Department of pulmonology R4 Ja Won Koo Disease Review Dysfunction of the Diaphragm N Engl J Med 2012;366:932-42. Department of pulmonology R4 Ja Won Koo

Diaphragm Dome-shaped Separates the thoracic and abdominal cavities Innervated by the phrenic nerves from C3~C5 Fatigue-resistant slow-twitch type I and fast-twitch type IIa myofibers

Clinical feature Unexplained dyspnea  rule out diaphragmatic dysfunction Partial loss of the ability to generate pressure (weakness) to complete loss of diaphragmatic function (paralysis). involve either one or both hemidiaphragms Etiology : metabolic or inflammatory disorders, after trauma or surgery, during mechanical ventilation, and with mediastinal masses, myopathies, neuropathies, or diseases that cause lung hyperinflation.

Unilateral diaphragmatic paralysis : asymptomatic, dyspnea on exertion, limited ability to exercise, supine position dyspnea Bilateral diaphragmatic paralysis unexplained dyspnea or recurrent respiratory failure Dyspnea : rest, supine, exertion, in water above their waist sleep fragmentation and hypoventilation during sleep fatigue, hypersomnia, depression, morning headaches, and frequent nocturnal awakenings Subsegmental atelectasis and infections of the lower respiratory tract

Physical examination Tachypnea and use of accessory muscles - contraction of the sternocleidomastoid muscles Abdominal paradox : maximum transdiaphragmatic pressure <30 cm of water

Natural history Cause and Rate of progression of the underlying disease Neuromuscular : progressive Traumatic or infectious : spontaneous Phrenic nerve - Regeneration time : 3years Neuralgic amyotrophy - typically in 1 to 1.5 years Cardiac surgery : shorter, Spinal injury : poor prognosis Hypoventilation : Age-related changes Respiratory drive Respiratory-muscle strength Chest-wall compliance

Causes Classified by the level of the impairment

Spinal cord injuries C1, C2 : Diaphragmatic paralysis C3~C5 : Partially preserved (C3 : 40% MV, C5 : 15% MV) Damage to the phrenic nerve : Iatrogenic injury during surgery (transection, stretching, crushing, hypothermia) compression caused by bronchogenic or mediastinal tumors Trauma infections (Herpes zoster and Lyme disease) Inflammatory disorders Guillain–Barré syndrome : 25% need Mechanical Ventilation

Disordered synaptic transmission at the neuromuscular junction myasthenia gravis Botulinum toxins Aminoglycosides Critical illness polyneuropathy and myopathy Sepsis, multiorgan failure, and Hyperglycemia Disuse atrophy of the diaphragm – mechanical ventilation, paralyzing agents Undernutrition and metabolic abnormalities COPD (lung hyperinflation) - shortening the diaphragm, lesser extend  mechanical disadventage

Diagnosis Chest radiographs : Elevated hemidiaphragms, basal subsegmental atelectasis Unilateral dysfunction : sensitivity : 90%, specificity : 44% Bilateral elevation : poor inspiratory effort, low lung volumes Fluoroscopy of the diaphragm Sniff test : assessing the motion of the diaphragm during a short, sharp inspiratory effort Normal : Descent of the diaphragm Unilateral diaphragmatic paralysis : paradoxical (cephalad) movement of the paralyzed hemidiaphragm

Pulmonary-function tests TLC : Unilateral 70~79% of pred, Bilateral 30~50% of pred Upright and supine Vital Capacity Supine position VC decrease : Unilateral 10~30%, Bilateral 30~50% FRC and RV : no decrease in unilateral Maximal static inspiratory pressure and sniff nasal inspiratory pressure : Unilateral 60% of pred, bilateral 30% of pred Maximal expiratory pressure : spare expiratory muscle

Transdiaphragmatic pressure [Pdi] Difference of Gastric and esophageal pressure sniff Pdi : maximal sniff maneuvers Pdimax : maximal inspiratory efforts twitch Pdi : transcutaneous electrical or magnetic stimulation of the phrenic nerve – standard for diagnosis of bilateral paralysis Normal range : sniff Pdi or Pdi max ≥ 80 cm of water(men), ≥ 70 cm of water (women) twitch Pdi ≥ 10 cm of water with unilateral phrenic-nerve stimulation ≥ 20 cm of water with bilateral phrenic-nerve stimulation

Ultrasonography Zone of apposition Normal : Thickening of the diaphragm during inspiration Diagnosis and monitoring Central tendon of the diaphragm, not the muscular component Electromyography of the diaphragm Queit breathing or stimulation of the phrenic nerve Useful in distinguishing between neuropathic and myopathic Limitation : technical issue

Treatment Cause, Nocturnal hypoventilation Treatable cause myopathies related to metabolic disturbances, Myopathies due to parasitic infection, Idiopathic diaphragmatic paralysis paralysis due to neuralgic amyotrophy Persists or progresses : ventilatory support Ix. for initiating nocturnal noninvasive ventilation pCO2 ≥ 45mmHg in day time O2 saturation ≤ 88%, 5min at night Maximal static inspiratory pressure < 60 cm of water or FVC < 50% of pred in progressive neuromuscular disease

Plication of the diaphragm - unilateral diaphragmatic paralysis increases of up to 20 % in VC, FEV1, and TLC with improvement in dyspnea Eur J Cardiothorac Surg. 2007 Sep;32(3):449-56. Epub 2007 Jul 19

high cervical cord quadriplegia, central hypoventilation Phrenic pacing potential to provide full ventilatory support in bilateral paralysis, intact phrenic nerve high cervical cord quadriplegia, central hypoventilation laparoscopic mapping of motor points and intramuscular stimulation of the diaphragm