What Is Pressure Support Ventilation?

In modern clinical medicine, the ventilator, as an effective means to artificially replace the autonomous ventilation function, has been widely used in respiratory failure caused by various reasons, anesthesia and respiratory management during major surgery, respiratory support treatment and emergency resuscitation. Occupies a very important position in the field of modern medicine. The ventilator is a vital medical device that can prevent and treat respiratory failure, reduce complications, save and extend the life of patients.

One. Classified by type of use or application

(1) Controlled Mechanical Ventilation (CMV) Definition: When the patient's spontaneous breathing weakens or disappears, the patient's breathing is generated, controlled, and regulated entirely by a mechanical ventilator. 2. Application: The spontaneous breathing disappears or weakens due to the disease; the spontaneous breathing is irregular or the frequency is too fast, and mechanical ventilation cannot be coordinated with the patient, and the spontaneous breathing is artificially suppressed or weakened.

(B). Auxiliary Mechanical Ventilation (AMV) Definition: In the presence of patient breathing, the ventilator assists or enhances the patient's spontaneous breathing. The various types of mechanical ventilation are mainly triggered by the patient's inspiratory negative pressure or inspiratory airflow. 2. Application: Although spontaneous breathing exists and is more regular, patients with spontaneous breathing weakened and insufficient ventilation.

two. Classified by use of mechanical ventilation

(A) intrathoracic or airway compression type

(Two) chest shape

three. Classification by switching between inhalation and exhalation

(1) Constant pressure type: After the pressure in the airway reaches the expected value, the ventilator opens the exhalation valve, and the thoracic and lungs passively collapse or exhale due to negative pressure. When the pressure in the airway continues to drop, the ventilator passes the positive pressure again Generates airflow and causes inhalation.

(2) Constant volume type: The expected tidal volume is sent into the lungs by positive pressure. After reaching the estimated tidal volume, the air supply is stopped and the state of expiration is entered.

(3) Timing type: supply air according to the pre-designed inspiratory and expiratory time. (4) Hybrid (multifunctional).

four. Supply air at the ventilation frequency

(1) High-frequency ventilation: ventilation frequency> 60 times / minute. 1. Advantages: low airway pressure, low intrathoracic pressure, little interference to the circulation, no need to close the airway. 2. Disadvantages: Not conducive to the removal of carbon dioxide. 3 Classification: high frequency positive pressure ventilation, high frequency jet ventilation, high frequency oscillating ventilation.

(2) Ordinary frequency ventilation: ventilation frequency <60 times / minute.

Fives. Classified by sync device or performance

(1) Synchronous ventilator: When the patient's spontaneous breathing starts, the ventilator can be triggered to supply air to the patient's respiratory tract and produce an inspiratory action.

(2) Non-synchronized ventilator: The patient's breathing or inspiratory negative pressure cannot trigger the ventilator to supply air, and it is generally only used for patients with controlled mechanical ventilation.

six. Classified by applicable objects

(1) Baby ventilator

(2) Infant ventilator (3) Adult ventilator

Seven. Classified by working principle

(1) Simple ventilator

(Two) membrane lung

1 Microcomputerized degree of ventilator The degree of microcomputerization of the ventilator determines the grade of the ventilator, which is manifested in: (1) It has a self-test function after it is turned on. (2) There is a screen prompt when a failure occurs, which is convenient for maintenance. (3) Perfect alarm functions, such as oxygen supply, gas supply, minute ventilation, upper pressure limit, lower pressure limit, respiration rate, tidal volume, apnea ventilation, background ventilation settings, machine disconnection, air leakage and air leakage, flow Sensors, working status, oxygen flow and many other links ensure the safety of mechanical ventilation. Clinicians can adjust the alarm range set by parameters according to the patient status. (4) Other special functions, including sputum suction function, atomization function, breath-holding function (including inhalation and expiration breath-holding, to meet the needs of chest radiographs), and lock function (to prevent the ventilation parameters from being arbitrarily changed).

