Investigations

• Peak expiratory flow rate ^c

Admit patients with a PEFR ^c

• < 100 l/min before therapy
• < 300 l/min after therapy

Why?

• Neither clinicians nor patients accurately judge peak flows ^c
• PEFR correlates reasonably well with FEV1 in patients with acute asthma ^c
• Both PEFR and FEV1 can predict which patients will require admission or have continuing symptoms. ^c

Peak expiratory flow rate helps predict patients that require admission

Patient	Prognostic Factor	Outcome	CER	RR (95% CI)	NNF+ (95% CI)
acute asthma c	pre-treatment PEFR < 100 l/min not independent	admitted to hospital or failed discharge at 48 hours	41%	1.86 (1.32 to 2.61)	3 (2 to 8)
	post-treatment PEFR < 300 l/min not independent		14%	5.43 (2.55 to 11.56)	2 (1 to 5)