Disorders of Breathing

Sleep apnea may be obstructive or central in origin, or a combination of both. The effects of recurrent apnea extend well beyond simple fatigue or sleep deprivation, causing significant cardiovascular and neurologic disease. Patients with obstructive sleep apnea are often but not always obese. They experience episodes of intermittent apnea, often associated with snoring, especially during deeper stages of sleep. In addition to obesity, adenoidal or tonsillar enlargement, mac-roglossia, and laxity of the soft palate and pharyngeal tissue can contribute to sleep apnea. Stroke, brain tumors, trauma, cerebral edema, and other CNS disorders can affect breathing at the central level as well. Brainstem infarctions can lead to respiratory arrest and death. Cheynes-Stokes respirations describe an undulating pattern of breathing of increased depth and frequency alternating with waves of shallow, slower breathing and even apnea.

Many patients with obstructive sleep apnea have elements of central apnea as well. For example, alcohol and sedatives can exacerbate the respiratory depression and contribute to pharyngeal muscle laxity. In addition, patients with chronic obstructive sleep apnea can develop chronic CO2 retention that further depresses respiration. Patients with the classic "pickwickian syndrome" (obesity and hypoventilation syndrome) have a constellation of signs, including morbid obesity, obstructive apnea, polycythemia, pulmonary hypertension, and right-sided heart failure. Patients can present with symptoms of daytime drowsiness, sleepiness, or feeling inadequately rested. Family members often bring the problem to the attention of the patient or the family physician, having observed loud snoring and interruptions in breathing during sleep. Sometimes a motor vehicle crash resulting from somnolence while driving brings the condition to light. Depression can also develop.

In addition to symptoms related to loss of sleep or upper airway obstruction, sleep apnea can contribute to other major causes of morbidity and mortality. Bradyarrhythmias are common, and hypoxia can lead to ventricular arrhythmias or even myocardial ischemia or stroke. When episodic hypoventilation becomes frequent or chronic, with resultant hypoxia and hypercapnia, a metabolic response may counteract the respiratory acidosis associated with hypoventilation; the kidneys retain bicarbonate to foster a compensatory metabolic alkalosis. Systemic and pulmonary hypertension may be intermediate outcomes that lead to more serious cardiac complications.

Formal diagnosis of sleep apnea can be made in a sleep laboratory using multichannel recording (polysomnography) of EEG, ECG, airflow, upper airway muscle tone, and oximetry. Home oximetry alone might not be adequately sensitive. The most essential treatment is significant weight reduction to decrease obesity. Other behavioral treatments include avoiding supine sleep and avoiding alcohol or sedatives. Nasal CPAP is effective for patients who tolerate it. Various oral or dental devices are also available, but data on effectiveness are limited. Surgical procedures attempt to reduce airway obstruction at the palate or tonsillopharyngeal or adenoidal

The complete reference list is available online at www.expertconsult.com.

www.guidelines.gov Provides clinical guidelines for pulmonary function testing and treatment. www.thoracic.org/sections/publications/statements/index.html

American Thoracic Society; general pulmonary guidelines. www.nhlbi.nih.gov/guidelines/asthma/orwww.nhlbi.nih.gov/about/

naepp/ Clinical guidelines for asthma. www.goldcopd.com Global Initiative for Chronic Obstructive Lung Disease (COPD); Global Strategy for the Diagnosis, Management, and Prevention of COPD (GOLD guidelines). www.thoracic.org/sections/publications/statements/resources/idsaats-

cap.pdf Information on community-acquired pneumonia. www.cdc.gov/flu/professionals/andwww.cdc.gov/vaccines/vpd-vac/ pneumo Centers for Disease Control and Prevention; pneumococ-cal and influenza vaccines. www.thoracic.org/sections/publications/statements/pages/mtpi/rr5211. html American Thoracic Society; tuberculosis information.

levels. The American Academy of Sleep Medicine (AASM) has published clinical guidelines with evidence-based recommendations and algorithms for the evaluation, diagnosis, treatment and follow-up of patients with sleep disorders (Epstein et al., 2009).

www.cdcnpin.org/scripts/tb/cdc.asp CDC tuberculosis information. http://meded.ucsd.edu/clinicalmed/lung.htm; www.med.ucla.edu/

wilkes Physical examination and lung auscultation. www.aafp.org/afp/2004/0301/p1107.html Interpretation of spirometry. www.nlhep.org/resources-medical.html#spirometry National Lung

Health Education Program; spirometry information. http://phil.cdc.gov/phil/quicksearch.asp Pulmonary imaging

(e.g., chest radiograph, CT) www.uams.edu/radiology/education/teaching_cases/default.asp

University of Arkansas Medical Sciences, Department of Radiology Teaching Cases.

http://medinfo.ufl.edu/year1/rad6190/topics/lect4.shtml University of

Florida Anatomy by Diagnostic Imaging course. www.lungusa.org/ American Lung Association; community and patient resources.

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