3. Scenario It is a pleasant spring morning. You and your partner have been dispatched to a residence to assist a man injured by a falling tree. As you approach the residence, a middle-aged man directs you to the back yard where you see two men kneeling next to a third man, who is sitting on the ground, leaning against a large fallen tree.
Instructor Notes: Solicit responses from participants rather than supply the information yourself. Ask follow-up questions as needed. For example, if participants respond with a list of potential injuries, follow up with a questions such as “What makes you say that?” This verifies understanding of the mechanism of injury. Key Points: Primary scene safety consideration is the stability of the tree. The mechanism is suspicious for blunt and penetrating trauma; particularly at the point of impact of the tree branch. Trauma to the spine is possible, as well as injuries to the thoracic and abdominal organs.
Instructor Notes: Solicit responses from participants rather than supply the information yourself. Ask follow-up questions as needed. For example, if participants respond with an answer of “Yes,” follow up with a question such as “What makes you say that?” This verifies understanding of how the patient’s signs and symptoms relate to ventilatory compromise. Key Points: Assessment is a process of seeking evidence of potential problems, including evidence of impaired respiration. Participants should note the following: The patient is awake and able to speak only 2 to 3 words without a breath. (LOC, airway, breathing) The patient is exhibiting labored ventilations (general impression) Based on the mechanism of injury and general impression, there is ventilatory compromise. External bleeding is minor, but internal bleeding cannot be ruled out and shock is a possibility. Compromised ventilation results in hypoxia and acidosis, which can kill the patient rapidly.
Key Points: Understanding what is happening to the patient is critical to understanding how respiratory compromise kills and what prehospital care providers must do to intervene in the process. The patient’s airway is patent, but he is having labored ventilations. He has an injury to the chest, therefore we suspect an injury to the chest wall and/or lung or compromised pleural contact are interfering with ventilation. Ventilatory (breathing) assessment is not complete until the chest and lungs have been assessed by inspection, palpation, and auscultation.
Key Points: Compromises to airway, breathing, and circulation are treated in the primary survey. What does this patient need right now? What else do we need to know? Transition: Discussion of pathophysiology follows.
Instructor Notes: It is critical that participants understand this basic definition of respiratory compromise. Key Points: The patient’s ventilations are compromised. The patient is working harder to achieve an adequate minute volume. As the patient’s ability to compromise diminishes, his cells will not receive enough oxygen to produce an adequate amount of energy for them to function.
Key Points: The terms ventilation and respiration are often used interchangeably, but physiologically, they are not the same.
Key Points: A patent airway is a prerequisite to adequate ventilation. Ventilation does not necessarily result in oxygenation, in and of itself. The air entering the lungs must contain an adequate concentration of oxygen. The oxygen must be able to cross the alveoli and attach to hemoglobin in RBCs. The RBCs must be delivered to the cellular level. The oxygen must be able to disassociate from the hemoglobin at the cellular level.
Key Points: Lactic acid is a product of cellular metabolism. Without oxygen, it cannot be converted to water and carbon dioxide for elimination, resulting in acidosis. Oxygen is also needed for ATP production. Without sufficient oxygen, ATP is depleted and cells cannot do their work. If oxygen depletion is severe enough, cells die.
Key Points: The most common cause of airway obstruction is the tongue.
Key points: An unresponsive patient cannot protect his or her airway. Unresponsiveness may be due to airway obstruction. Airway obstruction may be secondary to unresponsiveness. No air movement will be present with a complete airway obstruction. In a patient with respiratory effort, a partial airway obstruction may result in noisy breathing. Gurgling – liquids Snoring – tongue Stridor – upper airway obstruction Wheezing – lower airway obstruction
Key Points: A quick inspection should be performed to assess the oropharynx for food, avulsed teeth, or other material that may need to be manually cleared from the airway. Manual maneuvers relieve and prevent airway obstruction caused by the tongue.. With suspected cervical spinal injury, the jaw thrust is used rather than the head-tilt/chin-lift Suction is needed to remove blood, fluid, and vomit from the airway. The airway must be clear before ventilating of the patient begins. Basic adjuncts assist in preventing the tongue from occluding the airway, but do not relieve the need to maintain proper head position. Aspiration of vomit, fluid, or blood and gastric distension are still possible with basic adjuncts — but a good BLS airway is better than a poor ALS airway.
