The CPVAP principle for the application and training of critical care ultrasound and the corresponding education system in China

Introduction The use of critical care ultrasound (CCUS) is increasingly prevalent, particularly in resource-limited settings, as seen during the COVID-19 pandemic, where it aided life-saving interventions. However, the utility of the ultrasound equipment depends entirely on the operation of well-trained specialists; thus, appropriate practical training is essential and imperative to ensure competence in the use of CCUS for life-saving interventions.1–3 Mayo et al3 identify three prerequisites for effective patient outcomes: a well-designed ultrasound device, an adequately trained operator, and the effective clinical use of results at the point of care. These prerequisites translate into core competencies critical for effective CCUS applications, including view quality control, clinical question formulation, and structured workflows. Standardized imaging is fundamental for an accurate interpretation, and as CCUS is inherently a problem-oriented examination,4–6 it requires the clear articulation of clinical questions. Moreover, specific applications necessitate corresponding workflow protocols to guide and standardize clinical practice.7 Therefore, “universal” CCUS training should encompass all three competencies; however, due to the heterogeneity among physicians, a rigid, one-size-fits-all training model presents significant challenges.8 Given that the overarching objective remains the development of a comprehensive CCUS competence, training must be tailored to specific clinical scenarios, with curricula adapted to defined diagnostic and therapeutic goals. In general, CCUS training should be tailored to specific practitioner characteristics and clinical contexts to support a progressive learning system. To promote appropriate CCUS use,9 Yin et al proposed the CPVAP principles based on the CCUS application characteristics. These principles distill essential care ultrasound into a logical five-step approach—clinical analysis, protocol, view quality control, approach, and practice workflow—each with specific process guidance.9 This approach demonstrates favorable clinical outcomes. An effective CCUS application depends on the accurate interpretation of visualized ultrasound findings integrated with clinical information to ensure practical utility. Current training programs often emphasize image acquisition, measurement, and interpretation proficiency, but fall short of integrating these skills with clinical workflows. In contrast, the CPVAP principle initiates training starting with clinical discrimination and thereafter progresses modularly through image acquisition training with the incorporation of quality control and interpretation. It further advances to structured analytical pathways and culminates in consolidation through an integrated practice platform. Accordingly, CCUS training and assessment based on CPVAP principles are more structured, reasonable, and comprehensive. Consequently, the Critical Care Ultrasound Study Group (CCUSG) has enhanced the universal training curriculum and developed training systems tailored for different clinical application scenarios. In the following sections, we introduce CPVAP principles and present our training system for peer reference (Figure 1).Figure 1.: The application algorithm and training system of CCUSG based on the CPVAP principle.Clinical analysis The first component of the CPVAP principles is “clinical analysis.” CCUS, one of the primary means of information acquisition in the intensive care unit, is based on a problem-oriented approach. Critical care specialists often encounter various clinical manifestations. The initial task is to recognize these symptoms, group them into symptom clusters, and formulate precise clinical questions. For example, if a patient presents with a cluster of symptoms, including tachycardia, hypotension, oliguria, and acidosis, the central issue can be summarized as an acute circulatory disturbance. This leads to clinical questions such as: What is the mechanism underlying circulatory disorders? What are the underlying causes of this phenomenon? Thus, the clinical need serves as the primary determinant for the timing of the ultrasound examination, scope and content of the scan, selection of an appropriate protocol, and interpretation of the findings to guide treatment decisions. This foundation is necessary for interpretation but also serves as a reminder to clinicians that medical interventions should focus on solving clinical problems rather than treating ultrasound signs; that is, the improvement of a patient’s clinical condition must remain the goal of treatment. Protocol The second step involves selecting an appropriate examination protocol based on clinical presentation and context. Protocol-based examinations help avoid overreliance on a single view and offer a more efficient approach for obtaining comprehensive information. However, as examinations progress and clinical issues become more clearly defined, the protocol should be dynamically adjusted to include focused assessments tailored to specific conditions. For example, selecting the Critical Consultation Ultrasonic Examination protocol during emergency consultations helps to rapidly narrow down the causes of acute cardiorespiratory compromise. The Focused Echocardiographic Evaluation in Life Support protocol assists in distinguishing true pulseless electrical activity (PEA) from pseudo-PEA during cardiopulmonary resuscitation and identifying common causes of pseudo-PEA. Therefore, the choice of the examination protocol depends on the specific clinical scenario; that is, a scenario-driven protocol selection. View quality control View quality control is conducted during the acquisition of sections. Rapid-view acquisition is a fundamental requirement for bedside ultrasound. Standardized two-dimensional views reflect three-dimensional organ pathophysiology more accurately and enhance operator consistency and