End-Tidal CO₂ Measurement in Pediatric Resuscitation: Target Values

Capnography is considered one of the most important parameters for guiding cardiopulmonary resuscitation – and not just in adults. In the pediatric setting, end-tidal CO₂ measurement (ETCO₂) provides critical information about the quality of chest compressions, the effectiveness of ventilation, the likelihood of return of spontaneous circulation (ROSC), and prognosis. However, target values and interpretation considerations in children differ substantially from those in adults in several respects. Anyone leading pediatric resuscitations must understand these differences to optimally use capnography as a real-time feedback tool.

Physiological Fundamentals of ETCO₂ Measurement in Children

End-tidal CO₂ measured at the end of expiration reflects the alveolar CO₂ concentration, which in turn depends on the interplay of three factors:

• CO₂ production: Tissue metabolism produces CO₂ as the end product of aerobic energy generation.
• CO₂ transport: Cardiac output transports CO₂ via the venous system to the lungs.
• CO₂ elimination: Alveolar ventilation eliminates CO₂ through exhaled air.

During cardiac arrest, CO₂ transport to the lungs collapses. ETCO₂ values initially drop drastically. Only through effective chest compressions is a minimal cardiac output generated that transports CO₂ to the lungs – and it is precisely this transported CO₂ that becomes measurable by capnography. This makes ETCO₂ under resuscitation conditions a surrogate parameter for pulmonary blood flow and thus for the effectiveness of chest compressions.

Characteristics of Pediatric Physiology

Children differ from adults in several ways that affect ETCO₂ interpretation:

• Higher basal metabolic rate: Children produce more CO₂ per kilogram of body weight than adults. This can lead to relatively higher ETCO₂ values with effective compressions compared to equivalent compression quality in adults.
• Higher respiratory rate and lower tidal volume: The shorter expiratory time can affect the accuracy of ETCO₂ measurement, especially with sidestream capnographs that have longer response times.
• Greater proportion of dead space ventilation: With small airway adapters and supraglottic airway devices, dilution of exhaled air can lead to falsely low ETCO₂ values.
• Most common cause of cardiac arrest: Unlike in adults, pediatric cardiac arrest is predominantly of respiratory or hypoxic origin – not a primary cardiac event. This has far-reaching consequences for ETCO₂ interpretation.

Target Values During Pediatric Resuscitation

The AHA guidelines recommend continuous capnography as standard monitoring during pediatric resuscitation – particularly after endotracheal intubation, but also when using supraglottic airway devices and even during bag-mask ventilation with appropriate adapters.

ETCO₂ as a Marker of CPR Quality

The key target value you should aim for during pediatric resuscitation:

• ETCO₂ ≥ 10–15 mmHg (equivalent to ≥ 1.3–2.0 kPa): This indicates adequate pulmonary blood flow from effective chest compressions.
• ETCO₂ < 10 mmHg over a prolonged period: This is an alarm signal for inadequate compressions or other correctable causes and should immediately prompt a review and optimization of CPR quality.

Important to note: The commonly cited threshold of 10 mmHg is derived primarily from adult data. In children – especially infants – absolute values may be lower without necessarily indicating poorer compression quality. Reasons include:

• The smaller absolute cardiac output during CPR
• The lesser thoracic muscle mass
• The higher chest wall compliance, which paradoxically can lead to less effective pressure transmission to the great vessels

Therefore, in children, the trend of the ETCO₂ curve is more important than the absolute single value.

Trend Analysis Rather Than Single-Value Fixation

The most clinically relevant information provided by capnography during pediatric resuscitation comes from trend monitoring:

• Rising ETCO₂ trend with consistent ventilation: Indicates improved perfusion – either from optimized compressions or as an early sign of ROSC.
• Falling ETCO₂ trend: Deterioration in perfusion, compressor fatigue, compression interruptions, or increasing airway obstruction.
• Sudden ETCO₂ drop to near zero: Tube displacement, obstruction, or disconnection – immediate airway check required.
• Sudden, sustained ETCO₂ rise to > 30–40 mmHg: Highly suspicious for ROSC.

