Oxygen desaturation following voluntary hyperventilation in normal subjects

An adolescent with Wolfram syndrome and central sleep apnea

Wolfram syndrome is a rare autosomal recessive disorder affecting approximately 1 in 500,000 individuals. The disorder is most commonly caused by mutations in the WFS1 gene, which encodes an endoplasmic reticulum protein, wolframin, which is thought to protect against endoplasmic reticulum stress-related apoptosis. The major clinical findings of Wolfram syndrome are diabetes mellitus and optic atrophy, both of which usually appear before 16 years of age. Common additional findings include sensorineural hearing impairment, central diabetes insipidus, nonautoimmune hypothyroidism, delayed puberty, neurogenic bladder, cerebellar ataxia, and psychiatric disorders. Central sleep apnea is an uncommon but serious feature of Wolfram syndrome. However, the clinical details of this manifestation have not been documented. Herein, we report an adolescent with recently diagnosed Wolfram syndrome who demonstrated severe central sleep apnea on polysomnography testing.

CITATION

Harris JC, Kenkare JD, Schramm CM. An adolescent with Wolfram syndrome and central sleep apnea. J Clin Sleep Med. 2024;20(7):1205-1208.

Prolonged post-hyperventilation apnea in two young adults with hyperventilation syndrome

BACKGROUND

The prognosis of hyperventilation syndrome (HVS) is generally good. However, it is important to proceed with care when treating HVS because cases of death following hyperventilation have been reported. This paper was done to demonstrate the clinical risk of post-hyperventilation apnea (PHA) in patients with HVS.

CASE PRESENTATION

We treated two patients with HVS who suffered from PHA. The first, a 21-year-old woman, had a maximum duration of PHA of about 3.5 minutes and an oxygen saturation (SpO2) level of 60%. The second patient, a 22-year-old woman, had a maximum duration of PHA of about 3 minutes and an SpO2 level of 66%. Both patients had loss of consciousness and cyanosis. Because there is no widely accepted regimen for treating patients with prolonged PHA related to HVS, we administered artificial ventilation to both patients using a bag mask and both recovered without any after effects.

CONCLUSION

These cases show that some patients with HVS develop prolonged PHA or severe hypoxia, which has been shown to lead to death in some cases. Proper treatment must be given to patients with HVS who develop PHA to protect against this possibility. If prolonged PHA or severe hypoxemia arises, respiratory assistance using a bag mask must be done immediately.

The psychophysiology of blood-injection-injury phobia: looking beyond the diphasic response paradigm

Blood-injection-injury (BII) phobia is an anxiety disorder that may be accompanied by vasovagal fainting during confrontation with the feared stimuli. The underlying pattern of autonomic regulation has been characterized as a diphasic response, with initial increases in heart rate and blood pressure that are typical of a fight-flight response, and subsequent drops in blood pressure and/or heart rate that may precipitate vasovagal fainting. Tensing skeletal muscles of the arms, legs, and trunk (applied tension) has been proposed as a technique to cope with this dysregulation. This review critically examines the empirical basis for the diphasic response and its treatment by applied tension in BII phobia. An alternative perspective on the psychophysiology of BII phobia and vasovagal fainting is offered by focusing on hypocapnia that leads to cerebral blood flow reductions, a perspective supported by research on neurocardiogenic and orthostatically-induced syncope. The evidence may indicate a role for respiration-focused coping techniques in BII phobia.

Subjective sleep quality alterations at high altitude

OBJECTIVE

Sleep pattern at high altitude has been studied, mainly with the use of polysomnography. This study aimed to analyze subjective sleep quality at high altitude using the following standardized scales: the Pittsburgh Sleep Quality Index (PSQI) and the Athens Insomnia Scale (AIS-8).

METHODS

Thirty-two members of 2 expeditions--28 males and 4 females (mean age 31 years)--participated in this study conducted in Nepal, Himalayas (Lobuche East, 6119 m above sea level [masl]), Kyrgyzstan, Pamirs (Lenin Peak, 7134 masl), and Poland (sea level). The scales were administered twice, at high altitude (mean altitude 4524 masl) and at sea level.

RESULTS

Both measures showed a decrease in sleep quality at high altitude (statistical significance, P < .001). Sleep problems affected general sleep quality and sleep induction. Sleep disturbances due to awakenings during the night, temperature-related discomfort, and breathing difficulties were reported. High altitude had no statistically significant effect on sleep duration or daytime dysfunction as measured by PSQI.

CONCLUSIONS

The overall results of PSQI and AIS-8 confirm the data based on the climbers' subjective accounts and polysomnographic results reported in previous studies. The introduction of standardized methods of subjective sleep quality assessment might resolve the problem of being able to perform precise evaluations and research in the field of sleep disturbances at high altitude.

Post-hyperventilation hypoxaemia is due to alteration of ventilation and perfusion matching

OBJECTIVE

The aim of this study was to investigate the mechanisms of post-hyperventilation hypoxia.

METHODOLOGY

Seven healthy male volunteers, aged 29.1 +/- 1.4 years, underwent two 10-min periods of voluntary hyperventilation to pulmonary end tidal CO2 values of 20 mmHg (severe hyperventilation), or 30 mmHg (moderate hyperventilation). Post-hyperventilation, the arterial oxygen saturation, VE and arterial blood gas values were measured. Sleep was excluded by EEG monitoring.

