unmasking copd exacerbations

UNMASKING COPD EXACERBATIONSA Guide to Mask-Free NIV™

for COPD Patients

SUBGROUP ANALYSIS COPD PATIENTS ON

HIGH VELOCITY THERAPY

COPD PATIENTS AND WOUND CARE

IMPLICATIONS

HIGH VELOCITY THERAPY IS NON-

INFERIOR TO NIPPV

TREATING COPD PATIENTS WITH HIGH VELOCITY THERAPY

HIGH VELOCITY THERAPY USED TO

AVOID NIPPV

WHAT IS MASK-FREE NIV?

VENTILATORY SUPPORT VIA AN

OPEN SYSTEM

Copyright © 2020 Vapotherm, Inc.

All rights reserved. This book or any portion thereof may not be reproduced or used in any manner whatsoever without the express written permission of the published except for the use of brief quotations in a book review.

Vapotherm’s high velocity therapy is a tool for treating respiratory distress. Vapotherm does not practice medicine or provide medical services or advice, any clinical recommendations provided herein are solely those of the speaker. Practitioners should refer to the full indications for use and operating instructions of any products referenced before use. All contributors are employees of Vapotherm.

First eBook Edition – June 2020 MKT-0388 Rev A 06/20 Edited by Kristina Paschkopić Designed by Dylan McGuinness

Vapotherm, Inc. 100 Domain Drive Exeter, NH 03833

www.vapotherm.com

UNMASKING COPD EXACERBATIONS 1




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Contents

3What is Mask-Free NIV? by John Walsh, CRT

5Case Study: High Velocity Therapy to Avoid NiPPV and Reverse Acute Carbon Dioxide Retention in a COPD Exacerbationby Marcia Jeffers, RRT • Kale Spivey, RRT-NPS • Terrell Ashe, RRT-NPS • Sheldon Spivey, RRT • Rose Dennis, RRT

7Treating COPD Patients with Vapotherm High Velocity Therapy by Kirk Hinkley, MD, FACEP

10What Does it Mean Vapotherm High Velocity Therapy is Noninferior to NiPPV?by George Dungan, II MPhil

16COPD Patients on Vapotherm High Velocity Therapy - Ventilatory Support, Intubations, and Length of Stay Implications from a Subgroup Analysisby Leo Volakis, PhD

20COPD Patients and Wound Care Implications with Vapotherm High Velocity Therapyby Jeanne Pettinichi, MSN, RN, CPN, CPEN

23Ventilatory Support via an Open System - How Does it Work?by Amrit Kahlon, MD




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cannula on the woman’s face. It looked like just a regular oxygen cannula and I remember hoping that it would buy us at least a bitof time as the doctor was getting ready to intubate because there was no way this was going to work. The patient’s work of breathing began to improve almost immediately. About half an hour later, she was fully stabilized and it was clear she wouldn’t need an intubation. I picked up the phone and called up the rep who’d asked us to try the device and I remember saying, “I don’t think you understand what you’ve got here.” I’m not kidding when I say that for a few years back then, we used to call it the “magic box.” We didn’t understand how it worked. Just that it worked. It worked on pretty much all kinds of spontaneously breathing patients in respiratory distress. It worked on COPDers, on folks

A couple of decades ago, the mother of the CFO of the hospital where I worked was brought into the Emergency Department with a COPD exacerbation. I was one of the respiratory therapists who had treated her before and we all knew that she absolutely did not want to be put on a pressure-based respiratory support modality. She had been so anxious with it last time that it had worsened her respiratory rate on top of the underlying exacerbation. Because of her medical history and age, we were also hesitant to intubate her and so we agreed to give it a try with this Vapotherm device we’d recently learned about. It delivered high liter flows of humidified gas through a simple nasal cannula. None of us had ever used it before on a hypercapnic patient, but we’d been trained to set it up, so we quickly slipped a nasal cannula on the woman’s face.


What is Mask-Free NIV™?By John Walsh, CRTJohn Walsh is a Respiratory Therapist and currently holds the position of Area Vice President with Vapotherm. Prior to this, he utilized high velocity therapy on adult patients in the Emergency Department. He has been with Vapotherm for 19 years and in that time has helped hospitals all over the world on implementing and utilizing this therapy.

having respiratory symptoms from CHF. Closest to home for me was that it worked on preemie babies and my wife and I got to see our son’s face and hold him skin to skin when he was in the NICU, born premature.

John Walsh holding son Jonathan while visiting baby Alex in the NICU.




