Human Reproductive Sciences

http://www.jhrsonline.org/currentissue.asp?sabs=n

From the editors desk Madhuri Patil Journal of Human Reproductive Sciences 2018 11(4):303-305

Preimplantation genetic testing: Its evolution, where are we today? Firuza Rajesh Parikh, Arundhati Sitaram Athalye, Nandkishor Jagannath Naik, Dattatray Jayaram Naik, Rupesh Ramesh Sanap, Prochi Fali Madon Journal of Human Reproductive Sciences 2018 11(4):306-314 Preimplantation genetic testing (PGT) is an early form of prenatal genetic diagnosis where abnormal embryos are identified, thereby allowing transfer of genetically normal embryos. This technology has become an integral part of Assisted Reproductive Technology (ART) procedures. Initial experiments with animals as early as 1890 and those in the mid and later part of the last century paved the forward path of ART and PGT. This review article covers the evolution of PGT and is a pointer toward current and fast-evolving technology, allowing scientists and doctors to better comprehend human reproduction, and ensure healthy pregnancy outcomes.

Psychosocial aspects of therapeutic donor insemination Ansha Patel, P. S. V. N. Sharma, Pratap Kumar Journal of Human Reproductive Sciences 2018 11(4):315-319 The experience of delays in conception or possibility of remaining childless has the potential to create considerable psychological discomfort. In couples with severe male factor infertility, therapeutic intrauterine insemination using donor sperms (TDI) is offered as a treatment, second to in vitro fertilization using donor sperms. TDI is lucrative, less invasive, and a hopeful treatment. However, there are intricacies associated with it. Its immediate outcomes involve limited success rates, nonresponse, and chances of implantation failures, miscarriages, and multifetal pregnancies. Due to this, couples experience distress when they are advised to undergo three to six cycles of TDI in order to meet the expectations of having a baby. TDI has long-term issues on the triad comprising the “recipients,” the “donors,” and the “the children born out of TDI.” Nevertheless, managing psychosocial needs for couples undergoing TDI and other treatments in Indian clinics are grey areas of the conventional treatment pathway. The present review expands on the psychological issues and needs in couples opting for TDI.

"In cycles of dreams, despair, and desperation:" Research perspectives on infertility specific distress in patients undergoing fertility treatments Ansha Patel, P. S. V. N. Sharma, Pratap Kumar Journal of Human Reproductive Sciences 2018 11(4):320-328 “Emotional distress in infertility” is a broad expression that loosely denotes anxiety, depression, grief, crisis, depleting psychological well-being, and all forms of affective and interpersonal disturbances faced by individuals with infertility. The distress is usually associated with involuntary childlessness as it is an unwelcoming event. The developmental crisis associated with childlessness poses a threat to one's sense of self at all levels (individual, family and social). Distress may begin before or during treatments as a person experiences the loss of control over attaining parenthood, anxiety or dejection after the diagnosis, treatments, its complications particularly its limited success rates. This paper reviews the basic concepts, theoretical models related to infertility specific distress (ISD). It elaborates on the effects of individual and treatment-specific variables on ISD with special highlights gathered from the national and international research.