ETCO₂ as a ROSC Predictor in Children

One of the most valuable aspects of capnography during resuscitation is the early detection of ROSC – often before a pulse is palpable or organized electrical activity is visible on the monitor.

Recognizing the ROSC Signal

In children, ROSC typically manifests as:

• An abrupt, sustained rise in ETCO₂ to values above 30–40 mmHg
• This rise frequently occurs 15–30 seconds before a clinically palpable pulse
• The rise occurs because the restored cardiac output rapidly transports the CO₂ load accumulated in tissues to the lungs

This "ETCO₂ surge" is a reliable sign and should prompt you to look particularly carefully for an organized rhythm and clinical signs of circulation during the next scheduled rhythm analysis. However: Do not interrupt compressions solely because of an ETCO₂ rise. Wait for the next regular analysis point in the algorithm, unless definitive clinical signs (purposeful movements, coughing, spontaneous breathing) confirm ROSC.

Prognostic Significance

The prognostic value of ETCO₂ values during pediatric resuscitation must be viewed with nuance:

• In adults, a persistently low ETCO₂ < 10 mmHg after 20 minutes of high-quality CPR is considered a negative prognostic factor that can be factored into the decision to terminate resuscitation.
• In children, the evidence is less robust. The AHA guidelines explicitly recommend that ETCO₂ values alone should not be used as a criterion for terminating pediatric resuscitation. Reasons include:
  • Smaller study populations
  • More heterogeneous etiologies (drowning, airway obstruction, congenital heart defects)
  • The observation that children can achieve neurologically favorable outcomes even after prolonged CPR with initially low ETCO₂ values

ETCO₂ can therefore supplement prognostic assessment but should never be the sole determining factor in children.

Practical Application: ETCO₂-Guided CPR in Children

Airway Management and Measurement Accuracy

The accuracy of ETCO₂ measurement depends critically on the type of airway management:

Airway Device	ETCO₂ Accuracy	Considerations
Endotracheal tube	Highest accuracy	Gold standard; direct sensor connection
Supraglottic airway device	Good to very good	Leaks can lead to falsely low values
Bag-mask ventilation	Limited	Leakage common; sidestream capnography with nasal cannula adapter possible

In non-intubated children, you should interpret ETCO₂ values with caution. Leaks around the mask or supraglottic airway device dilute the expiratory gas and lead to falsely low readings. An apparently low ETCO₂ value during mask ventilation therefore does not necessarily indicate inadequate compressions.

Systematically Identifying Sources of Error

Before assessing CPR quality or prognosis based on ETCO₂ values, systematically rule out the following sources of error:

1. Tube/airway problems: Displacement, obstruction, esophageal misplacement
2. Leaks: Check cuff pressure, verify mask seal
3. Hyperventilation: An excessively high ventilation rate – a classic error in pediatric resuscitations – leads to increased CO₂ elimination and can paradoxically lower the ETCO₂ value even though compression quality is adequate
4. Medication effects: Epinephrine causes temporary redistribution of blood flow through peripheral vasoconstriction and can lead to a transient ETCO₂ drop of 2–5 mmHg – this is expected and not a sign of poor CPR
5. Sodium bicarbonate administration: Rapidly releases CO₂ and can cause a brief ETCO₂ rise that must not be confused with ROSC

Ventilation Rate and ETCO₂

Hyperventilation is one of the most common and harmful errors in pediatric resuscitation. Capnography can serve as a corrective tool here:

• Target ventilation rate with a secured airway: One breath every 2–3 seconds (approximately 20–30/min in infants, 15–20/min in older children), depending on age
• ETCO₂-guided adjustment: If ETCO₂ is conspicuously low despite adequate compressions, first check whether you are ventilating too fast
• Capnography waveform: A regular, non-choppy waveform with a distinct plateau indicates adequate expiratory time

