Why buy a nebulizer?

🥼 Practice and Clinical
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Today at the pediatric outpatient clinic, I found that when children undergo nebulization, a machine is required to be used. The mask is connected to a tube, which is then connected to the machine that provides the gas. However, in the ward (non-respiratory department), I saw patients undergoing nebulization with the tube directly connected to the oxygen outlet on the wall to provide gas. The principle is that the high-speed gas flow creates a negative pressure that draws the liquid in the nebulizer, breaking up the drug particles to achieve nebulization.[1]

Since both methods provide gas, there should be little difference between using oxygen and using air. So why buy a special nebulizer machine? The outpatient clinic also has oxygen outlets on the wall.

After discussing with Instructor Li Xinyi and consulting relevant materials, I learned that there are actually three types of nebulizer machines (details below). The one used by the child today should be a jet nebulizer, which uses a compressor to provide gas. Such a nebulizer can indeed be replaced by an oxygen outlet. If nebulization is only done in the outpatient clinic, it seems unnecessary to buy a nebulizer machine. But if nebulization is done long-term at home where there is no oxygen outlet, a compressor is needed.

The jet nebulizer compressor has a drawback: the particles of the nebulized liquid are relatively large, and the noise is also relatively high. The ultrasonic nebulizer can nebulize the liquid into very fine particles, thus better depositing in the lower respiratory tract (such as the bronchioles and alveoli). The mesh nebulizer’s advantage is its quiet operation.

Excerpts from related literature introducing the three types of machines

Consensus of Experts on the Application of Nebulized Inhalation Therapy in Respiratory Diseases[2]

  • The commonly used nebulizers in clinical practice are mainly three kinds: jet nebulizers, ultrasonic nebulizers, and vibrating mesh nebulizers.
    1. Jet nebulizer: Also called a jet stream nebulizer or compressed gas nebulizer. It consists mainly of a compressed gas source and a nebulizer. The compressed gas source can be bottled compressed gas (such as high-pressure oxygen or compressed air) or an electric compressor. The nebulizer uses the Venturi jet principle, where compressed gas moves at high speed through a narrow opening and suddenly depressurizes, creating negative pressure locally. This negative pressure siphons liquid from the container through a small tube near the gas outlet. When encountering the high-pressure gas flow, the liquid is collided and broken into small aerosol particles. Especially when the high-pressure gas flow strikes a baffle, the liquid is shattered to form countless drug aerosol particles. Larger drug aerosol particles fall back into the drug reservoir via the baffle, while smaller drug aerosol particles are outputted with the airflow. The nasal-sinus nebulizer is a jet nebulizer with oscillating waves. On the basis of compressor design, a pulse pressure aggregation device is added; the pulse wave acts directly on the drug aerosol, giving drug particles an oscillation characteristic that easily penetrates sinus openings and deposits well inside the sinuses.
    1. Ultrasonic nebulizer: Its principle is that a crystal transducer at the bottom of the nebulizer converts electrical energy into ultrasonic energy, creating vibrations transmitted through a sound-permeable membrane at the bottom of the nebulization cup. This vibration agitates the liquid inside, destroying its surface tension and inertia, thus forming countless fine aerosol particles for release.
    1. Vibrating mesh nebulizer: Combines features of ultrasonic nebulization. It employs an ultrasonic vibrating membrane that vibrates strongly and uses extrusion technology to force the liquid through micro-sized fixed-diameter mesh holes, forming countless fine particles for release.

Expert consensus on glucocorticoid nebulized inhalation therapy in pediatrics (2018 revised edition)[3]

  • Jet nebulization: Jet nebulizers driven by a compressor pump or oxygen are currently the most commonly used nebulizers in clinical practice. Their principle is that high-speed compressed gas passes through a narrow opening and suddenly depressurizes, generating localized negative pressure that sucks out the drug liquid and forms drug aerosol particles in the high-speed airflow. Larger particles fall back into the medicine reservoir via the baffle, while smaller particles are carried out with the airflow[4]. The size of aerosol particles relates to the pressure and flow rate of the airflow; increasing flow rate increases nebulization output, reduces particle size, and shortens nebulization time, improving patient compliance. When using jet nebulizers, the liquid volume should be sufficient, generally 3-4 mL, which can be output completely within 5-10 minutes. For children in acute asthma attacks with difficulty breathing, oxygen is recommended as the driving gas to provide oxygen simultaneously during nebulization. The oxygen flow rate for oxygen-driven nebulization is 6-8 L/min.
  • Mesh nebulization: Nebulization occurs by vibrating the liquid through mesh holes. Compared with jet nebulization, mesh nebulization outputs a slightly lower proportion of inhalable microparticles but has advantages of small device size, light weight, easy portability, low noise during use, and the ability to be used in inclined positions. Currently, the available mesh nebulizers are limited, mainly passive devices domestically, which cannot connect to extended inhalation tubes. When using suspensions, the mesh easily clogs, and durability of the mesh is relatively low, which is the greatest drawback.
  • Ultrasonic nebulization: Uses piezoelectric sheets to generate 1-2 MHz high-frequency ultrasound, forming aerosol particles on the top layer of the liquid in the medicine reservoir. However, for suspensions, aerosol particles cannot fully reach the liquid surface that forms aerosols. Ultrasonic nebulization aerosols have a high water particle density and fewer effective drug particles and may increase airway resistance. The high frequency can also convert into heat energy, potentially affecting the activity of glucocorticoid drugs. When using ultrasonic nebulizers, the drug volume is large, and the output efficiency of aerosol particles is low; most drugs ultimately remain in the residual liquid, making it unsuitable for treating asthma and other wheezing diseases.
  • Because the output efficiency of microparticles varies greatly among nebulizers and directly affects therapeutic efficacy, it is recommended to avoid nebulizers that cannot provide definite aerodynamic data and clinical efficacy evidence.

References

  1. [What is the principle of medical nebulizers? Are you using it correctly? - Bilibili] https://b23.tv/DHLSoxZ ↩︎

  2. Expert Group for the Consensus on the Application of Nebulized Inhalation Therapy in Respiratory Diseases by the Respiratory Disease Branch of the Chinese Medical Association. Consensus on the Application of Nebulized Inhalation Therapy in Respiratory Diseases [J]. Chinese Medical Journal, 2016, 96(34): 2696-2708. DOI:10.3760/cma.j.issn.0376-2491.2016.34.003 ↩︎

  3. 申昆玲,邓力,李云珠,李昌崇,向莉,刘恩梅,刘瀚旻,刘传合,陈强,陈育智,陈志敏,陈爱欢,何庆南,张建华,尚云晓,俞善昌,洪建国,郝创利,赵德育,钟礼立,殷勇,崔永耀,盛锦云,鲍一笑. Expert Consensus on the Application of Glucocorticoid Nebulized Inhalation Therapy in Pediatrics (2018 Revised Edition) [J]. Journal of Clinical Pediatrics, 2018, 36(2): 95-107. DOI:10.3969/j.issn.1000-3606.2018.02.004. ↩︎