Risks factors for prolonged mechanical ventilation (PMV) include patient comorbidities, intubation site, ventilator settings, and various clinical parameters, whereas the risk for weaning failure is apparently related to age and previous mechanical ventilation. These were among findings of a systemic review and meta-analysis on risk factors for PMV and weaning failure, published in Respiration.

Notably, researchers conducting the meta-analysis found that inter-study comparison of risk factors was not possible due to the studies’ inconsistent and overlapping definitions of PMV and MV weaning failure, as well as the heterogeneity of the patient populations studied.

Mechanical ventilation weaning failure and prolonged mechanical ventilation (PMV) place significant burdens on health care systems, patients, and their families. Moreover, these burdens are extended when weaning failure leads to home MV. In Germany, the prospective, multicenter PRiVENT trial was initiated to reduce the number of patients requiring invasive home MV. As part of that trial, the current review sought to identify risk factors for weaning failure and PMV.

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The researchers conducted a systematic review and analysis of 23 studies, including 23,418 patients altogether, identified from the COCHRANE Library, CINHAL, Web of Science, MEDLINE, PubMed, and the LILACS databases from 2007 through June 2020. Reviewers defined PMV as 96 or more hours of mechanical ventilation. The review included studies in German or English examining PMV risk factors, weaning failure, and prolonged weaning. Pediatric studies and those not generalizable to the majority of intensive care unit (ICU) patients were excluded.

Among studies reviewed, 9 analyzed weaning failure risk factors and 14 examined PMV and prolonged weaning risk factors. Researchers found that different studies employed different definitions of what constituted weaning failure, prolonged weaning, and PMV. Notably, weaning failure risks in these studies were primarily related to previous home MV, cause of ventilation, preexisting underlying disease, and age. The reviewers identified the most significant PMV risk factors as ventilator settings, functional parameters, critical care scoring systems, blood gas or laboratory parameters, intubation site, and comorbidities. Spontaneous breathing trials revealing elevated partial pressure of carbon dioxide (PaCO2) levels indicated risks in weaning failure and prolonged weaning.

Overall, because of heterogeneity among studies on PMS and home MV, the researchers said that direct comparison of risk factors was beyond their scope. “The large number of different definitions and relevant parameters reflects the heterogeneity of patients undergoing PMV and those discharged to HMV after unsuccessful weaning,” they noted. “A direct comparison of the studies was not possible because of the large differences in the patient populations studied and the endpoints examined. A comparative analysis with harmonized endpoints would be helpful to identify the most informative parameters.”

 The researchers concluded that multidimensional scores that reflect various aspects of intensive care and ventilator weaning may be better at assessing risk than independent assessment of individual risk factors.

Disclosure: One author of this review is editor-in-chief of the journal in which this article appears.


Trudzinski FC, Neetz B, Bornitz F, et al. Risk factors for prolonged mechanical ventilation and weaning failure: A systematic review. Respiration. Published online August 17, 2022. doi:10.1159/000525604