Patients of the ICU's often require bronchodialtatory treatment due to bronchospazm caused by conditions like : ARDS, COPD or asthma. The β2 adreneregic drugs are one of the most commonly used for this purpose. However it is known that they may cause tachycardia and may have substantial proarrhythmic effect. The investigators' aim is to estimate the influence of nebulized bronchodilatatory drugs on selected electrophysiological parameters, whose changes are generally recognized as potentially increasing the risk of ventricular and supraventricular arrhythmias. Two drugs will be compared - salbutamol given in two doses and ipratropium bromide