Respiration and applied tension strategies to reduce vasovagal reactions to blood donation: A randomized controlled trial.

BACKGROUND: Whether produced by breathing too fast or too deeply, hyperventilation is common in stressful situations and may contribute to blood donation-related vasovagal symptoms. The effects of some previously tested interventions for vasovagal symptoms, for example, applied tension (AT), may be related to reduction of hyperventilation. More targeted breathing techniques might be useful. STUDY DESIGN AND METHODS: This was a randomized controlled trial comparing the effects of AT, a slow, shallow "anti-hyperventilation" breathing technique previously tested in phobic individuals (respiration control [RESP]), the combination of AT and RESP, and no intervention on blood donors participating in university clinics. A total of 547 eligible donors were assigned randomly to one of these four groups. Observational, self-report, and physiologic measures (primarily via respiratory capnometry) were obtained. RESULTS: Although both RESP and AT had some positive impact on blood donation outcome, the effects of RESP were more numerous, albeit limited primarily to donors who had less general fear of medical procedures. For example, lower-fear donors assigned to practice RESP had significantly lower Blood Donation Reaction Inventory scores and were significantly less likely to require treatment for symptoms than no-treatment individuals. In general, RESP led to a significant decrease in respiration rate, though it did not influence end-tidal CO2 , a more precise measure of hyperventilation. CONCLUSION: While the mechanisms remain somewhat unclear and the interventions did not benefit more fearful, higher-risk donors, respiration control is a promising additional approach to reducing vasovagal symptoms.

Respiratory and hemodynamic contributions to emotion-related pre-syncopal vasovagal symptoms.

Vasovagal reactions are conventionally understood as resulting from systemic changes in cardiovascular activity; however, there exists a complementary perspective focused on specific changes in cerebral vasoconstriction associated with hyperventilation-induced hypocapnia. The present study investigated the role of cardiovascular and respiratory activity in self-reported pre-syncopal vasovagal reactions to a surgery video in a sample of 49 healthy women. Participants who indicated more previous real-life episodes of dizziness reported experiencing significantly more symptoms in the laboratory consistent with a vasovagal response. They also showed lower total peripheral resistance and higher pre-ejection period in general, suggesting lower sympathetic nervous system activity. Significant decreases in end-tidal carbon dioxide (PETCO2) occurred during the surgery video among susceptible participants, without significant increases in respiration rate. Further, participants who experienced reductions from the neutral video in PETCO2, systolic blood pressure, or both, reported vasovagal symptoms during the surgery video. The results suggest that patterns of respiration associated with decreases in PETCO2 may contribute to vasovagal symptoms reported in non-clinical groups as well as those with blood-injection-injury phobia and are associated with susceptibility to dizziness.