(1) tidal volume: in the volume control ventilation mode, the tidal volume should be selected to ensure sufficient gas exchange and patient comfort, and usually 5- 12ml/Kg should be selected according to the body weight, and adjusted according to the compliance and resistance of the respiratory system to avoid the airway platform pressure exceeding 30-35cmH2O. In pressure controlled ventilation mode, tidal volume is mainly determined by preset pressure and inspiratory time. Finally, it should be adjusted according to arterial blood gas analysis. ?
(2) Breathing frequency: The choice of breathing frequency is based on the ventilation volume per minute and the target PCO2 level. Adults usually set it as 12-20 beats/min, and acute/chronic restrictive lung diseases can exceed 20 beats/min. The accurate adjustment of breathing frequency should be based on the changes of arterial blood gas analysis.
(3) Flow regulation: The ideal peak flow should meet the needs of patients' inspiratory peak flow. The flow rate commonly used by adults is set between 40-60L/min, which is adjusted according to the ventilation volume per minute, respiratory system resistance and lung compliance. Clinically, the velocity waveform is usually deceleration wave or square wave. The flow rate in pressure controlled ventilation is affected by the selected pressure level, airway resistance and patient's inspiratory effort. ?
(4) Setting of inspiratory-expiratory ratio (e): Patients with mechanical ventilation usually set inspiratory time to 0.8- 1.2 seconds or set inspiratory-expiratory ratio to1:1.5 ~ 2; Patients with restrictive lung disease generally advocate a longer inhalation time, with a larger I: E (generally 1: 1.0 ~ 1.5) and a longer inhalation time (>: 1.5s), and usually need to use sedatives or muscle relaxants. ?
Patients with obstructive pulmonary disease should appropriately extend the expiratory time and reduce I: E, so as to fully exhale and discharge carbon dioxide. The commonly used I: E is 1: 2.0 ~ 1: 3.0. However, we should pay attention to patients' comfort and monitor PEEPI and its influence on cardiovascular system. ?
(5) Adjustment of trigger sensitivity: In general, the pressure trigger is -0.5 ~ -0.5~-2.0cmH2O, and the flow trigger is 1 ~ 5l/min. Appropriate trigger sensitivity setting will obviously make patients more comfortable and promote man-machine coordination; If the trigger sensitivity is too high, it will cause false trigger unrelated to the patient's exertion. If the trigger sensitivity is too low, it will significantly increase the patient's inspiratory load and consume additional breathing work. ?
(6) Inhaled oxygen concentration (FIO _ 2): At the beginning of mechanical ventilation, high FIO _ 2 (100%) can be given to quickly correct severe hypoxia, and thereafter, according to the target pao _ 2, PEEP level, MAP level and hemodynamic status, FIO _ 2 can be reduced below 50% as appropriate to keep SAO _ 2 > unchanged. 90%, if the above goal cannot be achieved, PEEP can be added to increase the average airway pressure, and sedatives or muscle relaxants can be used; If appropriate, peek? MAP can make Sao 2 >: 90%, and the lowest FiO2 should be kept.
(7) Setting of positive end-expiratory pressure: The function of PEEP is to dilate collapsed alveoli, increase the average airway pressure, improve oxygenation and reduce pulmonary edema, but it will also affect the cardiac blood volume and left ventricular afterload, and overcome the increase of respiratory work caused by PEEP. PEEP is often used for type I respiratory failure represented by ARDS. Based on the reference target PaO2 and oxygen delivery, PEEP is set in combination with FiO2 and VT. Although the upper limit of PEEP is unknown, it is usually set to 5 ~ 20 cmH2O in clinic. PEEP can be set at 3 ~ 5 cmH2O at first, and then increased by 3 ~ 5 cmH2O according to blood gas analysis until satisfactory oxygen saturation can be obtained. The principle is to achieve the best gas exchange and the smallest PEEP with the minimum circulation influence. Hemodynamic changes should be monitored in high level PEEP. ?
(8) alarm limit setting: minute ventilation: the upper and lower limits of alarm should generally be set at 20%-30% above and below the patient's preset minute ventilation; Airway pressure: generally, the upper alarm limit should be set above the peak inspiratory pressure required to maintain the patient's normal tidal volume10-15cm H2O; Inhaled oxygen concentration: the upper and lower alarm limits should be 10%-20% of the preset oxygen concentration? .
(9) Adjust the humidifier: heating and humidifying have the best effect. The gas temperature at the outlet, that is, the humidifier temperature, is generally set at 30 ~ 35℃ and the humidity is 98 ~ 99%. Humidifying liquid can only be distilled water. The high temperature alarm setting cannot be higher than 37? ℃? Low temperature alarm setting value should not be lower than 30℃. ?
(10) Start the ventilator, connect the breathing sac (artificial lung), check whether there is air leakage, observe the expansion and contraction of the breathing sac, and make the ventilator run normally. ?
(1 1) If the ventilator works normally, it should be connected to the human body, closely monitored and further adjusted according to blood gas analysis. Generally speaking, it is required to conduct blood gas analysis half an hour before boarding the computer, and adjust the ventilator parameters according to the results, and then repeat the inspection every 2 hours to prevent the complications of hyperventilation or hypoventilation. Generally, when the oxygen concentration is lower than 0.4 and the oxygen partial pressure is 60mmHg, 24-hour blood gas analysis is allowed.