Respiratory emergencies

In emergency medicine, ensuring the airway is not obstructed is usually the first priority in assessment and immediate measures. The mnemonic "ABCD" gives the immediate priorities:

• Airway: There must be a clear path from the nose or mouth to the lungs, which may take no more than proper anatomic positioning with the head-tilt/chin-lift maneuver.Even if the patient is incapable of active breathing, air can be supplied externally, but if there is no way to oxygenate the blood, irreparable brain damage can start in 4-5 minutes at normal body temperature.
• Breathing: If the patient is making no respiratory effort, oxygen can be supplied externally, initially by mouth-to-mouth artificial respiration, manual bag-valve-mask device, or a mechanical ventilator. When the patient is breathing ineffficiently, supplemental oxygen may be adequate, or it may be necessary to paralyze the respiratory muscles and take over mechanical ventilation.
• C:irculation. Blood needs to move, through regular or artificial heartbeat, or interventions to restore circulation.

Whenever there is even mild respiratory distress, emergency personnel must plan for contingencies; some conditions, such as anaphylactic shock can progress from itching and wheezing, to complete airway obstruction, in minutes.

If there is active respiratory distress or a strong index of suspicion that it is imminent, other supportive steps should be taken. A breathing patient should be put on oxygen. Establish at least two large-bore intravenous lines, draw several tubes of venous blood according to the local protocol, and attach the patient to a cardiac monitor-defibrillator.

Attach a pulse oximeter, and, when available, a pulse capnometer. Take vital signs.

Position the patient to assist respiration. Note the patient's weight if the treatment table is equipped with a scale; increasing weight can be a warning of developing pulmonary edema or other fluid load abnormalities.

Immediate airway management

Without a patent airway, all other resuscitative efforts will be futile. The examiner begins by assessing the patient's level of consciousness and efficiency of breathing. If the patient is conscious, able to speak, not cyanotic, and has nonemergent vital signs and chest sounds, assessment can proceed to the evaluating urgent but not immediately life-threatening conditions.

In a nonbreathing patient, the simplest and fastest measures may be all that is needed: the head-tilt/jaw-lift maneuver. This is contraindicated if there is there is suspected injury to the cervical spine, and the jaw-thrust maneuver used instead. If head-tilt/jaw-lift fails, jaw-thrust sometimes restores the airway. Should the circumstances suggest the airway might be obstructed by a foreign body, including food, perform an age-appropriate airway-clearing procedure such as infant back blows or the Heimlich maneuver.

If those manual maneuvers fail, the next actions depend on the training of the responder and the available equipment. Soft rubber or plastic nasopharyngeal or oral airways may be used before more advanced methods, and, if available, positive-pressure ventilation may be tried briefly before moving to more advanced measures such as intubation or creating a surgical airway. Some conditions justify immediate intubation:

1. No breathing at all (apnea)
2. Glasgow Coma Scale < 9
3. Sustained seizure activity.
4. Unstable mid-face trauma.
5. Airway injuries.
6. Large flail segment or respiratory failure.
7. High aspiration risk.
8. Inability to otherwise maintain an airway or oxygenation.

Intubation

Intubation physically protects the airway from vomitus or other fluids being aspirated, and also acts as a mechanical "splint" inside it, protecting it from laryngospasm or laryngeal edema. While clinical judgment is always paramount, full endotracheal intubation may not be needed. Various less invasive oral or nasopharyngeal airway may provide adequate mechanical support, and require far less less technical skill to insert.

Preparation

• Rapid sequence intubation

Other immediate threats to life

Upper airway obstruction

If the Heimlich or related maneuvers fail to remove a foreign body, the next step is attempted removal under direct removal with a laryngoscope. If that fails, a surgical airway is probably necessary, with the understanding that an obstruction in the distal glottis may not be relieved even by cricothrotomy or tracheostomy. Continuing failure requires either a more extensive surgical approach or use of a rigid bronchoscope.

Tension pneumothorax

Tension pneumothorax is far more severe than ordinary pneumothorax. In a conventional pneumothorax, air enters the chest cavity, which is normally at negative pressure relative to room air. In the less complicated types of pneumothorax, there is leakage in both directions. Tension pneumothorax, however, is caused by damage that creates a one-way valve effect, so the air pressure in the chest continues to increase, and can cause complete lung failure.

There is considerable controversy about its diagnosis and treatment, especially in the field. In principle, a large-bore hypodermic needle, equipped with a flutter valve that will let air out but not in, converts the condition to a regular pneumothorax. If the problem is indeed tension pneumothorax, and the needle is inserted in the correct place, the decompression can indeed be a lifesaving immediate intervention.

