Visual estimates of blood loss by medical laypeople: Effects of blood loss volume, victim gender, and perspective

Abstract

A severe hemorrhage can result in death within minutes, before professional first responders have time to arrive. Thus, intervention by bystanders, who may lack medical training, may be necessary to save a victim’s life in situations with bleeding injuries. Proper intervention requires that bystanders accurately assess the severity of the injury and respond appropriately. As many bystanders lack tools and training, they are limited in terms of the information they can use in their evaluative process. In hemorrhage situations, visible blood loss may serve as a dominant cue to action. Therefore, understanding how medically untrained bystanders (i.e., laypeople) perceive hemorrhage is important. The purpose of the current study was to investigate the ability of laypeople to visually assess blood loss and to examine factors that may impact accuracy and the classification of injury severity. A total of 125 laypeople watched 78 short videos each of individuals experiencing a hemorrhage. Victim gender, volume of blood lost, and camera perspective were systematically manipulated in the videos. The results revealed that laypeople overestimated small volumes of blood loss (from 50 to 200 ml), and underestimated larger volumes (from 400 to 1900 ml). Larger volumes of blood loss were associated with larger estimation errors. Further, blood loss was underestimated more for female victims than male victims and their hemorrhages were less likely to be classified as life-threatening. These results have implications for training and intervention design.

Comparing Blood Loss Estimates by Medical Laypeople in Online and In-person Formats using SABLE

“…Data is stored on a secure server. The first study using SABLE was conducted in a lab setting using American college students (Phillips et al, 2020a). Consistent with previous research, Phillips et al found that participants overestimated small volumes of blood loss and underestimated large volumes, suggesting that medical laypeople demonstrate the same pattern of results as medical professionals and SABLE is an effective research tool.…”

“…A common finding in research on visual blood loss estimation is that small amounts of blood are overestimated, and large amounts underestimated (Al-Kidri et al, 2014;Frank et al, 2010;Hancock et al, 2015;Phillips et al, 2020a). However, there are relatively few studies of how medical laypeople perceive blood loss.…”

“…10.1177/1071181321651247 mandatory training, not medical laypeople completing a study for research credit. To determine if there is a difference between the results obtained through SABLE in a controlled lab setting and those obtained in an online only setting with less experimental control over distractions and the surrounding environment, data collected in a lab setting (Phillips et al, 2020a) was compared to data collected online.…”

Development of the Aerial Remote Triage System using drones in mass casualty scenarios: A survey of international experts

“…It revealed that laypeople overestimated small volumes of blood loss (50–200 ml) and underestimated larger volumes (400 −1900 ml) [ 48 ]. A similar situation happened with clinicians, regardless of their training and skills [ 49 ]. Thus, the visual estimation of blood loss is usually inaccurate; therefore, it is an inherent limitation of all triage systems.…”

“…their training and skills [49]. Thus, the visual estimation of blood loss is usually inaccurate; therefore, it is an inherent limitation of all triage systems.…”