Importance In therapeutic trials for acute viral bronchiolitis, consistent clinical improvement in groups that received nebulized normal saline (NS) as placebo raises the question of whether nebulized NS acts as a treatment rather than a placebo. Objective To measure the short-term association of nebulized NS with physiologic measures of respiratory status in children with bronchiolitis by analyzing the changes in these measures between the use of nebulized NS and the use of other placebos and the changes before and after nebulized NS treatment. Data Sources MEDLINE and Scopus were searched through March 2019, as were bibliographies of included studies and relevant systematic reviews, for randomized clinical trials evaluating nebulized therapies in bronchiolitis. Study Selection Randomized clinical trials comparing children 2 years or younger with bronchiolitis who were treated with nebulized NS were included. Studies enrolling a treatment group receiving an alternative placebo were included for comparison of NS with other placebos. Data Extraction and Synthesis Data abstraction was performed per PRISMA guidelines. Fixed- and random-effects, variance-weighted meta-analytic models were used. Main Outcomes and Measures Pooled estimates of the association with respiratory scores, respiratory rates, and oxygen saturation within 60 minutes of treatment were generated for nebulized NS vs another placebo and for change before and after receiving nebulized NS. Results A total of 29 studies including 1583 patients were included. Standardized mean differences in respiratory scores for nebulized NS vs other placebo (3 studies) favored nebulized NS by -0.9 points (95% CI, -1.2 to -0.6 points) at 60 minutes after treatment (P < .001). There were no differences in respiratory rate or oxygen saturation comparing nebulized NS with other placebo. The standardized mean difference in respiratory score (25 studies) after nebulized NS was -0.7 (95% CI, -0.7 to -0.6; I2 = 62%). The weighted mean difference in respiratory scores using a consistent scale (13 studies) after nebulized NS was -1.6 points (95% CI, -1.9 to -1.3 points; I2 = 72%). The weighted mean difference in respiratory rate (17 studies) after nebulized NS was -5.5 breaths per minute (95% CI, -6.3 to -4.6 breaths per minute; I2 = 24%). The weighted mean difference in oxygen saturation (23 studies) after nebulized NS was -0.4% (95% CI, -0.6% to -0.2%; I2 = 79%). Conclusions and Relevance Nebulized NS may be an active treatment for acute viral bronchiolitis. Further evaluation should occur to establish whether it is a true placebo.

中文翻译：

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评估雾化生理盐水在急性病毒性细支气管炎患者中的安慰剂状态

重要性 在急性病毒性细支气管炎的治疗试验中，接受雾化生理盐水 (NS) 作为安慰剂的组的持续临床改善提出了雾化 NS 是否作为治疗而不是安慰剂的问题。目的通过分析使用雾化 NS 与使用其他安慰剂之间这些指标的变化以及雾化 NS 治疗前后的变化，测量雾化 NS 与毛细支气管炎患儿呼吸状态生理指标的短期关联。数据来源 MEDLINE 和 Scopus 以及纳入研究的参考书目和相关系统评价均在 2019 年 3 月进行了搜索，以进行评估细支气管炎雾化疗法的随机临床试验。研究选择 随机临床试验比较了接受雾化 NS 治疗的 2 岁或以下患有细支气管炎的儿童。纳入了接受替代安慰剂治疗组的研究，用于比较 NS 与其他安慰剂。数据提取和综合 数据提取是按照 PRISMA 指南进行的。使用了固定效应和随机效应、方差加权的元分析模型。主要结果和测量 对雾化 NS 与另一种安慰剂以及接受雾化 NS 前后变化的治疗后 60 分钟内与呼吸评分、呼吸频率和氧饱和度的相关性的汇总估计值。结果共纳入29项研究，1583例患者。在治疗后 60 分钟，雾化 NS 与其他安慰剂（3 项研究）呼吸评分的标准化平均差异有利于雾化 NS 的 -0.9 分（95% CI，-1.2 至 -0.6 分）（P < .001）。将雾化 NS 与其他安慰剂相比，呼吸频率或氧饱和度没有差异。雾化 NS 后呼吸评分的标准化平均差异（25 项研究）为 -0.7（95% CI，-0.7 至 -0.6；I2 = 62%）。雾化 NS 后使用一致量表（13 项研究）的呼吸评分加权平均差异为 -1.6 分（95% CI，-1.9 至 -1.3 分；I2 = 72%）。雾化 NS 后呼吸频率的加权平均差异（17 项研究）为每分钟 -5.5 次呼吸（95% CI，每分钟 -6.3 至 -4.6 次呼吸；I2 = 24%）。雾化 NS 后氧饱和度的加权平均差异（23 项研究）为 -0.4%（95% CI，-0.6% 至 -0.2%；I2 = 79%）。结论和相关性 雾化 NS 可能是急性病毒性细支气管炎的有效治疗方法。应进一步评估以确定它是否是真正的安慰剂。