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flow products are included (BTT) is the same one that also includes respiratory humidifiers. The one where the Vapotherm Precision Flow Hi-VNI™ belongs (QAV) has indications that are similar to those of noninvasive positive pressure ventilation (NiPPV). As I write this, the Precision Flow Hi-VNI, which is a product that delivers Vapotherm therapy, is also the only product in that QAV category. The FDA created this new category based on a substantial body of evidence showing what Vapotherm therapy could do. As for me, like I said, I was a believer in what it could do long before these studies were even conducted because I saw what it could do. It took me a few COPD patients before I became convinced that this mask-free modality could tackle hypercapnia, but I was soon glad I had it as an option in my toolkit. As all of us who work with respiratory patients know, some patients are very much like my former CFO’s mother and just have a very hard time tolerating pressure-based masks. About a third of all NiPPV failure happens due to the patients’ mask-intolerance.1 COPD is the third leading cause

Now we of course know how it works and now I call it Vapotherm high velocity therapy or Mask-Free NIV™ for spontaneously breathing patients. Although this technology has been spreading across the country and world, I still get some double-takes from medical professionals who aren’t familiar with the therapy when they hear mask-free NIV. The conventional wisdom of course tells us that you need pressure to be able to achieve ventilatory support. But Mask-Free NIV is an open system capable of providing ventilatory support and treating respiratory distress in hypercapnic patients. Inevitably the second double-take I sometimes get goes like this: “If it’s an open system that delivers liter flows, isn’t it just high flow cannula?” The very quick answer to that is no, Vapotherm therapy is mechanistically different. You can also think of it as high velocity therapy. Because they are quite different, the US Food and Drug Administration (FDA) actually distinguishes between high flow and high velocity products. To give you a better sense, the product category where high

of death in the U.S.2 As our population ages and COPD continues to rise,3 we might be seeing more and more cases in our emergency departments and hospitals. The articles written by my colleagues in this book will go in depth on how Vapotherm therapy works and will review the studies showing the effects of this first major innovation in NIV in the last 30 years. It’s my hope that by understanding all tools available to you, it will help you provide even better care to your patients.


References1. Carron M. et al. Complications of non-invasive ventilation techniques: a comprehensive qualitative review of randomized trials. British Journal of Anaesthesia. 110(6):896-914. (2013) https://www.ncbi.nlm.nih.gov/pubmed/235629342. Basics about COPD. Centers for Disease Control and Prevention. Last accessed: March 10, 2020. https://www.cdc.gov/copd/basics-about.html3. Chronic obstructive pulmonary disease (COPD). World Health Organization. December 1, 2017. Last accessed: March 10, 2020. https://www.who.int/news-room/fact-sheets/detail/chronic-obstructive-pulmonary-disease-(copd)




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Case Study: High Velocity Nasal Insufflation (Vapotherm High Velocity Therapy) Used to Avoid NiPPV and Reverse Acute Carbon Dioxide Retention in a COPD ExacerbationBy Marcia Jeffers, RRT • Kale Spivey, RRT-NPS • Terrell Ashe, RRT-NPS • Sheldon Spivey, RRT • Rose Dennis, RRT

This patient is well known to our staff with multiple prior admissions. Eighteen days prior, this patient presented with a similar exacerbation, wherein she was intubated and admitted to the ICU with a three day length of stay. Based on history, it was anticipated that this patient would be intubated and admitted to the ICU.Treatment and Response Non-invasive positive pressure ventilation was ordered but never initiated; Vapotherm high velocity therapy

Patient History and Presentation A 60 year-old female with a history of end-stage COPD, having been intubated within the last month for a similar exacerbation, arrived by ambulance to our Emergency Department. The chief complaint was severe difficulty breathing which came on gradually. Initial assessment noted tachypnea with nasal flaring and purse-lipped breathing, as well as bilateral wheezing and wet cough.

was started (Precision Flow, Vapotherm, Exeter, NH: Adult cannula with 4.8mm O.D.) at 25 L/min with a 60% oxygen blend and the patient immediately and markedly began to improve. Arterial blood gas analyses (ABGs) were made immediately after the initiation of high velocity therapy and again 44 minutes thereafter; data are reported below. Following the initiation of high velocity therapy, respiratory rate dropped precipitously and the patient

Athens Regional Medical Center (Athens, Georgia)




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ventilation work was seen as a reduced respiratory rate. This reduced work of breathing likely averted respiratory muscle fatigue.Conclusions The application of high velocity therapy resulted in rapid improvement that is believed to have averted the use of mechanical ventilation and ICU admission. Note that this patient returned twelve days later with an identical presentation, and was again successfully treated with high velocity therapy.

