目的 对比早产儿撤机前后右手掌（导管前）和右脚掌（导管后）的无创灌注指数（PI）的差异，探讨机械通气（MV）常频模式是否对其产生影响，阐明呼吸系统严重程度评分（RSS）与PI的相关性。 方法 选择胎龄（GA）≥32周，体质量（BW）≥1 500 g的早产儿，出生后因呼吸窘迫，行无创辅助通气治疗，脉搏血氧饱和度（SpO₂）<90%，需要常频MV辅助呼吸。共纳入符合标准病例55例。出生24 h后符合撤机标准，进行撤机。记录撤机前后右手掌和右脚掌PI稳定后的30 s内数值，取其中位数。同时记录撤机前呼吸机参数吸入气体氧浓度分数（FiO₂）和平均气道压（P_mean）。使用配对样本t检验比较撤机前后患儿右手掌和右脚掌PI差异。采用多元线性回归分析患儿GA、BW和RSS与撤机前右手掌（导管前）PI的相关性及FiO₂和P_mean与PI的相关性。 结果 撤机前右手掌PI低于撤机后（P<0.05），撤机前右脚掌PI低于撤机后（P<0.05）；GA、BW、RSS与PI线性回归分析，GA与PI无相关性（P>0.05），BW与PI存在正相关关系［b=0.44，标准化回归系数（β）=0.25，P<0.05］，RSS与PI存在负相关关系（b=－0.56，β=－0.68，P<0.05），回归方程PI=1.9+0.44×BW－0.56×RSS；进一步对构成RSS的呼吸机参数FiO₂和P_mean进行多元线性回归分析，FiO₂（b=－2.52，β=－0.27，P<0.05）和P_mean（b=－0.39，β=－0.63，P<0.05）均与PI存在线性关系，且为其危险因素，回归系数中P_mean的β值大于FiO₂，前者对PI影响更大。 结论 常频MV模式可以影响PI，该模式下RSS是PI的危险因素，较高的RSS可对循环产生不利影响，其中P_mean较FiO₂对PI影响更大。

Objective To compare the differences in noninvasive perfusion index （PI） before and after extubation between the right palm （ preductal） and right sole （postductal） in the preterm infants，and to discuss whether the conventional frequency mechanical ventilation （MV） mode has an effect on it， and to clarify the correlation between the respiratory severity score （RSS） and PI. Methods The preterm infants with the gestational age （GA） ≥32 weeks and body weight （BW） ≥1 500 g who were born with respiratory distress and underwent noninvasive assisted ventilation therapy， with pulse oxygen saturation （SpO₂） <90%， requiring conventional frequency MV assistance， were selected. A total of 55 patients met the inclusion criteria were included. The extubation was carried out after meeting the criteria 24 h after birth. The median values within 30 s after stabilization of PI in the right palm and right sole were recorded before and after extubation. At the same time， the ventilator parameters such as the fraction of inspired oxygen （FiO₂） and the mean airway pressure （P_mean） before extubation were recorded. The paired samples t-test was used to compare the differences in PI of the right palm and right sole before and after extubation；multivariate linear regression analysis was used to analyze the correlation between GA， BW， and RSS with the preductal PI of the right palm before extubation and the correlation between FiO₂ and P_mean with PI. Results The PI of the right palm before extubation was lower than after extubation （P<0.05）； the PI of the right sole before extubation was lower than that after extubation （P<0.05）； the linear regression analysis results showed there was no correlation between GA and PI （P>0.05）， there was a positive correlation between BW and PI ［b=0.44，standardized regression coefficient （β）=0.25， P<0.05）］， and there was a negative correlation between RSS and PI （b=－0.56， β=－0.68， P<0.05）， and the regression equation was PI=1.9+0.44×BW－0.56×RSS；the further multivariate linear regression analysis results of the ventilator parameters showed that the ventilator parameters constituting the RSS， FiO₂ （b=－2.52， β=－0.27， P<0.05） and P_mean （b=－0.39， β=－0.63， P<0.05）， both showed a linear relationship with PI and they were risk factors for it， and the β value of P_mean was greater than that of FiO₂， indicating that the former had a greater impact on PI. Conclusion The conventional frequency MV mode can affect PI， and RSS under this mode is a risk factor for PI； higher RSS can have an adverse effect on the circulation， and P_mean has a greater impact on PI compared with FiO₂.