NU 621 Unit 3: sample paper, in real form

From Inhaled Injury to Air Trapping: The Pathophysiology of Chronic Obstructive Pulmonary Disease in a 63-Year-Old Adult

Author Name

Department of Nursing, Herzing University

NU 621: Advanced Pathophysiology

Unit 3 Assignment

Instructor Name

February 9, 2026

The Case

A 63-year-old man presents to a family practice clinic with three days of worsening breathlessness and a change in his sputum from clear to thick and yellow. For the past four years he has coughed most mornings and has raised sputum on most days of the month. Over the last 18 months he has stopped carrying groceries up the single flight of stairs to his apartment without pausing twice. He has a 42 pack-year smoking history and quit eleven months ago. Vital signs today are temperature 98.8 F, heart rate 96, respirations 24, blood pressure 138/84, and oxygen saturation 88 percent on room air. He speaks in short phrases, sits leaning forward on his forearms, and exhales through pursed lips.

Examination shows an increased anteroposterior chest diameter, accessory muscle use at the neck, hyperresonant percussion in both lung fields, and distant breath sounds with a prolonged expiratory phase at an inspiratory to expiratory ratio of roughly 1 to 3. Scattered expiratory wheeze is heard bilaterally, with coarse rhonchi at the bases that partly clear with cough. Heart sounds are distant, and there is trace ankle edema. Post-bronchodilator spirometry from three months ago records a forced expiratory volume in one second to forced vital capacity ratio of 0.58, with a forced expiratory volume in one second at 46 percent of predicted. Arterial blood gas today shows pH 7.34, carbon dioxide tension 52 mm Hg, oxygen tension 58 mm Hg, and bicarbonate 28 mEq/L.

Normal Airflow and Gas Exchange

Airflow out of a healthy lung is passive and depends on two structures working together. Elastin fibers in the alveolar walls store energy during inspiration and release it during expiration, generating the pressure gradient that empties the lung without muscular effort. Those same alveolar attachments tether the walls of the small conducting airways, which carry no cartilage of their own and stay open only because the surrounding tissue pulls outward on them. Airways smaller than 2 mm in diameter therefore remain patent during expiration through radial traction rather than through structural rigidity (Hogg & Timens, 2009). Above them, mucociliary transport clears inhaled particles upward through a thin fluid layer moved by coordinated ciliary beating.

Gas exchange depends on matching. Ventilation and perfusion are distributed so that alveolar units receiving air also receive blood, holding the ratio near 1 across most of the lung and keeping arterial oxygen and carbon dioxide within a narrow range. Carbon dioxide is far more diffusible than oxygen, and its clearance depends chiefly on alveolar ventilation, so a person with normal mechanics can raise minute ventilation and hold carbon dioxide tension steady even when demand rises. The diaphragm supplies that reserve, and it generates force efficiently only when it sits in its normal domed resting position at the end of a full expiration (Rogers, 2023).

The Disordered Mechanism

Decades of inhaled oxidants change the airway lining before they change its architecture. Cigarette smoke injures ciliated epithelium, slows ciliary beating, and drives goblet cell hyperplasia and submucosal gland enlargement, so more mucus is produced and less of it is cleared. The retained material is both a chronic irritant and a culture medium, which explains a productive morning cough years before any breathlessness. Smoke also recruits and activates neutrophils, macrophages, and CD8 positive T lymphocytes within the airway wall, and that infiltrate persists after the exposure stops, which is why airflow limitation continues to progress in patients who have already quit (Barnes, 2016).

The activated cells release neutrophil elastase and matrix metalloproteinases at rates that overwhelm local antiprotease defense, while the oxidant load in smoke inactivates alpha-1 antitrypsin, the main brake on that enzymatic activity. Elastin in the alveolar septa is then digested faster than it is replaced, and two consequences follow at once. Alveolar walls are lost, so the lung holds fewer and larger air spaces and stores less elastic energy for expiration. The small airways lose the radial traction those walls provided, and they are narrowed at the same time by wall thickening, peribronchiolar fibrosis, and luminal mucus, which together account for most of the measured resistance in advanced disease (Hogg & Timens, 2009).

Expiration is where the two losses meet. Reduced recoil lowers the driving pressure while untethered airways collapse under the positive pleural pressure that forced expiration generates, so flow limitation appears first at the end of expiration. Air that cannot leave is retained, residual volume rises, and the resting position of the lung shifts toward full inflation. The diaphragm flattens and works at a mechanical disadvantage, so every breath costs more. Ventilation is delivered to units whose capillary beds were destroyed and is wasted as dead space, while perfusion continues past mucus-filled units that receive little air. That mismatch lowers arterial oxygen and eventually raises carbon dioxide, and renal bicarbonate retention buffers the acidosis that follows (Global Initiative for Chronic Obstructive Lung Disease, 2025).

Mechanism Mapped to the Findings

The acute change that brought this patient in is the same mechanism amplified. A viral or bacterial trigger raises airway inflammation, edema, and secretion, which narrows already narrowed airways, shortens the time available for expiration, and adds trapped air to a lung that was hyperinflated at baseline (Global Initiative for Chronic Obstructive Lung Disease, 2025). Every finding at the visit then follows from a named step. The increased anteroposterior diameter and the hyperresonant percussion are hyperinflation made visible and audible. Distant breath and heart sounds reflect the air interposed between the stethoscope and its source. The prolonged expiratory phase and the wheeze are flow limitation heard in real time, and pursed lip breathing is a learned maneuver that raises pressure inside the airway and delays the collapse described above.

The numbers close the same loop. A post-bronchodilator ratio of 0.58 documents obstruction that does not reverse, which is what separates this disease from asthma and serves as the spirometric criterion for the diagnosis (Global Initiative for Chronic Obstructive Lung Disease, 2025). An oxygen saturation of 88 percent reflects mismatch rather than a diffusion barrier alone. A carbon dioxide tension of 52 mm Hg with a bicarbonate of 28 mEq/L and a pH of 7.34 describes retention that developed slowly enough for renal compensation to nearly keep pace, which is a chronic pattern and not an acute one. The trace ankle edema is the first sign of the next stage, in which sustained hypoxemia drives pulmonary vasoconstriction and vascular remodeling and the right ventricle begins to fail (Centers for Disease Control and Prevention, 2024).

References

Barnes, P. J. (2016). Inflammatory mechanisms in patients with chronic obstructive pulmonary disease. Journal of Allergy and Clinical Immunology, 138(1), 16-27.

Centers for Disease Control and Prevention. (2024). Chronic obstructive pulmonary disease (COPD). U.S. Department of Health and Human Services. https://www.cdc.gov/copd/

Global Initiative for Chronic Obstructive Lung Disease. (2025). Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease: 2025 report. https://goldcopd.org/

Hogg, J. C., & Timens, W. (2009). The pathology of chronic obstructive pulmonary disease. Annual Review of Pathology: Mechanisms of Disease, 4, 435-459.

Rogers, J. L. (Ed.). (2023). McCance & Huether's pathophysiology: The biologic basis for disease in adults and children (9th ed.). Elsevier.