This study was supported in part by the grants from the Ministry of Science and Technology, Taiwan (MOST 103-2511-S-002-007). The authors would like to thank Dr. Chih-Hsien Wu and Mr. Jen-Chih Sung for helping the preparation of the photographs and film.

This procedure was approved by the Institutional Review Board of the National Taiwan University Hospital and registered at ClinicalTrials.gov (NCT02952768).
1. Instrumentation
<ol>
	<li>Use a US machine equipped with a curvilinear 2&#8211;5 MHz probe. A portable US is more suitable for CPR.</li>
</ol>
2. Personnel and their roles in the resuscitation team
<ol>
	<li>Ideally, a resuscitation team should be comprised of six members: 1) a leader; 2) a member for airway management (A) and ventilation (B); 3) one for chest compressions (C); 4) one for defibrillation (D); 5) one for intravenous (IV) catheterization and medication; and 6) a recorder.</li>
	<li>If the personnel is limited, have the roles overlap. When US is integrated into the CPR process, the sonographer should be an independent member of the team who is well trained and experienced in resuscitation US and can intervene and interpret the US images in a timely manner without interrupting or delaying resuscitation efforts. However, the leader can also be the sonographer. He or she can use US to search for any potentially reversible causes of resuscitation failure as early as possible while leading the whole CPR process.</li>
</ol>
3. Cardiopulmonary resuscitation process
<ol>
	<li>Perform all resuscitation procedures according to the ALS guidelines6.</li>
	<li>When US is integrated into the CPR process, strict control to minimize interruption of the chest compressions is the highest priority. Restrict the hands-off interval for pulse checks/rhythm analysis and simultaneous US evaluation to no longer than 10 s.
	<ol>
		<li>Use a timer with preset alarms to remind the sonographer of the time intervals. Set the alarm for every 2 min of CPR and 10 s for pulse checks.</li>
	</ol>
	</li>
</ol>
4. US-CAB protocol
<ol>
	<li>US-C: Use cardiac US (US-C) at the start of CPR and at the end of the first five cycles of chest compressions.
	<ol>
		<li>Use the subxiphoid four-chamber view (Figure 1A) to check pericardial effusion, the size of the right and left ventricles, and sonographic cardiac activity.</li>
		<li>Turn the probe 90&#176; (parallel to the long axis of the patient) to measure the diameter of the IVC (Figure 1B).</li>
	</ol>
	</li>
	<li>US-A: Use US-A to check the endotracheal tube location after intubation.
	<ol>
		<li>Place the probe transversely at the suprasternal notch (Figure 1C).</li>
		<li>Note the one air-mucosal interface with one comet-tail artifact (single tract sign) for tracheal intubation.</li>
		<li>Move the probe to the lateral side of the neck to reconfirm the single tract sign.</li>
		<li>Perform reintubation if there are two air-mucosal interfaces with two comet-tail artifacts (double tract sign)12.</li>
	</ol>
	</li>
	<li>US-B: Use US-B to check proper ventilation.
	<ol>
		<li>Put the probe on either side of the chest at the 4th&#8211;5th intercostal spaces over the midaxillary line (Figure 1D).</li>
		<li>Detect lung sliding to evaluate pulmonary ventilation11,13.</li>
		<li>If lung sliding is absent on one side, adjust the depth of the endotracheal tube until bilateral lung sliding is noticed.</li>
	</ol>
	</li>
	<li>US-C: Repeat US-C every 2 min when chest compression is stopped for pulse checks.</li>
	<li>Repeat US-AB after transportation and bed transfer of the patient.</li>
</ol>
5. Settings and approach during CPR
<ol>
	<li>Keep the US machine ready in the resuscitation room of the emergency department. In cases of in-hospital cardiac arrest, a portable US device can be brought to the scene immediately, and turned on instantly.</li>
	<li>Because a lot of resuscitation procedures are performed around the head, neck, and chest of the patient (e.g., chest compressions, defibrillation, intubation, ventilation, etc.), place the US machine in the caudal area of the patient (Figure 2). For example, it should be located over the patient&#8217;s right side for a right-handed sonographer and vice versa. This way the sonographer can get the probe ready and immediately assess the patient&#8217;s condition.</li>
</ol>
6. Image acquisition and recording
<ol>
	<li>Have the US images interpreted by the sonographer and print or store important images for medical records and further discussion with the resuscitation team.</li>
	<li>Ideally, store the US images in the hard disk of the US machine for regular (e.g., monthly) review, either for quality assurance or teaching purposes. Video recording is even better, as it not only provides important information that is less well characterized by still photos but also offers materials for training or subsequent analysis.</li>
</ol>
7. Data interpretation and analysis
<ol>
	<li>Have the sonographer interpret the US images during CPR on-site to help with clinical judgement and decision making. A sonographer, after structured training and continued practice, can perform sonographic evaluation and interpret the data in real CPR scenarios. The interpretation and discussion of the data can also be done by all resuscitation team members during debriefing immediately after the post-CPR phase. The discussion focuses not only on US diagnosis, but on the therapeutic interventions and impact on CPR outcomes following the US examination.</li>
	<li>For research purposes, also have interpretation done afterwards by blinded researchers.</li>
</ol>