Key Points: Nonvisualized airways are an EMT-Basic skill in many states. Nonvisualized airways require less skill maintenance and provide better, though not complete, protection of the airway from aspiration and gastric insufflation. Nonvisualized airways do not require hyperextension of the neck for placement. Prolonged attempts at insertion lead to worsening hypoxia.
Key Points: Intubation has long been considered the gold standard for airway management. Poor initial training (lack of intubation opportunities) and inadequate skill maintenance lead to decreased competence in intubation. Prolonged attempts worsen hypoxia. A good BLS airway is better than a poor ALS airway.
Key Points: Surgical airways are used only when an adequate airway cannot be established by any other means. Needle cricothyrotomy leads to inadequate exhalation and overinflation of the chest, impairing ventilation and gas exchange. It is an extremely short-term measure. Provides for adequate ventilation; potential for complications, such as false passage and hemorrhage.
Key Points: Larynx houses the vocal cords. Trachea divides into right and left main stem bronchi at the carina.
Key Points: Gas exchange occurs only at the alveolar level.
Key Points: Ventilation is triggered by increasing levels of CO 2 and (secondarily) by decreasing levels of O 2 . When chemoreceptors detect changes in gas levels, nerves conduct impulses to the respiratory center, which sends impulses to the diaphragm and intercostal muscles. When the diaphragm and intercostal muscles contract, the size of the thoracic cavity increases, creating a vacuum by which the adherent pleural layers expand the lung, decreasing pressure inside the lung and allowing air to flow into the lungs. At the end of inspiration, the diaphragm and intercostal muscles relax, making the thoracic cavity smaller, increasing the pressure inside the lungs, and forcing air to flow out of the lungs. However, air will flow from higher to lower pressure through the path of least resistance. An opening in the chest wall that is 2/3 the size of the tracheal diameter will allow air to flow into the thoracic cavity, where it separates the visceral and parietal pleura.
Key Points: The respiratory dead space includes all the parts of the airway above the alveoli.
Key Points: Shock and problems with airway, ventilation, and oxygenation compound each other.
Key points: Severe ventilatory compromise is apparent by the general appearance. Assess for hypoventilation by considering both the volume and rate of breathing. Assist ventilations immediately if needed. Are there immediately life-threatening causes of hypoventilation that can be addressed in the field? Tension pneumothorax Flail chest
Instructor Notes: Solicit responses from participants rather than supply the information yourself. Ask follow-up questions as needed. For example, if participants respond with an answer of “Yes,” follow up with a question such as “What makes you say that?” This verifies understanding of how the patient’s signs and symptoms relate to ventilatory compromise.
Key Points: Recall that with normal rate and tidal volume, 4900 mL is available for gas exchange; this patient has only 3600 mL available for gas exchange. An increased rate can compensate for a decreased volume only to a point. Is the patient neurologically capable of ventilation? Are the conducting airways intact? Is the chest wall intact? Are the pleura in contact with each other?
Key Points: Consequences of anaerobic metabolism include: Dysfunction of cell membranes such that potassium and lactic acid leave the cell and enter the interstitial fluid, resulting in hyperkalemia and acidosis. pH (acidosis) causes the release of cellular enzymes that destroy cells, ultimately resulting in organ damage, organ death, and patient death. The sodium and water enter the cell resulting in cellular edema and loss of intravascular fluid. The low process of anaerobic metabolism must be reversed by ensuring that oxygenated red blood cells reach the capillaries that supply the body’s cells.