Examination of Y-chromosomal microdeletions and partial microdeletions in idiopathic infertility in East Hungarian patients Attila Mokánszki, Anikó Ujfalusi, Éva Gombos, István Balogh Journal of Human Reproductive Sciences 2018 11(4):329-336 Purpose: The aim of this study was to establish the Y chromosome microdeletion and partial AZFc microdeletion/duplication frequency firstly in East Hungarian population and to gain information about the molecular mechanism of the heterogeneous phenotype identified in males bearing partial AZFc deletions and duplications. Materials and Methods: Exactly determined sequences of azoospermia factor (AZF) region were amplified. Lack of amplification was detected for deletion. To determine the copy number of DAZ and CDY1 genes, we performed a quantitative analysis. The primers flank an insertion/deletion difference, which permitted the polymerase chain reaction products to be separated by polyacrylamide gel electrophoresis. Statistical Analysis Used: Mann–Whitney/Wilcoxon two-sample test, Kruskal–Wallis test, and two-sample t-probe were used for statistical analysis. Results: AZFbc deletion was detected only in the azoospermic cases; AZFc deletion occurred significantly more frequently among azoospermic patients, than among oligozoospermic males. The frequency of gr/gr deletions was significantly higher in the oligozoospermic patients than in the normospermic group. The b2/b3 deletion and partial duplications were not different among our groups, while b1/b3 deletion was found only in the azoospermic group. In infertile males and in normozoospermic controls, similar Y haplogroup distribution was detected with the highest frequency of haplogroup P. The gr/gr deletion with P haplogroup was more frequent in the oligozoospermic group than in the normozoospermic males. The b2/b3 deletion with E haplogroup was the most frequent, found only in the normozoospermic group. Conclusions: Y microdeletion screening has prognostic value and can affect the clinical therapy. In case of Y chromosome molecular genetic aberrations, genetic counseling makes sense also for other males in the family because these types of aberrations are transmittable (from father to son 100% transmission).

A study on balanced chromosomal translocations in couples with recurrent pregnancy loss Pritti K Priya, Vineet V Mishra, Priyankur Roy, Hetvi Patel Journal of Human Reproductive Sciences 2018 11(4):337-342 Background: Recurrent pregnancy loss (RPL) is an obstetric complication that affects couples in their reproductive age. Chromosomal abnormalities, mainly balanced rearrangements, could commonly be present in couples with RPL. Aim: The purpose of this study is to evaluate the contribution of chromosomal abnormalities and balanced reciprocal translocations, in particular occurring in either of the partners, resulting in RPL. Materials and Methods: A retrospective cytogenetic study was carried out on 152 individuals (76 couples) having a history of RPL. The cases were analyzed using G-banding and fluorescence in situ hybridization, wherever necessary. Results: Chromosomal abnormalities were observed in 3.2% of the total RPL cases, of which balanced translocations were observed in 4 (80%) individuals and marker chromosome was detected in 1 (20%) individual. All balanced translocations comprised reciprocal translocations, and no cases of Robertsonian translocations were detected in our study. Among reciprocal translocation carriers, three were male and one was female. Polymorphic variants were noted in 8 (5.3%) individuals. Conclusions: Chromosomal analysis is an important etiological investigation in couples with RPL. Balanced translocations are the most commonly detected chromosomal abnormalities in such couples. Thus, these couples are the best candidates for offering prenatal genetic diagnosis, thereby ensuring a better reproductive outcome.

Circulating levels of vitamin D3 and leptin in lean infertile women with polycystic ovary syndrome Ayman Shehata Dawood, Adel Elgergawy, Ahmed Elhalwagy Journal of Human Reproductive Sciences 2018 11(4):343-347 Objective: The objective of this study is to measure levels of Vitamin D3 and leptin and assess their relation of each to the pathogenesis of polycystic ovary syndrome (PCOS). Design: This was a cohort observational study. Settings: This study was conducted at the Department of Obstetrics and Gynecology, Tanta University. Materials and Methods: Ninety lean women were enrolled in this study and were allocated into two groups with 45 patients in each group: the first group (study group) who are lean women with PCOS and the second group (control group) who are the lean infertile patients without PCOS. Blood samples were collected and tested for study parameters. Results: There were no significant differences regarding demographic characteristics between both groups. The differences were in ovarian volume and hormonal profiles. Serum leptin was found to be significantly increased in lean PCOS than in control groups. Vitamin D3 levels were found to be lower in the lean PCOS group than in control group. Conclusion: Lean PCOS women are a unique group with specific hormonal profiles different from the typical PCOS profiles. Leptin and Vitamin D3 may have a role in the pathogenesis of lean PCOS, but large studies are still required regarding this unique group.

