The height of the capnography waveform accompanies this number on the monitor, as well as the respiratory rate. The amount of CO2 at the end of exhalation, or end-tidal CO2 (ETCO2) is normally 35-45 mm HG. CO2 is a byproduct of cellular metabolism, which gets transported in the blood to the lungs for elimination. Think respiratory failure when ETCO2 is highĬapnography adds objective data to physical exam findings, which helps determine the severity of respiratory distress. A rectangular capnography waveform means that there is no bronchoconstriction, and that no bronchodilator is needed.Ģ. A nebulized bronchodilator would not help, and may harm, respiratory conditions not caused by bronchoconstriction. While both compromise air exchange and increase the effort needed to breathe, air still leaves the alveoli consistently and generates a rectangular capnography waveform. These causes include fluid in the alveoli, such as from CHF, and excessive mucus secretion in the lower airways, such from pneumonia or bronchitis. A nebulized bronchodilator, such as albuterol, is indicated when patients have a shark-fin waveform and bronchoconstriction to open lower airways and increase air movement.Ī rectangular-shaped waveform means that there is no constriction of the lower airways, and that there must be another cause of the patient’s respiratory distress. The more pronounced the shark fin and the longer the exhalation phase, the more constricted the lower airways are. īronchoconstriction may also cause a longer expiratory phase, seen as a longer waveform. This causes the normally rectangular-shaped capnography waveform to have a “shark-fin” appearance. With bronchoconstriction, caused by asthma, COPD, and sometimes pneumonia, air is released inconsistently from the constricted lower airways. A normal waveform is rectangular shaped, with a slight elevation during the plateau. The waveform then slopes downward at the beginning of inhalation and returns to baseline. A spike is seen when CO2-filled air released from the alveoli first passes the nose and lips, and then plateaus when all air is exhaled from the alveoli. The waveform begins at baseline when exhaled air from the dead space in the upper airway reaches the sensor, which contains no measurable CO2. Capnography is measured with an adapter between the bag-valve device and the mask, or with nasal prongs that sample exhaled air from the mouth and nose.

The shape of the capnography waveform represents air movement through the lungs, similar to how an ECG tracing represents electrical activity in the heart.

When added to a thorough history and physical exam, waveform capnography is a valuable assessment tool.

Diminished breath sounds, wheezes, and crackles can be caused by multiple conditions, including asthma, COPD, CHF and pneumonia. The shape of the capnography waveform helps determine the cause of the problemĪccurate diagnosis of the cause of respiratory distress is critical, but can be difficult when the patient has difficulty speaking or multiple chronic respiratory conditions. Here are five things you should know about capnography and respiratory distress:ġ. Waveform capnography is a valuable tool to determine the cause and severity of respiratory distress, to guide treatment decisions, and to monitor the patient’s response to treatment. Respiratory distress is one of the most common patient complaints. Understand how monitoring end-tidal carbon dioxide helps assess and treat a patient in respiratory distress October 3rd, 2018 CapnoAcademy Articles, Columnists Columnists 5 things to know about capnography and respiratory distress

Etco2 capnography