Algorithm: ETCO₂ Interpretation During Pediatric CPR

The following systematic approach helps you correctly interpret ETCO₂ values during pediatric resuscitation:

Step 1 – Assess the waveform

• Is a regular capnography curve with a plateau visible?
• If no waveform: Check the airway (tube position, connection check, rule out obstruction)

Step 2 – Contextualize the absolute value

• ETCO₂ ≥ 10–15 mmHg: CPR quality likely adequate → maintain current approach
• ETCO₂ < 10 mmHg: Rule out sources of error → then optimize compression quality (depth, rate, complete recoil, minimizing interruptions)

Step 3 – Monitor the trend

• Rising trend: Positive sign → continue current strategy
• Falling trend: Switch compressors, check airway, re-evaluate reversible causes (4 H's and HITS)

Step 4 – Recognize an abrupt rise

• Sudden ETCO₂ rise > 30–40 mmHg: Suspected ROSC → perform targeted pulse check at next rhythm analysis
• Abrupt rise after sodium bicarbonate administration: Not ROSC → wait to see whether the rise persists

Step 5 – After epinephrine administration

• Transient ETCO₂ drop of 2–5 mmHg: Expected → no change in CPR strategy
• Absence of ETCO₂ drop after epinephrine may indicate a non-functioning access (for IV/IO administration: check placement and patency)

Common Pitfalls of Capnography in Children

The following situations regularly lead to misinterpretation in practice:

• Hypothermia (e.g., after drowning): Reduced metabolism leads to lower CO₂ production. ETCO₂ values may be low despite adequate compressions. This must not lead to premature termination of resuscitation.
• Asthma/bronchospasm: Air trapping can lead to paradoxically elevated ETCO₂ values that do not necessarily reflect better perfusion. At the same time, a "shark fin" pattern on capnography may indicate obstruction.
• Congenital heart defects with right-to-left shunt: A portion of venous blood bypasses the lungs. ETCO₂ values may be systematically lower than in children with normal cardiac anatomy.
• Pulmonary hypertension: Reduced pulmonary blood flow lowers ETCO₂ independently of compression quality.
• Tension pneumothorax: Causes an abrupt ETCO₂ drop due to diminished venous return and reduced gas exchange surface area – one of the reversible causes that must be treated immediately.

Integration into the PALS Algorithm

Capnography integrates seamlessly into the PALS algorithm and complements the standard 2-minute cycles:

1. Before the first cycle: Connect capnography, document the baseline value
2. During each cycle: Continuously monitor the ETCO₂ trend, assess the waveform
3. At each rhythm check: Actively incorporate the ETCO₂ value into the team briefing ("ETCO₂ currently at 18, rising trend")
4. After epinephrine administration: Anticipate and communicate a short-term ETCO₂ drop
5. When ROSC is suspected: Regard the ETCO₂ rise as the earliest sign, but only pause compressions after rhythm analysis and pulse check

Communicating ETCO₂ values within the team is essential. Ideally, designate one person (often the person managing the airway) to regularly announce ETCO₂ values and trends aloud.

Summary of Key Points

• ETCO₂ is the best available real-time marker for compression quality during CPR in children.
• Target value ≥ 10–15 mmHg, with the trend being more important than any single value.
• An abrupt, sustained ETCO₂ rise to > 30–40 mmHg is the earliest indicator of ROSC.
• Sources of error (leaks, hyperventilation, medication effects) must be systematically ruled out before questioning CPR quality.
• ETCO₂ alone must not be used as a criterion for terminating resuscitation in children.
• Exercise particular caution with hypothermia, congenital heart defects, and obstructive airway diseases.

Practical Training

Interpreting capnography during resuscitation requires not only theoretical knowledge but above all practical experience – especially recognizing trends, rapid troubleshooting of unexpected values, and integration into team communication. In the PALS course from Simulation Tirol, you train exactly these scenarios using realistic simulations with real capnography monitoring and receive structured feedback on correct interpretation and clinical decision-making in pediatric emergencies.