Eicosanoids modulate hyperpnea-induced late phase airway obstruction and hyperreactivity in dogs

A canine model of exercise-induced asthma was used to test the hypothesis that the development of a late phase response to hyperventilation depends on the acute production of pro-inflammatory mediators. Peripheral airway resistance, reactivity to hypocapnia and aerosol histamine, and bronchoalveolar lavage fluid (BALF) cell and eicosanoid content were measured in dogs approximately 5 h after dry air challenge (DAC). DAC resulted in late phase obstruction, hyperreactivity to histamine, and neutrophilic inflammation. Both cyclooxygenase and lipoxygenase inhibitors administered in separate experiments attenuated the late phase airway obstruction and hyperreactivity to histamine. Neither drug affected the late phase inflammation nor the concentrations of eicosanoids in the BALF obtained 5 h after DAC. This study confirms that hyperventilation of peripheral airways with unconditioned air causes late phase neutrophilia, airway obstruction, and hyperreactivity. The late phase changes in airway mechanics are related to the hyperventilation-induced release of both prostaglandins and leukotrienes, and appear to be independent of the late phase infiltration of inflammatory cells.

Hypoxia following voluntary hyperventilation during exercise in man

The importance of carbon dioxide in the control of ventilation during exercise was tested by emptying CO2 stores by voluntary hyperventilation. Healthy subjects were studied after 3 min hyperventilation down to an end-tidal PCO2 of about 20 mmHg on a background of steady exercise at 75 W. Control runs were performed when the hyperventilation was made isocapnic by the addition of CO2. Following hypocapnic hyperventilation, there was a period when ventilation fell below control and this was accompanied by a fall in end-tidal PO2 (minimum 48 mmHg) and oximeter reading (minimum 73%). Ventilation rapidly returned to baseline following isocapnic hyperventilation and hypoxia was not seen. A mathematical simulation suggested that brain PCO2 recovered more slowly than arterial PCO2 and that at the times that ventilation was depressed central chemoreceptor PCO2 would have been low. We conclude that CO2 provides a crucial drive for maintaining adequate ventilation during steady exercise and that the central chemoreceptor may be involved.

Hypoxaemia in patients with hyperventilation syndrome

We assessed 12 patients with hyperventilation syndrome (HVS) who had experienced hypoxaemia (PaO2 < 60 Torr or SaO2 < 90%) despite the lack of any other organic disease and variability in their blood gas data. Hypoxic and hypercapnic ventilatory responses were measured in nine. Eight of the 12 patients had been referred from other hospitals to our institution for hypoxaemia of unknown origin. Mean PaO2 (n = 12) at rest (non-attack stage) was 87.3 +/- 7.5 Torr (mean +/- SD). Their (n = 9) hypoxic (-0.53 +/- 0.32 l/min/%; range 0.12-0.99) and hypercapnic (2.01 +/- 0.76 l/min/Torr; range 0.69-3.17) ventilatory responses were both within the normal range in our laboratory. The patients with HVS had variable blood gas data, and some of them also exhibited hypercapnia (PaCO2 > 45 Torr). Clinicians who treat patients with HVS should be aware of the possibility of hypoxaemia, even when ventilatory responses are normal. Physicians should also consider HVS as a diagnosis when treating patients with hypoxaemia of unknown origin.

The psychosomatic theory of bronchial asthma

The author discusses the development of the psychosomatic asthma theory as a paradigm of theory formation in psychomatic medicine. The first formulation of the theory was based on clinical and psychiatric observations. It was tested by psychological, physiological and experimental methods and as a result was reformulated and extended. In its present form it regards asthmatic breathing as a reaction of a predisposed personality structure (partly hereditary, partly acquired during a youth situation in which overprotection by a domineering parent played a large role), to an ambivalent conflict with a key figure. The resulting frustration is not acted out by aggressive, flight, or depressive behaviour, but inhibited; thereby the motoric and verbal discharges are displaced into (substituted by) a respiratory behaviour pattern, which is characterised by an abnormally forceful contraction of the abdominal muscles during the expiration. The resulting high intraabdominal pressure is transmitted into the thorax where it pushes the posterior membranaceous wall of the trachea and large bronchi forward into the lumen and thus produces a long stretched obstruction of the large airways. The passage of the air through the compressed large air passages under high pressure and low velocity is the mechanism which causes the typical wheeze and the other manifestations of the asthmatic airway obstruction. A hypothesis is suggested for the ways in which this psychoneurogenic respiratory behaviour contributes to the so-called bronchial hyper-reactivity and the secondary development of allergies.

