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Background-The incidence and significance of gasping after cardiac arrest in humans are controversial. Methods and Results-Two approaches were used. The first was a retrospective analysis of consecutive confirmed out-of-hospital cardiac arrests from the Phoenix Fire Department Regional Dispatch Center text files to determine the presence of gasping soon after collapse. The second was a retrospective analysis of 1218 patients with out-of-hospital cardiac arrests in Arizona documented by emergency medical system (EMS) first-care reports to determine the incidence of gasping after arrest in relation to the various EMS arrival times. The primary outcome measure was survival to hospital discharge.

Importance Current prehospital traumatic brain injury guidelines utilize a systolic blood pressure threshold of <90mmHg for treating hypotension (age≥10) based on studies showing higher mortality when blood pressure drops below this level. However, the guidelines also acknowledge the weakness of the supporting evidence. Objective In a statewide, multisystem study of traumatic brain injury, to evaluate whether any statistically supportable systolic pressure-versus-mortality threshold emerges from the data, a priori, without assuming that a cut-point exists. Design Observational evaluation of a large prehospital database established as a part of the Excellence in Prehospital Injury Care (EPIC) Traumatic Brain Injury Study (NIH/NINDS-1R01NS071049). The generalized additive model and logistic regression were utilized to determine the relationship between systolic pressure and probability of death, adjusting for significant/important confounders. Setting The pre-implementation cohort (1/1/2007–3/31/2014) of the EPIC Study. Participants Patients (age≥10) with moderate/severe traumatic brain injury (Barell Matrix-Type 1 and/or International Classification of Disease-9 head region severity ≥3 and/or Abbreviated Injury Scale head-region severity ≥3) and lowest prehospital systolic pressure between 40 and 119mmHg were included. Main Outcome Measure The main outcome measure was in-hospital mortality. Results Among the 3,844 included cases, the model revealed a monotonically-decreasing relationship between systolic pressure and adjusted probability of death across the entire range (40–119mmHg). Each ten-point increase of systolic pressure was associated with a decrease in the adjusted odds of death of 18.8% (aOR=0.812; 95% confidence interval: 0.748–0.883). Thus, the adjusted odds of mortality increase as much for a drop from, say, 110 to 100mmHg as for 90 to 80mmHg, and so on, throughout the range. Conclusions and Relevance We found a linear relationship between lowest prehospital systolic blood pressure and severity-adjusted probability of mortality across an exceptionally wide range. There is no identifiable threshold or inflection point between 40 and 119mmHg. Thus, in traumatic brain injury, the concept that 90mmHg represents a unique or important physiological “cut-point” may be wrong. Furthermore, clinically-meaningful “hypotension” may not be as low as current guidelines suggest. Randomized trials evaluating treatment levels significantly above 90mmHg are needed.