SCCM Resource Library-Peak & Driving Pressures Stratify Respiratory Failure Severity in Cyanotic Congenital Heart Disease

Video Transcription

Good morning, everyone. My name is Ugi Ver, and I am one of the hospital's physicians in the PICU at the Children's Hospital of Philadelphia.  I'm thrilled to be here today, and I first want to thank SCCM for providing this platform to be able to share some of our work that we've done over the past year.  The title of my talk today is Peak and Driving Pressures Stratify Respiratory Failure Severity in Cyanotic Congenital Heart Disease.  And I was able to do some of this work with Dr. Dewitt, who is in the CHOP CICU, Dr. Thomas,  who's from the Penn State College of Medicine in the PICU, and my research mentor, Dr. Yeya, who is a PICU attending at CHOP.  Acute respiratory failure is the most common cause of death for children admitted to PICUs.  Pediatric acute respiratory distress syndrome, or PARDS, is a severe form of acute respiratory  failure characterized by acute hypoxemic respiratory failure from non-cardiogenic pulmonary edema.  Historically, the characterization of PARDS was based on adult definitions, determined as recently as 2012 with the Berlin definition.  But recognizing that ARDS in children is different than in adults, the Pediatric Acute Lung Injury  Consensus Conference, or PALICC, was convened in 2015 to establish new definitions and guidelines for PARDS.  Among key differences with the PALICC definition is the utilization of the OI and the OSI,  rather than the PF ratio, to assess hypoxemia and stratify severity groups into mild, moderate,  and severe, with PALICC specifically recommending the development of prognostic scores to stratify mortality.  There is a significant stepwise increase in mortality with increasing disease severity, with 10% to 15% for mild or moderate disease versus about 30% for severe.  Since then, multiple studies, including the recent PROSPECTIVE-PARTY study, comparing the new PALICC criteria to prior definitions, including Berlin, showed that the new PALICC  definition identified a threefold increase in cases of children as having ARDS, and diagnosed ARDS sooner than the Berlin definition, with improved mortality discrimination.  For patients with cyanotic congenital heart disease, PALICC recommended that they are considered to have PARDS if they fulfill standard criteria, including having an acute onset,  a known clinical insult, and chest imaging supporting new onset pulmonary parenchymal disease, as well as having an acute deterioration in their oxygenation not explained by the  underlying cardiac disease. However, due to the difficulties in ascribing the contribution to hypoxemia from acute lung  disease versus the presence of a cyanotic heart lesion, per the PALICC criteria, we are unable to use OI or OSI risk categories for stratification of disease severity in  this patient population, which is a group with a particularly high risk of developing acute respiratory failure, with significant morbidity and mortality as a result.  Therefore, the aim of our study was to determine whether variables related to respiratory mechanics,  independent of indices of oxygenation, could assist in stratifying acute respiratory failure severity in patients with cyanotic congenital heart disease.  Our study was a retrospective analysis of a cohort of patients admitted to the Cardiac Intensive Care Unit at CHOP between July 1, 2011, and June 30, 2019.  Patients were included if they were term-born infants born between 37 and 42 weeks gestation, as well as all children less than 18 years old.  Patients born with cyanotic congenital heart disease with acute onset of respiratory failure requiring invasive mechanical ventilation for 72 or more hours, with finding of new  pulmonary infiltrates on chest imaging at the onset of acute respiratory failure, and with an average FiO2 requirement of greater than 30% over the first 24 hours of mechanical  ventilation. Patients with a prior history of lung transplant, orthotic heart transplant, or ventricular  assist device, and those that were intubated at an outside facility prior to transfer to CHOP were excluded, as well as those patients who died within 72 hours of acute respiratory  failure onset, defined as a time of initiation of mechanical ventilation. We included patients with a history of long-term artificial airway if they were admitted on  increased ventilator support from baseline for more than 72 hours. Using these inclusion criteria, a total of 344 patients with acute respiratory failure  were admitted to the CICU during this study period. Then, demographics, cardiac history, cause of acute respiratory failure, duration of  mechanical ventilation, and time-matched ventilator settings and oxygenation data at acute respiratory  failure onset at the 12-hour mark and at 24 hours were then recorded retrospectively. Ventilator settings included PEEP, PIP, driving pressure, or PIP minus PEEP, tidal volume,  dynamic compliance, or tidal volume over delta P, and mean airway pressure. Oxygenation data included FiO2, oxygenation saturation, and tidal CO2 and blood gas data.  Our primary outcome was CICU mortality at 28 days. Our secondary outcome was VFDs, or ventilator-free days, at 28 days and ventilator days in survivors.  Any mention of ventilation refers to invasive mechanical ventilation, as we did not count non-invasive support toward VFDs or total ventilator days.  We define successful extubation as more than 48 hours of successful ventilator-free days or a return to baseline respiratory support if the patient has a history of long-term  artificial airway. If a patient required reintubation after being successfully extubated, we created a new subject encounter for the purposes of this study moving forward.  We initially screened all respiratory metrics and oxygenation data for association with our primary outcome of mortality using lowest smoothing, which was able to help us determine  if a relationship existed between the variables and warranted further analyses. We subsequently analyzed those variables of interest that emerged with logistic regression  for our primary outcome of CICU mortality and competing risk regression for our secondary outcome of VFDs at 28 days.  