Bedside diaphragmatic ultrasound used to diagnose an unexpected cause of weaning difficulty in a patient with COVID-19 pneumonitis

ABSTRACT

Introduction: Diaphragm dysfunction has been described as being responsible for weaning failure with an incidence of 23-80%. It has also been associated with difficult weaning from mechanical ventilation, prolonged intensive care unit (ICU) stay and increased ICU and hospital mortality.1 This case report describes the use of bedside ultrasound to diagnose diaphragm dysfunction, assess the severity of dysfunction, refer to specialist care and monitor disease progression in patient with COVID-19 pneumonitis with difficulty weaning from mechanical ventilation. Main body A 59 year-oldmale with no known past medical history was admitted to our ICU with respiratory failure due to COVID-19 pneumonitis. He had received continuous positive pressure ventilation with oxygen supplementation on the medical high dependency unit for 15 days prior to deteriorating and requiring invasive ventilation in ICU. In ICU, the patient was mandatory ventilated using lung protective ventilation strategies for 26 days before he was switched to pressure support ventilation for attempts to wean him from mechanical ventilation. During the initial phase of his ICU admission, he was severely hypoxaemic and required deep sedation as well as muscle relaxation for a total of 370 hours. Prone positioning was required on 4 occasions before he was stable in the supine position. Once attempts to liberate him from mechanical ventilation were being made, pressure support was gradually reduced along with PEEP and FiO2. Progress with this reduction in support was slow due to marked tachypnoea and a dyssynchronous respiratory pattern. It was also noted that he had poor air entry in his right base with corresponding right lower zone opacities on his chest x-ray. At this stage a bedside ultrasound was used to investigate the cause of weaning difficulty and consequently, the diagnosis of right diaphragmatic paralysis was made. This was a new finding, as his admission chest x-ray did not show a raised hemidiaphragm. This diagnosis led to an increased focus on physical rehabilitation and mobilisation with tolerance of his tachypnoea and respiratory pattern as we now appreciated this didn't represent ongoing underlying parenchymal lung disease. We also made a referral to the respiratory team in order to facilitate longer-term rehabilitation and follow up. The patient was successfully extubated after intense physical rehabilitation, post extubation he remained tachypnoeic and still required supplemental oxygen at the point of hospital discharge. A follow up diaphragm ultrasound 6 months after discharge did not show any improvement in the right diaphragmatic function, he remains dyspnoeic on exertion and still occasionally uses ambulatory supplemental oxygen. Conclusion: Ultrasound assessment revealed an unexpected cause of weaning difficulty in our patient that allowed us to individualise his weaning plan and rehabilitation. This case shows that bedside intensivist performed ultrasound can accurately evaluate diaphragmatic function in patients who are difficult to wean from mechanical ventilation. Brief description of ultrasound video The diaphragm was scanned using low frequency curvilinear ultrasound probe. There is lack of diaphragmatic excursion and absent thickening of the right hemidiaphragm on subcostal and intercostal views. M-mode evaluation and 'sniff test' confirms diaphragmatic paralysis.