结论：交替压力的效果取决于压力值、周期、和系统的可靠性

交替压力气垫床通过气泵周期性地给不同气囊充放气，使身体的受压部位不断变化。原理是：组织缺血需要持续一定时间才会造成损伤，如果受压部位周期性改变，每个部位的持续受压时间就被缩短。

所以性能取决于三件事：压力值是否合适、交替周期是否合理、以及系统能否长期可靠运行。 三者缺一不可——压力对但周期太长，效果打折；两者都对但气泵故障，防护就中断了。

验证的维度

维度 验证内容
气囊压力 充气与放气状态的压力值
交替周期 一个完整循环的时间
压力转换 充放气的过渡过程
界面压力 人体与垫面之间的实际压力
载荷适应 不同体重下的压力调节
泄漏 气囊与管路的密封性
气泵可靠性 长期运行的稳定性
断电行为 停电时的表现
报警 异常情况的提示

注意「气囊压力」和「界面压力」是两回事。 气囊内的气压是系统参数，而人体与垫面之间的界面压力才是与组织相关的量。两者有关系但不相等，因为还受体重、体位、垫面材料影响。

验证应当以界面压力为主，气囊压力作为系统参数一并记录。

界面压力的测量

测量方式。 与坐垫压力测量类似，用压力分布阵列铺在人体（或模型）与垫面之间。

动态记录。 交替压力垫的压力是随时间变化的，必须做连续记录而不是单点测量。

关键部位。 骶尾部、足跟、肩胛、枕部这些好发部位要覆盖。

周期内的变化。 记录一个完整周期内各部位的压力变化曲线。

峰值与持续时间。 不只看峰值，还要看高压持续多久。

「高压持续时间」是这类产品评价的关键指标。 峰值压力高但持续时间短，与峰值压力中等但持续时间长，对组织的影响不同。交替压力垫的价值正在于缩短持续时间。

交替周期的考察

周期长度。 一个完整循环的时间。周期设定要有依据。

周期的准确性与稳定性。 实际周期与设定值的偏差，以及长期运行中的漂移。

各气囊的相位关系。 相邻气囊的充放气时序，决定了受压部位的转移方式。

过渡过程。 从充气到放气的过渡是否平滑，过渡期间的压力分布。

可调性。 周期是否可调，调节范围是多少。

建议记录完整的周期曲线，而不只是给一个周期时间。曲线能反映过渡过程、各气囊的配合关系，这些都影响实际效果。

载荷适应

不同使用者体重差别很大，系统应当能适应：

压力调节。 按体重调节气压，避免轻体重者「悬空」（压力过高，身体被顶起）或重体重者「触底」（压力不足，身体沉到底部接触床板）。

触底的检测。 触底时局部压力会很高，防护失效。应当能检测或者通过设定避免。

自动调节功能。 部分产品有自动调节，其准确性要验证。

调节范围。 适用的体重范围要明确。

「触底」是这类产品的关键失效模式，因为它是静默的——系统仍在运行，指示正常，但使用者的骶尾部已经压在床板上。验证时应当包含体重上限的情形，确认不会触底。

失效模式

气泵故障。 停止工作则防护完全中断。

泄漏。 气囊破损或管路漏气，导致压力不足。

堵塞。 管路折弯或堵塞，某些气囊不工作。

控制故障。 周期异常或者停在某个状态。

断电。 停电后的行为。

触底。 前面说过。

这些失效有一个共同点：使用者往往感觉不到。 需要防护的使用者本身感觉或表达能力受限，而失效的表现（压力不足）不像机械故障那样明显。所以报警功能是必需的，不是可选的。

报警与安全功能

低压报警。 压力低于设定值时报警。

气泵故障报警。 泵停止或异常时报警。

断电报警。 停电时报警，并保持一定的支撑（部分产品有单向阀，断电后气囊保持一段时间的压力）。

报警的可感知性。 声光报警的强度要足够，在病房或家庭环境中能被注意到。

静音功能的限制。 静音后应当有时限，不应永久静音。

心肺复苏快速放气。 急救时需要快速放平，应当有快速放气装置且操作简便。

「快速放气」是急救相关的功能，位置要明显、操作要简单、放气要快。验证时应当实测放气时间。

其他考察项

噪音。 气泵运行噪音影响使用者睡眠。长期使用的产品这一项有实际意义。

微气候。 垫面的透气性影响接触面温湿度。

清洁消毒。 垫套的耐受性、气囊的清洁。

耐久。 长期运行后的性能保持，包括气囊材料的老化和气泵的寿命。

防火。 与床上用品相关的阻燃要求。

与静态减压垫的比较

气垫床分交替压力和静态（恒压）两类，特点不同：

交替压力。 主动改变受压部位，适合风险较高的使用者。但有噪音、依赖电源、结构复杂。

静态减压。 通过材料和结构分散压力，无运动部件。可靠性高，但不能主动改变受压部位。

混合型。 部分产品兼有两种模式。

选择依据是使用者的风险等级和活动能力。 能自主翻身的使用者，静态减压可能已经足够；完全不能自主活动的使用者，交替压力的价值更大。

产品资料中应当说明适用的风险等级，帮助采购和临床做出合适的选择。

使用中的常见问题

参数设置不当。 体重设定错误导致压力不合适。

床单过紧。 绷紧的床单限制气囊膨胀，削弱交替效果。这个问题很常见但容易被忽略。

加太多垫层。 在气垫上再铺多层垫子，交替压力传不到使用者身上。

管路折弯。 影响气流。

长期不检查。 泄漏或故障未被发现。

「床单过紧」和「加太多垫层」这两点应当在说明书中明确提示，因为它们完全抵消了产品的作用，而照护人员往往不知道。

我们的做法

做气垫床验证时，我们会做完整周期的界面压力连续记录，并重点分析高压的持续时间而不只是峰值。 这一项才对应交替压力垫的核心价值。

另外，体重上限下的触底检测是我们建议的项目——这是静默失效的场景，使用者和照护人员都不易察觉，必须通过测试确认。

如果你有气垫床或类似的动态减压产品需要验证，想先理清测试方案，可以把产品参数和适用范围发过来一起讨论，或者直接联系：132 4819 8029。检测能力见服务介绍，产品分类见手动轮椅检测与电动轮椅检测，标准信息见标准查询。

