The Patient Who Looks Fine at PEF 45%
October 22, 2026
A clinical brief for referring providers — week 1 of a 4-part series on asthma exacerbations.
A question before the clinical note: In the acute setting, which more reliably tells you how sick your asthma patient is — how they look and sound, or their peak flow?
a) How they look and sound b) Objective lung function (PEF or FEV1) c) Both are equally reliable
Dr. {{first_name}},
A young adult with a prior ICU admission for asthma is speaking in full sentences and does not look distressed. Her peak flow is 45% of her personal best.
GINA 2026 is direct: in the acute setting, objective lung function — PEF or FEV1 — is a more reliable indicator of severity than symptoms.
A minority of patients are poor perceivers of airflow limitation. They deteriorate significantly without a proportional change in symptoms, and it is more common in patients with a history of near-fatal asthma. It concentrates in exactly the patients you can least afford to misjudge.
Severity maps to venue
Mild, above 75%: Outpatient
Moderate, 50–75%: Outpatient
Severe, 33–50%: Acute care
Life-threatening, below 33%: Immediate transfer
Transfer now, without a trial of therapy: drowsiness, confusion, or a silent chest.
Two practical notes
Start the rescue inhaler and oxygen while you measure — do not hold treatment for a complete workup.
Consider pertussis in an atypical exacerbation where cough predominates.
Refer your toughest asthma patient
Pulmonary evaluation with the Chest & Sleep Team. Tell us what you are seeing and we will take it from there.
Call (847) 860-7250.
Severity bands adapted from Zaidan et al., JAMA, 2020.
The answer
Objective lung function. PEF or FEV1 outperforms symptoms for staging (Reddel et al., GINA 2026).