Background

Impulse oscillometry (IOS) is a noninvasive method based on the forced oscillation technique able to detect small airway dysfunction (SAD) in asthma. We aimed to analyze the prevalence and the functional features of IOS-defined SAD across the different Global Initiative for Asthma (GINA) steps.

Methods

A cross-sectional, single-center study in which 400 consecutive adult patients with physician-diagnosed, community-managed asthma underwent standard spirometry and IOS, and were stratified by stepwise GINA classification. SAD was defined by IOS as a fall in resistance from 5 to 20 Hz [R5–R20]>0.07kPa × s × L⁻¹.

Results

The prevalence of IOS-defined SAD ranged between 58.3% (GINA step 2) and 78.6% (GINA step 5), without statistically significant difference within GINA steps (p > 0.05 in all comparisons). Isolated SAD (i.e. without proximal airways involvement) was similarly represented across GINA steps 2–4. Peripheral airways resistance (R5-R20) tended to a progressive increase with the worsening of GINA steps, and was significantly higher in steps 4–5 compared to the other steps (p < 0.05).

The proportion of patients with FEF_25–75%-defined SAD (<60%) was lower than the IOS-defined one in GINA steps 2–4 (p < 0.05). Only non-significant or weak inverse correlations between R5-R20 and FEF_25–75% were observed within each GINA step, with the exception of GINA step 5, which showed a strong, inverse correlation (r = −0.80, p = 0.0005).

Conclusions

This study shows that first, IOS-defined SAD is overwhelmingly present across asthma severities; second, airways resistance increases with the worsening of GINA steps; and third, SAD may be overlooked by standard spirometry, especially in milder asthma.

中文翻译：

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IOS 定义的小气道疾病在哮喘严重程度中的患病率和特征

背景

脉冲示波法 (IOS) 是一种基于强迫振荡技术的无创方法，能够检测哮喘患者的小气道功能障碍 (SAD)。我们旨在分析 IOS 定义的 SAD 在不同全球哮喘倡议 (GINA) 步骤中的患病率和功能特征。

方法

一项横断面、单中心研究，其中 400 名由医生诊断的社区管理的哮喘成年患者连续接受标准肺活量测定和 IOS，并通过逐步 GINA 分类进行分层。IOS 将 SAD 定义为从 5 到 20 Hz [R5–R20]>0.07kPa × s × L ^{-1 的}电阻下降。

结果

IOS 定义的 SAD 的患病率介于 58.3%（GINA 步骤 2）和 78.6%（GINA 步骤 5）之间，在 GINA 步骤内没有统计学上的显着差异（在所有比较中 p > 0.05）。孤立的 SAD（即没有近端气道受累）在 GINA 步骤 2-4 中也有类似表现。随着 GINA 步骤的恶化，外周气道阻力 (R5-R20) 趋于逐渐增加，并且与其他步骤相比，步骤 4-5 中的阻力显着更高 (p < 0.05)。

FEF _25–75%定义的 SAD (<60%)患者比例低于 GINA 步骤 2–4 中 IOS 定义的患者比例(p < 0.05)。在每个 GINA 步骤中仅观察到R5-R20 和 FEF _25-75%之间不显着或弱的负相关，但 GINA 步骤 5 除外，它显示出强烈的负相关（r = -0.80，p = 0.0005） .

结论

该研究表明，首先，IOS 定义的 SAD 绝大多数存在于哮喘严重程度中；第二，气道阻力随着 GINA 步数的加重而增加；第三，标准肺活量测定法可能会忽略 SAD，尤其是在轻度哮喘中。