How to measure driving pressure

Articolo

Autore: Clinical Experts Group, Hamilton Medical

Data: 30.08.2017

Airway driving pressure is associated with clinical outcomes in ARDS, post-surgical, and normal-lung patients, and is a measure of the strain applied to the respiratory system and the risk of ventilator-induced lung injuries. Evidence suggests we should keep driving pressure below 14 cmH2O. But how can we measure it?

Measurement on Hamilton Medical ventilators

Driving pressure = Plateau pressure - Total PEEP

On a Hamilton Medical ventilator you can measure driving pressure in any ventilation mode, provided the patient is relaxed and making no inspiratory or expiratory effort, and there is no leakage from the ventilation circuit.

All you have to do is perform an end-inspiratory hold maneuver and then an end-expiratory hold for 3-5 seconds to measure the plateau pressure and total PEEP respectively.

So driving pressure = inspiratory hold pressure (plateau pressure) - expiratory hold pressure (total PEEP).

End-inspiratory hold

End-inspiratory hold: Press the Tools button to open the Tools -> Hold window and select Insp hold, wait for 3 to 5 seconds, then select Insp hold or press the P&T knob again to deactivate the hold maneuver and close the window. The waveforms will freeze so you can check that plateau pressure is stable, then measure pressure at the end of the plateau using the cursor.

Screenshot ventilator display showing end-inspiratory hold in ASV mode — End-inspiratory hold in ASV mode

End-expiratory hold

End-expiratory hold: As for end-inspiratory hold, but select Exp hold. Check that plateau pressure is stable, then measure pressure at the end of the plateau using the cursor.

Full citations below: (Amato MB, Meade MO, Slutsky AS, et al. Driving pressure and survival in the acute respiratory distress syndrome. N Engl J Med. 2015;372(8):747-755. doi:10.1056/NEJMsa14106391, Laffey JG, Bellani G, Pham T, et al. Potentially modifiable factors contributing to outcome from acute respiratory distress syndrome: the LUNG SAFE study [published correction appears in Intensive Care Med. 2017 Nov 14;:]. Intensive Care Med. 2016;42(12):1865-1876. doi:10.1007/s00134-016-4571-52, Guérin C, Papazian L, Reignier J, et al. Effect of driving pressure on mortality in ARDS patients during lung protective mechanical ventilation in two randomized controlled trials. Crit Care. 2016;20(1):384. Published 2016 Nov 29. doi:10.1186/s13054-016-1556-23, Chiumello D, Carlesso E, Brioni M, Cressoni M. Airway driving pressure and lung stress in ARDS patients. Crit Care. 2016;20:276. Published 2016 Aug 22. doi:10.1186/s13054-016-1446-74, Baedorf Kassis E, Loring SH, Talmor D. Mortality and pulmonary mechanics in relation to respiratory system and transpulmonary driving pressures in ARDS. Intensive Care Med. 2016;42(8):1206-1213. doi:10.1007/s00134-016-4403-75, Neto AS, Hemmes SN, Barbas CS, et al. Association between driving pressure and development of postoperative pulmonary complications in patients undergoing mechanical ventilation for general anaesthesia: a meta-analysis of individual patient data [published correction appears in Lancet Respir Med. 2016 Jun;4(6):e34]. Lancet Respir Med. 2016;4(4):272-280. doi:10.1016/S2213-2600(16)00057-66)

Screenshot ventilator display showing end-expiratory hold in volume-control — End-expiratory hold in volume-control mode

Note

Bibliografia

1. Amato MB, Meade MO, Slutsky AS, et al. Driving pressure and survival in the acute respiratory distress syndrome. N Engl J Med. 2015;372(8):747-755. doi:10.1056/NEJMsa1410639
2. Laffey JG, Bellani G, Pham T, et al. Potentially modifiable factors contributing to outcome from acute respiratory distress syndrome: the LUNG SAFE study [published correction appears in Intensive Care Med. 2017 Nov 14;:]. Intensive Care Med. 2016;42(12):1865-1876. doi:10.1007/s00134-016-4571-5
3. Guérin C, Papazian L, Reignier J, et al. Effect of driving pressure on mortality in ARDS patients during lung protective mechanical ventilation in two randomized controlled trials. Crit Care. 2016;20(1):384. Published 2016 Nov 29. doi:10.1186/s13054-016-1556-2
4. Chiumello D, Carlesso E, Brioni M, Cressoni M. Airway driving pressure and lung stress in ARDS patients. Crit Care. 2016;20:276. Published 2016 Aug 22. doi:10.1186/s13054-016-1446-7
5. Baedorf Kassis E, Loring SH, Talmor D. Mortality and pulmonary mechanics in relation to respiratory system and transpulmonary driving pressures in ARDS. Intensive Care Med. 2016;42(8):1206-1213. doi:10.1007/s00134-016-4403-7
6. Neto AS, Hemmes SN, Barbas CS, et al. Association between driving pressure and development of postoperative pulmonary complications in patients undergoing mechanical ventilation for general anaesthesia: a meta-analysis of individual patient data [published correction appears in Lancet Respir Med. 2016 Jun;4(6):e34]. Lancet Respir Med. 2016;4(4):272-280. doi:10.1016/S2213-2600(16)00057-6

Driving pressure and survival in the acute respiratory distress syndrome.

