Use of neonatal ventilator: parameter adjustment, weaning steps

Respiratory failure is a critical and severe disease of newborns and one of the important causes of neonatal death. Mechanical ventilation with a ventilator is an important means of rescuing respiratory failure. It can correct severe hypoxemia and hypercapnia, and buy time and conditions for rescuing the primary disease of respiratory failure and removing the inducement. The ultimate goal is to restore effective spontaneous breathing in the child. Although the structural forms of various ventilators are different, the basic units and principles that make up the ventilator are similar.
Neonatal respiratory support is one of the most critical life support measures in the neonatal intensive care unit (NICU). As an important rescue equipment, neonatal ventilator is widely used in various critical conditions such as premature infants, respiratory distress syndrome, meconium aspiration syndrome, etc. This article will explain in detail the parameter adjustment, use process and weaning steps of the neonatal ventilator to help clinical staff manage neonatal mechanical ventilation more scientifically and safely.

1. The relationship between the child and the ventilator and its parts
Host
It supplies air-oxygen mixed gas to the patient according to the set parameters and selected method, and is equipped with a monitoring system to monitor the pressure, flow and oxygen concentration during ventilation.
Air-oxygen mixer
Generally, compressed oxygen and compressed air are used as the power. After the two are mixed, the inhaled oxygen concentration is accurately controlled by controlling the oxygen flow or air intake.
Humidifier
The gas provided by the host is heated and humidified to humidify the patient's respiratory tract, reduce the viscosity of respiratory secretions, make it difficult to produce sputum plugs or sputum crusts in the airway, and protect the airway mucosa.
External pipeline
Its function is to provide humidified gas to the patient and discharge the patient's exhaled gas through the respiratory valve. The respiratory signal must also be fed back to the host to achieve human-machine synchronization.

2. The role of the ventilator
Improve ventilation function.
Improve ventilation function.
Reduce breathing work.
Keep the airway open.

3. Indications for ventilator use
Severe hypoventilation: pulmonary infection, airway obstruction, central infection, severe cerebral edema or intracranial hemorrhage, respiratory muscle paralysis, etc.
Severe ventilation disorders: respiratory distress syndrome, pulmonary hemorrhage, pulmonary edema, etc.
Nerve muscle paralysis.
After chest and heart surgery.
Repeated apnea.
After cardiopulmonary resuscitation: cardiac and respiratory arrest caused by various reasons, such as asphyxia, ventricular fibrillation, etc., should be mechanically ventilated as soon as possible after resuscitation.

4. Preparation before mechanical ventilation
Check the power supply of the ventilator
The power supply of the ventilator is generally 220 volts, and the power plug adopts a three-hole flat type and is connected to the ground wire, such as a plug strip. Be careful not to connect it to the same line with high-power electrical appliances at the same time to avoid burning the fuse and affecting the operation of the ventilator.

Inspection of the ventilator gas source
Most ventilators use compressed air and oxygen as gas sources, and the air compressor pump is used as the pressure gas source. The working pressure is 0.4MPa, which is equivalent to 4 atmospheres. The oxygen pressure is also adjusted to 0.4MPa. If the pressure of compressed air and oxygen is insufficient, it will affect the pressure in the ventilator pipeline, resulting in a drop in airway pressure and a serious deviation of the oxygen concentration from the preset inhaled oxygen concentration.
Before mechanical ventilation, the air compressor should be plugged in to check whether its pressure is 0.4MPa. For central oxygen supply, it should be noted whether the actual working pressure has dropped after the machine is turned on. If oxygen is supplied by oxygen cylinder, the maximum pressure scale of the pressure reducing valve used is 25MPa, the pressure in the oxygen cylinder is generally 15MPa, and the working pressure released by the pressure reducing handle is 0.4MPa, which can be observed through the pressure gauge on the oxygen cylinder. At the same time, it should also be checked whether the air and oxygen pipelines are well connected to the ventilator and no air leaks are allowed.

Inspection of the ventilator circuit pipeline
The ventilator circuit pipeline is the part that connects the ventilator body to the patient, including the ventilation circuit pipeline from the ventilator to the humidifier and then to the patient, and the ventilation circuit pipeline from the patient to the ventilator. Before mechanical ventilation, check whether the pipeline is twisted, aged, cracked, and whether the interface between the pipeline and the ventilator, humidifier water bottle, etc. is tight and whether there is any leakage.

Inspection of the heating and humidification device
Before mechanical ventilation, check whether the performance of the heating and humidification device is intact, which can ensure good humidification, make the gas temperature close to body temperature, and the relative humidity close to 100%. Generally, the heating and humidification device is adjusted to 33~35℃.

Test of the functional status of the ventilator
After completing the above inspection work, connect the simulated lung to the patient end of the pipeline, turn on the power of the ventilator host, air compressor, and heating and humidification device, adjust the ventilator parameters and alarm limits to the working state, and test the ventilator. If there is no abnormality, it can be connected to the patient.

