# Situation: A 24-year-old woman with asthma is brought to the emergency room (ER) with wheezing and breathlessness that began after a viral cold. At home she uses only a salbutamol (albuterol) inhaler, about 6 to 8 times a week. She has no other illness, takes no other medicines, and her oxygen saturation by pulse oximetry (SpO2) is monitored continuously. Before discharge, the nurse teaches her to use a peak expiratory flow (PEF) meter with a written asthma action plan. In the traffic-light zone system, which range of her personal best PEF defines the yellow zone?

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## 문제

Situation: A 24-year-old woman with asthma is brought to the emergency room (ER) with wheezing and breathlessness that began after a viral cold. At home she uses only a salbutamol (albuterol) inhaler, about 6 to 8 times a week. She has no other illness, takes no other medicines, and her oxygen saturation by pulse oximetry (SpO2) is monitored continuously.

Before discharge, the nurse teaches her to use a peak expiratory flow (PEF) meter with a written asthma action plan. In the traffic-light zone system, which range of her personal best PEF defines the yellow zone?

## 보기

1. 60% to 79%
2. 80% to 100%
3. 50% to 79% **✔ 정답**
4. 30% to 49%

**정답: 3**

## 해설

In the traffic-light action plan, the green zone is 80% or more of personal best, the yellow zone is 50% to 79%, and the red zone is below 50%. In the yellow zone she uses her reliever, follows her written plan, and contacts her provider; in the red zone she uses her reliever and seeks emergency care.

## 심화 해설

Traffic-Light Zone System for PEF Monitoring

The written asthma action plan uses a traffic-light model to help patients interpret peak expiratory flow readings and respond appropriately. The zones are defined as percentages of the patient’s personal best PEF, which is established during a period of good asthma control.

| Zone | PEF Range | Clinical Meaning | Typical Action |
| --- | --- | --- | --- |
| Green zone | 80% to 100% of personal best | Good control; no significant airflow limitation | Continue daily controller; use reliever as needed |
| Yellow zone | 50% to 79% of personal best | Caution; worsening airflow obstruction or impending exacerbation | Use reliever; follow written plan; contact provider |
| Red zone | Below 50% of personal best | Medical alert; severe airflow limitation | Use reliever; seek emergency care immediately |

The yellow zone is the key early-warning band. A drop into the 50% to 79% range signals that airway inflammation and bronchoconstriction are increasing, even before the patient may perceive severe symptoms. This is especially important because patients with poor symptom perception may not recognize an impending exacerbation by clinical score or symptom questionnaires alone [2]. Objective PEF monitoring provides an earlier, effort-dependent but quantifiable signal of decline.

In the scenario, the patient uses salbutamol 6 to 8 times a week, which already suggests suboptimal control. Teaching her to identify the yellow zone allows her to act on a measurable threshold rather than waiting for breathlessness to become severe. The action plan in this zone typically includes increasing reliever use, possibly stepping up controller therapy per the written plan, and contacting the healthcare provider.

Watch out! Do not confuse the yellow zone lower boundary with the red zone threshold. The red zone begins below 50%, not at 60%. Option 1 (60% to 79%) is a narrower range that excludes the lower yellow-zone readings where early intervention is still possible.

Key point! The traffic-light system is standardized across most asthma action plan guidelines: green is 80% or above, yellow is 50% to 79%, and red is below 50% . The PEF meter converts a subjective sense of “not feeling well” into an objective number that guides stepwise self-management.References (research sources)

- [2]The relationship between changes in peak expiratory flow and asthma exacerbations in asthmatic children.Research articleChen X, Han P, Kong Y, Shen K. (2024) · DOI: 10.1186/s12887-024-04754-7

## 임상 시나리오

PEF Traffic-Light Zone TeachingAsthma action plan thresholds for early intervention
The yellow zone is defined as 50% to 79% of the patient’s personal best PEF. This range signals worsening airflow obstruction and should prompt reliever use, following the written plan, and contacting the provider.

The green zone is 80% to 100% of personal best, indicating good control. The red zone is below 50% and requires emergency care.

CautionPatients with poor symptom perception may not feel severe dyspnea despite a significant PEF drop. Teach them to act on the objective PEF number, not only on symptoms, to avoid delayed treatment.

## 핵심 개념

- **Peak expiratory flow (PEF)** — The maximum speed of expiration measured with a peak flow meter, used to monitor asthma control.
- **Personal best PEF** — The highest PEF value a patient can achieve when asthma is well controlled, used as the reference for zone cutoffs.
- **Traffic-light zone system** — A color-coded asthma action plan that classifies PEF readings as green, yellow, or red to guide self-management.
- **Yellow zone** — PEF 50–79% of personal best, indicating worsening airflow obstruction and need for reliever use plus provider contact.
- **Red zone** — PEF below 50% of personal best, indicating severe airflow limitation and need for emergency care.

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