Asphyxia is generally accompanied by ‘dyspnoea’, i.e. the sensation of laboured breathing described by patients as ‘air hunger’.
Prolonged suffocation leads to hypoxemia and hypoxia, i.e. a lack of oxygen in the blood and tissues, which mainly affects the tissues and organs most sensitive to oxygen deficiency, such as the brain (cerebral hypoxia).
If the hypoxia is prolonged, the tissues stop functioning and a series of sequential events quickly occur: loss of consciousness, irreversible brain damage, coma and death of the patient; even if death does not occur, the severe cerebral hypoxia could still lead to necrosis (death) of the nerve tissue, with possible severe and irreversible motor and/or sensory damage.
Interestingly, the need to breathe is induced by increasing levels of carbon dioxide in the blood rather than by too low levels of oxygen.
Sometimes the level of carbon dioxide is not sufficient to induce ‘air hunger’ and the subject becomes hypoxic without realising it.
Table of Contents
There are three main causes of suffocation
- the presence of intrinsic or extrinsic airway obstruction;
- the absence of adequate oxygen concentration in the environment;
- the presence of chemical or psychological interference.
There are various causes that can prevent gases from passing through the airways, creating mechanical barriers in them.
These obstructions can be intrinsic (the obstruction is internal to the airway) or extrinsic (the obstruction is external to the airway but comes to strongly compress it).
The most common causes of mechanical obstruction are:
- compression of the chest or abdomen (compressive or compression asphyxia, see appropriate section);
- obstruction of the external airways;
- presence of food or foreign bodies in the larynx or trachea;
- strangulation (sometimes performed to increase sexual arousal);
- airway constriction due to bronchial asthma or anaphylactic shock;
- aspiration of vomit (typical in children and drug users).
Outside air alteration
Suffocation can result from prolonged exposure to an atmosphere containing too low a concentration of oxygen, which occurs in various situations, such as
- loss of pressurisation in the cabin of an aircraft. The pressure inside commercial aircraft is maintained at that equivalent to 6000 ft (1800 m), but a failure of the pressurisation system can bring the internal pressure back up to that outside;
- when workers descend into a sewer or the hold of a ship containing gases without oxygen and heavier than air, usually methane or carbon dioxide;
- in the case of reckless use of a closed-circuit underwater rebreather where the recirculated breathing air contains insufficient oxygen.
An extreme example of suffocation is that caused by exposure to the vacuum of space, as happened in the case of the decompression of the Soyuz 11 spacecraft on 29 June 1971, the day when for the first and only time human beings unfortunately died in the vacuum of space.
Chemical or psychological interference with breathing
Various chemical and psychological situations can interfere with the body’s ability to absorb and use oxygen or regulate oxygen levels in the blood:
- inhalation of carbon monoxide, e.g. from the exhaust of a car, carbon monoxide has a high oxygen-like affinity for haemoglobin in red blood cells, so it binds strongly with haemoglobin, replacing the oxygen it should normally carry within the body;
- contact with chemicals, including pulmonary agents (such as phosgene) and blood agents (such as hydrogen cyanide);
- self-induced hypocapnia through hyperventilation, such as in shallow or very deep water or in sexual games involving asphyxiation;
- a respiratory crisis that stops normal breathing;
- obstructive apnoea during sleep;
- overdose resulting from drug use;
- central alveolar hyperventilation syndromes;
- acute respiratory distress syndrome.
Compression asphyxia (or suffocation)
Compression asphyxia (also called ‘compression asphyxia’ or ‘chest compression’) refers to the restriction of lung expansion by compression of the torso, which interferes with breathing.
Compression asphyxia occurs when the chest or abdomen is compressed
In accidents, the term ‘traumatic asphyxia’ or ‘crush asphyxia’ is commonly used to describe the compression asphyxia of a subject who is crushed or pinned under a great weight or force.
An example of traumatic asphyxia is when a subject, while using a mechanical lever to repair a car, is crushed by the weight of the vehicle when the lever slips.
In fatal crowd-related disasters, such as the Heysel Stadium disaster, traumatic asphyxia is called ‘crowd compression’.
