Asphyxia can literally be translated from the Greek as meaning 'absence of pulse', but is usually the term given to deaths due to 'anoxia' or 'hypoxia'.
The term 'asphyxia' is thought by some forensic pathologists to be a vague and confusing term. In its broadest sense it refers to a state in which the body becomes deprived of oxygen while in excess of carbon dioxide (ie. hypoxia and hypercapnoea). This results in a loss of consciousness and/or death. However, prior to any death the body usually reaches a low oxygen-high carbon dioxide state, and so an 'asphyxial' death is therefore one in which the oxygen deprived state has been achieved unnaturally.
When oxygen is not able to reach the lungs because of external occlusion of the mouth and/ or nose, or the airway at the level of the larynx is obstructed (eg by a bolus of food), the cause of the asphyxial death is 'obstruction of the airways'. There are no specific autopsy findings that would support the main types of airway obstruction deaths, and circumstantial evidence, physical evidence (eg plastic bags used by the deceased) and the scene of death would be relied on to support the diagnosis.
Exhaustion or Displacement of Environmental Oxygen (Suffocation)
This may occur in tight or confined spaces, where toxic fumes are released from bedding etc in cots, or in drowning (the inhaled water displaces the oxygen).
This is 'pure' asphyxia and results in a fairly rapid, painless loss of consciousness, followed by death if not discovered. There are no diagnostic autopsy findings.
Asthma
Asthma is a common disorder that accounts for almost 2 million visits to the Emergency department each year in the United States. On average, this represents approximately 2% of all ED visits. In urban centers, however, acute asthma may comprise up to 10% of all ED visits.
History: Specific historical factors are key in the assessment of acute asthma. The patient should be asked about the following aspects of their disease to help gauge the severity of this episode.
Precipitating factors may include the following:
Viral upper respiratory infection
Allergen exposure (dustmite, animal dander, mold)
Smoke inhalation
Change in weather
Current medications and compliance (eg, frequency of inhaled beta-agonist treatments, use and dose of inhaled corticosteroids)
Past asthma-related healthcare utilization, including both the frequency of events in last 12 months and the length of time since most recent event:
Systemic corticosteroids for an asthma exacerbation
ED visits for asthma exacerbation
Overnight hospitalization or other admissions for asthma exacerbation
ICU admission for severe asthma exacerbation
Endotracheal intubation
Duration of present symptoms (eg, hours to days): Duration of more than 2 days is associated with a higher admission rate than duration of less than 2 days. Sudden-onset exacerbations (ie, < 3 hours since symptom onset) tend to be more severe but also tend respond better to treatment in the ED and an inpatient setting.
Degree of dyspnea, cough, wheezing; whether new productive cough is present
Ask about a patient's baseline peak flow or personal best peak flow. Many patients know these values, and they can serve as a comparison against current peak flow and help set a goal for improvement in the ED.
The clinician should address whether the condition is truly asthma. Many other causes of dyspnea, cough, and wheezing exist and include the following:
Chronic obstructive pulmonary disease (COPD), which usually requires smoking more than 20 pack-years of cigarette smoking
Bronchopulmonary dysplasia, cystic fibrosis, sarcoidosis, or other pulmonary disease
History of heart disease (cardiac asthma)
Presence of chest pain or pleuritis, which may suggest a complication of more severe exacerbations
Physical:
Level of alertness
Ability to lie flat: Patients with mild acute asthma are able to lie flat. In more severe cases, the patient assumes a sitting position. As the severity increases, the patient increasingly assumes a hunched-over sitting position with the hands supporting the torso, termed the tripod position. If symptomatology becomes more severe, profuse diaphoresis occurs. The diaphoresis presents concomitantly with a rise in PCO2 and hypoventilation. In the most severe form of acute asthma, the patient may struggle for air and/or be bradypneic and be profusely diaphoretic; almost no breath sounds may be heard, and the patient is willing to lie recumbent.
Ability to speak/staccato speech
Stridor
Accessory muscle use - In children, also look for supraclavicular and intercostal retractions and nasal flaring as well as abdominal breathing.
Central cyanosis
Peripheral edema
Subcutaneous emphysema
Bilateral breath sounds
Wheezing: Inspiration-expiration ratio reveals prolongation of the expiratory phase (eg, 1:1 mild, 1:3 severe). Wheezing may be absent both during a severe presentation with very poor air exchange or in mild exacerbations. In a situation with mild exacerbation, request rapid forced expiration to see if a wheeze becomes audible.
Peak flow measurements: A peak flow value should be obtained early in the course of the ED visit to document severity as well as to serve as a baseline against which improvement may be measured.
Prehospital Care: Therapy for acute asthma can be initiated in the prehospital setting consistent with EMS providers' legally authorized scope of practice and local medical direction. The primary treatment approach is administration of supplemental oxygen and inhaled bronchodilators. The latter treatment most often involves inhaled beta2-agonists given by hand-held nebulizer or using a metered-dose inhaler (MDI) with spacer (holding chamber). If these delivery devices are not available, subcutaneous epinephrine or terbutaline can be given for severe exacerbations.