demonstrated a reduction in dyspnea. In the time between ABGs, and despite the drop in respiratory rate, PaCO2 was reduced and pH increased markedly. Arterial oxygen tension dropped in conjunction with the decrease in respiratory rate, but hemoglobin oxygen saturation was maintained. The patient was admitted to the medical floor and discharged the following day.Interpretation In conjunction with the mechanistic evidence that high velocity therapy provides ventilatory support by way of dead space purge, HVNI resulted in a reduced minute ventilation by way of a reduction in respiratory rate. The blow-off of CO2 from the anatomical dead space improved arterial CO2, and corresponding pH, despite the drop in respiratory rate. The improvement in pH stabilized hemoglobin saturation in the face of a reduced arterial oxygen tension (Bohr effect) that was associated with the drop in minute ventilation. The arterial CO2 was reduced to 53 mmHg, which is normal for a compensated COPD patient (HCO3– = 33 mEq/L), and so much of the

The applications of high velocity therapy resulted in rapid improvement that is believed to have averted the use of mechanical ventilation and ICU admission.




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tripoding, and tachypneic with pursed-lip breathing. It was pretty clear that he was having yet another COPD exacerbation. EMS started CPAP and with his symptoms it was clear he really needed an advanced respiratory modality. I knew the patient had been on pressure-based bi-level PAP before and had some issues tolerating the mask, so I figured this might be a good test case. I asked him whether he’d be willing to give high velocity therapy a go and he nodded and gave the thumbs up since he couldn’t speak much through the mask. Now I had just been told that Vapotherm high velocity therapy could manage symptoms of acute hypercapnia but being told something

When I was first introduced to Vapotherm high velocity therapy several years ago it took me only a few hours to realize that this was a great new way to care for patients. It is a super user-friendly device with just three buttons – but the biggest controls all of the therapy. As I like to say, it’s so simple even an ER doc can run it. When my respiratory director asked me if I’d like to kick the tires on this new device and see how it worked, I agreed. I’d just walked in for a night shift and was given 10 minutes of training and soon after that, hooked up my first patient. This patient came in by ambulance, a gentleman I was quite familiar with. He had a history of COPD and was

Treating COPD Patients with Vapotherm High Velocity Therapy — My Experience as an Emergency Department Physician

By Kirk Hinkley, MD, FACEPDr. Hinkley has been a board-certified Emergency Medicine Physician for over 11 years. He is the Emergency Medicine Medical Director of Commonwealth Health EMS, where he maintains clinical oversight of several EMS units, and he practices as an Emergency Physician in Scranton, PA. Dr. Hinkley is also the Director of Emergency Department Education at Vapotherm. He went to medical school on a United States Air Force Scholarship and served in Operations Iraqi Freedom and Enduring Freedom as a critical care air transport team leader and flight surgeon. Dr. Hinkley is an experienced user of HVNI.

and seeing it are always two different things. I remember the surprise of watching this man turn around so quickly without ever needing to go back on the mask. In only 10-15 minutes he had stabilized. I had been standing by, ready to switch him to positive pressure and send him to the ICU if needed, but instead was able to admit him to the medical floor on the Vapotherm cannula. That experience made life in the ER much simpler, as we no longer needed to board so many respiratory failure patients bound for the ICU. Over the next several days, my partners and I tried it successfully on many spontaneously breathing patients to evaluate just what its range of efficacy was.




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My Approach and the Settings I Use What I like about Vapotherm high velocity therapy is that it’s a de-escalation therapy. It makes sense to start the patients when they are at their sickest on the highest settings, rescue the patient fast, and then titrate down upon stabilization.

In a suspected COPD exacerbation, I typically start around 25-35 L/min of flow and enough FiO2 to bring the sats into the low to mid 90s, with a focus on ventilatory support over oxygenation. I often start right off with 40 L/min, which is the maximum setting, but in general I’ve found that these patients titrate to between 25-35 L/min, the clinically effective range for adults. Some of my COPD patients who are on home oxygen often prefer the humidified

I was initially told that there was a subset of sick patients that I might need to use non-invasive positive pressure on to rescue from the need for intubation. But what I’ve found after years of practice is that that range of “too sick for high velocity therapy” is really quite small. This therapy has almost replaced use of noninvasive positive pressure ventilation in my practice. Unless a patient is signed out to me on mask-based NIV therapy, and so long as the patient is spontaneously breathing and doesn’t need to be intubated, I put them on this mask-free form of NIV. Looking back, I’ve had patients with really bad hypercapnic respiratory failure who I believed required intubation but put them on Vapotherm therapy while I prepared for the procedure. In those 5 to 10 minutes I have had several turn around avoiding the tube altogether. My comfort level with the therapy has grown exponentially over time, yet I still sometimes stand surprised at what it can do.

