Suicide by air embolism introduced by means of a bicycle pump

Gas embolisms have a wide variety of etiologies. They are potentially life-threatening but rarely the cause of death. Fatal venous air embolisms can be caused by acute pathological alterations, diagnostic and surgical procedures [1‐3]. Some cases of air entering the venous blood system subsequent to incorrectly applied medical measures or in connection with defective intravenous infusion systems have been described [4‐8]. In medicolegal cases air embolisms can be found principally after blunt chest trauma and in connection with penetrating injuries, such as cuts and stab wounds especially to the head, neck and chest and even more rarely gunshot wounds.

Most of the cases observed, gas embolism was accidental. According to the literature [9], premeditated homicides through injection of air into the venous system are extremely rare, whereas a few cases of forced air injection in suicidal intention have been described. This article describes a case of suicide through air embolism induced by a bicycle pump.

Gas embolism usually occurs through the blockage of a blood vessel by a gas aggregation. It can affect the arterial as well as the venous branch of circulation. Circulatory arrest as a result of gas embolism can be caused by a massive embolism in previously healthy persons or in cases of pre-existing cardiac or pulmonary insufficiency, by decompensation and several smaller embolisms. The right ventricle is adapted to low pressures and has only limited ability to react to an acute increase of resistance in pulmonary vessels. As widely known the Italian anatomist Morgagni postulated even in the late eighteenth century that an increasing afterload of the right ventricle threatens the circulatory system by a lower ejection fraction, as well as a certain amount of gas in the right ventricle [44]. In addition, humorally and/or reflexively elicited vasoconstriction plays an important role. Lung segments affected by embolic obstruction are still ventilated but the alveoli do not participate in gas exchange, resulting in an increased dead space. The functionally disturbed balance between ventilation and perfusion leads to dyspnea and arterial hypoxemia. This hypoxemia can be partially explained through the opening of additional arteriovenous anastomoses [2, 10‐13].

Information on the quantity of gas in a fatal gas embolism varies in the literature. Most frequently, quantities of 70–130 ml are given to be fatal [10, 12, 13]. Some authors cite quantities of 10 ml and 70 ml gas as being fatal [14, 15], others described a rapidly injected gas volume of 100–300 ml or 3–5 ml/kg body weight as a fatal volume [16]. Acute amounts of 0.5–2 ml/kg body weight are attributed to cause inter alia myocardial and cerebral ischemia, hypotension and pulmonary hypertension [2]. Because no pathological alterations of the organs or evidence for an intoxication were found, the 50 ml of gas in the right ventricle was considered to be the cause of death.

Gas embolisms are more frequently described in connection to medical procedures like the use of rapid infusion systems, invasive vascular procedures and neurosurgical procedures [17] as with, for example, cuts or stab wounds [18, 19], gunshot wounds to the head [20, 21] or open craniocerebral injuries [22‐24]; however, gas embolism is not inevitable in these cases [25, 26]. Furthermore, gas embolism can occur in connection with medical malpractice [4‐8]. Most frequently, gas embolism is found in connection with inappropriate infusion therapies [4, 6, 8], endoscopic operations with air insufflation [18], surgery on large blood vessels, neurosurgery and orthopedic surgery [27] but also in faulty operation of dialysis equipment or during legal abortions [28, 29]. Furthermore, there are reports of sexual orogenital insufflation in pregnancy and also autoerotic practices that caused a fatal air embolism [30, 31].

Traditionally, a thorax radiograph is used as a non-invasive proof of gas embolism of the right ventricle. A transesophageal echocardiography is the most sensitive invasive monitoring device, the precordial Doppler ultrasound is the most sensitive noninvasive monitoring device [2, 32] and helical computed tomography (CT) [33] is also applied. In the present case, the gas embolism of the right ventricle was not reliably detected by radiography, probably because the volume of 50 ml air found using the aspirometer was too small. In addition, the small amount of blood was foamy, which might further have complicated radiological confirmation. There are various methods for detecting a gas embolism during autopsy: the test according to Richter [34] can be used as qualitative proof as bubbles would emerge after inserting the submerged right ventricle. An appropriate method for the quantification and collection of the gas is the method according to Bajanowski et al. using an aspirometer [10] as used in this case. Gas samples obtained by this method can be chemically analyzed [10, 35]. In the present case no analysis of the gas sample was performed because the autopsy was conducted just 22 h after the death and there were no signs of internal putrefaction. Moreover, it was assumed that the gas within the right ventricle was ambient air out of the bicycle pump.

Suicides through insufflation of air into the venous system have seldom been reported. There are a few cases described in which people connected an oxygen supply with tubes to a venous cannula to commit suicide [36‐38].

In one suicide case a man blew air through a system of tubes and a cannula into a vein in one arm [39], in another case an oral air insufflation is assumed in a patient in hospital after suicidal cutting of the veins of the wrist [40]. Another case describes a fatal air embolism of a man after cutting his varicose saphenous vein in apparently suicidal intention [41]. Moreover, one case is presented in which a man committed suicide by compressing a 2000 mL plastic bottle containing air linked to a system of tubes and a venous cannula with his body weight [42]. With respect to forensic cases, bicycle pumps in connection with air embolisms have usually been used in cases of illegal abortion [43]. To our knowledge, our case is the first in which a bicycle pump has been used to commit suicide by intentionally inflicted air embolism. The two puncture wounds on the back of the left hand were suitable as an entry point for air into the circulatory system.

The homemade system, an insulin cannula set into the valve of the bicycle pump, is capable of insufflating air into the venous system. The insulin cannula was slightly curved, maybe for an easier insertion of the needle. Apparently, the man had placed the bicycle pump on the back of the hand at a right angle, punctured the vein, and then pressed the plunger down. By reconstructing the case this procedure was possible if the man had pulled up the plunger before inserting the cannula into the vein. The existence of two puncture wounds indicated that he was not successful at the first attempt.