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PubMed1988

Effect of passive hyperventilation on seizure duration in patients undergoing electroconvulsive therapy.

The influence of end-expired carbon dioxide concentration (E'CO2) on seizure duration was studied in 30 depressed patients undergoing electroconvulsive therapy (ECT) on three separate consecutive occasions. Unpremedicated patients breathed 100% oxygen before the induction of anaesthesia with methohexitone and the provision of partial neuromuscular blockade with suxamethonium. They then received no further ventilation, 10 breaths, or 20 breaths of hyperventilation with 100% oxygen from a non-rebreathing system with a high fresh gas flow. Transcutaneous oxyhaemoglobin saturation (SaO2) was monitored continuously and E'CO2 was measured before and after the seizure. Observation of an isolated forearm was used to time the seizure duration. SaO2 remained greater than 90% in all patients. Passive hyperventilation with 20 breaths significantly reduced E'CO2 and prolonged seizure duration. E'CO2 before the seizure and change in E'CO2 during the seizure did not correlate significantly with seizure duration.

Adult↗

PubMed1994

Hyperventilation-induced unconsciousness during labour.

We report the development of unconsciousness caused by hyperventilation in an otherwise healthy woman in labour. Extradural analgesia resulted in restoration of full consciousness and normal respiratory state. The pathophysiology of hyperventilation and aspects of respiratory physiology in pregnancy are discussed.

Adult↗

PubMed1983

Non-pharmacological provocation of coronary vasospasm. Experience with prolonged hyperventilation in the coronary care unit.

Results are reported of prolonged hyperventilation as a provocation test in a consecutive series of six patients with a clinical diagnosis of Prinzmetal's variant angina (PVA) and a control series of eight patients. All the patients with PVA responded to the hyperventilation test (HVT) with significant ST deviation (five with elevation, one with depression) and typical anginal pain. None of the eight patients in the control series were positive responders. Sustained attacks of serious arrhythmias were recorded in one patient with PVA. Sensitivity to HVT showed circadian variations; the tests were positive only in the early morning at the time of the reported spontaneous attacks. Beta blockade changed a negative HVT response to a positive one in one case. Treatment with calcium channel blockers suppressed the positive response in all patients. After cessation of long-term treatment with calcium channel blockers, HVT suggested spontaneous remission in spasm tendency in three out of four patients with PVA from a previous series of 12 patients. It is concluded that HVT as a non-pharmacological provocation test may prove an effective and comparatively safe procedure with potential for controlling the efficacy of drug treatment and confirming spontaneous remission of vasospastic disease. Optimal facilities for resuscitation should be at hand during the test due to risk of provoking life-threatening arrhythmias.

Adult↗

PubMed1999

Transient hyperdynamic response associated with controlled hypocapneic hyperventilation during sevoflurane-nitrous oxide mask induction in adults.

UNLABELLED: We assessed hemodynamic variables during sevoflurane face mask anesthetic induction in female ASA physical status I or II patients. Anesthesia was induced with a single-breath inhalation method with 8% sevoflurane in 50% nitrous oxide in oxygen. Thirty patients were randomized either to breathe spontaneously (SB group, n = 15) or to receive controlled ventilation (CV group, n = 15) for 6 min after the loss of consciousness. Noninvasive blood pressure and heart rate (HR) were recorded at 1-min intervals. Mean +/- SD HR increased from 83+/-18 to 112+/-24 bpm at 4 min in the CV group (P < 0.001 between groups and within group compared with baseline). Mean arterial pressure increased from 97+/-9 to 106+/-26 mm Hg at 4 min in the CV group, which was significantly higher than that in the SB group (P < 0.01). In the SB group, mean arterial pressure decreased significantly, from 96+/-8 to 78+/-13 mmHg, at 6 min (P < 0.001), and HR remained unchanged. Therefore, hyperventilation should be avoided during the induction of sevoflurane anesthesia via a mask. IMPLICATIONS: In this randomized, prospective study, we found that controlled hypocapneic hyperventilation delivered manually during sevoflurane/ N2O/O2 mask induction was associated with a significant transient hyperdynamic response. This kind of hemodynamic arousal can be detrimental to many patients and can be avoided by conducting sevoflurane mask induction with unassisted spontaneous breathing.

Adult↗

PubMed1979

Hyperventilation in tricyclic antidepressant poisoning.

A patient with severe tricyclic antidepressant poisoning who showed recurrent ventricular fibrillation and wide QRS complexes on the ECG, failed to respond to intravenous physostigmine and lidocaine. Deliberate artificial hyperventilation was immediately effective in preventing further arrhythmia and in decreasing the width of the QRS complexes. Hyperventilation, a neglected treatment, may be immediately effective in the treatment of severe tricyclic antidepressant poisoning.

