Respiratory Monitoring Flashcards
What is resistance in the context of pulmonary mechanics?
Resistance is the force that acts opposite to the relative motion of an object.
Define compliance as it relates to the lungs.
Compliance is the ability of the lungs to stretch and expand.
What are the two types of pulmonary compliance?
- Static compliance
- Dynamic compliance
What is peak inspiratory pressure (PIP)?
PIP is the maximum pressure in the patient’s airway during inspiration.
What is plateau pressure (PP)?
PP is the pressure in the small airways and alveoli after the target tidal volume is achieved.
How can we evaluate alterations in pulmonary mechanics?
By evaluating the PIP and PP to determine if changes are due to resistance or compliance.
What does increased resistance manifest as in terms of PIP and PP?
Increased PIP with a normal PP.
What does decreased pulmonary compliance manifest as in terms of PIP and PP?
Increased PIP and PP.
Examples: Increased Resistance
- Kinked endotracheal tube
- Endotracheal tube cuff herniation
- Bronchospasm
- Bronchial secretions
- Compression of the airway
- Foreign body aspiration
Examples: Decreased Compliance
- Endobronchial intubation
- Pulmonary edema
- Pleural effusion
- Tension pneumothorax
- Atelectasis
- Chest wall edema
- Abdominal insufflation
- Ascites
- Trendelenburg position
- Inadequate muscle relaxation
What does increased PIP with no change in PP indicate?
Resistance has increased or inspiratory flow rate has increased.
What happens when increased PIP and increased PP occur?
Total compliance has decreased (P-elastic has increased) or tidal volume has increased.
Example: Decreased Compliance
What does capnography measure?
Capnography measures the end-tidal CO₂ concentration over time.
What does capnography assess?
It permits continuous assessment of metabolism, circulation, and ventilation.
What insight does capnography provide?
It provides insight into equipment-related problems, including airway obstruction and rebreathing.
What does an increased alpha angle suggest?
An increased alpha angle suggests expiratory airway obstruction.
What does an increased beta angle indicate?
An increased beta angle suggests rebreathing due to a faulty inspiratory valve.
What are the two methods of carbon dioxide analysis?
The two methods are mainstream (in-line) and sidestream (diverting).
What occurs during Phase I (A-B) of exhalation?
Exhalation of anatomic dead space
What occurs during Phase II (B-C) of exhalation?
Exhalation of anatomic dead space + alveolar gas
What occurs during Phase III (C-D) of exhalation?
Exhalation of alveolar gas
What occurs during Phase IV (D-E) of respiration?
Inspiration of fresh gas that does not contain CO2
What is the alpha angle measured at?
Point C
What is the normal range for the alpha angle?
100-110 degrees
What does an increased alpha angle signify? Examples?
An expiratory airflow obstruction, such as COPD, bronchospasm, or a kinked endotracheal tube
Where is the beta angle measured?
The beta angle is measured at point D.
What happens to the capnograph when the patient inspires fresh gas?
The capnograph should immediately return to zero.
What angle is created at point D when the capnograph returns to zero?
This creates a 90-degree angle at point D.
How is the beta angle affected by rebreathing?
The beta angle is increased in some (but not all) etiologies of rebreathing.
Is the beta angle specific to any causes of rebreathing?
It’s specific to rebreathing caused by a faulty inspiratory valve.
What happens to the beta angle in other instances of rebreathing?
It will appear normal in instances of rebreathing caused by exhausted CO2 absorbent.
What are causes of increased EtCO2?
Causes include:
* Increased CO2 production and delivery to the lungs (e.g., malignant hyperthermia, thyrotoxicosis, tourniquet removal)
* Decreased alveolar ventilation (e.g., CNS depressant drugs, COPD, residual neuromuscular blockade)
* Equipment malfunction (e.g., CO2 absorbent exhaustion, unidirectional valve malfunction, increased apparatus dead space)
Increased EtCO2 indicates higher levels of carbon dioxide in exhaled air, often due to various physiological or equipment-related factors.
What are causes of decreased EtCO2?
Causes include:
* Decreased CO2 production and delivery to the lungs (e.g., hypothermia, decreased cardiac output, V/Q mismatch, pulmonary embolus)
* Increased alveolar ventilation (e.g., iatrogenic hyperventilation, inadequate anesthesia)
* Equipment malfunction (e.g., esophageal intubation, poor seal with an LMA, sample line leak)
Decreased EtCO2 levels can indicate reduced carbon dioxide levels in exhaled air, which may arise from various medical conditions or equipment issues.
Fill in the blank: Increased EtCO2 can result from _______ ventilation.
Decreased alveolar
Decreased alveolar ventilation can lead to increased carbon dioxide retention in the lungs.
True or False: Malignant hyperthermia can cause increased EtCO2.
True
Malignant hyperthermia is a condition that increases metabolism, leading to higher CO2 production.
