Chronic obstructive pulmonary disease (COPD) is a kind of chronic bronchitis and (or) emphysema with the characteristics of airflow obstruction, which can further develop into a common chronic disease of or pulmonale and respiratory failure. It is related to the abnormal inflammatory reaction of harmful gases and particles. The disability rate and mortality rate are very high. The global incidence rate of over 40 years old has reached 9%~10%.
（1）Chronic cough is often the earliest symptom. It can’t be healed for life with the development of the disease. It is obvious in the morning, and there are bursts of cough or expectoration at night. When the airway is severely blocked, it is usually difficult to breathe without coughing.
（2）The expectoration is generally white mucus or serous foam sputum, occasionally with bloodshot, and more sputum is discharged in the morning. The amount of sputum increases during the acute attack, and there may be purulent sputum.
（3）Shortness of breath or dyspnea is the main symptom of chronic obstructive pulmonary disease. In the early stage, it appeared during labor, and then gradually became worse, so that it felt short of breath in daily life and even during rest. However, due to abnormal individual difference, some people can tolerate it.
（4）Wheezing and chest tightness occur in some patients, especially in severe patients or acute exacerbations.
（5）Other fatigue, emaciation, anxiety, etc. often occur when chronic obstructive pulmonary disease is serious, but they are not typical manifestations of chronic obstructive pulmonary disease.
Respiratory function is one of the main life functions of the human body, and also an important index for evaluating the severity of chronic obstructive pulmonary disease. In clinical practice, in order to fully understand the pulmonary function of patients, partial pressure of carbon dioxide (PaCO2) and partial pressure of end tidal carbon dioxide (PetCO2) are often used for monitoring. Normal petco2 is around 35-45 mm Hg.
Arterial blood gas monitoring is an invasive operation, which will increase patients' pain, and has the risk of causing ventilator resistance and infection, so its clinical application is limited. PetCO2 is widely used in clinical practice. It can monitor the ventilation function, the change of CO2 production in the body, and the circulatory system. It can also maintain the normal ventilation volume, determine the position of the tracheal tube, timely find the mechanical failure of the ventilator, adjust the parameters of the ventilator, and guide the removal of the ventilator.
① When the patient is breathing autonomously, if the SPO2 and PetCO2 values are normal, the ventilator can be removed;
② If the PetCO2 value gradually increases, it indicates insufficient ventilation；
③ The change of PetCO2 waveform is helpful to find the failure of ventilator, such as connector falling off, loop leakage, tube twisting, tracheal obstruction, etc.
④ Guide the selection of the best positive end expiratory pressure (BEEP). Under normal circumstances, when the PetCO2 value is the minimum, the value of positive end expiratory pressure is the optimal value.
PetCO2 is a continuous non-invasive monitoring, which is simple to operate and can reduce the pain of patients and the workload of nurses. The monitoring values of PetCO2 and PaCO2 in patients with chronic obstructive pulmonary disease (COPD) under different ventilator modes and at different time periods were similar, showing a significant positive correlation.