Like the heart, the diaphragm is a muscle of the body that never rests. This flat, dome-shaped muscle sits underneath the lungs and helps us breathe, contracting and flattening to draw air into the lungs, and relaxing to push air out. But mechanical ventilation for critically ill patients in intensive care, such as those with severe cases of COVID-19, can weaken the diaphragm and make it hard for patients to breathe on their own again.
“A big problem with inflating the lungs using positive pressure to deliver oxygen is that high pressure causes ventilator-induced lung injury, and in COVID-19 patients this may compound the lung damage caused by the virus,” said Andy Hoffer, professor of biomedical physiology and kinesiology at Simon Fraser University in a press release.
Not only can a ventilator damage the lungs themselves, but the assistance reduces the activity of the diaphragm, and this can weaken it. Within three days of being placed on a ventilator, a patient’s diaphragm can atrophy to half of its normal size. About a third of patients can’t be weaned off of mechanical ventilation.
Hoffer is the lead inventor of a device that could help keep the diaphragm strong and active during mechanical ventilation. His spinoff company, Lungpacer Medical, has obtained emergency use authorization from the FDA to use its diaphragm pacing therapy in the United States during the pandemic.
Normally, the diaphragm is stimulated by the phrenic nerves, a pair of nerves that run down the neck and between the lungs to arrive at the diaphragm. The Lungpacer Diaphragm Pacing Therapy System delivers rhythmic electrical impulses to the diaphragm through the phrenic nerves, reminding the diaphragm to keep moving.
The system is inserted in a minimally-invasive procedure that threads a catheter through the subclavian vein, a large vein that can be accessed through the left shoulder, to the centre of the chest. Here the Lungpacer device can stimulate the phrenic nerves through the vein wall.
A sensor connected to the ventilator helps synchronize the electrical impulses to that the two devices can work together. Making use of the diaphragm also decreases the air pressure requirements for mechanical ventilation by 20-30 percent.
“Pacing the diaphragm distributes the breathed oxygen more evenly throughout the lungs and this helps protect the tissue from mechanical injury,” added Hoffer.
Notably, Lungpacer’s use of transvenous stimulation sets it apart from existing devices on the market. Other devices require surgical implantation, which can be dangerous for critically ill patients.
Without drug options to help treat COVID-19, many patients with severe cases need help to keep breathing. Around the world, hospitals are racing to acquire more ventilators to meet the emerging demand. Lungpacer’s technology not only helps improve patient outcomes, it also makes more ventilators available by decreasing the time to wean a patient back to breathing on their own.
The diaphragm is meant to move, and Lungpacer helps keep it in the game when COVID-19 patients need every available resource to keep breathing.