Confirm that the position of the endotracheal tube is normal
Before connecting the ventilator to the patient, observe the patient's skin color, oxygen saturation, chest lifting, whether the breath sounds are symmetrical, chest X-ray, etc. during positive pressure ventilation with the resuscitation bag to confirm whether the position of the endotracheal tube is normal and whether it is firmly fixed.

5. Setting of basic parameters of the ventilator
The main parameters of the ventilator.
Inspiratory oxygen concentration (FiO2).
Maximum inspiratory pressure (PIP).
Positive end-expiratory pressure (PEEP).
Respiratory rate (RR).
Inspiratory time (Ti) Inspiratory-expiratory ratio (I/E).
Tidal volume (Vt).
Flow rate (FR).
Humidifier and its temperature.

6. Pre-adjustment of ventilator parameters
Maximum inspiratory pressure (PIP)
No respiratory tract lesions, 15-18cmH2O for premature infants with apnea. RDS, atelectasis, meconium aspiration, pneumonia, 20-25cmH2O.

Positive end-expiratory pressure (PEEP)
When there is no respiratory tract disease, 2-3 cmH2O. When there is atelectasis and RDS, 4-6 cmH2O. When there is meconium aspiration and pneumonia, 0-3 cmH2O.

Respiratory rate (RR)
When there is no respiratory tract disease, 20-25 times/min. When there is respiratory tract disease, 30-45 times/min. When there is spontaneous breathing RR < 20 times/min → SIMV → shutdown.

Inspiratory/expiratory time ratio (I/E)
When there is no respiratory tract disease, the inspiratory time is 0.5-0.75s. When there is atelectasis and RDS, I/E is 1:1-1:1.2. When there is meconium aspiration and pneumonia, I/E is 1:1.2-1:1.5.

FiO2
When there is no respiratory tract disease, FiO2≤0.4 (40%), when there is respiratory tract disease, FiO20.4～0.8 (40%～80%). Since FiO2 greater than 60%~70% is prone to oxygen poisoning, the time of FiO280%~100% is generally not more than 6 hours, and the time of 60%~80% is not more than 12~24 hours. In order to ensure timely correction of hypoxia and maximize the prevention of oxygen poisoning, FiO2, SpO2, and SaO2 must be closely monitored.

Tidal volume (VT)
Newborn 6~8ml/kg.

Humidifier and its temperature adjustment
Generally, the temperature of the humidifier is adjusted at 33℃～35℃.

7. Adjustment of ventilator parameters during mechanical ventilation
Adjust various parameters according to blood gas analysis
The general principle of ventilator parameter adjustment is to maintain blood gas in the normal range with the lowest PIP and FiO2 as much as possible under the premise of ensuring effective ventilation and gas exchange functions, so as to reduce the risk of barotrauma and oxygen poisoning. The parameter adjustment range generally adjusts 1~2 parameters that have a great impact on the child each time. The adjustment range of each parameter should not be too large each time. The general increase and decrease range is: FiO2 0.05, PIP, PEEP 1~2cm H2O, RR 5 times/min, Ti 0.1~0.2 seconds, FR 1 liter/min.

8. Various common alarms
Alarm for excessive airway pressure: common in increased airway resistance, such as pneumonia, asthma, pipeline distortion; the high limit alarm range of inspiratory pressure is set too low, etc.
Alarm for excessive airway pressure: common in ventilator pipeline detachment, ventilator pipeline leakage, etc.
Gas supply alarm: when the oxygen or air pressure is lower than the specified range, a gas supply alarm will occur.
Power interruption alarm: Commonly seen in: (1) The power plug falls off or becomes loose. (2) Power outage.

