# A nurse is caring for a patient on mechanical ventilation with assist-control mode. Which assessment finding would be the most concerning and require immediate intervention?

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> subject: Critical Care

## 문제

A nurse is caring for a patient on mechanical ventilation with assist-control mode. Which assessment finding would be the most concerning and require immediate intervention?

The nurse is monitoring a critically ill patient who has been on mechanical ventilation for 3 days following respiratory failure from pneumonia.

## 보기

1. Peak inspiratory pressure of 28 cmH2O with no change from baseline
2. Oxygen saturation of 94% on FiO2 of 0.60
3. Sudden increase in peak inspiratory pressure from 25 to 40 cmH2O with decreased breath sounds on the left side **✔ 정답**
4. Respiratory rate of 22 breaths per minute above the set ventilator rate

**정답: 3**

## 해설

A sudden significant increase in peak inspiratory pressure with decreased breath sounds indicates pneumothorax, a life-threatening emergency requiring immediate intervention. Other findings represent stable or less urgent conditions.

## 심화 해설

Analysis of the Most Concerning Assessment Finding

The correct answer is the sudden increase in peak inspiratory pressure (PIP) from 25 to 40 cmH2O accompanied by decreased breath sounds on the left side. This combination of findings represents a classic presentation of a tension pneumothorax, a life-threatening emergency requiring immediate needle decompression.

The underlying pathophysiology connects directly to the risks of positive-pressure ventilation. When a patient receives mechanical ventilation, positive pressure is forced into the airways. If barotrauma occurs, air can escape from a ruptured alveolus into the pleural space. As this air accumulates and cannot exit, it collapses the affected lung (causing the decreased breath sounds) and shifts the mediastinum, compressing the great vessels and the contralateral lung. The sudden, sharp rise in PIP reflects the dramatically increased pressure needed to deliver a tidal volume against the resistance created by the trapped air under tension .

The other options, while requiring nursing attention, do not indicate an immediately life-threatening crisis. A stable PIP of 28 cmH2O is within a commonly monitored range and does not signal an acute change. An oxygen saturation of 94% on an FiO2 of 0.60 indicates a P/F ratio of approximately 156, which reflects ongoing ARDS or severe hypoxemia but is a chronic state for this patient, not a sudden deterioration demanding emergent intervention. A respiratory rate of 22 breaths per minute above the set rate indicates the patient is triggering additional breaths in assist-control mode, which may signal pain, anxiety, or increased ventilatory drive, but it does not carry the same immediate threat of cardiovascular collapse as a tension pneumothorax.

The critical nature of this assessment is reinforced by the understanding that mechanical ventilation, while essential for managing respiratory failure, inherently carries the risk of barotrauma, including pneumothorax . Furthermore, the concept of patient self-inflicted lung injury (P-SILI) is relevant to monitoring ventilated patients. P-SILI results from the combined forces of the positive pressure from the ventilator and the negative pressure generated by the patient’s own strong inspiratory efforts, which can cause excessive transpulmonary pressure swings and regional lung stress . In a patient fighting the ventilator or with a high respiratory drive, these forces can increase the risk of barotrauma, making the nurse's vigilant monitoring for a sudden change in PIP and unilateral breath sounds a critical safety function. The immediate recognition of this pattern as a tension pneumothorax is paramount, as the condition can rapidly progress to pulseless electrical activity and cardiac arrest if not promptly decompressed.

## 임상 시나리오

Clinical Scenario

A 68-year-old patient intubated for pneumonia develops a sudden rise in peak inspiratory pressure from 25 to 40 cmH2O. Auscultation reveals absent breath sounds on the left. The high-pressure alarm is sounding, and the patient becomes tachycardic and hypotensive.

Immediate Actions

- Disconnect the ventilator and manually ventilate with a bag-valve-mask on 100% oxygen.

- Auscultate both lung fields to confirm absent or diminished breath sounds on the affected side.

- Assess for tracheal deviation, distended neck veins, and subcutaneous emphysema.

- Prepare for emergency needle decompression: 14-16 gauge needle inserted at the 2nd intercostal space, midclavicular line on the affected side.

- Prepare for chest tube insertion following decompression.

Nursing Priorities

- Maintain airway and oxygenation; do not leave the patient unattended.

- Notify the provider and respiratory therapist immediately.

- Ensure emergency equipment is at the bedside: thoracostomy tray, chest drainage system.

- Monitor vital signs continuously, watching for worsening hypotension and hypoxemia.

- Document the event, including PIP before and after, breath sound changes, and time of decompression.

Prevention Strategies

- Use lung-protective ventilation strategies: tidal volume 6-8 mL/kg ideal body weight, plateau pressure less than 30 cmH2O.

- Monitor PIP and plateau pressures trends every 2-4 hours and with any ventilator setting change.

- Auscultate breath sounds at least every 4 hours and note any asymmetry.

- Assess for risk factors: high PIP, underlying lung disease (COPD, ARDS), prolonged ventilation.

## 핵심 개념

- **Tension pneumothorax** — A life-threatening condition where air accumulates in the pleural space under pressure, collapsing the lung and shifting the mediastinum, impairing venous return and cardiac output.
- **Peak inspiratory pressure (PIP)** — The highest pressure measured in the airways during the inspiratory phase of a mechanical breath, reflecting airway resistance and lung compliance.
- **Assist-control (AC) mode** — A ventilator mode that delivers a preset tidal volume for every breath, whether initiated by the patient or the machine, at a set minimum rate.
- **Barotrauma** — Lung injury caused by elevated transalveolar pressure during positive-pressure ventilation, which can lead to alveolar rupture and air leaks.
- **Needle decompression** — An emergency procedure where a large-bore needle is inserted into the pleural space to release trapped air and relieve tension pneumothorax.

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