Apnea

Apnea, the cessation of spontaneous respiration, is occasionally temporary and self-limiting, as occurs during Cheyne-Stokes and Biot’s respirations. More commonly, however, it’s a life-threatening emergency that requires immediate intervention to prevent death.

Apnea usually results from one or more of six pathophysiologic mechanisms, each of which has numerous causes. Its most common causes include trauma, cardiac arrest, neurologic disease, aspiration of foreign objects, bronchospasm, and drug overdose. (See Causes of apnea, page 56.)

Emergency interventions

If you detect apnea, first establish and maintain a patent airway. Position the patient in a supine position and open his airway using the head-tilt, chin-lift technique. (Caution: If the patient has an obvious or suspected head or neck injury, use the jaw-thrust technique to prevent hyperextending the neck.) Next, quickly look, listen, and feel for spontaneous respiration; if it’s absent, begin artificial ventilation until it occurs or until mechanical ventilation can be initiated.

Because apnea may result from cardiac arrest (or may cause it), assess the patient’s carotid pulse immediately after you’ve established a patent airway. Or, if the patient is an infant or small child, assess the brachial pulse instead. If you can’t palpate a pulse, begin cardiac compression.

History and physical examination

When the patient’s respiratory and cardiac status is stable, investigate the underlying cause of apnea. Ask him (or, if he’s unable to answer, anyone who witnessed the episode) about the onset of apnea and events immediately preceding it. The cause may become readily apparent, as in trauma.

Take a patient history, noting especially reports of headache, chest pain, muscle weakness, sore throat, or dyspnea. Ask about a history of respiratory, cardiac, or neurologic disease and about allergies and drug use.

Inspect the head, face, neck, and trunk for soft-tissue injury, hemorrhage, or skeletal deformity. Don’t overlook obvious clues, such as oral and nasal secretions reflecting fluid-filled airways and alveoli or facial soot and singed nasal hair suggesting thermal injury to the tracheobronchial tree.

Auscultate over all lung lobes for adventitious breath sounds, particularly crackles and rhonchi, and percuss the lung fields for increased dullness or hyperresonance. Move on to the heart, auscultating for murmurs, pericardial friction rub, and arrhythmia. Check for cyanosis, pallor, jugular vein distention, and edema. If appropriate, perform a neurologic assessment. Evaluate the patient’s level of consciousness (LOC), orientation, and mental status; test cranial nerve function and motor function, sensation, and reflexes in all extremities.

Medical causes

❑ Airway obstruction. Occlusion or compression of the trachea, central airways, or smaller airways can cause sudden apnea by blocking the patient’s airflow and producing acute respiratory failure.

❑ Brain stem dysfunction. Primary or secondary brain stem dysfunction can cause apnea by destroying the brain stem’s ability to initiate respirations. Apnea may arise suddenly (as in trauma, hemorrhage, or infarction) or gradually (as in degenerative disease or tumor). Apnea may be preceded by a decreased LOC and by various motor and sensory deficits.

❑ Neuromuscular failure. Trauma or disease can disrupt the mechanics of respiration, causing sudden or gradual apnea. Associated findings include diaphragmatic or intercostal muscle paralysis from injury or respiratory weakness or paralysis from acute or degenerative disease.

❑ Parenchymatous lung disease. An accumulation of fluid within the alveoli produces apnea by interfering with pulmonary gas exchange and producing acute respiratory failure. Apnea may arise suddenly, as in near drowning and acute pulmonary edema, or gradually, as in emphysema. Apnea may also be preceded by crackles and labored respirations with accessory muscle use.

❑ Pleural pressure gradient disruption. Conversion of normal negative pleural air pressure to positive pressure by chest wall injuries (such as flail chest) causes lung collapse, producing respiratory distress and, if untreated, apnea. Associated signs include an asymmetrical chest wall and asymmetrical or paradoxical respirations.

❑ Pulmonary capillary perfusion decrease. Apnea can stem from obstructed pulmonary circulation, most commonly due to heart failure or lack of circulatory patency. It occurs suddenly in cardiac arrest, massive pulmonary embolism, and most cases of severe shock. In contrast, it occurs progressively in septic shock and pulmonary hypertension. Related findings include hypotension, tachycardia, and edema.

Other causes

❑ Drugs. Central nervous system (CNS) depressants may cause hypoventilation and apnea. Benzodiazepines may cause respiratory depression and apnea when given I.V. along with other CNS depressants to elderly or acutely ill patients.

Neuromuscular blockers — such as curariform drugs and anticholinesterases — may produce sudden apnea because of respiratory muscle paralysis.

❑ Sleep-related apneas. These repetitive apneas occur during sleep from airflow obstruction or brain stem dysfunction.

Special considerations

Closely monitor the patient’s cardiac and respiratory status to prevent further episodes of apnea.

Pediatric pointers

Premature neonates are especially susceptible to periodic episodes of apnea because of CNS immaturity. Other common causes include sepsis, intraventricular and subarachnoid hemorrhage, seizures, bronchiolitis, and sudden infant death syndrome.

In toddlers and older children, the primary cause of apnea is acute airway obstruction from aspiration of foreign objects. Other causes include acute epiglottiditis, croup, asthma, and systemic disorders, such as muscular dystrophy and cystic fibrosis.

Geriatric pointers

In elderly patients, increased sensitivity to analgesics, sedative-hypnotics, or a combination of these drugs may produce apnea, even with normal dosage ranges.

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Book Source Details

• Book Title: Handbook of Signs & Symptoms (Third Edition)
• Author(s): Springhouse
• Year of Publication: 2006
• Copyright Details: Handbook of Signs & Symptoms (Third Edition), Copyright © 2006 Lippincott Williams & Wilkins.

Other Book Chapters Related to Breathlessness on exertion

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Copyright Details: Handbook of Signs & Symptoms (Third Edition), Copyright © 2008 Williams & Wilkins.

More About Causes of Breathlessness on exertion

• Back to symptom: Breathlessness on exertion: Introduction (review 6 causes)
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More About This Book: Title: Handbook of Signs & Symptoms (Third Edition) Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2006 ISBN: 1-58255-402-1

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