<ol>
	<li>Soar, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=European+Resuscitation+Council+Guidelines+for+Resuscitation+2015:+Section+3.+Adult+advanced+life+support.">European Resuscitation Council Guidelines for Resuscitation 2015: Section 3. Adult advanced life support.</a> Resuscitation. 95, 100-147 (2015).</li><li>Takeda, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+assessment+of+three+methods+to+verify+tracheal+tube+placement+in+the+emergency+setting.">The assessment of three methods to verify tracheal tube placement in the emergency setting.</a> Resuscitation. 56 (2), 153-157 (2003).</li><li>Levine, R., Wayne, M., Miller, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=End-tidal+carbon+dioxide+and+outcome+of+out-of-hospital+cardiac+arrest.">End-tidal carbon dioxide and outcome of out-of-hospital cardiac arrest.</a> New England Journal of Medicine. 337, 301-306 (1997).</li><li>Moule, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Checking+the+carotid+pulse:+diagnostic+accuracy+in+students+of+the+healthcare+professions.">Checking the carotid pulse: diagnostic accuracy in students of the healthcare professions.</a> Resuscitation. 44 (3), 195-201 (2000).</li><li>Sitzwohl, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endobronchial+intubation+detected+by+insertion+depth+of+endotracheal+tube,+bilateral+auscultation,+or+observation+of+chest+movements:+randomised+trial.">Endobronchial intubation detected by insertion depth of endotracheal tube, bilateral auscultation, or observation of chest movements: randomised trial.</a> British Medical Journal. 341, 5943 (2010).</li><li>Monsieurs, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=European+Resuscitation+Council+Guidelines+for+Resuscitation+2015:+Section+1.+Executive+summary.">European Resuscitation Council Guidelines for Resuscitation 2015: Section 1. Executive summary.</a> Resuscitation. 95, 1-80 (2015).</li><li>Breitkreutz, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Focused+echocardiographic+evaluation+in+life+support+and+peri-resuscitation+of+emergency+patients:+a+prospective+trial.">Focused echocardiographic evaluation in life support and peri-resuscitation of emergency patients: a prospective trial.</a> Resuscitation. 81 (11), 1527-1533 (2010).</li><li>Hernandez, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=C.A.U.S.E.:+Cardiac+arrest+ultra-sound+exam--a+better+approach+to+managing+patients+in+primary+non-arrhythmogenic+cardiac+arrest.">C.A.U.S.E.: Cardiac arrest ultra-sound exam--a better approach to managing patients in primary non-arrhythmogenic cardiac arrest.</a> Resuscitation. 76 (2), 198-206 (2008).</li><li>Perera, P., Mailhot, T., Riley, D., Mandavia, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+RUSH+exam:+Rapid+Ultrasound+in+SHock+in+the+evaluation+of+the+critically+lll.">The RUSH exam: Rapid Ultrasound in SHock in the evaluation of the critically lll.</a> Emergency Medicine Clinics of North America. 28 (1), 29-56 (2010).</li><li>Blyth, L., Atkinson, P., Gadd, K., Lang, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bedside+focused+echocardiography+as+predictor+of+survival+in+cardiac+arrest+patients:+a+systematic+review.">Bedside focused echocardiography as predictor of survival in cardiac arrest patients: a systematic review.</a> Academic Emergency Medicine. 19, 1119-1126 (2012).</li><li>Lien, W. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=US-CAB+protocol+for+ultrasonographic+evaluation+during+cardiopulmonary+resuscitation:+validation+and+potential+impact.">US-CAB protocol for ultrasonographic evaluation during cardiopulmonary resuscitation: validation and potential impact.</a> Resuscitation. 127, 125-131 (2018).</li><li>Chou, H. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Real-time+tracheal+ultrasonography+for+confirmation+of+endotracheal+tube+placement+during+cardiopulmonary+resuscitation.">Real-time tracheal ultrasonography for confirmation of endotracheal tube placement during cardiopulmonary resuscitation.</a> Resuscitation. 84 (12), 1708-1712 (2013).</li><li>Sim, S. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasonographic+lung+sliding+sign+in+confirming+proper+endotracheal+intubation+during+emergency+intubation.">Ultrasonographic lung sliding sign in confirming proper endotracheal intubation during emergency intubation.</a> Resuscitation. 83 (3), 307-312 (2012).</li><li>Lien, W. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+US-CAB+protocol+for+ultrasonographic+evaluation+during+cardiopulmonary+resuscitation.">A novel US-CAB protocol for ultrasonographic evaluation during cardiopulmonary resuscitation.</a> Resuscitation. 115, 1-2 (2017).</li><li>Roelandt, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasound+stethoscopy.">Ultrasound stethoscopy.</a> European Journal of Internal Medicine. 15, 337-347 (2004).</li><li>Lien, W. C., Chang, W. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Potential+Pitfall+of+Tracheal+Ultrasound+for+the+Confirmation+of+Endotracheal+Intubations.">A Potential Pitfall of Tracheal Ultrasound for the Confirmation of Endotracheal Intubations.</a> Journal of Ultrasound in Medicine. , (2019).</li><li>Huis In't Veld, M. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasound+use+during+cardiopulmonary+resuscitation+is+associated+with+delays+in+chest+compressions.">Ultrasound use during cardiopulmonary resuscitation is associated with delays in chest compressions.</a> Resuscitation. 119, 95-98 (2017).</li><li>Clattenburg, E. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Point-of-care+ultrasound+use+in+patients+with+cardiac+arrest+is+associated+prolonged+cardiopulmonary+resuscitation+pauses:+A+prospective+cohort+study.">Point-of-care ultrasound use in patients with cardiac arrest is associated prolonged cardiopulmonary resuscitation pauses: A prospective cohort study.</a> Resuscitation. 122 (1), 65-68 (2018).</li><li>Lien, W. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Data+on+evaluation+of+proficiency+for+the+US-CAB+curriculum.">Data on evaluation of proficiency for the US-CAB curriculum.</a> Data in Brief. 16 (17), 965-968 (2017).</li><li>Lien, W. C., Chang, W. T., Ma, M. H., Chen, W. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasonography+during+CPR:+Hands-off+or+hands-on.">Ultrasonography during CPR: Hands-off or hands-on.</a> Resuscitation. 125, 8-10 (2018).</li></ol>

