Treatment of comorbidities of ARDS and AKI

A device for treating comorbidities associated with high mortality rates

During the Covid-19 pandemic, Acute Respiratory Distress Syndrome (ARDS) came to prominence as a major cause of illness and death.  However, even before the pandemic, the condition was a significant cause of mortality resulting in around 5 deaths per 100,000 population. Amongst those dying from ARDS, a large proportion (around 70%) also suffered Acute Kidney Injury (AKI).  For those suffering the comorbidities of ARDS and AKI, the mortality rates, at up to 80%, are particularly high.  There is a need for treating these comorbidities effectively. The most effective treatment for ARDS is Extracorporeal Life Support (ECLS) in which the patient remains conscious throughout.  Conventionally, two devices are connected to the patient to treat the two conditions. Both devices take blood from the body and return it after treatment.  Device 1 is an Extracorporeal Life Support (ECLS) system which oxygenates the blood (and removes carbon dioxide).  The second device performs dialysis removing creatinine, urea and other contaminants.

The patented Haemair device is an enhancement of ECLS; it passes a two-phase gas/liquid mixture one side of a membrane and blood on the other.

The figure illustrates the principle of 2-phase mass transfer that lies at the heart of the device being developed.  Note that for flow through the very small channels employed in blood oxygenation, the plug flow illustrated is the natural flow regime.  No special provisions are needed to create the observed flow pattern.

Illustration of 2-phase mass transfer

Key:
Blood flow
 is shown as dark red and may flow L to R or R to L.
Liquid flow is shown from L to R. It flows as a series of “plugs” shown in blue.
The liquid plugs are separated by plugs of oxygen-rich gas (shown entering as a red arrow).
Oxygen diffusion from gas to blood is shown as red arrows from each gas plug to the blood.
Carbon dioxide diffusion from blood to the 2-phase flow is shown as mauve arrows.
Urea and Creatinine diffusion are shown as black arrows from blood to liquid phase plugs.

Oxygen passes from the two-phase mixture into the blood and carbon dioxide from the blood to the two-phase mixture. In addition, urea, and creatinine pass from the blood into the liquid phase of the two-phase mixture. In this way, the device acts both as an auxiliary lung and an auxiliary kidney.

Prototype devices have been built and tested in a project partially supported by Innovate UK. The photograph shows one of the prototype devices tested. The advantage of the Haemair device is that there is a much reduced volume of blood outside the body (reduced priming volume). In one pass through the device, the blood is oxygenated, dialysed, and heated.

 

Small prototype test device

We now have the capability to build devices suitable for treating the comorbidity.