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PubMed1987

A non-invasive method for measuring inspiratory muscle fatigue during progressive isocapnic hyperventilation in man.

Eleven normal adults each performed a ten minute progressive isocapnic hyperventilation (PIHV) test in which ventilatory levels were increased every two minutes. All subjects exhibited mechanical fatigue by failing to maintain the target of 80% of maximum voluntary ventilation (MVV). The mean ventilation at this level was 67.5 +/- 1.4% MVV. This fatigue was accompanied by a fall in transdiaphragmatic pressure. During the test the EMG of the sternomastoid (SM) was monitored by surface electrodes and was analyzed using fast-fourier transform. The centroid frequency (Fc) fell as ventilation increased, and correlated negatively with the inability to achieve target ventilation(r = -0.99, p less than 0.015). Five subjects performed the test while the diaphragmatic EMG was recorded from an oesophageal electrode (DIes) and from surface electrodes (DIs). The Fc of DIes fell with increasing ventilation levels (r = -0.95, p less than 0.05) and there was a correlation between the Fc changes of both DIes and the SM (r = -0.92, p less than 0.001). The Fc of DIs did not correlate with either mechanical performance or the Fc of DIes, because of contamination of surface signals by signals from expiratory muscles. It is concluded that the PIHV along with surface monitoring of EMG activity from the sternomastoid can serve as a non-invasive method for evaluating inspiratory muscle fatigue.

Adult↗
PubMed1976

Metabolic control of respiratory neuronal activity and the accompanying changes in breathing movements of the rabbit. III. Phase shifts in respiratory neurons induced by inflation and collapse of the lung, hyperventilation, or metabolic modifiers.

Phase shifts between inspiratory-related and expiratory-related discharge patterns can be reversibly induced in respiratory neurons following volume changes of the lung, hypocapnic apnea as a result of hyperventilation, or superfusion with certain metabolic modifiers. Phase-spanning expiratory-inspiratory or inspiratory-expiratory discharges are frequently induced in those neurons which are activated either by pulmonary stretch receptors or collapse afferents. The same is true for regulatory effectors which activate key steps of the neuronal metabolism such as ADP, 3-phosphoglycerate, L-glutamine, fructose-6-phosphate and fructose-1,6-diphosphate. In contrast, inhibitory vagal inputs or superfusion with citrate, an inhibitory metabolic modifier, revert preexisting expiratory-inspiratory discharges into a phase-coupled inspiratory pattern. It is postulated that the respiratory neuronal networks represents a time-optimal control system which strives to adjust to a new equilibrium value in a minimum of time, following a given mechanical or chemical perturbation. Following the hypothesis advanced by Cohen (1974) that the phase-spanning units modulate the activity of the in-phase neurons, it is suggested that the additional recruitment of expiratory-inspiratory and inspiratory-expiratory units provides a measure of the quality of time-optimal control and hence a performance index of the system.

Animals↗
PubMed1988

Trachea-noise biofeedback in asthma: a comparison of the effect of trachea-noise biofeedback, a bronchodilator, and no treatment on the rate of recovery from exercise- and eucapnic hyperventilation-induced asthma.

We review some of the evidence that supports the existence of psychosomatic triggers to bronchospasm in asthmatics, and hypothesize that it may also be possible to consciously reverse bronchospasm using trachea-noise biofeedback. We precipitated significant levels of bronchospasm in 16 asthmatics using exercise or eucapnic-hyperventilation challenges on five occasions, and administered four different treatments and a no-treatment control. The treatments were trachea-noise biofeedback (TNBF), wrong-information TNBF, an inhaled adrenergic bronchodilator, and a placebo inhaler, all given double blind. Half of the subjects had 3 training days in the use of the TNBF device before study. Our results show that TNBF, in the trained subjects only, is associated with a detectable, but not statistically significant, increase in the rate of recovery from bronchospasm over that found with no treatment. We conclude that, although asthmatics seem to have a strong ability to consciously induce bronchospasm, conscious reversal of a full asthma attack using TNBF is limited. Despite contrary conclusions by other investigators, we believe that this study demonstrated little TNBF-assisted recovery from bronchospasm. We suggest that this is because its effect may be inhibited by humoral mechanisms that sustain the attack, but we believe further work is required to support this.

Adult↗
PubMed1994

Effort syndrome: hyperventilation and reduction of anaerobic threshold.