Adult↗

PubMed1997

Effect of hyperventilation on regional cerebral blood flow in head-injured children.

OBJECTIVES: To study cerebral blood flow and cerebral oxygen consumption in severe head-injured children and also to assess the effect of hyperventilation on regional cerebral blood flow. DESIGN: Prospective cohort study. SETTING: Pediatric intensive care unit at a tertiary-level university children's hospital. PATIENTS: Twenty-three children with isolated severe brain injury, whose admission Glasgow Coma Scores were <8. INTERVENTIONS: PaCO2 was adjusted by altering minute ventilation. Cerebral metabolic measurements were made at three levels of PaCO2 (>35, 25 to 35, and <25 torr [>4.7, 3.3 to 4.7, and <3.3 kPa]) after allowing 15 mins for equilibrium. MEASUREMENTS AND MAIN RESULTS: Thirty-eight studies (each study consisting of three sets of measurements at different levels of PaCO2) were performed on 23 patients. At each level of PaCO2, the following measurements were made: xenon-enhanced computed tomography scans; cerebral blood flow; intracranial pressure; jugular venous bulb oxygen saturation; mean arterial pressure; and arterial oxygen saturation. Derived variables included: cerebral oxygen consumption; cerebral perfusion pressure; and oxygen extraction ratio. Cerebral blood flow decreased below normal after head injury (mean 49.6 +/- 14.6 mL/min/100 g). Cerebral oxygen consumption decreased out of proportion to the decrease in cerebral blood flow; cerebral oxygen consumption was only a third of the normal range (mean 1.02 +/- 0.59 mL/min/100 g). Neither cerebral blood flow nor cerebral oxygen consumption showed any relationship to time after injury, Glasgow Coma Score at the time of presentation, or intracranial pressure. The frequency of one or more regions of ischemia (defined as cerebral blood flow of <18 mL/min/100 g) was 28.9% during normocapnia. This value increased to 73.1% for PaCO2 at <25 torr. CONCLUSIONS: Severe head injury in children produced a modest decrease in cerebral blood flow but a much larger decrease in cerebral oxygen consumption. Absolute hyperemia was uncommon at any time, but measured cerebral blood flow rates were still above the metabolic requirements of most children. The clear relationship between the frequency of cerebral ischemia and hypocarbia, combined with the rarity of hyperemia, suggests that hyperventilation should be used with caution and monitored carefully in children with severe head injuries.

Adolescent↗

PubMed1971

Effect of disodium cromoglycate on exacerbations of asthma produced by hyperventilation.

The prophylactic inhalation of disodium cromoglycate lessens the exacerbations which occur in some asthmatic patients after voluntary hyperventilation. Reasons are given for considering this to be a possible mechanism for certain types of emotional exacerbation of the disease and for disodium cromoglycate giving sypmtomatic relief of asthma disproportionate to the improvement in routine measurements of ventilatory capacity. It is suggested that one clinical indication for giving disodium cromoglycate is to observe whether a fall in FEV(1) occurs after two minutes hyperventilation.

Adolescent↗

PubMed1973

Evaluation of hyperventilation in treatment of head injuries.

Reduction of the partial pressure of carbon dioxide in the arterial blood by mechanical hyperventilation (Pco(2) 25-30 mm Hg; Po(2) 100-150 mm Hg) may be beneficial in cases of severe head injury. To evaluate its efficacy and establish prognostic guidelines intracranial pressure, radiocirculograms, and cerebrospinal fluid (C.S.F.) lactate levels were studied in 31 patients. In survivors intracranial pressure fell and cerebral blood flow improved with treatment. A C.S.F. lactate greater than 55 mg/100 ml was associated with a poor prognosis. Selection of patients was based on clinical judgement, and adults with signs of extensive brain damage were excluded. The importance of an adequate airway and resuscitation is stressed before a final decision is made. The object of treatment is to improve the quality of survival and the criteria measured may aid in the distinction between patients with a potential for good recovery and those capable only of a vegetative existence. Many associated factors as well as hypocapnia reduce intracranial pressure, and these are discussed. We believe that hyperventilation may improve some head injuries, and further study is indicated.

Adolescent↗

PubMed1981

Hyperventilation or exercise to induce asthma?

Bronchoconstriction was induced in asthmatic patients by means of isocapnic hyperventilation with dry air. Responses both within a day and between days did not differ significantly and corresponded closely with those observed after exercise. The mean fall in forced expiratory volume in one second (FEV1) observed with both techniques was equivalent to 36%. Isocapnic hyperventilation with dry air, as used in this study, was a potent stimulus and provoked a reproducible response. The method was physically less demanding than exercise and was more acceptable to patients.

