Date: 201412
Local time of day: 0601-1200
Location: DFW.Airport, TX
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
ATC / advisory: Center ZFW
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Workload; Time Pressure; Distraction; Human-Machine Interface; Confusion; Communication Breakdown
Anomaly: ATC Issue All Types; Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance; Flight Deck / Cabin / Aircraft Event Illness / Injury
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Separated Traffic; Flight Crew FLC Overrode Automation
Contributing factors: Aircraft; Chart Or Publication; Human Factors; Procedure
Primary problem: Chart Or Publication

Narrative: Approximately ten minutes from top of descent into the DFW area; the FA's called to inform that a passenger was ill. Due to our proximity to destination; and considering that a Dr was on board; and considering that a Medlink conversation takes my attention away from PM duties; I elected to continue to destination. But; even with the reduced demands of not carrying on a conversation with Medlink; the ongoing medical event still proved distracting; and did so at the wrong time. During the last 30 mins of flight (all of which were affected by the ill passenger issue); ATC changed the arrival once; issued two lengthy off course vectors; changed one waypoint crossing from a 'between FLxxx and FLxxx' to a 'cross at' restriction and issued three (or maybe more) speed changes. The PF (FO) became task saturated with reprogramming the FMGC MCDU to accommodate the latest request for an airspeed change; and failed to initiate a descent at the proper time. I; the Capt and PM; noticed the error in time to start down before the fix (SEEVR) but not in time to cross the fix at the required altitude. The result was an altitude error at SEEVR of approximately 700 ft. ATC made no mention of the missed restriction and we received no TCAS alerts. The remainder of the flight was normal.ATC must drastically reduce or (preferably) eliminate the multiple speed changes after top of descent on these 'continuous' descent arrivals into the DFW terminal area. We routinely receive clearances that significantly modify the databased arrivals; mainly dealing with speed changes. If the speeds were modified just once; this would be a non-issue; but the requested/required speed changes are becoming almost a constant - happening numerous times during the descent phase into the DFW terminal area. ATC specialists must not have any idea of the level of disruption the constantly changing speeds impose on the flight crew during arrival into DFW.  In my opinion they truly need increased awareness of the destabilizing affect these speed changes have on a safe flight. Events such as abnormals/emergencies and passenger issues that increase pilot workload can't be avoided; but events created by ATC can and should be eliminated. DFW is attempting to 'load ten pounds into a five pound bag' and the results are becoming increasingly unsafe.




Synopsis: An Air Carrier Captain; dealing with the added demands of an ill passenger; expressed his concerns about the disruptive nature of multiple ATC modifications to their complex RNAV arrival to DFW; the end result of which was 700 FT deviation from an altered crossing restriction which; ultimately; went uncommented upon by ATC.