Refractory period during provocation with eucapnic hyperventilation and methacholine

Eucapnic voluntary hyperventilation (EVH) and methacholine inhalation challenge (MIC) both cause bronchoconstriction in asthmatics. A refractory period, or time when the response to bronchoprovocation in a series of challenges is diminished, has been found after hyperventilation or exercise but not after MIC. We investigated whether EVH or MIC blunted the response to the other test. Sixteen asthmatics were studied on 2 d, taking both tests each day. They were randomized to either EVH or MIC first on Day 1, then the opposite order on Day 2, 6 to 14 d apart. After EVH as a first test, the mean decline in FEV1 from baseline was 18.66 +/- 4.76% (mean +/- SEM), but when EVH followed MIC, the response to EVH was reduced by 30%, to a decline in FEV1 of only 13.02 +/- 3.75% (p = 0.0026). During MIC, the mean provocation dose to cause 20% decrease in FEV1 (PD20) given as the initial challenge was 54.77 +/- 21.60 breath units, compared with 46.94 +/- 19.55 breath units when MIC followed EVH (p = 0.54). However, the subset of patients most sensitive to methacholine (PD20 < 0.1 breath unit) had changes suggestive of a refractory period after EVH, with a mean increase in the PD20 from 0.06 +/- 0.01 to 3.35 +/- 1.43 (p = 0.069). Our data show that MIC attenuates the response to subsequent challenge with EVH. Conversely, EVH may only affect subsequent MIC in those most sensitive to methacholine.

Prevention with and without the use of medications for exercise-induced asthma

Exercise-induced asthma or bronchospasm occurs in approximately 12% of the population. It can be prevented with proper techniques of exercise and environmental exposures and with medication. Exercise techniques include timing of exercise to less than 5-min interludes and continued repeat exercise every hour. Exercising to less than full tolerance may avoid the onset of exercise-induced asthma. In some individuals exercise in warm, humidified air is less asthmogenic than in dry, cold air. Medications that are effective and safe include bronchodilators such as theophylline and beta-agonists and prevention with cromolyn sodium in the atopic or sulfite exposed individual.

Understanding dizziness. How to decipher this nonspecific symptom

Dizziness is a common but often nonspecific symptom. Through careful history taking and physical examination, primary care physicians can usually determine the type of sensation (vertigo or light-headedness) and its source. Although most causes of dizziness are benign, disorders of the central nervous system tend to be ominous and require immediate referral to a specialist.

Asystole with syncope secondary to hyperventilation in three young athletes

We describe three athletes who had syncope after (case 1) or during (cases 2, 3) hyperventilation. During the episode, ECG showed prolonged sinus arrest. Clinical data and noninvasive investigations were normal and the phenomenon was not reproducible. Electrophysiological study after autonomic blockade allowed a prolonged intrinsic heart rate in case 1, and abnormal corrected sinus node recovery time in cases 1 and 2. During follow-up, symptomatic sinus arrest provoked by deep inspiration occurred in case 3. These cases document prolonged asystole of unknown etiology, secondary to hyperventilation, and probably caused by different vagally-mediated mechanisms.

Clinical and metabolic features of overdosage with Amesec

A 23-year-old woman ingested 2g. amylobarbitone, 10.4g. aminophylline and 2g. ephedrine. She was deeply unconscious, hypothermic, and went on to have supraventricular and ventricular dysrhythmias, convulsions and haematemesis. During the last convulsion she aspirated vomitus and died. The peak plasma concentration of amylobarbitone was 19mg. per l. and those of ephedrine and theophylline were 13 times higher than accepted therapeutic levels. During the course of the poisoning marked hypokalaemia (1.8mmol./l.) and hyperinsulinaemia (greater than 240mU./l.) were found in conjunction with mild hyperglycaemia (9.6mmol./l.) and elevation of free fatty acid levels (1860mumol./l.). The mechanism of these changes is discussed.