gas that’s delivered to them to be cooler, so I tend to turn the temperature down for patient comfort in that group. Otherwise, I use 37 degrees (body temperature) for everyone else, as this temperature and humidity level best supports the patient’s own respiratory tract protective mechanisms. Once stabilized I first titrate down FiO2 based on the patient’s oxygen saturation. I’ve found that even in exacerbation, I can often get their oxygen requirement at or near their baseline. The flow rate is really what is considered the “therapy” and is titrated down after oxygen requirements stabilize -- as the patient’s work of breathing, aeration, wheezing and their pCO2 improve. When these factors have improved and the patient is down to 25 L/min high velocity therapy can be discontinued, usually to simple nasal cannula (and often to the patient’s baseline oxygen requirement). If there is concern for a highly infectious disease that can be transmitted by airborne droplets, such as COVID-19, a simple facemask is the best way to protect the healthcare

I start high, help their air hunger, reduce the work of breathing and in most cases that’s enough to stabilize the patient so that I can have time to treat the underlying disease causing the symptoms.




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to get with a masked form of NIV. This is the way to go in 2020 to treat undifferentiated respiratory distress.

team. I place a simple surgical mask on the patient after the cannula is placed on their face, but before the therapy is initiated. Computer modeling evidence published in CHEST has shown that for high velocity therapy in particular, following this course of action reduces the risk of airborne droplet dispersion down to a level that’s comparable to a patient’s tidal breathing while wearing a mask.1 A follow-up publication in JACEP Open corroborates these preliminary findings.2 The other important component of that modeling is that using the surgical mask largely preserves the clinical efficacy of the therapy. In those cases, I do turn the liter flow a little higher to get the level of flush I’m looking for. It’s just that simple. I start high, help their air hunger, reduce the work of breathing and in most cases that’s enough to stabilize the patient so that I can have time to treat the underlying disease causing the symptoms. I’ll continue using Vapotherm high velocity therapy because the patients like it, they tolerate it well, and it gives me the same or better results than I used

References1. Leonard S, Atwood CW Jr, Walsh BK, DeBellis RJ, Dungan GC, Strasser W, Whittle JS, Preliminary Findings of Control of Dispersion of Aerosols and Droplets during High Velocity Nasal Insufflation Therapy Using a Simple Surgical Mask: Implications for High Flow Nasal Cannula, CHEST (2020), doi:https://doi.org/10.1016/j.chest.2020.03.043.2. Leonard S, Strasser W, Whittle JS, Volakis LI, DeBellis RJ, Prichard R, Atwood CW, Dungan GC. Reducing aerosol dispersion by High Flow Therapy in COVID-19: High Resolution Computational Fluid Dynamics

Simulations of Particle Behavior during High Velocity Nasal Insufflation with a Simple Surgical Mask. JACEP Open (2020). https://doi.org/10.1002/emp2.12158




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What Does it Mean That Vapotherm High Velocity Therapy is “Noninferior” to NiPPV?

By George C Dungan, II, MPhil (Medicine) with Kristina Paschkopić George Dungan is Vice President, Science and Innovation for Vapotherm, responsible for innovation, intellectual property, scientific characterization and clinical research. He is also currently an Adjunct Professor at Canisius College, Buffalo, NY. Prior to joining Vapotherm, George was at the Woolcock Institute of Medical Research in Sydney, Australia from 2005 to 2011 where he served as the Chief Operating Officer, Head of Technology Research and Technical Director for the Australian Centre for Chronobiology, Endocrinology and Sleep Science. His research interests include clinical management of disease and characterization of complex physiology. George has worked in sleep, neurophysiology, and pulmonary medicine since 1982. He received his MPhil in Medicine from Sydney Medical School, University of Sydney, Australia.

1) superiority—to assess whether one treatment is better than another—2) equivalence, or 3) noninferiority—which is used to compare a new therapy to a current standard therapy of known efficacy. Noninferiority trial design may sound confusing and are more complex to design and interpret, but they are a key tool in cases where a new treatment which offers some selective new advantage is being compared to an existing, known treatment. A noninferiority trial is designed to establish whether a new treatment is not less efficacious than the control, taking into account that the new treatment may bring specific new advantages to the care of the patient.

A multi-center, randomized, controlled trial has shown that Vapotherm high velocity therapy is comparable in efficacy to non-invasive positive pressure ventilation (NiPPV) when it comes to managing respiratory distress of spontaneously breathing adults.1 This supports using high velocity therapy as a form of mask-free NIV. Before we go over the trial and interpretation of results, it’s valuable to spend some time on why this trial was designed to be a noninferiority trial.

