Optimising lung volumes with the MetaNeb intermittent oscilation system whilst supported by ECMO

Purpose

Extracorporeal membrane oxygenation (ECMO) provides prolonged support to a person's heart and lungs in circumstances where they are unable to provide adequate perfusion and gas exchange to sustain life. ECMO is a high risk procedure with an increased chance of complication with increasing duration of support.

Atelectasis and consolidation are common side effects as the lungs become hyper-perfused and secretions become gelatinous. Ensuring that a patient´s lungs are in as optimal a condition as possible (expanded and clear from secretions) gives them a greater chance successful decannulated from ECMO. Balancing the risk of possible bleeding from the lungs with conventional physiotherapy techniques such as bagging and manual techniques and the need to optimise the lungs is a challenge.

The MetaNeb system is an emerging method of airway clearance which combines a delivery of continuous high or low frequency oscilation which can mobilise secretions and reverse atelectasis.

Approach

This case report outlines the use of the MetaNeb system in the management of a 2 month old baby with a complex congenital cardiac condition who was supported by ECMO for 20 days.

He presented to our unit on day 10 of his ECMO run. His chest x-ray (CXR) showed bilateral whiteouts. CT showed consolidation of both lungs. He had tidal volumes of less than 1ml/kg, was quiet throughout on auscultation and had stiff lungs on manual hyperinflation trial and no visible chest movement.

He was on 20 parts per million (ppm) of nitric oxide to manage his pulmonary hypertension and required 60-70% of oxygen to maintain normal saturations. A bronchoscopy showed inflamed airways with gelatinous secretions and some signs of bleeding from fragile airways.

His cardiac function had improved sufficiently to be weaned from the ECMO support however, his lungs were not in a condition to sustain life and needed to be optimised to ensure sufficient gas exchange was possible without ECMO support.

Treatment using the MetaNeb was commenced and delivered 4 times daily alongside suction. The MetaNeb was placed within the ventilator circuit as close to the patient as possible. This did not affect the flow of nitric oxide to the patient.

Outcomes

Initially the patient was treated in supine and tolerated 3 minutes of fast then 3 minutes of slow oscilation prior to suctioning as his blood pressure then started to rise.

By day 2 he tolerated positional changes and 5 minute cycles of oscilation. His CXR showed some slight improvement and he was noted to have some air entry on auscultation. He continued to be seen 4 times a day for treatment.

Despite a requiring pericardial drain insertion on day 4 he went on to show marked improvements on his CXR, tidal volumes, air entry and chest movement. He was successfully decannulated from ECMO on day 7 maintaining tidal volumes at around 7ml/kg on 40% oxygen.

Airway clearance using the MetaNeb proved to be safe and effective where conventional physiotherapy caused some problems with pulmonary hypertension and bleeding.

Implications

The MetaNeb is an exciting novel way to manage high risk respiratory problems.

Funding acknowledgements

No funding has been received from any source for this work. 

Additional notes

This work was presented at Physiotherapy UK 2019