ImportancePrehospital needle decompression (PHND) is a rare but potentially life-saving procedure. Prior studies on chest decompression in trauma patients have been small, limited to single institutions or emergency medical services (EMS) agencies, and lacked appropriate comparator groups, making the effectiveness of this intervention uncertain.ObjectiveTo determine the association of PHND with early mortality in patients requiring emergent chest decompression.Design, Setting, and ParticipantsThis was a retrospective cohort study conducted from January 1, 2000, to March 18, 2020, using the Pennsylvania Trauma Outcomes Study database. Patients older than 15 years who were transported from the scene of injury were included in the analysis. Data were analyzed between April 28, 2021, and September 18, 2021.ExposuresPatients without PHND but undergoing tube thoracostomy within 15 minutes of arrival at the trauma center were the comparison group that may have benefited from PHND.Main Outcomes and MeasuresMixed-effect logistic regression was used to determine the variability in PHND between patient and EMS agency factors, as well as the association between risk-adjusted 24-hour mortality and PHND, accounting for clustering by center and year. Propensity score matching, instrumental variable analysis using EMS agency-level PHND proportion, and several sensitivity analyses were performed to address potential bias.ResultsA total of 8469 patients were included in this study; 1337 patients (11%) had PHND (median [IQR] age, 37 [25-52] years; 1096 male patients [82.0%]), and 7132 patients (84.2%) had emergent tube thoracostomy (median [IQR] age, 32 [23-48] years; 6083 male patients [85.3%]). PHND rates were stable over the study period between 0.2% and 0.5%. Patient factors accounted for 43% of the variation in PHND rates, whereas EMS agency accounted for 57% of the variation. PHND was associated with a 25% decrease in odds of 24-hour mortality (odds ratio [OR], 0.75; 95% CI, 0.61-0.94; P = .01). Similar results were found in patients who survived their ED stay (OR, 0.68; 95% CI, 0.52-0.89; P < .01), excluding severe traumatic brain injury (OR, 0.65; 95% CI, 0.45-0.95; P = .03), and restricted to patients with severe chest injury (OR, 0.72; 95% CI, 0.55-0.93; P = .01). PHND was also associated with lower odds of 24-hour mortality after propensity matching (OR, 0.79; 95% CI, 0.62-0.98; P = .04) when restricting matches to the same EMS agency (OR, 0.74; 95% CI, 0.56-0.99; P = .04) and in instrumental variable probit regression (coefficient, −0.60; 95% CI, –1.04 to –0.16; P < .01).Conclusions and RelevanceIn this cohort study, PHND was associated with lower 24-hour mortality compared with emergent trauma center chest tube placement in trauma patients. Although performed rarely, PHND can be a life-saving intervention and should be reinforced in EMS education for appropriately selected trauma patients.