A method of taking pulse oximetry measurements on a specific patient, the method comprising: using a calibration pulse-oximeter, estimating one or more first, reference SpO2 values from a first, reference PPG signal measured by the calibration pulse-oximeter on a first, reference area of the human body of said specific patient; wherein said calibration pulse-oximeter comprises one or more light emitters (2, 2', 3, 3') adapted to emit light directed into a human tissue, and at least one light detector (13, 13') for detecting light reflected from said tissue; wherein the first, reference area of the human body of said specific patient is a fingertip or an ear lobe of said specific patient, thus having greater blood perfusion than a second, target area of the human body of said specific patient located around the wrist of said specific patient; the method being characterized by: using the same calibration pulse-oximeter, estimating one or more second SpO2 values from a second PPG signal on said second, target area of the human body of said specific patient around the wrist of said specific patient; calculating an offset parameter on the basis of the one or more first, reference SpO2 values and the one or more second SpO2 values; and using a bracelet-type measurement pulse oximetry device (10, 10', 10A) also comprising one or more light emitters (2, 2', 3, 3') adapted to emit light directed into a human tissue, and at least one light detector (13, 13') for detecting light reflected from said tissue, measuring a plurality of third SpO2 values from the second PPG signal on said second, target area of the human body of said specific patient, wherein said third SpO2 values are offset using said offset parameter. using a calibration pulse-oximeter, estimating one or more first, reference SpO2 values from a first, reference PPG signal measured by the calibration pulse-oximeter on a first, reference area of the human body of said specific patient; wherein said calibration pulse-oximeter comprises one or more light emitters (2, 2', 3, 3') adapted to emit light directed into a human tissue, and at least one light detector (13, 13') for detecting light reflected from said tissue; wherein the first, reference area of the human body of said specific patient is a fingertip or an ear lobe of said specific patient, thus having greater blood perfusion than a second, target area of the human body of said specific patient located around the wrist of said specific patient; the method being characterized by: using the same calibration pulse-oximeter, estimating one or more second SpO2 values from a second PPG signal on said second, target area of the human body of said specific patient around the wrist of said specific patient; calculating an offset parameter on the basis of the one or more first, reference SpO2 values and the one or more second SpO2 values; and using a bracelet-type measurement pulse oximetry device (10, 10', 10A) also comprising one or more light emitters (2, 2', 3, 3') adapted to emit light directed into a human tissue, and at least one light detector (13, 13') for detecting light reflected from said tissue, measuring a plurality of third SpO2 values from the second PPG signal on said second, target area of the human body of said specific patient, wherein said third SpO2 values are offset using said offset parameter. using the same calibration pulse-oximeter, estimating one or more second SpO2 values from a second PPG signal on said second, target area of the human body of said specific patient around the wrist of said specific patient; calculating an offset parameter on the basis of the one or more first, reference SpO2 values and the one or more second SpO2 values; and using a bracelet-type measurement pulse oximetry device (10, 10', 10A) also comprising one or more light emitters (2, 2', 3, 3') adapted to emit light directed into a human tissue, and at least one light detector (13, 13') for detecting light reflected from said tissue, measuring a plurality of third SpO2 values from the second PPG signal on said second, target area of the human body of said specific patient, wherein said third SpO2 values are offset using said offset parameter.