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, 23 (1), 105

Safety and Efficacy of Volume-Based Feeding in Critically Ill, Mechanically Ventilated Adults Using the 'Protein & Energy Requirements Fed for Every Critically Ill Patient Every Time' (PERFECT) Protocol: A Before-And-After Study


Safety and Efficacy of Volume-Based Feeding in Critically Ill, Mechanically Ventilated Adults Using the 'Protein & Energy Requirements Fed for Every Critically Ill Patient Every Time' (PERFECT) Protocol: A Before-And-After Study

Sue Brierley-Hobson et al. Crit Care.


Background: Underfeeding in critical illness is common and associated with poor outcomes. According to large prospective hospital studies, volume-based feeding (VBF) safely and effectively improves energy and protein delivery to critically ill patients compared to traditional rate-based feeding (RBF) and might improve patient outcomes. A before-and-after study was designed to evaluate the safety, efficacy and clinical outcomes associated with VBF compared to RBF in a single intensive care unit (ICU).

Methods: The sample included consecutively admitted critically ill adults, mechanically ventilated for at least 72 h and fed enterally for a minimum of 48 h. The first cohort (n = 46) was fed using RBF, the second (n = 46) using VBF, and observed for 7 days, or until extubation or death. Statistical comparison of percentage feed volume, energy and protein delivered, plus indices of feed intolerance, were the primary outcomes of interest. Secondary observations included ventilation period, mortality, and length of ICU stay (LOICUS).

Results: Groups were comparable in baseline clinical and demographic characteristics and nutrition practices. Volume delivered to the VBF group increased significantly by 11.2% (p ≤ 0.001), energy by 13.4% (p ≤ 0.001) and protein by 8.4% (p = 0.02), compared to the RBF group. In the VBF group, patients meeting > 90% of energy requirements increased significantly from 47.8 to 84.8% (p ≤ 0.001); those meeting > 90% of protein requirements changed from 56.5 to 73.9% (p = 0.134). VBF did not increase symptoms of feed intolerance. Adjusted binomial logistic regression found each additional 1% of prescribed feed delivered decreased the odds of vomiting by 0.942 (5.8%), 95% CI [0.900-0.985], p = 0.010. No differences in mortality or LOICUS were identified. Kaplan-Meier found a significantly increased extubation rate in patients receiving > 90% of protein requirements compared to those meeting < 80%, (p = 0.006). Adjusted Cox regression found the daily probability of being extubated tripled in patients receiving > 90% of their protein needs compared to the group receiving < 80%, hazard ratio 3.473, p = 0.021, 95% CI [1.205-10.014].

Conclusion: VBF safely and effectively increased the delivery of energy and protein to critically ill patients. Increased protein delivery may improve extubation rate which has positive patient-centred and financial implications, warranting larger confirmatory trials. This investigation adds weight to the ICU literature supporting VBF, and the growing evidence which advocates for enhanced protein delivery to improve patient outcomes.

Keywords: Critical care; Enteral; Mechanical ventilation; Protein; Volume-based feeding.

Conflict of interest statement

Ethics approval and consent to participate

This is discussed in ‘methods’ as follows:

The study did not require informed patient consent: the system-level quality improvement initiative was designed to undertake a minimal-risk change in feed process which did not exceed the boundaries of standard clinical care, and could not take place practically if prior consent were required [11, 23]. The Local Health Board ‘Research and Development’ department consented to the work as a service evaluation project without need to pursue ethical review. The required University Healthcare Sciences and Medical Sciences Academics Ethics Committee approval was obtained before data analysis.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.


Fig. 1
Fig. 1
Number of evaluable feeding days in RBF and VBF groups. Figure shows the number of evaluable feeding days, and the p value of Fisher’s exact test demonstrating no significant group differences
Fig. 2
Fig. 2
Daily median percentage feed volume delivered to RBF and VBF groups. Figure shows median 95% CI error bars, n per sample, and Mann-Whitney U result which found statistically significant increases in volume delivered to the VBF group compared to the RBF group every day
Fig. 3
Fig. 3
Kaplan-Meier 60-day survival curves by group; shows no difference in 60-day survival
Fig. 4
Fig. 4
Kaplan-Meier curves; time to extubation by group
Fig. 5
Fig. 5
Kaplan-Meier curves for time to extubation by percentage of prescribed protein delivered: shows 75th centile, days by which 25% of each group extubated and the cumulative probability (discussed as %) of remaining ventilated at day 10
Fig. 6
Fig. 6
Kaplan-Meier curves: LOICUS by RBF and VBF group

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    1. McClave SA, Taylor BE, Martindale RG, Warren MM, Johnson DR, Braunschweig C, et al. Guidelines for the provision and assessment of nutrition support therapy in the adult critically ill patient: Society of Critical Care Medicine and American Society for Parenteral nutrition. JPEN J Parenter Enteral Nutr. 2016;40:159–211. doi: 10.1177/0148607115621863. - DOI - PubMed
    1. 1000 Lives Plus. How to guide: improving critical care. The Health Foundation: Inspiring Improvement. 2010. Accessed 20 Aug 2017.
    1. Pichard C, Oshima T, Berger MM. Energy deficit is clinically relevant for critically ill patients: yes. Intensive Care Med. 2015;41:335–338. doi: 10.1007/s00134-014-3597-9. - DOI - PubMed
    1. Alberda C, Gramlich L, Jones N, Jeejeebhoy K, Day AG, Dhaliwal R, Heyland DK. The relationship between nutritional intake and clinical outcomes in critically ill patients: results of an international multicentre observational study. Intensive Care Med. 2009;35:1728–1737. doi: 10.1007/s00134-009-1567-4. - DOI - PubMed
    1. Elke G, Wang M, Weiler N, Day AG, Heyland DK. Close to recommended caloric and protein intake by enteral nutrition is associated with better clinical outcome of critically ill septic patients: secondary analysis of a large nutrition database. Crit Care. 2014;18:R29. doi: 10.1186/cc13720. - DOI - PMC - PubMed

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