We then performed repeat analyses after adjusting for age in months, RAC1 scores, and average FIO2 over the first 24 hours of mechanical ventilation.  As noted previously, there were 344 patients admitted to the CICU who required invasive mechanical ventilation during our study period who met our inclusion criteria.  And the notable patient characteristics are depicted here. We utilize RAC1 scores as a marker of complexity of congenital heart disease, with the majority  of our patient population having a RAC score of 3 to 4. As expected, due to the nature of cyanotic congenital heart disease, the majority of  our patient population were less than one year old, with 49% under the age of 30 days. But importantly, again, similar to Palik's recommendation, that exclusion criteria for  PARDS should include causes of acute hypoxemia unique to the perinatal period, such as prematurity-related lung disease, perinatal lung injury, or other congenital abnormalities.  We only included term-born infants born between 37 and 42 weeks gestation. And finally, but importantly, 2 thirds of our cohort of patients that required invasive  mechanical ventilation were due to the result of a cardiopulmonary bypass, which we defined here as patients undergoing cardiac surgery requiring bypass or the need for ECMO.  The most common causes of acute respiratory failure due to non-cardiopulmonary bypass include an infectious pneumonia and non-pulmonary sepsis, which aligns with known causes of  PARDS. Using screening lowest graphs, we were able to demonstrate that PIP and delta-P showed  the most significant relationship with our primary outcome of CICU mortality at 28 days. On further analysis, average PIP and delta-P were each significantly associated both with  mortality with an unadjusted odds ratio of 1.12 and 1.14, respectively, as well as a lower probability of excavation as measured by VFDs with a sub-hazard ratio of 0.95 and  0.96 for PIP and delta-P, respectively. This association remained true for both PIP and delta-P with mortality and VFDs adjusting  for age, severity of cardiac lesion, and average FiO2. Our next goal was to see if we could create a stratification system for acute respiratory  failure for this patient population using both PIP and delta-P. Using spleen graphs, we were able to determine cutoffs for both PIP and delta-P to create  a three-level severity stratification scheme using mild, moderate, and severe. For PIP, we define mild disease as PIPs less than or equal to 20, moderate 21 to 29, and  severe greater than 29. For delta-P, mild disease assessed as delta-P less than or equal to 16, moderate 17 to 24, and severe greater than 24.  Graphically, this figure represents our whole patient cohort. You can clearly see an increase in mortality with an increasing severity of disease stratification  for both PIP and delta-P, as well as a lower probability of extubation as represented by either decreasing VFDs for both PIP and delta-P as you move from mild to moderate to severe  disease, or by an increase in number of ventilator days in survivors, again, for both PIP and delta-P as you go from mild to moderate to severe disease.  As noted before, we further analyze our patient cohort depending on their initial cause of acute respiratory failure, with 2 thirds of our patients requiring invasive mechanical  ventilation as a result of cardiopulmonary bypass. The stratification system of disease severity, broken down for both PIP and delta-P when  looking only at those patients requiring bypass, continues to hold true with increasing mortality  from mild to moderate to severe disease in both PIP and delta-P, decreasing VFDs and increasing ventilator days in survivors also when going from mild to moderate to severe  disease in both PIP and delta-P. When looking at patients suffering from acute respiratory failure for causes other than  cardiopulmonary bypass, this trend does continue, especially when looking at VFDs and ventilator days in survivors.  When looking at mortality specifically, the effect is more pronounced between the mild and moderate severity categories and the severe category, both for PIP and delta-P, something  that may need to be explored further. So our initial overall goal was to determine whether there were variables related to respiratory  mechanics that were independent of indices of oxygenation that could assist us in coming up with a stratification system for acute respiratory failure severity in patients  with cyanotic congenital heart disease. Doing that, we were first able to demonstrate that PIP and delta-P were associated with mortality and VFDs in this patient population.  And second, we were able to come up with a stratification scheme using PIP and delta-P to assess severity of acute respiratory failure in a very particular patient population who  was acute on chronic deoxygenation from baseline as multifactorial. So with these types of gains in risk stratification, along with an improved understanding of epidemiology  and heterogeneity of a disease process that continues to have significant morbidity and mortality, it will allow us in the future to come up with better targeted management  to ultimately improve outcomes and further reduce the mortality burden. While our study did provide meaningful results, it did have some limitations.  First, this was a retrospective single-center study, which may affect the generalizability of our findings.  Next, mortality overall was low in our patient cohort, which aligns with known outcomes in PARDS, but does make it a problematic endpoint for stratification.  And finally, the public definition of PARDS is characterized by acute respiratory failure from non-cardiogenic pulmonary edema.  And we did not review echoes to ensure that patient's acute deterioration in oxygenation was not explained by their underlying cardiac disease.  All other criteria for PARDS, per the public definition, were met. Overall, I want to thank everyone again for tuning into this virtual presentation.  I want to thank SCCM for giving me the platform to be able to present this research. And importantly, to my collaborators, Drs. Dewitt and Thomas, and especially a huge thank  you to Dr. Yeya for all of his teaching and mentorship over the years. I'm very grateful. Thank you, everyone.

