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This is the complete lecture note for MED402 Respiratory. You can read it online below, open it in the full viewer, or download the PDF for offline study. It pairs with the course's video lectures, so you can read and watch together.
Course code: MED 402 Course title: Respiratory Course credit load: 2 Units Series 1: Fundamentals of Respiratory Evaluation and Clinical Skills • Part 1.1: Anatomy and Physiology of the Respiratory System o Sub Part 1.1.1: Gross anatomy of the respiratory tract o Sub Part 1.1.2: Mechanics of breathing and lung volumes o Sub Part 1.1.3: Gas exchange and control of ventilation • Part 1.2: Respiratory History Taking o Sub Part 1.2.1: Cardinal respiratory symptoms o Sub Part 1.2.2: Past medical, drug, occupational, and social history o Sub Part 1.2.3: Systems review and functional assessment • Part 1.3: Physical Examination of the Respiratory System o Sub Part 1.3.1: General inspection and peripheral signs o Sub Part 1.3.2: Chest inspection and palpation o Sub Part 1.3.3: Percussion and auscultation • Part 1.4: Common Respiratory Investigations o Sub Part 1.4.1: Chest X-ray interpretation o Sub Part 1.4.2: Pulmonary function tests
o Sub Part 1.4.3: Arterial blood gas analysis Introduction The respiratory system is responsible for delivering oxygen to the body and eliminating carbon dioxide. Diseases of the respiratory system are among the most common causes of morbidity and mortality in Nigeria and globally, including pneumonia, tuberculosis, asthma, and chronic obstructive pulmonary disease. Competent evaluation of the respiratory patient requires a foundation in respiratory anatomy and physiology, systematic history taking and physical examination, and the ability to select and interpret the key investigations. This Series provides that foundation. It covers the anatomy of the respiratory tract, the mechanics and physiology of breathing, and the clinical approach to the respiratory patient from history through to physical examination. It then introduces the most important investigations in respiratory medicine: the chest X-ray, pulmonary function tests, and arterial blood gas analysis. These skills underpin all the clinical respiratory knowledge covered in subsequent Series of this course. A systematic approach to respiratory assessment, applied consistently to every patient, ensures that important findings are not missed and that the clinical reasoning leading to diagnosis and management is grounded in objective data. Series Learning Outcomes Upon completing this Series, you should be able to: • SLO 1.1 describe the gross anatomy of the respiratory tract and the mechanics of breathing, lung volumes, and gas exchange (Linked to Part 1.1), • SLO 1.2 explain the control of ventilation and the physiological basis of common respiratory symptoms (Linked to Part 1.1),
• SLO 1.3 conduct a systematic respiratory history covering the cardinal symptoms, past history, occupational and social history, and functional assessment (Linked to Part 1.2), • SLO 1.4 perform and describe the findings of a systematic respiratory examination including inspection, palpation, percussion, and auscultation (Linked to Part 1.3), and • SLO 1.5 interpret a chest X-ray, pulmonary function tests, and arterial blood gas analysis in the context of common respiratory conditions (Linked to Part 1.4). 1.1 Anatomy and Physiology of the Respiratory System 1.1.1 Gross anatomy of the respiratory tract The respiratory tract is divided into the upper respiratory tract (nose, nasopharynx, oropharynx, larynx) and the lower respiratory tract (trachea, bronchi, bronchioles, and alveoli). The trachea bifurcates at the carina (at the level of the angle of Louis, T4/5) into the right and left main bronchi; the right main bronchus is shorter, wider, and more vertical, making it the more common site of inhaled foreign bodies. The lungs are paired organs occupying the pleural cavities. The right lung has three lobes (upper, middle, and lower); the left lung has two lobes (upper and lower, with the lingula corresponding to the right middle lobe). The functional unit of gas exchange is the acinus, comprising the respiratory bronchioles, alveolar ducts, and alveoli. The pleura consists of visceral (covering lung surface) and parietal (lining chest wall) layers; the potential space between them normally contains a small amount of lubricating fluid. Fill in the blank: The right main bronchus is shorter, wider, and more vertical than the left, making it the more common site of inhaled foreign ________; the right lung has three lobes; the left lung has two lobes. 1.1.2 Mechanics of breathing and lung volumes Inspiration is an active process driven by contraction of the diaphragm (the primary muscle of inspiration) and the external intercostal muscles, which increase chest dimensions and reduce
