Anxiety, pCO2 and cerebral blood flow.

This study examined the effect of anxiety on cerebral blood flow at different levels of pCO2 in healthy participants (N=29). Three types of breathing were used to manipulate pCO2 in a within-subject threat-of-shock paradigm: spontaneous breathing, CO2-inhalation and hyperventilation resulting in normo-, hyper- and hypocapnia. Transcranial Doppler ultrasonography was used to measure CBF velocity (CBFv) in the right middle cerebral artery, while breathing behavior and end-tidal pCO2 were monitored.

Feeling lightheaded: the role of cerebral blood flow.

Objective: The main aims of this study were a) to investigate the relationship between lightheadedness and cerebral blood flow velocity (CBFv) during hyperventilation-induced hypocapnia, and b) to investigate whether and why the relationship between lightheadedness and CBFv may change after several episodes of this sensation.

Methods: Three hypocapnic and three normocapnic overbreathing trials were administered in a semirandomized order to healthy participants (N = 33). Each type of breathing trial was consistently paired with one odor.

Defense reactions to interoceptive threats: a comparison between loaded breathing and aversive picture viewing.

Human fear research has mostly applied exteroceptive stimuli to induce fear. Interoceptive sensations however can also be very threatening and play a major role in a number of anxiety disorders. In this study, we compared affective responses to inspiratory resistive loads with those to aversive pictures.

Distorted symptom perception in patients with medically unexplained symptoms.

The present study investigated differences in symptom perception between a clinical sample with medically unexplained symptoms (MUS) and a matched healthy control group. Participants (N = 58, 29 patients) were told that they would inhale different gas mixtures that might induce symptoms. Next, they went through 2 subsequent rebreathing trials consisting of a baseline (60 s room air breathing), a rebreathing phase (150 s, which gradually increased ventilation, PCO2 in the blood, and perceived dyspnea), and a recovery phase (150 s, returning to room air breathing).

Why do you sigh? Sigh rate during induced stress and relief.

Whereas sighing appears to function as a physiological resetter, the psychological function of sighing is largely unknown. Sighing has been suggested to occur both during stress and negative emotions, such as panic and pain, and during positive emotions, such as relaxation and relief. In three experiments, sigh rate was investigated during short imposed states of stress and relief.

Acquired lightheadedness in response to odors after hyperventilation.

Objective: This study aimed to investigate whether lightheadedness in response to odors could be acquired through previous associations with hyperventilation-induced hypocapnia.

Methods: Diluted ammonia and acetic acid served as conditional odor cues (CSs) in a differential associative learning paradigm. Hyperventilation-induced hypocapnia (unconditional stimulus [US]) was used to induce lightheadedness.