SCCM Resource Library-Agreement Between Peak Inspiratory Pressure in Decelerating-Flow Ventilation and Plateau Pressure in Square-Flow Ventilation in Pediatric ARDS

Video Transcription

Good morning, everyone. My name is Bhavesh Patel. I'm the Chief Resident for the Internal Medicine and Pediatric Residency Program at the University  of Pennsylvania and the Children's Hospital of Philadelphia. Next year, I'll be joining the Children's Hospital of Philadelphia's Pediatric Critical Care Medicine Fellowship.  Today I'll be chatting with you all about a study that Drs. Yeye, Thomas, and I carried out titled, Agreement Between Peak Inspiratory Pressure and Decelerating  Flow Ventilation and Plateau Pressure and Square Flow Ventilation in Pediatric ARDS. As many of us know, the ARDSNet protocol recommends a plateau pressure of less than  30 in adults with ARDS because it improves mortality. In 2015, Patlick recommended a plateau pressure of less than 28.  The theory behind this is that plateau pressure is a good surrogate for lung stress. Therefore, the monitoring of plateau pressure is a key tenet of lung protective ventilation.  However, pediatric providers most often use pressure-regulated volume control or pressure control ventilation rather than the square flow volume control ventilation most commonly  used in adult ARDS. Here's an example of flow and decelerating flow ventilation and flow and square flow ventilation.  In a multicenter pediatric ARDS cohort, 65% of patients were on pressure control or pressure-regulated volume control ventilation.  The issue with that is that plateau pressure is less reliably measured in decelerating flow ventilation and is therefore often substituted with the peak inspiratory pressure or PIP.  In the same cohort, plateau pressure was reported in only 2.9% of measurements, suggesting that those providers relied on PIPs.  However, there's concern that the resistive components of ventilation may make PIP an unreliable surrogate for lung stress and it may overestimate the plateau pressure.  But the degree to which PIP overestimates plateau pressure has not been quantified in adults or children.  Therefore, we aim to assess the correlation and accuracy of PIP during decelerating flow ventilation or PIP decel for approximating plateau pressure in pediatric ARDS.  Our hypothesis was that PIP decel would approximate plateau pressure and square flow ventilation within 0.5 centimeters of water.  Our study was a prospective observational study carried out from January 2020 to May 2021. Our inclusion criteria included components of both the Berlin definition of ARDS and  the Pallack definition of pediatric ARDS. Specifically, our inclusion criteria were acute respiratory failure requiring invasive  ventilation, age greater than one month without an upper limit, oxygenation index greater  than or equal to four, or oxygenation saturation index greater than equal to five on two consecutive  measurements greater than or equal to four hours apart, and bilateral parenchymal infiltrates on radiography.  Our exclusion criteria were respiratory failure primarily from cardiac failure, exacerbation  of underlying chronic respiratory disease, chronic ventilator dependence, mixing cyanotic  heart disease, ventilation for greater than or equal to seven days before meeting eligibility, and finally, pediatric ARDS established outside of our institution.  Our institutional practice is to initiate conventional ventilation in a decelerating flow mode, whether that's pressure regulated volume control or pressure control ventilation  with a peak greater than or equal to five centimeters of water, with age appropriate cuffed endotracheal tubes, and active humidification.  We try to ensure that our inspiratory and expiratory flows approach zero as seen in this figure here.  Persistently elevated PIPs, ongoing hypercarbia, and oxygenation difficulties prompt consideration for changing ventilation mode or escalating to extracorporeal support.  We recorded decelerating flow settings within 24 hours of pediatric ARDS onset. We verified quiet breathing by ensuring measurements during paralysis or when there was no  respiratory effort. We recorded PIP decel without adjustment of the set inspiratory time. We then switched the patient to square flow volume control ventilation using the excelled  tallidal volume from the previous settings and allowed 30 to 60 seconds of ventilation. We then recorded the plateau pressure after about half a second of an inspiratory pause.  We chose to switch to square flow ventilation rather than performing an inspiratory pause  in decelerating flow because this represents the gold standard for measuring plateau pressure  and because inconsistent tidal volumes and pressure-regulated volume control make plateau pressure in that mode unreliable.  We identified a total of 56 subjects, of which 4 were on non-conventional modes of ventilation and did not have pressure supported, therefore we ultimately included 52.  There were 8 non-survivors at day 28, resulting in a 15% 28-day mortality. Most of our cohort had pediatric ARDS due to pneumonia in 54%, and non-pulmonary sepsis in 15%.  Overall, the severity of pediatric ARDS in our cohort was moderate, with a median OI of 15.7 and a median P to F ratio of 124.  Most of our cohort was on pressure-regulated volume control ventilation with 79%, and 21% were on pressure control ventilation.  PIP decel ranged from 20 to 42 centimeters of water, and inspiratory time ranged from 0.4 to 1.3 seconds.  As you can see here, plateau pressure and PIP decel were strongly correlated. And Bland-Altman analysis revealed that PIP decel was greater than plateau pressure by  a mean of 1 ± 0.6 centimeters of water. And PIP decel exceeded plateau pressure by less than 2 centimeters of water in 50 of our patients, or 96% of our cohort.  One patient was outside the limits of agreement, and they had coexistent asthma with inspiratory flow prematurely terminated prior to reaching zero.  And only one patient had plateau pressure greater than PIP decel. So PIP decel slightly overestimates plateau pressure in pediatric ARDS, but it may be  a reasonable approximation, particularly when inspiratory flow approaches zero, when there's not significant obstructive disease, when PIPs are between 20 and 40 centimeters of  water, with age-appropriate inspiratory times between 0.4 and 1.3 seconds. Therefore, PIP decel measured during quiet breathing may indeed be a reasonable surrogate  for plateau pressure, again, provided that inspiratory flow approaches zero, and may be used clinically to approximate the plateau pressure and calculate a driving pressure.  Should be noted that providers should be cognizant that PIPs may not be much higher than plateau pressure. Our study had its limitations, as all studies do.  First, it was a single-center study, which may limit generalizability to other populations.  Next, there are only seven patients less than 12 months of age, which may limit the generalizability to younger patients.  And finally, it applies only to pediatric ARDS, and specifically, it is not applicable to processes where resistance may be elevated, such as obstructive conditions.  Thank you so much for taking the time to listen.

