Expiratory-gated Transcutaneous Auricular Vagus Nerve Stimulation (taVNS) does not Further Augment Heart Rate Variability During Slow Breathing at 0.1 Hz.

As cardiac vagal control is a hallmark of good health and self-regulatory capacity, researchers are seeking ways to increase vagally mediated heart rate variability (vmHRV) in an accessible and non-invasive way. Findings with transcutaneous auricular vagus nerve stimulation (taVNS) have been disappointing in this respect, as its effects on vmHRV are inconsistent at best. It has been speculated that combining taVNS with other established ways to increase vmHRV may produce synergistic effects. To test this idea, the present study combined taVNS with slow breathing in a cross-over design. A total of 22 participants took part in two sessions of breathing at 6 breaths/min: once combined with taVNS, and once combined with sham stimulation. Electrical stimulation (100 Hz, 400 µs) was applied during expiration, either to the tragus and cavum conchae (taVNS) or to the earlobe (sham). ECG was recorded during baseline, 20-minutes of stimulation, and the recovery period. Frequentist and Bayesian analyses showed no effect of taVNS (in comparison to sham stimulation) on the root mean square of successive differences between normal heartbeats, mean inter-beat interval, or spectral power of heart rate variability at a breathing frequency of 0.1 Hz. These findings suggest that expiratory-gated taVNS combined with the stimulation parameters examined here does not produce acute effects on vmHRV during slow breathing.

Transcutaneous Auricular Vagus Nerve Stimulation Combined With Slow Breathing: Speculations on Potential Applications and Technical Considerations.

OBJECTIVES: Transcutaneous auricular vagus nerve stimulation (taVNS) is a relatively novel noninvasive neurostimulation method that is believed to mimic the effects of invasive cervical VNS. It has recently been suggested that the effectiveness of taVNS can be enhanced by combining it with controlled slow breathing. Slow breathing modulates the activity of the vagus nerve and is used in behavioral medicine to decrease psychophysiological arousal. Based on studies that examine the effects of taVNS and slow breathing separately, this article speculates on some of the conditions in which this combination treatment may prove effective. Furthermore, based on findings from studies on the optimization of taVNS and slow breathing, this article provides guidance on how to combine taVNS with slow breathing. MATERIALS AND METHODS: A nonsystematic review. RESULTS: Both taVNS and slow breathing are considered promising add-on therapeutic approaches for anxiety and depressive disorders, chronic pain, cardiovascular diseases, and insomnia. Therefore, taVNS combined with slow breathing may produce additive or even synergistic beneficial effects in these conditions. Studies on respiratory-gated taVNS during spontaneous breathing suggest that taVNS should be delivered during expiration. Therefore, this article proposes to use taVNS as a breathing pacer to indicate when and for how long to exhale during slow breathing exercises. CONCLUSIONS: Combining taVNS with slow breathing seems to be a promising hybrid neurostimulation and behavioral intervention.

Training of paced breathing at 0.1 Hz improves CO2 homeostasis and relaxation during a paced breathing task.

Volitional control of breathing often leads to excessive ventilation (hyperventilation) among untrained individuals, which disrupts CO2 homeostasis and may elicit a set of undesirable symptoms. The present study investigated whether seven days of training without any anti-hyperventilation instructions improves CO2 homeostasis during paced breathing at a frequency of 0.1 Hz (6 breaths/minute). Furthermore, the present study investigated the effects of training on breathing-related changes in affective state to examine the hypothesis that training improves the influence of slow paced breathing on affect. A total of 16 participants performed ten minutes of paced breathing every day for seven days. Partial pressure of end-tidal CO2 (PetCO2), symptoms of hyperventilation, affective state (before and after breathing), and pleasantness of the task were measured on the first, fourth, and seventh days of training. Results showed that the drop in PetCO2 significantly decreased with training and none of the participants experienced a drop in PetCO2 below 30 mmHg by day seven of training (except one participant who already had PetCO2 below 30 mmHg during baseline), in comparison to 37.5% of participants on the first day. Paced breathing produced hyperventilation symptoms of mild intensity which did not decrease with training. This suggests that some participants still experienced a drop of PetCO2 that was deep enough to produce noticeable symptoms. Affective state was shifted towards calmness and relaxation during the second and third laboratory measurements, but not during the first measurement. Additionally, the breathing task was perceived as more pleasant during subsequent laboratory measurements. The obtained results showed that training paced breathing at 0.1 Hz led to decrease in hyperventilation. Furthermore, the present study suggests that training paced breathing is necessary to make the task more pleasant and relaxing.

