initiated. Paramedics are also now beginning to monitor the PETCO2 status of nonintubated patients by using a special nasal cannula that collects the carbon dioxide. A high PETCO2 reading in a patient with altered mental status or severe difficulty breathing may indicate hypoventilation and a possible need for the patient to be intubated. Low PETCO2 readings on patients may indicate hyperventilation. Capnography, because it provides a breath by breath measurement of a patient's ventilation, can quickly reveal a worsening trend in a patient's condition by providing paramedics with an early warning system into a patient's respiratory status. When compared to oxygenation which is measured by pulse oximetry, there are several disadvantages that capnography can help address to provide a more accurate reflection of cardiovascular integrity. One shortcoming of measuring pulse oximetry alone is that administration of supplemental oxygen (ie. via nasal cannula) can delay desaturation in a patient if they stopped breathing, therefore delaying medical intervention. Capnography provides a rapid way to directly assess ventilation status and indirectly assess cardiac function. Clinical studies are expected to uncover further uses of capnography in asthma, congestive heart failure, diabetes, circulatory shock, pulmonary embolus, acidosis, and other conditions, with potential implications for the prehospital use of capnography. Registered nurses Registered nurses in critical care settings may use capnography to determine if a nasogastric tube, which is used for feeding, has been placed in the trachea as opposed to the esophagus. Usually a patient will cough or gag if the tube is misplaced, but most patients in critical care settings are sedated or comatose. If a nasogastric tube is accidentally placed in the trachea instead of the esophagus, the tube feedings will go into the lungs, which is a life-threatening situation. If the monitor displays typical waveforms then placement should be confirmed. Diagnostic usage Capnography provides information about production, pulmonary (lung) perfusion, alveolar ventilation, respiratory patterns, and elimination of from the anesthesia breathing circuit and ventilator. The shape of the curve is affected by some forms of lung disease; in general there are obstructive conditions such as bronchitis, emphysema and asthma, in which the mixing of gases within the lung is affected. Conditions such as pulmonary embolism and congenital heart disease, which affect perfusion of the lung, do not, in themselves, affect the shape of the curve, but greatly affect the relationship between expired and arterial blood . Capnography can also be used to