9. Care for neonates during mechanical ventilation
Before using the ventilator, carefully check the power cords, oxygen pipes and their connections.
Add water to the humidifier to the standard scale.
Test the various functions and operation of the ventilator.
Set the basic parameters of the ventilator.
Connect the endotracheal tube to the ventilator.
Observe the rise and fall of the chest, and use a stethoscope to auscultate the left and right chest and the two armpits to confirm the normal position and patency of the endotracheal tube to prevent single-lung ventilation.
Routinely monitor arterial blood gas.
A simple ventilator and sputum suction device are available at the bedside of the child, and they are in good condition.
Keep the airway open and suction sputum in a timely and effective manner. 100% oxygen should be given before and after suctioning. Before each suctioning, 0.5-1 ml of normal saline should be dripped into the trachea. Each suctioning time is less than 10 seconds. For children with a lot of sputum and obvious hypoxia, it is not easy to suck it all at once. Suctioning and giving O2 should be performed alternately.
Warm and humidify the gas delivered. The temperature of the humidifier is adjusted at 33℃~35℃. Normal saline should be dripped directly into the trachea at regular intervals.
Pay attention to the water storage of the humidifier, add distilled water in time, avoid dry blowing, and pour out the condensed water in the water collection arms and the water collected in the pipe.
Strengthen physical therapy, turn over and pat the back regularly to facilitate the discharge of secretions.
Strictly prevent artificial airway displacement and accidental extubation. It is difficult to fix the oral tracheal intubation of newborns, and it is very easy to shift and slip. Especially when suctioning sputum through an artificial airway. Therefore, when suctioning sputum, it is best for two people to cooperate with the operation. When the newborn is agitated, use sedatives according to the doctor's advice, and use restraints when necessary.
Understand the meaning of various alarms to ensure the safety of patients: if the power plug falls off, reconnect it. In case of power outage, quickly go to the patient's bedside to disconnect the machine, use a simple ventilator for artificial oxygen, and monitor closely. For reasons that cannot be found for the time being, immediately use an artificial simple ventilator or replace another ventilator.
Pay attention to whether the patient's spontaneous breathing and mechanical ventilation are coordinated.
When moving a child, pay attention to disconnecting the machine first and then moving to prevent the pipe from twisting or pulling and causing the tracheal tube to fall out.
Observe complications and notify the doctor in time if there are any abnormalities.
Prevent secondary infection: keep the indoor air fresh, ventilate regularly, and disinfect the ward once a day. For children sleeping in an incubator, follow the routine care of the incubator. When suctioning sputum, strictly follow aseptic operation to prevent cross infection. Strengthen the care of the skin, eyes, and mouth. The ventilator pipe is replaced and disinfected once a week.
Closely observe the condition, pay attention to changes in breathing, heart rate, body temperature and urine volume. Observe changes in ventilator parameters and the child's response to mechanical ventilation, and keep records. After using the ventilator, the child is quiet, breathing is stable, hypoxia symptoms are reduced or disappeared, and the coma is conscious, which proves that the ventilation is appropriate. On the contrary, there is insufficient ventilation, air leakage in the tube or sputum blockage, and the cause should be found and dealt with in time. Special care. Strictly hand over the bedside, explain the vital signs, the size of the tracheal tube, the depth of insertion into the trachea, and the various parameters of the ventilator and record them.

10. Complications of mechanical ventilation in neonates
Air leakage: pulmonary interstitial emphysema, pneumothorax, mediastinal emphysema, subcutaneous emphysema.
Bronchopulmonary dysplasia.
Immature retinopathy or retrolental fibroplasia (ROP).
Secondary infection.
Intracranial hemorrhage (more common in premature infants).

11. Withdrawal from mechanical ventilation in neonates
Indications for withdrawal
Improvement of the primary disease and improvement of the condition.
Spontaneous breathing is stable, coughing and expectoration are strong, can tolerate suction, and blood pressure and heart rate are stable. FiO2≤0.4, PIP≤15~16cmH2OPEEP<5cmH2ORR<10 times/min, normal blood gas, acid-base imbalance and water and electrolyte disorders are corrected.
X-rays show that the primary lung disease has been significantly absorbed and improved, and the age of RDS children is >3 days.
Steps of weaning
Monitor heart rate and respiration during weaning. If there is any abnormality, restore the original parameters immediately.
According to the blood gas results, gradually reduce the ventilator parameters.
R20 times/min→SIMV, T should be 0.5~0.655, and the child's spontaneous breathing appears during the intermittent period of ventilator ventilation.
After SIMV is maintained for a period of time, if RR<6 times/min and spontaneous breathing is strong, the machine can be directly weaned or CPAP can be used instead.
During CPAP, FiO2≤0.4, pressure≤3cmH20→extubation. 0.5~1h before extubation, intravenous injection of dexamethasone 0.5mg/kg is given to prevent laryngeal edema.
Before extubation, clean the oral, nasopharyngeal secretions, and then clean the tracheal secretions according to the routine suction operation. The secretions in the catheter are sent for bacterial culture.
After extubation, oxygen is inhaled through the hood and respiratory changes are closely observed.
After extubation, nebulize once every 2 hours, and use it 2 to 3 times as appropriate.
Strengthen lung physical therapy and take chest X-rays to check for lung complications.

12. Disinfection of ventilator
Regularly clean and disinfect the airway pipeline and soak it for disinfection.
Use high temperature and high pressure to disinfect the silicone airway pipeline.
Use ethylene oxide gas fumigation for disinfection.

The use of neonatal ventilators requires close monitoring, precise parameter setting and scientific weaning process. Every NICU medical staff should master this technology to ensure the safety of children, reduce complications and improve survival rate. In the future, with the improvement of the intelligence of ventilators, automatic parameter adjustment and remote monitoring technology will provide more protection for neonatal life support.