Effort syndrome is an entity in danger of being subsumed into "chronic fatigue syndrome" and lost to sight. Its distinctive feature is the reduction of the anaerobic threshold for work by depletion of the body's alkaline buffering systems through hyperventilation. This article describes the history and clinical features of effort syndrome and reports a study in which capnography is used to identify the anaerobic threshold by registering the respiratory response to the onset of metabolic acidosis. The patients' thresholds are low, and provide a goal for rehabilitation. In other forms of chronic fatigue syndrome, the pathogenesis and logic of therapy are unclear.

Adult↗
PubMed1990

Changes in regional cerebral blood flow after hyperventilation in the pig with an induced focal cerebral contusion.

Changes in regional cerebral blood flow in anaesthetized pigs with an induced focal cerebral contusion were studied before and after two grades of hyperventilation. A reduction in arterial tension of CO2 with 0.70 mmHg and a further reduction of 0.55 mmHg did not change the CO2 reactivity. Reactivity in both injured and macroscopically normal regions was the same, revealing an average of 39.3% flow change per kPa change in CO2 tension. Regions with low flow after the contusion had an equally big reduction apparently leading to hypoxia because global metabolic rate was unchanged.

Animals↗
PubMed1979

Hyperventilation and inhibitory synapses.

Injection of a subconvulsive dose of strychnine (which blocked the inhibitory synapses) increases respiratory muscle activity evoked by stimulation of a sciatic nerve as well as by inhalation of hypercapnic gas mixture. Thus the inhibitory synapses prevent an excessive hyperventilation.

Animals↗
PubMed1991

Hyperventilation as a model for acute ischaemic hypoxia of the brain: effects on cortical auditory evoked potentials.

Controlled hyperventilation (HV) may be used as an experimental procedure to produce transient ischaemic hypoxia of the brain. The effect of HV on the cortical auditory evoked potential (AEP) components N1 and P2 was studied in ten healthy adult subjects. AEP were recorded before HV, during 3 min of controlled HV, and 1 min and 5 min after the end of HV. The P2 amplitude was significantly reduced by HV and regained its initial value 1 min after the end of HV. The P2 amplitude decrease probably reflects an impairment of synaptic function produced by cerebral hypoxia. Thus, the investigation of cortical AEP components may provide a useful parameter in the study of anti-ischaemic or anti-hypoxic therapies.

Adolescent↗
PubMed1996

Breathing retraining: a three-year follow-up study of treatment for hyperventilation syndrome and associated functional cardiac symptoms.

This study was designed to evaluate the long-term effects of paced diaphragmatic breathing on subjects who reported functional cardiac symptoms and who also demonstrated associated signs of hyperventilation syndrome. Subjects were a representative sample composed of 10 out of the original 41 subjects who had participated three years previously in a study designed to evaluate the short-term effects of breathing retraining on functional cardiac symptoms and respiratory parameters (respiratory rate and end-tidal carbon dioxide). The results of this follow-up study indicate that breathing retraining had lasting effects on both respiratory parameters measured. Subjects evidenced significantly higher end-tidal carbon dioxide levels and lower respiratory rates when compared to pretreatment levels measured three years earlier. Subjects also continued to report a decrease in the frequency of functional cardiac symptoms when compared to pretreatment levels. We conclude that breathing retraining has lasting effects on respiratory physiology and is highly correlated with a reduction in reported functional cardiac symptoms.

Female↗
PubMed1999

Phase changes caused by hyperventilation stress in spastic angina pectoris analyzed by first-pass radionuclide ventriculography.

To understand the effect of hyperventilation (HV) stress in patients with spastic angina, left ventricular (LV) contraction was analyzed by quantitative phase analysis. The study was performed on 36 patients with spastic angina pectoris, including vasospastic angina pectoris (VspAP: 16 patients) and variant angina pectoris (VAP: 20 patients). First-pass radionuclide ventriculography (first-pass RNV) was performed at rest and after HV stress, and standard deviation of the LV phase distribution (SD) was analyzed. The SD was lower in patients with VspAP than in VAP (12.8+/-1.4 degrees vs. 14.6+/-2.2 degrees, p < 0.005) at rest. After HV stress, the SD (HVSD) tended to increase in VspAP patients (62.5%), whereas the SD decreased in VAP patients (70%). Due to HV stress, the percentage change in SD (%SD) in VspAP patients was 8.9+/-23.7% whereas that in VAP patients was -9.1+/-17.3% (p < 0.01). Moreover, phase histograms were divided into HVSD increase and HVSD decrease groups. The HVSD increase group had a decrease of HVEF, but the HVSD decrease group tended to have more decreased HVEF than the HVSD increase group. These results indicate that spastic angina pectoris patients show various responses to HV stress. The HVSD increase group might have additional myocardial ischemia due to regional coronary spasm. In contrast, in the HVSD decrease group severe LV dysfunction or diffuse wall motion abnormality might have been generated, and this caused a reduction in the SD value. Phase analysis would therefore add new information regarding electrocardiographically silent myocardial ischemia due to coronary spasm, and HV stress might increase sensitivity for the detection of abnormalities in quantitative phase analysis, especially in VspAP patients.

