Respiratory changes in vasovagal syncope

Introduction: Respiratory changes accompany the cardiovascular changes duri ng head-up, tilt test-induced vasovagal syncope. Methods and Results: Using the 45-minute 60 degrees head-up Westminster pro tocol, 29 patients were studied (mean age 53.9 +/- 20.0 years; 19 females). Two groups resulted: tilt-induced vasovagal syncope positive and negative. The cardiorespiratory parameters blood pressure (BP), heart rate (HR), tid al volume, and minute volume were measured. Comparisons of the cardiorespir atory parameters were made within the positive group and negative group, an d then between the two groups, There were 14 in the positive group and 15 i n the negative group. Baseline measurements were normalized to 1.0. Compari ng the late tilt periods between the positive and negative groups, there me re differences in BP (P < 0.002), HR (P < 0.002), tidal volume (P < 0.05), and minute volume (P < 0.002), In the positive group comparing early with l ate intervals: BP 1.11 +/- 0.09 versus 0.49 +/- 0.17, P < 0.0001; HR 1.18 /- 0.12 versus 0.85 +/- 0.35, P < 0.009; tidal volume 1.39 +/- 0.34 versus 2.17 +/- 1.00, P < 0.015; and minute volume 1.24 +/- 0.26 versus 3.3 +/- 2. 03, P < 0.0025. There mere no comparable cardiorespiratory changes in the n egative group. Conclusion: There were significant differences in the respiratory and cardi ovascular parameters measured between those who were positive and those who were negative for tilt-induced vasovagal syncope. Within the positive grou p, in addition to the falls in HR and BP, there were significant increases in minute volume and tidal volume during late tilt. This suggests that ther e may be a role for respiratory sensors in vasovagal syncope that may permi t earlier and hence possibly more effective therapy for selected patients.