Air Where the Lung Should Be: A Delayed Pneumothorax After Subclavian Line Placement, With Each Assessment Finding Traced to the Pleural Physics That Produced It
Student Name
American College of Education
NUR5203: Advanced Pathophysiology and Health Assessment
Module 2 Assignment
Instructor Name
January 18, 2028
The Case
A 68-year-old composite patient on a medical unit needed a central venous catheter for parenteral nutrition after a complicated bowel resection. A subclavian catheter was placed at the bedside at 1015 after two attempts, and a chest radiograph at 1100 was read as showing correct tip position and no pneumothorax. At 1430 she told the nursing student caring for her that she felt a little short of breath. Her oxygen saturation had fallen from 96% to 91% on room air and her respiratory rate had risen from 16 to 24. The student raised the head of the bed, applied oxygen by nasal cannula and documented anxiety. At 1545 her saturation was 88% on oxygen, her heart rate 118 and her breath sounds were quieter on the right. A repeat radiograph showed a large right pneumothorax. A chest tube was placed, her lung re-expanded, and she recovered.
Central venous catheterization carries a known risk of pneumothorax. McGee and Gould (2003), reviewing the complications of the procedure, reported pneumothorax rates of 1.5% to 3.1% with the subclavian approach, compared with 0.1% to 0.2% with the internal jugular approach. A pneumothorax may not be visible on the first film if air leaks slowly through a small puncture. Film technique matters too. On an upright film, free air rises to the apex and outlines the edge of the lung, but a portable film taken with the patient lying flat or partly reclined lets air collect in front of the lung, where it is much harder to see. A clear early film therefore answers a narrower question than it seems to: it shows that no large pneumothorax was present at that moment, in that position, not that the lung is safe for the rest of the day. Nurses caring for a patient after the procedure are the ones who will see a slow leak declare itself, usually through the patient's breathing long before a second film is ordered.
How the Pleural Space Holds the Lung Open
The lungs are elastic and, left to themselves, would recoil inward and collapse. The chest wall tends to spring outward. The two are held together by the pleural space, a thin film of fluid between the visceral pleura covering the lung and the parietal pleura lining the chest wall. Because the lung pulls inward and the chest wall pulls outward, the pressure in this space is slightly below atmospheric pressure, typically a few centimeters of water below zero at rest, and it becomes more negative during inspiration as the diaphragm descends. That negative pressure is what keeps the lung expanded against its own recoil. It is also what makes the pleural space dangerous to breach: any opening to the outside or into the airways lets air flow in, because air moves from higher to lower pressure.
From a Needle Puncture to a Collapsed Lung
During the second attempt at line placement, the needle almost certainly punctured the apex of the right lung, where the subclavian vein lies close to the pleura. Each breath afterward drew a small amount of air from the lung into the pleural space. As air accumulated, pleural pressure rose toward atmospheric, and the lung, no longer held open, recoiled inward. Because the leak was small and slow, the first radiograph taken 45 minutes after the procedure showed too little air to see. By the afternoon, enough had collected to collapse much of the right lung.
A collapsed lung still receives blood flow from the pulmonary arteries, but the collapsed alveoli receive no air. Blood flowing past those airless alveoli stays deoxygenated, a form of shunt, and this blood mixes with oxygenated blood from the other lung, lowering arterial oxygen levels. Hypoxic vasoconstriction in the collapsed lung partly limits the shunt, which is why saturation often falls gradually rather than all at once. The brain senses falling oxygen and rising effort, and breathing becomes faster. The patient's first complaint, a little short of breath, was the earliest outward sign of a lung that had already begun to collapse.
When a Pneumothorax Becomes Tension
In some cases the tear in the lung acts as a one-way valve: air enters the pleural space during inspiration but cannot leave during expiration. Pressure in the affected side then rises above atmospheric, compressing the lung completely and pushing the mediastinum toward the other side. The rising pressure also compresses the great veins and reduces blood returning to the heart, so that cardiac output falls. This is a tension pneumothorax, and it is immediately life threatening.
