The airflow dynamics design of the nebulizer mask plays a key role in the drug deposition efficiency. Its core lies in optimizing the gas flow path and characteristics so that the drug particles can reach the target area more accurately and efficiently. The cavity shape of the mask is the basic factor affecting the airflow distribution. If the internal space of the mask is too wide, a low-speed vortex area is easily formed at the top, and larger drug particles will be retained in it due to gravity sedimentation, and small particles may also be lost with the exhaled airflow; while the fitted mask can effectively guide the airflow to the central nozzle area by reducing the gap between the face and the cavity, so that the proportion of drug particles moving in a straight line is greatly increased, thereby significantly increasing the amount of drug deposition in the respiratory tract.
The synergistic effect of the nozzle angle and the airflow velocity should not be ignored. The drug particles ejected from the vertical nozzle are easy to hit the oral mucosa, while the nozzle tilted at a certain angle (usually 30°-45°) can guide the particles to slide along the back of the tongue into the throat, increasing the probability of entering the lower respiratory tract. At the same time, the airflow velocity at the nozzle needs to be precisely controlled. If the speed is too fast, the probability of large particles hitting the upper respiratory tract wall due to inertia increases; if the speed is too slow, small particles are prone to diffusion and deposition due to Brownian motion. Only by finding the right combination of speed and angle can the drug particles arrive and deposit in the target respiratory tract smoothly.
The influence of the exhalation valve structure on the drug deposition efficiency is also very important. The traditional spring-type exhalation valve has an opening delay at the beginning of exhalation, which will cause some inhaled drugs to be lost with the initial exhalation flow; the new film-type exhalation valve uses pressure-sensitive materials, which can be opened quickly, reduce drug waste, and improve drug retention rate. In addition, the aperture size and position of the exhalation valve also need to be carefully designed. If the aperture is too small, it will increase the patient's exhalation resistance, and if it is too large, it will be difficult to maintain the drug concentration in the mask. The appropriate exhalation valve design can effectively improve the effective utilization rate of the drug.
The sealing of the mask edge and the face is directly related to the drug deposition efficiency. If the mask edge is not tightly fitted to the face and the leakage rate is too high, the mixing of external air will not only reduce the drug concentration in the mask, but also change the direction of the airflow, causing the particle deposition position to shift. The soft silicone edge with appropriate elastic modulus, and the adjustable nose clip and chin support can ensure comfort while keeping the leakage rate at a low level to ensure that the drug can fully play its role.
Computational fluid dynamics (CFD) technology provides a powerful optimization tool for the airflow dynamics design of the nebulizer mask. By establishing a three-dimensional mask model and the geometric structure of the human respiratory tract, simulating the airflow velocity field, particle trajectory and deposition distribution under different design parameters, designers can intuitively observe the movement of drug particles, discover design defects in time and make adjustments. For example, by changing the curvature of the top of the mask and adding guide grooves, the vortex intensity can be effectively reduced, the lung deposition rate can be significantly improved, and the simulation results will eventually be verified by experiments to ensure the effectiveness of the design.
With the help of 3D printing technology, a highly fitted mask can be customized according to the patient's facial features, which can greatly reduce the airflow leakage rate. At the same time, the smart mask with integrated micro-sensors and feedback systems can automatically adjust the nozzle angle and airflow velocity according to the patient's real-time breathing frequency, realize dynamic optimization of drug deposition efficiency, promote atomization treatment to a new stage of precision, and bring patients a more efficient treatment experience.
