During inspiration, CO2 is essentially zero and thus inspiration is displayed at the zero baseline. Phase 1 occurs as exhalation begins, which is shown as A to B on the capnogram. In phase 3 (C to D on the capnogram), all of the gas passing by the CO2 sensor is alveolar gas which causes the capnograph to flatten out.
- 1 What does the Capnographic waveform represent?
- 2 What causes a sudden increase in the waveform?
- 3 What increases the beta angle in capnography?
- 4 What does a sloped upstroke on capnogram indicate?
- 5 What causes curare cleft?
- 6 What characteristics are observed in a normal capnogram?
- 7 What phase of the Capnogram reflects when the alveoli are full of inhaled oxygen and CO2 levels are very low?
- 8 What causes ETCO2 to increase?
- 9 Why does hyperventilation cause low ETCO2?
- 10 What phase of the capnography waveform is signified by the flat line of inhalation?
- 11 Which phase of the capnography waveform is signified by the ascending line of exhalation?
- 12 Which Capnogram phase is reflected by the change in CO2 concentration as anatomical dead space is replaced with alveolar gas?
- 13 What increases end tidal CO2?
- 14 What does a Capnograph measure?
What does the Capnographic waveform represent?
Waveform capnography represents the amount of carbon dioxide (CO2) in exhaled air, which assesses ventilation. It consists of a number and a graph. The number is capnometry, which is the partial pressure of CO2 detected at the end of exhalation. This is end-tidal CO2 (ETCO2) which is normally 35-45 mm Hg.
What causes a sudden increase in the waveform?
A sudden increase in ETCO2 is seen in ROSC during arrest or correction of an ETT obstruction. This waveform shows a tapering of the ETCO2, suggestive of esophageal intubation.
What increases the beta angle in capnography?
The nearly 90 degrees angle between phase III and the descending limb in a time capnogram has been termed as the beta angle. 5 During rebreathing, there is an increase in beta angle from the normal 90 degrees. As rebreathing increases, the horizontal baseline of phase 0 and phase I can be elevated above normal.
What does a sloped upstroke on capnogram indicate?
Prolongation or slanting of the expiratory upstroke phase II occurs when there is obstruction to expiratory gas flow (e.g., asthma, bronchospasm, obstructive pulmonary disease, and kinked endotracheal tube,1–9 or in the presence of leaks in the breathing system.
What causes curare cleft?
The “curare cleft” seen in the alveolar plateau is actually a patient making an attempt to breathe. With their feeble inspiratory effort, some fresh gas sucked from the ventilator tubing and past the capnometer, generating this pattern.
What characteristics are observed in a normal capnogram?
A normal capnogram for patients of all ages is characterized by a set of specific elements: it includes 4 distinct phases (Figure 1), the CO2 concentration starts at zero and returns to zero (ie, there is no rebreathing of CO2), a maximum CO2 concentration is reached with each breath (ie, ETCO2), the amplitude depends
What phase of the Capnogram reflects when the alveoli are full of inhaled oxygen and CO2 levels are very low?
Phase I (inspiratory baseline) reflects inspired gas, which is normally devoid of carbon dioxide. Phase II (expiratory upstroke) is the transition between VDana, which does not participate in gas exchange, and alveolar gas from the respiratory bronchioles and alveoli. Phase III is the alveolar plateau.
What causes ETCO2 to increase?
In severe cases of respiratory distress, increased effort to breathe does not effectively eliminate CO2. This causes CO2 to accumulate in the lungs and more of it to be excreted with each breath (hypercapnea), which would cause the ETCO2 level to rise.
Why does hyperventilation cause low ETCO2?
Increased work of breathing from pulmonary edema may lead to fatigue and respiratory failure. This would cause a rise in ETCO2, but the waveform will remain upright. Hyperventilation causes excess CO2 to be exhaled, which would present with a crisp waveform and low ETCO2, or hypocapnea.
What phase of the capnography waveform is signified by the flat line of inhalation?
Phase 1 is inhalation. This is the baseline. Since no CO2 is going out when a patient is breathing in, the baseline is usually zero. Phase 2 is the beginning of exhalation.
Which phase of the capnography waveform is signified by the ascending line of exhalation?
Phase II – (B-C): Expiratory Upstroke The ascending phase, CO2 rich air from the alveoli begins to reach the upper airway and mix with the dead space air. CO2 is detected in exhaled air and is identified by the gradual upslope of the horizontal line between the end of phase I and the beginning of phase III.
Which Capnogram phase is reflected by the change in CO2 concentration as anatomical dead space is replaced with alveolar gas?
Phase 2 is characterized by a rapid rise in CO2 concentration as anatomical dead space is replaced with alveolar gas, leading to Phase III.
What increases end tidal CO2?
Problems with the anesthesia machine can cause increased expired carbon dioxide by increasing inspired carbon dioxide. Exhausted soda lime, channeling through the soda lime, or a faulty inspiratory or expiratory valve might increase the end-tidal carbon dioxide level.
What does a Capnograph measure?
Capnography is the measurement of exhaled CO2; the number is. displayed in millimeters of Mercury (mm Hg) or percent (%) CO2. Capnography provides the clinician with a waveform which tracks. exhaled CO2 over time.