Nurses are often taught to look for tracheal deviation and hypotension, but these are late findings. Leigh-Smith and Harris (2005), reviewing the evidence, concluded that in patients who are breathing on their own, respiratory distress, tachycardia and falling oxygen saturation are the consistent early features, while hypotension and tracheal deviation tend to appear late, if at all. The case patient's rising heart rate at 1545, together with falling saturation on oxygen, meant that her pneumothorax was large and may have been beginning to affect her circulation.
Each Finding and Its Cause
Diminished breath sounds on the right: sound from the airways is poorly transmitted through air in the pleural space, and the collapsed lung moves little air. Hyperresonance to percussion on the right: air in the pleural space resonates more than lung tissue. Reduced chest expansion on the right: the collapsed lung no longer inflates, so that side of the chest moves less. Tachypnea and falling saturation: shunt through the collapsed lung and the drive to breathe faster. Tachycardia: compensation for hypoxemia and, as pressure rises, for falling venous return. Anxiety: a real symptom of hypoxemia and breathlessness, not an alternative explanation for them. Current guidance on pleural disease recommends that management be guided by symptoms and physiological effect rather than by size on the radiograph alone (Roberts et al., 2023).
What Students Need to Be Taught
Three teaching points follow. First, a procedure's known complications define what to watch for afterward. Students should be taught that after a subclavian line, new breathlessness is pneumothorax until proven otherwise, and that a clear first film does not rule out a slow leak. Second, anxiety is a finding to be explained, not an explanation. The student documented anxiety and missed the chance to compare breath sounds side to side. In the author's clinical group, students now practice a two-minute focused respiratory assessment that always compares both sides for sounds, percussion and expansion. Third, the classic signs of tension are late. Students should escalate on rising respiratory rate, falling saturation and rising heart rate, without waiting for hypotension or a shifted trachea. The next module turns from a single condition to two conditions that present alike and must be separated by their mechanisms.
References
Leigh-Smith, S., & Harris, T. (2005). Tension pneumothorax: Time for a re-think? Emergency Medicine Journal, 22(1), 8-16. https://doi.org/10.1136/emj.2003.010421
McGee, D. C., & Gould, M. K. (2003). Preventing complications of central venous catheterization. New England Journal of Medicine, 348(12), 1123-1133. https://doi.org/10.1056/NEJMra011883
Roberts, M. E., Rahman, N. M., Maskell, N. A., Bibby, A. C., Blyth, K. G., Corcoran, J. P., Edey, A., Evison, M., de Fonseka, D., Hallifax, R., Harden, S., Lawrie, I., Lim, E., McCracken, D. J., Mercer, R., Mishra, E. K., Nicholson, A. G., Noorzad, F., Opstad, K., ... Sivasothy, P. (2023). British Thoracic Society guideline for pleural disease. Thorax, 78(Suppl. 3), s1-s42. https://doi.org/10.1136/thorax-2022-219784
How this NUR 5203 Module 2 example is structured
NUR 5203 Module 2 often analyzes a respiratory case and links each assessment finding to its physiological cause; your classroom's instructions decide the case and the depth of assessment required. This example presents the case with timed findings, explains normal pleural mechanics, traces the mechanism of collapse and of tension, links each finding to its cause with evidence on which findings appear early and late, and ends with teaching points for students.
NUR5203 Module 2 questions, answered
What does NUR5203 Module 2 usually ask for?
NUR5203 Module 2 often asks you to analyze a respiratory case and explain each assessment finding by its physiological cause, at graduate depth. Your classroom's instructions decide the case and whether teaching points are required.
How do I explain respiratory findings by mechanism?
Start with normal ventilation and the pressures involved, then explain what changes in the condition, and link each finding, such as breath sounds, percussion note or oxygen saturation, to the specific change that produces it.
Should I include what the nurse did wrong in the case?
Describe what happened factually and use it to identify teaching points, without blaming an individual. The course's educator focus makes these missed cues valuable learning material.
Write yours, or have the desk draft it
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