Ventilators are generally divided into:
Normal-frequency ventilators (adult 10~60 times)
High-frequency ventilators (adult >60 times)
Exercorporeal modeling of lungs
Normal-frequency ventilators also include: positive-pressure ventilators and negative-pressure ventilators, and the most commonly used is the positive pressure ventilator in the airway. A perfect ventilator consists of three parts: air supply device, control device and patient airway.
1. air supply device
by the air compressor (to provide high-pressure air), oxygen supply device or oxygen cylinder (to provide high-pressure oxygen) and air-oxygen mixer composition. Mainly to provide the patient inhalation of oxygen concentration of 21% ~ 100% of the high oxygen gas.
2. Control device
Intelligent processing of the set parameters and measured values by the computer, through the controller sends out different commands to control the sensors, exhalation valves, inhalation valves to meet the requirements of the patient's breathing.
3. Patient airway
Consisting of gas pipeline, humidifier, filter and so on.
In the use of ventilator operation, the first need to select and set many parameters, which also requires belonging to the non-clinical engineering personnel and clinical medical personnel, as well as to understand the meaning of the basic parameters, requirements, scope, etc.. Now through the introduction of the basic operation of the ventilator to understand its basic parameters of the selection and setting.
1. Respiratory mode selection
In the operation of the ventilator, the first step is to select the patient's respiratory mode, the most commonly used in modern models have three modes:
(1) A/C (assisted/control ventilation): when the patient has spontaneous respiration, the machinery is started with the respiration, and once the spontaneous respiration does not occur for a certain period of time, the mechanical ventilation is automatically switched to the control-type ventilation from the auxiliary. It belongs to the category of intermittent positive-pressure ventilation. It belongs to intermittent positive pressure ventilation.
(2) SIMV (synchronized intermittent command ventilation): the ventilator receives signals of negative pressure in the airway due to spontaneous breathing at certain intervals, and sends out the airflow synchronously, and carries out assisted ventilation intermittently.
(3) SPONT (spontaneous breathing): the work of the ventilator is controlled by the patient's spontaneous breathing.
In the above three basic modes, all types of ventilators are also designed for a variety of diseases of the respiratory function for the use of choice. For example:
(a) PEEP (Positive End-of-Expiratory Pressure): On the basis of mechanical ventilation, a resistance is exerted on the airway at the end of expiration, so that the pressure in the airway is maintained at a certain level.
(b)CPAP (Continuous Positive Airway Pressure Ventilation): Under the premise of spontaneous breathing, a certain level of positive airway pressure is artificially applied throughout the respiratory cycle. It prevents intra-airway atrophy.
(c) PSV (pressure support): receiving a degree of pressure support with each inhalation under conditions of voluntary breathing.
(d)MMV (scheduled minute ventilation): if the minute ventilation of SPONT is lower than the limit, the insufficient air volume is supplied by the ventilator; if the minute ventilation of SPONT is greater than the limit, the ventilator stops supplying air automatically.
(e) BIPAP (bi-level intra-airway positive pressure): the patient breathes spontaneously at different high and low levels of positive pressure. It can be regarded as PSV + CPAP + PEEP.
(f)APRV (Airway Pressure Release Ventilation): ventilation created by opening a low-pressure valve to temporarily deflate and reduce airway pressure in the CPAP state.
2. Ventilation mode selection
After selecting the breathing mode, it is necessary to select or to know the ventilation mode:
(1)Volume-controlled ventilation (VCV): set a tidal volume, which is regulated by the flow rate × inspiratory time.
(2) Pressure-controlled ventilation (PCV): set a pressure, which is determined by inspiratory plateau pressure.
3. Trigger mode selection
(1)Pressure trigger: when the pressure in the pipeline reaches a certain limit, the breath is switched.
(2) Flow trigger: when the flow rate in the pipeline changes to a certain value, the breath is switched. Because of its high sensitivity and short lag time, it has been widely used.
(3) Time switching: controlled by the time, the set time arrives, the breath that switch.
4. alarm parameter selection
The settings of various parameters of the ventilator are interrelated, so we need to know the basic meaning of the various settings and the range of normal values in order to accurately set the alarm parameters. The physiological indexes for adult application of ventilator are: tidal volume 5-7ml/kg; respiratory rate 12-20 times/min; airway pressure 30-35cmH2O; ventilation per minute 6-10l/min.
In the use of ventilator, the setting of upper and lower alarm limits is also very important. If the alarm setting is too close to the patient's actual value, it will cause the ventilator to alarm frequently; and if the alarm setting range is too large, it will lose the significance of the alarm. Because of the different models of the alarm settings are different, but generally should be:
(1) pipeline pressure upper and lower limits of the alarm.
(2) the lower and upper limits of the moisture volume alarm.
(3) Apnea interval alarm.
(4) Minute ventilation upper and lower limits alarm.
(5) Upper and lower limits of respiratory rate alarm.
These are the basic parameters that need to be selected and set in the operation of the ventilator. Here is only the most basic concepts of all types of ventilators **** have. Various brands of ventilators are based on this and then develop some new features, and these features are mainly for clinical use