Narrative:

Upon descent the aircraft pressurization system failed; leading to a loss of cabin pressure. Until point of malfunction aircraft operated with no observed anomalies or deficiencies. Flight was smooth and routine until shortly after reaching top of descent and leaving FL380. Descending from FL380 to FL300 auto fail light illuminated on pressurization panel. Estimate the illumination of the auto fail light occurred around FL370. First officer acting as pilot monitoring located appropriate checklist in QRH and we commenced working through the items contained therein. Completed QRH 2.4. The auto fail light extinguished and we continued normal operation with panel now set to altn mode. Shortly thereafter there was erratic behavior in the differential pressure and cabin altitude gauge. The changes were noticeable in ears as the pressure/cabin altitude changed quickly in either direction. Scanned overhead panel and noticed the altn light no longer illuminated. Verbalized to first officer that we should put our masks on. At this point estimate the aircraft was between FL360 and FL300 which was the initial floor of our assigned descent from ATC. We both donned masks and within moments the cabin altitude light illuminated with corresponding warning horn and a very noticeable drop in pressure. Called for and first officer immediately secured and began with the cabin altitude warning qrc. Pass oxy on light illuminated as well indicating cabin oxygen masks had deployed. Accomplished cabin altitude warning qrc. Cabin altitude spiked but can't recall to what altitude. At one point; cabin descended rapidly and diff pressure climbed to redline on gauge.outflow valve seemed to be uncontrollable; which made the onboard pressurization issue uncontrollable. Coordinated with ATC for lower altitude and maintained an expedited descent that was essentially unbroken until landing. At completion of qrc we were directed to accomplish QRH 2.1. Used 2.1 through entire descent and uneventful landing. During descent while coordinating with cabin crew; flight attendants informed flight deck crew that one passenger briefly lost consciousness but was awake again and being attended to by cabin crew. Notified ATC of need for EMS to meet aircraft at gate upon arrival. ATC facilitated request and local EMS met aircraft and evaluated passenger. Upon arrival coordinated with dispatch; both local company maintenance and maintenance control and chief pilot; to ensure aircraft abnormalities were properly documented in logbook; crew was taken care of and all other pertinent issues had been addressed. I think this was an anomaly and part of flying aircraft as a business. Things break. Just glad it turned out the way it did. As far as self evaluation goes; I did forget a few items that bug me. One; I should've let the first officer handle communication with the cabin as I ended up unnecessarily task loading myself. Also; I forgot to send an acars to dispatch or radio them letting them know about the situation. We were pretty busy but no excuse. I'm pretty sure ATC notified company if only just the local ops folks. The checklist was handled correctly but as altn system failed and we were directed to go to manual. The cabin pressure spiked and dropped several times and then failed. That was certainly an enormous distraction and it took us a minute to get masks on and fully reengaged with the checklist. Feel like I could've done a better job leading in those moments. Will say that I was very happily surprised by how much our training kicked in; when the event got bad. Kudos to the training folks!

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Original NASA ASRS Text

Title: B737-800 flight crew reported a normal landing following the loss of pressurization at top of descent.

Narrative: Upon descent the aircraft pressurization system failed; leading to a loss of cabin pressure. Until point of malfunction aircraft operated with no observed anomalies or deficiencies. Flight was smooth and routine until shortly after reaching Top of Descent and leaving FL380. Descending from FL380 to FL300 Auto Fail light illuminated on pressurization panel. Estimate the illumination of the Auto Fail light occurred around FL370. First Officer acting as Pilot Monitoring located appropriate checklist in QRH and we commenced working through the items contained therein. Completed QRH 2.4. The Auto Fail light extinguished and we continued normal operation with panel now set to ALTN mode. Shortly thereafter there was erratic behavior in the differential pressure and cabin altitude gauge. The changes were noticeable in ears as the pressure/cabin altitude changed quickly in either direction. Scanned overhead panel and noticed the ALTN light no longer illuminated. Verbalized to First Officer that we should put our masks on. At this point estimate the aircraft was between FL360 and FL300 which was the initial floor of our assigned descent from ATC. We both donned masks and within moments the Cabin Altitude light illuminated with corresponding warning horn and a very noticeable drop in pressure. Called for and First Officer immediately secured and began with the Cabin Altitude Warning QRC. PASS OXY ON light illuminated as well indicating Cabin Oxygen masks had deployed. Accomplished Cabin Altitude Warning QRC. Cabin altitude spiked but can't recall to what altitude. At one point; cabin descended rapidly and diff pressure climbed to redline on gauge.Outflow valve seemed to be uncontrollable; which made the onboard pressurization issue uncontrollable. Coordinated with ATC for lower altitude and maintained an expedited descent that was essentially unbroken until landing. At completion of QRC we were directed to accomplish QRH 2.1. Used 2.1 through entire descent and uneventful landing. During descent while coordinating with cabin crew; flight attendants informed flight deck crew that one passenger briefly lost consciousness but was awake again and being attended to by cabin crew. Notified ATC of need for EMS to meet aircraft at gate upon arrival. ATC facilitated request and local EMS met aircraft and evaluated passenger. Upon arrival coordinated with Dispatch; both local Company Maintenance and Maintenance Control and Chief Pilot; to ensure aircraft abnormalities were properly documented in logbook; crew was taken care of and all other pertinent issues had been addressed. I think this was an anomaly and part of flying aircraft as a business. Things break. Just glad it turned out the way it did. As far as self evaluation goes; I did forget a few items that bug me. One; I should've let the First Officer handle communication with the cabin as I ended up unnecessarily task loading myself. Also; I forgot to send an ACARs to Dispatch or radio them letting them know about the situation. We were pretty busy but no excuse. I'm pretty sure ATC notified Company if only just the local ops folks. The checklist was handled correctly but as ALTN system failed and we were directed to go to manual. The cabin pressure spiked and dropped several times and then failed. That was certainly an enormous distraction and it took us a minute to get masks on and fully reengaged with the checklist. Feel like I could've done a better job leading in those moments. Will say that I was very happily surprised by how much our training kicked in; when the event got bad. Kudos to the training folks!

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.