Chapter 15: Ready for Review

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Chapter 15: Ready for Review

• The upper airway consists of all structures above the vocal cords—the larynx, oropharynx, nasopharynx, and tongue. Its functions include warming, filtering, and humidification 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 respiratory and cardiovascular systems work together to ensure that constant supplies of oxygen and nutrients are delivered to every cell in the body and that carbon dioxide and other waste products are removed from every cell.

• Ventilation, oxygenation, and respiration are crucial for the tissues to receive the needed nutrients.

• Ventilation is the act of moving air into and out of the lungs. For ventilation to occur, the diaphragm and intercostal muscles must function properly. Diffusion allows oxygen to transfer from the air into the capillaries.

• Changes in oxygen demand are regulated primarily by the pH of the cerebrospinal fluid (CSF), which is directly related to the amount of carbon dioxide dissolved in the plasma portion of the blood (Paco2). The medullary respiratory centers in the brainstem control the rate, depth, and rhythm of breathing. Chemoreceptors monitor the chemical composition of the blood and provide feedback to the respiratory centers.

• 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.

• Oxygenation is the process of loading oxygen molecules onto hemoglobin in the bloodstream. Oxygenation may not occur if the environment is depleted of oxygen or if the environment contains carbon monoxide, which prevents oxygen from binding to hemoglobin.

• Respiration is the exchange of oxygen and carbon dioxide in the alveoli and tissues of the body. Cells normally perform aerobic respiration, which converts glucose into energy. Without oxygen, cells perform anaerobic metabolism, which cannot meet the metabolic demands of the cell. Ultimately, anaerobic metabolism will lead to cell death if the lack of oxygen not corrected.

• The primary breathing stimulus in a healthy person is based on increasing arterial carbon dioxide levels. The hypoxic drive—a backup system to breathe—is based on decreasing arterial oxygen levels.

• Conditions that can inhibit the body’s ability to effectively deliver oxygen to the cells are many. With ventilation/perfusion ratio mismatch, ventilation may be compromised but perfusion continues, leading to a lack of oxygen diffusing into the bloodstream, which can lead to severe hypoxemia.

• Other factors that impede delivery of oxygen to cells include airway swelling, airway obstruction, medications that depress the central nervous system, neuromuscular disorders, respiratory and cardiac diseases, hypoglycemia, circulatory compromise, submersion, and trauma to the head, neck, spine, or chest.

• Hypoventilation and hyperventilation, along with hypoxia, can cause disruptions in the acid-base balance in the body that may lead to rapid deterioration in a patient’s condition and death. When there is an excess of acid in the body, the fastest way to eliminate it is through the respiratory system. Excess acid can be expelled as carbon dioxide from the lungs. Conversely, slowing respirations will increase the level of carbon dioxide. Respiratory acidosis and respiratory alkalosis can result from a number of conditions and can be life threatening.

• Adequate breathing in the adult features a respiratory rate between 12 and 20 breaths/min, adequate depth (tidal volume), a regular pattern of inhalation and exhalation, symmetric 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, asymmetric chest movement, adventitious airway sounds, cyanosis, and an altered mental status.

• It is important to be able to recognize abnormal breathing patterns when assessing a patient. These include Cheyne-Stokes respirations, Kussmaul respirations, Biot (ataxic) respirations, apneustic respirations, and agonal gasps.

• While assessing breathing, auscultate breath sounds with a stethoscope. Breath sounds represent airflow into the alveoli. They should be clear and equal on both sides of the chest (bilaterally), anteriorly, and posteriorly. Abnormal breath sounds include wheezing, rhonchi, crackles, stridor, and pleural friction rub.

• The pulse oximeter measures the percentage of blood that is saturated with oxygen (Spo2). 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 bronchoconstriction. It is also used to gauge the effectiveness of treatment, such as inhaled beta-2 agonists (such as albuterol).

• End-tidal co2 (etco2) monitors detect the presence of carbon dioxide in exhaled air and are important adjuncts for determining ventilation adequacy. These monitors can analyze air samples of a spontaneously breathing patient or can be used when an advanced airway has been inserted. Quantitative waveform capnography is the “standard” and is the most accurate method for monitoring etco2.

