By Abdolghader Pakniyat (Reviewed by Dr. Sabrina Berdouk)

Educational content only. Follow your local AHA/ERC guidelines and institutional protocols. POCUS is operator-dependent.

This is Part 1 of a series on POCUS in CPR and critical care.

POCUS can help during cardiac arrest.
It can also harm patients if it prolongs pauses in chest compressions.

A high-quality ultrasound image is not a success if it costs no-flow time. When compressions stop, coronary perfusion pressure falls rapidly. The next image must justify its place in resuscitation.

AHA 2025 and ERC-based 2025 guidance share the same safety principle: skilled operators may use POCUS only without adding or prolonging CPR interruptions. AHA also states that its diagnostic and prognostic roles during arrest are not well established. A useful image does not prove a survival benefit.

This post focuses on a proposed transthoracic POCUS workflow. Use it only when trained staff can scan without compromising ALS. Interpretation and decision-making continue in Parts 2 and 3, linked below.

The Operating System

Think of POCUS during arrest as an operating system, not a collection of tricks.

Simple rules

• CPR is the treatment
• POCUS is a decision aid
• One pause = one primary question
• In this proposed workflow, acquire a needed cardiac clip within an already indicated rhythm/pulse check. Lung or other noncardiac scanning may be performed during compressions when it does not interfere with CPR.
• Everything else happens during compressions

ERC-based 2025 guidance emphasizes

• POCUS may help identify tamponade and tension pneumothorax
• RV dilation alone does not diagnose PE
• No ultrasound finding should be the sole reason to stop CPR

When to Scan: Pause vs Compressions

During an already indicated check: keep the entire interruption as short as possible and no longer than 10 seconds

Use the already indicated rhythm check for one needed cardiac clip. The 10-second ceiling covers the entire interruption, including any indicated pulse assessment; it is not an extra scanning allowance. Resume sooner whenever possible.

• If an organized rhythm appears, assess for a pulse within the same brief check. Cardiac motion alone does not establish ROSC. If no definite pulse is found, resume CPR.
• If there are convincing combined clinical and physiological signs of ROSC, follow the ALS circulation-assessment pathway. An ETCO₂ rise alone is insufficient.
• If the rhythm is shockable, deliver the indicated shock promptly and resume compressions; do not delay defibrillation for imaging.

How

• Record a brief clip
• Restart compressions immediately
• Interpret while CPR continues

Conservative workflow cue: if the view is not immediately obtainable, stop scanning and resume compressions. The suggested 1–2 second abort point is this article’s teaching cue, not a separately validated guideline threshold.

During compressions (parallel processing)

Selective options, when clinically indicated

• Lung assessment when pneumothorax is suspected, without obstructing compressions or delaying treatment
• DVT scan (if PE is plausible)
• FAST (if bleeding is plausible)
• Airway ultrasound for selected troubleshooting; it does not replace sustained waveform capnography to exclude oesophageal intubation
• Pre-positioning cardiac or femoral probes
• Femoral vessel localization during compressions; spontaneous pulse assessment only within the indicated brief check, distinguishing compression-generated flow from ROSC

Key principle: select the scan that can answer a relevant question while resuscitation continues. Skip it if it distracts from, obstructs or delays treatment. This is not a requirement to complete every view.

“One Pause = One Question”

Practical meaning:

• At a planned check, record a cardiac clip only when it addresses the most urgent question.
• If tension pneumothorax is suspected, assess and treat it promptly; do not wait for a designated second cycle or for confirmatory imaging when the clinical diagnosis requires immediate decompression.
• Repeat or adjust based on the most likely cause

You may notice additional findings on a single clip, but do not extend the pause to chase them.

Technique That Keeps You Honest

1) Pre-pause probe placement

Place the probe while compressions continue, without obstructing the compressor. Prepare the preset, depth and recording function beforehand. If the team cannot do this safely, omit the scan.

2) Record first, interpret second

Clip during pause → compressions resume → interpret during CPR.

3) One view per pause

If inadequate, stop and try a different view next cycle.
Never chase a perfect image during the pause.

Team Choreography (Prevents Pause Creep)

Suggested roles for this workflow

• Code leader: runs ALS, does not scan
• Dedicated sonographer: pre-positions probe, records clip
• Timer/voice: counts down and enforces restart

Script

• “Scanning on compressions.”
• “Ready for pause.”
• “Recording… 3…2…1… back on chest.”
• “Interpreting during compressions.”

A timer and clear script may help limit pause creep; the team still has to monitor and enforce prompt restart. In the CASA before-and-after study, training and probe pre-positioning were associated with shorter pauses, but this did not establish a survival benefit. Rehearse the sequence, measure actual interruptions and review saved clips afterward.

Cardiac Views: Is There a “Hero View”?

There is no single view that shows everything.
Choose the view your team can obtain fastest without interfering with compressions.

• Default (often practical): subcostal 4-chamber
• Backup: parasternal long-axis (PLAX)

Rule: one view per pause. Switch views next cycle if needed.

Transesophageal echocardiography (TEE) can image during ongoing compressions. It requires a trained team, appropriate equipment and procedural safety checks; it is outside this transthoracic workflow.

In 2026, a small prehospital randomized pilot supported feasibility and reported a higher compression fraction. The 132-patient EXECT-CPR trial did not show a significant improvement in sustained ROSC or survival; it was underpowered. Better images or compression metrics do not establish patient benefit.

Safety Checklist (End With This)

Before every arrest scan, confirm:

• Probe positioned before the pause
• One pause = one primary question
• Clip during pause, interpret during CPR
• Never chase better images
• Never prolong CPR interruptions
• Never stop CPR based on ultrasound alone

CPR first. Scan fast. No delays.

What This Post Is Not Covering

This post does not cover:

• PE decision-making
• Tamponade diagnosis details
• Fine VF vs asystole nuances
• Pitfalls and false positives
• When to terminate resuscitation

These topics continue in Part 2: interpretation pitfalls and Part 3: decision pathways.