12 April QF534 SYD/BNE (4.45pm departure).
I was seated in Business and as we were still in the initial climb and the CSM Kathleen was just readying to serve the snack, the lady seated in the row behind was having trouble breathing and pinged the call button. The CSM called up one of the Y crew to serve in J and attended to the lady. She suggested she have oxygen therapy and the lady agreed, so Kathleen squeezed past the trolley and got the bottle and administered oxygen. The lady had her own Pulse Oximeter (she was down to 89%) and she was looking grey and said she had cold extremities. I finished my snack and through the break in the seat, was talking to her and her huband (initially seated in opposite aisle, but soon switched with a deadheading pilot). She looked a lot better by descent and came of the oxygen.
I assisted them deplaning and waited with them at Gate 23 in BNE, whilst Samantha (QF groundstaff) took over and we suggested she have a trip to hospital in an ambulance to get checked out. Samantha re-booked their onward flight (meant to be that night BNE/MKY) to the next day, called the paramedics and still boarded the BNE/PER flight as we waited for the ambos to turn up.
Turns out the lady had an operation the week before and post-op had been diagnosed with pericarditis. Made the difficulty in breathing understandable - somehow her doctor had medically cleared her for the flight (going to MKY to see daughter and impending birth of grandchild).
The ambos turned up and my help wasn't needed, but the ambo had parked in he bay next to the Uber pick-up zone, so I saw her again as she was loaded on.
So kudos to Kathleen, Samantha and the ambos.