Respiratory System Function and Sounds

Ventilation, Perfusion, and Diffusion

• Ventilation: Movement of air into and out of the lungs.
• Perfusion: Movement of blood into and out of the capillary beds and to other organs.
• Diffusion: Movement of gases between the air spaces in the lungs and the bloodstream.

Lung Sounds and Associated Conditions

• Wheezing: Whistling, musical sound caused by narrow or obstructed airways.
  • Asthma:
  • COPD (Chronic Obstructive Pulmonary Disease) including chronic bronchitis
  • Sleep Apnea:
  • CHF (Congestive Heart Failure) and GERD (Gastroesophageal Reflux Disease)
  • Bronchiectasis, bronchiolitis, lung cancer, anaphylaxis
• Crackles: Discontinuous, high-pitched sounds heard during inspiration.
  • COPD (Chronic Obstructive Pulmonary Disease) including chronic bronchitis
  • Asbestosis:
  • Idiopathic pulmonary fibrosis:
• Stridor: Monomorphic sound indicating narrowing of the larynx
  • Status Asthmaticus:
  • Choking/Foreign Body: Obstruction of the larynx or trachea

Restrictive vs. Obstructive Lung Diseases

• Obstructive Lung Diseases: Characterized by decreased FEV1 (Forced Expiratory Volume in 1 second) and decreased FEV1/FVC (Forced Vital Capacity) ratio.
  • Asthma
  • COPD: (Emphysema and Chronic Bronchitis)
  • Cystic Fibrosis
  • Bronchiectasis
• Restrictive Lung Diseases: Characterized by increased or normal FEV1/FVC ratio.
  • Sarcoidosis
  • Pneumoconiosis: (Berylliosis, Byssinosis, Asbestosis )
  • Idiopathic pulmonary fibrosis

Asthma Severity Classifications

• Inconsistent Asthma: Uses short-acting beta-agonists (SABAs) 1-2 times or less during the daytime in a week and wakes up less than 2 times a month.
• Mild Persistent Asthma: Uses SABAs >2 times or more in a week and wakes up 3-4 times a month.
• Moderate Persistent Asthma: Daily symptoms, uses SABAs every day, and wakes up more than 5 times a month.
• Severe Persistent Asthma: Uses SABAs 2-3 times a day, wakes up every night, and has continuous symptoms.

Asthma Triads

• Classic Triad: Expiratory wheezing, dyspnea, cough
• Atopic Triad: Asthma, allergic rhinitis, eczema
• Samter's Triad: Asthma, nasal polyps, aspirin allergy

Pulmonary Function Tests

• Pulmonary Function Tests: Measure the amount and speed of air a person can inhale and exhale.
  • Spirometry: Measures lung volumes and flow rates.
  • Plethysmography: An airtight box that patients sit or stand in to conduct the test.
• Peak Flow: Monitors the response to treatment (usually used for asthma)
  • The maximum speed at which a person can exhale.
• Incentive Spirometry: A device used to help patients breathe deeply after surgery or illness. It encourages them to take slow, deep breaths to help improve lung function.

Cystic Fibrosis Infection Suspects

• Pseudomonas aeruginosa: Most common bacterial infection in patients with cystic fibrosis.
  • Treatment: Fluoroquinolones and aminoglycosides (e.g., Levofloxacin and Gentamycin)

Cystic Fibrosis Associated Conditions

• Floating Stools: Due to pancreatic insufficiency.
• Infertility: Men experience infertility, and women have decreased fertility.
• Meconium Ileus: Obstruction of the intestines in newborns.
• Salty-Tasting Skin: Infants with cystic fibrosis may have salty-tasting sweat.

Key Points About Cystic Fibrosis

• Autosomal Recessive Disorder: Both parents must carry the gene for a child to inherit the disease.
• Most Common Lethal Genetic Disease in the White Population: Cystic fibrosis is the most common lethal genetic disease in people of European descent.
• **CFTR Gene: ** The CFTR gene on chromosome 7 regulates chloride channels, impacting the flow of sodium, chloride, and bicarbonate.

How to Identify Cystic Fibrosis in a Clinical Case

• Symptoms:
  • Chronic bacterial infections of the lungs, leading to bronchiectasis.
  • Pancreatic insufficiency with malabsorption of fat and fat-soluble vitamins, causing oily stools (steatorrhea).
  • Infants may have salty-tasting skin and excessive sweating.
  • Hyponatremia and elevated lipase levels.
• CXR (Chest X-ray): Hyperinflation, bronchial wall thickening, atelectasis, and bronchiectasis.

Tests for Cystic Fibrosis

• Elevated Sweat Chloride Test: Sweat chloride levels greater than 60 mmol/L on two separate visits confirm cystic fibrosis.
• Genetic Screening: Genetic testing confirms the diagnosis.