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CareVue Interface

The HP CareVue/9000 system has a "foreign systems interface" (FSI) that supports a limited HL7 dialect. The task of the gateway is to map "standard" HL7 messages to CareVue's dialect of HL7 (cvHL7). The particular transformations performed are dependent on both, cvHL7 and the actual configuration of the CareVue system. Since the latter may vary from one installation to the other it is likely that the gateway program will not work "out of the box" but needs some adjustments. A lot is configurable at runtime by databases and the like, but some properties must be adjusted in the source code. This affects mainly the configuration of the user configurable patient demographics (ZDM) segment of cvHL7. However, since the configuration of the ZDM segment tends to be stabile over years, this limitation it is not too much of a problem.

The major differences between cvHL7 and "standard" HL7 are:

the ZDM segment
This is a segment that is placed at the end of ADT messages. It is required and very important, because CareVue does not use the HL7 standard data items for updating its patients demographic data. It rather maps the strings found in the ZDM segment to its preconfigured and user configurable patient data, like name, medical record number, etc.
message structure
is defined slightly different. For instance, the ORU message may not have a PV1 segment.
patient reference
patients are referenced by the CareVue's medRecNum. This number is expected in the PID.PatIdIntId field of any HL7 message. However, the CareVue system might be configured such that visit numbers (PV1.VisitNum) are used as patient ids instead, thus the gateway must exchange both numbers.

The cvHL7 interface of CareVue currently consists of three applications. The following table lists the application names along with the messages they can receive:

the ADT application receives ADT messages: A01, A02, A03, A08, A11, A12, A13, and A17
the clinical laboratory application receives ORU messages
the pharmacy orders application receives (!) pharmacy orders -- this is not implemented in this gateway and no documentation from HP is available for it whatsoever.

Note that the CareVue interface does only receive messages and sends an acknowledgment, with the exception of network management (NMD) messages, which it is capable to originate. However, this facility of (doubtful use) must be turned off for use with this gateway. NMD messages can be sent to each of the applications and are acknowledged by them.

The way that CareVue acknowledges request messages is quite disturbing. For instance, a positive acknowledgment (AA) for an admission (A01) does not guarantee the patient to be really admitted in the CareVue census. If the selected bed was already occupied no error is reported on HL7 level. On the other hand, one might receive an application error (AE) if an ORU message reports the same results twice for one date/time. The gateway must therefore test preconditions to messages in order to guarantee them to be reasonably effective where possible, and must reject those that can not be successful even though CareVue might acknowledge them positively.

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