The authors have nothing to disclose.

US is a noninvasive, real-time, and readily available imaging modality in emergency and critical care settings. Application of US during CPR plays an important role in diagnosis, guidance of therapeutic intervention, or monitoring15. While many US protocols have been introduced for use with CPR, the US-CAB protocol complies with the sequence of advanced life support (ALS). It integrates important US techniques to detect possibly reversible causes of any issues, and to evaluate the C-A-B status during the whole process of resuscitation11,14.
The scanning sequence of the US-CAB protocol is: 1) C, at the start of resuscitation; 2) AB, after intubation; 3) C, every 2 min during pulse checks and rhythm analysis; 4) AB, after transportation. US-C helps detect possible reversible causes of cardiac arrest and the existence of cardiac contractility. US-AB is used for confirmation of endotracheal tube location and proper ventilation. This can guide the first-line physician&#39;s management resuscitation appropriately. For example, when pericardial effusion is detected, pericardiocentesis can be performed immediately. When a double tract sign is noted after intubation, removal of the endotracheal tube and reintubation can be quickly accomplished.
According to our experience, the hands-off interval for pulse checks and rhythm analysis (which takes less than 10 s) is enough for sonographic examination after proper training11,14. However, if the sonographer cannot complete US-C within 10 s, the team needs to resume chest compressions. US-C can be performed again during the next pulse check.
Tracheal ultrasound (US-A) exhibits a high sensitivity and a high specificity for confirmation of tracheal intubation12. However, evidence is still lacking for detection of the supraglottic airway. In addition, pitfalls occur in patients with proximal esophageal dilatation, which mimics a double tract sign16.
Although the scanning sequence is performed in an arbitrary order, the order can be changed according to a sonographer&#39;s experience. For example, US-B can be performed at the start of resuscitation while using a bag-ventilation mask (BVM) to rule in proper ventilation or rule out pulmonary pathologies. In addition, US-B can be first performed on the right side of the patient, and then on the left side. Because the right side is checked first, if sliding is detected, it is evident that the endotracheal tube is in the trachea even when checking the right bronchus (which can be identified in the next step and also gives a baseline for comparison on the left side). If sliding is not seen, the airway can be checked again, then pneumothorax can be considered.
Concerns regarding interruption of chest compressions to use US have been raised17,18. Perfect integration of the US-CAB protocol into the CPR process necessitates familiarity with the US-C, US-A, and US-B techniques, qualified personnel, optimal instruments, and well-organized teamwork. Structured training and continued practice are needed, and show remarkable improvement in US performance18,19. Therefore, the potential delay of chest compressions can be minimized. Moreover, experienced individuals can try subxiphoid US-C when chest compression is ongoing20. Though the quality of imaging can be limited by a number of factors, such as obesity, it is possible to get a glance at the heart and IVC to rule out important reversible causes for CPR failure as quickly as possible. Similarly, though the initial assessment of US-A and US-B are usually performed immediately after intubation, when chest compressions stop for auscultation, the follow-up US-AB can also be done during chest compressions whenever dislodgement or displacement of the endotracheal tube is suspected.
In conclusion, US-CAB is feasible and provides diagnostic and prognostic abilities during CPR. Through rigorous training and continued practice, as well as adequate integration of the protocol with an organized resuscitation team, the impact of US-CAB protocol can be maximized.

