For Healthcare Professionals
There is good evidence based on animal and human physiological studies and large-scale clinical series that exovent may provide an additional option for the clinical management of pneumonia caused by COVID-19 virus, when additional help with breathing is needed.
Some patients with COVID-19 have difficulty sustaining high enough oxygen levels in the blood and they are given additional oxygen to breathe through a face-mask or nasal tubes.
If that is insufficient they can have the oxygen delivered via a tightly fitting mask over the face which delivers Continuous Positive Airways Pressure (CPAP) into their lungs which helps the lungs open up when breathing in (inspiration) and prevents them collapsing totally when breathing out (expiration). If that is insufficient the next stage, which may be offered, is to replace their own spontaneous breathing with full mechanical ventilation. This is done via a tube placed in the windpipe (intubation). This is connected to a ventilator which blows oxygen into the lungs. This is Positive Pressure Ventilation (PPV). These sophisticated ventilators can vary the amount of pressure provided on inspiration to suit the patients’ needs and on expiration to help prevent the lungs fully collapsing which is called Positive End-Expiratory Pressure (PEEP). Patients usually require heavy sedation and often muscle relaxants.
- exovent devices work differently and provides respiratory support by creating a negative pressure around the chest and abdomen. This can be done by creating a steady negative pressure around the outside of the chest (extra-thoracic) and abdomen whilst the patient breathes spontaneously. This is called Continuous Negative Extra-thoracic Pressure (CNEP). If more help is needed, the pressure can be increased and provided in waves to take over the effort of breathing. This is called negative pressure ventilation (NPV).
- exovent devices only covers the torso so monitoring is still possible. Patients can move their head and legs freely, and their arms within the ventilator casing. Oxygen can be delivered directly to the patient by mask or tubing as required. People can be treated in exovent in a variety of positions to suit. For example: while lying on their back (supine), semi-sitting, whilst lying on their front (prone) or on their side. Intensive care specialists have suggested that routinely changing the position of patients with COVID19 pneumonia may be helpful.
- More negative pressure is provided on inspiration, and a smaller negative pressure is maintained on expiration to prevent the lungs from totally collapsing. This is called Negative End-Expiratory Pressure (NEEP) and can be considered as equivalent to PEEP.
- exovent devices are less likely to cause a pneumothorax (burst lung) as negative pressure ventilation produces less micro-trauma to the lung.
- Studies in a non-COVID but very severe lung disease (ARDS) have shown that negative pressure ventilation (NPV) gives equal or improved gas transfer compared to standard positive pressure ventilation (PPV +PEEP).
- exovent devices are non-invasive, which means that it is not necessary to have a tube in the windpipe (intubation), so there is no need for sedation or muscle paralysis medication. Instead, people in the an exovent device can remain conscious, take medication and nutrition by mouth, and talk to loved ones on the phone.
We predict that exovent will help the heart’s efficiency (this will be measured in upcoming clinical trials), which is particularly important because COVID 19 may make heart function worse. Conventional positive pressure ventilation squeezes the heart and veins in the chest, and therefore can actually reduce cardiac function.
Being non-invasive and simple to use, exovent could be used in intensive care or on a high dependency ward.
Find out about the application of negative pressure on the disease states that cause respiratory distress and its clinical benefits. A comparison to other ventilation techniques and modalities, a brief history, and our thoughts on the role of NPV in the COVID-19 pandemic.
Read out Medical Review document which is regularly updated by it's authors Dr Malcolm Coulthard and Professor David Howard.