Airway Management

Oxygen moves from the atmosphere and crosses the alveolar membrane and attaches to the hemoglobin by a process called diffusion, where molecules move from an area of higher concentration to an area of lower concentration. Next, red blood cells carry the hemoglobin, with bound oxygen delivering it to the capillaries to the body’s cells. At the same time, carbon dioxide is moved from the cells into the blood and carried back to the lungs, where it moves into the alveoli by diffusion. The airway is divided into the upper and lower airways. The structures that help us breathe include the diaphragm, intercostal muscles, which are the muscles in between the ribs, and when we are in distress, accessory muscles.

Upper airway consists of the nasopharynx, nasal air passage, pharynx, oropharynx, mouth, epiglottis, laryngopharynx (larynx, trachea), which are all above the level of the vocal cords. The thyroid cartilage joins in a V shape anteriorly to form the laryngeal prominence known as the Adam’s apple. The cricoid cartilage lies inferior to the thyroid cartilage and forms the lowest portion of the larynx. The cricoid cartilage is the first ring of the trachea and the only lower airway structure that forms a complete ring. The cricothyroid membrane is the elastic tissue that connects the thyroid cartilage to the cricoid ring. The glottis is the space between the vocal cords and the airway.

The lower airway consists of the trachea, bronchioles, carina, and main bronchus. Its function is to deliver O2 to the alveoli. Its boundary is the fourth cervical vertebra to the xiphoid process, the lower tip of the sternum. The trachea goes from the cricoid cartilage to the thoracic cavity. Once there, it divides at the level of the carina into the two mainstem bronchi. When performing airway management techniques on a child, place a towel under the shoulders to maintain a neutral position of the head. The visceral pleura covers the outer surface of the lung tissue. The parietal pleura lines the inside of the thoracic cavity. Between the lungs is a space called the mediastinum, which contains the heart, esophagus, trachea, and major bronchi. Everything is then dictated by the phrenic nerves.

When breathing, partial pressure is used to tell the amount of gas in air or dissolved in fluid such as blood. PaO2 within alveoli is 104 mm Hg. CO2 enters from the blood and causes a partial pressure of 40 mm Hg. Negative pressure ventilation occurs when air is pulled through the trachea, causing the lungs to fill due to thoracic cage air pressure being lower than the atmospheric pressure. The average tidal volume is 500 mL. Alveolar ventilation is the amount of air that reaches the alveoli, dead space minus the tidal volume. Vital capacity is the amount of air that can be forcibly expelled from the lungs. Failure to meet the body’s needs for oxygen may result in hypoxia. Breathing is regulated by carbon dioxide levels; when CO2 increases, the pH of the CSF (cerebrospinal fluid) decreases. Emphysema or bronchitis causes difficulty eliminating carbon dioxide through exhalation. Higher levels alter respiratory drive. The body then uses a backup called hypoxic drive, which is based on levels of O2 in plasma. Shortness of breath is called dyspnea. Hypoxemia is a low level of O2 in arterial blood. Hypoxia is a low level of oxygen at the cellular level. Carbon monoxide poisoning occurs because carbon monoxide binds to the hemoglobin more readily than oxygen. During metabolism, nutrients and oxygen produce energy in the form of adenosine triphosphate. Surfactant reduces surface tension within the alveoli and keeps them expanded. The oxygen and carbon dioxide exchange is called internal respiration. Cells convert glucose to energy in a process known as aerobic metabolism. Chemoreceptors monitor the levels of oxygen, carbon dioxide, hydrogen ion concentration, and the pH of the CSF. Ventilation/perfusion mismatch can be seen in pulmonary embolism (blood clot). Even though the patient continues to ventilate, external respiration will be impaired because of decreased blood flow to the lungs. Increases in carbon dioxide in the bloodstream is a condition called hypercarbia. Muscular dystrophy can impair pulmonary function as loss of muscle contractility results in gradual weakening of muscles such as the diaphragm and intercostal muscles. The tongue is the most common airway obstruction in the unresponsive patient. An allergic reaction can cause the airway obstruction to swell and also decrease pulmonary ventilation from bronchoconstriction. Trauma to the airway must be noticed, especially a fracture to the mandible/jawbone; patients may have a hard time keeping the airway open. Pneumonia, pulmonary edema, and COPD/emphysema may also result in a disturbance of cellular metabolism by decreasing the surface area of the alveoli either by damaging the alveoli or by leading to an accumulation of fluid in the lungs. Intrapulmonary shunting occurs when blood circulates from the right to the left without oxygenation. Obstruction of blood flow to individual cells and tissue can be related to traumatic emergencies, hemothorax or pneumothorax, whether a simple or tension pneumothorax, open pneumothorax (sucking chest wound). Hypovolemic shock is a decrease in circulating volume that causes inadequate oxygen delivery to the body. Vasodilatory shock is determined by the size of the blood vessels. As the diameter of the blood vessels increases, the blood pressure in the circulatory system decreases. As the systemic blood pressure decreases, O2 is not delivered effectively to the tissues.

Adequate breathing is 12–20 breaths/min in adults, 12–40 breaths/min in children, and 30–60 breaths/min in infants. There is a regular pattern of inhalation and exhalation. There are clear and equal lung sounds on both sides of the chest with equal chest rise. There is adequate depth and tidal volume.

For inadequate breathing, there is a respiratory rate of fewer than 12 breaths/min or more than 20 breaths/min in the presence of shortness of breath (dyspnea). Irregular rhythm, such as a patient taking a series of deep breaths followed by periods of apnea. Diminished, absent, or noisy auscultated breath sounds. Use of tripod position and reduced flow of expired air at the nose and mouth. Unequal or inadequate chest expansion, reduced tidal volume. Increased effort of breathing (use of accessory muscles) with shallow depth (reduced tidal volume). The skin that is pale, cyanotic, cool, or moist. The skin is also pulling in around the ribs or above the clavicles during inspiration (retractions).