Effect of insulin sensitizers on raised serum anti-mullerian hormone levels in infertile women with polycystic ovarian syndrome Neeti Chhabra, Sonia Malik Journal of Human Reproductive Sciences 2018 11(4):348-352 Context: Increased circulating insulin levels contribute to hyperandrogenism in polycystic ovarian syndrome (PCOS) which causes a derangement in folliculogenesis, thus contributing to polycystic morphogenesis of the ovaries and a higher than normal anti-Mullerian hormone (AMH). A high AMH is an indicator of either stubborn anovulation or a predictor of ovarian hyperstimulation syndrome. Hence, it is postulated that the use of insulin sensitizers will reduce insulin resistance, hyperandrogenism, and subsequently serum AMH levels and will convert anovulatory cycles to ovulatory. Aim: To study the effect of insulin sensitizers on raised serum AMH levels in infertile women with PCOS. Settings and Design: This was a prospective interventional randomized single tertiary center study. Methodology: The study was conducted from August 2015 to April 2016. Infertile patients with PCOS as defined by the Rotterdam criteria with raised AMH (>5 ng/ml) levels were enrolled in the study under strict inclusion and exclusion criteria. The sample size was 105 patients. Cycle regularity, day 2–antral follicle count (AFC), luteinizing hormone, AMH levels, modified Ferriman–Gallwey score (mFGS), and acne score were recorded before starting the intervention. Patients were randomized into three equal groups of 35 each. Group A received metformin alone, Group B metformin plus myoinositol, and Group C only myoinositol. After completion of 3 months of pretreatment, the same parameters were rechecked. Statistical Analysis Used: Univariate analysis and Chi-square test were used for statistical analysis. Results: Of 105 patients, 95 completed treatment and the rest 10 dropped out. There was a reduction in AMH in all groups of insulin sensitizers with significant fall in the metformin only group. Cycle regularity, reduction in AFC, mFGS, and grade of acne were also obtained. Conclusions: Therapy with insulin sensitizers in PCOS women with raised AMH reduces the AMH levels, converts irregular menstrual cycles to regular, and reduces clinical hyperandrogenism.

Window of implantation is significantly displaced in patients with adenomyosis with previous implantation failure as determined by endometrial receptivity assay Nalini Mahajan, Simrandeep Kaur, Maria Ruiz Alonso Journal of Human Reproductive Sciences 2018 11(4):353-358 Background: Adenomyosis is associated with implantation failure and poor reproductive performance in IVF/ICSI cycles. Aims: To compare if window of implantation (WOI) is displaced in patients having adenomyosis compared to controls using endometrial receptivity array (ERA) test. Settings and Design: Retrospective Case control study. 374 patients with previous one or more IVF failures who underwent ERA test between 2013-2016 at our centre were enrolled. Patients were divided into two groups; Group A-36 patients with adenomyosis (study group) and Group B- 338 patients without adenomyosis (controls). Statistical Analysis: Normality assumptions for continuous variables were tested using Kolmogorov Smirnov test. Mean values of two groups were compared using Student's t-independent test. Frequency data by categories were compared using Chi-square/Fisher's exact test. Risk ratio and 95% confidence limits were calculated. P < 0.05 was considered for statistical significance. Results: WOI was displaced (Non Receptive ERA) significantly in adenomyosis 47.2% (17/36) compared to controls 21.6% (73/338) (P < 0.001, CI-8.7%-42.5%) making risk ratio of displaced WOI in adenomyosis versus controls to be 2:1. The incidence of RIF was 66.6% in adenomyosis compared to 34.9% in controls (P < 0.001, CI- 15.5%-47.9%). Pregnancy rate after personalized embryo transfer in adenomyosis group was 62.5%, signifying displaced WOI as a cause of implantation failure in adenomyosis patients with previous implantation failure. Conclusions: Our study suggests it is prudent to evaluate Endometrial receptivity before embryo transfer in patients with adenomyosis to avoid wastage of good embryos.

