Anatomy, pathophysiology , and investigations of the respiratory system

Anatomy, pathophysiology, and investigations of the respiratory system

د.خلدون العباﭕﭽي
كلية طب نينوى- المرحلة الرابعة
Functional anatomy
Upper respiratory tract: nose, nasopharynx, larynx
(ciliated epithelium)
Lower RT: trachea, bronchi, 64,000 terminal bronchiole,
alveoli, acini (ciliated epithelium)
Right lung: upper lobe (apical, anterior, posterior
bronchopulmonary segments), middle lobe (medial &lateral), lower
lobe (apical, anterior, posterior, medial, lateral).
Left lung: upper lobe (apical, anterior, posterior, lingular), lower lobe (apical, anterior, posterior, lateral).
Sensory nerves: supply all, cough reflex
Acinus: gas exchange unit, lined by flat epith.cells (type 1 pneumocytes) and cuboidal (type II pneumocytes) which produce surfactant (phospholipid, reduce surface tension, preventing alveolar collapse, form type I after lung injury).
Perfusion: right ventricle → low resistance pulmonary vessels →capillary network around alveoli, gas exchange.

Lung defences

Physical defences: nasal hair & cilia, larynx protects lower airways during swallowing and vomiting.
Mucociliary function: particles >0.5(m trapped by lining fluid of trachea and bronchi and cleared by mucociliary escalators, goblet cells→mucus. It is reduced by: polluants, smoking, anaesthesia, bacteria, viruses and primary ciliary dyskinesia→sinusitis and bronchiectasis.
Surfactant protein A opsonise bacteria. IgG, IgA, IgM, complement, peptides, (I antitrypsin.
Alveolar macrophages.


Hypoxia: pa 02 <8kpa
Alveolar capillary membrane: ventilation- perfusion if deranged →
hypoxia and hypercapnoea
Causes
Ventilation-perfusion mismatch * Bronchial obstruction (secretions, oedema, asthma, tumors) * Destruction of elastic tissue e.g emphysema * Lung collapse * Chest wall deformity.
Right to left shunt e.g cyanotic congenital heart dis.
Decreased 02 carrying capacity e.g anemia, CO poisoning.
↓02 → constrict pulmonary arterioles
↑CO2→ dilates pulmonary arterioles

Hypercapnoea: paCO2 >6.6 kpa Due to alveolar hypoventilation,
Causes
Central brain stem lesion, sleep apnea syndrome
Neuromuscular: peripheral neuropathy, myopathy, myasthenia gravis
Chest wall abnormality: kyphoscoliosis, trauma, ankylosing spondylitis.
Pulmonary disease: COPD, severe asthma.

Respiratory acidosis = ↑CO2

Respiratory alkalosis = ↓CO2
Respiratory centre stimulant: ↑paCO2, ↓pa02, acidosis, CNS lesion
Respiratory centre depressant: brain stem lesion, sedatives, opiates,
hypothermia, hypothyroidism


Cor pulmonale Right ventricular hypertrophy or failure secondary to pulmonary hypertension due to increased pulmonary vascular resistance e.g COPD, pul.embolism. Normal pulmonary circulation pressure 24/9 mm Hg

Investigations of respiratory diseases

Plain chest radiograph: PA & lateral
CT scan: * sensitive & accurate, assess stage of lung cancer * Contrast enhanced spiral CT for pulmonary embolism * High resolution CT scan: interstitial lung fibrosis, bronchiectasis

Ultrasound

Sensitive at detecting pleural fluid.
Directs pleural biopsy.
Investigate empyema and facilitate pus drainage.
Needle biopsy of superficial lymph node or chest wall mass.
Endobronchial ultrasound image and sample peribronchial lymph nodes.
Ventilation-perfusion lung scan - xe133 gas inhaled (ventilation scan), Tc99m labeled
macroaggregates of albumin i.v (perfusion scan)
- Pulmonary embolism: filling defect in perfusion scan which does
not match ventilation scan.

Pulmonary angiography - Contrast injected into main pulmonary artery. - Definitive diagnosis of pulmonary embolism.
- Measure right heart and pulmonary artery pressures.
- Administration of thrombolytics
- Digital subtraction angiography: more sensitive,
post contrast image- precontrast image= final digital image.
- rarely used as CT pulmonary angio is widely available.


Positron emission tomography PET - Use 18-fluorodeoxyglucose FDG - Differentiate between malignant & benign lesions in pulmonary
nodules, mediastinal lymph nodes and distant metastasis.
- Prevent 20% unnecessary surgery in non-small cell
lung cancer.

Endoscopy a. Laryngoscopy b. Bronchoscopy: biopsy, bronchial brush, wash, aspirate for
Cytology & bacteria, transbronchial biopsy.
c. Mediastinoscopy
d. Thoracoscopy: video assisted- lung biopsy, reduces
the need for open lung biopsy e.g interstitial lung disease.

7. Pleural aspiration & biopsy

Abrams needle, blind pleural biopsy for pleural diseases
e.g T.B, tumors.

8. Transthoracic needle biopsy under radiological guidance, useful for

peripheral lung lesions.

9. Skin test: tuberculin, allergic disease

10. Immunological & serological tests
Pneumoccocal antigen, influenza virus, legionella,
mycoplasma, chlamydia, viruses, aspergillosis, allergic alveolitis.


11. Microbiological investigation: Sputum, swabs, blood, washings for
TB, bacteria, fungi & viruses

12. Histology & cytology

13. Lung function test

14. Arterial blood gas analysis

Pa 02 12-15 kpa
pa C02 4.5-6kpa
02 saturation 97%
Bicarbonate 21-29 mmol/L
Hydrogen ion 37- 45 nmol/L
PH 7.4 0.4










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