Unit
- Upper respiratory tract: The nose, nasal cavity, pharynx, and larynx filter, warm, and humidify inspired air. The nasal mucosa contains cilia that trap particulates, while the larynx protects the lower airway during swallowing.
- Lower respiratory tract: The trachea branches into right and left main bronchi, which divide into segmental bronchi, bronchioles, and terminal bronchioles. This branching increases surface area for gas exchange.
- Alveoli: Approximately 300 million alveolar sacs provide a surface area of about 70 square meters for oxygen and carbon dioxide exchange. Type I pneumocytes form the thin barrier, while Type II cells produce surfactant that reduces surface tension.
- Pleura: The visceral pleura covers the lungs, and the parietal pleura lines the thoracic cavity. A thin layer of pleural fluid allows frictionless movement during breathing.
- Thoracic cage: The ribs, sternum, and thoracic vertebrae enclose and protect the lungs. The diaphragm is the primary muscle of inspiration, contracting to increase thoracic volume.
- Blood supply: The pulmonary circulation delivers deoxygenated blood to the alveoli for gas exchange, while the bronchial circulation supplies oxygenated blood to lung tissue itself.
- Lymphatic system: Lymphatic vessels drain excess fluid and remove particulate matter from the lung interstitium, maintaining fluid balance and immune surveillance.
- Innervation: The autonomic nervous system regulates airway diameter and secretion. Sympathetic stimulation causes bronchodilation, while parasympathetic stimulation promotes bronchoconstriction and mucus secretion.
- Mucociliary clearance: Coordinated ciliary beating on epithelial cells propels mucus and trapped particulates upward toward the pharynx for removal. This defense mechanism clears inhaled pathogens and debris, and its impairment underlies conditions such as chronic bronchitis and primary ciliary dyskinesia.
- Pulmonary surfactant composition: Surfactant consists of phospholipids, primarily dipalmitoylphosphatidylcholine, along with surfactant proteins A, B, C, and D. It lowers alveolar surface tension to prevent collapse at end expiration and enhances innate immunity by opsonizing bacteria and facilitating macrophage clearance.
- Lung volumes and capacities: Standard spirometry measures tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume. Combining these yields vital capacity, total lung capacity, and functional residual capacity, which are essential for distinguishing restrictive from obstructive pulmonary disorders.
Scope of Practice
Role: Respiratory Care Practitioner in Diagnostic Assessment
Within scope:
- Performing patient interview to obtain respiratory history and symptoms.
- Measuring and recording baseline respiratory rate, oxygen saturation, and breath sounds.
- Assisting with non-invasive diagnostic assessments such as peak flow measurement.
- Educating patients on breathing techniques and pulmonary hygiene.
- Documenting observations in the electronic health record.
Outside scope:
- Diagnosing pulmonary conditions or ordering diagnostic tests independently.
- Interpreting chest imaging or histopathological specimens.
- Prescribing medications or adjusting ventilator settings without physician order.
- Performing invasive procedures such as bronchoscopy or thoracentesis.
- Providing medical clearance for procedures requiring pulmonary evaluation.
Quick Revision
- The respiratory system includes upper and lower tracts, alveoli, pleura, and thoracic cage.
- Key cells include Type I pneumocytes for gas exchange and Type II pneumocytes for surfactant production.
- Autonomic innervation modulates airway caliber and mucus secretion.
- Respiratory care practitioners assess and educate but do not diagnose or prescribe.