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The upper airway consists of all structures above the vocal cords—the larynx,
oropharynx, nasopharynx, and tongue. Its functions include warming, filtering,
and humification of inhaled air.
The lower airway consists of all structures below the vocal cords—the trachea,
mainstem bronchi, bronchioles, pulmonary capillaries, and alveoli. Pulmonary gas
exchange takes place at the alveolar level in the lungs.
The diaphragm is the major muscle of breathing; it is innervated by the phrenic
nerves. The intercostal muscles, the muscles between the ribs, are innervated by
the intercostal nerves. Accessory muscles, which are used during times of
respiratory distress, include the sternocleidomastoid muscles of the neck.
The primary breathing stimulus in a healthy patient is based on increasing arterial
carbon dioxide levels. The hypoxic drive—a backup system to breathe—is based
on decreasing arterial oxygen levels.
Ventilation is the movement of air into and out of the lungs. Negative-pressure
ventilation is the drawing of air into the lungs due to changes in intrathoracic
pressure. Positive-pressure ventilation is the forcing of air into the lungs and is
provided via bag-mask device, pocket mask, or mechanical ventilation device to
patients who are not breathing (apneic) or are breathing inadequately.
Manual airway maneuvers include the head tilt–chin lift, jaw-thrust (with and
without head tilt), and the tongue-jaw lift.
Regardless of the patient’s condition, his or her airway must remain patent at all
times. Clearing the airway means removing obstructing material; maintaining the
airway means keeping it open, manually or with adjunctive devices.
Airway obstruction can be caused by choking on food (or, in children, on toys),
epiglottitis, inhalation injuries, airway trauma with swelling, and anaphylaxis. It is
critical to differentiate between a mild (partial) airway obstruction and a severe
(complete) airway obstruction.
Chest compressions, finger sweeps (only if the object can be seen and easily
retrieved), manual removal of the object, and attempts to ventilate is the
recommended sequence of events to attempt to remove a foreign body airway
obstruction in the unconscious adult. Abdominal thrusts should be performed
continuously in the conscious adult or child with an airway obstruction until the
obstruction is relieved or he or she becomes unresponsive.
Back slaps and chest thrusts are performed to relieve a severe airway obstruction
in conscious infants. Chest compressions are performed in unconscious infants
with a severe airway obstruction.
Patients with a mild airway obstruction should be closely monitored and
transported. Encourage the patient who is coughing forcefully to continue
coughing, as it is the most effective way of clearing the airway.
If conventional methods of airway obstruction removal fail, perform direct
laryngoscopy and attempt to retrieve the object with Magill forceps.
Basic airway adjuncts include the oropharyngeal (oral) airway and the
nasopharyngeal (nasal) airway. The oral airway keeps the tongue off of the
posterior pharynx; it is used only in unresponsive patients without a gag reflex.
The nasal airway is better tolerated in patients with altered mental status who
have an intact gag reflex.
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Oropharyngeal suctioning may be required after opening a patient’s airway. Rigid
(tonsil-tip) catheters are preferred when suctioning the pharynx. Soft, plastic
(whistle-tip) catheters are used to suction secretions from the nose, and can be
passed down the endotracheal tube to suction pulmonary secretions.
Oropharyngeal suction should be limited to 15 seconds in the adult, 10 seconds in
the child, and 5 seconds in the infant.
The recovery position involves placing the patient in a left lateral recumbent
position. It is the preferred position to maintain the airway of unconscious patients
without traumatic injuries, who are breathing adequately.
Adequate breathing features a respiratory rate between 12 and
20 breaths/min, adequate depth (tidal volume), a regular pattern of inhalation and
exhalation, symmetrical chest rise, and bilaterally clear and equal breath sounds.
Inadequate breathing features a rate that is too slow
(< 12 breaths/min) or too fast (> 20 breaths/min), a shallow depth of breathing
(reduced tidal volume), an irregular pattern of inhalation and exhalation,
asymmetrical chest movement, adventitious airway sounds, cyanosis, and an
altered mental status.
The nonrebreathing mask is the preferred device for delivering oxygen to
adequately breathing patients in the prehospital setting; it can deliver up to 90%
oxygen when the flow rate is set at 15 L/min. The nasal cannula should be used if
the patient cannot tolerate the nonrebreathing mask; it can deliver oxygen
concentrations of 24% to 44% when the flowmeter is set at 1 to 6 L/min. Other
types of oxygen delivery devices include the simple face mask, partial rebreathing
mask, and Venturi mask.
The pulse oximeter measures the percentage of blood that is saturated with
oxygen (Sao2). This type of measurement depends on adequate perfusion to the
capillary beds and can be inaccurate when the patient is cold, is in shock, or has
been exposed to carbon monoxide.
