University of Canterbury, Christchurch, 8041, New Zealand.
Biomed Eng Online. 2013 Jan 31;12:9. doi: 10.1186/1475-925X-12-9.
Acute Respiratory Distress Syndrome (ARDS) is characterized by inflammation, filling of the lung with fluid and the collapse of lung units. Mechanical ventilation (MV) is used to treat ARDS using positive end expiratory pressure (PEEP) to recruit and retain lung units, thus increasing pulmonary volume and dynamic functional residual capacity (dFRC) at the end of expiration. However, simple, non-invasive methods to estimate dFRC do not exist.
Four model-based methods for estimating dFRC are compared based on their performance on two separate clinical data cohorts. The methods are derived from either stress-strain theory or a single compartment lung model, and use commonly controlled or measured parameters (lung compliance, plateau airway pressure, pressure-volume (PV) data). Population constants are determined for the stress-strain approach, which is implemented using data at both single and multiple PEEP levels. Estimated values are compared to clinically measured values to assess the reliability of each method for each cohort individually and combined.
The stress-strain multiple breath (at multiple PEEP levels) method produced an overall correlation coefficient R2 = 0.966. The stress-strain single breath method produced R2 = 0.530. The single compartment single breath method produced R2 = 0.415. A combined method at single and multiple PEEP levels produced R2 = 0.963.
The results suggest that model-based, single breath and non-invasive approaches to estimating dFRC may be viable in a clinical scenario, ensuring no interruption to MV. The models provide a means of estimating dFRC at any PEEP level. However, model limitations and large estimation errors limit the use of the methods at very low PEEP.
急性呼吸窘迫综合征（ARDS）的特征是炎症、肺部充满液体以及肺单位塌陷。机械通气（MV）用于通过使用呼气末正压（PEEP）来治疗 ARDS，以募集和保留肺单位，从而增加肺容量和呼气末的动态功能残气量（dFRC）。然而，不存在简单的、非侵入性的估计 dFRC 的方法。
基于在两个独立的临床数据队列中的性能，比较了四种用于估计 dFRC 的基于模型的方法。这些方法源自应变理论或单腔室肺模型，并且使用通常受控制或测量的参数（肺顺应性、平台气道压力、压力-容积（PV）数据）。对于应变理论方法确定了群体常数，该方法使用单个和多个 PEEP 水平的数据来实现。将估计值与临床测量值进行比较，以单独和组合评估每种方法对于每个队列的可靠性。
应变多呼吸（在多个 PEEP 水平下）方法产生的整体相关系数 R2 = 0.966。应变单呼吸方法产生的 R2 = 0.530。单腔室单呼吸方法产生的 R2 = 0.415。在单个和多个 PEEP 水平下的组合方法产生的 R2 = 0.963。
结果表明，基于模型、单呼吸和非侵入性方法来估计 dFRC 在临床情况下可能是可行的，确保 MV 不会中断。这些模型提供了在任何 PEEP 水平下估计 dFRC 的方法。然而，模型限制和大的估计误差限制了这些方法在非常低的 PEEP 下的使用。
