1 Principle and performance of the humidifier
The humidification of the patient's inhalation gas can usually be used cold water humidification, heating humidification, ultrasonic atomization humidification and heat and humidity exchange humidification and other ways. Oxygen inhalation often use cold water humidification, respiratory use heating humidification, and the other two are less commonly used. Completion of the humidification function of the device called humidifier, according to the realization of the different ways of humidification, but also accordingly divided into: cold water humidifier, heating humidifier, ultrasonic atomization humidifier and heat and moisture exchange humidifier (artificial nose) and so on several types.
1.1 Heating humidifier Heating humidifier structure has two types: Class A is the heating device and humidification tank into one, Class B is separate. Class A heating part of the water container in the water directly placed in the heating plate or heating rod heating, Class B is the use of heating plate heating, heating plate can be placed in accordance with the actual needs of adults or infants and young children special humidification canisters. Class A humidifier through the Class A humidifier through the gas flow to be submerged underwater, and then come out, take away the water vapor and heat, the advantage is simple to use, low failure rate, the disadvantage is that the tank's compliance with the changes in the liquid level and change, cleaning and disinfection is not convenient; and class B humidifier is placed vertically in the humidification tank by a multi-turn curled aluminum cylinder and the inner wall affixed with a layer of water-absorbent paper (can be replaced on a regular basis), the canister with up to 1/3 water, so that in gas This creates a warm and humid corridor between the inlet and outlet of the gas, which carries away water vapor and heat as the gas passes through and does not create a trans-water pressure. In addition to the tank can be replaced as needed, can also be made into a disposable consumables, such as the following side of the heating part of the failure, replacement, maintenance is very convenient.
Some high-grade humidifier is also placed in the exit and the patient mouth side of a temperature sensor, in the suction circuit to place a 1-meter-long heating wire, through the two heating elements of double-servo heating, to solve the low ambient temperature when the single-servo type of easy to knot the water in the pipeline, and can be adjusted by the relative degree of the two heating elements heated to change the relative humidity, but do not set the heating wire temperature too high, in order to avoid the heating part failure, replacement, maintenance is very convenient. But do not set the temperature of the heating wire too high, so as not to reduce the relative humidity too much, such as do not need to heat the wire heating, you can turn off to make it a single servo type.
Usually, the temperature of the gas reaching the patient's mouth should be set between 32℃ and 36℃, the relative humidity should be kept above 95%, and the absolute humidity should be ≥30mg L-1, i.e., the patient's inhalation of each liter of gas should contain more than 30mg of water vapor. It is generally believed that if the outlet temperature of the humidification tank is lower than 31 ℃, the ability of the gas to carry water vapor does not meet the ISO8185 and ANSI Z79.9 suggested that the absolute humidity of the inhaled gas should be ≥ 30mg L-1 requirements, the MR700 series of humidifier such as the tank outlet temperature is set to be lower than 31 ℃ can be automatically alarmed. Therefore, the choice of humidifier should be considered whether its performance can meet the clinical requirements, through the detection of its flow rate and temperature and humidity performance curve can be judged (Figure 1).
Figure 1:
Curve 1: the patient's mouth temperature is set to 37 ℃, the canister outlet 39 ℃, the air circuit heating to maintain a low 2 ℃; curve 2: the patient's mouth temperature is set to 37 ℃, the canister outlet 36 ℃, the air circuit heating to maintain a high 1 ℃; curve 3: the patient's mouth temperature is set to 34 ℃, the canister outlet 36 ℃, the air circuit heating to maintain a low 2 ℃. 1.2 Thermo-hygrostatic exchanger Thermo-hygrostatic exchanger, also called artificial nose, is a disposable consumable, which is made by imitating camel's nose, and there is a chemical adsorbent inside, which can retain water and heat when exhaling, and make the inhaled gas wet and warm when inhaling. The heat and humidity exchanger concentrates the advantages of the above kinds of humidifier, can keep the body temperature, compliance is small, the use is very convenient, simple, and for the disposable consumables, there is no danger of breeding bacteria and cleaning and disinfecting trouble; but there is a certain degree of exhalation resistance, and need to be replaced once in 24h, emergency, anesthesia and ICU short-term ventilation of the use of the patient is more desirable, the use of hepatitis B or tuberculosis, etc., the use of the positive patients can also alleviate the disinfection of the workload and the air pollution of the ward environment. The use of hepatitis B or tuberculosis positive patients can also reduce the workload of sterilization and air pollution of the ward environment.
