Effect of anticipation triggered by a prior dyspnea experience on brain activity

[Purpose] Oxygenated hemoglobin (oxy-Hb) concentrations in the prefrontal cortex are closely associated with dyspnea. Dyspnea is influenced not only by physical activity, but also by visual stimuli, and several studies suggest that oxy-Hb concentrations change in response to certain external stimuli. However, the effects of internal psychological states on dyspnea have not been reported. This study explored the influence of anticipation triggered by previous episodes of dyspnea on brain activity. [Subjects] The subjects were 15 healthy volunteers with a mean age of 25.0 ± 3.0 years. [Methods] The subjects were shown a variety of photographs and instructed to expect breathing resistance matched to the affective nature of the particular photograph. After viewing the images, varying intensities of breathing resistance that were identical to, easier than, or harder than those shown in the images were randomly administered to the subjects; in fact, the image and resistance were identical 33% of the time and discordant 66% of the time. [Results] The concentrations of oxy-Hb in the right medial prefrontal cortex (rMPFC) increased significantly with an inspiratory pressure that was 30% of the maximum intensity in the subjects shown a pleasant image compared to the concentrations in subjects shown an unpleasant image. Moreover, rMPFC activity was significantly correlated with the magnitude of the dyspnea experienced. [Conclusion] These results suggest that a correlation exists between increased oxy-Hb in the rMPFC and the effects of expectations on dyspnea.

Respiratory symptom perception differs in obese women with strong or mild breathlessness during constant-load exercise

BACKGROUND

During constant-load exercise, some otherwise healthy obese women report substantially more dyspnea on exertion (DOE) than do others. The objective of this study was to investigate whether qualitative differences exist between the sensations of dyspnea felt by these women.

METHODS

Seventy-eight women were categorized based on their ratings of perceived breathlessness (RPBs) (Borg 0-10 scale) after 6 min of 60-W cycling. Thirty-four women rated RPB ≥ 4 (+DOE) (34 ± 7 years, 36 ± 5 kg/m² BMI), and 22 women rated RPB ≤ 2 (-DOE) (32 ± 7 years, 37 ± 4 kg/m² BMI). Twenty-two women rated RPB as 3 (RPB = 3) (34 ± 7 years, 34 ± 4 kg/m² BMI) and were grouped separately to allow for a better delineation of the +DOE and the -DOE groups. After the exercise test, subjects were asked to pick three of 15 statements that best described their respiratory sensations.

RESULTS

The +DOE and the -DOE groups were characterized differentially (P < .05) by the respiratory clusters "Breathing more" (82% of -DOE vs 41% of +DOE), "Shallow" (36% vs 6%), and "Heavy" (14% vs 53%). All four descriptors in the cluster "Work/Effort" were chosen more frequently by women in the +DOE group than by women in the -DOE group. Although relative exercise intensity was higher in the +DOE women (75% ± 13% vs 67% ± 10% of oxygen uptake at peak exercise, 41 ± 10 L/min vs 31 ± 8 L/min as % maximal voluntary ventilation, 83% ± 7% vs 76% ± 7% of peak heart rate), none of these variables was significantly associated with RPB.

CONCLUSIONS

Not only is the intensity of dyspnea significantly different between the +DOE and the -DOE groups, but so are the self-reported qualitative aspects of their dyspnea. Women in the +DOE group reported an increased sensation of the work of breathing relative to women in the -DOE group, which may be associated with the elevated RPB.

Changes in P300 following alternate nostril yoga breathing and breath awareness

This study assessed the effect of alternate nostril yoga breathing (nadisuddhi pranayama) on P300 auditory evoked potentials compared to a session of breath awareness of equal duration, in 20 male adult volunteers who had an experience of yoga breathing practices for more than three months. Peak amplitudes and peak latencies of the P300 were assessed before and after the respective sessions. There was a significant increase in the P300 peak amplitudes at Fz, Cz, and Pz and a significant decrease in the peak latency at Fz alone following alternate nostril yoga breathing. Following breath awareness there was a significant increase in the peak amplitude of P300 at Cz. This suggests that alternate nostril yoga breathing positively influences cognitive processes which are required for sustained attention at different scalp sites (frontal, vertex and parietal), whereas breath awareness brings about changes at the vertex alone.

Respiratory muscle tension as symptom generator in individuals with high anxiety sensitivity

OBJECTIVE

Anxiety and panic are associated with the experience of a range of bodily symptoms, in particular unpleasant breathing sensations (dyspnea). Respiratory theories of panic disorder have focused on disturbances in blood gas regulation, but respiratory muscle tension as a source of dyspnea has not been considered. We therefore examined the potential of intercostal muscle tension to elicit dyspnea in individuals with high anxiety sensitivity, a risk factor for developing panic disorder.

METHODS

Individuals high and low in anxiety sensitivity (total N=62) completed four tasks: electromyogram biofeedback for tensing intercostal muscle, electromyogram biofeedback for tensing leg muscles, paced breathing at three different speeds, and a fine motor task. Global dyspnea, individual respiratory sensations, nonrespiratory sensations, and discomfort were assessed after each task, whereas respiratory pattern (respiratory inductance plethysmography) and end-tidal carbon dioxide (capnography) were measured continuously.

