Respiratory case examples

• Spirometry

  A) Normal

  B) Obstruction

  C) Restriction

  
• Asthma airways

  A) Thickened airway wall

  B) Narrowed airway

  C) Mucus

  D) Muscle constriction

  
• Lung Function Volumes. All values proportional to:

  • age 
  • gender 
  • height
• Spirometry

  • Simple
  • Measures flow and total volume
  • Volume vs time
  • Can determine:
  • FEV1
  • FVC
  • FEV1/FVC
  • Forced expiratory flow 25%-75% 
  • (FEF25-75)
• Restrictive:

  • TLC < 80% predicted
  • RV < 80%  predicted
• Obstructive:

  • TLC >120% predicted
  • RV > 120% predicted (air trapping)
  • RV/TLC ratio increased
• Obstructive spirometry

  • Decreased FEV1
  • Decreased FVC
  • Decreased FEV1/FVC <70%
• Differential diagnosis of obstructive pattern on spirometry

  • asthma
  • COPD
  • bronchiectasis
  • bronchiolitis
  • upper airway obstruction
• Restrictive spirometry

  • Decreased FEV1
  • Decreased FVC
  • Fev1/FVC normal or increased (≥70%)
• Differential diagnosis of restrictive pattern on spirometry

  • pleural
  • parenchymal
  • chest wall
  • neuromuscular
• Why is expiration reduced in COPD?

  • reduced alveolar recoil
  • narrowed airways
• Pathogenesis of COPD

  • inflammation and fibrosis of airways
  • hypertrophy of submucosal glands and hypersecretion of mucus
  • loss of elastic lung fibres and alveolar tissue (lead to airway narrowing and increased resistance)
• Sarcoidosis - chronic inflammatory disease in which small nodules (granulomas) develop in lungs, lymph nodes and other organs
• Symptoms of sarcoidosis

  • erythema nodosum (tender, red nodules on skin)
  • cough
  • shortness of breath
  • enlarged lymph nodes
  • fatigue
  • joint pain
• Cough: Protective reflex to expel irritant materials from the respiratory passages, sensed by receptors (chemical or mechanical) in the respiratory epithelium. Noxious agents in tobacco smoke result in excess mucus production, inflammation and impaired ciliary function – chronic bronchitis.
• Sarcoidosis is an uncommon chronic inflammatory condition which produces granulomata in various tissues and organs, including skin, lung, liver, brain and heart. Fatigue and breathlessness are common features. Restrictive lung disease results from extensive deposition of inflammatory infiltrates; it also produces enlarged hilar lymph nodes. Diagnosis is often difficult and may need LN biopsy.
• Asthma is characterised by airway obstruction secondary to inflammation and airway hyperresponsiveness
• Arterial blood gas in asthma

  • respiratory alkalosis (low pCO2) with moderate hypoxaemia (low pO2) in most cases
  • respiratory acidosis (normal or high pCO2) occurs when the fatigue of the inspiratory muscles is present
• Asthma is commonly worse at night - several factors may cause this:

  • allergens in the bedroom (e.g. house dust mite, mould)
  • the air is usually coldest
  • nasal secretions can drip into the chest
  • natural cortisol levels are lower
• features of nail clubbing:

  • softening of the nail bed
  • loss of nail bed angle (Schamroth's window diamond)
  • increased convexity of the nail fold
  • drumsticking of the finger distally

  
• Conditions causing finger clubbing

  • lung cancer
  • bronchiectasis
  • lung abscesses
  • hypersensitivity pneumonitis
  • HPOA
  • CF
  • Sarcoidosis
  • Asbestosis
  • TB
  • Fibrosis
• Diffusing capacity

  • diffusing capacity of lungs for CO
  • measures ability of lungs to transport inhaled gas from alveoli to pulmonary capillaries
• What helps prevent pulmonary oedema in healthy pulmonary circulation?

  Oncotic pressure exceeds pulmonary capillary hydrostatic pressure
• Causes of pulmonary oedema

  • rise in pulmonary capillary hydrostatic pressure
  • endothelial damage leads to vascular permeability to protein, so a decrease in oncotic gradient
  • Lymphatic obstruction compromises normal lymph drainage
• pack year history = number of packs per day x number of years smoked (1 pack = 20 cigarettes)
• Diffusion capacity (transfer factor) - TLCO

  • carbon monoxide used to measure TLCO
  • CO binds to Hb, keeping plasma partial pressure at zero
  • a single vital capacity inhaled containing:
  • 0.3% CO
  • 10% He (to calculate initial V and pp of CO)
  • breath held in for 10 sec then exhaled and gases measured
• Decreased DLCO (<80% predicted)

  • Obstructive lung disease
  • Parenchymal lung disease
  • Pulmonary vascular disease
  • Anaemia
• Increased DLCO (>120- 140% predicted)

  • Pulmonary haemorrhage
  • Polycythaemia
  • Left to right shunt
• Primary pneumothorax - without an apparent cause and in the absence of significant lung disease
• Secondary pneumothorax - occurs in the presence of existing lung disease
• Pneumothorax risk factors

  • smoking
  • pre-existing lung conditions
  • connective tissue diseases (Marfans)
• Treatment for myasthenia gravis:

  mestinon (pyridostigmine) - acetyl choline esterase inhibitor
• Management of Myasthenia gravis

  • symptomatic
  • pyridostigmine, ventilation
  • immunomodulation
  • steroids, IVIG, plasma exchange, rituximab
  • look for thymoma or thymic hyperplasia
• Contraindications for lung function testing

  • thoracic/abdominal surgery
  • brain, eye, ENT surgery
  • pneumothorax
  • myocardial infarction
  • ascending aortic aneurysm
  • haemoptysis
  • pulmonary embolism
  • acute diarrhoea
  • angina
  • severe hypertension
  • confused/demented patients
• Normal pH = 7.38 - 7.42
• Normal pO2 = 9.5-13.0 kPa (71-100 mmHg)
• Normal pCO2 = 3.5-5.5 kPa (26-40 mmHg)
• Normal HCO3 = 22-26 mEq/L
• Normal base excess = -2 to +2 mmol/L