Anatomy and Physiology Review
- The upper and lower airway
- The alveoli and pulmonary capillaries
Key Concepts: Respiratory Physiology
- Minute volume: Tidal volume × rate
- Alveolar ventilation: The amount of air that actually reaches the alveoli
- External respiration: The exchange of oxygen and carbon dioxide from air to blood at the level of the alveoli
- Requires adequate ventilation of the alveoli and blood flow to the pulmonary capillaries
- Internal respiration: The exchange of oxygen and carbon dioxide from blood to the cells of the body
- Requires external respiration first and adequate blood flow to the cells
The Pathophysiology of Hypoxia
- Actual obstruction of the airway
- Decreased mental status leading to relaxation of airway structures such as the tongue
- Foreign body airway obstruction, such as from blood or objects (as in choking)
- Disruption of alveolar ventilation
- Obstruction of air flow in the lower airways, such as from bronchoconstriction (as in asthma)
- Changes in the alveoli and small airways, such as pulmonary edema
- Inadequate breathing
- Rate problems leading to inadequate minute volume, such as very slow breathing (narcotic overdose)
- Volume problems leading to inadequate breathing, such as with a collapsed lung (pneumothorax)
- Disordered control of breathing
- Conditions such as seizures or brain injury that challenge the ability to keep an airway open or maintain adequate breathing
- Respiratory decompensation after prolonged compensation for a respiratory challenge
- Muscles of respiration failing as the ability to supply oxygen to them is outpaced by the increased demand and overall respiratory challenge
- Exhaustion
Signs and Symptoms of Inadequate Breathing and Hypoxia
- Changing and decreasing mental status
- Anxiety and fear as hypoxia begins
- Mental status depression as hypoxia and high levels of carbon dioxide build
- Be aware that mental status can affect the patient’s ability to keep an airway open
- Cyanosis
- Dyspnea and respiratory distress
- Respiratory fatigue/slowing or irregular respirations
- Inability to speak/move air (silent chest)
- Accessory muscle use
- Lung sounds
- Diminished volume: decreased sounds of moving air
- Adventitious sounds: stridor, wheezing, rales and rhonchi
- Pulse oximetry (readings lower than 94%)
Key Interventions: Supplemental Oxygen
- Indication = Hypoxia (saturations less than 94% and/or other signs of hypoxia)
- Precautions = Hyperoxia
- Hyperoxia is a condition caused by excessive oxygen administration that leads to abnormally high partial pressures of oxygen in the blood plasma
- Hyperoxia may be linked with cellular death and coronary artery obstruction
- Never withhold oxygen from a patient who is demonstrating signs of hypoxia
- Oxygen is an accelerant—exposure to flame must be avoided!
- Secure tanks
- Avoid smoking or open flame near oxygen delivery devices
- Prevent tank drop; always secure oxygen cylinders
- Prepare properly for administration
- Clear the tank and attach the regulator, assuring proper alignment of regulator pins
- Check for leaks
- Assemble Regulator
- Oxygen delivery devices (consider concentration delivered and technique for use)
- Nonrebreather mask (12–15 Lpm)
- Used to deliver the highest concentration of inspired oxygen (80–90%) to hypoxic patients
- Partial rebreather masks (9–10 Lpm)
- Similar to nonrebreather but with open valve(s) in face mask
- Used to deliver slightly lower concentrations of oxygen (40–60%) to patients who may require more precise management of oxygen levels and CO2 levels, such as end-stage COPD patients
- Simple face masks (9–10 Lpm)
- Face mask with no rebreather bag attached
- Used to deliver slightly lower concentrations of oxygen (40–60%) to patients who do not require high-concentration oxygen to maintain saturation; commonly used in COPD patients
- Tracheal masks are a variation of the simple face mask and are designed to be placed over open stomas or tracheal tubes to deliver medium-concentration oxygen (40–60%)
- Venturi masks (1–15 Lpm)
- Adjustable liter flow masks designed to provide variable oxygen concentrations (24–60%) to patients who require precise low to medium concentrations, such as end stage COPD patients
- Nasal cannula (2–6 Lpm)
- Nasal prong system designed to deliver low-concentration supplemental oxygen
- Often better tolerated by mildly hypoxic patients
- Nonrebreather mask (12–15 Lpm)
Key Concepts: Positive Pressure Ventilation (PPV)
- Indication: Used in situations in which the patient’s breathing and/or respiratory effort is inadequate
- Goals: To restore minute volume and alveolar ventilation to a patient who is not breathing or is breathing inadequately
- Hazards and side effects:
- Does not resolve breathing problems such as bronchospasm
- Potential gastric insufflation (air into the stomach), displacing the diaphragm and decreasing lung capacity (especially in children)
- Potentially stretches lung tissue and increases intrathoracic pressure, which can lead to decreased preload and diminished cardiac output
Performance Points: Positive Pressure Ventilation
- Open and maintain a patent airway
- Suction/clear obstructions prior to PPV
- Consider head elevated sniffing position (align level of the ear with supersternal notch and keep level of the face parallel to the ceiling)
- Consider using airway adjunct
- Seal the mask
- First, place mask on face, unattached to bag device
- Choose proper mask size (must fit from bridge of the nose to cleft of the chin and be wide enough to cover lateral aspects of mouth)
- Remember that using two hands to seal the mask is always better than using only one
- Use two hands to apply the thenar eminence technique (palms on mask and fingers of both hands using modified jaw thrust to pull mandible into mask
- Only when absolutely necessary, use one hand to apply EC clamp (thumb and first digit holding the mask, remaining fingers using a modified jaw thrust to pull mandible into mask)
- Ventilate properly
- Ventilate nonarrest adult patients 10–12 breaths per minute (every 5–6 seconds)
- Ventilate nonarrest pediatric patients 12–20 breaths per minute (every 3–5 seconds)
- In cardiac arrest situations, ventilate using compression-to-ventilation ratios of CPR (30:2 or 15:2 for multiple rescuer pediatrics)
- In cardiac arrest situations when an advanced airway is placed, ventilate patients at 10 breaths per minute (every 6 seconds) and perform continuous chest compressions
- Ventilate slowly and gently, using just enough air to move the chest. Stop once chest rise is visualized
- Flow-Restricted, Oxygen-Powered Ventilation Device may be used (check local protocol)
Important Concepts : PPV and Supplemental Oxygen
- Although you may be concerned right now about studying for the big exam, remember that the true test is using these skills to do well for a patient in a critical situation. Therefore, think less about memorizing lists and more about how you would use each of these techniques in an actual situation. In the end, this method will also help you on the exam.
- Recognizing respiratory/airway failure is the key first step to initiating PPV. Be sure you are prepared to identify it and take immediate action. Know the indications for PPV.
- Hypoxia exhibits different signs and symptoms in different patients. Always have a high index of suspicion, recognize subtle findings, and err on the side of caution.
- Study Tip: Consider each of the pathophysiologies listed here. How would you recognize it, and what steps would be necessary to treat it?
- Study Tip: Consider each skill and intervention in context. How would you use the device or intervention in a real person? In what type of situation would you use the device/intervention?