Video Summary

Dr. Bhavesh Patel discusses a study he conducted on the agreement between peak inspiratory pressure (PIP) and plateau pressure in pediatric ARDS (acute respiratory distress syndrome). The study found that PIP decel (during quiet breathing) slightly overestimates plateau pressure, but it can be a reasonable approximation, particularly when inspiratory flow approaches zero and there is no significant obstructive disease. It suggests that PIP decel can be used clinically to approximate plateau pressure and calculate a driving pressure. However, the study's limitations include being a single-center study and limited generalizability to other populations and younger patients. It is not applicable to obstructive conditions.

Asset Subtitle

Pulmonary, Procedures, Pediatrics, 2022

Asset Caption

INTRODUCTION: Lung-protective ventilation guidelines for acute respiratory distress syndrome (ARDS) suggest limiting plateau pressure to 30 cmH2O. Plateau pressure is most accurately measured in square-flow modes of ventilation, such as volume control. In children, decelerating-flow modes of ventilation (pressure-regulated volume control and pressure control) are more common, and plateau pressures are rarely obtained. Pressure limits are instead provided for peak inspiratory pressure (PIP). The degree to which PIP in decelerating-flow overestimates plateau pressure is unknown. Therefore, we aimed to assess the correlation and accuracy of PIP in decelerating-flow for approximating plateau pressure in square-flow ventilation. We hypothesized that PIP in decelerating-flow would approximate plateau pressure in square-flow within 0.5 cmH2O. METHODS: We carried out a prospective, observational study in a tertiary, academic pediatric intensive care unit. Fifty-two intubated children with pediatric ARDS (PARDS) were enrolled between January 2020 and May 2021. PIP in decelerating-flow ventilation and plateau pressure after transition to square-flow ventilation were measured within 24 hours of onset of PARDS. After the first 10 subjects, we calculated the standard deviation of the difference between PIP in decelerating-flow and plateau pressures in square-flow to calculate a sample size. In an equivalence test of paired means, a sample size of 45 was required for 90% power at an α of 0.05 to demonstrate a true difference (± SD) of 0 ± 1, with equivalence limits of -0.5 and 0.5. RESULTS: Of the 52 patients with PARDS, there were 8 non-survivors (17%) at day 28. Hypoxemia was consistent with moderate PARDS, with a median oxygenation index of 10.5 and PaO2/FIO2 of 177. PIP in decelerating-flow was highly correlated (r2 = 0.99, p < 0.001) with plateau pressure in square-flow. PIP was 0.98 ± 0.63 cmH2O higher than plateau pressure, with 96% of values within 2 cmH2O. Inspiratory flows approached zero in decelerating-flow in all subjects except one outlier with concurrent obstructive lung disease. CONCLUSIONS: PIP measured during decelerating-flow ventilation is an adequate surrogate of plateau pressure in PARDS. Practitioners should not be reassured that PIPs in decelerating-flow are substantially higher than plateau pressures.

Meta Tag

Content Type Presentation

Knowledge Area Pulmonary

Knowledge Area Procedures

Knowledge Area Pediatrics

Knowledge Level Intermediate

Knowledge Level Advanced

Membership Level Select

Tag Acute Respiratory Distress Syndrome ARDS

Tag Mechanical Ventilation

Tag Pediatrics

Tag Respiratory Failure

Year 2022

Keywords

Dr. Bhavesh Patel

pediatric ARDS

peak inspiratory pressure

plateau pressure

driving pressure

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