7.3 CPR Quality Monitoring: ETCO2 & Diastolic BP

From Checklist CPR to Physiology-Directed CPR

Section 7.1 gave you the external metrics—rate, depth, recoil, interruptions. Section 7.3 adds what 2025 AHA/AAP PALS emphasizes when invasive monitoring is already in place (typically in-hospital, ICU, or OR arrests): use physiologic signals to judge whether those compressions are actually generating perfusion. The two highest-yield signals on the exam are arterial diastolic blood pressure and end-tidal CO2 (ETCO2).

Physiology-directed care does not mean inventing a new algorithm that ignores epinephrine timing or defibrillation. It means that if diastolic BP is low despite "looking busy" on the chest, you immediately improve compression quality, switch a fatigued compressor, correct leaning, shorten pauses, and search for reversible causes—rather than assuming the checklist numbers guarantee oxygen delivery to the heart.

Who has these monitors?

• Arterial line diastolic BP: available when an invasive arterial catheter is already present or rapidly usable during IHCA.
• ETCO2: available when an advanced airway is in place with continuous waveform capnography (preferred confirmation and monitoring tool).
• If neither is available (many OHCA and early ED cases), you still deliver high-quality BLS metrics from Section 7.1—monitoring targets do not delay starting CPR.

Diastolic Blood Pressure Goals During CPR (2025)

Coronary perfusion pressure during CPR is driven largely by the aortic diastolic pressure relative to right-atrial pressure. Higher achieved diastolic pressures during compressions associate with better rates of ROSC and favorable neurologic survival in pediatric data informing the 2025 update.

Numeric targets to memorize

When continuous invasive arterial blood pressure monitoring is present during CPR, it is reasonable to target:

These are hemodynamic goals of high-quality CPR, not alternative vital-sign definitions of ROSC. You still need organized rhythm and signs of return of circulation to declare ROSC. The numbers guide whether compressions are good enough right now.

What to do if diastolic BP is below target

1. Improve the compressor: depth, rate in band, full recoil, hand position, firm surface/backboard.
2. Rotate compressors if fatigue is likely—even before the 2-minute mark if quality collapses.
3. Eliminate leaning and unnecessary pauses (pulse checks, slow switches, prolonged procedures).
4. Avoid hyperventilation, which can lower venous return and arterial pressures.
5. Reassess advanced airway and circuit if ventilation problems coexist.
6. Treat reversible causes (H’s and T’s) that prevent effective output (Chapter 11)—for example tension pneumothorax, hypovolemia, tamponade.
7. Escalate per institutional arrest leadership (including consideration of advanced therapies such as ECPR in selected IHCA settings when protocols exist).

Exam trap: memorizing 25 and 30 but choosing "continue unchanged shallow compressions" when the arterial waveform shows diastolic pressures of 15 mm Hg. The correct action is to fix CPR quality using the waveform as feedback.

What diastolic BP during CPR is not

• Not a reason to withhold CPR if no arterial line exists.
• Not a post-ROSC blood pressure goal (post-arrest hemodynamic targets differ—Chapter 12).
• Not a substitute for rhythm checks and defibrillation of VF/pVT.

ETCO2: Quality Monitor, Not a Termination Threshold Alone

End-tidal carbon dioxide reflects pulmonary blood flow when ventilation is relatively stable. During CPR with an advanced airway:

• Very low ETCO2 often correlates with poor pulmonary blood flow (poor compressions, or other low-flow states).
• Improving compression quality may raise ETCO2.
• A sudden, sustained increase in ETCO2 can be an early marker of ROSC (cardiac output resumes and delivers CO2 to the lungs)—prompt a brief check for organized rhythm and pulse without a prolonged pause.

2025 critical limit on interpretation

Do not use a specific ETCO2 cutoff value alone as the sole criterion to terminate resuscitation in infants and children. ETCO2 can be influenced by:

• Endotracheal tube dislodgement or obstruction
• Severe ventilation–perfusion mismatch
• Massive pulmonary embolism
• Equipment failure or sampling line leaks
• Epinephrine and other interventions that change physiology
• Timing relative to pauses and ventilation changes

Termination of resuscitation decisions, when made at all, require a full clinical picture: reversible causes addressed, adequate CPR duration and quality, rhythm history, patient-specific context, and team/clinical judgment—not a single numeric ETCO2 threshold pulled from adult folklore.

Practical ETCO2 use during PALS care

ETCO2 also remains the preferred continuous method to confirm advanced airway placement when available—separate from its CPR-quality role.

CPR Feedback Devices and Quality Improvement

CPR feedback devices (accelerometers, defibrillator-based coaching, depth/rate/recoil displays, metronomes) may help rescuers hit metric targets. 2025-oriented teaching frames them as tools that work best inside training programs and system-level quality improvement (QI)—debriefing, mock codes, and continuous measurement—not as magic sensors that replace team leadership.

How to use feedback well

• Follow real-time prompts for rate and depth while still watching the patient and monitors.
• Combine device feedback with arterial DBP and ETCO2 when those exist.
• After the arrest, debrief: What was CCF? When did diastolic BP fall? Who needed earlier compressor relief?
• Do not stop compressions for long periods to "set up" a feedback puck if basic CPR is already due—apply devices in parallel.

Putting 7.1–7.3 together on a megacode

1. Recognize arrest → CPR ≤10 s.
2. Metrics: 100–120/min, correct depth, full recoil, pauses <10 s, correct infant/child technique.
3. Ratios: 30:2 single, 15:2 two-rescuer; then continuous compressions + breath every 2–3 s with advanced airway.
4. Early AED/defibrillator with pediatric attenuation when available.
5. If arterial line: drive diastolic BP to ≥25 (infant) or ≥30 (child ≥1 yr).
6. If ETCO2 available: use trends for quality and ROSC clues; never quit solely on a low number.
7. Feedback devices and closed-loop communication keep the team honest.

Clinical scenario (synthesis)

A 2-year-old has an in-hospital arrest with an arterial line and a newly placed tracheal tube. Compressions look "fast," but arterial diastolic pressure is 18 mm Hg and ETCO2 is 8 mm Hg. You coach: deeper compressions to one-third AP depth (~5 cm), full recoil, rate into 100–120, backboard in place, switch compressor, stop hyperventilation. Diastolic BP rises to 32 mm Hg and ETCO2 climbs into the 20s. Two minutes later ETCO2 jumps to the mid-40s with an organized rhythm—brief pulse check confirms ROSC. You would not have stopped the code earlier merely because ETCO2 was once 8 mm Hg; you used that value to improve CPR, not to declare futility.

Master diastolic targets, ETCO2 interpretation limits, and feedback-device QI use, and you complete the BLS/CPR quality triad that underpins every PALS arrest algorithm.