flatter, fatigues; during rapid eye movement sleep, intercostal muscle movements become uncoordinated TABLE 71.3 CAUSES OF RESPIRATORY DISTRESS Respiratory system Upper airway obstruction Nasopharynx (craniofacial anomalies, choanal atresia, nasal congestion, adenotonsillar hypertrophy, foreign body, trauma, mass) Oropharynx (macroglossia, micrognathia, midface hypoplasia, tonsillitis, peritonsillar abscess, Ludwig angina, trauma) Larynx (epiglottitis, laryngomalacia, hemangioma, papilloma, webs, cysts, laryngoceles, laryngotracheal cleft, subglottic stenosis, croup, retropharyngeal abscess, tracheitis, anaphylaxis, angioneurotic edema, trauma, thermal or chemical burn, foreign body, vocal cord paralysis, laryngospasm, hypocalcemic tetany, mass) Trachea (tracheomalacia, stenosis, tracheoesophageal fistula, foreign body, mass) Bronchi (bronchomalacia, stenosis, bronchogenic cyst, bronchitis, foreign body) Lower airway obstruction/acinar/interstitial disease Bronchioles (asthma, bronchiolitis, allergy, angioneurotic edema, bronchiectasis) Acini/interstitium Disorders of lung maturity (transient tachypnea of newborn, respiratory distress syndrome, bronchopulmonary dysplasia, persistent fetal circulation) Congenital malformation (congenital emphysema, cystic adenomatoid malformation, sequestration, pulmonary agenesis/aplasia/hypoplasia, pulmonary cyst) Aspiration (meconium, foreign body, near drowning, gastroesophageal reflux, vomiting) Infection (pneumonia; bacterial, atypical bacteria, viral, chlamydial, pertussis, fungal, pneumocystis) Pulmonary collapse (atelectasis), fluid (consolidation, edema, hemorrhage), mass Environmental/trauma (high-altitude pulmonary edema, thermal or chemical burn, smoke, carbon monoxide, biologic and chemical agents, hydrocarbon, drug-induced pulmonary fibrosis, bronchopulmonary traumatic disruption, pulmonary contusion) Central nervous system Structural abnormality (agenesis, hydrocephalus, mass, arteriovascular malformation) Dysfunction/immaturity (apnea, hyperventilation/hypoventilation) Infection (meningitis, encephalitis, abscess) Inherited or acquired degenerative disease Intoxication, central nervous system depression (alcohol, barbiturates, benzodiazepines, opiates, neurotoxins) Seizure Trauma (birth asphyxia, hemorrhage) Spinal cord (congenital anomaly, tetanus, trauma) Anterior horn (poliomyelitis, transverse myelitis, spinal muscular atrophy) Peripheral nervous system Peripheral motor nerve (phrenic nerve injury, Guillain–Barré syndrome, multiple sclerosis, tick paralysis, heavy metal or organophosphate toxicity, porphyria) Neuromuscular junction (myasthenia gravis, botulism, snake bite, organophosphate toxicity, antibiotics) Muscle (muscular/myotonic dystrophies, IEM, carnitine deficiency, polymyositis/dermatomyositis, fatigue) Chest wall/intrathoracic Air leak (pneumothorax, tension pneumothorax, pneumomediastinum, pneumopericardium) Space-occupying (esophageal foreign body, pleural effusion, empyema, chylothorax, hemothorax, anomalies of the great vessels, diaphragmatic hernia, cyst, mass) Bony and/or muscular deformity or dysfunction (congenital bone/muscle absence, spine deformity, pectus excavatum/carinatum, diaphragmatic hernia, contusion, rib fractures/flail chest, burn) Cardiovascular Congenital (structural defect, arrhythmia) Acquired (cardiogenic shock, arrhythmia, valvular heart disease, myocarditis, myocardial ischemia or infarction, pericarditis, pericardial effusion, pericardial tamponade, aortic dissection or rupture, mass, coronary artery dilation/aneurysm, congestive heart failure) Gastrointestinal