Knowledge about age-related decline in fertility and oocyte cryopreservation: A national survey Karissa C Hammer, Alyssa N Kahan, Louis F Fogg, Mark A Walker, Jennifer E Hirshfeld-Cytron Journal of Human Reproductive Sciences 2018 11(4):359-364 Context: Women worldwide are delaying childbearing, but are they aware of the age-related decline in fertility? Aims: The aim of this study is to investigate awareness of age-related decline in fertility and oocyte cryopreservation. Settings and Design: A primary analysis of a cross-sectional electronic survey with a nationally representative sample of nulliparous women aged 25–45 years. Subjects and Methods: A national online survey performed March 4–March 9, 2016. Statistical Analysis Used: A linear regression model and ANOVA tests were performed. Results: A total of 1213 women completed the survey. A significant difference was discovered in fecundity knowledge between women who identified as in a partnership compared to those who did not. Partnered women were more likely to respond “know a lot” about the age-related decline in fertility, whereas unpartnered women were more likely to respond “never heard of it” (P < 0.01). Partnered women are also more likely to respond that they would have made different life choices had they been more knowledgeable about fertility at a younger age (P = 0.01). The majority of the survey population had heard of oocyte cryopreservation but did not know much about it. Conclusions: Slightly over half of participants had an understanding of the natural age-related decline in fertility. Having a partner significantly increased the likelihood that a woman reported more knowledge about fertility. More effort is necessary to educate all women on assisted reproductive technologies and the natural age-related decline in fertility, specifically single women of childbearing age.

Atypical Asphysia

http://www.jfsmonline.com/article.asp?issn=2349-5014;year=2018;volume=4;issue=4;spage=233;epage=237;aulast=Cao

Forensic investigation of atypical asphysia

Zhe Cao¹, Zhiyuan An², Xiaoning Hou¹, Dong Zhao^3
1 Anshan Public Security Bureau, Anshan, China
² Key Laboratory of Evidence Science (China University of Political Science and Law), Ministry of Education, China, Collaborative Innovation Center of Judicial Civilization, China
³ Key Laboratory of Evidence Science (China University of Political Science and Law), Ministry of Education, China, Collaborative Innovation Center of Judicial Civilization; Key Laboratory of Forensic Genetics of Ministry of Public Security, Institute of Forensic Science, Ministry of Public Security, Beijing, China

Correspondence Address:
Dr. Dong Zhao
25 Xitucheng Road, Haidian, Beijing 100088 
China

Abstract

Smothering, choking, confined spaces, traumatic asphyxia, positional asphyxia, and other kinds of atypical mechanical asphyxia are not rare in forensic practice. However, these are not commonly well demonstrated in forensic monographs worldwide. The authors researched related works and literatures and summarized these with a view to contribute to the existing teaching resources and provide help to forensic practitioners who are involved in scene investigation and identification of such deaths.

Keywords: Asphyxia, forensic pathology, forensic medicine

Introduction

Death caused by compression of the neck, such as from hanging, strangling, or throttling, is termed "mechanical asphyxia" and usually has obvious physical findings. However, asphyxias that result from no direct pressure on the neck vessels or trachea, lack typical morphological changes, or result in minimal damage are called "subtle asphyxias"^[1] or "atypical mechanical asphyxias," used in this article. Atypical mechanical asphyxias include smothering, choking, environmental hypoxia, traumatic asphyxia, and positional asphyxia, among others.

