Relationships among gas exchange, spirometry and symptoms in asthma.
OBJECTIVE
The severity of asthma is usually evaluated by clinical examination and spirometry. In a small study of asthmatics considerable ventilation/perfusion (VA/Q) inequality was found, however, despite essentially normal flow rates. These findings prompted the current study.


METHODS
We prospectively examined symptoms, spirometry and VA/Q inequality in 26 patients with chronic, symptomatic asthma once a week for 9 consecutive weeks. VA/Q measurements were made using a less invasive approach of the multiple inert gas elimination technique and symptoms were scored.


RESULTS
Correlation coefficients between indices for VA/Q inequality (log SDQ), spirometry (FEV1.0/VC, MEF25) and symptom scores were only in the range 0.24-0.29.


CONCLUSIONS
We conclude that even at the individual level, symptoms, spirometry and VA/Q inequality are so poorly correlated that one cannot evaluate any of these aspects of asthma without measuring each. The data support the notion that spirometric and gas exchange abnormalities in asthma are caused by different pathophysiologic events.
Lagerstrand
L
L
Department of Clinical Physiology, Huddinge Hospital, Sweden.
Bylin
G
G
Hedenstierna
G
G
Wagner
P D
PD
D001249:Asthma / Q000175:diagnosis / Q000503:physiopathology*; D005541:Forced Expiratory Volume; D006801:Humans; D008168:Lung / Q000502:physiology*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D013147:Spirometry; D014692:Ventilation-Perfusion Ratio; D014797:Vital Capacity