Ultrasonographic Assessment During Cardiopulmonary Resuscitation
October 24th, 2020
Here, we present a US-CAB (Ultrasound, Circulation/Airway/Breathing) protocol for use during cardiopulmonary resuscitation (CPR). US-C evaluates the subxiphoid view of the heart and inferior vena cava. After intubation, tracheal US (US-A) and lung US (US-B) help confirm endotracheal intubation and proper ventilation.
The US-CAB protocol is a simple, structured protocol, that is used during resuscitation. It was named after the CAB sequences in the advanced life support guidelines. The US-CAB protocol can be used at during resuscitation.
It has positive impact on patient outcomes. Ideally, a resuscitation team should be comprised of a leader, a member for airway management and ventilation, a member for chest compressions, a member for defibrillation, a member for intravenous catheterization and medication, and a recorder. A sonographer should also be present as an independent member of the team who is well-trained and experienced in resuscitation ultrasound and who can intervene and interpret the ultrasound images in a timely manner without interrupting or delaying the resuscitation efforts.
When ultrasound is to be integrated into the CPR process, place a portable ultrasound machine in the caudal region of the patient, and set an alarm for every two minutes for CPR and every 10 seconds for pulse checks. To restrict the hands-off interval for pulse checks rhythm analysis, and simultaneous ultrasound evaluation to no longer than 10 seconds. At the start of CPR and at the end of the first five cycles of chest compressions use the subxiphoid four chamber view to check for pericardial effusion, the size of the left and right ventricles, and sonographic cardiac activity.
Then turn the probe 90 degrees, parallel to the long axis of the patient to measure the diameter of the inferior vena cava. To check the endotracheal tube location after intubation, place the probe transversely at the suprasternal notch and note the one air mucosal interface with one comet tail artifact for tracheal intubation. Move the probe to the lateral side of the neck to reconfirm the single tract sign.
And re-intubate, if there are two air mucosal interfaces with two comet tail artifacts. To check for proper ventilation, place the probe on both sides of the chest at the fourth to fifth intercostal spaces over the mid axillary line and look for lung sliding to evaluate pulmonary ventilation. If lung sliding is absent on one side, adjust the depth of the endotracheal tube until bilateral lung sliding is noticed.
Then repeat the cardiac ultrasound every two minutes when chest compression is stopped for pulse checks. Continue to repeat the airway and breathing ultrasounds after patient transport and bed transfer. If compression of the right atrium and ventricle is noted during cardiac ultrasound with subxiphoid evaluation, pericardiocentesis is indicated and should be performed immediately.
Pericardial effusion is also of diagnostic value. If the echogenicity is high or blood clots are present in the pericardial sac, the etiology could indicate serious complications. Cardiac ultrasound with subxiphoid evaluation of the inferior vena cava can be demonstrated by a vertical approach, and visual identification of the inferior vena cava diameter helps assess the fluid status of the patient.
The inferior vena cava can also be evaluated in the subxiphoid transverse view. Cardiac ultrasound with subxiphoid verification of the descending abdominal aorta can be approached via a vertical or transverse view. This optional evaluation is recommended if aortic dissection is suspected from clinical presentation or when hemopericardium is observed by cardiac ultrasound cardiac evaluation.
Endotracheal intubation is confirmed if a single tract sign is observed. If there is a double tract sign esophageal intubation is highly likely. Breathing ultrasound is usually performed immediately after airway ultrasound when auscultation or capnography is being performed but it can also be performed anytime during CPR when displacement of the endotracheal tube with one lung intubation is suspected or when specific etiologies such as pneumothorax or hemothorax need to be ruled out.
Although the scanning sequence is organized, the order can be changed according to the experience of the sonographer. Focused training and continued practice are essential to minimize processes during chest compressions. Maintaining a good image of quality is an important issue for further studies.
View the full transcript and gain access to thousands of scientific videos
Overview
The US-CAB protocol is a structured approach used during cardiopulmonary resuscitation (CPR) to enhance patient outcomes. It incorporates ultrasound techniques to evaluate cardiac function and confirm airway management.
Key Study Components
Area of Science
- Cardiopulmonary resuscitation
- Ultrasound in emergency medicine
- Patient outcome improvement
Background
- The US-CAB protocol is based on advanced life support guidelines.
- It includes evaluation of the heart and inferior vena cava via ultrasound.
- Tracheal and lung ultrasound confirm intubation and ventilation.
- A well-coordinated resuscitation team is essential for effective implementation.
Purpose of Study
- To present a structured protocol for use during CPR.
- To improve patient outcomes through the use of ultrasound.
- To define roles within the resuscitation team for optimal performance.