Smothering

Smothering is a form of asphyxia death caused by obstructing the mouth and nose with hands, airtight papers, soft textiles, or the weight of one's own head.^[2]

Smothering can be seen in homicidal or suicidal cases. Homicidal smothering is common in infants, older adults, and people who are unconscious or have restricted motion due to fabric bundling, disease, poisoning, or intoxication. Homicidal smothering can also result when there are significant physical power differences between a perpetrator and victim.^[3],[4],[5] Suicidal smothering is common in psychiatric patients; an example includes wrapping tape around one's mouth, nose, or the entire face.^[6] Smothering can also occur accidentally. For example, adults who are unconscious or paralyzed because of drunkenness, epilepsy, drug overdose, or having another disease might accidentally asphyxiate themselves. Similarly, for an infant lying face down on an airtight mattress or pillow, the weight of the infant's head might obstruct, distort, and occlude his or her mouth and nose, leading to suffocation. In a third example, sleeping infants with clothes or bedding covering their faces are at an increased risk of suffocation.^[1],[2]

In general, it is difficult to identify a case of smothering during forensic scene examination because physical findings are nonspecific.^[7],[8] If smothering is suspected, there may be local signs of pressure on the face.^[2],[3] In adults, with even slight resistance, signs include skin exfoliation from fingernails; contusions on the nose, cheeks, or chin from fingers; bleeding and skin tears corresponding to the teeth in the oral mucosa; and intramuscular bleeding at the mandibular margin. Nasal deformation is also considered a sign of smothering, but can be caused by emergency tracheal intubation.^[3],[5],[7] In infants and adults who are unable to physically resist during asphyxiation, physical damage is difficult to detect.^[3] Of note, a body in the prone position concentrates pressure on the face, preventing accumulation of blood into the compressed skin around the mouth and nose, leading to the formation of distinct pale areas caused by the absence of pooled blood. It is, therefore, important not to assume that pale areas such as these have resulted from indentation by smothering.^[2]

Without positive physical findings in smothering cases, scene investigation plays a decisive role. Pillows and bedding should be examined for blood or lipstick.^[5],[9] For suspected cases of smothering, even if postmortem changes are obvious, suspicious skin lesions should be biopsied for histological examination.^[5] In cases of smothering by textiles, the mouth, nasal cavity, and airways should be examined for inhaled fabric fibers. Fibers in the trachea indicate that a patient may have been alive during smothering.^[8]

Gagging generally involves placing fabric in a victim's mouth to prevent yelling; the fabric gradually becomes soaked with saliva, and if airtight, will lead to suffocation. Another form of gagging involves placing tape over the mouth or nose, which results in trapped mucus production that eventually leads to suffocation. Obstruction of the nasopharynx by objects in the oral cavity may also lead to gagging and subsequent death.^[2] Usually, suspected gagging is confirmed when blocking objects are found, not by any specific physical signs of asphyxia.^[3]

Choking

Choking refers to upper respiratory tract blockage by a foreign body leading to suffocation. The foreign body is usually lodged between the larynx and trachea.^[10],[11] Death may result from simple hypoxia; however, many deaths occur quickly before the onset of hypoxia. Studies have found that, even in cases in which the airway is not completely blocked, death often occurs, likely from neurogenic-induced cardiac arrest.^{[2],[9],[11],[12]}

Choking is almost always accidental, with cases of homicide and suicide relatively rare.^[1],[11] For infants, accidental choking most often occurs with foreign body ingestion; for adults, choking most often occurs with food.^[1],[11] Victims in homicidal choking cases are most likely to be older adults, infants, young children, people who are unconscious, or persons debilitated by illness or intoxication. Suicidal choking most often occurs in patients with psychosis or prisoners in jail.^[1]

Evidence of coughing helps eliminate choking as a cause of death because it signifies that the respiratory tract was open during upper respiratory blockage.^[3] Computed tomography imaging can provide information before an autopsy on the location of a foreign body and can help inform an autopsy plan.^[13] Few physical findings are generally seen in choking deaths, so the discovery of a foreign body in the airway, a detailed clinical history, descriptions of the death environment and any resuscitation attempts, and exclusion of other causes of death are critical when forming a conclusion.^{[1],[9],[11],[12]} If the foreign body shifts during resuscitation or otherwise is moved, clinical history might be the only evidence.^[3],[13]