Why a noninferiority trial? When comparing two therapies to each other, the three trial designs currently commonly employed are

High velocity nasal insufflation (HVNI)—which is the clinical term for Vapotherm’s high velocity therapy—was invented in the late 1990’s, about twenty years after common nasal CPAP and ten years after bi-level PAP. It pioneered heated, humidified, high liter flows as a method to provide respiratory support and reliable delivery of oxygen. This means that NiPPV, with its pressure-based mechanism of action, had about a two decade head start in becoming adopted as a front-line tool for treating respiratory distress and establishing itself as the gold standard. Meanwhile, after the invention of high velocity therapy, several devices came




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In a non-inferiority design, clinician/researchers must determine what is the ‘allowable difference’ in the performance of the new therapy being tested, in order to state that the new therapy is non-inferior to the standard – known as the ‘non-inferiority margin’. The difference has to take into account some clinically meaningful advantage of the new therapy – in this case the opportunity for improved management of the patient using the HVNI small-bore cannula as compared to the tight-fitting sealed mask interface of NiPPV with its attendant compliance and management issues. When designing a trial, the known performance of the standard therapy is determined as the comparison endpoint, along with the known variability

to market that collectively fall under the umbrella of high flow nasal oxygen (HFNO), or high flow nasal cannula (HFNC), among other terms. HFNC became established as a comfortable means of oxygen support and several studies even showed that it was noninferior to NIV for managing patients presenting with hypoxemic respiratory distress.2,3 HVNI was, and often still is, colloquially viewed as another type of HFNC and regarded as an oxygenation device. That is certainly correct in that HVNI does provide oxygenation support, as both therapies share a feature of high liter-flow of oxygenated gas to the patient using an open interface. But several research clinicians familiar with the therapy and with bench study evidence, hypothesized that the actual mechanistic differences of HVNI may also effectively provided ventilatory support. A noninferiority trial design to test the ability to provide ventilatory support as well as oxygenation was the most reasonable choice to study whether HVNI indeed was a viable alternative to NiPPV.

in those outcomes. That variability is important to add a ‘window’ to the comparison. The performance of the new therapy is then compared to the standard therapy, and the differences of the two results are evaluated with this non-inferiority margin as the decision point. There are several possible outcomes. Comparing the difference in outcomes of the two therapies (e.g., % Intubated for HVNI - % Intubated NiPPV), the new therapy is inferior, meaning that the difference of the new to the standard therapy, along with the variability is beyond the non-inferiority margin (shown below). If the variability of the difference is below the non-inferiority margin but still completely above the no-difference line, the new therapy is deemed non-inferior.

From Lavizzari 20161




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In the case of HVNI these advantages included a simple small-bore cannula interface as opposed to a sealed facemask, as well as a therapy that was not principally pressure based. The researchers decided that the advantages of the new therapy in management of the patients in this clinical setting were sufficient to permit a 5% worse performance of the HVNI therapy as compared to the NiPPV standard, while still allowing the study to conclude that the new therapy was non-inferior to NiPPV. In this specific case, that meant that the other advantages of HVNI including patient tolerance, meant that a failure rate of 21.1% (16.1% + 5%) would be considered successful. That was the original target for the study, around which the sample size was selected for the conduct of the study.

The literature on NiPPV escalation to intubation shows

If the difference of the two therapies, including the variability, is in favor of the new therapy, the new therapy can be called superior. For this trial, the designed primary endpoint was the percentage of patients who were randomized to either HVNI or NiPPV would fail the therapy. Doshi et al. chose intubation as the primary endpoint to compare the two therapies – and as the characteristic around which the study was built. NiPPV failure requiring intubation was well described in the literature across the common diagnoses presenting in the Emergency Department. For example, large meta-analysis of such patients presenting with COPD showed that a failure rate requiring intubation was 16.1%,2 and for patients with Acute Decompensated Heart Failure and cardiogenic pulmonary edema was 16.9%.3 The selection of this margin must weigh the known efficacy of the standard therapy (in this study, for example, the known 16.1% intubation rate for COPD patients presenting in the ED) as well as the effect of the advantages of the new therapy.

a wide range of outcomes, and this variability must also be considered for the non-inferiority comparison. To do this, a total of 10% was added to the 5% target, to account for such variability, and so the researchers determined a 15% noninferiority margin for intubation. In other words, so long as the two therapies were within 15 percentage points of each other regarding intubation, HVNI would be shown to be noninferior to NiPPV. Even more specifically, as long as the confidence-intervals for the two endpoint results fall within that margin window, the therapies are deemed non-inferior – and the confidence intervals for the outcomes is calculated based on the number of subjects studied. If the tested treatment (HVNI, in this case) falls within this predetermined range as compared to the control treatment (NiPPV), then the tested treatment is shown to be noninferior to the control, i.e. not worse than the control. If the tested treatment does not fall within that margin, then—and this sounds discombobulating—the tested

If the variability of the difference is below the non-inferiority margin but still completely above the no-difference line, the new therapy is deemed non-inferior.




