Ventilation mode of the ventilator
The ventilation mode is a prescription for the ventilator. Traditional ventilation modes include forced ventilation (CV), assisted ventilation (AV), forced/assisted ventilation (A/CV), intermittent mandatory ventilation (IMV), synchronized intermittent mandatory ventilation (SIMV), continuous positive airway pressure (CPAP) ), positive end-expiratory pressure (PEEP), deep breathing (SIGH), manual breathing (MV), etc.
1.Pressure support ventilation
When the patient inhales spontaneously through the ventilator, he gets an additional airflow from the on-demand valve set on the ventilator, and receives positive pressure support in the airway. PsV is lower than the peak inspiratory pressure of intermittent positive pressure ventilation (IPPV), which is related to the negative chest pressure produced by spontaneous breathing. Under the same pressure, the tidal volume of PsV is greater than IPPV, which is conducive to reducing the VD/vT ratio and increasing Alveolar ventilation improves ventilation and also helps to reduce the impact on hemodynamics. PSV is a useful partial auxiliary breathing mode for the patient to breathe spontaneously, but PSV requires a certain central sensitivity and respiratory muscle strength, and respiratory mechanics People who are unstable or whose condition may change rapidly in the short term should use PsV with caution. Generally, a combination of SIMV and PSV low-level pressure support is used in clinical practice.
2. Biphasic positive airway pressure
BIPAP is a pressure/time cycle ventilation mode, commonly known as "universal mode". It sets two different levels of CPAP through a software program, namely P1 and P2 and their execution time Tl and T2. The patient can be within the set time , Spontaneous breathing is performed on two different levels of CPAP, and the application of BIPAP mode has a more obvious effect on increasing the oxygenation of the patient than the application of PAP. The experience of clinical application in recent years has shown that: at all stages of the disease, BIPAP mode can be used as a ventilation aid for patients' spontaneous breathing, and the operation is simple and convenient and non-invasive. However, it is generally believed that BIPAP and APRV are only suitable for mild to moderate respiratory failure, because the mechanical assistance they provide is not very high.
3. Airway pressure release ventilation
Allow the patient to breathe spontaneously under the condition of continuous airway pressure with short pressure release. In the high-pressure section of the patient's voluntary inhalation, the ventilator provides a high flow of gas in the breathing loop to maintain an almost constant CPAP level, which keeps the level of CPAP relatively constant. In order to assist breathing, CPAP is temporarily reduced to allow the functional residual capacity (FRC) to decrease instantaneously. At this time, the natural compliance of the lungs can passively discharge gas and remove carbon dioxide. In APRV mode, the physiological dead space is reduced, and the gas is better distributed in the lungs during the extended inspiratory phase. This ventilation mode is suitable for patients with poor gas exchange. Since the gas is expected to be discharged as much as possible during pressurization, the airway Obstructed patients do not work well
4. Proportional assisted ventilation
Proportional assisted ventilation (PAV) is also called proportional pressure support (ees). The ventilator changes the internal airway pressure proportionally according to the patient's inspiratory volume and inspiratory flow. The volume provided by traditional positive pressure ventilation is fixed. The volume and airway pressure provided by PAV increase in proportion to the patient’s instantaneous inhalation effort, making the inhalation effort and ventilation more consistent. Because PAV protects and strengthens the patient's own control mechanism, the peak airway pressure during ventilation is reduced, the possibility of hyperventilation is reduced, mechanical damage is avoided, and the work of breathing is greatly reduced. Because PAV requires the patient to breathe independently, it inhibits the central nervous system and abnormalities. Patients with breathing patterns (breathing too fast or too slow) do not work well.
5. Inverse ventilation
IRV is a ventilation method in which the inspiration-to-expiration ratio (I:E) is greater than 1:1 by gradually extending the inhalation time. IRV provides a longer-time positive pressure during inhalation to further expand the collapsed alveoli. This positive pressure simultaneously inflates the alveoli slowly, thereby improving ventilation. A shorter expiration time inevitably produces PEEPI. In order to prevent alveolar collapse and improve alveolar stability, IRV is mainly used for acute respiratory failure that is ineffective to PEEP treatment, such as severe ARDS. Because IRV imposes an unnatural breathing pattern on the patient, it causes discomfort to the patient, and more sedation is required. Drugs or muscle relaxants, avoid the patient's confrontation with the ventilator, and be cautious in patients with severe airway obstructive pulmonary disease and cardiac insufficiency
6. Volume guarantee pressure support ventilation
VAPS is a mechanical breathing mode that can not only provide pressure support ventilation that is synchronized with the patient, but also provide volume support ventilation with a capacity guarantee function. This mode maintains the lowest level of tidal volume while providing good synchronization assistance. Function, the flow rate provided by the ventilator is consistent with the flow rate required by the patient, thereby reducing the load on the respiratory muscles, reducing the work of breathing and avoiding over-ventilation. This mode can be used in combination with multiple ventilation modes
7. Mandatory ventilation every minute
MMV will automatically increase mechanical ventilation only when the patient's spontaneous breathing is not enough and is lower than the preset minimum minute ventilation. Conversely, patients who recover their spontaneous breathing ability will automatically reduce the ventilation level without changing the ventilator parameters. MMV is particularly It is suitable for patients with unstable spontaneous breathing caused by mental disorders, such as encephalitis, overdose of sedatives, general anesthesia, acute brain injury, etc., and MMV should be used cautiously for patients with shallow breathing that cause alveolar insufficiency
8. Pressure adjustment capacity control
PRVC is actually a pressure-controlled ventilation. The ventilator continuously measures the patient’s compliance. Under the patient’s current lung compliance conditions, the selected tidal volume VT is reached with the minimum airway pressure and peak pressure is avoided. In this mode The human-machine coordination is good, and the tidal volume is constant, which can ensure the safety of ventilation for patients with unstable spontaneous breathing.
9. Spontaneous breathing and target volume ventilation (VV+)
Including VC+ and VSVC+, the doctor sets the inspiratory time and target tidal volume. The ventilator first uses deceleration waves and inspiratory plateau pressure to give a regular volume test breath at the beginning. To determine the relative compliance of the lungs, calculate the relevant pressure required to deliver the set tidal volume. When the plateau pressure is reached, the ventilator converts to pressure controlled breathing. If the delivered tidal volume is less or more than the preset value, the following The target pressure of breathing will be adjusted, to correct the difference between the two. The aspiration control of VS is similar to VC+, but VS uses PS to adjust the inspiratory flow instead of PC. If the patient's breathing exceeds the set volume, both VC+ and VS will reduce the ventilator's support to control the tidal volume. The target volume breathing method can be reduced The breathing work of the patient with high ventilation demand increases the comfort of the patient, reduces the risk of insufficient flow, and improves the synchronization between man and machine.
10. Adaptive support ventilation
ASV is that the doctor sets the ventilation volume per minute according to the weight and clinical conditions. The ventilator first provides test ventilation, automatically measures the patient's dynamic compliance (CDYN) and expiratory time constant (RCEXP), and then calculates the "minimum work of breathing" The O-TIS formula. Calculate the ideal frequency (F) and ideal tidal volume (VT), and then use P-SIMV (when not breathing spontaneously) or PSV (when breathing spontaneously) to implement. ASV ventilation simplifies the parameter setting and adjustment during ventilation as much as possible, avoids excessive airway pressure and excessive tidal volume, increases human-machine coordination to reduce mechanical ventilation complications, and can adapt to various patients and different clinical conditions.
