Figure 2

Time Course of Symptoms and Oximetry Variables at Exacerbation. Time course of symptom count, heart rate, oxygen saturation (SpO₂) and peak-expiratory flow (PEF) from seven days prior (-7) to exacerbation onset (day 0, vertical line) and seven days into exacerbation of COPD. Values of the physiological variables are the mean of 13 exacerbations in 13 patients, expressed as standard deviation multiples away from each patient's stable mean (see text for details). A 1SD change is an approximate alteration in heart rate of 5 min^-1, SpO₂ of 1% and PEF of 10l min^-1. Symptom count values are the mean from the 13 patients.