Respiratory system

• Apnea


  Cessation of airflow for more than 10 sec
• Obstructive apnea


  Patient continues to make respiratory efforts against an obstruction (typically a narrowing or closure in the upper airway)
• Obstructive sleep apnea (OSA) occurs in 3% to 4% of women and 6% to 9% of men

  
• Recurrent decrements in airflow


  Apneas or hypopneas most commonly occur during sleep

  
• Events more prominent during rapid eye movement sleep


  Caused by associated hypotonia of upper airway musculature

  
• Central apnea


  Patient makes no respiratory effort during the apnea
• Central sleep apnea (CSA) is much less common than OSA

  
• Mixed apnea


  Apnea with features of both OSA and CSA
• Hypopnea


  A 30% or greater decrease in airflow associated with at least a 3% drop in oxygen saturation or an arousal
• Apnea-hypopnea index (AHI)


  The total number of apneas and hypopneas per hour of sleep; normal is five or fewer events per hour

  
• Respiratory disturbance index (RDI)

  Frequently larger than the AHI because it includes not only apneas and hypopneas, but other respiratory disturbances that can disrupt sleep (e.g., respiratory effort–related arousals [RERAs])

  
• Upper airway resistance syndrome (UARS)

  Repeated arousals secondary to increased upper airway resistance ("crescendo snoring"); AHI is normal, RDI is elevated; no significant oxygen desaturation episodes
• Obesity-hypoventilation syndrome (Pickwickian syndrome)


  Syndrome of morbid obesity and chronic hypoventilation with daytime hypercapnia (arterial partial pressure of carbon dioxide [PaCO2] greater than 45 mm Hg); classically there is also low PaO2 and high bicarbonate; OSA present in majority of patients
• Cheyne-Stokes respirations


  Cyclic rise and fall in respiratory pattern with recurrent periods of apnea; apneas are typically central; most commonly seen with congestive heart failure, central neurologic disease like CVA, or administration of sedative agents, but may occur in patients without these conditions or not taking these medications
• Obstructive sleep apnea (OSA)


  • History obtained from the patient alone may be unreliable; input of bed partner or housemate often helpful; symptoms include loud, disruptive snoring, daytime sleepiness, and witnessed apneas; patients also describe sleep as nonrefreshing, complain of morning headaches, and experience irritability/personality change/depression, cognitive impairment, and decreased libido; nocturia/enuresis may also be seen; physical examination findings include obesity, increased neck circumference, large tonsils and adenoids, large uvula, low soft palate, systemic hypertension, and lower extremity edema; retrognathia, micrognathia, and other craniofacial abnormalities also described

  
• Central sleep apnea (CSA)


  • History findings include daytime sleepiness and witnessed apneas; snoring not a prominent finding; patients may have any body habitus; underlying neurologic disease, if present, determines many of the physical findings

  
• Diagnosis of an apnea syndrome


  Made by an overnight polysomnogram (PSG) sleep study; physiologic parameters measured include airflow, chest/abdominal wall effort, oxygen saturation, electroencephalogram (EEG), electrocardiogram (ECG), electrooculogram (EOG), and body position; recording time should be 6 to 8 hours; if AHI is more than five events per hour, sleep study is positive for sleep apnea; OSA versus CSA is determined by presence versus absence of chest/abdominal wall efforts, respectively

  
• Grading of OSA


  • Mild: 6 to 15 events per hour
  • Moderate: 16 to 30 events per hour
  • Severe: more than 30 events per hour
• Treatment of OSA


  • Three components: behavioral, medical, and surgical; behavioral treatment is commonly the only intervention recommended for patients with mild OSA; compliance is a major problem with nasal continuous positive airway pressure (CPAP); discomfort of apparatus, claustrophobia, aerophagia, and difficulty with exhalation are common side effects
• Treatment of CSA


  • Nasal CPAP usually not effective; treatment of choice: nocturnal nasal noninvasive ventilation with a backup respiratory rate and bilevel (inspiratory and expiratory) positive airway pressure (BiPAP) settings; adaptive servoventilation
• COPD


  Chronic obstructive pulmonary disease

  
• COPD


  • Preventable and treatable disease
  • Characterized by persistent airflow limitation (usually non-reversible)
  • Usually progressive
  • Associated with an enhanced chronic inflammatory response in the airways and the lung to noxious particles or gases

  
• Chronic bronchitis


  Cough and sputum for at least 3 consecutive months in each of 2 consecutive years
• Emphysema


  Abnormal permanent enlargement of the airspaces distal to the terminal bronchioles, accompanied by destruction of their walls and without obvious fibrosis
• Pathophysiology of COPD


  1. Airflow limitation

  2. Premature airway closure

  3. Gas trapping

  4. Hyperinflation

  5. Impaired pulmonary and chest wall compliance

  6. Flattening of diaphragmatic muscles

  7. Horizontal alignment of intercostal muscles

  8. Increased work of breathing
• Emphysema classification


  • Centriacinar
  • Panacinar
  • Paraseptal
• Clinical features of COPD

  • Cough and sputum production are usually the first symptoms
  • Breathlessness is common
  • Physical signs are non-specific and correlate poorly with lung function
  • Finger clubbing is not a feature of COPD
  • Right heart failure may develop in advanced COPD
  • Fatigue, anorexia and weight loss may occur
  • Prolonged expiratory time >5s, with pursed lip breathing

  
• 'Pink puffers' and 'blue bloaters'

  Classical phenotypes of COPD
• Investigations for COPD


  • CXR
  • CBC
  • Electrolytes
  • Echocardiography
  • Pulmonary function test
  • Measurement of lung volumes
  • Exercise tests
  • HRCT
  • Arterial blood gas analysis

  
• Management of COPD


  1. Reducing exposure to noxious particles and gases

  2. Smoking cessation strategies

  3. Bronchodilator therapy

  4. Combined inhaled glucocorticoids and bronchodilators

  5. Oral glucocorticoids

  6. Pulmonary rehabilitation

  7. Oxygen therapy

  8. Surgical intervention

  9. PDE4 Inhibitors

  10. Theophylline

  11. Influenza and pneumococcal vaccination

  
• Acute exacerbations of COPD


  • Increase in symptoms and deterioration in lung function and health status
  • Usually triggered by bacteria, viruses or a change in air quality
  • May be accompanied by respiratory failure and/or fluid retention

  
• Management of acute exacerbations

  1. Oxygen therapy

  2. Bronchodilators

  3. Glucocorticoids

  4. Antibiotic therapy

  5. Non-invasive ventilation
• Acute exacerbations of COPD represent an important cause of death