Prepulse inhibition and the call alert in emergency medical services

In emergency medical services, paramedics are informed of an emergency call by a high-intensity acoustic alarm called the "call alert." Sudden, loud sounds like the call alert may cause a startle response and be experienced as aversive. Studies have identified an association between the call alert and adverse health effects in first responders; conceivably, these adverse health effects might be reduced by modifying the call alert to blunt its startling and aversive properties. Here, we assessed whether the call alert causes a startle response and whether its startling and aversive properties are reduced when the call alert is preceded by a weak acoustic "prepulse," a process referred to as "prepulse inhibition" (PPI). Paramedics (n = 50; 34M:13F:3 not reported; ages 20-68) were exposed to four call alerts (two with and two without a prepulse) in counterbalanced order. Responses were measured using electromyography (measuring blink amplitude), visual analog scales (quantifying perceived call alert intensity and aversiveness), and an electrocardiogram (assessing heart rate). Paramedics responded to the call alert with a startle reflex blink and an increased heart rate. Acoustic prepulses significantly reduced the amplitude of the call alert-induced startle blink, the perceived sound intensity, and the perceived "dislike" of the call alert. These findings confirm that the call alert is associated with an acoustic startle response in paramedics; adding a prepulse to the call alert can reduce its startling and aversive properties. Conceivably, such reductions might also diminish adverse health effects associated with the call alert in first responders.