Fill in the blank: Equipment malfunction, such as _______ absorbent exhaustion, can lead to increased EtCO2.
CO2
CO2 absorbent exhaustion in anesthesia machines can result in inadequate removal of carbon dioxide.
What is a cause of decreased CO2 production and delivery to the lungs?
Causes include:
* Hypothermia
* Decreased cardiac output
* V/Q mismatch
* Pulmonary embolus
These conditions can lead to less carbon dioxide being transported to the lungs for exhalation.
What law is the pulse oximeter based on?
The pulse oximeter is based on the Beer-Lambert law, which relates the intensity of light transmitted through a solution (blood) and the concentration of the solute (hemoglobin) within the solution.
How does the pulse oximeter compare light absorption?
It compares the ratio of light absorption in arterial and venous blood throughout the pulse cycle.
What wavelengths of light does the pulse oximeter emit?
The pulse oximeter emits two wavelengths of light at a constant intensity: red light (660 nm) and near-infrared light (940 nm).
What is red light preferentially absorbed by?
Red light (660 nm) is preferentially absorbed by deoxyhemoglobin, which is higher in venous blood.
What is near-infrared light preferentially absorbed by?
Near-infrared light (940 nm) is preferentially absorbed by oxyhemoglobin, which is higher in arterial blood.
Where are monitoring sites with faster response times located?
Monitoring sites closer to the central circulation, such as the forehead or ear, have faster response times than sites like the toe.
What is Left Shift?
Increased Affinity for O2 (left = love)
Occurs in the lungs
What are the conditions that cause Left Shift?
Low Temperature, Low 2,3-DPG, Low CO, Low hydrogen, Increase pH, Increase HgbMet, Increase HgbCo, Increase Hgb F
What is Right Shift?
Decreased Affinity for O2 (right = release)
Occurs near metabolically active tissue
What are the conditions that cause Right Shift?
Increase Temperature, Increase 2,3-DPG, Increase [H+], Low pH
What is the PaO2 when SpO2 is 90%?
PaO2 is approximately 60 mmHg.
Example: SpO2 90% = 60 PaO2
What is the PaO2 when SpO2 is 80%?
PaO2 is approximately 50 mmHg.
Example: SpO2 80% = 50 PaO2
What is the PaO2 when SpO2 is 70%?
PaO2 is approximately 40 mmHg.
Example: SpO2 70% = 40 PaO2
What are methods to improve the SpO2 signal?
- Place a digital block
- Warm the extremity
What does a pulse oximeter monitor?
A pulse oximeter is a noninvasive monitor of hemoglobin saturation, heart rate, fluid responsiveness (pulse pressure variation), and perfusion.
What is a pulse oximeter NOT a good monitor of?
A pulse oximeter is NOT a good monitor of anemia, ventilation, or bronchial intubation.
What is compliance equation in the context of airway?
Compliance is a change in volume for a given change in pressure.
What does compliance measure?
It measures the elastic properties of the lungs and chest wall.
What factors influence airway compliance?
Muscle tone, degree of lung inflation, alveolar surface tension, amount of interstitial lung water, and pulmonary fibrosis.
What is dynamic compliance?
Dynamic compliance is the compliance of the lung/chest wall during air movement.
What does dynamic compliance depend on?
The pressure required to inflate the lung to a given volume is a function of airway resistance AND the tendency of the lung/chest to collapse.
What is static compliance?
Static compliance measures lung compliance when there is no airflow.
What does ‘stasis’ mean in the context of compliance?
‘Stasis’ means ‘not moving.’
What is the PIP?
The PIP is the maximum pressure in the patient’s airway during inspiration.
It is affected by airway resistance as well as chest/lung compliance.
How is Dynamic Compliance calculated?
Dynamic Compliance = Tidal Volume / (Peak Inspiratory Pressure - PEEP)
What is Plateau Pressure (PP or Pplateau)?
Plateau pressure is the pressure in the small airways and alveoli after the target tidal volume is delivered.
Since there is no airflow at this time, airway resistance does not affect plateau pressure.
What does Plateau Pressure reflect?
Plateau pressure reflects the elastic recoil of the lungs and thorax during the inspiratory pause.
What is the risk associated with elevated Plateau Pressure?
Barotrauma risk increases when plateau pressure exceeds 35 cm/H2O.
What are complications of elevated Plateau Pressure?
Complications include ventilator associated lung injury, pneumothorax, pneumomediastinum, and subcutaneous emphysema.
How can you reduce Plateau Pressure if barotrauma exists?
Aim to reduce plateau pressure by reducing tidal volume, inspiratory flow, and PEEP. Sedation is also helpful.
How is Static Compliance calculated?
Static Compliance = Tidal Volume / (Plateau Pressure - PEEP)
What is the normal range for Static Compliance in adults?
In the adult, normal static compliance is 35 - 100 mL/cm H2O.
What is the normal Static Compliance in children?
In the child, normal static compliance is > 15 mL/cm H2O.
