[Relationship between peak expiratory flow and clinical exploration and arterial gas analysis in assessing the severity of an asthma attack].

Protocols for treating acute asthma presently rely on measurement of peak expiratory flow (PEF) to orient treatment and evaluate progress. Other clinical or functional parameters have also been considered for use in the assessment of severity of attack. In order to investigate the usefulness of these criteria we analyzed their relation to degree of air flow obstruction expressed by PEF in a sample of 48 asthmatics who came to the emergency room for treatment of disease exacerbation, excluding 6 who presented imminent risk of death at the time of admission. Among the clinical parameters analyzed, only presentation of cyanosis or diaphoresis was related to degree of obstruction. The pattern of accessory muscle use or vital signs such as heart, breathing rate or blood pressure were similar in patients with (PEF < 50%) or without (PEF > 50%) severe exacerbation. Among gasometric readings only PaO2 was significantly lower in patients with PEF < 50% and we were able to identify a cutoff point useful as a screen for respiratory insufficiency: when the initial PEF was above 50% of theoretical value, no patient had PaO2 < 60 mmHg. We conclude that: 1) clinical parameters do not always reflect severity of attack established by degree of air flow obstruction, and 2) PEF > 50% at the start of asthmatic exacerbation allows respiratory insufficiency to be ruled out, making performance of gasometric measurement unnecessary.