Background: A life-threatening asthma attack is still of major concern. One of the main goals in treating patients with asthma is identification of the patients at risk of having these attacks. It has been shown that patients who have a near-fatal asthma attack have a blunted perception of dyspnea (POD). The purpose of this study is to measure the POD in patients with asthma, and to relate POD to life-threatening attacks within a 24-month follow-up period.
Methods: The POD was scored using the Borg scale during breathing against a progressive load at 1-min intervals, in order to achieve mouth pressure up to 30 cm H(2)O, in 113 consecutive asthmatic patients with stable asthma attending an outpatient clinic. All patients were invited to regular follow-up every 3 months for up to 24 months, and all hospitalizations and near-fatal and fatal asthma attacks were recorded. The prebronchodilator morning peak expiratory flow rate (PEFR), daily regular treatment, and beta(2)-agonist consumption were recorded in a diary card for the first 4 weeks.
Results: Seventeen patients (15%) had high POD compared to the normal subjects, 67 patients (59%) had POD within the normal range, and 29 patients (26%) had lower-than-normal POD. In the patients with low POD, there was a tendency for higher age, higher female/male ratio, and a longer duration of disease. The rate of severe asthma was higher in the low-POD group than in the normal-POD group, but did not differ from the rate in the high-POD group. The mean daily beta(2)-agonist consumption in the patients with low POD was significantly lower (p < 0.01) than in the patients with high POD, although the mean PEFR was lower in the low-POD group. During the 2 years of follow-up, the patients in the low-POD group had statistically significantly more emergency department (ED) visits, hospitalizations, near-fatal asthma attacks, and deaths compared to the normal-POD and high-POD groups.
Conclusions: Approximately 26% of the referral subjects with asthma had low POD when compared to healthy matched subjects. Patients with low POD had statistically significantly more ED visits, hospitalizations, near-fatal asthma attacks, and deaths during the follow-up period. Reduced POD may predispose patients to a life-threatening attack.