If the waveform is upright and “crisp,” there is no bronchospasm and respiratory distress must be from another cause. The worse the bronchoconstriction, the more pronounced the curve on the waveform. This creates a curve in the initial spike and plateau, or “shark fin” appearance. In cases of bronchospasm, air is is trapped in the alveoli and inconsistently released. The height of the waveform depends on the amount of CO2 detected, and the length of the waveform depends on the time of exhalation. A sharp downward spike is then seen during inhalation. A sharp spike is normally seen when exhaled air from the alveoli reaches the sensor, and plateau’s when all of the exhaled air detected came from the alveoli. There is normally no CO2 present in dead space, and the graph should be at baseline. The waveform starts at the beginning of exhalation, and senses air from dead space in the upper airway and bronchi. The capnography waveform represents air movement in the lungs, similar to how complexes on an ECG represent electrical conduction through the heart.
Adding waveform capnography to history and physical exam findings can help with treatment decisions. A number of conditions can cause diminished breath sounds, wheezing may be heard with both asthma and pulmonary edema, and crackles may be heard with pulmonary edema and pneumonia. Capnography helps diagnose the cause of respiratory distressĬorrectly diagnosing the cause of respiratory distress can be difficult, and treating the wrong condition may cause harm. In this group of patients means that their effort is not effectively eliminating CO2 (hypercarbia), and ETCO2 may rise or fall depending on tidal volume. It is important to understand that patients in respiratory distress may inhale enough oxygen and have a normal pulse-ox reading, but still struggle to get air out, and progress to respiratory failure from fatigue. Patients with asthma, COPD, CHF, and pneumonia must often exert themselves to exhale with accessory muscles. While a rise in CO2 should stimulate someone to breathe, no effort should be needed to exhale it. Once ventilation is assisted with a bag valve mask, ETCO2 would spike until the excess CO2 is washed out of the lungs. 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
Here are five things you should know about waveform capnography.
0 kommentar(er)
