Proceedings of the Human Factors and Ergonomics Society Annual Meeting | 2019
Middle Cerebral Artery Blood Flow Velocity as an Indicator of Attentional Load and Attentional Resource Depletion in the Laparoscopic Training Environment
Abstract
Laparoscopies require surgeons to perform surgery while viewing their actions and the target tissue on a video monitor. This surgical approach has advantages for patients on a variety of outcome measures (Cuschierie, 1995; McGreevy et al., 2003; Rattner, 1999; Varela, Wilson, & Nguyen, 2010). Yet, compared to traditional surgical methods, the laparoscopic environment places unique demands upon surgeons. The requirement that surgeons view their actions, instruments, and the surgical site indirectly on a monitor has been shown to induce perceptual-motor distortions and disruptions of handeye mapping. These perceptual disturbances have been associated with increases in attentional load/workload, as indicated by an increase in global NASA TLX scores, especially when the camera must be positioned to the surgeon’s side (Klein, Riley, Warm, & Matthews, 2005). The experience of high attentional load in the laparoscopic environment is further amplified by surgeons’ needing to remain vigilant in order to detect critical information pertaining to the patient and the surgery. The need for vigilance is a human factors concern, because prior vigilance research has demonstrated that humans typically experience a performance decline that occurs over time (i.e., the vigilance decrement; Warm et al., 2015). Within the surgical theatre, the vigilance decrement could cause a surgeon to fail to detect critical information relating to patient safety. Extant vigilance research indicates that the onset and severity of the vigilance decrement is largely determined by the difficulty of the vigilance task and/or additional tasks (Warm et al., 2015). Specifically, as demands increase, overall vigilance performance suffers, the onset of the vigilance decrement is hastened, and the magnitude of the vigilance decrement is magnified. This link between task demands and vigilance performance represents the foundation for the resource theory of vigilance, which posits that the decline in vigilance performance is caused by the depletion of limited attentional resources required to maintain vigilance. Further support for resource theory comes from neuroergonomic research utilizing transcranial Doppler sonography (TCD), a technology that measures blood flow velocity (BFV) within cerebral arteries. BFV is correlated with cognitive activity, due to neurovascular coupling. That is, increases in neural activity, such as during increased difficulty of cognitive tasks, cause metabolic demands to increase and carbon dioxide (CO2) to be produced. In order to remove the excess CO2 associated with increased neural activity, BFV increases (Tripp & Warm, 2007). Vigilance research using this technique has focused on the middle cerebral artery (MCA), and has shown that the vigilance decrement is accompanied by a decline of blood blow velocity (BFV) of the middle cerebral arteries; this BFV decline has been interpreted as an objective index of neural resource depletion (MCA; Shaw et al., 2009). Like performance, BFV is affected by task demands such that increased demands increase the initial level of BFV, expedite the onset of the BFV decline, and amplify the degree of decline (Warm & Parsuraman, 2007). This BFV decline is typically most prominent within the right MCA, indicating lateralization of neural vigilance resources (Warm & Parasuraman, 2007). The aim of the present study was to apply TCD measurement of the MCA to the laparoscopic environment. Specifically, we assessed whether BFV of the MCAs was sensitive to increases in attentional load that tend to occur when a side camera view is provided instead of a frontal camera view. We also tested the possibility that BFV of the MCA would be sensitive to the temporal decline of attentional resources that is thought to cause the vigilance decrement. Thirty-four medical students (17 males, 17 females; Mage = 25.18, SDage = 2.47) took part in this study in exchange for $100 USD. All participants completed a 40-minute dual-task paradigm which required continuous and simultaneous engagement with a laparoscopic peg-transfer task and an auditory vigilance task. The apparatus and procedures of the peg-transfer task were based upon Klein, Wheeler, & Craig (2015). Briefly, that task required use of two laparoscopic graspers which were used to move ring-shaped, foam stars from one peg to another inside a laparoscopic simulator. The simulator was completely opaque; the only view of the pegboard was a video feed presented on a computer monitor. The angle of the camera was manipulated between participants, such that half of participants were presented with a frontal view (0°) and the other half were presented with a side view (90°). All participants completed the same auditory vigilance task, which was based upon Shaw and colleagues (2009) and involved monitoring sequential white-noise bursts for rare (5.33%) 200 ms bursts among common 247.5 ms bursts. Participants reported detection of rare bursts by pressing a foot pedal. Results indicated that peg-transfer performance was significantly worse (slower, less accurate) in the 90° condition, compared to the 0° condition. Peg-transfers in the 90° condition became faster (better) over time, whereas there were no changes in the 0° which was consistently faster than 90°. Vigilance performance (correct detections) declined significantly over 40-minutes. Analyses of BFV revealed that it too declined significantly over time, which suggests that BFV was sensitive to the temporal resource depletion associated with the vigilance decrement. Additionally, camera angle interacted with cerebral hemisphere such that cerebral asymmetry was observed in the 0° condition, but not in the 90° condition. This is in line with previous research that has found hemispheric asymmetries to be present within relatively Proceedings of the Human Factors and Ergonomics Society 2019 Annual Meeting