioxide; ETT, Endotracheal tube; PEEP, Positive-end expiratory pressure. PIP, Peak inflation pressure; PPV, Positive-pressure ventilation; VT, Tidal volume.
796
Respiratory support in the delivery room remains challenging, because assessment of chest rise is imprecise and mask leak and airway obstruction are common problems. Our study found that observing tidal volume and exhaled carbon dioxide waveforms added objectivity to the clinical assessment. The findings indicate that exhaled carbon dioxide has the potential to assess lung aeration and improve lung recruitment immediately after birth.
©2014 Foundation Acta Pædiatrica. Published by John Wiley & Sons Ltd 2014 103, pp. 796–806
van Os et al.
The aim of this clinical practice review is to illustrate how monitoring ECO2 along with VT, gas flow and airway pressures has the potential to improve respiratory support during neonatal resuscitation. Observations and recordings of respiratory signals during delivery room resuscitation are described. In addition, limitations and pitfalls are discussed.
METHODS VT, gas flow, airway pressure and ECO2 monitor Gas flow, VT, airway pressure and ECO2 were measured with the NM3 Cardiopulmonary management system (NM3; Philips Healthcare, Electronics Ltd., Markham, ON, Canada) with a combined flow and ECO2 sensor placed between a ventilation device and facemask or endotracheal tube (ETT). The ventilation device used was a Panda Resuscitator (GE Healthcare, Laurel, MD, USA), which is
Exhaled carbon dioxide at birth
a continuous-flow, pressure-limited, T-piece device with a built-in manometer and a PEEP valve. The flow sensor used has a fixed orifice pneumotach to calculate. The inspiratory VT and expiratory VT passing through the sensor were automatically calculated by integrating the flow signal (15). An airway pressure monitoring line directly connected to the circuit measured and displayed the peak inflation pressure (PIP) and the positive-end expiratory pressure (PEEP). The monitor continuously displays pressure, flow and VT waves (Fig. 1) and numerical values for PIP or PEEP, inspiratory VT, expiratory VT and respiratory rate. In addition, the percentage of mask leak or leak around an ETT is calculated and displayed. ECO2 was measured using nondispersive infrared absorption technique. According to the manufacturer, the accuracy for the gas flow is 0.125 L/min and for ECO2 2 mmHg. Measurements were recorded from the monitor at 200 Hz and were stored
Figure 1 Mask PPV in a 28-week infant – No leak. At the start of the inflation, PIP increases from PEEP. This pressure change correlates with rapid increase in flow towards the infant and increase in VT. The CO2 waveform remains at zero. During expiration, the PIP returns to baseline, the flow moves away from the infant, and the VT curve returns to zero. Now ECO2 is displayed. The ECO2 waveform traditionally consists of five parts: (i) inflation, (ii) start of expiration when the exhaled air is a combination of dead space and alveolar gases and consists of a rapid S-shaped upswing on the tracing, (iii) exhalation of mostly CO2-rich gas from the alveoli (alveolar plateau), (iv) end-tidal point, which represents the maximum CO2 exhalation and (v) start of next inflation with a rapid decrease of CO2 to baseline or zero.
©2014 Foundation Acta Pædiatrica. Published by John Wiley & Sons Ltd 2014 103, pp. 796–806
797
Exhaled carbon dioxide at birth
van Os et al.
continuously in a multichannel system alpha-trace digital MM (B.E.S.T. Medical Systems, Vienna, Austria) for subsequent analysis. We aim to describe how ECO2 along with gas flow, VT and airway pressure can guide optimal mask ventilation, pitfalls during mask ventilation and lung aeration assessment. In addition, we describe how ECO2 can be used to guide mask ventilation and identify correct tube placement. The figures were obtained during respiratory support of preterm infants in the delivery room at The Royal Alexandra Hospital, Edmonton, a tertiary perinatal centre admitting more than 350 infants with a birthweight of
REVIEW ARTICLE
Exhaled carbon dioxide can be used to guide respiratory support in the delivery room Sylvia van Os1, Po-Yin Cheung1,2, Gerhard Pichler1,2,3, Khalid Aziz1,2, Megan O’Reilly1,2, Georg M. Schm€olzer ([email protected])1,2,3 1.Neonatal Research Unit, Alberta Health Services, Royal Alexandra Hospital, Edmonton, AB, Canada 2.Division of Neonatology, Department of Pediatrics, University of Alberta, Edmonton, AB, Canada 3.Division of Neonatology, Department of Pediatrics, Medical University Graz, Graz, Austria
Keywords Delivery room, Neonatal resuscitation, Newborn, Positive-pressure respiration, Respiratory function tests Correspondence €lzer, MD, PhD, Neonatal Research Georg M. Schmo Unit, Royal Alexandra Hospital, 10240 Kingsway Avenue NW, Edmonton T5H 3V9 AB, Canada. Tel: +1 780 735 5179 | Fax: +1 780 735 4072 | Email: [email protected]
ABSTRACT Respiratory support in the delivery room remains challenging. Assessing chest rise is imprecise, and mask leak and airway obstruction are common problems. We describe recordings of respiratory signals during delivery room resuscitations and discuss guidance on positive-pressure ventilation using respiratory parameters and exhaled carbon dioxide (ECO2) during neonatal resuscitations. Conclusion: Observing tidal volume and ECO2 waveforms adds objectivity to clinical assessments. ECO2 could help assess lung aeration and improve lung recruitment immediately after birth.