Adolescent↗

PubMed1977

Effects of exercise and eucapnic hyperventilation on bronchial clearance in man.

The effects of exercise and eucapnic hyperventilation on bronchial clearance were assessed in 10 healthy nonsmoking adults. A 99mTc-albumin aerosol was inhaled as a bolus in late inspiration under controlled conditions to produce deposition primarily in large airways. Lung retention of radioactivity was quantified using a gamma camera and subsequent computer analysis. Compared with quiet breathing (control), exercise significantly speeded clearance (P less than 0.05). Resting eucapnic hyperventilation at levels similar to those achieved during exercise produced less speeding. Compared to control conditions these changes may be brought about by a) mechanical effect of increased lung movement, and b) effects on the autonomic nervous system, mediated via the parasympathetic pathway producing stimulation of airway mucus glands and/or sympathetic stimulation of cilia due to exercise-induced catecholamine release.

Adult↗

PubMed1995

Effects of high and low anxiety provoking instructions on the responses to the hyperventilation provocation test.

This study examined the effect of high and low anxiety provoking instructions in subjects submitted to a Hyperventilation Provocation Test (HVPT). Subjects were 43 out-patients referred to our clinic for a diagnostic examination of Hyperventilation Syndrome (HVS). Results showed that anxiety levels were affected by the instruction manipulation, but the magnitude of this effect was less than expected and the instruction manipulation had no effect on intensity arid type of reproduced symptoms, nor on symptom recognition. Subjects who met Diagnostic and Statistical manual of Mental Disorders (3rd ed., rev,; American Psychiatric Association, 1987) criteria for Panic Disorder (PD) were not more responsive to the instruction manipulation than non-PD patients. It is argued that the small effect of the manipulation is probably not due to the solidity of the HVPT but to the pervasiveness of pretest cognitions and expectations. In line with this, the report of HVS symptoms appeared highly related to psychological trait measures like anxiety, fear of bodily sensations, and a general tendency to report somatic symptoms.

Journal Article↗

PubMed1984

Use of high frequency jet ventilation during mechanical hyperventilation to reduce intracranial pressure in patients with multiple organ system injury.

Eleven patients with multiple organ system injury, including significant closed head injury, all required positive end-expiratory pressure (PEEP) for treatment of their pulmonary pathological condition. Additionally, the need for intracranial pressure (ICP) monitoring had previously been established on clinical evaluation by the Neurosurgery Service. Seven of the 11 patients met the criteria for invasive hemodynamic monitoring. Hemodynamic monitoring data are supplied for these 7 patients. All patients, after the initial institution of conventional means of hyperventilation, were transitioned to high frequency jet ventilation (HFJV) to evaluate the effects of HFJV during mechanical hyperventilation. There was a statistically significant decrease in ICP (mean decrease of 7.2 mm Hg). There was also a statistically significant fall in PaO2 from 131 to 101 torr. This was not associated with an appreciable decrease in oxygen delivery. There was no change in cardiac output or intrapulmonary shunt fraction. It is concluded that successful control of ICP was possible in all cases without impairment of cardiac output, oxygen delivery, or cerebral perfusion pressure, even when the pulmonary abnormality required the use of PEEP.

Adolescent↗

PubMed1986

Comparison of isocapnic hyperventilation and walking exercise training at home in pulmonary rehabilitation.

Eighteen COPD patients enrolled in a comprehensive, multidisciplinary pulmonary rehabilitation program were randomly assigned to perform either: 1) walking, or 2) ventilatory muscle exercise training (VMT) using a prototype, portable device for isocapnic hyperventilation training. Both groups performed exercise training at home. Twelve patients completed the study and follow-up evaluation (five VMT, seven walkers). Pulmonary function did not change in either group. For the VMT patients, there were modest increases in ventilatory muscle endurance and exercise performance. VO2max and VEmax increased significantly. For the walkers, only walking endurance time increased significantly. These results indicate that isocapnic hyperventilation exercise training can be performed successfully by COPD patients in an unsupervised home setting and can lead to improvement in both ventilatory muscle endurance and exercise performance. Walking exercise training did not improve ventilatory muscle endurance.

Aged↗

PubMed1999

Effects of indomethacin and hyperventilation on cerebral hemodynamics and oxygenation in newborn piglets.