Heparin inhibits hyperventilation-induced late-phase hyperreactivity in dogs

Inhalation of heparin attenuates hyperventilation-induced bronchoconstriction in humans and dogs. The purpose of this study was to determine whether heparin inhibits the late-phase response to hyperventilation, which is characterized by increased peripheral airway resistance (RP), eicosanoid mediator production, neutrophilic/ eosinophilic inflammation, and airway hyperreactivity (AHR) at 5 h after dry air challenge (DAC). Fiberoptic bronchoscopy was used to record RP and airway reactivity (DeltaRP) to aerosol and intravenous histamine before and 5 h after DAC. Bronchoalveolar lavage fluid (BALF) cells and eicosanoid mediators were also measured approximately 5 h after DAC. DAC of vehicle-treated bronchi resulted in late-phase airway obstruction (approximately 120% increase over baseline RP), inflammation, increased BALF concentrations of leukotriene (LT) C(4), LTD(4), and LTE(4) and prostaglandin (PG)D(2), and AHR. Pretreatment with aerosolized heparin attenuated late-phase airway obstruction by approximately 50%, inhibited eosinophil infiltration, reduced BALF concentrations of LTC(4), LTD(4), and LTE(4) and PGD(2), and abolished AHR. We conclude that heparin inhibits hyperventilation-induced late-phase changes in peripheral airway function, and does so in part via the inhibition of eosinophil migration and eicosanoid mediator production and release.

Flunarizine treatment in dizzy patients with vestibular hyperreactivity and hyperventilation

Flunarizine (10 mg/day) was given in an open pilot study to 14 patients with the primary complaint of dizziness, who showed vestibular hyperreactivity in the velocity step (VS) test and were proven to have a hyperventilation syndrome (HVS) without any other disease. The VS test was repeated after 4-6 weeks of treatment. Twelve of these HVS patients reported alleviation of dizziness. Objective evaluation of the results of treatment was attempted by defining suitable response parameters and comparing their values to those obtained in a control group of 14 healthy volunteers tested twice with the same interval. A significant decrease in right-left asymmetry in the VS responses of the patients on drug was found.

Cardio-respiratory measures following isocapnic voluntary hyperventilation

In some individuals, breathing is greater than at rest following voluntary hyperventilation. Most previous investigations have employed short hyperventilation periods; here we examine the time course of cardio-respiratory measures before, during, and after a 5-min voluntary hyperventilation, maintaining isocapnia throughout. We examined the possible co-involvement of the cardiovascular system; hypothesising that post-hyperventilation hyperpnoea results from an increase in autonomic arousal. In four subjects (two males, two females) of 18 (nine males, nine females) we observed a post-hyperventilation hyperpnoea, characterised by a slow decline of ventilation toward resting levels with a time constant of 109.0 +/- 16.1s. By contrast, heart rate, and systolic and diastolic blood pressure were unchanged from rest during and after voluntary hyperventilation for all subjects. We concluded that males and females were equally likely to exhibit post-hyperventilation hyperpnoea, and suggest that they may be characterised by an increased resting heart rate and the choice of breathing frequency to increase ventilation during the voluntary hyperventilation. We further concluded that post-hyperventilation hyperpnoea is rare, but when present is a strong and lasting phenomenon, and that it is not the result of an increased autonomic arousal.

C-reactive protein elevation predicts in-hospital deterioration after aneurysmal subarachnoid hemorrhage: a retrospective observational study

Background

There is increasing evidence that inflammation plays a role in the pathogenesis of aneurysmal subarachnoid hemorrhage (aSAH) and in the development of delayed cerebral ischemia (DCI). However, the assessment and interpretation of classically defined inflammatory parameters is difficult in aSAH patients. The objective of this study was to investigate the relationship between easily assessable findings (hyperventilation, fever, white blood cell count (WBC), and C-reactive protein (CRP)) and the occurrence of DCI and unfavorable neurological outcome at discharge in aSAH patients.

Methods

Retrospective analysis of prospectively collected data from a single center cohort. We evaluated the potential of clinical signs of inflammation (hyperventilation, fever) and simple inflammatory laboratory parameters CRP and WBC to predict unfavorable outcomes at discharge and DCI in a multivariate analysis. A cutoff value for CRP was calculated by Youden’s J statistic. Outcome was measured using the modified Rankin score at discharge, with an unfavorable outcome defined as modified Rankin scale (mRS) > 3.

