Background

Bedside lung volume measurement could personalise ventilation and reduce driving pressure in patients with acute respiratory distress syndrome (ARDS). We investigated a modified gas-dilution method, the inspired sinewave technique (IST), to measure the effective lung volume (ELV) in pigs with uninjured lungs and in an ARDS model.

Methods

Anaesthetised mechanically ventilated pigs were studied before and after surfactant depletion by saline lavage. Changes in PEEP were used to change ELV. Paired measurements of absolute ELV were taken with IST (ELV_IST) and compared with gold-standard measures (sulphur hexafluoride wash in/washout [ELV_SF6] and computed tomography (CT) [ELV_CT]). Measured volumes were used to calculate changes in ELV (ΔELV) between PEEP levels for each method (ΔELV_IST, ΔELV_SF6, and ΔELV_CT).

Results

The coefficient of variation was <5% for repeated ELV_IST measurements (n=13 pigs). There was a strong linear relationship between ELV_IST and ELV_SF6 in uninjured lungs (r²=0.97), and with both ELV_SF6 and ELV_CT in the ARDS model (r²=0.87 and 0.92, respectively). ELV_IST had a mean bias of –12 to 13% (95% limits=±17 – 25%) compared with ELV_SF6 and ELV_CT. ΔELV_IST was concordant with ΔELV_SF6 and ΔELV_CT in 98–100% of measurements, and had a mean bias of –73 to –77 ml (95% limits=±128 – 186 ml) compared with ΔELV_SF6 and –1 ml (95% limits ±333 ml) compared with ΔELV_CT.

Conclusions

IST provides a repeatable measure of absolute ELV and shows minimal bias when tracking PEEP-induced changes in lung volume compared with CT in a saline-lavage model of ARDS.

中文翻译：

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验证启发性正弦波技术以测量猪肺损伤模型中“婴儿肺”的体积。

背景

床旁肺体积测量可以个性化通气并降低急性呼吸窘迫综合征（ARDS）患者的驾驶压力。我们研究了一种改良的气体稀释方法，即正弦波技术（IST），以测量未受伤肺和ARDS模型中猪的有效肺体积（ELV）。

方法

在用盐水冲洗去除表面活性剂之前和之后，对麻醉的机械通气猪进行了研究。PEEP的变化用于改变ELV。使用IST（ELV _IST）对绝对ELV进行配对测量，并与金标准测量（六氟化硫冲洗/冲洗[ELV _SF6 ]和计算机断层扫描（CT）[ELV _CT ]）进行比较。测量体积用于在ELV（ΔELV）为每个方法PEEP水平之间的变化计算（ΔELV _IST，ΔELV _SF6和ΔELV _CT）。

结果

重复ELV _IST测量的变异系数<5％（n = 13头猪）。在未受伤的肺中，ELV _IST和ELV _SF6之间存在很强的线性关系（r ² = 0.97），在ARDS模型中，ELV _SF6和ELV _CT两者之间有很强的线性关系（r ²分别为0.87和0.92）。与ELV _SF6和ELV _CT相比，ELV _IST的平均偏差为–12至13％（95％限值=±17 – 25％）。ΔELV _IST与ΔELV一致_SF6和ΔELV _CT在测量98-100％，并且具有-73到-77毫升（95％限度=±128 - 186毫升）的平均偏压ΔELV相比_SF6与ΔELV比较和-1毫升（95％的范围±333毫升）_CT。

结论

与ARDS盐水灌洗模型中的CT相比，IST提供了可重复测量的绝对ELV，并且在追踪PEEP诱导的肺体积变化时显示出最小的偏差。