Received 30 January 2014; revised 4 March 2014; accepted 1 April 2014. DOI:10.1111/apa.12650
INTRODUCTION Approximately 10% of newborn infants require respiratory support at birth (1). An international consensus statement recommends positive-pressure ventilation (PPV) if infants fail to initiate spontaneous breathing (2). In the neonatal intensive care unit, arterial blood gases, transcutaneous partial oxygen saturation, end-tidal carbon dioxide and respiratory functions are used to guide effectiveness of respiratory support. However, these methods are not commonly applied in the delivery room. In the delivery room, PPV is usually guided by changes in heart rate. However, if heart rate does not increase, chest rise should be assessed to gauge PPV (2). Observational studies in the delivery room have shown that assessment of chest rise is imprecise; however, mannequin and observational delivery room studies demonstrated that assessment of chest rise is imprecise (3–5). Recently, oxygen saturation and heart rate have been considered important indirect indicators of adequate transition of newborn infants in the delivery room (6,7). This is supported by two observational studies demonstrating that heart rate is a very reliable indicator of adequate ventilation (8,9).
Furthermore, several observational studies and one randomised trial described how gas flow and tidal volume (VT) waves can be used to guide PPV during neonatal simulation (10), neonatal transport (11) and in the delivery room (12,13). However, parameters to directly assess the efficiency of ventilation are lacking. Hooper et al. (14) recently demonstrated that monitoring exhaled carbon dioxide (ECO2) during PPV identifies lung aeration. In addition, monitoring changes of ECO2 over time has the potential to guide mask PPV in the delivery room (14). Current neonatal resuscitation guidelines comment on the use of colorimetric CO2 detectors during mask PPV, which might help to identify airway obstruction (2). However, it remains unclear whether the use of CO2 detectors during mask PPV adds objectivity and has any additional benefit above clinical assessment alone (2).
Key notes
Abbreviations CO2, Carbon dioxide; ECO2, Exhaled carbon dioxide; ETT, Endotracheal tube; PEEP, Positive-end expiratory pressure. PIP, Peak inflation pressure; PPV, Positive-pressure ventilation; VT, Tidal volume.
796
Respiratory support in the delivery room remains challenging, because assessment of chest rise is imprecise and mask leak and airway obstruction are common problems. Our study found that observing tidal volume and exhaled carbon dioxide waveforms added objectivity to the clinical assessment. The findings indicate that exhaled carbon dioxide has the potential to assess lung aeration and improve lung recruitment immediately after birth.
©2014 Foundation Acta Pædiatrica. Published by John Wiley & Sons Ltd 2014 103, pp. 796–806
van Os et al.
The aim of this clinical practice review is to illustrate how monitoring ECO2 along with VT, gas flow and airway pressures has the potential to improve respiratory support during neonatal resuscitation. Observations and recordings of respiratory signals during delivery room resuscitation are described. In addition, limitations and pitfalls are discussed.
METHODS VT, gas flow, airway pressure and ECO2 monitor Gas flow, VT, airway pressure and ECO2 were measured with the NM3 Cardiopulmonary management system (NM3; Philips Healthcare, Electronics Ltd., Markham, ON, Canada) with a combined flow and ECO2 sensor placed between a ventilation device and facemask or endotracheal tube (ETT). The ventilation device used was a Panda Resuscitator (GE Healthcare, Laurel, MD, USA), which is
Exhaled carbon dioxide at birth
a continuous-flow, pressure-limited, T-piece device with a built-in manometer and a PEEP valve. The flow sensor used has a fixed orifice pneumotach to calculate. The inspiratory VT and expiratory VT passing through the sensor were automatically calculated by integrating the flow signal (15). An airway pressure monitoring line directly connected to the circuit measured and displayed the peak inflation pressure (PIP) and the positive-end expiratory pressure (PEEP). The monitor continuously displays pressure, flow and VT waves (Fig. 1) and numerical values for PIP or PEEP, inspiratory VT, expiratory VT and respiratory rate. In addition, the percentage of mask leak or leak around an ETT is calculated and displayed. ECO2 was measured using nondispersive infrared absorption technique. According to the manufacturer, the accuracy for the gas flow is 0.125 L/min and for ECO2 2 mmHg. Measurements were recorded from the monitor at 200 Hz and were stored
Figure 1 Mask PPV in a 28-week infant – No leak. At the start of the inflation, PIP increases from PEEP. This pressure change correlates with rapid increase in flow towards the infant and increase in VT. The CO2 waveform remains at zero. During expiration, the PIP returns to baseline, the flow moves away from the infant, and the VT curve returns to zero. Now ECO2 is displayed. The ECO2 waveform traditionally consists of five parts: (i) inflation, (ii) start of expiration when the exhaled air is a combination of dead space and alveolar gases and consists of a rapid S-shaped upswing on the tracing, (iii) exhalation of mostly CO2-rich gas from the alveoli (alveolar plateau), (iv) end-tidal point, which represents the maximum CO2 exhalation and (v) start of next inflation with a rapid decrease of CO2 to baseline or zero.
©2014 Foundation Acta Pædiatrica. Published by John Wiley & Sons Ltd 2014 103, pp. 796–806
797
Exhaled carbon dioxide at birth
van Os et al.
continuously in a multichannel system alpha-trace digital MM (B.E.S.T. Medical Systems, Vienna, Austria) for subsequent analysis. We aim to describe how ECO2 along with gas flow, VT and airway pressure can guide optimal mask ventilation, pitfalls during mask ventilation and lung aeration assessment. In addition, we describe how ECO2 can be used to guide mask ventilation and identify correct tube placement. The figures were obtained during respiratory support of preterm infants in the delivery room at The Royal Alexandra Hospital, Edmonton, a tertiary perinatal centre admitting more than 350 infants with a birthweight of
