B737-800
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 515; Flight Crew Type 5000
Other / Unknown; Communication Breakdown
Flight Deck / Cabin / Aircraft Event Illness / Injury
Air Traffic Control Provided Assistance; Flight Crew Took Evasive Action
Procedure
I was the Captain of the flight; operating as PF (pilot flying); when the FA (Flight Attendant) contacted the flight deck to inform us we had a sick child onboard. The child was complaining of headaches and vomiting and a physician was onboard and attending to the child. After transferring PF duties to the FO (First Officer); I initiated a phone patch with the aircraft; the Operations Center and medlink. After consultation with medlink; it was determined to be a sinus issue and we would be continuing to PHX. While monitoring the end of the medlink phone patch; I instructed the FO; who was PF and working the ATC radios; to seek a lower altitude; in order to lower the cabin altitude; and possibly relieve some of the child's sinus pressure.Our position was just prior to the arrival into PHX. We were at FL390 and had plenty of fuel for an early descent; so he asked for FL280; which was the first crossing altitude on the arrival; roughly 100 miles away. ATC asked for the reason for the early descent; and the FO replied a 'passenger issue.' I did not hear all of the exchange with ATC. I did tell the FO that we were not declaring medical emergency. ATC never asked for clarification; and we never declared an emergency. The medical situation was under control; and no priority handling was needed; requested or received. The remainder of the flight was uneventful; however; upon arrival at the gate in PHX; the Chief Pilot in the Operations Center called and let us know that the FAA had called the Operations Center and were concerned that our flight was under duress. Apparently; the use of 'passenger issue' was confusing to them.
B737 Captain reported a misunderstanding between the flight crew and ATC regarding a passenger illness resulted in an aircraft security inquiry.