Hyperventilation in the awake state: potentially treatable component of Rett syndrome

Hyperventilation, which occurs in some patients with severe mental handicap, is a prominent feature in the histories of most girls with Rett syndrome but its mechanism and effects have not been established. Respiratory function was therefore studied in 18 patients with Rett syndrome and 23 healthy controls. Ten of the patients (56%), but none of the controls, hyperventilated only when awake, and began doing so after a period of normal breathing without hypoxaemia. After hyperventilation was established it was interspersed with prolonged periods of apnoea (over 19 seconds) accompanied by Valsalva manoeuvres. Hypoxaemia (less than 90%) occurred in 47% of these periods of apnoea and five (50%) of the patients had oxygen saturation values of under 50%. During hyperventilation severe hypocapnia developed in every patient, and recorded arterial pH measurements ranged from 7.47 to 7.60. A further four patients (22%) did not hyperventilate, but had clear histories of hyperventilation when younger. All had frequent apnoeic pauses accompanied by Valsalva manoeuvres. The remaining four girls (22%) neither hyperventilated nor gave a clear history of doing so. Three had occasional apnoeic pauses associated with the Valsalva manoeuvres. All but one of the 18 patients had increased quantities of periodic apnoea compared with the control subjects. The hypocapnic alkalaemia and hypoxaemia resulting from hyperventilation may contribute to the cerebral impairment in Rett syndrome. Since the hyperventilation is 'primary', and not secondary to preceding apnoea, it is potentially treatable. Further studies will determine if treatment is practical and of benefit.

Absence seizure with generalized rhythmic delta activity

In seven children, 5-11 years old, who presented with spells of staring or unresponsiveness, hyperventilation reproduced clinical spells that were accompanied on the EEG by generalized, rhythmic, delta activity. The discharges were usually of abrupt onset, extremely high amplitude, recurrent, and prolonged. One spontaneous staring spell, not provoked by hyperventilation, was also accompanied by generalized rhythmic delta activity. All patients had improvement or complete control of their spells and abolition of the EEG changes with ethosuximide or valproate. Delta activity during hyperventilation in children may not always be benign and may be associated with clinical absence seizures.

Hyperventilation and myocardial infarction

Chest pain that is associated with hyperventilation is often considered to be benign and noncardiac in nature. While not commonly recognized, hyperventilation can provoke coronary vasospasm. We report a man who presented with hyperventilation and developed myocardial infarction. In the setting of hyperventilation, chest pain and ST segment elevation, coronary vasospasm must be considered.

Role of cooling and drying in hyperventilation induced asthma

Respiratory heat loss has been proposed as a mechanism of exercise induced asthma. Whether the predominant stimulus is airway drying or cooling remains unclear. We have measured changes in FEV1 after isocapnic cold air hyperventilation (CAH) (-23.4 degrees (SD 0.43 degrees) C) and dry ambient air hyperventilation (AAH) (18.7 degrees (0.52 degrees)C) in seven asthmatic patients (mean age 31 (SD 9) years and baseline FEV1 3.2(0.9)1) and in seven normal subjects (age 28(6) years and FEV1 3.6(0.7)1). The inspired water content in both cases was 0.3 mg/l air. The rate of respiratory heat exchange per breath was calculated in watts (W) with microcomputer based equipment. Cold air hyperventilation caused a fall in FEV1 almost twice that of ambient air hyperventilation at each level of ventilation: CAH v AAH (% fall) 8.0 (5.1) v 3.9 (4.0) at 15 l/min, 11.6 (7.8) v 7.0 (4.4) at 30 l/min, and 20.7 (10.9) v 12.4 (6.3) at 60 l/min. Identical latent heat loss (evaporative drying) was imposed on the airway during the two challenges. Sensible heat loss (convective cooling) in cold air hyperventilation was 41 W at 15 l/min, 63 W at 30 l/min, and 114 W at 60 l/min; whereas in ambient air hyperventilation the loss was 6, 13, and 23 W respectively. It is concluded that the rate of cooling of the upper airway is the predominant stimulus in hyperventilation induced asthma.