comparability. Nonstandard ultrasound images can lead to misinterpretation; therefore, the acquired views must meet clearly defined standards. Moreover, the production of stable and high-quality images can enable clinicians to perform more accurate evaluations. View quality control should adhere to the Fast, Excellent, Stable, and Standard principles.10 To achieve Fast, Excellent, Stable, and Standard image acquisition, it is essential to master the anatomical structure of organs and the fundamental techniques of image acquisition, including sliding, rocking, tilting, and rotation. Additionally, securing the probe using the hypothenar against the chest wall and other stabilization techniques can enhance image quality. Fine-tuning the gain and optimizing the depth settings are crucial technical adjustments that contribute to superior image clarity. Continuous practice and experience are vital to quickly obtain satisfactory images. Approach Following the protocol-based acquisition of the view, interpretation proceeds through an integration-centered approach. The first step in interpretation is to identify and record objective ultrasonographic abnormalities. For each view of the heart, assessments can be made regarding the “chamber,” “wall,” “valve,” and “flow.” This can involve probing questions such as, Is the heart chamber enlarged, reduced, or morphologically changed? Will thickening or thinning occur? Is wall motion increased or decreased, or was segmental dyskinesia or asynchrony present? Are stenosis, incompetence, vegetation, or increased echogenicity present in the valve? Forward-flow acceleration or backflow for the inferior vena cava? Is the long axis wide or slender, the short axis round or drop-shaped, and how does it vary with respiration? Additionally, quantitative measurements should be performed when necessary. For each view of the lung, the main focus is on pleural analysis and identification of pulmonary ultrasound signs, with specific rules for views of other areas. Once the objective judgment of ultrasound abnormalities has been completed and recorded, the analysis should be integrated with the clinical information by following a specific pathway guided by the clinical question. For example, in a patient presenting with shock, the interpretation must be assessed alongside ultrasound abnormalities in the following order: Is there insufficient right heart reflux or overload? What is right heart function and afterload? How does this affect the left heart (e.g., the ventricular septum)? What is the diastolic function of the left heart and the left atrial pressure? Is there any impairment in left heart contraction? What is the degree of impairment and type of abnormal systolic pattern present? Is there a reduction in the peripheral resistance? What are the abnormalities and degree of pulmonary fluid and renal blood flow? When integrated through a six-step hemodynamic approach, the interpretation of these findings yields a hemodynamic phenotype. Similarly, lung ultrasound involves interpreting ultrasonic signs in various regions as pathological and physiological changes in the air–water distribution, which are then combined to form a pulmonary air–water distribution phenotype. The three-column approach, which transforms ultrasound visualization data into critical care clinical information through discrimination, interpretation, and phenotype analysis, represents a standardized pathway for constructing a cardiopulmonary ultrasound phenotype interpretation template (Table 1). Hierarchical analysis of the condition by integrating clinical information can elucidate the mechanisms and pathways of disease deterioration, thereby facilitating the development of targeted treatment plans. This process is treatment-driven; that is, an analysis of a patient’s condition guided by therapeutic objectives. Table 1 - Illustration of the three-column approach through a case study. Step 1: discrimination Step 2: interpretation Step 3: phenotype Intravenous volume Diameter: 2.2 cm, short axis: oval, 2.85 cm × 1.74 cm; transhepatic measurement of IVC diameter: 2.02 cm, small variability, hepatic vein: S>D, portal vein PI: <30%, right renal vein: discontinuous Venous volume overload Venous volume overloadCardiac hypodynamia, low stroke volumeLow tension, high resistance, high leakageInterstitial deflation of nongravity-dependent regions of the lung, and solid-degeneration deflation of gravity-dependent regions Right heart (size, motion, interventricular septum) Enlarged right heart with driving enhancement and mild tricuspid regurgitation, pulmonary artery trunk width 2.83 cm; TAPSE 0.97 cm Left heart diastole E peak: 55.61 cm/second, A peak: 40.78 cm/second, E/A: 1.36, mural E/e’= 10.17, diaphragmatic E/e’= 9.97 Normal left heart diastolic function Left atrial pressure The left atrium is normal in size Normalcy Left heart asystole MAPSE: 1.01 cm, LV EF-M 44%; segmental dyskinesia Hypodynamic Left ventricular output VTI: 9.8 cm; CO: 2.3 L/minute Low stroke volume, low CO Peripheral vasculature (tension, resistance) Snuff-box artery RI: 1.07, norepinephrine:1.0 µg/kg minute Low tension, high resistance Lung Left lung zone 1 B2; zone 2 B2; zone 3 B2; zone 4 B2+C2; zone 5 B2+C1; zone 6 B2+C1; right lung zone 1 B2; zone 2 B2; zone 3 B2; zone 4 B2; zone 5 B2+C2; zone 6 B2+C2 Ultrasound interstitial lung syndrome + gravity-dependent zone solid lesions CO indicates cardiac output; E/A, early to late diastolic mitral inflow velocity ratio; E/e’, early mitral inflow velocity to early diastolic mitral annular velocity ratio; IVC, inferior vena cava; LV EF-M, left ventricular ejection fraction by m-mode; MAPSE, mitral annular plane systolic excursion; PI, pulsatility index; RI, resistive index; TAPSE, tricuspid annular plane systolic excursion; VTI, velocity time integral. Practice workflow Upon completion of the foundational diagnostic elements, a structured practice workflow must be implemented to enhance the standardization, homogeneity, safety of treatment, efficiency, and quality of care. For example, in