• 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 a 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.

• Regardless of the patient’s condition, his or her airway must remain patent at all times. The first step in airway management is to position the patient. The recovery position involves placing the patient in a left lateral recumbent position. It is the preferred position to maintain the airway of unresponsive patients without traumatic injuries who are breathing adequately.

• The patient’s head must be properly positioned. Manual airway maneuvers include the head tilt–chin lift, jaw-thrust (with and without head tilt), and the tongue-jaw lift.

• Clearing the airway means removing obstructing material; maintaining the airway means keeping it open, manually or with adjunctive devices.

• 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 an endotracheal tube to suction pulmonary secretions.

• Oropharyngeal suction should be limited to 15 seconds in an adult, 10 seconds in a child, and 5 seconds in an infant.

• 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 an unresponsive adult. Abdominal thrusts should be performed continuously in a responsive adult or child with an airway obstruction until the obstruction is relieved or he or she becomes unresponsive.

• 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.

• Supplemental oxygen should be administered to any patient with potential hypoxia, regardless of his or her clinical appearance. Be familiar with oxygen cylinder sizes and their duration of flow, and always practice safety precautions when using oxygen.

• The nonrebreathing mask is the preferred device for providing 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 partial rebreathing mask and Venturi mask.

• The methods of providing artificial ventilation—in order of preference—include the two-person bag-mask technique, mouth-to-mask with one-way valve and supplemental oxygen attached, manually triggered ventilation device, and the one-person bag-mask technique. Use extreme caution with the manually triggered ventilation, and never use this device in children and patients with thoracic injuries.

• Continuous positive airway pressure (CPAP) has been clinically proven to improve a patient’s breathing by forcing fluid from the alveoli (in pulmonary edema) or dilating the bronchioles (in obstructive lung diseases and asthma). It involves the patient breathing against a certain amount of positive pressure during exhalation. CPAP has also been shown to reduce the need for intubation.

• Check for loose dental appliances in a patient before providing artificial ventilation. Loose dental appliances should be removed to prevent them from 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.

• Ventilating too forcefully or too fast can cause gastric distention, which can cause regurgitation and aspiration. Administering ventilations over 1 second—just enough to produce visible chest rise—will reduce the incidence of gastric distention and the associated risks of regurgitation and aspiration.

• Invasive gastric decompression involves the insertion of a gastric tube into the stomach. A nasogastric tube is inserted into the stomach via the nose; an orogastric tube is inserted into the stomach via the mouth.

• 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 a 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 a stoma.

• Unresponsive patients or patients who cannot maintain their own airway should be considered candidates for endotracheal (ET) intubation, the insertion of an 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 ET intubation include digital (or tactile) intubation, retrograde intubation, face-to-face intubation, and intubation with the use of a lighted stylet (transillumination).

• An important step in intubation is confirmation of tube placement. Continuous waveform capnography, in addition to a clinical assessment (such as auscultation of breath sounds and over the epigastrium and assessing for visible chest rise), is regarded as the most reliable method of confirming and monitoring correct placement of the ET tube.

• If an attempted intubation does not result in acceptable oxygen saturations, perform simple BLS maneuvers with an oral airway and/or nasal airway and a bag-mask device, and consider using another airway device.

• Tracheobronchial suctioning is indicated if the condition of an intubated patient deteriorates because of 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 an intubated patient who is becoming intolerant of the ET tube.

• Pediatric ET intubation involves the same technique as for adult patients, but with smaller equipment.

• Rapid-sequence intubation (RSI) involves using pharmacologic agents to sedate and paralyze a patient to facilitate placement of an ET tube. It should be considered when a responsive 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 (succinylcholine) and nondepolarizing (such as vecuronium, pancuronium, and rocuronium) paralytics.

• Alternative airway devices, which may be used if ET intubation is not possible or is unsuccessful, include the Combitube, laryngeal mask airway, King LT airway, and Cobra perilaryngeal airway.

• 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.
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