Phd Rtsa Observation Profile

The Rtsa Observation Profile is used when the PHD metric measurement contains the following attribute:

Attribute Value Additional Information
Simple-Sa-Observed-Value A sequence of scaled 8, 16, or 32-bit numbers Other attributes give scale factors, number of entries, period, and bit-size

This attribute contain a measurement that is a sequence of scaled periodic values. It is typically used when reporting waveforms. The values are scaled to reduced bandwidth. The bandwidth reduction can be significant in cases where the actual values are small fluctuations about a large average value. The scale factors, number of bits in each sample, the period, and the number of data elements in the sequence are given by a set of support attributes.

Support Attribute Value Description
Sample-Period.period integer Interval between samples in 1/8th millseconds
Sa-Specification.SampleType.significant-bits integer Number of significant bits in the sample value
Sa-Specification.SampleType.sample-size integer Number of bits in each sample; gives the X value in 'Scale-and-Range-SpecificationX'
Sa-Specification.array-size integer Number of samples in 'Simple-Sa-Observed-Value'
Scale-and-Range-SpecificationX.upper-absolute-value Mder FLOAT Highest unscaled value PHD will report
Scale-and-Range-SpecificationX.lower-absolute-value Mder FLOAT Lowest unscaled value PHD will report
Scale-and-Range-SpecificationX.upper-scaled-value X-bit integer The upper range scaled
Scale-and-Range-SpecificationX.lower-scaled-value X-bit integer The lower range scaled

If (significantBits < sampleSize)

  • the most significant (sampleSize - significantBits) bits of the sample i are zeroed and are treated as unsigned integers

If significantBits equals 255

  • the samples are treated as signed integers otherwise
  • the samples are treated as unsigned integers.

The upper and lower ranges represent the upper and lower actual sensor ranges that can be reported. The name 'absolute' in the attribute does not refer to the mathematical definition of an absolute value. The upper and lower values do NOT mean that a given set of samples has those values or that those values are ever reported by the sensor. However, a graphing application could use those values to define the upper and lower ranges of a graph and be assured that the waveform would never go above or below those boundaries. These upper and lower boundaries are placed in the Observation.referenceRange.low and Observation.referenceRange.high elements, respectively.

The structure definition for the Phd Rtsa Observation Profile is shown below:

phdProfile1..1Fixed Value
value1..
system
value1..
unit
system1..Fixed Value
code1..
factor1..
dimensions
data
system1..
code1..
value1..
unit
system1..Fixed Value
code1..
value1..
unit
system1..Fixed Value
code1..
system1..Fixed Value
code1..Fixed Value
display
value1..
unit
system1..Fixed Value
code1..
dataAbsentReason..0
system1..Fixed Value
code1..
system1..Fixed Value
code1..
dataAbsentReason..0
system1..Fixed Value
code1..Fixed Value
display
value1..
unit
system1..Fixed Value
code1..
value1..
unit
system1..Fixed Value
code1..
dataAbsentReason..0
system1..Fixed Value
code1..Fixed Value
display
value1..
dataAbsentReason..0
system1..Fixed Value
code1..Fixed Value
display
value1..
unit
system1..Fixed Value
code1..
value1..
unit
system1..Fixed Value
code1..
dataAbsentReason..0
system1..Fixed Value
code1..Fixed Value
display
value1..
dataAbsentReason..0

Mapping RTSA Waveforms To FHIR

Periodic data is mapped to the SampledData data type in FHIR. The SampledData.data element in this data type is also scaled. If y[i] is the ith entry of the actual unscaled data from the PHD sensor, y[i] is obtained from the SampledData type using the following relation:

y[i] = d[i] * s + b

where

  • s = SampledData.scaleFactor
  • b = SampledData.origin.value
  • d[i] = SampledData.data[i]

In the case of the RTSA metric, the ith entry of the actual unscaled data from the sensor is obtained from the Simple-Sa-Observed-Value attribute using the following relation:

y[i] = ((A – B)x[i])/(I – J) + A – (A-B)I/(I-J) where

  • A = Scale-and-Range-SpecificationX.upper-absolute-value
  • B = Scale-and-Range-SpecificationX.lower-absolute-value
  • I = Scale-and-Range-SpecificationX.upper-scaled-value
  • J = Scale-and-Range-SpecificationX.lower-scaled-value Where X = 8, 16, or 32 and x[i] = Simple-Sa-Observed-Value.data[i]

