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Hypersensitivity to carbon dioxide as a disease-specific trait marker.

There is now substantial evidence that an abnormal threshold for suffocation alarm underlies panic disorder. Because this disorder is highly familial, evidence of an abnormal suffocation threshold may be apparent in high-risk individuals before they develop clinical illness. To explore this possibility, we used a single inhalation of 35% CO2 vs. air to evaluate 11 subjects who had at least one first-degree relative with DSM-III-R panic disorder, 13 who had at least two relatives treated for mania or for depression (HR-AD), and 15 low-risk controls who had no family history of panic disorder, affective disorder, or alcoholism (LR-C). All were aged 18-34 and had no history of panics or of any Research Diagnostic Criteria disorder. Five (45.5%) of the subjects at high risk for panic disorder, but none of the LR-C subjects (p = .007), nor any of the HR-AD subjects (p = .011), developed a panic attack following inhalation of the CO2 mixture.

Adolescent↗

Coping strategies of panic and control subjects undergoing lactate infusion during magnetic resonance imaging confinement.

The psychological reactions and coping strategies used in response to a behavioral contingency (confinement in a magnetic resonance imaging [MRI] scanner) during a biological challenge (sodium lactate infusion) were systematically studied in 13 subjects with panic disorder (PD) and 11 control subjects using the Claustrophobia Questionnaire (CQ) and the Revised Ways of Coping Checklist (RWCCL). All participants were able to successfully complete the experimental procedure. Findings suggest between-group coping strategy differences in response to general stressors, but relative convergence of coping strategies in response to the experimental procedure, with relatively greater emphasis on problem-focused coping approaches. These observations suggest that PD patients are able to engage in effective coping strategies in response to stressful but highly structured experimental situations. An overall pre-post MR scanning reduction in the fear of restriction but not suffocation was observed for the combined sample, primarily reflecting changes in the control group. Among PD subjects, higher levels of suffocation fears were maintained despite emergence of more problem-focused coping in the experimental situation.

Adaptation, Psychological↗

Central and peripheral chemoreflexes in panic disorder.

Klein (Arch Gen Psychiatry, 50, 1993, 306-317) has suggested that panic disorder patients have a false suffocation alarm that may be associated with a lowered threshold for carbon dioxide detection. We compared the thresholds and sensitivities of the central and peripheral chemoreflexes between panic disorder patients and age- and sex-matched healthy volunteers to test this aspect of the hypothesis. We used a modified version of Read's rebreathing technique in 11 panic disorder patients and 10 healthy volunteers to examine the peripheral and central chemoreflex characteristics in these two populations. Subjects were examined during three rebreathing tests: training, hyperoxic (central chemoreflex alone) and hypoxic (combined central and peripheral chemoreflex). Panic symptoms were retrospectively assessed between groups using a DSM-IV derived Panic Symptom Scale. Comparisons of panic disorder patients with agoraphobia and healthy volunteers showed no significant differences in sensitivities or thresholds. Klein's hypothesis is not supported by these data. If a false suffocation alarm exists, its triggering may not be implemented within the respiratory chemoreflexes.

Adult↗

Emergency preparedness and response in Israel during the Gulf War.

We examined the effect of the emergency response on medical and public health problems during the 1991 Gulf War in Israel. On the first day of the conflict, the number of deaths from suffocation, asphyxiation, aspiration, myocardial infarction, cardiac arrest, and cerebrovascular accident increased abruptly, as did the number of sudden deaths associated with the use of tight-fitting masks with filters in sealed rooms. Much of the excess risk for death from cardiorespiratory complications during the first alert may have been a consequence of its duration (140 minutes). Mass evacuation and concrete buildings are believed to have kept the death toll from trauma down, and mask use may have protected against facial and upper-airway injuries. Falls and hip fractures, airway irritation from exposure to bleach, carbon monoxide intoxication from open kerosene heaters in sealed rooms, and self-injection with atropine syringes were also noted. A measles epidemic and increased death rates from automobile crashes were other preventable causes of death. Protection against biological warfare was limited to surveillance of trends for pneumonia and gastroenteritis. Emergency planners failed to anticipate the need for better mask fit, hands-on training in the use of masks, and special guidelines for older persons to prevent deaths from suffocation and other cardiovascular-respiratory problems in the first minutes of use. If masks are to be distributed as a protection against chemical warfare, a simpler model including the use of shrouds for whole-body skin protection might help avoid cardiorespiratory complications. Public health problems not adequately dealt with in the predisaster period are apt to emerge with greater severity during a crisis.

