Diaphragmatic paralysis pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:
Overview
The exact pathogenesis of [disease name] is not fully understood.
OR
It is thought that [disease name] is the result of / is mediated by / is produced by / is caused by either [hypothesis 1], [hypothesis 2], or [hypothesis 3].
OR
[Pathogen name] is usually transmitted via the [transmission route] route to the human host.
OR
Following transmission/ingestion, the [pathogen] uses the [entry site] to invade the [cell name] cell.
OR
[Disease or malignancy name] arises from [cell name]s, which are [cell type] cells that are normally involved in [function of cells].
OR
The progression to [disease name] usually involves the [molecular pathway].
OR
The pathophysiology of [disease/malignancy] depends on the histological subtype.
Pathophysiology
The main muscles of inspiration:
- Diaphragm (most important)
- Scalenes
- External intercostals,
- Sternomastoids.
The muscles of expiration:
- Internal intercostals
- Muscles of the abdominal wall
- Rectus abdominus
- Internal and external obliques
- Transversus abdominus
Pathogenesis
- The diaphragm is the musculo-fibrous membrane. It has two parts: non-contractile central fibrous and peripheral muscular components. [1]
- Peripheral muscular section has two fibers:
- Type 1: slow and fatigue resistant fibers: play roles in low intensity, continual cycle of breathing
- Type 2: fast fibers: play roles in rapid and intense situations such as:
- Talking
- Singing,
- Sneezing,
- Defecation
- Acute hyperventilation
The diaphragm create negative intrathoracic pressure and facilitates movement of air into the lungs. It is innervated by cervical nerve roots ( C3-C5 ) via the phrenic nerves.
Diaphragmatic paralyses can be unilateral or bilateral according to involvemnet of one or two leaflets of diaphragm.
Diaphragmatic paralysis is an uncommon cause of dyspnea.
It is understood that diaphragmatic paralysis is the result of paralysis of ( C3-C5 ).
In the case of unilateral diaphragm paralysis, it is compensated by other hemidiaphragm or accessory muscles of respiration.
Depending upon the degree of diaphragmatic compromise, the other hemidiaphragm or the accessory muscles of respiration assume some or all the work of breathing. This compensation is achieved by more intense contraction of the accessory muscles and by the progressive recruitment of other, less important accessory inspiratory muscles (sternomastoid, trapezius, latissimus dorsi, and pectoralis minor and major). Patients may also recruit abdominal muscles to augment exhalation, which forces the respiratory system to a lower volume (below functional residual capacity) at end-exhalation. The low volume increases the elastic recoil energy in the chest wall, assisting the next inspiration.
In the case of unilateral diaphragm paralysis, the normal contralateral hemidiaphragm is able to generate enough negative pleural pressure to promote inspiration. The negative intrapleural pressure draws air in through the trachea, but also draws some air across the chest from the side of the paralyzed hemidiaphragm. As the paralyzed hemidiaphragm is pliable and mobile, it moves up into the chest (paradoxically) during inspiration. The movement of air from one lung to the other increases the work of breathing without improving gas exchange. However, over time (approximately one year) the paralyzed hemidiaphragm becomes less pliant and less responsive to the pull of negative pleural pressure from the contralateral side. The decreased compliance of the paralyzed hemidiaphragm reduces the amount of airflow from the paralyzed to the normal side. Thus, the respiratory impairment of unilateral diaphragm paralysis tends to improve even without restoration of phrenic nerve function.
- It is understood that [disease name] is the result of / is mediated by / is produced by / is caused by either [hypothesis 1], [hypothesis 2], or [hypothesis 3].
- [Pathogen name] is usually transmitted via the [transmission route] route to the human host.
- Following transmission/ingestion, the [pathogen] uses the [entry site] to invade the [cell name] cell.
- [Disease or malignancy name] arises from [cell name]s, which are [cell type] cells that are normally involved in [function of cells].
- The progression to [disease name] usually involves the [molecular pathway].
- The pathophysiology of [disease/malignancy] depends on the histological subtype.
Genetics
- [Disease name] is transmitted in [mode of genetic transmission] pattern.
- Genes involved in the pathogenesis of [disease name] include [gene1], [gene2], and [gene3].
- The development of [disease name] is the result of multiple genetic mutations.
Associated Conditions
Gross Pathology
- On gross pathology, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].
Microscopic Pathology
- On microscopic histopathological analysis, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].