Diagnosis is not as clear-cut as textbooks sometimes suggest, and, in inadequately trained hands, the needle either may not reach the air pocket, or may damage other structures.

Acute Respiratory Distress Syndrome

Acute Respiratory Distress Syndrome is not an independent cause of disease, but a pattern of responses to severe insult to the lungs, from factors including infection in the blood or lungs, or trauma to the lungs. Its presentation includes dyspnea, profound hypoxemia, decreased lung compliance, and diffuse bilateral infiltrates on chest X-ray. There has been an informal concept called the "Golden Hour" in trauma, which, when expressed somewhat more specifically, deals with the increasing probability that massive blood loss will produce "irreversible shock". A less quantitative version of the idea originated in the First World War; a seminal paper from the 1960s quantified, that dogs could survive a loss of 40 to 50 percent of their blood volume if it were replaced within one hour. With each hour of delay in replacement, survival dropped.

The longer it takes to reverse the pattern presented by ARDS, the less the chance of patient survival. For example, prolonged ARDS can produce pulmonary edema.

Severe aspiration into the respiratory tract

When vomitus is visible in the oropharynx, assume it has been aspirated. Mechanical aspiration problems may result from ingestion of oil or gasoline can also have similar effects.

Before intubation, clear the airway with a suction catheter. Corticosteroids have been shown to decrease recovery and should not be administered. Hospitalize for close monitoring, although the emergency assessment should continue to determine a continuing source of vomiting, or other disturbance to respiration.

While it is not part of the immediate workup, the next stage of the examination must determine if aspiration pneumonia is present. This can be produced by gastric acid, bacteria, or oil.

Severe pulmonary edema

Pulmonary edema can be due to direct lung disorders, or a consequence other disorders of fluid handling, especially heart failure. Cardiac etiology is most common, but primary lung disorders need specific handling; it is not impossible to have comorbid causes, such as ARDS.

There is a syndrome of high-altitude pulmonary edema, which results from exposure to a pressure level approximately of 2.5 km or higher. Obviously, this should be considered in mountainous area, but it is a possible effect of a malfunctioning aircraft oxygen system, and should be considered when an individual develops respiratory distress in flight. Commercial aircraft cabins are pressurized to well below that level, so an isolated case on a passenger aircraft is unlikely, but certainly within the scope of the differential diagnosis if the patient was on a breathing mask in a smaller or military aircaft.

Severe asthma

Asthma is, when acquired, usually a lifelong disease. The standard of treatment is to suppress the hyperimmune response, which, through the release of inflammatory factors, will lead to increasing difficulty. Criteria for an immediate asthmatic crisis include an inability to speak and intense perspiration. If the patient has difficulty in speaking and still has trouble breathing when in an optimal resting position, consider the exacerbation as severy. According to the diagnostic criteria of the U.S. National Asthma Education and Prevention Program. Severe asthma has dyspnea at rest and can speak only with difficulty. The peak expiratory flow rate <40 percent predicted or personal best. The situation is Life threatening when respiratory distress makes it impossible to speak, the patient is perspiring, and the peak expiratory flow rate, if it can be taken, is <25 percent predicted or personal best.

Laryngeal or tracheal narrowing

These sections of the upper airway can constrict briefly (laryngospasm) as a muscular effect, or narrow due to local edema. Regardless of the cause, it is obviously urgent to intubate, or, if necessary, establish a surgical airway.

If due to anaphylaxis, or strong suspicion of it, epinephrine should be administered as soon as possible. Patients with known sensitivities that may cause anaphylaxis often may carry autoinjectors; seeing one on or near the patient is strongly suggestive of the condition.

Angioedema involving the respiratory is an uncommon but recognized side effect of angiotensin-converting enzyme inhibitors.

Urgent threats to life

Chest wall defects

Chest wall defects due to trauma often overlap with lung collapse. For example, an extensive rib fracture could simultaneously cause flail chest, a pneumothorax where one broken bone went through the skin, and perhaps hemothorax where a different bone fragment lacerated a blood vessel.

Neurogenic respiratory distress

Support the patient with oxygen by nonrebreathing mask, or by intubation if appropriate, and evaluate coma and altered consciousness emergencies.

Patients at risk

People who have been exposed to smoke, toxic fumes, etc., may not initially be in respiratory distress, but the circumstances of the exposure can make it wise for them to be monitored for 24 to 72 hours. They need not be in an emergency department, but, depending on the specific incident, may be held at an observation facility, or discharged such that they are under responsible observation and can quickly be brought to an emergency facility.