Effective cardiopulmonary resuscitation (CPR) for cardiac arrest is key to successful revival of a patient. Circulation (C), airway (A), and breathing (B) are the three crucial components in either basic (BLS) or advanced life support (ALS). The evaluation of the C-A-B status during CPR basically relies on pulse checks, auscultation, and capnography1. In true clinical conditions, however, CPR is often complex and chaotic, and these methods may have limitations2,3. For example, the accuracy of pulse checks is often suboptimal even when performed by healthcare providers4. More than half of one lung intubations might be misdirected if guided by auscultation alone5. Even wave capnography can be affected by factors such as low cardiac output, low pulmonary flow, and use of epinephrine during CPR2. Therefore, more effective, accurate evaluation of the C-A-B status is mandatory.
When trying to search for the etiology of cardiac arrest or any potentially reversible factors during CPR, medical history and physical examination are often insufficient. The detection of reversible causes, such as the 5Hs (i.e., hypoxia, hypovolemia, hyperkalemia/hypokalemia, acidosis, and hypothermia) and the 5Ts (i.e., cardiac tamponade, tension pneumothorax, pulmonary thromboembolism, coronary thrombosis, and toxins or tablets), often requires advanced examinations.
Ultrasound (US) is a useful imaging modality in emergency and critical care settings. The European Resuscitation Council (ERC) Guidelines suggest that US can be an integral part of resuscitation6. US can readily identify critical but potentially reversible factors that negatively affect CPR, such as cardiac tamponade, pulmonary thromboembolism, and hypovolemia7,8,9. US also helps rule out pneumothorax and acute coronary syndrome. Moreover, US confers prognostic implications even when CPR is being performed. The presence of sonographic cardiac activity during CPR has been reported to confer higher chances of ROSC, survival, and hospital discharge10,11. In addition to sonographic evaluation of the heart and circulation status, tracheal US is employed for confirmation of proper endotracheal intubation12, while lung US is applied to confirm proper bilateral pulmonary ventilation13.
While high-quality CPR with minimal interruptions to the compressions is the most important factor for resuscitation, it is important to understand how to seamlessly integrate US into the process of resuscitation without interfering with CPR. We therefore developed a novel, ALS-compliant US-CAB protocol for use during CPR14. This paper presents a detailed description of the settings, personnel, and instruments necessary for better integration of the US protocol into the regular CPR process that first-line physicians can easily incorporate and implement into their practice.

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			<td class="xl65" height="21" style="height:15.75pt;width:162pt" width="216">Ultrasound</td>
			<td class="xl65" style="width:140pt" width="186">Cannon, Japan</td>
			<td class="xl65" style="width:89pt" width="119">SSA-550A</td>
			<td class="xl66" style="width:125pt" width="167">nil</td>
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ultrasonographic assessment during cardiopulmonary resuscitation

The US-CAB (Ultrasound, Circulation/Airway/Breathing) protocol integrates several sonographic techniques into a structured assessment of the circulation, airway, and breathing status of a patient during cardiopulmonary resuscitation (CPR) in an advanced life support-compliant manner. US-C provides a subxiphoid view of the heart, to look for potentially reversible causes of disease, such as pericardial effusion, pulmonary embolism, hypovolemia, and acute coronary thrombosis. Sonographic cardiac activity during CPR not only helps differentiate pseudo-pulseless electrical activity (PEA) from true PEA but also represents a higher chance of the return of spontaneous circulation (ROSC) and survival. Evaluation of the inferior vena cava (IVC) shows the fluid status of the patient and indicates the best methods to use for fluid resuscitation. If aortic dissection is suspected, a subxiphoid view of the aorta is suggested for identifying an intimal flap. Once intubation is done, tracheal ultrasound (US-A) at the suprasternal notch helps differentiate endotracheal intubation (one air-mucosal interface with one comet-tail) from esophageal intubation (double tract sign). Immediately following US-A, bilateral lung US (US-B) should be done to confirm proper bilateral ventilation using the lung sliding sign. In addition, US-C can be serially followed to see the dynamic changes in the cardiac chambers and IVC, or any cardiac contraction suggestive of ROSC. US-B can also detect coexisting lung or pleural pathologies without interfering with the performance of CPR. The main concern when implementing this method is maintaining high-quality CPR without delays in chest compressions when performing US-CAB. Rigorous training and continued practice are key to minimize any interruptions during resuscitation.