When initiating bronchodilator use, EMS personnel should not delay patient transport to the appropriate medical facility—which remains a high priority. If necessary, and again consistent with the scope of practice and local medical direction, bronchodilator treatments may be repeated while transporting patients. Prolonged transport times (eg, in rural settings or during transport on congested urban streets) may necessitate multiple bronchodilator treatments before arrival to the medical facility. To improve prehospital care, ambulance services are encouraged to develop protocols for the management of acute asthma in children and adults. Recently, a model protocol was developed by a CDC-funded workgroup to help advance this process.
Emergency Department Care:
The mainstay of ED therapy for acute asthma is inhaled beta2-agonists. The most effective particle sizes are 1-5 m. Larger particles are ineffective because they are deposited in the mouth and central airways. Particles smaller than 1 m are too small to be effective since they move in the airways by Brownian motion and do not reach the lower airways.
Standard delivery systems and routes are as follows:
Albuterol 2.5-5 mg every 20 minutes for 3 doses, then 2.5-10 mg every 1-4 hours as needed. Dilution of 2.5 mg in 3-4 mL of saline or use of premixed nebules is standard. Oxygen or compressed air delivery of the inhaled beta-agonists should be at a rate of 6-8 L/min. For children, use 0.15 mg/kg (minimum dose 2.5 mg) every 20 minutes for 3 doses then 0.15-0.3 mg/kg up to 10 mg every 1-4 hours as needed.
An equivalent method of beta-agonist delivery in mild-to-moderate exacerbations is the MDI used in conjunction with a spacer or holding chamber. For severe exacerbations, it is less clear if nebulized versus MDI/spacer delivery is truly equivalent. Each puff delivers a standard 90 mcg of albuterol. The dose is 4-8 puffs every 20 minutes up to 4 hours, then every 1-4 hours as needed. A potential advantage of the MDI/holding chamber is that it requires little or no assistance from the respiratory therapist once the patient understand how to use administer the medication; the patient can be discharged from the ED with the same spacer and albuterol canister. This modality is especially effective in areas where patients may be unable to afford their inhaled beta-agonists.
Continuous nebulization may be superior to the MDI/holding chamber method in a patient with severe exacerbations (eg, PEF <200 L/min). The dose of albuterol is 10-15 mg in 70 mL of isotonic saline. For children, this method is reserved for severe asthma at an albuterol dose of 0.5 mg/kg/h. Based on meta-analyses, there is no advantage of intravenous albuterol over inhaled albuterol, even in severe asthma. However, the role of parenteral beta-agonists in addition to inhaled beta-agonist treatments is uncertain.
In general, 3-4 hours in the ED is adequate time to determine if a patient with acute asthma has improved symptomatically and demonstrates pulmonary flow rates sufficiently improved for safe discharge. To allow time for corticosteroids to take effect, extended treatment in a clinical holding area has been demonstrated to be effective. Such observation units have avoided 60% of admissions to the hospital for acute asthma by treating and observing the patient for as long as 12 hours. These units are appropriate if nursing care and monitoring are adequate. They provide an excellent site for specialized asthma education.
Antibiotics should be administered only if bacterial sinusitis, bronchitis, or pneumonia is suspected clinically. Asthma exacerbation severity and therapeutic choices instituted should be evaluated according to the percent of predicted FEV1 or PEF. The 2002 National Asthma Education and Prevention Program (NAEPP) cutpoints are less than 50% (severe exacerbation), 50-79% (moderate exacerbation), and 80% or higher (mild exacerbation). Some experts believe that more appropriate cutpoints are less than 40% as “severe” (because that is the approximate percentage predicted where several adjunct therapies, such as continuous nebulization and intravenous magnesium, begin to work) and 70% or higher as “mild” (because that is the target PEF for discharge of patients from the ED).
Corticosteroids -- These anti-inflammatory agents have myriad effects, including restoration of beta2-agonist receptors in the bronchial smooth muscles and, therefore, improved response to beta2-agonists.
Corticosteroids are indicated in all patients with severe exacerbations and in the vast majority of patients with moderate exacerbations. If response to the first or second beta2-agonist inhaler treatment is incomplete, this too is an indication for corticosteroids in most patients.
Additional high-risk patients for whom corticosteroids may be recommended are those who require frequent ED visits, have been admitted with asthma exacerbations, have been intubated, are already on outpatient steroids, or have been experiencing an episode for longer than 2-3 days.
The onset of action of corticosteroids is approximately 4-6 hours. The bioavailability of orally and parenterally administered steroids is the same, and numerous randomized double-blind trials have demonstrated this equivalence. A primary reason to use intravenous corticosteroids is the adage to avoid medications by mouth when intubation is imminent. However, for most ED patients with acute asthma, the use of oral corticosteroids obviates
Complications:
Complications of severe asthma include the following:
Respiratory distress/arrest
Death
Prognosis:
The prognosis is excellent if compliant with proper therapies.
Risk factors for death from asthma include labile asthma, history of more than 3 ED visits or more than 2 hospitalizations, either ICU admission or endotracheal intubation within the past year, recent withdrawal from corticosteroids, current use of systemic corticosteroids, comorbid conditions (eg, heart disease, psychiatric disease, drug abuse), and concomitant adverse socioeconomic conditions.
