Unlocking the Power of Diaphragm Ultrasound After Cardiac Surgery: A Game-Changer in Postoperative Care

Understanding a Hidden Complication of Cardiac Surgery

Cardiac surgery is a life-saving intervention, yet it comes with risks that can complicate recovery. A recent study titled “Imaging of the Diaphragm Following Cardiac Surgery: Focus on Ultrasonographic Assessment” sheds light on the critical role of diaphragm ultrasound in identifying and managing post-operative respiratory complications in cardiac surgery patients. 

Diaphragm dysfunction is a condition that impacts up to 75% of post-operative cardiac surgery patients, according to some studies. This dysfunction, often caused by phrenic nerve injury or prolonged mechanical ventilation, can delay extubation, prolong ICU stays, and significantly hinder the patient’s rehabilitation process.

Diaphragm dysfunction isn’t always easy to detect. Patients may remain asymptomatic or exhibit subtle signs like exertional dyspnea, especially if the dysfunction is unilateral. In more severe cases, bilateral dysfunction can lead to acute respiratory failure. Complicating matters further, factors like obesity, chronic obstructive pulmonary disease (COPD), and arterial hypertension can exacerbate symptoms, making early and accurate diagnosis critical.

Why Diaphragm Imaging Matters in Recovery

Accurate and timely imaging is crucial for diagnosing diaphragmatic impairment and enhancing patient outcomes. The gold standard, transdiaphragmatic pressure measurement, while effective, is invasive and impractical for routine use. That’s where diaphragm ultrasound shines.

Ultrasonography provides a non-invasive, bedside, and real-time method of assessing diaphragm function. It is particularly useful in both the intensive care unit (ICU) and the cardiovascular rehabilitation (CR) setting. The technique enables clinicians to assess key parameters, including diaphragm thickness, thickening fraction (TF), excursion, and contraction velocity.

Multiple ultrasonographic views, such as the anterior subcostal and intercostal approaches, offer flexible ways to assess both hemidiaphragms. For instance, a diaphragm excursion of less than 2 cm or a TF of less than 20% strongly suggests dysfunction. This real-time insight enables care teams to tailor weaning strategies and respiratory therapy plans to the individual needs of patients recovering from cardiac surgery.

The Link Between Cardiac Surgery and Diaphragm Dysfunction

Procedures like coronary artery bypass grafting (CABG) are well-known culprits, often due to phrenic nerve damage from internal mammary artery harvesting. However, the problem isn’t limited to CABG. Other cardiac surgeries and techniques, such as cardiac cooling with topical ice slush, can also trigger a phenomenon known as “diaphragmatic stunning.” This transient yet significant impairment starts around 48 hours post-surgery and can persist for days, affecting up to 36% of patients severely enough to delay ventilator weaning.

Moreover, ventilation-induced diaphragm dysfunction (VIDD) adds another layer of complexity to the issue. Occurring in over half of intubated patients within 24 hours, VIDD is associated with muscle disuse atrophy, oxidative stress, and weakened contraction. In these cases, diaphragm ultrasound has proven invaluable, offering predictive insights into weaning success through indices like the diaphragmatic Rapid Shallow Breathing Index (dRSBI).

Beyond the ICU: Diaphragm Ultrasound in Rehabilitation

Even after ICU discharge, diaphragm dysfunction can linger and limit recovery. Studies show that nearly 70% of patients entering cardiovascular rehab post-cardiac surgery present with diaphragm dysfunction, impacting outcomes like the 6-minute walk test (6MWT). Ultrasound becomes an ongoing tool here, monitoring improvements, guiding therapy, and evaluating readiness for increased physical activity.

This continuity of care emphasizes the need for a workforce trained not only in traditional sonography but also in diaphragm imaging, specifically tailored to post-cardiac surgery care. Yet many institutions lack access to patients, pathology, and qualified instructors needed to support such specialized training.

How SonoSim Supports Ultrasound Education

Ultrasound plays a critical role in evaluating diaphragm function, particularly in the context of post-cardiac surgery recovery. While diaphragm ultrasound is a specialized application, the foundational skills that support it—like cardiac imaging, pulmonary ultrasound, and respiratory assessment—are all essential components of a clinician’s toolkit.

SonoSim offers a robust training ecosystem that helps learners develop and refine these core ultrasound competencies. With hands-on scanning practice using real pathologic cases, expert-narrated instruction, and performance feedback, users can strengthen the skills they’ll rely on at the bedside. Whether you're managing ICU patients or guiding post-op recovery in rehab settings, SonoSim prepares you to approach complex respiratory assessments with greater confidence.

Build your ultrasound fluency with SonoSim's cardiac and pulmonary training modules, and be better equipped to integrate diaphragm assessment into your clinical decision-making.