Date: 201411
Local time of day: 1201-1800
Location: MDW.Airport, IL
Flight conditions: VMC
Light: Daylight
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Initial Approach
Airspace: Class B MDW
ATC / advisory: TRACON C90
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Human factors: Time Pressure; Human-Machine Interface
Second reporter function: Pilot Not Flying; Captain
Anomaly: Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Contributing factors: Human Factors; Procedure
Primary problem: Procedure

Narrative: ATIS reported RNAV 22L Y with STERE transition. The initial check-in with Approach confirms that approach properly briefed and checked as correct in system. Subsequently told to expect the RNAV 22L X while at the end of the STAR. Again; briefed and correctly inputted into system. Then immediately directed back to the RNAV 22L Y. Again; checked as correct in the FMC (altitudes; waypoints with the discontinuity as required). Descended to 4000 FT just prior to MIING; then just before MIING; reassigned the RNAV 22L X approach. As pilot flying (PF); I once again selected the RNAV X Approach; but as the safety alert for the ENDEE Arrival points out; doing so at this point (MIING) brings back previous points that have to be deleted. The Captain; pilot monitoring (PM; handled this successfully; but now at 4000 FT; when we put the new approach into the FMC; we were dropped from VNAV PATH since the FMC wanted a 6000 FT cruise but we were already down at 4000 FT per ATC. Now at MIING; and out of VNAV PATH; and with things getting busy with the approach turn underway; and configuration changes underway; I (PF) was behind the aircraft. I went from being ahead of the aircraft; in LNAV/VNAV Path; with '0' at the IAF; and everything properly briefed and understood; to playing catch-up at the busiest time. PM correctly recommended flaps to start us slowing down; and believing that a descent was warranted (we were in ALT Hold); selected V/S to start us down. However; after getting down to approximately 3700 FT; we realized there was a further restriction of 4000 FT at the next point (FENCK). I switched off autopilot and autothrottles; returned to 4000 FT and flew the remainder of the approach without automation or further difficulty. We had briefed said restriction at FENCK as well as the others (a couple of times); but it dropped from our scans when we became saturated.I believe we gave due attention to proper briefing and communication. However; my scan broke down as the changes came fast and furious at the IAF and even inside of that. Those ATC-directed changes at that time and pace were not helpful but do not relieve the Crew of the requirement to remain ahead of the aircraft. Or just tell ATC 'no' and fly what was briefed at that point; or ask for a visual. But even ATC said 'sorry for yet another change in close' so I think they know it can get to be a bit much when that happens; so maybe some guidelines on deadlines in time; altitude or distance from the field for changing approaches...


Second narrative: [Report narrative contained no additional information.]


Synopsis: B737 First Officer experienced three changes to the expected RNAV approach during the arrival. The last change at MIING; caused the entire arrival to be restarted and required many deletions before WADLL became the 'to' waypoint. An altitude deviation occurred between MIING and FENCK; as the flying pilot became task saturated; and was quickly corrected.