2 performance testing and management of the use of humidifier
In 1997, the Shanghai Medical Devices Factory drafted the national standard of respirator with reference to ISO10651-1 on the basis of the original GB11747-89 and ZBC46008-89. In the standard, the performance of the humidifier stipulates that the airflow rate of the adult canister is 30L min-1, the airflow rate of the infant canister is 10L min-1, and the pressure drop is not more than 300Pa; while the temperature range of the gas at the outlet end of the canister and the humidification effect should be achieved are not stipulated, and no requirements are put forward for the safety monitoring of the temperature of the gas at the patient's mouth. In order to improve the success rate of mechanical ventilation rescue, the performance of the humidifier should be put forward higher requirements, on par with international standards, to strengthen the quality management in the process of purchase and use, and regular testing, repair and maintenance.
2.1 Maintenance and care of the humidifier Even if a good performance of the humidifier, if the use of the process does not pay attention to the maintenance, maintenance, but also will not achieve a better clinical results. A class of heated humidifier due to the compliance of the large, inconvenient disinfection will gradually be replaced by the B class.
The use of class B (split) humidifier maintenance and maintenance methods: ① humidification tank part of each patient before use should be cleaned, disinfection, disinfection, disinfection between the joints to be disassembled, and at the same time to replace a filter paper, long-term use of the patient can be replaced once a month, to ensure that the effect of humidification, such as long-term non-replacement, or forget to load the filter paper, humidification will be a low-temperature alarm, does not work, at this time need to replace the filter paper, and need to turn off the power supply after the replacement. filter paper, and the need to turn off the power and then restart; ② disinfection can be high temperature, high pressure (136 ℃, 1.2 atmospheric pressure, 5min), or 750mL L-1 ethanol scrubbing soak for 30min, but prohibit the use of acid, organic solvents and other corrosive disinfection methods; ③ often pay attention to the observation of the tank height of the liquid level, such as the liquid level is too low, the inlet side of the distilled water from the filling to the scale, but do not spill the water to the shell below. Spread the water to the following shell or heating plate, in order to avoid damage to the machine or corrosion of the heating plate; ④ temperature sensor probe should be inserted firmly in the patient's pipeline matching connector, connected to the suction end of the Y-head (do not connect to the inhalation and exhalation of the public **** end, to prevent the patient's exhalation of gas to interfere with the monitoring), and rotate to match the connector to make the temperature probe as far as possible in the pipeline above the head down, in order to prevent the collection of moisture affects the measurement of temperature, and remember to probe can only be scrubbed with ethanol, not by other means of disinfection. Scrub the probe with ethanol only, do not use other methods of disinfection; ⑤ dual-servo type humidifier tube heating line temperature should not be set too high, such as do not need to be turned off or do not install the heating line; ⑥ when there is a high temperature of the airway or low-temperature alarm, you only need to replace the following control part of the maintenance, such as no replacement, but also can not be immediately repaired, the upper tank can play a role in the role of the cold water humidification; ⑦ humidifier heating is out of control, you can switch on and off through the intermittent way to maintain humidification (restricted to only the wetter) The way to maintain the humidification (limited to inspiratory temperature monitoring of the humidifier, and the monitoring function is normal), in order to wait for maintenance or replacement; ⑧ humidifier import and export have obvious markings, do not connect the reverse, rely on the airflow across the water humidification, such as connecting the reverse, will be the water pressure to the patient's circuit, such as the MR series does not cross the water, connecting the reverse of the effect of humidification will be greatly reduced; ⑨ with the airway temperature monitoring of humidification such as respiratory in the stand-by mode, short time (about 20 minutes), the time to the patient's circuit, the airway temperature monitoring, and the humidification effect of the airway temperature monitoring. Machine state, a short period of time (about 20min) can press the "Standby" button 1s to make it standby, a long time to turn off the humidifier.