the workflow for acute respiratory and circulatory disorders, PIEPEAR7 includes components like etiological treatment, treatment at the pathophysiological level, and feedback. The practice workflow is the concrete application of CPVAP principles within a specific diagnostic and therapeutic context. Each practice workflow targets a specific scenario or disease determined through clinical discrimination. The primary task in diagnosis and treatment is the collection of comprehensive information. Ultrasonographic visual information collectively comprises ultrasound image acquisition, view quality control, and image interpretation centered on diagnostic and therapeutic tasks. The pathway for generating this information is essentially the mindset chain for clinical interpretation of ultrasound data, with the three-column approach serving as a concrete manifestation of this mindset chain. Ultrasonographic visual information must be integrated with clinical data to generate a portrait of the condition, followed by a hierarchical treatment. This process must adhere to standardized procedures; thus, the practice workflow is essentially a standardized behavioral guidance. CCUSG training View acquisition is a fundamental component of training. The ability to accurately identify ultrasound abnormalities and correlate these with clinical questions is critical. Therefore, the CCUSG training course emphasizes the identification of ultrasound abnormalities, reinforced by the accumulation of cases. A separate course on clinical cases, designed to train students to formulate questions, interpret images in the context of clinical information, and make diagnostic decisions, is also available. A specified number of cases is required for assessment. Overall, the CCUSG’s training program on CCUS (Figure 1) includes lectures (online/offline), hands-on skills training (offline only), visual accumulation practice (ultrasound image recognition and clinical interpretation training, online/offline), interactive case-based practical skills training (online/offline), follow-up offline training for specific diagnosis and treatment, and continuous quality improvement. The lectures cover topics such as basic introductions to critical illnesses and the fundamental theory of ultrasound. Operational skills training includes image acquisition techniques and specifications, as well as image acquisition exercises. Visual accumulation practice includes identifying and recording ultrasound abnormalities and interpreting images with clinical information through a material library. Case discussions included clinical analysis, diagnosis, and treatment decision-making exercises. The training process consists of short sessions, case exercises, and competency identification. Assessment and competency identification should also be based on the CPVAP components. Taking the CCUSG Fundamental Course as an example, the training approach is illustrated as follows: Within the 2-day curriculum Day 1 morning session C (clinical analysis) Lectures on fundamental critical care theories, covering disease mechanisms and diagnostic treatment principles, and equipping trainees with clinical discrimination skills. P (protocol) and V (view) Instructions on core ultrasound physics and cardiopulmonary scanning techniques, reinforced through hands-on training to master protocol-based examinations and view quality control. Day 1 afternoon session A (approach) Standardized pathway training (chronic cardiac substrate → IVC → right ventricular function → left ventricular diastolic/systolic function → peripheral vascular resistance → lung ultrasound [“six-step method”]), enabling systematic interpretation to derive hemodynamic conclusions. Day 2 P (practice workflow) Real-time telerounding case demonstrations illustrating ultrasound-integrated diagnosis and treatment workflows. Postcourse Trainees conduct mentored clinical practice under certified instructors and submit standardized cases by applying CPVAP principles. Summary CCUS has been widely recognized by clinicians as a visual and convenient tool for obtaining patient information. The CPVAP principle, which serves as a foundational framework for CCUS applications, consistently enables physicians to adopt a problem-oriented approach, standardize ultrasound utilization, and address the core clinical challenges in contemporary critical care practice. However, mastery of this principle varies among clinicians with divergent competency levels, and scenario-specific adaptations are warranted. Our regional cross-sectional survey revealed that among medical personnel utilizing the CPVAP principle for assessing critical conditions (e.g., shock, ARDS, sepsis, and pancreatitis), over 50% demonstrated >50% alteration rates in clinical management decisions.11 Therefore, the acquisition of high-quality images and the standardization of clinical applications must be further enhanced. Furthermore, the CPVAP-guided training model accommodates medical personnel with diverse fundamental competencies and clinical needs. Future studies should evaluate the long-term impact of CPVAP-based training on practitioner proficiency and patient care outcomes, thereby validating the principle’s sustained value. Through concerted efforts, CCUS will contribute to saving lives. Acknowledgments We would like to thank all members of the Chinese Critical Ultrasound Study Group (CCUSG) represented by Wanhong Yin, Yangong Chao, Wei He for their efforts in developing critical care medicine in China. We thank Mo Zhou from the West China Hospital/West China School of Medicine, Sichuan University, for editing the English text of the draft of this manuscript. Conflicts of interest The authors declare that they have no conflicts of interest with regard to the content of this report. Author contributions W.Y. contributed to the conception and design of this study. X.Z., W.Y., and X.L. reviewed and drafted the manuscript. W.Y. and Y.C. revised the manuscript. All authors provided their final approval for the submission of the present version.