Limiting driving pressure - Does it affect mortality?

Article

Auteur: Christine Wu

Date: 16.12.2024

The authors' point? Limiting static or dynamic ∆P can further reduce the mortality of patients requiring mechanical ventilation.

Limiting driving pressure - Does it affect mortality?

Clinical question

Does sustained limitation of driving pressure; both static (ΔP) and dynamic (ΔPdyn), reduce 30-day mortality in mechanically ventilated ICU patients with acute respiratory failure compared to usual care?

Cliinical background

ICU patients requiring mechanical ventilation, especially those with acute respiratory distress syndrome (ARDS), face mortality rates as high as 40%.
To reduce the risk of ventilator-induced lung injury (VILI), clinicians have traditionally limited tidal volumes and plateau pressures during mechanical ventilation. This approach aims to minimize lung over-distension and barotrauma.
In prior studies, higher ΔP has been associated with increased mortality, but these analyses typically focused on baseline parameters and did not assess the impact of ongoing intervention to limit ΔP.
ΔP is often challenging to measure, especially in spontaneously breathing patients.
Unlike ΔP, ΔPdyn can be monitored continuously by modern ventilators, regardless of the ventilation mode. This makes it a more practical parameter for tracking lung mechanics and adjusting ventilation in real time.
It remains unclear whether a treatment strategy that actively limits ΔP over time is more effective than conventional ventilation in improving clinical outcomes.

Design and setting

Retrospective cohort study: A retrospective cohort design was used to assess the effects of sustained interventions on both ΔP and ΔPdyn in critically ill, mechanically ventilated patients (Urner M, Jüni P, Rojas-Saunero LP, et al. Limiting Dynamic Driving Pressure in Patients Requiring Mechanical Ventilation. Crit Care Med. 2023;51(7):861-871. doi:10.1097/CCM.00000000000058441).
Emulated pragmatic trial: Observational data was used to simulate the impact of various mechanical ventilation strategies on patient outcomes.
Data source: Toronto Intensive Care Observational Registry, which recorded information from April 2014 to August 2021, encompassing 12,865 patients across nine ICUs affiliated with seven University of Toronto hospitals.

Patients

Adult patients (≥ 18 yrs) 24 hours or more of invasive or noninvasive mechanical ventilation.


Inclusion criteria	Mechanical ventilation lasting more than 24 hours Exposed to positive-pressure ventilation within the first 24 hours after ICU admission Available measurements for ΔP at baseline (for ΔP analyses) For patients with multiple admissions, only the data from the first admission was considered and among those, only the first episode of ventilation lasting more than 24 hours was included in the analysis
Exclusion criteria	Mechanical ventilation lasting 24 hours or less Patients who did not receive positive-pressure ventilation (e.g., only high flow nasal oxygen therapy) during the first 24 hours in the ICU. Patients without baseline ΔP measurements

Inclusion criteria

Mechanical ventilation lasting more than 24 hours
Exposed to positive-pressure ventilation within the first 24 hours after ICU admission
Available measurements for ΔP at baseline (for ΔP analyses)
For patients with multiple admissions, only the data from the first admission was considered and among those, only the first episode of ventilation lasting more than 24 hours was included in the analysis

Exclusion criteria

Mechanical ventilation lasting 24 hours or less
Patients who did not receive positive-pressure ventilation (e.g., only high flow nasal oxygen therapy) during the first 24 hours in the ICU.
Patients without baseline ΔP measurements

Intervention


Comparison of ventilation strategies	Compared strategies limiting daily ΔP or ΔPdyn to ≤ 15 cmH2O with usual care practices.
Threshold selection	Chosen based on prior studies using thresholds of 14 or 15 cmH2O for ΔP or ΔPdyn; ΔPdyn may underestimate spontaneous breathing contributions.
ΔP calculation	Calculated as plateau pressure minus positive end-expiratory pressure (PEEP) during occlusion manuevers.
ΔPdyn calculation	For mechanically ventilated patients: Daily ΔPdyn = peak inspiratory pressure (PIP) − PEEP For noninvasive ventilation: Daily ΔPdyn = inspiratory positive airway pressure (IPAP) − expiratory positive airway pressure (EPAP)
Additional analyses	Investigated various other thresholds for ΔP and ΔPdyn that could be targeted during mechanical ventilation.