Accidents, Traffic↗

Emergency preparedness and response in Israel during the Gulf War.

We examined the effect of the emergency response on medical and public health problems during the 1991 Gulf War in Israel. On the first day of the conflict, the number of deaths from suffocation, asphyxiation, aspiration, myocardial infarction, cardiac arrest, and cerebrovascular accident increased abruptly, as did the number of sudden deaths associated with the use of tight-fitting masks with filters in sealed rooms. Much of the excess risk for death from cardiorespiratory complications during the first alert may have been a consequence of its duration (140 minutes). Mass evacuation and concrete buildings are believed to have kept the death toll from trauma down, and mask use may have protected against facial and upper-airway injuries. Falls and hip fractures, airway irritation from exposure to bleach, carbon monoxide intoxication from open kerosene heaters in sealed rooms, and self-injection with atropine syringes were also noted. A measles epidemic and increased death rates from automobile crashes were other preventable causes of death. Protection against biological warfare was limited to surveillance of trends for pneumonia and gastroenteritis. Emergency planners failed to anticipate the need for better mask fit, hands-on training in the use of masks, and special guidelines for older persons to prevent deaths from suffocation and other cardiovascular-respiratory problems in the first minutes of use. If masks are to be distributed as a protection against chemical warfare, a simpler model including the use of shrouds for whole-body skin protection might help avoid cardiorespiratory complications. Public health problems not adequately dealt with in the predisaster period are apt to emerge with greater severity during a crisis.

Accidents, Traffic↗

Analysis of SIDS-related civil and criminal court cases in Japan.

Thirty-three sudden infant death syndrome (SIDS)-related civil and criminal lawsuits in Japan were retrieved from judicial precedent databases "Hanrei Masutar (Judicial Decisions Master)" and "Hanrei Taikei (Judicial Decisions System) using "SIDS" as a keyword. Sleeping posture and developmental stage of occurrence were studied in each of the cases retrieved, whether or not a legal autopsy had been performed. The influence exerted on court decisions by Japanese definitions of SIDS as well as the relationship between causes of death and court decisions were studied. Of 33, two were criminal cases (business/professional negligence on the part of the defendants, leading to death), and the rest were civil cases (claims for damages). Because the decision handed down in both criminal cases was "cause of death unknown", these defendants were found innocent. One of these cases was argued in both the court of appeals and the superior court: these courts found SIDS to be the cause of death and consequently the claim for damages was rejected. Both criminal and civil courts dealt with another case: the former found the cause of death to be "unknown" and the defendant innocent, while the latter, finding SIDS the cause of death, declined to review. In cases where the sleeping posture was prone, courts tended to decide the cause of death to be suffocation, especially with neonates. Because diagnosis by exclusion is required in cases of a legal autopsy for SIDS, the diagnosis is difficult without an autopsy. Disagreements between the results of legal autopsy and court decisions occurred in eight cases. With such a discrepancy, a detailed case examination is necessary. In 1983, SIDS was defined in Japan in two different ways; one in a more strict sense and the other being more inclusive. The wider and narrower definitions were unified in 1995 by requiring a survey of the circumstances of death in addition to the narrower definition. Because of this situation, the two cases in the 1980s when legal autopsy was not enforced fell into the category of "SIDS in a wider sense." In no case was a defendant found guilty when the cause of death was judged to be either SIDS/ALTE or unknown. Four cases were rejected when the cause of death was judged to be neither due to suffocation nor SIDS, while seven were accepted either as cases of "joint faults that canceled each other," or as "partial acceptance." In Japan, official views concerning a SIDS diagnosis differ among pediatricians, legal scholars of forensic medicine and pathologists. These differences appeared to influence the legal decisions. Several conferences should be convened as soon as possible to provide an opportunity to resolve the main points of difference between these three professional groups and, thus, attain a unified view.

Age Factors↗

Helicopter transport of patients to tertiary care centers after cardiac arrest.