English version

Conclusion. Alternating pressure mattresses use a pump to inflate and deflate different cells cyclically so that the body's loaded areas change continuously. The principle is that tissue ischaemia must persist for some time before damage occurs, so periodically changing the loaded area shortens the duration for which any one area is loaded. Performance therefore depends on three things: whether the pressures are appropriate, whether the cycle time is sensible, and whether the system runs reliably over time. All three are needed: correct pressures with too long a cycle reduce the effect, and correct pressures and cycle with a failed pump mean no protection at all.

Dimensions of verification. Cell pressure covers inflated and deflated values. Cycle time covers one complete cycle. Pressure transition covers the inflation and deflation process. Interface pressure covers the actual pressure between body and surface. Load adaptation covers pressure adjustment for different body weights. Leakage covers the integrity of cells and tubing. Pump reliability covers stability in prolonged operation. Power failure behaviour covers what happens during an outage. And alarms cover indication of abnormal conditions. Note that cell pressure and interface pressure are different things: cell pressure is a system parameter, while interface pressure between body and surface is the quantity relevant to tissue. They are related but not equal, since body weight, posture and surface materials also intervene. Verification should lead with interface pressure, recording cell pressure as a system parameter alongside.

Measuring interface pressure. The method resembles cushion pressure mapping, with a sensor array between body, or model, and surface. Recording must be continuous, since pressure varies with time and single-point measurement will not do. Coverage must include the vulnerable sites of sacrum, heels, scapulae and occiput. The variation across a complete cycle should be recorded as a curve for each region. And both peak pressure and its duration should be examined. Duration of high pressure is the key measure for these products: a high peak lasting briefly affects tissue differently from a moderate peak lasting long, and shortening duration is precisely what alternating pressure offers.

Examining cycle time. Record the length of one complete cycle, with a basis for the setting. Measure accuracy and stability, meaning deviation from the set value and drift over prolonged operation. Examine the phase relationship between cells, since the sequence of inflation and deflation determines how loading transfers. Examine the transition, whether smooth and what the pressure distribution is during it. And examine adjustability, whether the cycle can be varied and over what range. Record complete cycle curves rather than a single cycle time: the curve shows the transition and the interaction between cells, both of which affect real performance.

Load adaptation. Users vary widely in weight and the system must adapt. Pressure adjustment by weight prevents a light user being perched on an overpressurised surface and a heavy user bottoming out through insufficient pressure and contacting the base. Bottoming out should be detectable, since local pressure becomes very high and protection fails, or avoided by setting. Automatic adjustment, where fitted, must be verified for accuracy. And the applicable weight range must be stated. Bottoming out is the critical failure mode for these products because it is silent: the system still runs, indications appear normal, and the user's sacrum is nonetheless resting on the base. Include the upper weight limit in verification and confirm that bottoming out does not occur.

Failure modes. Pump failure interrupts protection entirely. Leakage from damaged cells or tubing reduces pressure. Blockage from kinked or obstructed tubing leaves some cells inactive. Control failure produces abnormal cycling or leaves the system stuck in one state. Power failure raises the question of subsequent behaviour. And bottoming out, as above. These share one feature: the user generally cannot detect them. The users needing this protection have limited sensation or communication, and the manifestation, insufficient pressure, is not obvious in the way a mechanical fault would be. Alarms are therefore necessary rather than optional.

Alarms and safety functions. Low pressure alarms indicate pressure below the set value. Pump failure alarms indicate a stopped or abnormal pump. Power failure alarms indicate an outage and should be accompanied by retained support, some products using non-return valves to hold cell pressure for a period. Alarm perceptibility requires sufficient audible and visual intensity to be noticed in a ward or home. Mute functions should be time-limited rather than permanent. And rapid deflation for resuscitation is needed so that the surface can be flattened quickly in an emergency, through a device that is simple to operate. Rapid deflation is an emergency function: its location must be conspicuous, its operation simple and its action fast, and deflation time should be measured during verification.

Other items. Noise from the pump affects sleep and matters genuinely for a product used continuously. Microclimate depends on surface breathability affecting interface temperature and humidity. Cleaning and disinfection covers cover tolerance and cell cleaning. Durability covers performance retention in prolonged operation, including cell material ageing and pump life. And fire performance covers flammability requirements applicable to bedding.

How we handle it. For mattress verification we record interface pressure continuously across complete cycles and analyse the duration of high pressure rather than peaks alone, since that corresponds to the core value of alternating pressure. We also suggest bottoming-out detection at the upper weight limit, because that is a silent failure neither user nor carer readily notices and testing is the only way to confirm it.

Send us the product parameters and intended range and we will work out the test approach. Phone or WeChat: +86 132 4819 8029.