Correction to: An Anti-hyperventilation Instruction Decreases the Drop in End-tidal CO2 and Symptoms of Hyperventilation During Breathing at 0.1 Hz.

The original version of this article unfortunately contained an error in abstract section. The number of participants should be "Forty-six participants" instead of "Thirty-six participants". The correct sentence is as follows: Forty-six participants were randomly assigned to one of two groups: a group given an anti-hyperventilation instruction and a control group without such an instruction. The original article has been corrected.

An Anti-hyperventilation Instruction Decreases the Drop in End-tidal CO2 and Symptoms of Hyperventilation During Breathing at 0.1 Hz.

Breathing at a frequency of around 0.1 Hz is widely used in basic research and in applied psychophysiology because it strongly increases fluctuations in the cardiovascular system and affects psychological functioning. Volitional control of breathing often leads to hyperventilation among untrained individuals, which may produce aversive symptoms and alter the psychological and physiological effects of the paced breathing. The present study investigated the effectiveness of a brief anti-hyperventilation instruction during paced breathing at a frequency of 0.1 Hz. Forty-six participants were randomly assigned to one of two groups: a group given an anti-hyperventilation instruction and a control group without such an instruction. The instruction asked participants to avoid excessively deep breathing and to breathe shallowly and naturally. Participants performed the breathing task for 10 min. Hyperventilation was measured by partial pressure of end-tidal CO2 (PetCO2); furthermore, symptoms of hyperventilation, feeling of air hunger, task difficulty, and affective state were measured by self-report. The results showed that paced breathing without instruction decreased PetCO2 by 5.21 mmHg and that the use of the anti-hyperventilation instruction reduced the drop in PetCO2 to 2.7 mmHg. Symptoms of hyperventilation were lower in the group with the anti-hyperventilation instruction. Neither the feeling of air hunger nor task difficulty were affected by the instruction. There were no significant effects of the instruction on affective state. The present study indicates that a brief anti-hyperventilation instruction may be used to decrease drop in PetCO2 and symptoms of hyperventilation during breathing at 0.1 Hz and that the instruction is well tolerated.

The effects of breathing at a frequency of 0.1 Hz on affective state, the cardiovascular system, and adequacy of ventilation.

The present study aimed to investigate changes induced by breathing at 0.1 Hz in affective state, cardiovascular activity, and adequacy of ventilation as well as the relation between changes in peripheral physiological processes and alteration of affect. Eighty-three participants were randomly assigned to one of three groups: Two groups doing paced breathing at 0.1 Hz, one with and the other without a cover story hiding the goal of the experiment, and, as a control, paced breathing at 0.28 Hz. We measured the effects of breathing at 0.1 Hz on affective state (unpleasant and pleasant arousals), respiratory sinus arrhythmia (RSA), sympathetic control of the heart (preejection period, PEP), and adequacy of ventilation as measured by partial pressure of end-tidal CO2 (PetCO2 ). The use of a cover story did not influence the effects of paced breathing on the study outcomes. In the 0.1 Hz groups, unpleasant arousal decreased only among men. Changes in RSA were not related to changes in affect. Respiratory frequency did not influence PEP. However, changes in PEP were inversely related to changes in pleasant arousal. PetCO2 decreased in all conditions, and a larger drop in PetCO2 predicted a greater decrease in unpleasant arousal. The results obtained corroborate previous findings showing that slow paced breathing may lead to moderate hyperventilation among untrained participants and suggest that hyperventilation during breathing at 0.1 Hz is not deep enough to produce an increase in affective arousal.