Measurements and main results

Outcomes and duration of follow-up


Primary outcome	Ventilator mortality up to 30 days. Competing events: Successful liberation from mechanical ventilation or ICU discharge was considered a competing event for ventilator mortality. Definition of successful liberation: Transition from mechanical ventilation to either room air or supplemental oxygen for more than 48 hours. Follow-up duration: Patients were followed from the initiation of mechanical ventilation (day 0) until death, ICU discharge, successful liberation, or 30 days in the ICU, whichever occurred first. Treatment strategy initiation: Initiated 24 hours after the start of mechanical ventilation (day 1) and sustained throughout the entire duration of mechanical ventilation.
Secondary analyses	Two secondary analyses with modified ventilator procedures were conducted: 1. Investigated the effect on mortality of different ventilation strategies that limit daily tidal volumes or PIPs, irrespective of ΔP levels. 2. Estimated the causal effect on mortality based on the timing and duration of limiting ΔPdyn (≤ 15 cmH2O) with the following strategies: - Early and short intervention (days 1 to 5) - Early but time-limited intervention (days 1 to 14) - Delayed intervention (days 5 to 30) - Late intervention (days 14 to 30)

Primary outcome

Ventilator mortality up to 30 days.
Competing events: Successful liberation from mechanical ventilation or ICU discharge was considered a competing event for ventilator mortality.
Definition of successful liberation: Transition from mechanical ventilation to either room air or supplemental oxygen for more than 48 hours.
Follow-up duration: Patients were followed from the initiation of mechanical ventilation (day 0) until death, ICU discharge, successful liberation, or 30 days in the ICU, whichever occurred first.
Treatment strategy initiation: Initiated 24 hours after the start of mechanical ventilation (day 1) and sustained throughout the entire duration of mechanical ventilation.

Secondary analyses

Two secondary analyses with modified ventilator procedures were conducted:
1. Investigated the effect on mortality of different ventilation strategies that limit daily tidal volumes or PIPs, irrespective of ΔP levels.
2. Estimated the causal effect on mortality based on the timing and duration of limiting ΔPdyn (≤ 15 cmH2O) with the following strategies:
- Early and short intervention (days 1 to 5)
- Early but time-limited intervention (days 1 to 14)
- Delayed intervention (days 5 to 30)
- Late intervention (days 14 to 30)

Main results


Patient population	Data from 19,989 patients were recorded; 12,865 patients were included in the final analysis after excluding: - 4,493 patients (22%) liberated from mechanical ventilation or discharged from the ICU within 24 hours - 2,631 patients (13%) who did not receive positive-pressure ventilation in the first 24 hours
Patient characteristics	Median tidal volume during the first 24 hours: 6.7 ml/kg predicted body weight (IQR: 6.0–7.9 mL/kg) 52% (6,638 patients) were spontaneously breathing 22% (2,794 patients) ventilated in pressure support mode ΔPdyn > 15 cmH2O in 35% (4,468 patients) ΔP measured in 19% (2,473 patients), with 14% > 15 cmH2O
Primary analysis	Estimated ventilator mortality at 30 days: - Usual care: 28.7% (24.1%–51.7%) - Limiting ΔP ≤ 15 cmH2O: 28.1% (23.8%–51.0%) - Absolute risk difference: –0.6% (95% CI: –1.2% to –0.3%); risk ratio: 0.98 (95% CI: 0.96–0.99) Overall population ventilator mortality: - Usual care: 20.1% (19.4%–20.9%). - Limiting ΔPdyn ≤ 15 cmH2O: 18.1% (17.5%–18.9%) - Absolute risk difference: –1.9% (95% CI: –2.2% to –1.7%); risk ratio: 0.90 (95% CI: 0.89–0.92).
Effect of limiting ΔP	A higher proportion of patients liberated from mechanical ventilation or discharged from ICU contributed to reduced mortality (risk ratio: 1.03; 95% CI: 1.03–1.04). ΔPdyn differed by an average of 2 cmH2O between groups after treatment assignment. A dose-dependent reduction in ventilator mortality with stricter limitations on both ΔP and ΔPdyn was observed.
Secondary analyses	Investigated different ventilation strategies limiting tidal volumes or PIPs; these were not associated with reduced mortality compared to usual care. Early and sustained intervention limiting ΔPdyn ≤ 15 cmH2O was more effective than delayed initiation: - Day 5: Risk difference –0.9% (–1.1% to –0.8%) - Day 14: Risk difference –0.3% (–0.4% to –0.2%)
Sensitivity analyses	Findings were robust, accounting for missing data and potential residual confounding.