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as a ‘treatment failure’ in terms of the original therapy to which the patient was randomized. This accommodated the subjective clinician decisions and mitigate risk to the patients, and the study design allowed for therapy crossover. Thus, in addition to the planned ‘failure requiring intubation’ an ‘all-cause’ failure was added as a co-primary endpoint for the study. This meant that if a patient was, for example, randomly assigned to either HVNI or NiPPV, the clinician was allowed to cross the patient over to the opposite therapy if they felt the patient wasn’t doing well. Given that intubation wasn’t imminent at the decision of crossover, the decision for crossover was highly variable and subjective to the clinician, in this study estimated at 15%. To account for this variability, the researchers

treatment is technically ‘not noninferior’ to the control, i.e. it is worse than the control.

Why are there two primary endpoints? Doshi and colleagues designed a randomized, controlled, multi-center noninferiority trial that studied how HVNI compared to NiPPV in the treatment of spontaneously breathing adults presenting in the emergency room with undifferentiated respiratory distress.4 It’s noteworthy that in large trials that established the noninferiority of HFNC to NiPPV, the designs did not include hypercapnic patients.5,6 Doshi et al. included adult all-comers in respiratory distress who would have otherwise received NiPPV therapy. When the study was presented for review, the strong standard of care preference was for NiPPV. In the management of these patients, time is often of the essence. As such, clinicians managing patients in the study were allowed to change therapies if they felt, in their clinical judgement, that either therapy was not effective. This must then be considered

determined a noninferiority margin of 20% (5% allowable difference plus 15% variability) for the crossover endpoint. This means that arm failure, i.e. crossover to the other study arm, was deemed noninferior so long as the therapy outcomes fell within 20 percentage points of each other.

What do the results mean for clinical practice? The study was powered appropriately to answer the primary endpoint questions by enrolling 204 patients. Of the 204 patients enrolled in the study, 104 were randomly assigned to the HVNI arm and 100 to the NiPPV arm. Figure 1 shows the outcomes regarding failure to intubation. 7% of patients in the HVNI arm were intubated and 13% of patients in the NiPPV arm were. This amounts to a

Figure 1. Intubation Rate HVNI vs NIPPV




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difference falling within the predetermined noninferiority margin of 20%. HVNI was deemed no worse than NiPPV even when accounting for subjective crossovers in the all-cause arm failure. In short, the trial conducted by Doshi and colleagues demonstrated that HVNI outcomes were comparable to NiPPV outcomes on adults coming into the emergency room in undifferentiated respiratory distress. The efficacy of HVNI is comparable to that of NiPPV. In addition to these primary outcomes, the authors also assessed several secondary outcomes shown in Figure 3. Secondary endpoints are studied in order to help understand and explain the primary endpoint findings. In this study, the secondary

-6% difference (a negative difference means HVNI performs better – and the non-inferiority threshold would be +15), with the confidence of the 6% difference between 2% and 11% - falling well within the set noninferiority margin of +15%. It thereby shows that HVNI is no worse than NiPPV at helping patients avoid intubation. Figure 2 shows the outcomes for the crossover endpoint of the study, i.e. the all-cause arm failure. This was the failure, regardless of whether the patient failed to intubation or failed just the respective arm they were initially randomized to. Here, 26% of patients failed the HVNI arm, and 17% failed the NiPPV arm. This means the two therapies were within +9 percentage points of each other, and the variability of the

endpoints suggested that the effect of the two therapies on measures which are often important in management of respiratory distress, were not significantly different between NiPPV and HVNI. Management of delivery of oxygen and blood CO2, pulse and respiratory rate, perception of shortness of breath were all not significantly different between the to therapies, and all showed improvement of the first four hours of the initiation of therapy. Clinicians were asked to provide their assessment of some key performance issues related to the two therapies. Physicians rated HVNI more highly when it came to perceptions of patient response, patient comfort, and simplicity of use for the technology. The remaining two secondary outcome categories were “technical difficulties” and “need for monitoring” where the two therapies were rated similarly. Regarding clinical practice, this means that clinicians have a viable alternative to NiPPV that doesn’t place the patient at any increased risk of intubation and offers some

Figure 2. All Cause Arm Failure, HVNI vs NIPPV




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their disposal when making decisions about the best course of treatment for their patients.

potential advantages regarding patient comfort and response. Given that more than 30% of patients fail NiPPV due to mask intolerance,7 having a form of mask-free NIV may be an attractive option. The authors note as much in their article, writing “patients treated with high-velocity nasal insufflation can more easily communicate, receive oral medications, and eat without interruption of therapy, which are limitations of noninvasive positive-pressure ventilation.” In conclusion, the evidence that Vapotherm high velocity therapy is similar in efficacy to NiPPV means that clinicians have an additional tool at

