Pathophysiology of pulmonary system
External structures
- Provide the external borders for the lungs
- Borders composed of:
- Sternum
- Provides anatomical landmarks for auscultation
- Rib cage
- 12 ribs and adjacent intercostal musculature assist with movement of air
- Provide anatomical landmarks for auscultation
- Vertebral column
- Provides posterior border
- Shoulder girdle
- Provides attachment for accessory muscles to support in movement of air
- Sternum
Internal structures
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Upper airways
- Entry point for air
- Comprised of nose, mouth, pharynx, and larynx
-
Lower airways
- Continue the conduction of air where gas exchange occurs
- Comprised of trachea, bronchi, bronchioles, alveolar ducts, and alveolar sacs
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Internal supporting structures
- Each lung is divided into lobes and further subdivided into bronchopulmonary segments.
- The right lung has three lobes - upper, middle, and lower - and a total of 10 bronchopulmonary segments:
- Upper lobe: 3 segments - apical, posterior, anterior
- Middle lobe: 2 segments - lateral, medial
- Lower lobe: 5 segments - superior, medial basal, anterior basal, lateral basal, posterior basal
- The left lung has two lobes - upper and lower - and typically 8 bronchopulmonary segments:
- Upper lobe: 4 segments - apicoposterior, anterior, superior lingular, inferior lingular
- Lower lobe: 4 segments - superior, anteromedial basal, lateral basal, posterior basal
- The right lung has three lobes - upper, middle, and lower - and a total of 10 bronchopulmonary segments:
- Each lung is divided into lobes and further subdivided into bronchopulmonary segments.
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Pleura
- Parietal pleura located on the outer surface and provides barrier to thoracic cage, diaphragm, and mediastinal border
- Visceral pleura located on the inner surface and provides barrier to lung
Muscles and mechanics of ventilation
Primary muscles of inspiration
- Diaphragm
- When contracted, muscle is pulled downward - inhalation
- Leads to protruded abdominal cavity
- When relaxed, muscle is in dome shape - exhalation
- Takes the natural shape of lower rib cage
- When contracted, muscle is pulled downward - inhalation
- Intercostals
- Aid in movement of rib cage
- Accessory muscles
- Scalenes
- Sternocleidomastoid
- Trapezius
- Serratus anterior
- Pectoralis muscles
Primary muscles for exhalation
- Passive recoil of activated inspiratory muscles
- Accessory muscles that can be utilized during disease state or exercise
- Quadratus lumborum
- Abdominal muscles
- Sections of intercostals
Mechanism of breathing
- Inspiration
- Activation of muscles to provide sufficient pressure gradient to allow for air to enter the lungs
- Causes the movement of bony thorax outward
- Exhalation
- Passive recoil of the activated muscle to allow air to leave the lungs
- Causes the movement of bony thorax inward
Pulmonary function test - ventilation
Obstructive vs. restrictive pulmonary disease patterns
Pulmonary function test results are used to sort disease processes into two broad patterns:
- Obstructive pattern: airflow out of the lungs is limited, so FEV1 drops more than FVC and the FEV1/FVC ratio falls below 70%. RV and TLC are often increased from air trapping. Common causes include chronic obstructive pulmonary disease (COPD), asthma, and bronchiectasis.
- Restrictive pattern: lung expansion itself is limited, so TLC and vital capacity are reduced while the FEV1/FVC ratio stays normal or increases. Common causes include pulmonary fibrosis, chest wall or neuromuscular restriction, and atelectasis.
Example: Interpreting a spirometry result
A patient’s spirometry shows an FEV1/FVC ratio of 62%, along with an increased RV. Which disease pattern does this suggest?
Answer: An obstructive pattern, such as COPD. The FEV1/FVC ratio is below 70%, and the increased RV reflects air trapping. The PTA documents the objective spirometry values and reports them to the supervising PT, who uses them to confirm the diagnosis and guide the plan of care.