Parse an HL7 v2 ADT (Admit/Discharge/Transfer) message to extract patient and event data

Steps

1. Receive the HL7 v2 message as a pipe-delimited string; the message starts with an MSH segment defining the field separator (|), component separator (^), and other encoding characters.
2. Parse the MSH segment: MSH-9 contains the message type (e.g., ADT^A01 for admission, ADT^A03 for discharge, ADT^A08 for update); MSH-10 is the message control ID used for acknowledgment.
3. Extract the PID segment for patient demographics: PID-3 (patient identifier list, including MRN), PID-5 (patient name as family^given^middle), PID-7 (date of birth YYYYMMDD), PID-8 (administrative sex).
4. Extract the PV1 segment for visit information: PV1-2 (patient class: I=inpatient, O=outpatient, E=emergency), PV1-3 (assigned patient location), PV1-19 (visit number), PV1-44/45 (admit and discharge dates).
5. Use an HL7 v2 parsing library (e.g., hl7apy for Python, HAPI for Java, node-hl7-client for Node.js) rather than manual string splitting to handle edge cases like escape sequences and optional fields.
6. Send an ACK response: construct an MSH segment with swapped sender/receiver and an MSA segment with MSA-1=AA (Application Accept) and MSA-2 matching the original MSH-10.