Foreign bodies blocking the airway leading to choking generally belong to the following categories.^[2]

Foreign objects

Attackers may put a towel or sock into the victim's mouth to prevent shouting; this can cause choking and gagging.^[3] In another example, people may inhale sand, piles of gravel, or piles of soil when they fall on them, causing respiratory blockage and resulting in choking death. This scenario may occur accidentally at a construction site, during a traffic accident, or in children playing in or eating sand.^[3],[14]

Acute obstruction

Acute allergy, steam stimulation, heat inhalation, and acute inflammation may cause swelling of the throat organs, including the epiglottis, tonsils, or glottis, leading to choking. Trauma in the anterior or lateral cervical neck structures can also result in severe swelling of the respiratory tract from bleeding and edema.^[1],[2],[7] Tumors, polyps, or cysts can also block respiration, leading to choking.^{[1],[10],[11]}

Foods

The most common foreign bodies causing choking death in adults are foods.^[10] Susceptible factors include old age, neuromuscular disease, poor dentition leading to chewing problems, consumption of alcohol or other central nervous system depressants weakening the gag reflex, or other neurological or mental illness (of which poor dentition is an important risk factor).^{[1],[11],[12],[13]} Of patients with mental illness, those with schizophrenia are most likely to choke on food, possibly from a propensity to swallow incompletely chewed food.^[11] The majority of adult choking cases occur at patients' homes, nursing homes, or mental hospitals, and often take place suddenly during meals.^[1]

When a sudden death occurs while eating or soon after, the possibility of choking must be considered. A search for a blocked airway should be initiated, but in addition, the investigator should also consider factors that could have aggravated the choking episode. Therefore, quality and number of teeth, food debris in the esophagus – which can cause tracheal obstruction from the external oppression – and exclusion of neurological diseases and intoxication are all important when evaluating sudden death during a meal.^{[1],[9],[11],[12]}

It is typical for gastric contents to be present in the throat, trachea, and bronchi after death, caused by reflux or shifting of contents. This is a common postmortem phenomenon, found in 20%–25% of routine examinations. As a result, if a small amount of gastric content is found in the respiratory tract, this does not mean that choking had occurred; however, if the throat or airway is completely blocked by gastric contents, choking can be concluded.^[2],[3],[13] The inhalation of gastric contents is more common in people who are unconscious.^[1]Importantly, there is no reliable way to distinguish natural food reflux early in the dying process from true inhalation while alive, unless the inhalation occurred during a clinical procedure or another person witnessed the event. In most cases, in the absence of hard evidence, it is unreasonable for forensic officers to conclude that the inhalation of gastric contents is secondary to choking death.^[2]

Environmental Hypoxia

Environmental asphyxiation is usually caused by a lack of oxygen in the local environment,^[1],[2],[3] and is almost always accidental. Oxygen deficiency can occur secondary to breathing exercises, microbial consumption, activities related to industrial work (such as welding), environmental chemical reactions (such as rust), absorption by chemical substances (such as activated carbon), and presence of toxic gases (such as propane, nitrogen, and methane).^[1],[2],[3] An atmospheric oxygen concentration below 5%–10% will cause death in a few minutes, and a concentration of carbon dioxide higher than 10% is lethal.^[1] In some cases, death occurs before the onset of hypoxia, and is secondary to overexcitement of the body's chemical sensing system, which causes parasympathetic nervous system-mediated cardiac arrest.^[2]

In hypoxia-asphyxia deaths caused by low atmospheric oxygen levels, physical findings are usually absent,^[2] making elucidation of the specific cause of death difficult. Investigators must carefully analyze the environment and exclude other causes of death to conclude environmental hypoxia-asphyxia.^[3] Measurements of toxic gases and oxygen concentrations in the air, as well as postmortem analysis of blood and tissues, should be performed; in addition, scene simulations may be required.^[1]

