Capnography Flashcards
What is indicated by a prolonged upstroke with increased alpha angle?
Airflow obstruction
Examples include COPD, bronchospasm, and kinked ett.
What causes this waveform?
Cardiac oscillations are caused by the heart beating against the lungs.
In which population are cardiac oscillations more common?
Cardiac oscillations are more common in children due to the close proximity of the heart to the lungs.
What is this waveform? What does it indicate?
Inadequate muscle relaxant reversal.
It indicates a lack of synchronization between intercostal muscles and diaphragm.
Spontaneous breaths during mechanical ventilation.
What is this waveform? What does it mean?
Low EtCO2
• Caused by hyperventilation, low CO2 production, or increased alveolar dead space. *
• Examples hyperventilation: light anesthesia, metabolic acidosis.
• Examples low CO2 production: hypothermia.
• Examples: increased alveolar dead space: hypotension, pulmonary embolism.
What is this waveform? What does it indicate?
Elevated EtCO2 with Normal Baseline
• Look at the baseline. It returns to zero. This is not rebreathing.
• Caused by increased CO2 production or decreased alveolar ventilation.
• Examples increased CO2 production: MH, sepsis, fever, hyperthyroidism.
• Examples decreased alveolar ventilation: hypoventilation, narcotics.
What is this waveform? What does it indicate?
Inspired CO2
• Look at the baseline. It does not return to zero. This is rebreathing-
• Caused by exhausted COz absorbent, incompetent expiratory valve, hole in the inner tube of a Bain system, inadequate FGF with Mapleson circuit, or rebreathing under the drapes in a patient who is not intubated.
What is this waveform? Indicates?
Incompetent Inspiratory Valve
• There’s a decreased slope during the inspiratory phase (widened beta angle). Part of the exhaled breath re-enters the inspiratory limb, so the patient rebreathes some of the previously exhaled CO2 on the next breath.
• The waveform may or may not reach zero, depending on the FGF.
What is this waveform? Indicated?
Biphasic Expiratory Plateaus
• This can occur after a single-lung transplant.
• Alveolar gas from the transplanted lung and the diseased lung have different time constants.
• The first peak is alveolar gas from the transplanted lung. It has a normal time constant.
• The second peak is alveolar gas from the diseased lung. Because air is trapped in the sick lung, there is a longer time constant.
• Biphasic expiratory plateaus have also been reported with severe kyphoscoliosis.
What is this waveform? Indicates?
Leak in Sample Line during Positive Pressure Ventilation
• The beginning of the plateau is low because alveolar gas is diluted when atmospheric air is aspirated into the sample line.
• Positive pressure during inspiration pushes the COz-rich gas through the sample line, which results in the peak at the end of the plateau.
• Not seen with spontaneous ventilation, because there is no positive pressure.
• This pattern may also occur in obese and pregnant patients.
