Protocol adherence
The protocol was well tolerated. All MS participants were able to learn and perform the surgical tasks, and all participants completed the protocol. The music intervention and control conditions did not need to be turned off for any participant.
Participant Characteristics
The MS group (n=15) were aged 23±2.7 years (mean±SD), with a height and weight of 170±10 cm and 67±21 kg, respectively. Ten (67%) were female and five (33%) were students who were in the first three university-based years of the undergraduate degree, and the remaining were in their final three hospital-based years. The pop genre was the most popular choice of the music intervention (n=4), although choices also included classical, Rhythm and blues, atmospheric instrumental, jazz and metal. The VS group (n=12) were older (42±10 years; p<0.0001 vs. MS), taller (179±8 cm; p=0.01), heavier (81±12 kg; p=0.04) and more likely to be male (p<0.01). There was 1 female participant and 8 were consultant surgeons. The most popular choices in the VS group were pop, easy listening and 80s music equally
Surgical Performance
Figure 2 illustrates the mean performance measures for the surgical task. Significant group effects were observed for time to completion (F(1,25)=43.4, p<0.0001), errors (F(1,25)=28.9, p<0.0001), and global rating scale (F(1,25)=16.4, p=0.0004). The VS cohort (mean difference of main effect, 95% CI) were faster to complete the task (-10 minutes [-13.2 - -6.8]), made fewer errors (-4 [-7 - -3]) and had higher self-rated scores (6 [2-9]). Music did not affect time to completion, number of errors or global rating scale (i.e., no condition effect was observed).
Psychological Responses
SURG-TLX total score and STAI-6 total score for baseline, music, and control (condition main effect) for MS and VS (group main effect) are shown in Figure 3 and Table 2. There was an interaction between condition and group for SURG-TLX total score (F(2,50) = 12.36, p<0.0001). MS exhibited pronounced increases from baseline by D40 [26-55, p<0.0001] with music, and by D44 [31-57, p<0.0001] with control, that tended to be greater than VS who exhibited increases from baseline by D17 [7-28, p<0.01] in music and by D17 [8-27, p<0.01] in control. SURG-TLX total score was not different between music and control in either group (MS p=0.392 VS p=1.000). A significant main effect of condition was noted for STAI-6 total scores (F(1.9,48.3)=18.7, P<0.0001), with an increase from baseline to control (D3 [1.7-4.3], p<0.0001) and baseline to music (D3 [1.4-4.3], p=0.0001), but no difference observed between music and control (-0.15 [-1.4-1.1], p=0.955).
Physiological Responses
Figure 4 demonstrates the HR, MCA Vm, PETCO2, and RR responses to the surgical task at four timepoints (rest, start, midpoint and end; time main effect), in MS and VS (group main effect), for music and no music (condition main effect). HR increased from baseline at all timepoints (time main effect; F(3,75)=14.2, p<0.0001) and reached a peak at the end of the task (D5.1bpm [3.0-7.1] vs. baseline, p<0.0001). HR was lower in VS (group main effect; F(1,25)=14.8, p=0.0007) but was not affected by music (condition main effect; p=0.204). Similarly, MCA Vm was increased from baseline at all timepoints during the task (time main effect; F(3,75)=36.8, p<0.0001) and was lower in VS (group main effect; F(1,25)=9.2, p=0.006), but was not affected by music (condition main effect; F(1,25)=3.0, p=0.094). PETCO2 increased during the task (time main effect; F(3,75)=15.8, p<0.0001) reaching a peak at the midpoint (+1.5 [0.95-2.1] mmHg, p<0.0001), and overall was lower with music (condition main effect; F(1,25)=5.0, p=0.034). RR increased only at the end of the task (time main effect; F(3,75)=2.9, p=0.040; +1.7 [0.3-3.0] bpm vs baseline, p<0.01). MAP was higher in VS than MS (group main effect; F(1,25)=6.0, p=0.022), although not different between conditions (condition main effect; F(1,25)=0.05, p=0.822).
HRV Responses
HRV parameters for the baseline, music, and control conditions, in the MS and VS groups, are shown in Table 1 and Figure 5. For PNS Index, there was a main effect of condition (F(1.1,27.8)=17.5, p=0.0002). with PNS Index being lower than baseline in both control (-0.45 [-0.73 - -0.18], p<0.0009) and music (-0.57 [-0.91 - -0.23], p<0.0009), and lower in music than control (-0.11 [-0.22 - -0.008], p=0.032). There was also a main effect of group (F(1,25)=5.9, p=0.023), such that MS had a lower PNS index (-0.8 [-1.5- -0.12]) than VS. There was a main effect of condition (F(1.1,28.3)=12.6, p=0.001) for SNS Index with values being higher than baseline during both control (0.54 [0.96 – 0.13], p<0.009) and music (0.68 [0.22 – 1.14], p<0.003), and higher during music than control (0.14 [0.004 – 0.27], p=0.042). SNS index was higher in MS than VS (group main effect F(1,25)=6.2, p=0.019; D+1.0 [0.17-1.8]).
There was a main effect of condition for RMSSD (F(1.2, 30.2)=5.6, p=0.020), with a tendency for a decrease from baseline during music (-5.98 [-12.4-0.48], p=0.073) and control (-3.72 [-8.9-1.4], p=0.192), and lower values during music than control (-2.3 [-4.7-0.24], p=0.081). Total power also exhibited a main effect of condition (F(1.3,32.3)=3.9, p=0.046), with lower values in music than control (-322 [-624 - -20], p=0.035). There was a main effect of condition for high frequency parameters (F(1.3,32.2)=4.2, p=0.038), though no significant results on post-hoc analysis. There were no significant main effects or interactions noted for low frequency power and LF/HF ratio, while there was an interaction between condition and group for Baevsky’s stress index (F(2,50)=3.6, p=0.035), although no significant post hoc differences were observed.