Fig. 3. (Top ) Data displaying the respiratory rate per minute on the y-axis in patients receiving total intravenous anesthesia (TIVA) with either remifentanil (black squares; n = 20) or alfentanil (grey circles; n = 20). Values are mean ± SD. (Bottom ) Data displaying pulse oximetry values on the y-axis in patients receiving TIVA with either remifentanil (black squares; n = 20) or alfentanil (grey circles; n = 20). Values are mean ± SD. On the x-axis for both graphs, preoperative baseline values are displayed, followed by the observed values after termination of TIVA in minutes. The asterisks indicate differences at the distinct time points between remifentanil and alfentanil, and the number signs indicate differences versus  the preoperatively assessed baselines (P < 0.05).