Adult↗
PubMed1985

Different susceptibility to myocardial ischemia provoked by hyperventilation and cold pressor test in exertional and variant angina pectoris.

Coronary constriction at the site of atherosclerotic stenoses has been suggested to play an important role in modulating the frequency of symptoms in patients with exertional angina. To investigate whether stimuli triggering coronary constriction have similar effects in patients with exertional and variant angina, responses to hyperventilation (HV) and cold pressor test (CPT) were evaluated. Twenty patients with chronic exertional angina, positive exercise test results and coronary heart disease were compared with 14 patients with variant angina and ST-segment elevation during an ergonovine test. In patients with exertional angina, the CPT produced diagnostic ST-segment depression in 6 of 20 patients (30%) at levels of rate-pressure product much lower than those during the exercise test; all patients had low effort tolerance and severe coronary artery disease. HV produced diagnostic ST-segment depression in only 1 of 20 patients (5%) (p less than 0.05 compared to that with CPT). Conversely, in patients with variant angina, HV produced ST-segment elevation in 11 of 14 patients (78%) and CPT produced elevation in only 2 of 14 (14%) (p less than 0.01). Thus, coronary constriction can provoke myocardial ischemia not only in patients with variant angina but also in some patients with exertional angina. Furthermore, the 2 groups of patients have a different susceptibility to stimuli known to produce coronary constriction.

Adult↗
PubMed1992

Exercise hyperventilation chronic congestive heart failure, and its relation to functional capacity and hemodynamics.

The ventilatory response to exercise was evaluated in 26 normal sedentary men and 68 patients with chronic heart failure using the slope of the relation between minute ventilation (VE) and carbon dioxide production (VCO2). All subjects underwent maximal upright bicycle cardiopulmonary exercise testing; 33 patients also underwent right-sided cardiac catheterization. The slope of VE/VCO2 was calculated by linear regression analysis using data from all the exercise tests and the first 60% of exercise duration; a high correlation was seen between these results (r = 0.83; p less than 0.001). The slope of VE/VCO2 was significantly, though weakly, related to peak exercise work load, oxygen consumption and ventilatory threshold (r = -0.49, -0.56 and -0.49, respectively), several peak exercise hemodynamic parameters and peak exercise dead space/tidal volume ratio (r = 0.70). With use of multivariate analysis, the only independent determinants of the slope were peak exercise dead space/tidal volume ratio and cardiac index. Thus, in patients with heart failure, exercise hyperventilation can contribute to the impairment of functional capacity and can be considered a compensatory response to abnormal hemodynamics and lung blood distribution in order to keep blood gas concentrations normal.

Cardiac Catheterization↗
PubMed1992

Hyperventilation syndrome and the assessment of treatment for functional cardiac symptoms.

Three methods of breathing retraining (guided breathing retraining, guided breathing retraining with physiologic monitoring of thoracic and abdominal movement plus peripheral temperature, and guided breathing retraining with physiologic monitoring of thoracic and abdominal movement, peripheral temperature and end-tidal carbon dioxide) were compared with a no-treatment control group to determine the effectiveness of breathing retraining on modifying respiratory physiology and reducing functional cardiac symptoms in subjects with signs associated with hyperventilation syndrome. Of 41 subjects studied, 16 were diagnosed with mitral valve prolapse. Results demonstrated that all 3 methods of breathing retraining were equally effective in modifying respiratory physiology and reducing the frequency of functional cardiac symptoms. Results determined that respiratory rate and subject's perception that training had generalized were the best predictors of treatment success. Furthermore, it was found that subjects with mitral valve prolapse responded as well to treatment as did those without prolapse.

Adult↗
PubMed1991

The efficacy of breathing retraining and the centrality of hyperventilation in panic disorder: a reinterpretation of experimental findings.

The present paper addresses de Ruiter, Rijken, Garssen, and Kraaimaat's (Behaviour Research and Therapy, 27, 647-655, 1989) interpretation of data pertaining to the efficacy of breathing retraining in the treatment of panic disorder. The proffered reinterpretation of these data makes it clear that breathing retraining led to a significant reduction in the frequency of panic attacks. These findings thus lend additional support to the central role of hyperventilation in primary panic attacks.

Anxiety Disorders↗
PubMed1985

Efficacy of Nijmegen Questionnaire in recognition of the hyperventilation syndrome.