Air transport is commonly used to transfer survivors of cardiac arrest from rural hospitals to large tertiary-care centers, presumably to improve outcome. To examine this issue, a retrospective review of patients stabilized after a cardiac arrest was conducted; 157 transports were reviewed. The mean age of patients was 37.9 +/- 27.8 yrs, with a male to female ratio of 2.2:1. Survivors were significantly older than nonsurvivors. Thirty-one of 69 patients (45%) with primary cardiac disease were discharged alive from the hospital, 75% without neurological sequelae. Only a minority of patients with noncardiac medical illness (7%), electrical injury (33%), suffocation (15%), near-drowning (15%), and inhalation (0%) were discharged alive from the hospital. Outcomes for cardiac arrest in adult patients older than 65 years (32.3% survival) were similar to those for adult patients younger than 65 years (36.2% survival) (P = .887). These results show that survivors of a primary cardiac event have a favorable outcome when transferred by air to tertiary centers when compared with historical controls that were transported by ground. On the other hand, cardiac arrests from noncardiac medical illness, suffocation, near-drowning, and inhalation have a grim prognosis. Prospective studies should clarify the role of air transport in these patients.

Adolescent↗

[Transtracheal jet ventilation with spontaneous ventilation in neoplastic laryngeal dyspnea].

In six suffocating patients with a severe upper airway obstruction (three patients after direct laryngoscopy under general anaesthesia and three patients with cervical tumor scheduled for a difficult tracheostomy), jet-ventilation was delivered using a transtracheal catheter. The jet-ventilator insufflated oxygen only when the tracheal pressure was below a preset value, during spontaneous inspiration. During expiration, tracheal pressure increased above the preset value, the ventilator stopped the insufflation and the expiratory gases escaped through the upper airway. This method corresponds to an inspiratory support without intubation. In post-anaesthesia patients, oxygenation and alveolar ventilation were improved, allowing the avoidance of tracheostomy. In the other patients, tracheostomy was made possible with good surgical conditions under general anaesthesia. This method can be applied in conscious patients and allows oxygenation of suffocating patients.

Adult↗

The Claustrophobia Questionnaire.

The content and psychometric properties of the Claustrophobia Questionnaire (CLQ) are described. An earlier version of the CLQ was developed to test the hypothesis that claustrophobia is comprised of two distinct but related fears--the fear of suffocation and the fear of restriction [J. Anxiety Disord. 7 (1993) 281.]. The scale was used to assess patients undergoing the magnetic resonance imaging (MRI) procedure [J. Behav. Med. 21 (1998) 255.] and in participants with panic disorder [J. Abnorm. Psychol. 105 (1996) 146; Taylor, S., Rachman, S., & Radomsky, A. S. (1996). The prediction of panic: a comparison of suffocation false alarm and cognitive theories. Unpublished data.]. On the basis of these studies, we decided to revise and shorten the CLQ, collect normative data, and provide information on the scale's predictive and discriminant validity as well as its internal consistency and test-retest reliability. This was done through a set of four interconnected studies that included psychometric analyses of undergraduate and community adult questionnaire responses and behavioural testing. Results indicate that the CLQ has good predictive and discriminant validity as well as good internal consistency and test-retest reliability. The CLQ appears to be a reliable and sensitive measure of claustrophobia and its component fears. We encourage the use of the CLQ in a variety of clinical and research applications. The scale is provided in this paper for public use.

Adult↗

A sudden death case of laryngocele accompanied by infarction of the dorso-lateral portion of the medulla oblongata.

A 70-year-old man, who had a laryngeal tumor discovered by otolaryngological examination during admission for suspicion of facial nerve paralysis was found dead in his bed on the seventh hospital day. Clinical doctors aspirated a large amount of mucous sputum from his larynx during their attempt at resuscitation. Although the direct cause of death was clinically unknown, an autopsy revealed an internal type laryngocele, a type of laryngeal cyst, in the right larynx and infarction of the left dorso-lateral portion of the medulla oblongata. Suffocation resulted from mucous sputum filling his larynx, which had been narrowed by a laryngocele from the right, in an unfortunate association with movement disturbance of the left larynx caused by the infarction of the left dorso-lateral portion of the medulla oblongata. We assumed this to be the direct cause of death, because the heart and lungs showed no remarkable changes that could be ascribed to it. This case offers important suggestions concerning the risks of suffocation due to laryngeal cysts, especially in patients with complications.

Journal Article↗

Pathological findings in overlaying.

