The diaphragm is a thin, dome-shaped sheet of muscle that separates the chest cavity from the abdomen and acts as the primary engine for breathing. This muscle contracts and flattens during inhalation, pulling air into the lungs, and relaxes during exhalation, allowing air to flow out. An elevated diaphragm, also known as diaphragmatic paralysis or eventration, occurs when one or both sides of this muscle are positioned higher than normal in the chest. This elevation is caused by weakness or a lack of innervation, which prevents the muscle from descending properly during the breathing cycle. The abnormal positioning reduces the volume available for the lungs to expand, which can lead to a spectrum of symptoms depending on the severity of the condition.
Physical Manifestations
The most common symptom of an elevated diaphragm is shortness of breath, medically termed dyspnea, which occurs because the muscle cannot generate the necessary negative pressure to fully expand the lung. This difficulty breathing is often most noticeable during physical activity or exertion, as the body struggles to meet the increased oxygen demand. Orthopnea is shortness of breath experienced when lying flat. In this supine position, the weight of the abdominal organs pushes the already weakened diaphragm further into the chest cavity, severely limiting lung capacity.
The reduced lung volume and impaired clearance of secretions can also lead to recurring respiratory infections, such as pneumonia or atelectasis, particularly in the lower lobes of the affected lung. Another distinct physical sign is the paradoxical movement of the diaphragm, which can be seen in patients with diaphragmatic paralysis. When the functional side of the diaphragm contracts during inspiration, it creates negative pressure that causes the paralyzed, elevated side to be sucked upward instead of moving downward.
While the primary symptoms are respiratory, the displacement of abdominal organs due to the elevated diaphragm can cause gastrointestinal discomfort. Patients may report mild abdominal fullness, dyspepsia, or pain in the upper abdomen. Many people with a mild or unilateral elevation may be completely asymptomatic, with the condition only being discovered incidentally on a chest X-ray performed for another reason.
Underlying Causes
The most frequent underlying cause of an elevated diaphragm is damage to the phrenic nerve. This damage, resulting in phrenic nerve palsy or paralysis, stops the nerve from transmitting the signal to contract. A common cause of phrenic nerve injury is iatrogenic damage, often resulting from surgical procedures in the chest or neck area, particularly cardiac surgery.
During open-heart surgery, the phrenic nerve can be injured by excessive surgical retraction, mechanical manipulation, or cold thermal damage from the ice slush used for myocardial protection. Beyond surgical injury, the phrenic nerve can be compressed or invaded by a space-occupying lesion, such as a lung tumor or a malignant mediastinal tumor. In some instances, the cause remains unknown, and the condition is classified as idiopathic.
Diaphragmatic eventration is a congenital defect where the muscle tissue is replaced by a thin, fibro-elastic membrane due to a failure in the migration of myoblasts during fetal development. A mass effect originating from the abdomen can physically push the diaphragm upward, causing an elevated position. Examples include a large liver (hepatomegaly), an enlarged spleen (splenomegaly), or a subphrenic abscess.
Confirmation and Diagnosis
The initial step in confirming an elevated diaphragm is a standard chest X-ray, which demonstrates the abnormally high position of one or both sides of the muscle. If the diaphragm appears elevated, a dynamic imaging study like fluoroscopy, often called a “sniff test,” is performed to observe movement during breathing. In this test, a paralyzed diaphragm moves upward paradoxically during a sharp sniff, rather than moving downward with the functional side.
Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) scans are often used to rule out a space-occupying lesion. These scans can identify tumors, cysts, or abscesses in the chest or abdomen that may be pushing the diaphragm upward. Pulmonary function tests (PFTs) provide objective evidence of the functional impairment, typically revealing a restrictive pattern because of the reduced lung volume.
Positional change in vital capacity (VC) is measured using PFTs. A patient with diaphragmatic paralysis will show a significantly larger drop in VC when moving from an upright to a supine position, sometimes up to 50% in bilateral cases, due to the abdominal contents pushing against the weakened muscle. Measurement of the maximal inspiratory pressure (MIP) is also performed, which is markedly reduced because the compromised diaphragm cannot generate the necessary inspiratory force.
Treatment and Management
The treatment for an elevated diaphragm is tailored to the severity of the symptoms and the underlying cause. For patients who are asymptomatic or experience only mild, manageable symptoms, watchful waiting is often the primary strategy. This approach is common because some cases of phrenic nerve injury, particularly those caused by surgical cooling, may resolve spontaneously over several months.
For individuals suffering from significant shortness of breath, particularly orthopnea or exertional dyspnea, non-invasive ventilation (NIV) provides support. NIV uses a mask to deliver positive pressure, maintaining adequate lung capacity and reversing hypercapnic respiratory failure, especially during sleep. This therapy is often a temporary measure or an alternative for patients who are not suitable for surgery.
The definitive treatment for a symptomatic, permanently paralyzed or eventrated diaphragm is diaphragmatic plication. Plication involves folding and tightening the diaphragm to flatten it and secure it in a lower position. This corrects the paradoxical movement and restores volume to the chest cavity, leading to symptomatic relief and increased tidal volume during breathing. The long-term outlook is generally favorable for patients who receive successful plication, often improving exercise tolerance and overall quality of life.