Transvenous Phrenic Nerve Stimulation: A Novel Therapy Gathering Pace

Extracellular Matrix as a Driver of Chronic Lung Diseases

The extracellular matrix (ECM) is not just a three-dimensional scaffold that provides stable support for all cells in the lungs, but also an important component of chronic fibrotic airway, vascular, and interstitial diseases. It is a bioactive entity that is dynamically modulated during tissue homeostasis and disease, that controls structural and immune cell functions and drug responses, and that can release fragments that have biological activity and that can be used to monitor disease activity. There is a growing recognition of the importance of considering ECM changes in chronic airway, vascular, and interstitial diseases, including 1) compositional changes, 2) structural and organizational changes, and 3) mechanical changes and how these affect disease pathogenesis. As altered ECM biology is an important component of many lung diseases, disease models must incorporate this factor to fully recapitulate disease-driver pathways and to study potential novel therapeutic interventions. Although novel models are evolving that capture some or all of the elements of the altered ECM microenvironment in lung diseases, opportunities exist to more fully understand cell-ECM interactions that will help devise future therapeutic targets to restore function in chronic lung diseases. In this perspective article, we review evolving knowledge about the ECM's role in homeostasis and disease in the lung.

[Electromagnetic stimulation in diaphragm dysfunction: repetitive peripheral magnetic stimulation as a method of choice during the rehabilitation period after stroke. (Literature review)]

Diaphragm dysfunction develops in central nervous system damage, chest injuries, complications of cardiac surgery, long-term artificial lung ventilation, respiratory diseases. Anatomical morphological features of phrenic nerves allow to effectively use electromagnetic stimulation methods for functional recovery of the diaphragm in different pathological conditions. Invasive and non-invasive, electric and magnetic methods of stimulation are used depending on the severity of manifestations of the diaphragm dysfunction and its genesis.

OBJECTIVE

To perform a review and comparison of modern methods of electromagnetic stimulation of the diaphragm; to determine the role of repetitive peripheral magnetic stimulation (rPMS) in the diaphragm dysfunction as a result of stroke.

MATERIAL AND METHODS

An analysis of publications from the Pubmed and Elibrary databases for 2008-2024 years was conducted. The search was done by the following keywords: diaphragm dysfunction, repetitive peripheral magnetic stimulation of phrenic nerve, stroke, hemiparesis.

RESULTS

There is a real possibility of effective diaphragm stimulation for recovery of its function due to the innervation of the diaphragm strictly by the phrenic nerves, their large diameter, presence of myelinated fibers as well as anatomical location of the phrenic nerves. Direct electric stimulation of the phrenic nerve is usually applied in the case of long-term continuous support of respiratory function. Non-invasive techniques of electric or magnetic stimulation of the phrenic nerve or directly of the diaphragmatic muscle are used in the case of temporary respiratory support or recovery of diaphragm function. The motor neurons of the brain and peripheral nerves are activated, thus a peak strength of the variable magnetic field usually reachs 1-2 T in rPMS. Application of rPMS affects the efferent nerve fibers, causing muscle contractions, and activates sensory afferent fibers, creating a stimulating effect on the superjacent nervous structures. It is advisable to use rPMS of the phrenic nerve in the cervical segment or rPMS of one of the segments of the diaphragmatic muscle in the case of unilateral diaphragm lesion during the recovery period after stroke. It is important to consider the frequency of exposure in the 10-30 Hz range, the closest location of the coil to the stimulation area, the choice of the coil shape depending on the localization when adjusting parameters of rPMS.

CONCLUSION

The use of rPMS of the phrenic nerve and diaphragm allows to preserve and recover motor and contractile functions of the diaphragm in different pathological conditions, including its unilateral lesion as a result of stroke. The method of rPMS of the phrenic nerves has a number of advantages over electric stimulation and repetitive transcranial magnetic stimulation, since it allows to achieve an effective motor response with less intensity of exposure, is painless and non-contact, better tolerated by patients.

Phrenic Nerve Stimulation for Acute Respiratory Failure

Diaphragm inactivity during invasive mechanical ventilation leads to diaphragm atrophy and weakness, hemodynamic instability, and ventilatory heterogeneity. Absent respiratory drive and effort can, therefore, worsen injury to both lung and diaphragm and is a major cause of failure to wean. Phrenic nerve stimulation (PNS) can maintain controlled levels of diaphragm activity independent of intrinsic drive and as such may offer a promising approach to achieving lung and diaphragm protective ventilatory targets. Whereas PNS has an established role in the management of chronic respiratory failure, there is emerging interest in how its multisystem putative benefits may be temporarily harnessed in the management of invasively ventilated patients with acute respiratory failure.