Amato MB, Meade MO, Slutsky AS, et al. Driving pressure and survival in the acute respiratory distress syndrome. N Engl J Med. 2015;372(8):747-755. doi:10.1056/NEJMsa1410639

Link to article

BACKGROUND

Mechanical-ventilation strategies that use lower end-inspiratory (plateau) airway pressures, lower tidal volumes (VT), and higher positive end-expiratory pressures (PEEPs) can improve survival in patients with the acute respiratory distress syndrome (ARDS), but the relative importance of each of these components is uncertain. Because respiratory-system compliance (CRS) is strongly related to the volume of aerated remaining functional lung during disease (termed functional lung size), we hypothesized that driving pressure (ΔP=VT/CRS), in which VT is intrinsically normalized to functional lung size (instead of predicted lung size in healthy persons), would be an index more strongly associated with survival than VT or PEEP in patients who are not actively breathing.

METHODS

Using a statistical tool known as multilevel mediation analysis to analyze individual data from 3562 patients with ARDS enrolled in nine previously reported randomized trials, we examined ΔP as an independent variable associated with survival. In the mediation analysis, we estimated the isolated effects of changes in ΔP resulting from randomized ventilator settings while minimizing confounding due to the baseline severity of lung disease.

RESULTS

Among ventilation variables, ΔP was most strongly associated with survival. A 1-SD increment in ΔP (approximately 7 cm of water) was associated with increased mortality (relative risk, 1.41; 95% confidence interval [CI], 1.31 to 1.51; P<0.001), even in patients receiving "protective" plateau pressures and VT (relative risk, 1.36; 95% CI, 1.17 to 1.58; P<0.001). Individual changes in VT or PEEP after randomization were not independently associated with survival; they were associated only if they were among the changes that led to reductions in ΔP (mediation effects of ΔP, P=0.004 and P=0.001, respectively).

CONCLUSIONS

We found that ΔP was the ventilation variable that best stratified risk. Decreases in ΔP owing to changes in ventilator settings were strongly associated with increased survival. (Funded by Fundação de Amparo e Pesquisa do Estado de São Paulo and others.).

Potentially modifiable factors contributing to outcome from acute respiratory distress syndrome: the LUNG SAFE study.

Laffey JG, Bellani G, Pham T, et al. Potentially modifiable factors contributing to outcome from acute respiratory distress syndrome: the LUNG SAFE study [published correction appears in Intensive Care Med. 2017 Nov 14;:]. Intensive Care Med. 2016;42(12):1865-1876. doi:10.1007/s00134-016-4571-5

Link to article

PURPOSE

To improve the outcome of the acute respiratory distress syndrome (ARDS), one needs to identify potentially modifiable factors associated with mortality.

METHODS

The large observational study to understand the global impact of severe acute respiratory failure (LUNG SAFE) was an international, multicenter, prospective cohort study of patients with severe respiratory failure, conducted in the winter of 2014 in a convenience sample of 459 ICUs from 50 countries across five continents. A pre-specified secondary aim was to examine the factors associated with outcome. Analyses were restricted to patients (93.1 %) fulfilling ARDS criteria on day 1-2 who received invasive mechanical ventilation.

RESULTS

2377 patients were included in the analysis. Potentially modifiable factors associated with increased hospital mortality in multivariable analyses include lower PEEP, higher peak inspiratory, plateau, and driving pressures, and increased respiratory rate. The impact of tidal volume on outcome was unclear. Having fewer ICU beds was also associated with higher hospital mortality. Non-modifiable factors associated with worsened outcome from ARDS included older age, active neoplasm, hematologic neoplasm, and chronic liver failure. Severity of illness indices including lower pH, lower PaO2/FiO2 ratio, and higher non-pulmonary SOFA score were associated with poorer outcome. Of the 578 (24.3 %) patients with a limitation of life-sustaining therapies or measures decision, 498 (86.0 %) died in hospital. Factors associated with increased likelihood of limitation of life-sustaining therapies or measures decision included older age, immunosuppression, neoplasia, lower pH and increased non-pulmonary SOFA scores.

