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What is the volume of gas per unit of time that reaches perfused alveoli?
How can alveolar ventilation be indirectly measured?
Arterial partial pressure of PaCO2
When PaCO2 is decreased, that means that the alveolar ventilation is increased and the patient is....? 3
When PaCO2 is increased, that means that the alveolar ventilation is decreased and the patient is....? 3
What is normal PaCO2?
What is acceptable PaCO2 under anesthesia (supplemented with O2)?
What is the definition of tachypnea?
Rapid respiratory rate
What does a capnometer display? 3
What does a capnograph display? 4
- graph of CO2 partial pressure plotted against time
Why is PaCO2 and EtCO2 not the same?
EtCO2 is lower than PaCO2 because of dead space ventilation
How much is EtCO2 lower than PaCO2 in small animals? Large animals?
- Small - 5 mmHg
- Large - 10 mmHg
What is hypercapnia?
PaCO2 >45 mmHg
What are the effects of increased PaCO2? 3
- Peripheral vasodilation (Increased ICP, decreased BP
- Sympathoadrenal responses (catecholamine release)
What are the two ways to provide intermittent positive pressure ventilation?
- Manual - close the pop-off valve and squeeze reservoir bag
- Mechanical - replace reservoir bag with ventilator
What are some reasons to use intermittent positive pressure? 4
- Constant delivery of inhalant
- Appropriate ventilation and PaCO2
- Improve arterial blood oxygenation
- Maintain ventilation in patients with decreased ability to expand chest/lungs
What variable must be calculated for mechanical ventilation? 4
- Respiratory rate
- tidal volume (Vt)
- peak respiratory pressure (PIP)
- Inspiratory time or inspiratory time: expiratory time ratio (I:E)
What is a good respiratory rate for mechanical ventilation of small animals? Large animals?
- Small - 8-12 bpm
- Large - 6-10 bpm
What is a good tidal volume for patients under mechanical ventilation?
Vt = 10-20 ml/kg
When can the demand valve be used?
Provide ventilation and oxygenation in large animals (not small animals)
What are some disadvantages of intermittent positive pressure ventilation? 2
- Increase pressure inside the chest (decreased venous return)
- Lung injury (alveolar stretching and rupture)
What is the accumulation of acid (H+) inside the body?
What is the accumulation of base (HCO3) inside the body?
What is the result of hypoventilation (increase in PaCO2)?
What is the result of hyperventilation (decrease in PaCO2)?
How are simple acid-base disturbances compensated?
- Fast - respiratory
- Slow - renal
What are most acid-base disturbances in healthy anesthetized patients?
For every 10 mmHg increase in PaCO2, how much will the pH decrease?
When do you see severe acidosis?
- pH < 7.2
- HCO3 < 10 mEq/L
- PaCO2 > 80 mmHg