The pattern of complaints of patients with the hyperventilation syndrome (HVS) was studied on the basis of the Nijmegen HVS Questionnaire (van Doorn, Colla, Folgering). This list was completed by 75 patients with the clinical diagnosis HVS. Non-metric principal components analysis (NMPCA) showed that the structure was three-dimensional, the dimensions being labelled: Shortness of breath (HVS-1), Peripheral tetany (HVS-II), Central tetany (HVS-III). The questionnaire's differentiating ability was investigated by comparing HVS patients with non-HVS persons (80 persons employed in health care). All three components had an unequivocally high ability to differentiate between HVS and non-HVS. Application of linear analysis of discriminance to HVS-I, HVS-II and HVS-III together yielded 93% correct classifications. Statistical double cross-validation resulted in 90 and 94% correct classifications. The sensitivity of the Nijmegen Questionnaire in relation to the clinical diagnosis was 91% and the specificity 95%. It is concluded that the questionnaire is suitable as a screening instrument for early detection of HVS, and also as an aid in diagnosis and therapy planning.

Adult↗
PubMed1981

Dynamics of changes in the acid-base equilibrium of arterial blood and the cerebrospinal fluid in conditions of natural hyperventilation and apnoea.

From investigations on 252 patients the dynamics of changes in the acid-base equilibrium of the cerebrospinal fluid (CSF) and arterial blood were assessed, in conditions of natural changes in breathing rhythm. Gasometric examinations were made several times during natural hyperventilation lasting 4, 5 or 6 min, depending on the examined group, and after apnoea lasting 30 s. The results indicate a specific autonomy of the CSF with respect to the blood, relating to such indices as pH, pCO2 and pO2, in conditions of natural changes in breathing rhythm. This is manifested to varying degrees by differentiation in time of occurrence, depth and direction of changes in the acid-base equilibrium indices in the CSF, relative to the corresponding indices in the blood. On this basis a number of groups were distinguished from among the patients investigated, in whom the clinical state appeared to correlate, to a certain degree, with the degree and direction of changes in the CSF. It is postulated that his specific autonomy of the CSF may be due to the action of regulatory mechanisms at the level of the nerve tissue.

Acid-Base Equilibrium↗
PubMed1995

Vestibular hyperreactivity and hyperventilation after whiplash injury.

Vestibular, oculomotor and respiratory tests were performed on 32 patients after whiplash injury caused by a rear-end car collision. Oculomotor functions were generally normal. The cervico-ocular reflex was usually absent or displayed the low gain typical of normal subjects. There was no nystagmic response to static neck torsion. The vestibulo-ocular reflex showed vestibular hyperreactivity (VH) in a significantly large number of cases (n = 17; 53%). The respiratory test results were also typical of the hyperventilation syndrome (HVS) in a significantly large number of cases (n = 12; 38%). The findings of VH and the HVS were not significantly correlated within the patient group. However, the combination of VH and the HVS occurred significantly more often (n = 7; 22%) than could be accounted for by combined false positivity. Most of the significant findings were due to high relative frequencies in the women: 11 out of the 17 women (65%) showed VH, 8 (47%) had the HVS and 5 (29%) showed a combination of VH and the HVS. The findings were not correlated with the patient's age or the time interval between the accident and the examination. VH might have been the result of plastic adaptation to limited head mobility secondary to neck pain. Behavioural and emotional distress might offer alternative explanations for both VH and the HVS.

Accidents, Traffic↗
PubMed1983

Changes in rib cage shape during quiet breathing, hyperventilation and single inspirations.

We measured the relative changes in upper and lower rib cage volume (delta RCU and delta RCL, respectively) using an induction coil plethysmograph (Respitrace) in seven normal seated subjects during relaxed passive expiration from total lung capacity, during quiet breathing, rapid breathing at 60 breaths/min (RB), during exercise-induced hyperventilation (EH) and during single fast inspirations. The plot of the RCU vs RCL was slightly curvilinear during relaxation from total lung capacity in all subjects. However, the inferred changes in rib cage shape were similar during RB and EH to those observed during quiet breathing and the relaxation manoeuvres. In contrast, single rapid inspirations were associated with marked and variable changes in rib cage shape, being most prominent in the first part of the breath. Our results suggest that during cyclic breathing respiratory muscle activity is so co-ordinated that the pattern of rib cage shape change is similar to that observed during relaxation. In contrast, single rapid inspirations are associated with markedly different and variable shape changes of the rib cage, presumably due to different patterns of inspiratory muscle recruitment. The results are consistent with the observation that during tidal breathing regional ventilation distribution is flow independent.

Adult↗