RESULTS

Maximal hypoxaemia occurred in proportion to severity of hyperventilation; at approximately 5 min post-hyperventilation Pao2 fell to 64 +/- 7 mmHg (severe hyperventilation) and 72 +/- 6 mmHg (moderate hyperventilation) from 97 +/- 3 mmHg at baseline. Hypoxaemia persisted beyond the time of normalization of Paco2 and HCO3. On another occasion, a N2 washout test was performed after severe hyperventilation, which excluded bronchoconstriction.

CONCLUSION

Relative hypoventilation may partly explain post-hyperventilation hypoxaemia, but by excluding bronchoconstriction and periodic breathing, we have demonstrated that most of the hypoxaemia must have been due to alteration of pulmonary blood flow distribution causing a fall in V/Q ratio.

Sleep at High Altitude

New arrivals to altitude commonly experience poor-quality sleep. These complaints are associated with increased fragmentation of sleep by frequent brief arousals, which are in turn linked to periodic breathing. Changes in sleep architecture include a shift toward lighter sleep stages, with marked decrements in slow-wave sleep and with variable decreases in rapid eye movement (REM) sleep. Respiratory periodicity at altitude reflects alternating respiratory stimulation by hypoxia and subsequent inhibition by hyperventilation-induced hypocapnia. Increased hypoxic ventilatory responsiveness and loss of regularization of breathing during sleep contribute to the occurrence of periodicity. Interventions that improve sleep quality at high altitude include acetazolamide and benzodiazepines.

Transcutaneous PCO(2) monitoring with hyperventilation during phonation in vocal cord paralysis

OBJECTIVE

Hyperventilation during phonation is one of the causes of fatigue in-patients with vocal disorders.

METHODS

The transcutaneous (tc) PCO(2) during phonation in 8 normal subjects and 12 patients with unilateral vocal cord paralysis was measured. Cases were further divided into two groups by the degree of the tcPCO(2) decrease during phonation. Patients with a tcPCO(2) decrease less than 3.4 mmHg during phonation were classified as group 1 (G1). Patients with a tcPCO(2) decrease larger than or equal to 3.4 mmHg during phonation were classified into group 2 (G2).

RESULTS

The average changes in tcPCO(2) in the G1 cases was not significantly different from that in normal subjects. The decrease in tcPCO(2) during phonation in the six G2 cases was 10.7+/-6.2 mmHg, and was significantly different from that in normal subjects (P<0.01, t-test). The decrease of tcPCO(2) during phonation in both G1 and G2 cases improved significantly after surgical treatment. Easy fatigability during phonation in two G1 cases and five G2 cases improved.

CONCLUSIONS

The decrease in tcPCO(2) during phonation in cases of unilateral vocal cord paralysis is well correlated with easy fatigability. It is clinically useful to classify cases into two groups using the criteria of a less than 3.4 mmHg or larger than or equal to 3.4 mmHg decrease in tcPCO(2). These results also suggest that hyperventilation is one major cause for easy fatigability during phonation in cases with unilateral vocal cord paralysis. TcPCO(2) changes during phonation are useful in evaluating hyperventilation and the effect of treatment.

Hyperventilation and attention: effects of hypocapnia on performance in a stroop task

This study aimed to investigate the effect of hypocapnia on attentional performance. Hyperventilation, producing hypocapnia, is associated with physiological changes in the brain and with subjective symptoms of dizziness, concentration problems and derealization. In this study (N=42), we examined cognitive performance on a Stroop-like task, following either 3 min of hypocapnic or normocapnic overbreathing. Both overbreathing trials were run on separate days, each preceded by a baseline trial with the same task during normal breathing. More and other symptoms were reported after hypocapnia compared to normocapnia. Also, more errors were made and progressively slower reaction times (RT's) were observed during recovery from hypocapnia. These performance deficits were only found in participants characterized by apneas. The number of symptoms did not correlate with RT's or errors. The pattern of data suggested that hypoxia, as a result of apneas during recovery from hypocapnia, caused the cognitive performance deficit.

Hypoxic ventilatory response and breathlessness following hypocapnic and isocapnic hyperventilation

STUDY OBJECTIVES

To investigate the etiology of posthyperventilation (post-HV) hypoxemia following voluntary hyperventilation (VHV), we examined the effects of hypocapnic (hypo-CO2) and isocapnic (iso-CO2) VHV on the hypoxic ventilatory response (O2-response) and on the sensation of breathlessness during the O2-response.

METHODS

O2-responses and visual analog scale (VAS) scores for estimating breathlessness in 10 normal subjects during the O2-response under iso-CO2 conditions and under hypo-CO2 conditions immediately following voluntary maximal HV of 3 min duration were examined.

RESULTS

Although there was no significant difference in the post-HV ventilation levels following hypo-CO2 vs iso-CO2 VHV, the VAS scores at the start of the O2-response following hypo-CO2 VHV (30.2+/-24.2 mm) were significantly higher (p<0.05) than the VAS scores at the start of the O2-response following iso-CO2 VHV (13.7+/-8.4 mm). However, VHV did not have a significant effect on the O2-response at 2 min after the VHV when the arterial O2 saturation (SaO2) was below 90%. The nonsteady-state hypo-CO2 induced by VHV greatly attenuated the O2-response below 90% SaO2 and VAS scores at 70% SaO2.

CONCLUSIONS

Elevated VAS scores immediately following the hypo-CO2 VHV, which might be independent of actual breathing levels, and the attenuation of the O2-response following the hypo-CO2 VHV were not due to input from lung and chest wall mechanoreceptors induced by the hyperpnea itself, but rather to the hypo-CO2 induced by hyperpnea.