A 2-month-old girl is reported who was found in cardiorespiratory arrest beneath her unconscious mother. Full autopsy examination failed to reveal any features which would give an indication of the nature of the terminal event. This case confirms the non-specificity of autopsy findings in an infant who suffocated underneath an adult--a situation mimicking classical 'overlaying'. Given that there may be no specific histopathological findings when an infant suffocates underneath an adult, a diagnosis should not be formulated if a full death scene description is not available and no specific lesions or diseases are found. The manner of death should be designated as 'undetermined'.

Journal Article↗

Progressive increase in bone mass and development of odontomas in aging osteopetrotic c-src-deficient mice.

The critical role of c-src in osteoclast-mediated bone resorption has been emphasized by gene deletion experiments in mice. However, the long-term effects of the lack of c-src and impaired osteoclast function on the skeleton remain unknown. To further study the physiological role of c-src and to circumvent the early death of src(-/-) mice, due to starvation in the absence of erupted teeth, we maintained mice on a liquid diet. At the age of 2 months the src(-/-) mice presented signs of airway obstruction and all mice died progressively between 2.5 and 6 months of age. Radiography demonstrated severe osteopetrosis of the whole skeleton. Histomorphometrical analysis of the src(-/-) mice confirmed a significant increase in bone mass with age, resulting in complete loss of bone marrow spaces in some bones and explaining the consistent hepatosplenomegaly, due to extraskeletal hematopoesis. Histopathological examination of the skull revealed the presence of odontomas in the region of the unerupted incisors, with a penetrance of 100% in the aging src(-/-) mice. Although odontomas are benign lesions, their progressive growth leads to the obliteration of the nasal airways, progressive suffocation, and death in src(-/-) mice. These results suggest that: (i) in the absence of bone resorption, bone formation continues and leads to progressive accentuation of the osteopetrotic phenotype in src(-/-) mice; (ii) osteoclastic function is required for regular eruption of the incisors and deficient bone resorption is associated with the development of odontomas; and (iii) src(-/-) mice die by suffocation due to airway obliteration as a result of progressive odontoma growth.

Aging↗

Psychological and physiological predictors of response to carbon dioxide challenge in individuals with panic disorder.

Past studies in nonclinical samples have found that suffocation fear, but not a behavioral index of carbon dioxide (CO2) sensitivity (i.e., breath-holding duration), predicts anxious response to CO2 challenge. These associations were examined in individuals with panic disorder while adding more sensitive indices of CO2 sensitivity. Consistent with the earlier studies, the authors found that suffocation fear predicted anxious responding to CO2 challenge but breath-holding duration did not. However, highly precise measures of CO2 sensitivity, not included in earlier studies, did predict anxious challenge responding. These findings support the predictive value and possible etiological relevance of both specific psychological variables and physiological CO2 sensitivity in panic vulnerability. Further work is still needed to determine whether the findings are specific to panic disorder.

Adult↗

Beyond the usual suspects: a cholinergic route for panic attacks.

For unknown reasons and through poorly understood mechanisms, people at risk of panic attacks are hypersensitive to suffocative stimuli and experience hyperventilation and anxiety after exposure to heightened concentrations of carbon dioxide. Similarly to the physiological reflex response to hypercapnia in animals and man, the anxious response to carbon dioxide in people with panic disorder is at least partially controlled by the central muscarinic receptors. It is suggested here that some modifications of the cholinergic functions could underlie human individual differences in carbon dioxide sensitivity and proneness to experience panic attacks. The hypothesis is based upon experimental evidence that stressful and potentially harmful stimuli prime relatively long-lasting changes in cholinergic genes expression and cholinergic receptors' regulation. The adaptive sequels of these modifications include protection of the brain from overstimulation, and, at the level of the corticolimbic circuitries, promotion of passive avoidance and learning after stress. The extension of the same modifications to the cholinergic receptors involved in chemoception, however, could lower the threshold for reaction to suffocative stimuli, including carbon dioxide. The exaggerated sensitivity to carbon dioxide observed in humans suffering from panic attacks could then be thought of as an evolutionary cost of the involvement of the cholinergic system in shaping otherwise adaptive responses to stress and threatening stimuli.

Chemoreceptor Cells↗

Sudden death in infants sleeping on polystyrene-filled cushions.

