The diaphragm is a large, dome-shaped muscle at the base of the chest cavity and is the primary muscle responsible for breathing. Its normal dome shape allows it to contract downward efficiently, creating negative pressure that draws air into the lungs. Diaphragmatic flattening is the loss of this shape, which impairs breathing efficiency, though therapeutic strategies exist to improve function depending on the underlying cause.
The Role of the Diaphragm and How It Becomes Flattened
During inhalation, the diaphragm descends into the abdomen, expanding chest volume and reducing pressure inside the lungs to pull air inward. The muscle’s dome shape allows for a powerful downward pull, driving respiration. When the muscle contracts, its fibers shorten and the central tendon descends, creating a piston-like action.
The main cause of diaphragmatic flattening is chronic hyperinflation of the lungs, a condition most often associated with severe Chronic Obstructive Pulmonary Disease (COPD), particularly emphysema. Hyperinflation occurs when air becomes trapped in the lungs, causing them to over-expand and push down against the diaphragm. This constant downward pressure stretches the muscle fibers and forces the diaphragm into a flatter, lower position.
A flattened diaphragm loses its mechanical advantage because the muscle fibers are already shortened and cannot contract effectively against the high internal pressure of the overinflated lungs. Instead of pulling straight down, the muscle’s force is directed more sideways, making the movement less efficient and reducing the volume of air drawn in. This altered geometry forces the body to rely more on accessory muscles in the neck and chest, leading to increased work of breathing and fatigue.
Diagnosing Diaphragmatic Dysfunction
Physicians use a combination of imaging and functional tests to confirm physical flattening and assess the degree of dysfunction. A standard chest X-ray often provides the first visual evidence, showing a lower, less curved diaphragm compared to a healthy dome shape, which suggests lung hyperinflation. Computed Tomography (CT) scans offer a more detailed view of the lung tissue and diaphragm morphology, useful for characterizing the underlying lung disease.
Functional assessment is achieved through tests like fluoroscopy, which is a dynamic X-ray that shows the diaphragm’s movement in real-time during breathing and during a “sniff test.” This test can reveal reduced excursion or even paradoxical movement, where the diaphragm moves upward instead of downward during inhalation. Pulmonary Function Tests (PFTs) measure lung volumes and airflow, indirectly confirming hyperinflation by showing an increase in residual volume and total lung capacity.
Ultrasound is increasingly used as a noninvasive tool to directly measure the diaphragm’s mobility and thickness, providing a specific assessment of its contractility. The measurement of diaphragmatic excursion, or how far the muscle moves, is a direct indicator of its function. These diagnostic steps are necessary to distinguish between flattening caused by chronic lung disease and dysfunction resulting from phrenic nerve damage or other causes.
Non-Surgical Approaches to Restore Function
For the majority of cases linked to chronic hyperinflation, non-surgical approaches are the primary strategy for improving function and managing symptoms. The core of this management is comprehensive Pulmonary Rehabilitation (PR), which enhances health outcomes and exercise tolerance in people with COPD. PR programs incorporate exercise training, breathing techniques, and education aimed at increasing the endurance and strength of respiratory muscles.
Specific breathing exercises are taught to help optimize the use of the diaphragm and reduce the reliance on accessory muscles. Diaphragmatic breathing, often called abdominal breathing, involves consciously engaging the muscle to take deeper breaths, thereby strengthening it and slowing the respiratory rate. Another technique, pursed-lip breathing, helps to keep airways open longer during exhalation, which reduces air trapping and can indirectly lessen the hyperinflation that causes the flattening.
Inspiratory Muscle Training (IMT) uses a device to create resistance during inhalation, specifically targeting the diaphragm to improve its strength and endurance. While these methods do not physically restore the muscle’s original dome shape, they improve its operational efficiency and mobility, allowing for better gas exchange. Medication management to reduce airway obstruction and inflammation is essential, as controlling the underlying lung disease limits further hyperinflation and mechanical stress on the diaphragm.
Surgical Options and Realistic Expectations
Surgical intervention is generally reserved for specific conditions or when non-surgical treatments have proven insufficient, with the approach differing based on the cause of dysfunction. For patients with a flattened diaphragm due to advanced emphysema, Lung Volume Reduction Surgery (LVRS) may be considered. LVRS removes the most diseased, over-inflated parts of the lung, decreasing overall lung volume and reducing the pressure pushing down on the diaphragm, which allows the muscle to recoil slightly.
In cases where the diaphragm is flattened or paralyzed due to phrenic nerve injury, surgical options focus on restoring nerve function or stabilizing the muscle. Diaphragm plication is a procedure for unilateral paralysis that involves surgically folding and flattening the diaphragm to take the slack out of the muscle, thereby improving the mechanical action of the healthy lung. Phrenic nerve pacing, which involves implanting electrodes to electrically stimulate the nerve and cause the diaphragm to contract, is a method used for paralysis, especially in patients with spinal cord injuries.
It is important to maintain realistic expectations, as the goal of treatment for a chronically flattened diaphragm is maximizing quality of life and respiratory endurance, rather than complete anatomical correction. In advanced lung disease, the degree of physical reshaping is limited, so the long-term outlook focuses on optimizing the muscle’s remaining function through rehabilitation and medical therapy. Combining phrenic nerve reconstruction with a diaphragm pacemaker has shown effectiveness in restoring functional activity in specific cases of bilateral diaphragm paralysis.