Since ((A – B)x[i])/(I – J) + A – (A-B)I/(I-J) = d[i] * s + b,

d[i] = x[i] if

  • s = SampledData.scaleFactor = (A – B)/(I – J) and
  • b = SampledData.origin.value = A –(A-B)I/(I-J) = (BI-AJ)/(I-J)

allowing one to map the Simple-Sa-Observed-Value.data[i] values directly to the SampledData.data[i] values unchanged. It is recommended that the uploader map the RTSA waveform to the Observation.valueSampledData element using the above scaling as it is assumed the PHD chose this scaling for a good reason. However, that does not restrict the uploader using other scalings. As an example, the uploader could decode the scaled values and report the unscaled original sensor values in the Observation.valueSampledData.data element and set the Observation.valueSampledData.scaleFactor to 1.0 and the Observation.valueSampledData.origin.value to 0. This approach is used in PCD-01.

Using the variables 'b' and 's' as defined above the mapping to the FHIR Observation resource is as follows:

Attribute FHIR coding
Simple-Sa-Observed-Value.data[i] Observation.valueSampledData.data[i]
Unit-Code.code Observation.valueSampledData.origin.code (as UCUM)
See calculation of 'b' above Observation.valueSampledData.origin.value = b*
See calculation of 's' above Observation.valueSampledData.scaleFactor = s*
Sample-Period.period/8 Observation.valueSampledData.period (milliseconds)
Sa-Specification.SampleType.sample-size Observation.valueSampledData.dimensions
Scale-and-Range-SpecificationX.upper-absolute-value Observation.referenceRange.high.value
Unit-Code.code Observation.referenceRange.high.code (as UCUM)
Scale-and-Range-SpecificationX.lower-absolute-value Observation.referenceRange.low.value
Unit-Code.code Observation.referenceRange.low.code (as UCUM)

*noting that other scaling options are allowed.

Conditional Create Identifier Generation

For a general description of the PHD Profile Identifier see the "PHD Profile Identifier" section in Phd Base Profile. The table below lists the items that make up the identifier.

Entry value Additional information
device "Phd Device.identifier.value" This value is the PHD IEEE EUI-64 system identifier
patient "Patient.identifier.value-Patient.identifier.system" or
provided logical id		 The dashes are part of the identifier.
When the service provider gives the PHG a pre-determined patient logical id the PHG creates no Patient resource and has no patient information. In that special case the provided logical id is used
type "Observation.code.coding.code" See Obtaining the Observation.code
value Observation.valueSampledData.period-Observation.valueSampledData.dimensions-Observation.valueSampledData.data[0] The data absent reason code is used if there is no value
units "Observation.valueSampledData.origin.code The units are the same for all data points
reported PHD timestamp "timestamp" See Generating the PHD Reported Time Stamp
supplemental types "Supplemental-Types.N-" A sequence of 32-bit MDC codes separated by a dash

The final identifier is made by concatenating the entries above as follows:

  • "device-patient-type-value-units-reported PHD timestamp-supplemental types".

Additional RTSA Measurement Information

All additional attributes that may be reported in a numerical metric measurement may also be present in an RTSA metric measurement. See the section 'Additional Note that one could report a waveform by reporting each value in the sequence as a sequence of single numeric metric measurements. Of course that would be costly in terms of bandwidth.

Consumers of the RTSA Profile

About the only work a consumer of this profile needs to do is to back-scale the valueSampledData.data[] values to the original values reported by the sensor. The following table summarizes where a reader can obtain the most pertinent information.

information Location in Observation.
Type of measurement code.coding.code
Time at the start of the waveform effectiveDateTime
Number of samples valueSampledData.dimension
Time between samples in milliseconds valueSampledData.period
Units of samples valueSampledData.origin.code
Upper range of values referenceRange.high.value
Lower range of values referenceRange.low.value
The actual n values valueSampledData.data[n] * valueSampledData.scaleFactor + valueSampledData.origin.value