Medicine, 2018. Published online ahead of print. https://www.ncbi.nlm.nih.gov/pubmed/293108685. Frat, Jean-Pierre, Rémi Coudroy, Nicolas Marjanovic, and Arnaud W. Thille. “High-flow nasal oxygen therapy and noninvasive ventilation in the management of acute hypoxemic respiratory failure.” Ann Transl Med. 2017 Jul; 5(14): 297. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5537116/6. Hernández, Gonzalo, Concepción Vaquero, Laura Colinas, et al. “Effect of Postextubation High-Flow Nasal Cannula vs Noninvasive Ventilation on Reintubation and Postextubation Respiratory Failure in High-Risk Patients A Randomized Clinical Trial.” JAMA. 2016;316(15):1565-1574. doi:10.1001/jama.2016.14194 https://jamanetwork.com/journals/jama/fullarticle/25653047. Carron M. et al. Complications of non-invasive ventilation techniques: a comprehensive qualitative review of randomized trials. British Journal of Anaesthesia. 110(6):896-914. (2013) https://www.ncbi.nlm.nih.gov/pubmed/23562934

References1. Lavizzari A, Colnaghi M, Ciuffini F, et al. Heated, Humidified High-Flow Nasal Cannula vs Nasal Continuous Positive Airway Pressure for Respiratory Distress Syndrome of Prematurity: A Randomized Clinical Noninferiority Trial.JAMA Pediatr. 2016.2. Ram FS, Picot J, Lightowler J, et al. Non-invasive positive pressure ventilation for treatment of respiratory failure due to exacerbations of chronic obstructive pulmonary disease. Cochrane Database Syst Rev.2004;(3)CD004104.3. Vital FM, Ladeira MT, Atallah AN. Non-invasive positive pressure ventilation (CPAP or bilevel NPPV) for cardiogenic pulmonary oedema. Cochrane Database Syst Rev. 2013;(5)CD005351.4. Doshi, Pratik et al. High-Velocity Nasal Insufflation in the Treatment of Respiratory Failure: A Randomized Clinical Trial. Annals of Emergency

Figure 3. Select Secondary Outcomes: HVNI vs. NiPPV




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COPD Patients on Vapotherm High Velocity Therapy — Ventilatory Support, Intubations, and Length of Stay Implications from a Subgroup Analysis

By Leo Volakis, BS, MS, PhDLeonithas I. Volakis, BS, MS, PhD, Research Scientist Vapotherm; Dr. Volakis has a multidisciplinary background in engineering, physiology, and cellular biology, stemming from his interest in biomedical research and passion to advance medical technology. During his undergraduate (BS) at the University of Michigan and graduate studies (MS, PhD) at The Ohio State University, he has developed, participated in, and completed various multidisciplinary research projects in a wide range of topics related to medical science/technology, diagnostic tools for diseases, cellular/molecular/tissue engineering, and microdevices. He has an undergraduate degree in Mechanical Engineering, and dual-graduate degrees in Biomedical Engineering. Outside of his strong research acumen, he has teaching experience in introductory biomedical course(s) and various biomedical laboratory courses. Upon completion of his PhD in 2017, he joined Vapotherm as the Research Scientist for the Department of Science & Innovation, handles scientific inquires, and has developed/managed/completed multiple clinical studies, research projects, and publications involving Vapotherm high velocity therapy.

modality could successfully manage hypercapnic respiratory distress. To better understand the subgroup analysis that sought to address that question, here is a quick overview of the original study.

Partial Overview of Original Trial The large randomized controlled trial was conducted across five emergency departments and designed to randomize all-comers in respiratory distress. So long as the patients were

In 2018, Doshi and colleagues showed that Vapotherm high velocity therapy has comparable outcomes to noninvasive positive pressure ventilation (NiPPV) when treating adults in respiratory distress.1 This trial was the first of its kind in that it compared the efficacy of a mask-free form of NIV (Vapotherm high velocity therapy) to an established respiratory support modality (NiPPV). Its results raised further questions, especially whether a mask-free, not pressure-based

spontaneously breathing and didn’t meet other exclusion criteria, they were randomly assigned either to the NiPPV or the high velocity nasal insufflation (HVNI) study arm. Approximately half of the 104 patients in the HVNI arm had a discharge diagnosis that included hypercapnic respiratory failure or COPD. Figure 1 shows the exact diagnoses breakdown. The trial results found that HVNI was comparable to NiPPV in efficacy overall.




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When the researchers looked at the markers of ventilatory effect across all patients in both arms (n=204), they found that HVNI also reduced blood PCO2 similarly well to NiPPV (Figure 2). We can see in Figure 2 that the NiPPV arm had patients whose PCO2 was on average slightly higher than that of the HVNI arm, but not significantly so. Nevertheless, the downward trend between the two groups was comparable over time. This indicates that HVNI achieved ventilatory efficacy similar to that of NiPPV.