Key Points: Right atrium Right ventricle Pulmonary artery Lungs Capillary-alveolar interface Pulmonary vein Left atrium Left ventricle Systemic circulation
Key Points: Gas exchange requires an adequate amount of oxygen reaching the alveoli. An adequate number of red blood cells reaching the pulmonary capillaries. A short diffusion distance across the respiratory membrane. Factors that can increase the diffusion distance and decrease gas exchange: Pulmonary contusion Trapped alveolar air (COPD) Pulmonary edema ARDS
Instructor Notes: Solicit responses from participants rather than supply the information yourself. Ask follow-up questions as needed. This verifies understanding of the cause of respiratory compromise. Key Points: Penetrating trauma is evident; the mechanism also strongly suggests pulmonary contusion due to blunt trauma. Blood from injured pulmonary capillaries enters the interstitial space between the capillaries and the alveoli, increasing the distance for gas exchange. Gas exchange may not be occurring in injured portions of the lung. There is no evidence of flail chest (3 or more adjacent ribs each broken in 2 or more places). The penetrating injury is allowing air from the lung to enter the pleural space and compress the lung tissue, causing atelectasis (collapsed alveoli). At this point, there is no evidence of a tension pneumothorax. Although there is an opening in the chest wall, it is occluded by a foreign body. Air is not entering the wound. Simple pneumothorax is likely; gas exchange is impaired due to atelectasis. There also may be blood from an injured vessel entering the pleural space, which may result in hemothorax. This would both compromise ventilation and result in blood loss that may be significant.
Key Points: Age: the chemoreceptors in the elderly are less sensitive to decreases in oxygen and increases in carbon dioxide. Respiratory rate may not be increased despite inadequate oxygen delivery to the tissues. Preexisting medical conditions Patients with cardiovascular and pulmonary disease cannot compensate well.
Key Points: Reduced carbon dioxide levels leads to cerebral vasoconstriction.
Key Points: Anaerobic metabolism is occurring before signs and symptoms are evident. Management requires definitive treatment of the cause, as well as restoration of tissue perfusion. Airway Ventilation Oxygenation Circulation
Instructor Notes: Solicit responses from participants rather than supply the information yourself. Ask follow-up questions as needed. For example, ask how a suggested intervention will address the patients needs and/or why that intervention is a better choice than other interventions. This verifies understanding of the need to address the underlying pathophysiology of respiratory compromise with interventions. Key Points: The patient is awake and able to speak. He does not need an airway intervention at this point. Since shock, including shock due to respiratory compromise, is progressive and we cannot definitively treat this patient, the airway warrants on-going assessment.
Instructor Notes: Solicit responses from participants rather than supply the information yourself. Ask follow-up questions as needed. For example, ask how a suggested intervention will address the patients needs and/or why that intervention is a better choice than other interventions. This verifies understanding of the need to address the underlying pathophysiology of respiratory compromise with interventions. Key Points: The patient’s respiratory rate is 24 We also need to consider the depth of ventilation to determine adequacy of ventilation. The patient’s tidal volume is decreased from normal, but does not yet require assisted ventilations. Once the ventilatory rate exceeds 30, the tidal volume may be inadequate. He does not yet need assistance, but is approaching the point where ventilatory assistance should be considered We cannot definitively treat this patient, therefore the need for ventilatory assistance must be continually assessed
Instructor Notes: Solicit responses from participants rather than supply the information yourself. Ask follow-up questions as needed. For example, ask how a suggested intervention will address the patients needs and/or why that intervention is a better choice than other interventions. This verifies understanding of the need to address the underlying pathophysiology of respiratory compromise with interventions. Key Points: Anaerobic metabolism occur prior to outward indications This patient is exhibiting signs of compensation, including an increased respiratory rate The increased respiratory rate is an indication of inadequate cellular oxygenation This patient needs oxygen The goal is to maintain an oxygen saturation level of at least 95% The best way to accomplish this is to provide the patient with 12 to 15 liters per minute of oxygen via a non-rebreathing mask
Instructor Notes: Solicit responses from participants rather than supply the information yourself. Ask follow-up questions as needed. For example, ask how a suggested intervention will address the patients needs and/or why that intervention is a better choice than other interventions. Key Points: The patient’s circulatory status is stable for now, but the mechanism of injury is consistent with the potential for internal hemorrhage and shock. The circulatory status must be monitored through on-going assessment
Instructor Notes: Solicit responses from participants rather than supply the information yourself. Ask follow-up questions as needed. For example, ask how a suggested intervention will address the patients needs and/or why that intervention is a better choice than other interventions.
Instructor Notes: Is the patient’s tissue oxygenation adequate?
Key Points: The best airway management and ventilation technique is the one that provides adequate ventilation and oxygenation with the fewest complications.
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