Conclusion

Limiting either static or dynamic ∆P can further reduce the mortality of patients requiring invasive or noninvasive mechanical ventilation.

Food for thought

Early and sustained interventions on ΔP were more effective than usual practice care in reducing mortality, indicating the importance of timely management in mechanically ventilated patients.
Both ΔP and ΔPdyn should be closely monitored during mechanical ventilation to mitigate the risk of VILI and associated mortality.
Sustained interventions focusing on daily tidal volumes or PIP, irrespective of ΔP levels, did not demonstrate a reduction in ventilator mortality.
The findings apply to a broad population of mechanically ventilated patients, including those with ARDS, highlighting the relevance of the study across various patient types.

How can I incorporate these findings into my daily work with Hamilton Medical technology?

The ability of Hamilton ventilators to display real-time ΔPdyn is crucial, as the study emphasizes the importance of monitoring ΔP to mitigate risks associated with VILI.
This feature allows clinicians to make timely adjustments to ventilation strategies for greater patient safety and improved outcomes.
Being able to review ΔPdyn and other lung mechanics’ parameters, along with their trends over extended periods, gives clinicians valuable insights into the patient’s respiratory status.
This long-term data collection and trend analysis are valuable for adjusting ventilation strategies and evaluating the effectiveness of interventions, particularly during the early stages of mechanical ventilation.

Notes en bas de page

Références

1. Urner M, Jüni P, Rojas-Saunero LP, et al. Limiting Dynamic Driving Pressure in Patients Requiring Mechanical Ventilation. Crit Care Med. 2023;51(7):861-871. doi:10.1097/CCM.0000000000005844

Limiting Dynamic Driving Pressure in Patients Requiring Mechanical Ventilation.

Urner M, Jüni P, Rojas-Saunero LP, et al. Limiting Dynamic Driving Pressure in Patients Requiring Mechanical Ventilation. Crit Care Med. 2023;51(7):861-871. doi:10.1097/CCM.0000000000005844

Link to article

OBJECTIVES

Previous studies reported an association between higher driving pressure (∆P) and increased mortality for different groups of mechanically ventilated patients. However, it remained unclear if sustained intervention on ∆P, in addition to traditional lung-protective ventilation, improves outcomes. We investigated if ventilation strategies limiting daily static or dynamic ∆P reduce mortality compared with usual care in adult patients requiring greater than or equal to 24 hours of mechanical ventilation.

DESIGN

For this comparative effectiveness study, we emulated pragmatic clinical trials using data from the Toronto Intensive Care Observational Registry recorded between April 2014 and August 2021. The per-protocol effect of the interventions was estimated using the parametric g-formula, a method that controls for baseline and time-varying confounding, as well as for competing events in the analysis of longitudinal exposures.

SETTING

Nine ICUs from seven University of Toronto-affiliated hospitals.

PATIENTS

Adult patients (≥18 yr) requiring greater than or equal to 24 hours of mechanical ventilation.

INTERVENTIONS

Receipt of a ventilation strategy that limited either daily static or dynamic ∆P less than or equal to 15 cm H 2 O compared with usual care.

MEASUREMENTS AND MAIN RESULTS

Among the 12,865 eligible patients, 4,468 of (35%) were ventilated with dynamic ∆P greater than 15 cm H 2 O at baseline. Mortality under usual care was 20.1% (95% CI, 19.4-20.9%). Limiting daily dynamic ∆P less than or equal to 15 cm H 2 O in addition to traditional lung-protective ventilation reduced adherence-adjusted mortality to 18.1% (95% CI, 17.5-18.9%) (risk ratio, 0.90; 95% CI, 0.89-0.92). In further analyses, this effect was most pronounced for early and sustained interventions. Static ∆P at baseline were recorded in only 2,473 patients but similar effects were observed. Conversely, strict interventions on tidal volumes or peak inspiratory pressures, irrespective of ∆P, did not reduce mortality compared with usual care.

CONCLUSIONS

Limiting either static or dynamic ∆P can further reduce the mortality of patients requiring mechanical ventilation.