2 Ventilator monitoring function Ventilator monitoring function is one of the key links in determining the grade of the ventilator. A complete ventilator monitoring function is an important prerequisite for achieving a ventilator suitable for the pathophysiological changes of the lungs of patients, not only displaying conventional ventilation and lung mechanical parameter values, such as VTe, VT, R, c, f, airway temperature, Fio2, Pp resistance k, P, Pn-, VA, VAleak, I: E and can further display: (1) pressure-time, volume-time, flow rate-time curve can be displayed on a single screen or simultaneously. (2) spo2, ETCO2 and calculate VD / VTe, co2 production. (3) Monitor the traces of curve rings such as Paw-V, V-Flow, Flow-Paw, V-co2, Ptrach-V, Flow-Ptrach. (4) Trend review (24-48 hours). (5) The logbook is a review of the set values of ventilator application events. (6) Calibration function, including the calibration of co2, Flow, o2. (7) Ventilation and various function settings: the volume of the volume, different combinations of screen display, arbitrary ventilation mode selection (more than 10 commonly used methods), a variety of voice settings and so on. (8) The ventilator allows the user to trace the P-V curve [1,2,3 J with low flow rate method to further understand the patient's pulmonary static compliance (c), resistance (R) and endogenous PEEP (PEEPi). In addition, it provides a basis for better adjustment of ventilation parameters. The curve can be used to calculate the up-and-down inflection point, complex tensor, and print the record online with the computer. (9) The ventilator integrates other devices (Bi-core respiratory monitor) to enhance the solution of problems that cannot be understood by breathing parameters alone during ventilation, such as respiratory mechanics monitoring, placement of esophageal pressure, and monitoring of intragastric pressure to understand Transpulmonary pressure, transcondylar pressure, and dynamic auto-PEEP can further clarify the status of respiratory mechanics and provide scientific research space for clinical professionals. (10) After years of clinical practice, foreign ventilator manufacturers have integrated some useful parameters such as RVR, MIP, Po. 1. PlP and au grid P are put into the monitoring system _4J, which provides the basis for the adjustment and offline setting of the clinician. In recent years, the automated offline mode has risen quietly. _5. 5. The ventilator also integrates important parameters, weight and ideal ventilation parameters, BGA of the patient, which improves the level of mechanical ventilation and shortens the time of taking the machine. In short, the microcomputerization and network of the ventilator provide a scientific research platform for mechanical ventilation and promote the development of the level of mechanical ventilation application _6J.

3 The development of the ventilator model is an important manifestation of the level of the ventilator. Regardless of whether the ventilator is volume control or pressure control, it causes ventilator-related lung injury to varying degrees (Ventilator-induced Lung Inj ~ y VILI). Many foreign countries have done a lot of basic and clinical research in this area, and made major reforms based on the original IPPV, IMV, SIMV, PSV, etc. Many studies have shown that the autonomous model of pressure can well implement the non-protection strategy and maximize the maximum Reduce the occurrence of VILI, and further expand the role of ventilator as a clinical treatment. (1) Today's ventilator applications from newborn to adult, only need to replace the humidifier and tubing; mechanical ventilation from non-invasive to invasive, non-invasive ventilation has strong leakage compensation. (2) Adding Autoflow (autonomous airflow) or flow-by in the volume control ventilation mode further increases the patient's autonomy, reduces airway pressure, increases patient comfort, and overcomes the disadvantages of the volume ventilation mode. (3) Ventilator aspiration response time (30-40ms), aspiration waveform (square wave-constant current, deceleration wave), trigger sensitivity is adjustable by flow velocity trigger, pressure trigger is abandoned, PSV mode exhalation sensitivity (Es. end) adjustable. Under the monitoring of a ventilator, the clinician can easily adjust the patient's Esem, thereby solving the human-computer interaction mode to minimize the interference with cardiopulmonary function and the occurrence of VILI. (4) International clinical practice has further confirmed that pressure ventilation mode is superior to volume control in maintaining positive airway pressure, reducing cardiopulmonary interference, improving oxygenation, and minimizing the occurrence of VILI. Based on PCV, BiPAP / PS and APRV have been introduced in recent years. In particular, the BiPAP ventilation mode has pressure control and good man-machine coordination. The universal ventilation mode has been adopted by many ventilator manufacturers and is named: Bilevel, duoPAP and other names. (5) Autonomous ventilation and closed-loop ventilation mode: Experiments and clinical applications have shown that the controlled ventilation time is minimized to minimize the occurrence of VILI, and to shorten the take-up time. Many studies have shown that spontaneous breathing has many advantages and is conducive to the recovery of patients' physiological changes. Spontaneous breathing is no longer the simple Spon mode in the past, but a servo mode and closed-loop ventilation mode. Its biggest advantage lies in the system. The internal output information can be precisely controlled. Can reach the steady state quickly under the premise of zero error, and can eliminate all kinds of external interference. The mechanical ventilation technology using the closed-loop control principle can be quite simple or complicated. The simplest closed-loop control is to control an output variable, such as PSV, based on inputting a message. Relatively complex closed-loop control can continuously regulate multiple output variables based on multiple input information. Dual control is the simultaneous control of output pressure and volume during one ventilation or each ventilation. The ventilation technology using the principle of dual control in one ventilation has the capacity to ensure pressure support ventilation (VI) and pressure augmentation (PA). Its ventilation goal is to reduce the patient's inhalation work while ensuring the minimum inhaled tidal volume and minute ventilation. Others include: PRVC, autoflow, VTPC (volume calibration pressure control). Its technical principle is that the ventilator follows the patient's respiratory mechanics. The change in characteristics automatically adjusts the inspiratory pressure and inspiratory flow rate to ensure that vT tends to be constant with each ventilation. The ventilator performs negative feedback control for each ventilation. Closed loop ventilation is divided into positive feedback ventilation (PAV), negative feedback ventilation (APV, ASV, PRvC), closed-loop ventilation (MMV, APV, ASV) and closed-loop ventilation (nw) based on closed-loop ventilation control principles.

