A pulse oximetry monitor configured to perform a spot-check measurement of a physiological parameter, the monitor comprising: a driver circuit that drives one or more emitters (7109A, 7209A, 7209B) of an optical sensor (2331; 6904A, 6904B; 7004; 7304A) at multiple wavelengths of light to cause the one or more emitters (7109A, 7209A, 7209B) to transmit the multiple wavelengths of light through body tissue (6906A, 6906B; 7106A; 7206A, 7206B; 7306A, 7306B) of a patient; a hardware processor in communication with the sensor (2331; 6904A, 6904B; 7004; 7304A), the hardware processor configured to: determine a number of remaining spot-check credits; based at least in part on a determination that the number of spot-check credits satisfies a threshold, initiate a spot-check measurement of a physiological parameter by obtaining a signal from the optical sensor (2331; 6904A, 6904B; 7004; 7304A); compute the spot-check measurement based on the signal upon detecting that the sensor (2331; 6904A, 6904B; 7004; 7304A) has been disconnected from the patient; assess a validity of the spot-check measurement; based at least in part on a determination that the spot-check measurement is valid, update the number of remaining spot-check credits; and output the spot-check measurement to a display of the pulse oximetry monitor. a driver circuit that drives one or more emitters (7109A, 7209A, 7209B) of an optical sensor (2331; 6904A, 6904B; 7004; 7304A) at multiple wavelengths of light to cause the one or more emitters (7109A, 7209A, 7209B) to transmit the multiple wavelengths of light through body tissue (6906A, 6906B; 7106A; 7206A, 7206B; 7306A, 7306B) of a patient; a hardware processor in communication with the sensor (2331; 6904A, 6904B; 7004; 7304A), the hardware processor configured to: determine a number of remaining spot-check credits; based at least in part on a determination that the number of spot-check credits satisfies a threshold, initiate a spot-check measurement of a physiological parameter by obtaining a signal from the optical sensor (2331; 6904A, 6904B; 7004; 7304A); compute the spot-check measurement based on the signal upon detecting that the sensor (2331; 6904A, 6904B; 7004; 7304A) has been disconnected from the patient; assess a validity of the spot-check measurement; based at least in part on a determination that the spot-check measurement is valid, update the number of remaining spot-check credits; and output the spot-check measurement to a display of the pulse oximetry monitor. determine a number of remaining spot-check credits; based at least in part on a determination that the number of spot-check credits satisfies a threshold, initiate a spot-check measurement of a physiological parameter by obtaining a signal from the optical sensor (2331; 6904A, 6904B; 7004; 7304A); compute the spot-check measurement based on the signal upon detecting that the sensor (2331; 6904A, 6904B; 7004; 7304A) has been disconnected from the patient; assess a validity of the spot-check measurement; based at least in part on a determination that the spot-check measurement is valid, update the number of remaining spot-check credits; and output the spot-check measurement to a display of the pulse oximetry monitor.