The diaphragm is the skeletal muscle that separates the abdomen from the thoracic cavity. It draws in with each inspiration, flattening out downward, permitting the bases of the lungs to extend. Paralysis or paresis of the diaphragm is partial or complete causing temporary suspension or permanent loss of function.

The most common causes are spinal cord injury, thoracic trauma, multiple sclerosis, and muscular dystrophy. In addition, unilateral diaphragm paralysis may be caused by invasion of nerves secondary to cancer in the area, e.g., the bronchi.

Patients with unilateral diaphragm paralysis are usually asymptomatic. However, those with bilateral paralysis or weakness most often present with respiratory failure, complications from cor pulmonale and right ventricular heart failure, atelectasis, and pneumonia.

The degree of weakness is most often determined by the measurement of pressures present across the diaphragm. Confirmation of the diagnosis is most often accomplished by the "sniff" test. This test involves visualizing the lungs via fluoroscopy while the patient sniffs. The paralyzed lung moves upward due to the negative pressure within the thoracic area.

The treatment most often used is ventilation (mechanical inhalation) assistance, all, or part of the day. In addition, if the nerves to the diaphragm are intact, treatment that provides stimulation to the nerves (diaphragmatic pacing) may be indicated.

In adults, bilateral diaphragmatic paralysis is almost always an indication that an extensive disease process is present.

• May be entitled to special monthly compensation where the Veteran has a single service-connected disability rated as 100% with additional service-connected disability or disabilities independently ratable at 60% or more, which are separate and distinct from the 100% service-connected disability and involves different anatomical segments or bodily systems. See  38 CFR 3.350(i)(1) – Special Monthly Compensation (SMC).

• A 100% rating shall be assigned for pleurisy with empyema, with or without pleurocutaneous fistula, until resolved.

• Following episodes of total spontaneous pneumothorax, a rating of 100% shall be assigned as of the date of hospital admission and shall continue for three months from the first day of the month after hospital discharge.

• Gunshot wounds of the pleural cavity with bullet or missile retained in lung, pain or discomfort on exertion, or with scattered rales or some limitation of excursion of diaphragm or of lower chest expansion shall be rated at least 20% disabling. Disabling injuries of shoulder girdle muscles (Groups I to IV) shall be separately rated and combined with ratings for respiratory involvement. Involvement of Muscle Group XXI (Diagnostic Code 5321), however, will not be separately rated.  

• Review special provisions regarding the evaluation of specific respiratory conditions under 38 CFR 4.96(a)- Rating co-existing respiratory conditions and 38 CFR 4.96(d)- Special provisions for the application of evaluation criteria for diagnostic codes 6600, 6603, 6604, 6825–6833, and 6840–6845.