Tremor side effects of salbutamol, quantified by a laser pointer technique

Abstract

Objective: To study tremor side effects of salbutamol an easily applicable, quick and low-priced method is needed. A new method using a commercially available, pen-shaped laser pointer was developed. Aim of the study was to determine sensitivity, reproducibility, reference values and the agreement with a questionnaire.

Methods: Tremor was measured using a laser pointer technique. To determine sensitivity we assessed tremor in 44 patients with obstructive lung disease after administration of cumulative doses of salbutamol. Subjects were asked to aim at the centre of a target, subdivided in concentric circles, from 5 m distance. The circle in which the participant succeeded to aim was recorded in millimetres radius. In another series of measurements, reproducibility and reference values of the tremor was assessed in 65 healthy subjects in three sessions, at 9 a.m., 4 p.m. and 9 a.m., respectively, 1 week later. Postural tremor was measured with the arm horizontally outstretched rest tremor with the arm supported by an armrest and finally tremor was measured after holding a 2-kg weight until exhaustion. Inter-observer variability was measured in a series of 10 healthy subjects. Tremor was measured simultaneously by two independent observers.

Results: Salbutamol significantly increased tremor severity in patients in a dose-dependent way. Within healthy adults no age-dependency could be found (b = 0.262 mm/year; P = 0.72). There was no agreement between the questionnaire and tremor severity (r = 0.093; P = 0.53). Postural tremor showed no significant difference between the first and third session (P = 0.07). Support of the arm decreased tremor severity, exhaustion increased tremor severity significantly. A good agreement was found between two independent observers (interclass correlation coefficient 0.72).

Discussion: Quantifying tremor by using an inexpensive laser pointer is, with the exception of children (<12 years) a sensitive and reproducible method.