Contrary to popular belief, it is not blunt trauma that causes the vast majority of deaths in many cases, but rather compression asphyxia caused by trampling by the crowd: people at the bottom are literally trampled by other individuals, preventing the former from expanding their chests necessary for proper breathing.
Neonatal asphyxia describes suffocation episodes occurring before, during and after birth, caused by various factors and pathologies, including:
- premature baby;
- early placental abruption from the uterus;
- maternal hypoxaemia (lack of oxygen in the maternal blood);
- long and complicated childbirth;
- umbilical cord difficulties;
- infections of baby and/or mother;
- maternal hypertension;
- high blood pressure in the mother;
- baby’s airway not well developed;
- baby’s airway obstructed.
In cases of neonatal asphyxia, it is vital to act early to reverse or at least reduce the damage caused to the baby by the interruption of oxygen supply:
- in cases of mild asphyxia, infants should be monitored and provided with respiratory support until they are breathing independently;
- in cases of severe asphyxia, mechanical ventilation, fluids and drugs are used.
Symptoms of suffocation
The main symptom of choking is an urge to breathe induced by increasing levels of carbon dioxide in the blood, i.e. dyspnoea.
Other signs and symptoms vary depending on the underlying cause of choking and may include:
- cyanosis (bluish skin and conjunctivae);
- violent or weak cough (if the subject cannot fill the lungs with air);
- the subject brings their hands to their throat;
- breathing may make noises;
- miosis (pupil constriction);
- bleeding from nasal mucosa and ear canal;
- arterial hypertension;
- altered respiratory rate;
- motor and/or sensory deficits;
- loss of consciousness;
- coma and death (in cases where breathing is not restored within a time frame usually ranging from 3 to 6 minutes).
Death by suffocation: signs, symptoms and timing
If suffocation, and therefore hypoxia, is prolonged over time, tissues stop functioning one after the other, starting with the brain (whose tissue is particularly oxygen-hungry) and a series of events, symptoms and signs occur rapidly in sequence
- loss of consciousness
- irreversible brain damage;
- death of the patient.
Death from suffocation is preceded by four stages:
1) Irritative or ‘respiratory dyspnoea’ stage: lasts from 30 to 60 seconds and is characterised by:
- tachypnoea (increased respiratory rate);
- arterial hypotension (‘low blood pressure’);
- cyanosis (bluish skin);
- miosis (narrowing of the pupil diameter of the eye).
2) Convulsive or ‘expiratory dyspnoea’ stage: lasts about 1 minute and is characterised by:
- severe dyspnoea (marked expiratory difficulty);
- arterial hypertension;
- high release of adrenaline into the circulation;
- obnubilation of consciousness;
- cerebral hypoxia;
- reduced motor reflexes;
- sensory alteration;
- sphincter release (faeces and/or urine may be involuntarily released).
3) Apnoic or ‘apparent death’ stage: lasts about 1 minute and is characterised by:
- progressive bradypnoea (progressive reduction in the frequency of respiratory acts);
- total loss of consciousness;
- muscle relaxation;
- severe bradycardia (slow and weak heartbeat);
- deep coma.
4) Terminal or ‘gasping’ stage: lasts approximately 1 to 3 minutes and is characterised by:
- continued loss of consciousness;
- slow and irregular respiratory movements;
- severe cardiac arrhythmia;
- cardiac arrest;
- cessation of breathing;
How quickly does one die?
The time in which death occurs is extremely variable depending on various factors such as age, state of health, state of fitness and mode of asphyxia.
An elderly person suffering from diabetes, hypertension and pulmonary emphysema, if subjected to a compressive force (e.g. strangulation) resulting in mechanical asphyxia, may lose consciousness and die in less than a minute, as can a child suffering from bronchial asthma.
An adult, fit individual, accustomed to prolonged exertion (think of a professional athlete or scuba diver), subjected to chemical asphyxia, such as that from carbon monoxide inhalation, may instead take several minutes to lose consciousness and die, however in the majority of cases death occurs within a variable time ranging from about 3 to 6 minutes, in which the 4 phases described in the previous paragraph alternate.
Treatment in cases of choking is to remove the upstream cause that prevents breathing, e.g. using the Heimlich manoeuvre or other foreign body removal techniques depending on the type of foreign body, its location and the age of the patient.