Other causes of respiratory failure present with inadequate respiratory rate and depth, and since little exhaled air would reach the sensor on the capnography circuit, the ETCO2 reading would be low. Some causes of respiratory failure present with adequate tidal volume but slow respiratory rate, and in these cases ETCO2 would be high (above 45 mm Hg) and continue to rise if not addressed. When the brain does not respond appropriately to CO2 changes, such as from overdose, head injury or seizure, excess CO2 accumulates in the lungs, though the ETCO2 reading may be low or high. Waveform capnography is a useful tool to identify when patients with an altered mental status need assisted ventilation with a bag valve mask. The patient’s respiratory rate should increase as CO2 rises, and decrease as CO2 falls. ETCO2 adds an objective measurement to those findings. We assess this by observing chest rise and fall, assessing respiratory effort, counting respiratory rate, and listening to breath sounds. In people with healthy lungs, the brain responds to changes in CO2 levels in the bloodstream to control ventilation. ETCO2 provides clues about respiratory effort Pulse-oximetry assess oxygenation, and works by measuring the how much of each red blood cell is bound with oxygen. Ventilation is the air movement in and out of the lungs, while oxygenation is the amount of oxygen inhaled by the lungs that reaches the bloodstream. In patients who require assisted ventilation, another adapter can be attached to a BVM and advanced airway device.Ĭapnography assesses ventilation, which is different from oxygenation. Those prongs can also be used to administer a small amount of oxygen, or applied underneath a non-rebreather or CPAP mask. In patients who are breathing, nasal prongs can be applied that capture exhaled air. Two sensors can be used to measure capnography. Changes in respiratory rate and tidal volume are displayed immediately as changes in the waveform and ETCO2. Capnography also measures and displays the respiratory rate. The capnograph is the waveform that shows how much CO2 is present at each phase of the respiratory cycle, and it normally has a rectangular shape. This is end-tidal CO2 (ETCO2) which is normally 35-45 mm Hg. The number is capnometry, which is the partial pressure of CO2 detected at the end of exhalation.
Waveform capnography represents the amount of carbon dioxide (CO2) in exhaled air, which assesses ventilation. Capnography provides breath-to-breath ventilation data
There is incredible utility in using EtCO2 in CPR.Here are five things you should know about waveform capnography. The correlation between serum pCO2 and EtCO2 is also less understood animal studies do not show much correlation, and as you would expect with CPR, there will likely be some dead space and/or V/Q mismatch. The utility of EtCO2 in patients who are receiving bag mask ventilation (BVM) or have a laryngeal mask airway (LMA) is less understood and researched.
The PQRST mnemonic should be applied to patients with an ETT. Approximately 20 minutes into a resuscitation, the likelihood of ROSC is significantly higher if EtCO2 >20 mm Hg and much less if EtCO2 <10 mm Hg. Termination (T)ĮtCO2 may provide an additional data point when deciding whether it is appropriate to terminate CPR. This can be seen in bronchospasm or a kinked or blocked ETT or circuit. This is an example of a waveform that looks like a “sharkfin,” which indicates expiratory obstruction.
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