We investigated the effect of indomethacin (INDO) and hyperventilation (HV) on cerebral hemodynamics and oxygenation in newborn piglets using near-infrared spectroscopy (NIRS). A total of 10 piglets aged 7-10 days were divided into 2 groups. INDO (Experimental group; 0.2 mg/kg i.v.) or saline (Control group) was administered after steady state, then each group was hyperventilated (pCO2; 20 mm Hg). Cerebral oxyhemoglobin concentrations (HbO2) significantly decreased immediately after INDO administration compared to controls (p < 0.01). This decrease continued for 15 min. During HV, HbO2 remained low compared to the steady state (p < 0.05) in the experimental group. Total hemoglobin concentrations (HbT) decreased simultaneously with HbO2. In the control group, no changes in HbO2 or HbT were observed after saline administration, and only a slight decrease in HbO2 was observed during the 5 minutes' HV compared to the steady state. No changes in cytochrome aa3 (Cytaa3) were observed in either group during 100% O2 inhalation. We conclude that INDO decreased HbO2 and HbT by vasoconstriction, but that HV did not further aggravate this tendency. Great care should be taken when using INDO for newborn neonates.

Animals↗

PubMed2003

Hyperventilation-induced syncope: no need to panic.

Accurately diagnosing and treating adult patients presenting with recurrent syncope can be extremely problematic. We present the case of a patient who presented with recurrent syncope. We propose that many cases currently classified as idiopathic may in fact be due to orthostatic hypotension secondary to hyperventilation, or simply hyperventilation-induced syncope. The presence of undiagnosed psychiatric disorders should be considered in these patients.

Adult↗

PubMed1985

Methylprednisolone half-life during simultaneous barbiturate treatment and mechanical hyperventilation of neurosurgical patients.

The pharmacokinetics of methylprednisolone sodium succinate (MP) were studied in six neurosurgical patients under intensive treatment with large doses of MP, barbiturates, and mechanical hyperventilation. The study showed a remarkable level of enzyme induction within 24 hours after starting treatment, when the first blood samples were taken. The half-life (t 1/2) for MP during barbiturate and hyperventilation therapy was found to be reduced by a mean 55% (p less than 0.01) in relation to the t 1/2 of MP when administered alone. Studies on the day after termination of barbiturate intake indicated a tendency for an increase in the t 1/2 of MP, but it was not significantly different from the pretermination assessment (p greater than 0.05). On the basis of this study it is not possible to determine if the change in t 1/2 alone is governed by enzyme induction or by a combination of this plus a change in the distribution and clearance of the steroid. The clinical implication of these findings is that patients who are undergoing steroid treatment and at the same time are sedated with barbiturates should have their MP dose increased in order to compensate for the marked reduction of t 1/2 of MP.

Adolescent↗

PubMed1991

Restoration of cerebrovascular responsiveness to hyperventilation by the oxygen radical scavenger n-acetylcysteine following experimental traumatic brain injury.

Previous experiments have shown that, following experimental fluid-percussion brain injury, cyclo-oxygenase-dependent formation of oxygen radicals prevents arteriolar vasoconstriction in response to hyperventilation. The oxygen radical scavengers superoxide dismutase and catalase restore normal reactivity; however, they are not routinely available for clinical use. The present study tested whether n-acetylcysteine (Mucomyst), an agent currently available for acetaminophen toxicity, could be used as a radical scavenger to restore reactivity after brain injury. N-acetylcysteine (163 mg/kg) was given intraperitoneally prior to or 30 minutes after fluid-percussion brain injury (2.6 atm) in cats, and reactivity to hyperventilation was tested 1 hour after injury. The authors found either that pre- or postinjury administration led to normal reactivity. Additional experiments supported the hypothesis that n-acetylcysteine is an oxygen radical scavenger, since it reduced or prevented the free radical-dependent cerebral arteriolar dilation normally induced by the topical application of arachidonic acid or bradykinin. The mechanism by which n-acetylcysteine is effective in trauma may involve direct scavenging of radicals or stimulation of glutathione peroxidase activity. The results suggest that n-acetylcysteine may be useful for treatment of oxygen free radical-mediated brain injury.

Acetylcysteine↗

PubMed1976

Post-traumatic and postoperative treatment of severe brain injuries with controlled hyperventilation.

Controlled hyperventilation has shown to be an effective method of treatment in patients with pronounced brain edema and high ICP caused by accidental or surgical damage. This treatment has to be started as early as possible after the injury to avoid secondary changes and spreading cerebral edema leading to the impact of the brain-stem and thus irreversible brain damage. If conducted consequently, controlled hyperventilation will diminish mortality rate and increase the rate of valuable recoveries in all sorts of brain injuries.

Brain Edema↗