# Performing Time Domain Heart Rate Variability in Ponemah v5.2 or less

Ponemah versions 5.00 - 5.20 do not have a function to directly derive Time Domain Heart Rate Variability (HRV), only Frequency Domain. Time Domain parameters must be manually calculated using Excel, as described below.

**Calculating Time Domain HRV in Excel**

- Calculate the NN interval
- Filter the RR interval for ectopic beats (NN interval
- This can be using various methods, you can calculate 1 overall average of all the RR interval or calculate a running average
- Delete cycles that are a given standard deviation or percentage from the average
- Average the remaining cycles (the ones that were not delete from the previous step), this is the NN interval
- Calculate the SDNN
- Take the square root of the of the NN interval (calculated in step 1)
- Calculate the RMSSD
- Copy the NN interval column to a blank column
- Copy the NN interval to a column next to the column created in step 3a but with a shift down one row
- In the next column, calculate the difference to the columns created in 3a and 3b.
- In the next column, square the value calculated in 3c
- In the next column, calculate the total sum of all the values calculated from step 3d
- In the next column, count the number of elements in the NN interval (can use values from step 3a)
- In the next column, take the sum of difference squared (step 3e)/ count of NN intervals (step 3f)
- Take the square routs of the value created in step 3g and this is the RMSSD value
- pNNx
- Count the number of value in the NN interval column that is greater than x. Humans are typically done at 50 msec, pNN

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