Detail Of The Medical Ventilator

Ventilator-Introduction


"Ventilator"-This term was coined by "Sullivan"! ——Professor Sullivan, the inventor of the world's first sleep ventilator


A ventilator is a device that can replace, control or change a person's normal physiological breathing, increase lung ventilation, improve breathing function, reduce breathing work consumption, and save heart reserve capacity. When infants and young children complicated with acute respiratory failure, after active conservative treatment is ineffective, weakened breathing and heavy and thick sputum, difficult sputum discharge, obstruction of the airway or atelectasis, endotracheal intubation and ventilator should be considered.


The ventilator must have four basic functions, namely, inflation to the lungs, inhalation to exhalation conversion, expulsion of alveolar air, and exhalation to inhalation conversion, which in turn cycle. Therefore, it must have: (1) It can provide the power to transport gas to replace the work of human respiratory muscles; (2) It can produce a certain respiratory rhythm, including respiratory frequency and respiration ratio, to replace the function of the human respiratory central nervous system to control the respiratory rhythm; Appropriate tidal volume (VT) or minute ventilation (MV) to meet the needs of respiratory metabolism; ⑷ The gas supplied is preferably heated and humidified to replace the function of the human nasal cavity, and can supply higher than that contained in the atmosphere The amount of O2 to increase the concentration of inhaled O2 and improve oxygenation. Power source: Compressed gas can be used as power (pneumatic) or motor as power (electric). Breathing frequency and inhalation ratio can also use pneumatic air control, electric electric control, pneumatic electric control and other types, switching between exhalation and inspiratory phase It is often switched to exhalation (constant pressure type) after reaching a predetermined pressure in the breathing circuit when inhaling or reaching a predetermined volume when inhaling, but modern breathing machines have both Kinds of forms.


The ventilator for treatment is often used in patients with more complicated and severe conditions. It requires complete functions and can carry out various breathing modes to meet the needs of changing conditions. The anesthesia ventilator is mainly used for patients undergoing anesthesia surgery. Most patients do not have major cardiopulmonary abnormalities. The required ventilator can basically use IPPV as long as it has variable ventilation, respiratory rate and breathing ratio.


Ventilator-working process


The pressure of the injected patient gas is generated by the internal turbo pump \ r. Engineering process: the atmosphere enters the safety valve through the filter. The opening size of the safety valve and the pump speed are controlled by the CPU. The pressure and capacity of the ventilation are set by the doctor according to the needs of SARS patients. The appropriate amount of gas is adjusted through the check valve Enter the human face mask, and enter the human body, that is, the positive suction pressure; the one-way valve is closed, the suction pressure is reduced, and the positive suction pressure of the patient's lungs automatically flows out, that is, exhaled through the mask.


Working process: Medical oxygen is mixed into the air storage tank through the pressure reducing valve and the air passing through the filter. The flow regulator is controlled by the CPU. The pressure and capacity of the ventilation are set by the doctor according to the needs of SARS patients. The valve enters the human body mask and enters the human body, that is, the positive pressure is sucked. When the patient exhales, the one-way valve is closed, the suction pressure decreases, and the positive pressure of the patient's lungs automatically flows out, that is, exhaled through the mask.


Ventilator-classification:


1. According to the connection method with patients:


Non-invasive ventilator: the ventilator is connected to the patient through a mask


Invasive ventilator: the ventilator is connected to the patient through an endotracheal tube


2. Classification by use (six categories):


First aid ventilator: dedicated to on-site first aid.


Respiratory therapy ventilator: Prolonged ventilation support and respiratory therapy for patients with respiratory insufficiency.


Anesthesia ventilator: dedicated to anesthesia breath management.


Pediatric ventilator: dedicated to ventilatory support and respiratory therapy in children and newborns.


High-frequency ventilator: with the function of ventilation frequency> 60 times / min.


Non-invasive ventilator: complete ventilation support through mask or nasal mask.


3. Classification according to driving mode (three categories):


Pneumatic air-controlled ventilator: The ventilation source and control system are only powered by oxygen. Mostly portable first aid ventilator.


4. Classification by ventilation mode (four categories):


Timed ventilator (time switch): Complete exhalation and inhalation conversion according to preset time.


Constant-volume ventilator (volume switching): Complete the conversion of exhalation and inhalation according to the preset output volume.


Constant pressure ventilator (pressure switching): Complete the conversion of exhalation and inhalation according to the preset airway pressure value.


Fixed flow machine (flow rate switching): Complete the exhalation and inhalation conversion according to the preset gas flow rate value.


5. Classification by pressure and flow generator (four types): Mapleson (1959)


Constant pressure generator: low pressure driven by the ventilation source, constant pressure during the inspiratory period, and the inspiratory airflow changes with the lung pressure.


Non-constant pressure generator: The driving pressure of the ventilation source is low, and regular changes occur during the inspiratory period. The inspiratory airflow is affected by both the driving pressure and the lung pressure.


Constant flow generator: The driving pressure of the ventilation source is high, and the air flow remains unchanged during the inhalation period.


Non-constant flow generator: The driving pressure of the ventilation source is high, and the air flow changes regularly during the inhalation period.


The pressure generator is suitable for patients with normal lung function, and the flow generator is suitable for patients with poor lung compliance.


Ventilator-ventilation


1. Intermittent positive pressure ventilation (IPPV): the most basic way of ventilation. When inhaling, a positive pressure is generated, which pushes the gas into the lungs, and the body's own pressure exhales the gas.


2. Expiratory platform (plateau): also called end-inspiratory positive pressure breathing (EIPPB), at the end of inhalation, before expiration, the exhalation valve continues to close for a period of time, and then open exhalation The time generally does not exceed 5% of the respiratory cycle, which can reduce VD / VT (dead volume / tidal volume).