CONCLUSIONS

Higher PEEP, lower peak, plateau, and driving pressures, and lower respiratory rate are associated with improved survival from ARDS.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02010073.

Effect of driving pressure on mortality in ARDS patients during lung protective mechanical ventilation in two randomized controlled trials.

Guérin C, Papazian L, Reignier J, et al. Effect of driving pressure on mortality in ARDS patients during lung protective mechanical ventilation in two randomized controlled trials. Crit Care. 2016;20(1):384. Published 2016 Nov 29. doi:10.1186/s13054-016-1556-2

Link to article

BACKGROUND

Driving pressure (ΔPrs) across the respiratory system is suggested as the strongest predictor of hospital mortality in patients with acute respiratory distress syndrome (ARDS). We wonder whether this result is related to the range of tidal volume (VT). Therefore, we investigated ΔPrs in two trials in which strict lung-protective mechanical ventilation was applied in ARDS. Our working hypothesis was that ΔPrs is a risk factor for mortality just like compliance (Crs) or plateau pressure (Pplat,rs) of the respiratory system.

METHODS

We performed secondary analysis of data from 787 ARDS patients enrolled in two independent randomized controlled trials evaluating distinct adjunctive techniques while they were ventilated as in the low VT arm of the ARDSnet trial. For this study, we used VT, positive end-expiratory pressure (PEEP), Pplat,rs, Crs, ΔPrs, and respiratory rate recorded 24 hours after randomization, and compared them between survivors and nonsurvivors at day 90. Patients were followed for 90 days after inclusion. Cox proportional hazard modeling was used for mortality at day 90. If colinearity between ΔPrs, Crs, and Pplat,rs was verified, specific Cox models were used for each of them.

RESULTS

Both trials enrolled 805 patients of whom 787 had day-1 data available, and 533 of these survived. In the univariate analysis, ΔPrs averaged 13.7 ± 3.7 and 12.8 ± 3.7 cmH2O (P = 0.002) in nonsurvivors and survivors, respectively. Colinearity between ΔPrs, Crs and Pplat,rs, which was expected as these variables are mathematically coupled, was statistically significant. Hazard ratios from the Cox models for day-90 mortality were 1.05 (1.02-1.08) (P = 0.005), 1.05 (1.01-1.08) (P = 0.008) and 0.985 (0.972-0.985) (P = 0.029) for ΔPrs, Pplat,rs and Crs, respectively. PEEP and VT were not associated with death in any model.

CONCLUSIONS

When ventilating patients with low VT, ΔPrs is a risk factor for death in ARDS patients, as is Pplat,rs or Crs. As our data originated from trials from which most ARDS patients were excluded due to strict inclusion and exclusion criteria, these findings must be validated in independent observational studies in patients ventilated with a lung protective strategy.

TRIAL REGISTRATION

Clinicaltrials.gov NCT00299650 . Registered 6 March 2006 for the Acurasys trial. Clinicaltrials.gov NCT00527813 . Registered 10 September 2007 for the Proseva trial.

Airway driving pressure and lung stress in ARDS patients.

Chiumello D, Carlesso E, Brioni M, Cressoni M. Airway driving pressure and lung stress in ARDS patients. Crit Care. 2016;20:276. Published 2016 Aug 22. doi:10.1186/s13054-016-1446-7

Link to article

BACKGROUND

Lung-protective ventilation strategy suggests the use of low tidal volume, depending on ideal body weight, and adequate levels of PEEP. However, reducing tidal volume according to ideal body weight does not always prevent overstress and overstrain. On the contrary, titrating mechanical ventilation on airway driving pressure, computed as airway pressure changes from PEEP to end-inspiratory plateau pressure, equivalent to the ratio between the tidal volume and compliance of respiratory system, should better reflect lung injury. However, possible changes in chest wall elastance could affect the reliability of airway driving pressure. The aim of this study was to evaluate if airway driving pressure could accurately predict lung stress (the pressure generated into the lung due to PEEP and tidal volume).

METHODS

One hundred and fifty ARDS patients were enrolled. At 5 and 15 cmH2O of PEEP, lung stress, driving pressure, lung and chest wall elastance were measured.

RESULTS

The applied tidal volume (mL/kg of ideal body weight) was not related to lung gas volume (r (2) = 0.0005 p = 0.772). Patients were divided according to an airway driving pressure lower and equal/higher than 15 cmH2O (the lower and higher airway driving pressure groups). At both PEEP levels, the higher airway driving pressure group had a significantly higher lung stress, respiratory system and lung elastance compared to the lower airway driving pressure group. Airway driving pressure was significantly related to lung stress (r (2) = 0.581 p < 0.0001 and r (2) = 0.353 p < 0.0001 at 5 and 15 cmH2O of PEEP). For a lung stress of 24 and 26 cmH2O, the optimal cutoff value for the airway driving pressure were 15.0 cmH2O (ROC AUC 0.85, 95 % CI = 0.782-0.922); and 16.7 (ROC AUC 0.84, 95 % CI = 0.742-0.936).