In the past 20 years, PSVE7,8,9J have been welcomed by clinicians, and the success rate of ventilator-dependent patients has been improved. Given that PSV is a constant-pressure inspiratory support, at low levels of Ps, the generation of VT must be over-supported. , Support is equivalent, support is less than three stages, this mode has inhalation delay and expiration delay, when this mode is applied, human-machine synchronization is prone to occur. In recent years, many manufacturers have increased the expiratory sensitivity adjustment (Esens) to the expiratory phase, which greatly reduces the occurrence of human-machine asynchrony and improves the clinical application effect. However, clinicians still have many difficulties in identifying and adjusting the waveform, and they cannot observe waveforms. Very easy to identify. In the past 10 years, PAV or PPS mode ventilation has become the focus of contemporary critical illness research [10,11,12]. This mode provides pressure support based on the patient's breathing effort to solve the human-machine disharmony in PSV ventilation. By understanding the patient resistance Changes in compliance, or adjustment of ventilator settings (VA and FA) using target adjustment methods. The ventilator set pressure is too high, the volume is too high, and the apnea ventilation alarm ensures the safety of this mode and reduces ventilator dependence. Significantly shorten the belt conveyor process. Currently there are DI in the world. ea company, PB company, Weikang company have this mode, PB840 has also adopted the automatic setting method to make this mode more convenient to use. This closed-loop model is being recognized by clinicians. (6) Automatic Catheter Compensation (AT ) Automatic catheter compensation is to instantly compensate the resistance pressure generated by the different calibers of artificial airway catheters. The compensation pressure is different for different calibers and different flow rates, and the compensation range is from 0-100%. different. The ventilator can be reflected on the curve and waveform. The setting of ATC is convenient for clinicians to observe and evaluate spontaneous breathing ability, and it is easy to go offline when implementing low assist ventilation.

4 Ventilator adjustment The modern ventilator has changed from a single function with multiple knobs, and adopts a single knob adjustment method, which is convenient for clinical use. Digital adjustment increases the accuracy of parameter setting. At the same time, the clinician requires rich theoretical and practical experience to make the parameter settings more consistent with the patient's condition. The ventilator also specifies the safety range of conventional parameters. If the range is exceeded, it needs to be confirmed, which increases the safety of mechanical ventilation. Due to the enhanced monitoring and display function of the ventilator, the set parameters are clearly displayed, which is conducive to the clinician's assessment of the patient's condition, and can be transmitted through the network to facilitate the management and guidance of mechanical ventilation.

5 Buying Principles of Ventilator Ventilator is a useful tool for respiratory support and a commonly used treatment method for critically ill patients today. Respiratory support is directly related to the rescue level of critically ill patients. The following principles should be followed when purchasing a ventilator: (1) Understand the current status of the development and application of ventilators, and monitoring and ventilation modes determine the grade of the ventilator. (2) According to whether the hospital scale is a comprehensive ICU or a specialized ICU, it is estimated that the type of disease to be treated is an application-oriented unit or a large hospital of medical, teaching, and research. (3) According to the experience of applying ventilator, ICU doctor level, do not buy high-end machine one-sidedly. The development of ventilator is the same as the development of other medical equipment. In summary, ventilator treatment for intubated patients is a complex systematic project, that is, the level of the ventilator is more related to the level of the doctor using the ventilator, the nurse's breathing management and the overall strength of the hospital (each auxiliary department). A one-sided pursuit of high-end machines may not necessarily improve the success rate of respiratory failure rescue.

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