Attenuation of hyperventilation-induced bronchospasm by terfenadine: a new antihistamine

The effect of terfenadine, a selective H1-receptor antagonist devoid of central nervous system side effects, was evaluated on hyperventilation-induced bronchospasm in 11 adult subjects with asthma in a double-blind, placebo-controlled, crossover study. Increases in specific airway resistance (SRaw) were induced by isocapnic hyperventilation with dry air on two occasions, 7 days apart. Before the tests, the subjects received oral terfenadine (120 mg, twice daily) or placebo for 3 days with the last dose administered 3 hours before the test. Baseline SRaw and spirometric values (vital capacity and FEV1) were similar for the two tests. Terfenadine yielded a significant (p less than 0.001) parallel shift to the right of the stimulus (hyperventilation)-response (SRaw) curve; 100% increases in SRaw occurred at ventilation rates of 44 L/min after placebo treatment and 64 L/min after terfenadine treatment. These data suggest that histamine release plays a role in hyperventilation-induced bronchospasm despite the fact that increase in plasma histamine has not been found in this situation, in contrast to exercise-induced bronchospasm.

Possible role of coronary spasm in acute myocardial infarction precipitated by hyperventilation

Acute myocardial infarction was precipitated by hyperventilation in a 65 year old man. His coronary arteriogram in the chronic phase showed almost normal coronary arteries. Injection of acetylcholine (50 micrograms) into the left coronary artery induced spasm of the circumflex artery with chest pain in association with ST-segment elevation in the inferior leads and ST-segment depression in the precordial leads. In this patient there may have been atherosclerosis of the coronary arteries with absent or dysfunctional endothelium, despite an almost normal angiographic appearance. In the absence of endothelium the response of the smooth muscle to acetylcholine is constriction.

Ventilatory physiology of patients with panic disorder

Thirty-one patients with DSM-III panic disorder or agoraphobia with panic attacks, 13 normal controls, and 12 patients with other anxiety disorders were studied during ventilatory challenge with room air hyperventilation and 5% carbon dioxide inhalation. Patients also underwent sodium lactate infusion. Among the patients with panic disorder, 58% panicked with sodium lactate, 39% with 5% CO2, and 23% with room air hyperventilation. Of the other patients, four panicked with sodium lactate, none with 5% CO2, and one with room air hyperventilation. One normal control panicked with both sodium lactate and 5% CO2. Panic with CO2 was associated with an exaggerated ventilatory response and increases in plasma norepinephrine level and diastolic blood pressure. Patients with panic disorder may have hypersensitive CO2 receptors that, when triggered, evoke a subjective panic associated with an exaggerated ventilatory response and consequent hypocapnic alkalosis.

Systemic alkalosis as a provocative test for coronary artery spasm in patients with infrequent resting chest pain

Systemic alkalosis was used to detect coronary spasm in 237 patients with infrequent, resting, angina-compatible chest pain. The provocative test was performed without previous coronary arteriography but only in patients with negative submaximal exercise test results. Rapid infusion of alkaline solution followed by maximal hyperventilation raised arterial pH above the 7.65 value necessary for diagnostic significance in 196 (83%) patients. In 24 (12%) of these patients the provocative test induced significant ischemic ST segment changes. In all patients with a positive response, coronary artery disease, which was predominantly vasospastic (19 patients) or atheromatous with a vasospastic contribution (five patients), was demonstrated by coronary arteriography followed, if necessary, by ergot derivative injection. Chest pain and ECG changes were always reversed within 5 minutes by intravenous nitroglycerin. Coronary arteriography was not performed in all patients with a negative response; therefore, the sensitivity of the procedure could not be assessed. However, 36 patients with a negative response to hyperventilation underwent coronary arteriography; 33 (92%) had normal arteriograms and a negative response to ergot derivatives. Hyperventilation appears to be a safe and specific diagnostic procedure in a subset of patients in whom the probability of coronary artery disease may not be judged sufficient to warrant coronary arteriography as a primary diagnostic approach.

Airway constriction by isocapnic hyperventilation of cold, dry air: comparison of magnitude and duration of protection by nedocromil sodium and sodium cromoglycate

The protective effect of 1, 2 and 4 mg of nedocromil sodium against airway constriction induced by hyperventilation of cold, dry air was compared with 10 mg sodium cromoglycate and placebo in a double-blind randomized trial. On 5 days, twelve asthmatic subjects received one of the trial medications from a metered dose inhaler. Twenty minutes, 2.5 and 5 hr later, airway responsiveness to hyperventilation of cold, dry air was measured. At 20 min, there was significant protection by all four active medications when compared to placebo, with a trend towards a nedocromil dose relationship but there was no statistical difference between the four active medications. All four showed a similar progressive decrease in protection over 5 hr. The results of this study suggest that nedocromil gives protection against hyperventilation-stimulated airway constriction and that the magnitude and duration of effect for all three doses is similar to 10 mg of cromoglycate.