Methods Used
- Implementation of the US-CAB protocol during resuscitation efforts.
- Use of ultrasound to assess cardiac and airway conditions.
- Team-based approach with defined roles for each member.
- Training for sonographers in resuscitation ultrasound.
Main Results
- The US-CAB protocol positively impacts patient outcomes.
- Effective team coordination enhances the resuscitation process.
- Ultrasound aids in timely decision-making during CPR.
- Presence of a trained sonographer is crucial for protocol success.
Conclusions
- The US-CAB protocol is a valuable tool in emergency medicine.
- Structured roles within the team improve resuscitation effectiveness.
- Ultrasound technology plays a key role in modern CPR practices.
Frequently Asked Questions
Executive Industry Relevance
The US-CAB protocol provides a structured ultrasound framework for real-time assessment during cardiopulmonary resuscitation, supporting rapid identification of reversible causes of cardiac arrest. This capability enhances mechanistic de-risking in preclinical and translational models by enabling dynamic monitoring of cardiac function, fluid status, and airway integrity under stress conditions. Integration of such imaging protocols improves predictive confidence in disease-relevant systems used for target validation and lead identification in cardiovascular therapeutic development.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables interrogation of therapeutic hypotheses related to cardiac contractility, vascular tone, and pulmonary perfusion in disease models.
- Operational Value: Supports functional target validation by distinguishing true pulseless electrical activity from pseudo-PEA through direct visualization of cardiac activity.
- Predictive Value: Increases confidence in lead compounds by correlating sonographic cardiac activity with higher likelihood of return of spontaneous circulation.
Screening & Assay Development
- Assay Readiness: Prepares validated biological systems for downstream workflows by confirming proper intubation and bilateral ventilation via lung sliding sign.
- Reproducibility: Standardizes respiratory and circulatory assessment through serial inferior vena cava and cardiac chamber measurements during CPR cycles.
- Scalability: Facilitates platform reuse across model systems by allowing protocol adaptation based on sonographer experience and clinical suspicion.
Translational & Preclinical Research
- Translational Continuity: Bridges discovery through preclinical validation by enabling serial monitoring of dynamic changes in cardiac chambers and IVC during resuscitation.
- Pathology Detection: Identifies coexisting lung or pleural pathologies such as pneumothorax or hemothorax without interrupting resuscitation efforts.
- Risk-Adjusted Decisions: Informs advancement strategies by detecting pericardial effusion, aortic dissection, or hypovolemia that may indicate need for pericardiocentesis or fluid resuscitation.
Pipeline & Workflow Integration
The US-CAB protocol fits within the discovery continuum from hypothesis testing to preclinical validation, particularly in cardiovascular and pulmonary therapeutic areas where physiological stress models are employed.
- Discovery Biology: Supports hypothesis testing and pathway clarification by evaluating cardiac function and vascular response under ischemic conditions.
- Screening: Enhances assay readiness through reproducible lung sliding and tracheal intubation confirmation, ensuring reliable compound evaluation in ventilated models.
- Analytics: Provides quantitative outputs such as IVC diameter and ventricular size to assess fluid status and cardiac function across experimental groups.
- Translational Research: Connects to preclinical continuity by detecting reversible etiologies like pericardial tamponade or endotracheal misplacement that impact survival outcomes.
- Enterprise Reuse: Functions as a reusable capability across teams due to its structured, team-based design requiring defined roles and training.
Operational & Enterprise Impact
- Scientific Value: Reduces mechanistic ambiguity by differentiating true cardiac arrest from pseudo-PEA through direct sonographic visualization of myocardial motion.
- Operational Value: Ensures standardization and reproducibility via timed ultrasound intervals aligned with pulse checks and chest compression cycles.
- Strategic Value: Improves go/no-go decisions by enabling real-time detection of ROSC predictors and complications like hemopericardium or aortic dissection.
- Portfolio Impact: Supports risk-adjusted prioritization by identifying patients or models with higher likelihood of survival based on IVC collapsibility and cardiac activity.
Implementation Considerations
- Requires sonographers trained in resuscitation ultrasound to acquire and interpret images without delaying chest compressions.
- Necessitates portable ultrasound equipment positioned caudally and synchronized with CPR rhythm via alarms for two-minute and ten-second intervals.
- Demands cross-team standardization to maintain image quality and protocol adherence during patient transport and bed transfer.
- Involves adaptation considerations across model systems, particularly in adjusting probe placement for subxiphoid, suprasternal, and intercostal views.
- Limited by the need to minimize hands-off intervals, requiring rigorous training to prevent interruptions in high-quality CPR during ultrasound acquisition.