A patient may appear to be breathing after his or her heart has stopped. These occasional gasping breaths are called agonal gasps. Cheyne-Stokes respirations are often seen in patients with stroke and patients with serious head injuries. They are an irregular respiratory pattern in which the patient breathes with an increasing rate and depth of respirations that is followed by a period of apnea or lack of spontaneous breathing, with the pattern repeating. Ataxic respirations are irregular, ineffective respirations that may or may not have an identifiable pattern.

To assess for adequate and inadequate respiration, a pulse oximeter is about 1 minute behind, and conditions can change rapidly, so be alert and concentrate. In cases of carbon monoxide poisoning, it can be wrong. End-tidal CO2 is the measure of the maximal concentration of CO2 at the exhaled breath. A low CO2 level could indicate a number of conditions. If the patient is hyperventilating, he or she is eliminating carbon dioxide faster than the body is making it; this would cause a low CO2 level. A low CO2 level could also indicate decreased CO2 return to the lungs because of reduced CO2 production at the cellular level secondary to conditions such as shock and cardiac arrest. A high CO2 level may indicate that the patient is retaining CO2 secondary to ventilation inadequacy. An absence of CO2 can indicate that the patient is not breathing at all. If opioids overdose, they are retaining too much carbon dioxide, and a tall waveform is expected.

Oxygen can become a missile if it falls on the regulator or if held by the neck alone and that slips off. Be sure the pins match to ensure O2 and not another type of regulator or cylinder. Combustion is a hazard, so make sure and watch for bystanders who are smoking or sparks generated during vehicle extrication. Oxygen toxicity is damage to cellular tissue due to excessive oxygen levels in the blood. AMA says conditions like shock or hypoxemia are immediately life-threatening, whereas oxygen toxicity is not and should be administered when in doubt.

Nonrebreathing masks are used to administer high concentrations of oxygen to hypoxemic patients who are otherwise breathing adequately, flow rate 10–15 L/min, up to 90% inspired oxygen. Gas escapes through the flapper valve ports at the cheek area of the mask, which prevents exhaled gas from being rebreathed. Make sure the reservoir bag is full before the mask is placed on the patient. The bag does not fully collapse when the patient inhales, just 2–3 of the bag volume. Should the bag collapse, increase the flow rate. Remove mask when oxygen therapy is discontinued.

Nasal cannula is 24% to 44% inspired oxygen when the flowmeter is set at 1 to 6 L/min. For the comfort of your patient, flow rates above 6 L/min are not recommended with the nasal cannula. Used in patients with mild hypoxemia. If a patient cannot tolerate a nonrebreathing mask, you will have to use a nasal cannula. Partial rebreathing masks are good if you want to increase the patient’s PaCO2 when you think they are experiencing hyperventilation syndrome.

CPAP is used when a patient is showing signs of moderate and severe respiratory distress. It works by changing the pressure in the lungs, creating a better pressure system. CPAP improves ventilation and not just oxygenation by keeping the alveoli open. So you most likely want to use a nonrebreather mask on a hypoxic patient instead of CPAP. Used for COPD, pulmonary edema, asthma, pneumonia, and near drowning.

When there is a foreign body airway obstruction, abdominal thrust is usually not effective for dislodging a partial obstruction. Attempts to remove the object manually could force the object farther down the airway. With poor air exchange, ineffective breathing, stridor (a high-pitched noise heard primarily on inspiration), and cyanosis. Stridor is an indication of a mild upper airway obstruction. For patients with mild airway obstruction with poor air exchange, treat immediately as if there is a severe airway obstruction. If a patient is unconscious, begin CPR at once; sometimes chest compressions are enough to dislodge the object. Resistance to ventilations is a primary indicator of an issue. Abdominal thrust is the most effective method of dislodging and forcing an object out of the airway. If the object is observed, remove it with a gloved index finger or suction. Attempt only if visible.

The four-step process of assisting with advanced life support (ALS) skills. The first step in preparing a patient for ET intubation is oxygenation. Good oxygenation often includes bag-mask ventilation; this is a critical phase called preoxygenation. Apneic oxygenation is a technique in which oxygen administered via a high-flow nasal cannula is left in place during an intubation attempt, allowing for continuous oxygen delivery into the airways during all phases of the procedure. Use towels and blankets and pillows to ramp, position, and otherwise manipulate the patient so that the first attempted intubation will be successful, sniffing position. Keep the suction equipment at hand in case you need to suction the patient’s airway. May ask for your help in manipulating the patient’s larynx or otherwise positioning the patient for a better view. May be asked to hand the ET tube, gum elastic bougie, suction catheter, or other equipment to the ALS provider. Should intubation attempts fail, it may be your responsibility to prepare and hand over the supraglottic airway device.

BE MAGIC
B – Perform bag-mask preoxygenation
E – Evaluate for airway difficulties
M – Manipulate the patient
A – Attempt first-pass intubation
GI – Use a supraglottic airway if unable to intubate
C – Confirm successful intubation/Correct any issue

Signs that indicate a complication with an intubated patient are to confirm intubation success, you may attach the end-tidal CO2 waveform detector in line between the ET tube and the bag. You may also either ventilate the patient while another provider checks for positive breath sounds and the absence of gastric sounds or listen while another team member ventilates. Absence of breath sounds and presence of gastric sounds suggest that the ET tube was improperly inserted into the esophagus. Absence of an end-tidal CO2 level. Decreasing SpO2 levels. Increasing resistance when ventilating or poor ventilation and perfusion. Improper positioning or dislodgement of the ET tube.