# 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?

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=542612  
> language: ko  
> 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?

## 보기

1. Sudden increase in peak inspiratory pressure from 25 to 40 cmH2O with decreased tidal volumes **✔ 정답**
2. Oxygen saturation decreasing from 98% to 94% over a period of 2 hours
3. Heart rate increasing from 88 to 102 bpm during a suctioning procedure
4. Ventilator alarm indicating patient-ventilator asynchrony for 30 seconds

**정답: 1**

## 해설

Sudden increase in peak inspiratory pressure with decreased tidal volumes indicates critical airway obstruction or pneumothorax requiring immediate intervention. Other findings require monitoring but are not immediately life-threatening.

## 심화 해설

Clinical Judgment
This question assesses your recognition and analysis skills in identifying the most dangerous sign of deterioration in a patient on a mechanical ventilator. The key is to recognize the pattern of a sudden increase in peak inspiratory pressure (PIP) accompanied by a decrease in tidal volume. This signifies not just a simple ventilator setting issue, but an acute change in the patient's lung condition. The most common and dangerous cause is a tension pneumothorax, which can lead to death without immediate medical intervention. Other options require monitoring and evaluation, but they do not represent an immediate life threat like this sign does.

Memory Tip:
**P**IP **U**p, **T**idal Volume **D**own = **P**anic **U**ntil **T**ension **D**efinitely Ruled Out! If you see this pattern, suspect a **pneumothorax** first.

KR vs US:
In Korea, the initial response to a ventilator alarm is often a collaboration between nurses and respiratory therapists. In the US NCLEX, the nurse's ability for independent judgment and immediate primary assessment (e.g., chest auscultation, checking breath sounds, inspecting tube placement and the circuit) is emphasized more, with a clear flow of reporting afterward. Questions asking for the "MOST concerning" finding test this ability for prioritization and clinical reasoning.

## 임상 시나리오

Clinical Practice Guide
Immediate actions when PIP rises sharply and tidal volume decreases: Remember D.O.T.S.
Disconnect from vent: Temporarily disconnect the patient from the ventilator and supply 100% oxygen with a manual resuscitation bag (Ambu bag) while assessing resistance.
Observe & Listen: Immediately check chest movement symmetry, skin color, and breath sounds. Loss of breath sounds on one side is a strong sign of pneumothorax.
Tube & Circuit check: Check the endotracheal tube position, cuff inflation, circuit kinks, and water accumulation.
Summon help: Immediately report to the respiratory therapist and physician.

Caution
In SATA (Select All That Apply) questions asking about "the nurse's immediate action when a ventilator alarm sounds," remember the principle of checking the patient first, then the machine. Choose the option that assesses the patient's respiratory status and level of consciousness first. Touching the machine's power or settings first is a trap.

## 핵심 개념

- **Peak Inspiratory Pressure** — Peak inspiratory pressure. This is the maximum pressure required to deliver the set tidal volume from the ventilator into the patient's lungs. It is influenced by airway resistance and lung-chest wall compliance. A sudden rise may indicate airway obstruction, bronchospasm, atelectasis, pneumothorax, or secretion accumulation.
- **Tidal Volume** — Tidal volume. It is the amount of air that enters and leaves the lungs during a single breath. It is one of the important variables set on a ventilator. A decrease in Vt accompanied by an increase in PIP strongly suggests a mechanical problem (e.g., kinked tube) or an acute change in the patient's lung condition (e.g., decreased compliance).
- **Patient-Ventilator Asynchrony** — Patient-ventilator dyssynchrony. It is a mismatch between the patient's spontaneous breathing efforts and the ventilatory support provided by the ventilator. The patient may become uncomfortable, work of breathing increases, and it can impair oxygenation and carbon dioxide removal.
- **Tension Pneumothorax** — Tension pneumothorax. This is a condition where air enters the pleural cavity but cannot escape, causing pressure to gradually increase. As a result, the lung on that side completely collapses, and the mediastinum shifts to the opposite side, compressing the vena cava and rapidly reducing cardiac output and blood pressure. It is a medical emergency. The risk of occurrence is high in patients on mechanical ventilation.
- **Assist-Control (AC) Mode** — Assist-control mode. A common ventilator mode that delivers a set tidal volume whenever the patient attempts to breathe spontaneously (assist), and if no spontaneous breathing occurs within the set respiratory rate, the machine provides mandatory breaths (control). It supports the patient's breathing efforts while ensuring a minimum minute ventilation.

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