CONCLUSIONS

Airway driving pressure can detect lung overstress with an acceptable accuracy. However, further studies are needed to establish if these limits could be used for ventilator settings.

Mortality and pulmonary mechanics in relation to respiratory system and transpulmonary driving pressures in ARDS.

Baedorf Kassis E, Loring SH, Talmor D. Mortality and pulmonary mechanics in relation to respiratory system and transpulmonary driving pressures in ARDS. Intensive Care Med. 2016;42(8):1206-1213. doi:10.1007/s00134-016-4403-7

Link to article

PURPOSE

The driving pressure of the respiratory system has been shown to strongly correlate with mortality in a recent large retrospective ARDSnet study. Respiratory system driving pressure [plateau pressure-positive end-expiratory pressure (PEEP)] does not account for variable chest wall compliance. Esophageal manometry can be utilized to determine transpulmonary driving pressure. We have examined the relationships between respiratory system and transpulmonary driving pressure, pulmonary mechanics and 28-day mortality.

METHODS

Fifty-six patients from a previous study were analyzed to compare PEEP titration to maintain positive transpulmonary end-expiratory pressure to a control protocol. Respiratory system and transpulmonary driving pressures and pulmonary mechanics were examined at baseline, 5 min and 24 h. Analysis of variance and linear regression were used to compare 28 day survivors versus non-survivors and the intervention group versus the control group, respectively.

RESULTS

At baseline and 5 min there was no difference in respiratory system or transpulmonary driving pressure. By 24 h, survivors had lower respiratory system and transpulmonary driving pressures. Similarly, by 24 h the intervention group had lower transpulmonary driving pressure. This decrease was explained by improved elastance and increased PEEP.

CONCLUSIONS

The results suggest that utilizing PEEP titration to target positive transpulmonary pressure via esophageal manometry causes both improved elastance and driving pressures. Treatment strategies leading to decreased respiratory system and transpulmonary driving pressure at 24 h may be associated with improved 28 day mortality. Studies to clarify the role of respiratory system and transpulmonary driving pressures as a prognosticator and bedside ventilator target are warranted.

Association between driving pressure and development of postoperative pulmonary complications in patients undergoing mechanical ventilation for general anaesthesia: a meta-analysis of individual patient data.

Neto AS, Hemmes SN, Barbas CS, et al. Association between driving pressure and development of postoperative pulmonary complications in patients undergoing mechanical ventilation for general anaesthesia: a meta-analysis of individual patient data [published correction appears in Lancet Respir Med. 2016 Jun;4(6):e34]. Lancet Respir Med. 2016;4(4):272-280. doi:10.1016/S2213-2600(16)00057-6

Link to article

BACKGROUND

Protective mechanical ventilation strategies using low tidal volume or high levels of positive end-expiratory pressure (PEEP) improve outcomes for patients who have had surgery. The role of the driving pressure, which is the difference between the plateau pressure and the level of positive end-expiratory pressure is not known. We investigated the association of tidal volume, the level of PEEP, and driving pressure during intraoperative ventilation with the development of postoperative pulmonary complications.

METHODS

We did a meta-analysis of individual patient data from randomised controlled trials of protective ventilation during general anesthaesia for surgery published up to July 30, 2015. The main outcome was development of postoperative pulmonary complications (postoperative lung injury, pulmonary infection, or barotrauma).

FINDINGS

We included data from 17 randomised controlled trials, including 2250 patients. Multivariate analysis suggested that driving pressure was associated with the development of postoperative pulmonary complications (odds ratio [OR] for one unit increase of driving pressure 1·16, 95% CI 1·13-1·19; p<0·0001), whereas we detected no association for tidal volume (1·05, 0·98-1·13; p=0·179). PEEP did not have a large enough effect in univariate analysis to warrant inclusion in the multivariate analysis. In a mediator analysis, driving pressure was the only significant mediator of the effects of protective ventilation on development of pulmonary complications (p=0·027). In two studies that compared low with high PEEP during low tidal volume ventilation, an increase in the level of PEEP that resulted in an increase in driving pressure was associated with more postoperative pulmonary complications (OR 3·11, 95% CI 1·39-6·96; p=0·006).

INTERPRETATION

In patients having surgery, intraoperative high driving pressure and changes in the level of PEEP that result in an increase of driving pressure are associated with more postoperative pulmonary complications. However, a randomised controlled trial comparing ventilation based on driving pressure with usual care is needed to confirm these findings.

FUNDING

None.