intrathoracic pressure, drawing air into the lungs. Expiration is passive at rest but active during exercise and in obstructive lung disease (using internal intercostals and abdominal muscles). Key lung volumes include: tidal volume (TV) (volume breathed in and out in one normal breath; approximately 500 mL at rest), vital capacity (VC) (maximum volume exhaled after maximum inhalation; normally 4 to 5 litres), total lung capacity (TLC) (all air in the lungs at full inspiration), residual volume (RV) (air remaining after maximum exhalation), and functional residual capacity (FRC) (air remaining after normal exhalation). FEV1 (forced expiratory volume in 1 second) and FVC (forced vital capacity) are the key spirometric measurements. Fill in the blank: Inspiration is active (diaphragm and external intercostals); expiration is passive at rest; key lung volumes include tidal volume (500 mL), vital capacity, TLC, residual volume, and FRC; FEV1 and FVC are key ________ measurements. 1.1.3 Gas exchange and control of ventilation Gas exchange occurs across the alveolar-capillary membrane: oxygen diffuses from alveolar air (PO2 approximately 100 mmHg) into pulmonary capillary blood, and carbon dioxide diffuses in the opposite direction. Efficient gas exchange requires ventilation-perfusion (V/Q) matching; V/Q mismatch is the most common cause of hypoxaemia in respiratory disease. The normal arterial PO2 is 10 to 13 kPa (75 to 100 mmHg) and PaCO2 is 4.7 to 6.0 kPa (35 to 45 mmHg). Ventilation is controlled by the respiratory centre in the brainstem (medulla and pons), which responds to chemical stimuli: central chemoreceptors in the medulla respond to PaCO2 (the primary drive to breathe), and peripheral chemoreceptors in the carotid and aortic bodies respond to PaO2, PaCO2, and pH. In patients with chronic hypercapnia (as in severe COPD), the hypoxic drive (low PaO2 stimulating peripheral chemoreceptors) may become the primary respiratory stimulus, making high-flow oxygen dangerous. Fill in the blank: Gas exchange requires V/Q matching; hypoxaemia is most commonly caused by V/Q ________; the primary drive to breathe is PaCO2 via central chemoreceptors; in chronic hypercapnia, the hypoxic drive may become primary.
Figure 1.1: Respiratory anatomy, lung volumes, and the control of ventilation Pilot questions 1.1 1. Describe the gross anatomy of the respiratory tract including the upper and lower respiratory tracts. (Linked to SLO 1.1) 2. Explain why the right main bronchus is more commonly affected by inhaled foreign bodies. (Linked to SLO 1.1) 3. Define tidal volume, vital capacity, total lung capacity, and residual volume. (Linked to SLO 1.1) 4. Explain the mechanics of inspiration and expiration. (Linked to SLO 1.2) 5. Explain why high-flow oxygen is dangerous in patients with chronic hypercapnia. (Linked to SLO 1.2)
1.2 Respiratory History Taking 1.2.1 Cardinal respiratory symptoms The cardinal respiratory symptoms are: cough (productive or dry; duration; character of sputum: mucoid, purulent, blood-stained), dyspnoea (onset: sudden or gradual; severity graded by MRC scale; associated wheeze or orthopnoea), haemoptysis (coughing up blood; must be distinguished from haematemesis and epistaxis; important causes: TB, lung cancer, bronchiectasis, pulmonary embolism), wheeze (musical expiratory sound; suggests airflow obstruction), chest pain (pleuritic: sharp, worse on inspiration; suggests pleurisy or pneumonia), and stridor (inspiratory high-pitched noise from upper airway obstruction). Each symptom is explored using SOCRATES and in the context of the patient's overall functional capacity. The MRC dyspnoea scale grades breathlessness from Grade 1 (breathless on strenuous exercise) to Grade 5 (too breathless to leave the house or breathless when dressing). A thorough review of the pattern, severity, duration, and associated symptoms guides the differential diagnosis of the presenting respiratory problem. Fill in the blank: Cardinal respiratory symptoms include cough, dyspnoea (graded by ________ scale), haemoptysis (TB, lung cancer, bronchiectasis), wheeze (airflow obstruction), pleuritic chest pain, and stridor (upper airway obstruction). 1.2.2 Past medical, drug, occupational, and social history The past medical history in respiratory disease must include: previous respiratory conditions (asthma, TB, pneumonia, bronchiectasis), childhood respiratory illness, atopy (eczema, allergic rhinitis, food allergies), cardiovascular disease (left heart failure causes dyspnoea and pulmonary oedema), and malignancy (lung metastases or primary lung cancer). The drug history is critical: several drugs cause pulmonary toxicity, including amiodarone (pulmonary fibrosis), methotrexate (pneumonitis), NSAIDs and aspirin (exacerbate asthma), and ACE inhibitors (dry persistent cough in approximately 15 percent of patients). The occupational history is essential: ask about dust, fume, chemical, asbestos, and animal exposure; occupational lung diseases include pneumoconiosis (coal dust), asbestosis, silicosis,
and occupational asthma. The social history covers smoking (pack years: number of packs per day multiplied by years smoked), alcohol use, and housing conditions. Fill in the blank: Drug-induced respiratory conditions include ACE inhibitor cough, amiodarone pulmonary fibrosis, and aspirin-exacerbated asthma; the occupational history identifies dust, asbestos, and fume exposure causing pneumoconiosis, silicosis, or ________ asthma. 1.2.3 Systems review and functional assessment The systems review in a respiratory patient should cover cardiovascular symptoms (orthopnoea, PND, ankle oedema: cardiac causes of dyspnoea), upper respiratory symptoms (nasal polyps, post-nasal drip,
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