Non-invasive positive pressure ventilation (NIPPV) is one of the important methods to treat acute exacerbation of chronic obstructive pulmonary disease (AECOPD). NIPPV combined with airway clearance therapy can effectively avoid endotracheal intubation and reduced length of hospital stay. The pathological characteristics of AECOPD make the indication of routine evaluation of airway suction lose its guiding value, frequent or delayed airway sputum aspiration is not beneficial to the positive pressure ventilation treatment of patients with acute phase of disease.

To establish the relationship between the oxygenation dropped dramatically after suction and respiratory effort index (ROX index and VOX index) in patients with AECOPD treated with NIPPV, and the predictive value of respiratory drive index on the time of suction.

Convenience sampling method was used, to investigate 140 AECOPD patients with NIPPV treated in the emergency intensive care unit of Qingdao Municipal Hospital from October 2022 to November 2023, the ROX index and VOX index were monitored and calculated within 24 h of non-invasive positive pressure ventilation and during sputum aspiration, the frequency and duration of a dramatic drop in SpO₂ (>10%) after sputum aspiration were assessed. Then analyzed the correlation between ROX index, VOX index and SpO₂ sharp drop after sputum aspiration, and ROX index and VOX index were plotted to predict the receiver operating characteristic (ROC) curve of SpO₂ sharp drop after sputum aspiration.

One hundred and forty patients within 24 hours a total of 861 sputum aspiration, SpO₂ decreased sharply after sputum aspiration in 98 patients (70.0%) ; in 96 patients (68.6%), the incidence of SpO₂ decrease was more than 60%; in 75 patients (53.6%), SpO₂ decreased dramatically for 16-30 seconds, and in 10 patients (7.1%), SpO₂ decreased more than 30 seconds. The baseline ROX index and the ROX index 1 hour before sputum aspiration were negatively correlated with the incidence and duration of SpO₂ decrease after sputum aspiration (P<0.05), baseline VOX index and VOX index 1 hour before sputum aspiration were positively correlated with the incidence and duration of SpO₂ sharp decline after sputum aspiration (P<0.05). The area under the ROC curve of the baseline VOX index was 0.970 (95%CI=0.939-0.967), the best threshold was 0.007 4; the area under the ROC curve of the VOX index 1 hour before sputum aspiration was 0.893 (95%CI=0.826-0.959), the best threshold was 0.008 7.

When VOX index ≥0.007 4 after 1 h of NIPPV and VOX index ≥0.008 7 within 1 h before sputum aspiration, we should be alert to the occurrence of dramatic SpO₂ reduction after sputum aspiration.

无创正压通气技术是治疗慢性阻塞性肺疾病急性加重的重要手段之一，无创正压通气治疗结合气道廓清技术可有效避免患者气管插管，缩短住院时间。慢性阻塞性肺疾病急性加重期（AECOPD）的病理特点使常规评估气道内吸引的指征失去指导价值，频繁或延迟的气道内痰液吸引均不利于患者急性期的正压通气治疗。

分析无创正压通气的AECOPD患者呼吸驱动指标（ROX指数与VOX指数）与吸痰后血氧饱和度（SpO₂）剧烈下降的相关性及呼吸驱动指标对吸痰时机的预测价值。

采用便利抽样法，于2022年10月—2023年11月，选取青岛市市立医院急诊监护室（EICU）住院的140例AECOPD行无创正压通气的患者为研究对象。于患者行无创正压通气24 h内及吸痰时监测并计算ROX指数和VOX指数，评估患者吸痰后SpO₂剧烈下降（>10%）的发生率和持续时间。分析ROX指数、VOX指数与吸痰后SpO₂剧烈下降的相关性，并绘制ROX指数、VOX指数预测吸痰后SpO₂剧烈下降发生的受试者工作特征（ROC）曲线。

140例患者24 h内累计吸痰861次，98例（70.0%）患者发生吸痰后SpO₂剧烈下降；96例（68.6%）患者吸痰后SpO₂剧烈下降发生率≥60%；75例（53.6%）患者吸痰后SpO₂剧烈下降持续时间16~30 s，10例（7.1%）患者吸痰后SpO₂剧烈下降持续时间>30 s。基线ROX指数、吸痰前1 h ROX指数与吸痰后SpO₂剧烈下降发生率及持续时间均呈负相关（P<0.05），基线VOX指数、吸痰前1 h VOX指数与吸痰后SpO₂剧烈下降发生率及持续时间均呈正相关（P<0.05）。基线VOX指数预测吸痰后SpO₂剧烈下降的ROC曲线下面积为0.970（95%CI=0.939~0.967），最佳截断值为0.007 4；吸痰前1 h VOX指数预测吸痰后SpO₂剧烈下降的ROC曲线下面积为0.893（95%CI=0.826~0.959），最佳截断值为0.008 7。

当行无创通气1 h后VOX指数≥0.007 4，吸痰前1 h内VOX指数≥0.008 7时，应警惕患者吸痰后SpO₂剧烈下降的发生。