Does tidal volume challenge improve the feasibility of pulse pressure variation in patients mechanically ventilated at low tidal volumes? A systematic review and meta-analysis

Background Pulse pressure variation (PPV) has been widely used in hemodynamic assessment. Nevertheless, PPV is limited in low tidal volume ventilation. We conducted this systematic review and meta-analysis to evaluate whether the tidal volume challenge (TVC) could improve the feasibility of PPV in patients ventilated at low tidal volumes. Methods PubMed, Embase and Cochrane Library inception to October 2022 were screened for diagnostic researches relevant to the predictability of PPV change after TVC in low tidal volume ventilatory patients. Summary receiving operating characteristic curve (SROC), pooled sensitivity and specificity were calculated. Subgroup analyses were conducted for possible influential factors of TVC. Results Ten studies with a total of 429 patients and 457 measurements were included for analysis. The predictive performance of PPV was significantly lower than PPV change after TVC in low tidal volume, with mean area under the receiving operating characteristic curve (AUROC) of 0.69 ± 0.13 versus 0.89 ± 0.10. The SROC of PPV change yielded an area under the curve of 0.96 (95% CI 0.94, 0.97), with overall pooled sensitivity and specificity of 0.92 (95% CI 0.83, 0.96) and 0.88 (95% CI 0.76, 0.94). Mean and median cutoff value of the absolute change of PPV (△PPV) were 2.4% and 2%, and that of the percentage change of PPV (△PPV%) were 25% and 22.5%. SROC of PPV change in ICU group, supine or semi-recumbent position group, lung compliance less than 30 cm H 2 O group, moderate positive end-expiratory pressure (PEEP) group and measurements devices without transpulmonary thermodilution group yielded 0.95 (95%0.93, 0.97), 0.95 (95% CI 0.92, 0.96), 0.96 (95% CI 0.94, 0.97), 0.95 (95% CI 0.93, 0.97) and 0.94 (95% CI 0.92, 0.96) separately. The lowest AUROCs of PPV change were 0.59 (95% CI 0.31, 0.88) in prone position and 0.73 (95% CI 0.60, 0.84) in patients with spontaneous breathing activity. Conclusions TVC is capable to help PPV overcome limitations in low tidal volume ventilation, wherever in ICU or surgery. The accuracy of TVC is not influenced by reduced lung compliance, moderate PEEP and measurement tools, but TVC should be cautious applied in prone position and patients with spontaneous breathing activity. Trial registration PROSPERO (CRD42022368496). Registered on 30 October 2022.