Optimizing PEEP to Improve Rates of Ventilator Associated Events in the Medical Intensive Care Unit

Abstract

Background: The National Healthcare Safety Network (NHSN) developed a new algorithm as an approach to improve monitoring for the physiologic changes contributory to ventilator-associated events (VAE), and identified subgroups of ventilator associated conditions (VAC), infection-related ventilator-associated conditions (IVAC) and possible ventilator-associated pneumonia (PVAP). After introduction of the new surveillance definition, we noted in our MICU the majority of PEEP changes triggering VAEs were unrelated to true ventilator-associated complications. It is known that mechanical ventilation is associated with reductions in functional residual capacity (FRC), which, can result in atelectasis. Given the FRC in ventilated patients is determined by PEEP, we hypothesized optimizing PEEP settings at higher starting levels would allow for better identification of clinically significant VAEs.

Methods: We initiated a pilot intervention across 25-beds in 2 MICUs at our urban tertiary care institution in March 2019. All newly ventilated patients were initiated at a starting PEEP of 8 cm H₂O rather than 5. Respiratory therapists, intensivists, and nursing staff were educated as to the protocol, and local champions were identified to ensure adherence. The new baseline PEEP allowed for minimal disruption in patient care, as spontaneous breathing trials and weaning could be conducted per usual practice. Other ventilator bundle components were maintained throughout both periods with a ≥ 75% compliance rate. We then compared pre- and post-intervention rates of VAEs.

Results: There were 419 mechanically ventilated patients in the pre-intervention group, and 427 in the post-intervention group. After initiation of the higher baseline PEEP protocol, we found an approximate 50% reduction in rates of total VAE, along with reductions in IVAC and PVAP by 25-30% (Table 1). Comparative trends in VAC, IVAC and PVAP diagnoses between the two periods of interest are depicted in Figure 1.

Conclusions: Our data suggest optimizing baseline PEEP may help to reduce VAE in the MICU setting. As the intent of the new NHSN definition was to capture physiologic processes other than infectious pneumonia, the mechanism of our results may have been through reduction of atelectasis or other ventilator-induced lung injury. Further study will help to determine generalizability of this practice to non-MICU settings, and also measure its impact on outcomes such as antibiotic utilization.

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