During long-term pressurized use, the strength of pressure infusion bags, a medical device used in operating rooms, is affected by a combination of material properties, the pressure mechanism, and environmental factors. This can manifest as gradual changes in physical properties and potential failure risks.
The core function of a pressure infusion bag is to accelerate fluid delivery through external pressure. Therefore, the bag material must possess sufficient flexibility, fatigue resistance, and sealing properties. Under long-term pressurization, the material's molecular chains may undergo creep under sustained stress—irreversible plastic deformation over time under constant stress. This deformation can cause localized thinning or swelling of the bag, particularly at stress-concentrated areas such as seal edges and creases, thereby reducing the material's tensile strength and puncture resistance. For example, while medical-grade PVC material exhibits good flexibility, under prolonged high-pressure conditions, plasticizers may migrate to the material's surface, causing the bag to become hard and brittle, increasing the risk of rupture.
The impact of the pressure mechanism on bag strength is reflected in the difference between dynamic and static pressure. In the operating room, pressure infusion bags may experience intermittent pressurization (e.g., adjusting pressure based on patient needs) or continuous high pressure (e.g., during rapid blood transfusions). Dynamic pressure fluctuations can accelerate material fatigue and trigger the initiation and propagation of microcracks. For example, during repeated inflation and deflation, the bag material experiences stress fatigue due to the expansion and contraction cycles. Cracks may initiate at material defects or processing marks, gradually propagating to a critical size, ultimately leading to bag rupture. While static high pressure reduces cyclic stress, the continuous high stress state accelerates material aging. Especially when the pressure approaches or exceeds the material's design limit, the bag's strength will decrease nonlinearly.
The synergistic effect of environmental factors and pressure further exacerbates bag strength degradation. Operating room environments are often subject to temperature fluctuations, light exposure, and disinfectant exposure. High temperatures accelerate material oxidative degradation, weakening the bonding between molecular chains; ultraviolet radiation can trigger photooxidative reactions on the material surface, leading to embrittlement; and chlorine-containing disinfectants can corrode the material surface, compromising its seal. When these environmental factors are combined with long-term pressurization, the rate of bag strength degradation can be significantly accelerated. For example, if the material is used under high pressure immediately after high-temperature sterilization, changes in crystallinity caused by the thermal history may increase the susceptibility to cracking.
Long-term pressurization can also affect the bag's sealing performance. The seal of a pressure infusion bag is a critical area of stress concentration. Prolonged pressure can cause the heat seal to delaminate or the adhesive to fail, leading to leakage. Furthermore, the connection between the bag and the infusion tubing may become loose or worn due to repeated insertion and removal or pressure shock, further threatening safe use.
To mitigate the adverse effects of long-term pressurization on bag strength, comprehensive intervention is necessary, including material selection, design optimization, and usage specifications. Selecting materials with improved fatigue resistance (such as multi-layer co-extruded film) can slow creep and crack propagation; optimizing the bag structure (such as adding ribs and rounded corners) can disperse stress concentrations; and strictly controlling the pressure range and operating time to avoid overpressure or prolonged continuous pressurization is key to ensuring bag integrity. Furthermore, regular inspection of the bag's appearance (for deformation and leakage) and pressure testing can promptly identify potential failure risks and ensure safe use in the operating room.