BACKGROUND: Infants are at risk for both the sudden infant death syndrome (SIDS) and accidental suffocation. On postmortem examination, however, it is difficult to distinguish one from the other without information from the scene of death. Healthy infants are assumed to be able to turn their heads and, if not otherwise restrained, to obtain fresh air. We assessed this assumption in an investigation of infant deaths that occurred during sleep on cushions filled with polystyrene beads. METHODS: We obtained data on 25 deaths from the U.S. Consumer Product Safety Commission. We also used mechanical and animal models to study physiologic aspects of ventilation relevant to these results, by simulating the effects on an infant of breathing into a cushion. We measured the effects of softness, malleability (molding of the cushion about an infant's head), airflow resistance, and rebreathing of expired gases. RESULTS: All 25 study infants were prone when found dead, and at least 88 percent were face down with nose and mouth obstructed by the cushion. SIDS was the diagnosis in 19 of the 23 infants who underwent autopsy. Our findings show, however, that the cushion would have limited movement of the infant's head to obtain fresh air, and the amount of rebreathing we estimated to have occurred in the infants was lethal in a rabbit model. CONCLUSIONS: Accidental suffocation by rebreathing was the most likely cause of death in most of the 25 infants studied. Consequently, there is a need to reassess the cause of death in the 28 to 52 percent of the victims of SIDS who are found with their faces straight down. Safety regulations setting standards for softness, malleability, and the potential for rebreathing are needed for infant bedding.

Air Movements↗

Female resistance to hypoxia: does it explain the sex difference in mortality rates?

There is currently no accepted explanation in the medical literature for the lower female total mortality rate in infancy, childhood and adulthood. We review the pediatric mortality data provided by Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) and show that for causes of respiratory infant death that are apparently independent of gender (e.g., suffocation from inhalation of food or other object), there is a consistently one-third lower rate of mortality in the female than in the male. This one-third lower mortality for causes of death with a respiratory terminal event is hypothesized to be due to an X-linked dominant allele that occurs with frequency 1/3. It appears as if a second X chromosome provides the one-third extra probability of protection afforded for an XX female compared with an XY male. It is suggested that the allele's function is unmasked during transient periods of cerebral anoxia, requiring a mechanism for anaerobic oxidation to prevent the death of respiratory control neurons in the brain stem. Examples of the female one-third extra chance of resistance to hypoxia are given for causes of death in infancy, such as infant respiratory distress syndrome (IRDS) and sudden infant death syndrome (SIDS), and for causes of suffocation in childhood and asphyxiation in adulthood. DNA testing of the X chromosome of probands from causes of respiratory death, such as SIDS and IRDS, where there is a one-third lower female than male death rate, is a future direction that can verify the existence of the proposed allele.

Centers for Disease Control and Prevention, U.S.↗

Child injury deaths: comparing prevention information from two coding systems.

OBJECTIVES: The International Classification of Disease (ICD) external cause of injury E-codes do not sufficiently identify injury circumstances amenable to prevention. The researchers developed an alternative classification system (B-codes) that incorporates behavioral and environmental factors, for use in childhood injury research, and compare the two coding systems in this paper. METHODS: All fatal injuries among children less than age five that occurred between January 1, 1992, and December 31, 1994, were classified using both B-codes and E-codes. RESULTS: E-codes identified the most common causes of injury death: homicide (24%), fires (21%), motor vehicle incidents (21%), drowning (10%), and suffocation (9%). The B-codes further revealed that homicides (51%) resulted from the child being shaken or struck by another person; many fires deaths (42%) resulted from children playing with matches or lighters; drownings (46%) usually occurred in natural bodies of water; and most suffocation deaths (68%) occurred in unsafe sleeping arrangements. CONCLUSIONS: B-codes identify additional information with specific relevance for prevention of childhood injuries.

Child↗

Suicide by environmental hypoxia (forced depletion of oxygen).

Suicidal suffocation by forced oxygen depletion (environmental hypoxia) with carbon dioxide (CO2) and with propane is discussed in two cases. No toxicologic proof was available with the former and circumstantial evidence weighed heavily. The latter case demonstrated inhaled propane by an on-scene transthoracic aspirate; all other toxicology specimens, including brain, liver, blood, kidney, fat, and vitreous, did not contain hydrocarbons. This second fatality was complicated by multi-agent overdose, including diphenhydramine, fluoxetine (Prozac), and nordiazepam. The designation of these deaths as due to oxygen depletion involved careful scrutiny of the autopsy, toxicologic, and scene findings. Complete analysis of all factors surrounding these rarely encountered suffocation deaths is stressed.

Adult↗