Video Summary

Dr. Ugi Ver from the Children's Hospital of Philadelphia discusses the severity of respiratory failure in children with cyanotic congenital heart disease. The Pediatric Acute Lung Injury Consensus Conference (PALICC) established new definitions and guidelines for pediatric acute respiratory distress syndrome (PARDS) in 2015. However, these guidelines do not provide a stratification of disease severity for patients with cyanotic congenital heart disease. Dr. Ver's study aimed to determine if variables related to respiratory mechanics could be used to stratify the severity of respiratory failure in this patient population. The study found that peak inspiratory pressure (PIP) and driving pressure (delta-P) were associated with mortality and ventilator-free days. A three-level severity stratification scheme was developed based on PIP and delta-P values. This research will help improve the management and outcomes of respiratory failure in children with cyanotic congenital heart disease.

Asset Subtitle

Pulmonary, Cardiovascular, Pediatrics, 2022

Asset Caption

INTRODUCTION: Intensive care unit (ICU) clinicians rely on hypoxemia to stratify the severity of acute respiratory failure (ARF), including in pediatric acute respiratory distress syndrome (PARDS). PARDS is stratified based on hypoxemia as mild, moderate, and severe, with better oxygenation associated with lower mortality. However, hypoxemia caused by intracardiac mixing or right-to-left shunting in patients with cyanotic congenital heart disease (CCHD) decreases oxygenation in the absence of lung disease. We aimed to determine whether variables related to respiratory mechanics were associated with mortality and ventilator-free days (VFDs) to assist with stratifying ARF severity in pediatric CCHD. METHODS: We performed a retrospective cohort study of children with CCHD admitted to the cardiac ICU at the Children’s Hospital of Philadelphia with ARF (intubated with FIO2 ≥ 0.3 and new infiltrates) ventilated for ≥ 72 hours. Demographics and cardiac history were recorded, and respiratory metrics and oxygenation data were averaged at ARF onset, 12 hours, and 24 hours. We tested for association between markers of ventilator mechanics and both 28-day mortality and VFDs at 28 days using logistic and competing risk regression, respectively. RESULTS: Between 2011 and 2019, 344 patients were eligible, of whom 226 (66%) had ARF due to cardiopulmonary bypass. Respiratory metrics and oxygenation data were screened for univariate association with mortality. Average peak inspiratory pressure (PIP) and driving pressure (ΔP = PIP minus PEEP) were both associated with higher mortality and lower probability of extubation. PIP and ΔP remained associated with mortality (PIP: odds ratio [OR] 1.10, 95%CI 1.02-1.19, p=0.020; ΔP: OR 1.11, 95%CI 1.01-1.21, p=0.017) and VFDs (PIP: subdistribution hazard ratio [SHR] 0.95, 95%CI 0.93-0.98, p < 0.001; ΔP: SHR 0.96, 95%CI 0.93-0.99, p=0.006) after adjusting for age, severity of cardiac lesion and FIO2. PIP and ΔP showed increasing mortality and decreasing VFDs across a three-level (mild, moderate, severe) severity stratification scheme (PIP: mild ≤20, moderate 21-29, severe ≥29; ΔP: mild ≤16, moderate 17-24, severe ≥24). CONCLUSIONS: PIP and ΔP were associated with mortality and VFDs in pediatric CCHD and may be useful to stratify ARF severity in a population whose deoxygenation is multifactorial.

Meta Tag

Content Type Presentation

Knowledge Area Pulmonary

Knowledge Area Cardiovascular

Knowledge Area Pediatrics

Knowledge Level Advanced

Membership Level Select

Tag Acute Respiratory Distress Syndrome ARDS

Tag Pediatrics

Tag Congenital Heart Disease

Tag Cardiothoracic Critical Care

Year 2022

Keywords

respiratory failure

cyanotic congenital heart disease

Pediatric Acute Lung Injury Consensus Conference

pediatric acute respiratory distress syndrome

severity stratification

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