Transoesophageal Ultrasound Assessment of Lung Aeration in Patients With Acute Respiratory Distress Syndrome

Diagnosis of Lung Abscess and Pancreatic Collection Using Transesophageal and Transgastric Point-of-Care Ultrasound in a Critically Ill Patient

Effectively managing critically ill septic patients requires careful utilization of imaging techniques. While point-of-care ultrasound (POCUS) is invaluable in the ICU, it faces challenges with conventional transcutaneous ultrasound, especially in obese patients. A 22-year-old obese female presented with abdominal pain and renal dysfunction. Abdominal CT confirmed acute biliary pancreatitis, progressing to respiratory failure. Transesophageal and transgastric ultrasound revealed a pulmonary abscess and peripancreatic collection. Expectant management of the lung abscess and percutaneous drainage of the pancreatic collection led to successful recovery. This case highlights POCUS's pivotal role in timely diagnosis, particularly in severe pancreatitis, showcasing its versatility in critical care.

Focused transoesophageal TOE (fTOE): A new accreditation pathway

The concept of a focused ultrasound study to identify sources of haemodynamic instability has revolutionized patient care. Point-of-care ultrasound (POCUS) using transthoracic scanning protocols, such as FUSIC Heart, has empowered non-cardiologists to rapidly identify and treat the major causes of haemodynamic instability. There are, however, circumstances when a transoesphageal, rather than transthoracic approach, may be preferrable. Due to the close anatomical proximity between the oesophagus, stomach and heart, a transoesphageal echocardiogram (TOE) can potentially overcome many of the limitations encountered in patients with poor transthoracic ultrasound windows. These are typically patients with severe obesity, chest wall injuries, inability to lie in the left lateral decubitus position and those receiving high levels of positive airway pressure. In 2022, to provide all acute care practitioners with the opportunity to acquire competency in focused TOE, the Intensive Care Society (ICS) and Association of Anaesthetists (AA) launched a new accreditation pathway, known as Focused Transoesophageal Echo (fTOE). The aim of fTOE is to provide the practitioner with the necessary information to identify the aetiology of haemodynamic instability. Focused TOE can be taught in a shorter period of time than comprehensive and teaching programmes are achievable with support from cardiothoracic anaesthetists, intensivists and cardiologists. Registration for fTOE accreditation requires registration via the ICS website. Learning material include theoretical modules, clinical cases and multiple-choice questions. Fifty fTOE examinations are required for the logbook, and these must cover a range of pathology, including ventricular dysfunction, pericardial effusion, tamponade, pleural effusion and low preload. The final practical assessment may be undertaken when the supervisors deem the candidate's knowledge and skills consistent with that required for independent practice. After the practitioner has been accredited in fTOE, they must maintain knowledge and competence through relevant continuing medical education. Accreditation in fTOE represents a joint venture between the ICS and AA and is endorsed by Association of Cardiothoracic Anaesthesia and Critical care (ACTACC). The process is led by TOE experts, and represents a valuable expansion in the armamentarium of acute care practitioners to assess haemodynamically unstable patients.

Respiratory effects of lung recruitment maneuvers depend on the recruitment-to-inflation ratio in patients with COVID-19-related acute respiratory distress syndrome

Background

In the context of acute respiratory distress syndrome (ARDS), the response to lung recruitment maneuvers (LRMs) varies considerably from one patient to another and so is difficult to predict. The aim of the study was to determine whether or not the recruitment-to-inflation (R/I) ratio could differentiate between patients according to the change in lung mechanics during the LRM.

Methods

We evaluated the changes in gas exchange and respiratory mechanics induced by a stepwise LRM at a constant driving pressure of 15 cmH₂O during pressure-controlled ventilation. We assessed lung recruitability by measuring the R/I ratio. Patients were dichotomized with regard to the median R/I ratio.

Results

We included 30 patients with moderate-to-severe ARDS and a median [interquartile range] R/I ratio of 0.62 [0.42–0.83]. After the LRM, patients with high recruitability (R/I ratio ≥ 0.62) presented an improvement in the P_aO₂/F_iO₂ ratio, due to significant increase in respiratory system compliance (33 [27–42] vs. 42 [35–60] mL/cmH₂O; p < 0.001). In low recruitability patients (R/I < 0.62), the increase in P_aO₂/F_iO₂ ratio was associated with a significant decrease in pulse pressure as a surrogate of cardiac output (70 [55–85] vs. 50 [51–67] mmHg; p = 0.01) but not with a significant change in respiratory system compliance (33 [24–47] vs. 35 [25–47] mL/cmH₂O; p = 0.74).

Conclusion

After the LRM, patients with high recruitability presented a significant increase in respiratory system compliance (indicating a gain in ventilated area), while those with low recruitability presented a decrease in pulse pressure suggesting a drop in cardiac output and therefore in intrapulmonary shunt.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03876-z.