Results

We included 97 consecutive aSAH patients (63 females, 34 males, mean age 58 years) in the analysis. Twenty-one (22%) had major disability or died by the time of hospital discharge. Among inflammatory parameters, CRP over 100 mg/dl on day 2 was an independent predictor for worse neurological outcome at discharge. The average C-reactive protein level in the first 14 days was higher in patients with a worse neurological outcome (96.6, SD 48.3 vs 56.3 mg/dl, SD 28.6) in the first 14 days after aSAH. C-reactive protein on day 2 was an indicator of worse neurological outcome. No inflammatory parameter was an independent predictor of DCI. After multivariate adjustment, DCI, increased age, and more than 1 day of mechanical ventilation were significant predictors of worse neurological outcome.

Conclusions

Early elevated CRP levels were a significant predictor of worse neurological outcome at hospital discharge and may be a useful marker of later deterioration in aSAH.

Hyperventilation and amplified blood pressure response: is there a link?

Based on prior studies, the hypothesis that hyperventilation (HV) may have a pressor effect and play a causal role in hypertension has been suggested. The objective of this study was to correlate HV with blood pressure (BP)-change during a postural challenge. Consecutive subjects referred for evaluation of syncope, dizziness, chronic fatigue syndrome (CFS), fibromyalgia, or non-CFS fatigue were assessed with a 10-min supine 30-min head-up tilt test combined with capnography. We selected for analysis the records of patients aged 17-70 years, not taking vasoactive medications, having sitting systolic BP (SBP) < 140 mmHg, sitting diastolic BP (DBP) < 90 mmHg, and who completed 30 min of tilt. HV was diagnosed when end-tidal pressure of CO2 < 30 mmHg was recorded consecutively for > or = 10 min. Postural hypertension (PHT) was diagnosed when DBP on tilt > or = 90 mmHg was recorded consecutively for > or = 10 min. DBP-change was computed as (median DBP on tilt) -(median DBP supine). PHT and DBP-change were correlated with HV. A total of 320 patient charts were reviewed. PHT was present in 30 cases. The mean DBP-change in patients with PHT was +9.9 mmHg (s.d. 5.8), with three patients manifesting HV. Of the remaining 290 patients, 56 had HV, their mean DBP-change was -0.3 mmHg (s.d. 7.2). The other 234 patients without HV had a mean DBP-change +0.95 mmHg (s.d. 5.7), comparable to the DBP-change in patients with HV. In, conclusion, posturally induced HV was not associated with an increase in BP, nor was PHT associated with HV, except in a small minority of cases.

[A case of coronary vasospasm treated with stent placement]

We report about a 49 year old woman with repeated chest pain at rest. During hyperventilation significant ST-segment elevation in leads V1-V5 appeared. Bicycle stress test did not provoke any ECG changes. Coronary angiography showed a significant stenosis of the left anterior descending coronary artery. Successful balloon angioplasty followed by stent implantation was performed. After an uneventful course of twelve months, hyperventilation could provoke neither chest pain nor ECG changes again without any antispastic medical treatment. Impact of fixed atherosclerotic lesions for the occurrence of coronary vasospasm, usefulness of hyperventilation as a non-invasive provocation test and therapy are discussed.

Non Q-wave myocardial infarction following hyperventilation test

We report a case of acute myocardial infarction following a hyperventilation test performed at coronary angiography. The potential pathophysiological mechanisms and clinical implications are discussed.

Sympathetic rhythms during hyperventilation-induced apnea

The effect of hyperventilation-induced apnea on the respiratory rhythmicity of sympathetic nerve activity was determined using spectral analysis of sympathetic nerve frequencies. Left phrenic, external intercostal, and inferior cardiac sympathetic nerves were recorded in alpha-chloralose-anesthetized, vagotomized, paralyzed, artificially ventilated cats. The respiratory modulation of sympathetic activity during normoventilation was indicated by spectral peaks of sympathetic activity coinciding with respiratory frequencies determined from the phrenic nerve activity of each cat. The spectral peaks of respiratory-related sympathetic activity disappeared during hyperventilation-induced apnea and then reappeared with the return of phrenic nerve activity when normoventilation was resumed. Although sympathetic activity lost its respiratory modulation during hyperventilation, baroreceptor-mediated bilateral carotid occlusion responses and electrocardiogram (R wave)-triggered computer summation of cardiac related sympathetic activity were unaffected. Hence central respiratory inputs on sympathetic pathways in the central nervous system best explain the origin of respiratory-related sympathetic rhythms. Independent sympathetic rhythms of apparent nonrespiratory origin may be due to artificial ventilator influences, baroreflex-autonomic oscillation loops, or Mayer waves.