US-C with subxiphoid evaluation of the heart displays a cardiac four-chamber view as shown in Figure 3A. At this point, detection of any of the three typical patterns suggestive of specific etiologies or reversible factors is possible.
Identify the presence and characters of pericardial effusion: If pericardial effusion is present, notice if the right heart chambers (i.e., the right atrium or even the right ventricle) are compressed. If compression of the right atrium and ventricle is noted (Figure 3A), pericardiocentesis is indicated and should be done immediately. If there is no compression of the right heart chambers, whatever the effusion amount is, CPR should be continued and pericardiocentesis should not be performed to not waste time. Pericardial effusion is also of diagnostic value. If the echogenicity is high or blood clots are present in the pericardial sac, the etiology could be cancer, aortic dissection with rupture into pericardium, etc. The nature of the pericardial effusion and the possible underlying etiologies can guide the decision whether to perform pericardiocentesis.
If pericardial effusion is absent, evaluate the size of the ventricles. If the right ventricle is dilated, with the interventricular septum compressing the left ventricle, increased right ventricular pressure is likely. Pulmonary embolism should be taken into consideration in this case, especially if there is jugular vein engorgement or unilateral leg swelling.
If the right heart chambers are small in size or even collapsed, marked hypovolemia is suspected in patients with substantial gastrointestinal bleeding or dehydration.
While verifying the three typical patterns (i.e., cardiac tamponade, pulmonary embolism, and hypovolemia), sonographic cardiac activity should be clarified. This can help differentiate pseudo-PEA from true PEA, detect fine ventricular fibrillation, and identify regional wall motion abnormalities in specific coronary artery territories.
US-C with subxiphoid evaluation of the IVC can be demonstrated by a vertical approach (Figure 1B). Visual identification of the IVC diameter helps assess the fluid status of the patient (Figure 3B). The IVC can also be evaluated with the subxiphoid transverse view (Figure 3C).
US-C with subxiphoid verification of the descending abdominal aorta can be approached via a vertical (Figure 3D) or transverse view (Figure 3C). Though optional, this evaluation is recommended if aortic dissection is suspected from clinical presentation or when hemopericardium is observed on US-C cardiac evaluation (Figure 3A).
US-A for confirmation of the location of the endotracheal tube can be done after intubation or any time during CPR when dislodgement is suspected. Endotracheal intubation is confirmed if a single tract sign is observed (Figure 4A). If there is a double tract sign, esophageal intubation is highly likely.
US-B is usually done immediately after US-A when auscultation or capnography is being performed by other team members. However, it can also be done any time during CPR when displacement of the endotracheal tube with one lung intubation is suspected, or when specific etiologies such as pneumothorax (Figure 4B) or hemothorax need to be ruled out.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/59144/59144fig1.jpg" /> 
Figure 1: Ultrasonographic (US) approach in US-CAB protocol. (A) Subxiphoid assessment of the heart. (B) Subxiphoid vertical approach for assessment of the inferior vena cava and aorta. (C) Tracheal US with the probe placed transversely on the anterior neck superior to the suprasternal notch. (D) Lung US with probe placed on mid axillary line at the 4th to 5th intercostal space, left side first and then right side. <a href="https://www.jove.com/files/ftp_upload/59144/59144fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/59144/59144fig2.jpg" /> 
Figure 2: Settings of ultrasound (US) and sonographers during cardiopulmonary resuscitation. <a href="https://www.jove.com/files/ftp_upload/59144/59144fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/59144/59144fig3.jpg" /> 
Figure 3: Representative images of US-C, A and B. (A) Subxiphoid four-chamber view of the heart showing pericardial effusion with compression of the right ventricle (arrow). (B) Subxiphoid vertical view of the IVC. (C) Subxiphoid transverse view of the IVC and aorta. (D) Subxiphoid vertical view of the aorta. <a href="https://www.jove.com/files/ftp_upload/59144/59144fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/59144/59144fig4.jpg" /> 
Figure 4: Ultrasonographic (US) assessment of endotracheal tube location and bilateral ventilation. (A) Tracheal US demonstration of single air-mucosa interface (asteroid = single comet tail sign). (B) Lung US assessment for lung sliding sign (left, 2D image; right, M-mode image). <a href="https://www.jove.com/files/ftp_upload/59144/59144fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Ultrasonographic Assessment During Cardiopulmonary Resuscitation at JoVE.com

Ultrasonographic Assessment During Cardiopulmonary Resuscitation

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 (Ultrasound, Circulation/Airway/Breathing) protocol integrates several sonographic techniques into a structured assessment of the circulation, ...

ultrasonographic-assessment-during-cardiopulmonary-resuscitation

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6.3K Views.  National Taiwan University Hospital and College of Medicine. 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.

Video: Ultrasonographic Assessment During Cardiopulmonary Resuscitation

Normothermic Cardiac Arrest and Cardiopulmonary Resuscitation: A Mouse Model of Ischemia-Reperfusion Injury

Acute Kidney Injury (AKI) is a common, highly lethal, complication of critical illness which has a high mortality1-4 and which is most 
frequently caused by whole-body hypoperfusion.5,6 Successful reproduction of whole-body hypoperfusion in rodent models has been fraught with 
difficulty.7-9,9,10 Models which employ focal ischemia have repeatedly demonstrated results which do not translate to the clinical setting, and larger 
animal models which allow for whole body hypoperfusion lack access to the full toolset of genetic manipulation possible in the mouse.11,12 However, in recent 
years a mouse model of cardiac arrest and cardiopulmonary resuscitation has emerged which can be adapted to model AKI.13 This model reliably reproduces 
physiologic, functional, anatomic, and histologic outcomes seen in clinical AKI, is rapidly repeatable, and offers all of the significant advantages of a murine surgical 
model, including access to genetic manipulative techniques, low cost relative to large animals, and ease of use. Our group has developed extensive experience 
with use of this model to assess a number of organ-specific outcomes in AKI.14,15

A powerful model for perioperative and critical care related acute kidney injury is presented. Using whole body hypoperfusion induced by cardiac arrest it is possible to nearly replicate the histologic and functional changes of clinical AKI.

