DM1 Pt5-3 Monitoring the Respiratory System Flashcards
How can manual observation of respiration help determine anesthesia depth?
An increase in anesthesia depth generally reduces respiratory rate and effort, with smaller chest movements during inspiration. However, assessing whether respiratory effort is adequate or if hypoventilation is present is challenging manually.
What does a capnometer measure, and what is a capnogram?
A capnometer measures carbon dioxide concentrations in respired gases, and a capnogram is the graphical representation of these changes throughout the respiratory cycle.
What is the difference between side stream and mainstream capnometers?
Side stream capnometers sample gases through a tube, while mainstream capnometers measure CO₂ directly in the breathing system. Mainstream capnometers have little delay but are heavier and more expensive.
What happens during a normal capnogram?
At the start of expiration, no CO₂ is detected (dead space gases), then CO₂ concentration rises as alveolar gases are exhaled, forming a plateau. End-tidal CO₂ represents the peak CO₂ concentration at the end of expiration.
What is hypoventilation, and how is it detected with capnography?
Hypoventilation is inadequate ventilation, leading to hypercapnia (high CO₂ levels). It appears as increased end-tidal CO₂ on the capnogram.
How does hyperventilation appear on a capnogram?
Hyperventilation, often caused by rapid breathing or excessive ventilator rate, leads to hypocapnia (low CO₂ levels) and appears as a reduced end-tidal CO₂ concentration on the capnogram.
What does rebreathing of CO₂ look like on a capnogram?
Rebreathing is indicated by CO₂ being present during inspiration (the CO₂ level doesn’t fall to zero), and it can result from exhausted soda lime or low flow rates in breathing systems like the Ayres T Piece.
How can a capnogram indicate respiratory obstruction?
Respiratory obstruction appears as a gradual slope at the start of expiration, indicating difficulty in expelling expired gases quickly, and may occur during bronchospasm.
How can capnography inform about cardiovascular status?
A gradual decline in end-tidal CO₂, without changes in respiration, suggests reduced cardiac output since CO₂ transport from tissues back to the lungs is impaired.
What might cause a sudden drop to zero in the CO₂ reading on a capnogram?
A sudden drop to zero likely indicates an equipment problem, such as a blocked sample line in side stream capnometers, rather than a physiological disturbance.
