Plethysmograph variability processor
A plethysmograph variability processor inputs a plethysmograph waveform having pulses corresponding to pulsatile blood flow within a tissue site. The processor derives plethysmograph values based upon selected plethysmograph features, determines variability values, and calculates a plethysmograph variability parameter. The variability values indicate the variability of the plethysmograph features. The plethysmograph variability parameter is representative of the variability values and provides a useful indication of various physiological conditions and the efficacy of treatment for those conditions.
1. A computerized plethysmograph variability method using a signal processor comprising:
receiving a data signal from a physiological sensor coupled to a patient;
generating a plethysmograph waveform based at least in part on the data signal, wherein the plethysmograph waveform comprises a plurality of pulses corresponding to pulsatile blood flow within tissue of the patient;
accumulating, in a first buffer, a plurality of perfusion values corresponding to the plurality of pulses, the plurality of perfusion values derived based on the plurality of pulses;
determining if a sufficient amount of physiologically acceptable data is in the first buffer based at least on a length of a respiration cycle of the patient, wherein the signal processor is configured to perform specific operations when there is sufficient amount of data and when there is insufficient amount of data in the first buffer over time;
in response to determining that sufficient amount of data is in the first buffer for a specific period of time:
determining a plurality of variability values each indicative of variability of a series of the plurality of perfusion values;
calculating a plethysmograph variability index representative of the plurality of variability values; and
displaying the calculated plethysmograph variability index; and
in response to determining that insufficient amount of data is in the first buffer for the specific period of time:
displaying a previously calculated plethysmograph variability index stored in the signal processor.
2. The computerized plethysmograph variability method according to claim 1 , wherein
determining the plurality of variability values further comprises:
sorting the plurality of perfusion values within the first buffer from a largest perfusion value to a smallest perfusion value; and
trimming at least one perfusion value from a set of largest perfusion values and at least one perfusion value from a set of smallest perfusion values from the first buffer.
3. The computerized plethysmograph variability method according to claim 2 , wherein determining the plurality of variability values further comprises calculating a plurality of plethysmograph variability indexes (PVIs) from a percentage difference between a maximum perfusion value and a minimum perfusion value for the first buffer.
4. The computerized plethysmograph variability method according to claim 3 , wherein calculating qathe plethysmograph variability index comprises calculating a median value of the PVIs.
5. The computerized plethysmograph variability method according to claim 4 , wherein determining if sufficient amount of physiologically acceptable data is in the first buffer comprises:
identifying the plurality of pulses, wherein the plurality of pulses comprise physiologically acceptable pulses identified from a group comprising the physiologically acceptable pulses and physiologically unacceptable pulses; and
determining a minimum amount of time of acceptable data in the first buffer.
6. The computerized plethysmograph variability method according to claim 5 , further comprising:
verifying the physiologically acceptable pulses using a red channel,
wherein inputting the plethysmograph waveform comprises using an IR channel for the plethysmograph waveform.