Acute Kidney Injury (AKI) is a common, highly lethal, complication of critical illness which has a high mortality1-4 and which is most 
frequently caused ...

A Novel Application of Musculoskeletal Ultrasound Imaging

Ultrasound is an attractive modality for imaging muscle and tendon motion during dynamic tasks and can provide a complementary methodological approach for biomechanical studies in a clinical or laboratory setting. Towards this goal, methods for quantification of muscle kinematics from ultrasound imagery are being developed based on image processing. The temporal resolution of these methods is typically not sufficient for highly dynamic tasks, such as drop-landing. We propose a new approach that utilizes a Doppler method for quantifying muscle kinematics. We have developed a novel vector tissue Doppler imaging (vTDI) technique that can be used to measure musculoskeletal contraction velocity, strain and strain rate with sub-millisecond temporal resolution during dynamic activities using ultrasound. The goal of this preliminary study was to investigate the repeatability and potential applicability of the vTDI technique in measuring musculoskeletal velocities during a drop-landing task, in healthy subjects. The vTDI measurements can be performed concurrently with other biomechanical techniques, such as 3D motion capture for joint kinematics and kinetics, electromyography for timing of muscle activation and force plates for ground reaction force. Integration of these complementary techniques could lead to a better understanding of dynamic muscle function and dysfunction underlying the pathogenesis and pathophysiology of musculoskeletal disorders.

We describe a new ultrasound-based vector tissue Doppler imaging technique to measure muscle contraction velocity, strain and strain rate with sub-millisecond temporal resolution during dynamic activities. This approach provides complementary measurements of dynamic muscle function and could lead to a better understanding of mechanisms underlying musculoskeletal disorders.

Ultrasound is an attractive modality for imaging muscle and tendon  motion during dynamic tasks and can provide a complementary methodological  approach ...

A Rat Model of Ventricular Fibrillation and Resuscitation by Conventional Closed-chest Technique

A rat model of electrically-induced ventricular fibrillation followed by cardiac resuscitation using a closed chest technique that incorporates the basic components of cardiopulmonary resuscitation in humans is herein described. The model was developed in 1988 and has been used in approximately 70 peer-reviewed publications examining a myriad of resuscitation aspects including its physiology and pathophysiology, determinants of resuscitability, pharmacologic interventions, and even the effects of cell therapies. The model featured in this presentation includes: (1) vascular catheterization to measure aortic and right atrial pressures, to measure cardiac output by thermodilution, and to electrically induce ventricular fibrillation; and (2) tracheal intubation for positive pressure ventilation with oxygen enriched gas and assessment of the end-tidal CO2. A typical sequence of intervention entails: (1) electrical induction of ventricular fibrillation, (2) chest compression using a mechanical piston device concomitantly with positive pressure ventilation delivering oxygen-enriched gas, (3) electrical shocks to terminate ventricular fibrillation and reestablish cardiac activity, (4) assessment of post-resuscitation hemodynamic and metabolic function, and (5) assessment of survival and recovery of organ function. A robust inventory of measurements is available that includes &#8211; but is not limited to &#8211; hemodynamic, metabolic, and tissue measurements. The model has been highly effective in developing new resuscitation concepts and examining novel therapeutic interventions before their testing in larger and translationally more relevant animal models of cardiac arrest and resuscitation.

This article describes a rat model of electrically-induced ventricular fibrillation and resuscitation by chest compression, ventilation, and delivery of electrical shocks that simulates an episode of sudden cardiac arrest and conventional cardiopulmonary resuscitation. The model enables gathering insights on the pathophysiology of cardiac arrest and exploration of new resuscitation strategies.

A rat model of electrically-induced ventricular fibrillation followed by cardiac resuscitation using a closed chest technique that incorporates the basic ...

Assessment of Pulmonary Capillary Blood Volume, Membrane Diffusing Capacity, and Intrapulmonary Arteriovenous Anastomoses During Exercise

Exercise is a stress to the pulmonary vasculature. With incremental exercise, the pulmonary diffusing capacity (DLCO) must increase to meet the increased oxygen demand; otherwise, a diffusion limitation may occur. The increase in DLCO with exercise is due to increased capillary blood volume (Vc) and membrane diffusing capacity (Dm). Vc and Dm increase secondary to the recruitment and distension of pulmonary capillaries, increasing the surface area for gas exchange and decreasing pulmonary vascular resistance, thereby attenuating the increase in pulmonary arterial pressure. At the same time, the recruitment of intrapulmonary arteriovenous anastomoses (IPAVA) during exercise may contribute to gas exchange impairment and/or prevent large increases in pulmonary artery pressure.
We describe two techniques to evaluate pulmonary diffusion and circulation at rest and during exercise. The first technique uses multiple-fraction of inspired oxygen (FIO2) DLCO breath holds to determine Vc and Dm at rest and during exercise. Additionally, echocardiography with intravenous agitated saline contrast is used to assess IPAVAs recruitment.
Representative data showed that the DLCO, Vc, and Dm increased with exercise intensity. Echocardiographic data showed no IPAVA recruitment at rest, while contrast bubbles were seen in the left ventricle with exercise, suggesting exercise-induced IPAVA recruitment.
The evaluation of pulmonary capillary blood volume, membrane diffusing capacity, and IPAVA recruitment using echocardiographic methods is useful to characterize the ability of the lung vasculature to adapt to the stress of exercise in health as well as in diseased groups, such as those with pulmonary arterial hypertension and chronic obstructive pulmonary disease.

