Background

The forced oscillation technique (FOT) enables non-invasive measurement of respiratory system impedance. Limited data exists on how changes in operating lung volume (OLV) impact FOT-derived measures of airway resistance (Rrs) and reactance (Xrs).

Objectives

This study examined the reproducibility and responsiveness of FOT-derived measures of Rrs and Xrs during simulated changes in OLV.

Methods

Participants simulated breathing at six OLVs: total lung capacity (TLC), ∼50% of inspiratory reserve volume (IRV₅₀), ∼two-times tidal volume (VT₂), tidal volume (VT), ∼50% of expiratory reserve volume (ERV₅₀), and residual volume (RV), on a commercially available FOT device. Each simulated OLV manuever was performed in triplicate and in random order. Total Rrs and Xrs were recorded at 5, 11, and 19 Hz.

Results

Twelve healthy participants (2 female) completed the study (weight: 76.5 ± 13.6 kg, height: 178.6 ± 9.7 cm, body mass index: 23.9 ± 3.1 kg/m²). Reproducibility of Rrs and Xrs at VT, VT₂ and IRV₅₀ was good to excellent (Range: ICC: 0.89–0.98, 95% confidence interval (CI): 0.70–0.98), while reproducibility at TLC, RV, and ERV₅₀ was poor to excellent (Range: ICC: 0.60–0.98, 95% CI: 0.36–0.97). Rrs and Xrs were not different between VT and VT₂ at any frequency (P > .05). With lung hyperinflation from VT to TLC, Rrs and Xrs decreased at all three frequencies (e.g., At 5 Hz Rrs: mean difference (MD): − 0.89, 95%CI: − 0.03 to − 1.75, P = .04; Xrs: MD: − 0.56, 95%CI: − 0.25 to − 0.86, P < .01). With lung hypoinflated from VT to RV, Rrs increased, and Xrs decreased for all frequencies (e.g., MD at 5 Hz, Rrs: MD: 2.31, 95%CI: 0.94–3.67, P < .01; Xrs: MD: −2.53, 95%CI: −4.02 to −1.04, P < .01).

Conclusion

FOT-derived measures of airway Rrs and Xrs are reproducible across a range of OLV’s, and are responsive to hyper- and hypo-inflation of the lung. To further understand the impact of lung hyper- and hypo-inflation on FOT-derived airway impedance additional study is required in individuals with pathological variations in operating lung volume.

中文翻译：

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气道阻抗测量的再现性和响应性源自不同操作肺容量的受迫振荡技术

背景

受迫振荡技术 (FOT) 可实现呼吸系统阻抗的无创测量。关于工作肺容量 (OLV) 的变化如何影响 FOT 衍生的气道阻力 (Rrs) 和电抗 (Xrs) 测量值的数据有限。

目标

本研究检验了模拟 OLV 变化期间 FOT 衍生的 Rrs 和 Xrs 测量值的再现性和响应性。

方法

参与者模拟六个 OLV 的呼吸：总肺活量 (TLC)、~50% 补吸气量 (IRV ₅₀ )、~两倍潮气量 (VT ₂ )、潮气量 (VT)、~50% 补呼气量(ERV ₅₀ ) 和残余体积 (RV)，在市售 FOT 设备上进行。每个模拟 OLV 操作均按随机顺序重复三次。总 Rrs 和 Xrs 在 5、11 和 19 Hz 处记录。

结果

12 名健康参与者（2 名女性）完成了研究（体重：76.5 ± 13.6 kg，身高：178.6 ± 9.7 cm，体重指数：23.9 ± 3.1 kg/m ²）。VT、VT ₂和 IRV ₅₀时 Rrs 和 Xrs 的重现性为良好至极好（范围：ICC：0.89–0.98，95% 置信区间 (CI)：0.70–0.98），而 TLC、RV 和 ERV ₅₀的重现性为从差到优秀（范围：ICC：0.60–0.98，95% CI：0.36–0.97）。在任何频率下， VT 和 VT ₂之间的 Rrs 和 Xrs 均无差异( P  > .05)。随着肺过度充气从 VT 到 TLC，Rrs 和 Xrs 在所有三个频率下均下降（例如，5 Hz 时 Rrs：平均差 (MD)：− 0.89，95% CI：− 0.03 至 − 1.75，P  = .04；Xrs： MD：− 0.56，95%CI：− 0.25 至− 0.86，P  < .01）。随着肺从 VT 到 RV 肺充气不足，所有频率的 Rrs 增加，Xrs 减少（例如，5 Hz 时的 MD，Rrs：MD：2.31，95%CI：0.94–3.67，P  < .01；Xrs：MD：-2.53 ，95%CI：-4.02 至 -1.04，P  < .01）。

结论

FOT 衍生的气道 Rrs 和 Xrs 测量在一系列 OLV 中可重复，并且对肺部过度充气和低充气有反应。为了进一步了解肺过度充气和低充气对 FOT 衍生的气道阻抗的影响，需要对工作肺容量存在病理变化的个体进行额外的研究。