Disorders of the Diaphragm

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Key points

  • Diaphragm dysfunction can arise from pathologic processes or injuries that affect the central nervous system, phrenic nerve, neuromuscular junction, or muscle itself.

  • The difference between upright and supine vital capacity can be used to screen for diaphragm dysfunction.

  • A definitive diagnosis can be made by measuring transdiaphragmatic pressure or by ultrasound measurements of diaphragm thickness or diaphragm dome excursion.

  • Treatment of diaphragm dysfunction depends on the underlying cause, but

Anatomy

The diaphragm is a musculotendinous, dome-shaped structure that separates the thorax from the abdomen. It is lined by peritoneum on the abdominal surface and pleura on the intrathoracic surface.1 It is the major muscle of inspiration and also acts as a barrier to the transmission of abdominal pressure to the thorax (Fig. 1). It consists of a muscular component and a central tendon. The muscular component can be subdivided into 2 parts, the costal and crural diaphragm. The costal diaphragm

Physiology

The diaphragm is the major muscle of inspiration, and its action normally accounts for approximately 70% of the inspired tidal volume.9 When the diaphragm contracts, it moves caudally, increases intraabdominal pressure, and lowers intrapleural pressure. This reduction in pleural pressure results in a decrease in intraalveolar pressure. Once intraalveolar pressure becomes subatmospheric, air moves from atmosphere into the alveoli. ensues. The lower rib cage moves outward when the diaphragm

Clinical manifestations of diaphragm dysfunction

The incidence and prevalence of diaphragm paralysis and weakness are unknown. Diaphragmatic weakness or paralysis can involve either one or both hemidiaphragms.13, 14 Individuals with unilateral diaphragmatic paralysis are generally asymptomatic unless there are comorbid conditions such as obesity or underlying lung disease. In this context, patients with unilateral diaphragm paralysis may experience dyspnea in the supine position, dyspnea with exertion, and difficulty sleeping. Individuals

Diagnosis of diaphragm dysfunction

The presence of unilateral diaphragm paralysis is often suggested by the presence of an elevated hemidiaphragm on a chest radiograph (Fig. 3). However, diaphragm eventration, subpulmonic effusion, lobar atelectasis, or a subphrenic abscess can give a similar radiographic appearance. Measurements of lung volumes in the seated position also are nonspecific, demonstrating normal lung volumes or mild restriction. Confirmation of the diagnosis is accomplished by performing a “sniff test.” For this

Causes of diaphragm dysfunction

A myriad of disorders that involve either the central nervous system, phrenic nerve, neuromuscular junction, or diaphragm muscle itself can cause weakness or paralysis and involve either one or both hemidiaphragms.18, 32, 33, 34, 35, 36, 37 A partial list of these disorders is given in Box 1.

Diaphragm eventration

Eventration refers to a condition where part of the diaphragm is replaced with fibroelastic tissue or where there is localized diaphragm atrophy. Eventration may be noted at birth and is due to failure of the fetal diaphragm to properly develop. In adults, it may be due to phrenic nerve injury or occur for unknown reasons.88 Eventration can be seen on a chest radiograph as a localized area of diaphragm elevation. The localized nature of the eventration often is best appreciated on the lateral

Diaphragm tumors

Diaphragm tumors can be malignant (primary or metastatic), benign (cystic or solid), or owing to endometriosis. Fibrosarcomas and rhabdomyosarcoms of the diaphragm are very rare. Metastatic malignancies that involve the diaphragm with direct extension include primary lung or esophageal cancer and mesothelioma. Malignancies of the pancreas, stomach, or liver also may extend to the diaphragm. Lipomas are the most common benign solid tumor. Cystic lesions involving the diaphragm are bronchogenic

Diaphragm trauma

Traumatic injuries to the diaphragm are uncommon with an incidence of less than 1% when there is concurrent abdominal trauma.92 If present, diaphragm injuries carry a high mortality (≥25%). Diaphragm injury can occur in the setting of either blunt trauma (automobile accidents) or penetrating trauma (gunshot wounds, stabbings). When diaphragm injuries exist, associated injuries to other organs occurs 50% to 75% of the time.93, 94 The left hemidiaphragm seems to be more likely injured during

Diaphragm hernias

Congenital diaphragmatic hernias occur in approximately 1 in 2500 births in the United States. They form when the diaphragm muscle fails to develop prenatally. Consequently, abdominal viscera may migrate into the thorax. When this occurs in infants, there is hypoplasia of the ipsilateral lung, bronchial structure, and pulmonary arterial tree. The mortality and morbidity of congenital diaphragmatic hernias are related to the severity of lung hypoplasia and pulmonary hypertension, and the

Treatment and prognosis

The natural history of diaphragmatic dysfunction depends largely on its etiology and the rate of progression of underlying disease. In certain neuromuscular diseases (eg, muscular dystrophies) the course of diaphragmatic dysfunction is predictable, whereas in the case of posttraumatic or infectious diaphragmatic paralysis, recovery may occur in some, but not all, cases. The likelihood of spontaneous recovery of diaphragm function occurring depends on the etiology of the dysfunction. The phrenic

Summary

The diaphragm is a dome-shaped structure that separates the thorax from the abdomen. It is the major inspiratory muscle and serves to separate the abdominal contents from the thorax. Disorders of the diaphragm may impair its performance or disrupt its integrity. Impaired performance can result in dyspnea, poor exercise performance, or nocturnal hypoventilation. Its integrity can be impaired locally by eventration. However, with diaphragm hernias or trauma, diaphragm integrity may be diminished

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    Disclosure: None of the authors have any financial interests in subject matter or materials discussed in this article.

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