To assess the pulmonary diffusion and vasculature responses to exercise, we describe the multiple-inspired oxygen diffusion capacity technique to determine capillary blood volume and membrane diffusing capacity, as well as agitated saline contrast echocardiography to assess the recruitment of intrapulmonary arteriovenous anastomoses.

Exercise is a stress to the pulmonary vasculature. With incremental exercise, the pulmonary diffusing capacity (DLCO) must increase to meet the increased ...

Cardiopulmonary Bypass in a Mouse Model: A Novel Approach

As prolonged cardiopulmonary bypass becomes more essential during cardiac interventions, an increasing clinical demand arises for procedure optimization and for minimizing organ damage resulting from prolonged extracorporal circulation. The goal of this paper was to demonstrate a fully functional and clinically relevant model of cardiopulmonary bypass in a mouse. We report on the device design, perfusion circuit optimization, and microsurgical techniques. This model is an acute model, which is not compatible with survival due to the need for multiple blood drawings. Because of the range of tools available for mice (e.g., markers, knockouts, etc.), this model will facilitate investigation into the molecular mechanisms of organ damage and the effect of cardiopulmonary bypass in relation to other comorbidities.

This paper describes how to perform cardiopulmonary bypass in mice. This novel model will facilitate the investigation of the molecular mechanisms involved in organ damage.

As prolonged cardiopulmonary bypass becomes more essential during cardiac interventions, an increasing clinical demand arises for procedure optimization ...

Microscopy Based Methods for the Assessment of Epithelial Cell Migration During In Vitro Wound Healing

Cell migration is a mandatory aspect for wound healing. Creating artificial wounds on research animal models often results in costly and complicated experimental procedures, while potentially lacking in precision. In vitro culture of epithelial cell lines provides a suitable platform for researching the cell migratory behavior in wound healing and the impact of treatments on these cells. The physiology of epithelial cells is often studied in non-confluent conditions; however, this approach may not resemble natural wound healing conditions. Disrupting the epithelium integrity by mechanical means generates a realistic model, but may impede the application of molecular techniques. Consequently, microscopy based techniques are optimal for studying epithelial cell migration in vitro. Here we detail two specific methods, the artificial wound scratch assay and the artificial migration front assay, that can obtain quantitative and qualitative data, respectively, on the migratory performance of epithelial cells.

Microscopy Based Methods for the Assessment of Epithelial Cell Migration During  In Vitro Wound Healing

This manuscript describes how incision-like lesions made on cultured epithelial cell monolayers conveniently model wound healing in vitro, allowing for imaging by confocal or laser scanning microscopy, and which can provide high-quality quantitative and qualitative data for studying both cell behavior and the mechanisms involved in migration.

Cell migration is a mandatory aspect for wound healing. Creating artificial wounds on research animal models often results in costly and complicated ...

The Perinatal Asphyxiated Lamb Model: A Model for Newborn Resuscitation

Birth asphyxia accounts for nearly one million deaths worldwide each year, and is one of the primary causes of early neonatal morbidity and mortality. Many aspects of the current neonatal resuscitation guidelines remain controversial given the difficulties in conducting randomized clinical trials owing to the infrequent and often unpredictable need for extensive resuscitation. Most studies on neonatal resuscitation stem from manikin models that fail to truly reflect physiologic changes or piglet models that have cleared their lung fluid and that have completed the transition from fetal to neonatal circulation. The present protocol provides a detailed step-by-step description on how to create a perinatal asphyxiated fetal lamb model. The proposed model has a transitioning circulation and fluid-filled lungs, which mimics human newborns following delivery, and is, therefore, an excellent animal model to study newborn physiology. An important limitation to lamb experiments is the higher associated cost.

Invasive instrumentation of the fetal lamb provides accurate physiologic measurements of the transitioning circulation in a model that closely mimics the newly born infant.

Birth asphyxia accounts for nearly one million deaths worldwide each year, and is one of the primary causes of early neonatal morbidity and mortality. ...