[Prinzmetal's syncopal angina during an electroencephalogram. Triggering role of the hyperpnea test]

We are reporting a cardiac arrest occurring during an electroencephalogram with hyperventilation. The diagnosis is made on the Holter recording which shows a Prinzmetal's angor tracing followed with ventricular arrhythmias, leading to asystoly. The physiopathology of the spasm is not clear and we are discussing the possible mechanisms. We stress again the harmful role of beta-blockers in this pathology. In addition, we insist on electrocardiographic manifestations surrounding sudden death. As for the hyperventilation test, its potential risks call for caution during its performance.

Hyperventilation and panic attacks

The symptoms of hyperventilation syndrome and panic disorder are very similar. A questionnaire was used to assess the incidence of panic disorder in 274 patients; 35% of the patients with hyperventilation and only 5% of the non-hyperventilating patients showed panic disorder. The authors conclude that hyperventilation plays an important role in panic disorder and in generalized anxiety disorder.

Regional cerebral blood flow, clinical manifestations, and age in children with moyamoya disease

In children with Moyamoya disease, transient ischemic attacks often occur during hyperventilation, and the frequency of attacks usually decreases with advancing age. To elucidate the mechanism of the attacks, the regional cerebral blood flow was measured during rest and/or hyperventilation in children aged 3-16 with Moyamoya disease. Regional cerebral blood flow during rest was significantly higher in younger children with Moyamoya disease, and it progressively decreased with advancing age through childhood. During hyperventilation, regional cerebral blood flow decreased in all the children, although blood flow in younger children was still higher than that in the older children. Nevertheless, transient ischemic attacks were more readily precipitated by hyperventilation in the younger than in the older children. Cerebral metabolic demand is much higher in the first decade of life than in later decades. Therefore, it seems likely that even a moderate reduction in cerebral blood flow can cause metabolic impairment in young children. Such high cerebral metabolic demand may play an important role in the frequent occurrence of transient ischemic attacks in young children with Moyamoya disease.

Does regular treatment with ketotifen inhibit bronchoconstriction induced by isocapnic hyperventilation?

Eight asthmatic patients completed a 12-week, double-blind, placebo controlled study to assess the efficacy of ketotifen, 1 mg twice daily, in the inhibition of bronchoconstriction induced by isocapnic hyperventilation (IH). There was no significant difference in the degree of bronchoconstriction produced by IH after treatment with ketotifen or placebo.

Hyperventilation and Raynaud's disease

A 42 year old woman with long standing Raynaud's disease, unresponsive to medical and surgical treatment, was noted to have a typical history of the hyperventilation syndrome. Rewarming of the hands following cold challenge was markedly prolonged in the presence of hypocapnia. It is suggested that hyperventilation may have an aetiological role in maintaining digital artery spasm in Raynaud's disease, which would benefit from recognition and treatment.

Acid-base balance in real life panic

A case of naturally occurring panic attack is described. Blood gas analysis was performed during and after the attack and compared with the baseline values in the same patient. The possible significance of the observed shifts is discussed.

Hyperventilation syndrome and asthma

Hyperventilation syndrome is a common and often disabling condition. Traditional treatment consists of reassurance and anxiolytic drugs. Hyperventilation is known to precipitate an asthmatic reaction. A retrospective review of patients with hyperventilation syndrome was performed to ascertain the frequency of asthma as well as the response to bronchodilator medication. Forty-seven patients were seen. Thirty-eight were tested, and asthma was proved in 36. Two additional patients had positive clinical responses with bronchodilators. Thus, asthma was identified in 38 of 47 consecutive patients seen for hyperventilation syndrome (80 percent), and asthma was proved in 36 of 38 of patients tested (95 percent). Hyperventilation syndrome was eliminated in 29 of 35 patients (90 percent) treated with a combination of explanation and bronchodilator treatment.