As a type of environmental hypoxia-asphyxia, plastic bag suffocation is often used as a suicide technique in Western countries. This method is common in young men and elderly women.^[15] Some people even use the propane, ether, or helium gas along with the plastic bag. Plastic bag suffocation deaths can also occur accidentally or unexpectedly, such as during sexual asphyxia, children playing with plastic bags, and other occurrences.^[1] It is very rare for the use of plastic bags to result in death; however, it is more likely in cases in which the victim is unconscious, or when there is a large difference in strength between the perpetrator and victim.^[16]

Plastic bag suffocation often occurs rapidly with few physical signs;^[1],[2] however, in a small number of cases, marks on the neck are present corresponding to the areas of bag bundling (such as from a rubber band), or there may be signs of prior injury, such as wrist cutting or abuse.^[1],[2] It is a common misconception that the postmortem presence of moisture in the plastic bag confirms that the bag was placed on a breathing human; water droplets form as gas evaporates from the skin, nose, and mouth even if the person was previously deceased.^[2]

Because there are usually no specific physical findings, it is difficult to identify cases of plastic bag suffocation unless the bag is over the head at the time of scene investigation or autopsy.^[2] If the plastic bag is removed before forensic workers see the corpse, they will not be able to determine the cause of death through forensic examination, and may even conclude that a natural death occurred. Therefore, to identify such cases, forensic workers must pay careful attention during scene exploration and investigation.^{[1],[3],[9],[16]} If necessary, forensic workers can conduct simulations under close monitoring in a protected environment, which can help to pinpoint a cause of death through analysis of time measurements.^[4],[6],[17] Specimens collected from the blood, lungs, liver, or other organs for poison analysis should be extracted and stored in a sealed empty bottle along with a plastic bag,^[2],[7],[16] frozen, and delivered promptly.^[1]

Traumatic Asphyxia

Traumatic asphyxia refers to the compression of the chest or abdomen by massive mechanical forces resulting in thoracic fixation – expansion of thoracic and lower phrenic muscles – leading to respiratory disturbance and death by asphyxiation.^[2]

Traumatic asphyxia is common in the following types of accidents: motor vehicle compression or extrusion during traffic accidents; pinning from building collapse, falling rocks, or other objects; trampling by a crowd; compression while standing in a crowded population from sudden external forces; compression by fallen tools or furniture; and compression of infants and children while sleeping with parents (overlaying asphyxia).^[1],[2],[18] There are also reports of homicide resulting from a perpetrator kneeling or sitting on the chest of a victim.^[19]

The pathological features of traumatic asphyxia are usually quite specific. These include prominent facial and nuchal hyperemia and swelling; numerous petechial hemorrhages on the face or conjunctiva; subconjunctival hemorrhage and edema; and nasal bleeding. In general, a person who dies from traumatic asphyxiation often appears strangled with features extending down to the neck, with no signs of local damage.^{[2],[20],[21]}

However, physical features such as these are not always visible. Studies have shown that, in up to 10% of cases, no petechial hemorrhages are seen on the face or conjunctiva. The reason for this is unclear, but may be related to rapidness of death, lack of obvious chest compression or vagus nerve stimulation, lack of occlusion of the epiglottis, or concurrence of both left heart and right heart impairment at the time of chest compression.^{[1],[18],[20],[21]} On gross examination, lungs may have a purplish red color, congestion, or subserous bleeding with or without obvious expansion of the right heart or superior vena cava; sometimes, there is no evidence of trauma despite severe direct external compression on the chest and abdomen.^{[1],[2],[3],[9]}

Traumatic asphyxia is a diagnosis of exclusion. In addition to supporting evidence from a scene investigation, suffocation death should only be considered after excluding fatal injuries and poisoning.^[1],[9],[21]