RESULTS

In individuals with high compared to low anxiety sensitivity, intercostal muscle tension elicited a particularly strong report of obstruction (M=5.1, SD=3.6 versus M=2.5, SD=3.0), air hunger (M=1.9, SD=2.1 versus M=0.4, SD=0.8), hyperventilation symptoms (M=0.6, SD=0.6 versus M=0.1, SD=0.1), and discomfort (M=5.1, SD=3.2 versus M=2.2, SD=2.1) (all p values<.05). This effect was not explained by site-unspecific muscle tension, voluntary manipulation of respiration, or sustained task-related attention. Nonrespiratory control sensations were not significantly affected by tasks (F<1), and respiratory variables did not reflect any specific responding of high-Anxiety Sensitivity Index participants to intercostal muscle tension.

CONCLUSIONS

Respiratory muscle tension may contribute to the respiratory sensations experienced by panic-prone individuals. Theories and treatments for panic disorder should consider this potential source of symptoms.

Reliability and validity of the multidimensional dyspnea profile

BACKGROUND

Most measures of dyspnea assess a single aspect (intensity or distress) of the symptom. We developed the Multidimensional Dyspnea Profile (MDP) to measure qualities and intensities of the sensory dimension and components of the affective dimension. The MDP is not indexed to a particular activity and can be applied at rest, during exertion, or during clinical care. We report on the development and testing of the MDP in patients with a variety of acute and chronic cardiopulmonary conditions.

METHODS

One hundred fifty-one adults admitted to the ED with breathing symptoms completed the MDP three times in the ED, twice at least 1 h apart (T1, T2), and near discharge from the ED (T3). Measures were repeated in 68 patients twice in a follow-up session 4 to 6 weeks later (T4-T5). The ED sample was 56% men with a mean age of 53 ± 15 years; the follow-up sample was similar.

RESULTS

Factor analysis resulted in a two-factor solution with a total explained variance of 63%, 74%, and 72% at T1, T2, and T3, respectively. One domain related to primary sensory qualities and immediate unpleasantness, and the second encompassed emotional response. For the two domains, Cronbach α ranged from 0.82 to 0.95, and the intraclass correlation coefficient ranged from 0.91 to 0.98. Repeated-measures analysis was significant for change (T1, T3, T4), showing responsiveness to change in MDP domains with treatment (F([2,66]) = 19.67, P > .001).

CONCLUSIONS

These analyses support the reliability, validity, and responsiveness to clinical change of the MDP with two domains in an acute care and follow-up setting.

Respiratory and leg muscles perceived exertion during exercise at altitude

We compared the rate of perceived exertion for respiratory (RPE,resp) and leg (RPE,legs) muscles, using a 10-point Borg scale, to their specific power outputs in 10 healthy male subjects during incremental cycle exercise at sea level (SL) and high altitude (HA, 4559 m). Respiratory power output was calculated from breath-by-breath esophageal pressure and chest wall volume changes. At HA ventilation was increased at any leg power output by ∼ 54%. However, for any given ventilation, breathing pattern was unchanged in terms of tidal volume, respiratory rate and operational volumes of the different chest wall compartments. RPE,resp scaled uniquely with total respiratory power output, irrespectively of SL or HA, while RPE,legs for any leg power output was exacerbated at HA. With increasing respective power outputs, the rate of change of RPE,resp exponentially decreased, while that of RPE,legs increased. We conclude that RPE,resp uniquely relates to respiratory power output, while RPE,legs varies depending on muscle metabolic conditions.

Dependency of illness evaluation on the social comparison context: findings with implicit measures of affective evaluation of asthma

OBJECTIVES

The affective dimension of illness representation plays an important role in asthma self-management. However, little is known about the stability of this affective representation across contexts. We explored the role of social comparison in this affective evaluation.

DESIGN AND METHODS

Participants included 20 individuals reporting an asthma diagnosis and 33 healthy controls. To measure asthma attitudes, we used three different versions of the Implicit Association Test (IAT), a single target IAT (ST-IAT) and two IATs with different social comparison standards for asthma evaluation (1) HIV and (2) diabetes. Reaction times to pair asthma with positive or negative word stimuli in the three IATs were compared in a repeated measure ANOVA. Furthermore, the relationship between affective evaluation, self-reported asthma-specific coping, and negative affect was explored.

RESULTS

Individuals reporting an asthma diagnosis showed a stronger negative evaluation of asthma than healthy individuals in the ST-IAT. This negative evaluation was positively related to the self-report of dysfunctional coping strategies. However, in the IAT introducing a downward social comparison with HIV, evaluation of asthma was less negative and no longer positively related to the report of dysfunctional coping.

CONCLUSION

Downward social comparison can buffer against negative affective evaluation of asthma. The context dependency of illness-related attitudes requires attention in future research and asthma management practice.