Peak expiratory flow is a fairly reliable assessment of the severity of a patient’s
bronchoconstriction. It is also used to gauge the effectiveness of treatment, such
as inhaled beta-2 agonists (eg, Albuterol).
Patients with inadequate breathing require some form of positive-pressure
ventilation; patients with adequate breathing who are suspected of being
hypoxemic require 100% supplemental oxygen via nonrebreathing mask. Never
withhold oxygen from any patient suspected of being hypoxemic.
Unrecognized inadequate breathing will lead to hypoxia, a dangerous condition in
which the body’s cells and tissues do not receive adequate oxygen.
The methods of providing artificial ventilation—in order of preference—include
the mouth-to-mask technique; the two-person bag-mask technique; the flowrestricted, oxygen-powered ventilation device (FROPVD); and the one-person
bag-mask technique. Use extreme caution with the FROPVD and never use this
device in children and those with cervical spine or thoracic injuries.
Combined with your own exhaled breath, mouth-to-mask ventilation with
supplemental oxygen attached will deliver approximately 55% oxygen to the
patient. A bag-mask device with supplemental oxygen, a reservoir, and an
adequate mask-to-face seal can deliver almost 100% oxygen.
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Ventilating too forcefully or too fast can cause gastric distention, which can cause
regurgitation and aspiration. Delivering ventilations over 1 second and the use of
posterior cricoid pressure (Sellick maneuver) will reduce the incidence of gastric
distention and the associated risk of regurgitation/aspiration.
Invasive gastric decompression involves the insertion of a gastric tube into the
stomach. A nasogastric (NG) tube is inserted into the stomach via the nose; an
orogastric (OG) tube is inserted into the stomach via the mouth.
Unresponsive patients or patients who cannot maintain their own airway should
be considered candidates for endotracheal intubation, the insertion of an
endotracheal (ET) tube into the trachea. In orotracheal intubation, the ET tube is
inserted into the trachea via the mouth; in nasotracheal intubation (a blind
technique), the ET tube is inserted into the trachea via the nose. Other methods of
endotracheal intubation include digital (or tactile) intubation and intubation with
the use of a lighted stylet (transillumination).
Tracheobronchial suctioning is indicated if the condition of the intubated patient
deteriorates due to pulmonary secretions in the ET tube.
Extubation should not be performed in the prehospital setting unless the patient is
unreasonably intolerant of the tube. It is generally best to sedate the intubated
patient who is becoming intolerant of the ET tube.
Alternative airway devices, which may be used if endotracheal intubation is not
possible or is unsuccessful, include the Combitube, pharyngeotracheal lumen
airway (PtL), and the laryngeal mask airway (LMA).
Pediatric endotracheal intubation involves the same technique as for adult
patients, but with smaller equipment.
Patients with a tracheal stoma or tracheostomy tube may require ventilation,
suctioning, or tube replacement. Ventilation through a tracheostomy tube involves
attaching the bag-mask device to the 15/22-mm adapter on the tube; ventilation of
the patient with a stoma and no tracheostomy tube can be performed with a pocket
mask or bag-mask device. Use pediatric-size masks when ventilating a patient
through his or her stoma.
Open (surgical) cricothyrotomy involves incising the cricothyroid membrane,
inserting a tracheostomy tube or ET tube into the trachea, and ventilating the
patient with a bag-mask device. Needle cricothyrotomy involves inserting a 14- to
16-gauge over-the-needle catheter through the cricothyroid membrane and
ventilating the patient with a high-pressure jet ventilation device.
Rapid-sequence intubation (RSI) involves using pharmacologic agents to sedate
and paralyze the patient to facilitate placement of an ET tube. It should be
considered when a conscious or combative patient requires intubation but cannot
tolerate laryngoscopy.
Drugs used for RSI include sedatives, such as diazepam (Valium) and midazolam
(Versed), and neuromuscular blocking agents (paralytics) to induce complete
paralysis. The latter agents are classified into depolarizing paralytics (eg,
succinylcholine) and nondepolarizing paralytics (eg, vecuronium, pancuronium).
Check for loose dental appliances in a patient before providing artificial
ventilation. Loose dental appliances should be removed to prevent them from
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obstructing the airway; tight-fitting dental appliances should be left in place
during artificial ventilation.
Dental appliances should be removed before intubating a patient. Removing them
after the patient has been intubated may result in inadvertent extubation.
Patients with massive maxillofacial trauma are at high risk for airway
compromise due to oral bleeding. Assist ventilations and provide oral suctioning
as needed.