Overlaying asphyxia is a special form of traumatic asphyxia, often secondary to nasal compression. Physical examination findings are usually absent, so overlaying can be difficult to determine unless the same-bed sleeper admits to crushing the infant or child. Overlaying asphyxia is sometimes attributed to sudden infant death syndrome, so it is important to examine adults' and children's clothes and bedding carefully as well as the scene.^[1],[3],[22]

Positional Asphyxia

Positional asphyxia refers occurrences in which respiration is compromised from splinting of the chest or diaphragm preventing normal respiration, or occlusion of the upper airway due to abnormal positioning of the body.^[23] Positional asphyxia is almost always an accident, during which the victim cannot extract himself or herself from a specific position or small space. The victim may be further impaired by alcohol or drug intoxication, weakness, neurological disease, or fabric bundling. Common examples of positional asphyxia include limbs tied behind the back while in a prone position (may be performed for restraint by police or psychiatrists for suspects or patients); head-down position (inversion of the body, or head hanging down off the edge of a bathtub); jack-knife position (upper body significantly curved from the waist down); bundled thoracic or abdominal horizontal sling (e.g., a young girl wearing a belt hanging by the abdomen on a swing); excessive flexion or extension of the neck (e.g., during a motor vehicle accident); lack of chest wall expansion in a restricted space (wedging); and a person sandwiched between the wall and the mattress after falling off the bed.^{[1],[2],[3],[4],[5],[6],[7],[24]} A typical case of postural asphyxia involves a drunken person who collapses into a narrow space, excessively distorting the neck and hindering breathing, leading to death.^[9]

Cause of death from positional asphyxia often results from reverse suspension of the body such that the movement of the chest wall is restricted by intra-abdominal organs compressing the diaphragm. This prolongs inspiration, and eventually results in respiratory muscle fatigue, leading to slowed movement of the chest wall and subsequent hypoxia. Venous return is effectively limited, and blood flow to the brain is shifted, decreasing blood flow and further aggravating respiratory muscle fatigue; eventually, the heart stops.^[1] Positional asphyxia does not require reversal of the entire body; fatal asphyxia may result from the reversal of torso position, excessive flexion of the neck, or pressure on one's face, such as in an intoxicated person whose face is pressed to the floor.^[25] The difference between traumatic asphyxia and positional asphyxia is whether the chest and abdomen are compressed by external forces. If chest compression is from an external source, he or she should have been died from traumatic asphyxia. If a deceased person is found in a specific position or restricted space that limits chest activity, the person should have been died from positional asphyxia.^[1],[23]

Positional asphyxia can be identified by the following criteria: The body position is consistent with restricted or disordered respiration; scene investigation or historical investigation identifies that an accident had occurred; the deceased person cannot change his or her position for some reason; and other obvious natural or violent causes of death are excluded. A diagnosis of accidental positional asphyxia mainly depends on the evidence obtained from the scene environment.^[24],[25] Some forensic investigators believe that, if another disease is present, then either the cause of death is not associated with positional asphyxia, or the onset of the disease makes the deceased patient prone to positional asphyxia.^[23] It should be noted that alcohol consumed by a patient with positional asphyxia may be metabolized. Thus, even if the concentration of alcohol in the blood or urine is very low or negative, the possibility of positional asphyxia cannot be ignored.^[24]

Wedging is a special form of positional asphyxia, commonly seen in infants and young children whose body or head are compressed in a narrow space. The chest wall is fixed, resulting in airway obstruction that results in asphyxia. Wedging usually occurs between a mattress and wall or mattress and furniture or baby crib. It is most common in infants aged 3–6 months, intoxicated adults, or comatose patients who accidentally fall between a mattress and wall, leading to death. Physical findings of wedging are usually absent.^[1],[22]

Acknowledgments

This study was supported by the Open Project of Key Laboratory of Forensic Genetics, Ministry of Public Security (2017FGKFKT05), Program for Young Innovative Research Team from China University of Political Science and Law (2016CXTD05), and Project of Interdisciplinary Science Construction-Forensic Psychology from China University of Political Science and Law.