Feasibility of Transvenous Phrenic Nerve Stimulation for Diaphragm Protection in Acute Respiratory Failure

The diaphragm is the main muscle of breathing and for most of us therefore is continuously being used (and hence exercised) when in health. When people are unwell with severe breathing difficulties to the degree that their lungs are needing a lot of support from a breathing machine (ventilator) in the intensive care unit (ICU), or are recovering from major lung/chest surgery on a ventilator in ICU, the diaphragm can quickly start to weaken from its inactivity. This means that even when starting to recover from the underlying medical problem, or from the surgery itself, the diaphragm may be unable perform well enough to take over the work of breathing once again. This can lead to not only longer times on the ventilator (time to gradually rebuild diaphragm strength by rehabilitation and physiotherapy) but also therefore longer times in ICU and in hospital with the risk of complications that can be associated with this. Stimulating the diaphragm by use of a pacemaker (electrical stimulation) is an established treatment for a number of patients with certain types of long-term breathing problems. These pacemakers are permanent and are inserted by invasive surgical methods. More recently however, there have also been a number of studies looking to see if it is possible to safely, temporarily and less invasively stimulate the diaphragm of patients who only have temporary diaphragm inactivity. This has been done either during surgery or during their intensive care stay. A number of methods of temporarily stimulating the diaphragm have been looked at, but the simplest has been to integrate the function of stimulating the nerves (that ultimately control the diaphragm) with a catheter that is frequently placed into a vein in the neck to enable delivery of medications during surgery and in ICU.