Integration of Brain Tissue Saturation Monitoring in Cardiopulmonary Exercise Testing in Patients with Heart Failure

Cerebral hypo-oxygenation during rest or exercise negatively impacts the exercise capacity of patients with heart failure with reduced ejection fraction (HF). However, in clinical cardiopulmonary exercise testing (CPET), cerebral hemodynamics is not assessed. NIRS is used to measure cerebral tissue oxygen saturation (SctO2) in the frontal lobe. This method is reliable and valid and has been utilized in several studies. SctO2 is lower during both rest and peak exercise in patients with HF than in healthy controls (66.3 &#177; 13.3% and 63.4 &#177; 13.8% vs. 73.1 &#177; 2.8% and 72 &#177; 3.2%). SctO2 at rest is significantly linearly correlated with peak VO2 (r = 0.602), oxygen uptake efficiency slope (r = 0.501), and brain natriuretic peptide (r = -0.492), all of which are recognized prognostic and disease severity markers, indicating its potential prognostic value. SctO2 is determined mainly by end-tidal CO2 pressure, mean arterial pressure, and hemoglobin in the HF population. This article demonstrates a protocol that integrates SctO2 using NIRS into incremental CPET on a calibrated bicycle ergometer.

This protocol integrated near-infrared spectroscopy into conventional cardiopulmonary exercise testing to identify the involvement of the cerebral hemodynamic response in exercise intolerance in patients with heart failure.

Cerebral hypo-oxygenation during rest or exercise negatively impacts the exercise capacity of patients with heart failure with reduced ejection fraction ...

Transthoracic Echocardiography to Assess Post-Resuscitation Left Ventricular Dysfunction After Acute Myocardial Infarction and Cardiac Arrest in Pigs

One of the main causes of out-of-hospital cardiac arrest is acute myocardial infarction (AMI). After successful resuscitation from cardiac arrest, approximately 70% of patients die before hospital discharge due to post-resuscitation myocardial and cerebral dysfunction. In experimental models, myocardial dysfunction after cardiac arrest, characterized by an impairment in both left ventricular (LV) systolic and diastolic function, has been described as reversible but very little data are available in cardiac arrest models associated with AMI in pigs. Transthoracic echocardiography is the first-line diagnostic test for the assessment of myocardial dysfunction, structural changes and/or AMI extension. In this pig model of ischemic cardiac arrest, echocardiography was done at baseline and 2-4 and 96 hours after resuscitation. In the acute phase, the examinations are done in anesthetized, mechanically ventilated pigs (weight 39.8 &#177; 0.6 kg) and ECG is recorded continuously. Mono- and bi-dimensional, Doppler and tissue Doppler recordings are acquired. Aortic and left atrium diameter, end-systolic and end-diastolic left ventricular wall thicknesses, end-diastolic and end-systolic diameters and shortening fraction (SF) are measured. Apical 2-, 3-, 4-, and 5-chamber views are acquired, LV volumes and ejection fraction are calculated. Segmental wall motion analysis is done to detect the localization and estimate the extent of myocardial infarction. Pulsed Wave Doppler echocardiography is used to record trans-mitral flow velocities from a 4-apical chamber view and trans-aortic flow from a 5-chamber view to calculate LV cardiac output (CO) and stroke volume (SV). Tissue Doppler Imaging (TDI) of LV lateral and septal mitral anulus is recorded (TDI septal and lateral s&#39;, e&#39;, a&#39; velocities). All the recordings and measurements are done according to the recommendations of the American and European Societies of Echocardiography Guidelines.

Transthoracic echocardiography is the first-line diagnostic test for post-resuscitation left ventricular dysfunction and structural changes in a pig model of cardiac arrest.

One of the main causes of out-of-hospital cardiac arrest is acute myocardial infarction (AMI). After successful resuscitation from cardiac arrest, ...

Providing Visual Biofeedback Using Brightness Mode Ultrasound During a Golf Swing

Using ultrasound biofeedback in conjunction with verbal cueing can increase muscle thickness more than verbal cueing alone and may augment traditional rehabilitation techniques in an athletic, physically active population. Brightness mode (B-mode) ultrasound can be applied using frame-by-frame analysis synchronized with video to understand muscle thickness changes during these dynamic tasks. Visual biofeedback with ultrasound has been established in static positions for the muscles of the lateral abdominal wall. However, by securing the transducer to the abdomen using an elastic belt and foam block, biofeedback can be applied during more specific tasks prevalent in lifetime sports, such as golf. To analyze muscle activity during a golf swing, muscle thickness changes can be compared. The thickness must increase throughout the task, indicating that the muscle is more active. This methodology allows clinicians to immediately replay ultrasound videos for patients as a visual tool to instruct proper activity of the muscles of interest. For example, ultrasound can be used to target the external and internal obliques, which play an important role in swinging a golf club or any other rotational sport or activity. This methodology aims to increase oblique muscle thickness during the golf swing. Additionally, the timing of muscle contraction can be targeted by instructing the patient to contract the abdominal muscles at specific time points, such as the beginning of the downswing, with the goal of improving muscle firing patterns during tasks.

Brightness mode ultrasound can be used to provide visual biofeedback of the muscles of the lateral abdominal wall during a golf swing. Post-swing visual and verbal instruction can increase the muscle activation and timing of the external and internal obliques.

Using ultrasound biofeedback in conjunction with verbal cueing can increase muscle thickness more than verbal cueing alone and may augment traditional ...