Subgroup Analysis Given these results, a team of researchers and clinicians, myself included, conducted a subgroup analysis of COPD patients from the original trial. This subgroup analysis assessed the ventilatory effect of HVNI on this patient population, who traditionally required mask and pressure-based therapy for hypercapnia management. The subgroup analysis was published in Heart & Lung, titled “The ventilatory effect of high velocity nasal insufflation compared to noninvasive positive-pressure ventilation in

Figure 1. HVNI Discharge Diagnosis (n=104)

Figure 2. Blood Carbon Dioxide Tension Over Time as a Function of Group

the treatment of hypercapneic respiratory failure: A subgroup analysis.”2

A total of 65 patients met the subgroup analysis criteria—34 HVNI, 31 NiPPV. The primary outcomes we looked at were change in PCO2 and pH over time. Secondary outcomes were treatment failure, as evidenced by therapy crossover

or intubation rate. Markers of Ventilatory Effect We found that the changes in PCO2 (Figure 3) and pH (Figure 4) trended similarly between the two study arms. This indicates that, for patients in this study, HVNI had comparable ventilatory efficacy to NiPPV.




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as failing on one therapy and crossed them over to the other, the other therapy was able to keep the patient from intubation 75% of the time. Both therapies failed half the time due to failure to ventilate. For the NiPPV arm, the remaining half of failures were due to an inability of the patients to tolerate the modality. We did not see this failure due to intolerance in the

Intubations and Arm Failure As for the secondary outcomes, they too were comparable. As Figures 5 and 6 show, the intubation rate was 16.1% for NiPPV, and 5.9% for HVNI. The all-cause therapy failure was 25.8% for NiPPV and 23.5% for HVNI. The salvage rate for both groups following crossover was 75%. In other words, if the clinician perceived the patient

HVNI arm.

Length of Stay One very interesting finding was the length of stay (LOS) for these patients. There was no statistical difference between the groups when it came to overall LOS or emergency department LOS or medical floor LOS. But we found that the HVNI patients spent significantly less time in the ICU and more time on the medical floor and step-down unit. Table 1 shows the breakdown. This finding suggests that the two groups of patients were comparably sick and needed comparable hospital time to get better. The patients’ physiological measures over time also show this similarity between the groups. Therefore, the difference in patient disposition could be based on hospital protocol in that some hospitals require NiPPV patients to be admitted to the ICU. It could also be due to clinician perception that patients on HVNI responded better to therapy and were more comfortable.1 If this finding can be replicated in a larger trial, it would have significant implications for

Figure 3. PCO2 Trend Over Time

Figure 4. pH Trend Over Time




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hospital workflows as well as cost savings. One key limitation is that the original trial was not powered for this subgroup analysis. Additionally, the baseline PCO2 was lower in the HVNI arm which may have some clinical relevance despite it not being a statistically significant difference. Despite these limitations, we concluded that the results of these analyses suggest that HVNI “may be considered another noninvasive ventilation therapy, that is available in managing patients with acute hypercapneic respiratory failure.”

References1. Doshi P, Whittle JS, Bublewicz M, et al. High-Velocity Nasal Insufflation in the Treatment of Respiratory Failure: A Randomized Clinical Trial. Ann Emerg Med. 2018;72(1):73-83 e75.2. Doshi P, Whittle JS, Dungan G et al, Heart Lung. 2020 Apr 6. https://doi.org/10.1016/j.hrtlng.2020.03.008

Figure 5. Intubation Rate

Figure 6. All Cause Arm Failure

Table 1. Length of Stay




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COPD Patients and Wound Care Implications with Vapotherm High Velocity Therapy

By Jeanne Pettinichi, MSN, RN, CPN, CPENJeanne Pettinichi has 34 years’ experience as a nurse including 20 years working in Pediatric Emergency Nursing. She has nearly 10 years’ experience as a Clinical Nurse Education Specialist at two Level I Trauma Centers, the Cincinnati Children’s Hospital Medical Hospital, and the Emergency Medicine & Trauma Center at Children’s National Medical Center in Washington, DC. She obtained her BSN from Vanderbilt University and her MSN degree from Northern Kentucky University. Jeanne currently serves as the Clinical Nurse Educator for Vapotherm.

The Importance of Medical Device-Related Pressure Injury Prevention The most obvious reason to prevent hospital acquired pressure injuries (HAPIs) is for our patients’ well-being. They can be painful and at their most severe can even be traumatizing and impact a patient’s sense of self, especially if they happen on the face. Another reason to do our best to avoid them is the costs hospitals can incur due to HAPIs. According to the Agency for Healthcare Research and Quality (AHRQ), 2.5 million patients per year are affected by pressure injuries with the financial cost ranging from $9.1-$11.6 billion per year in the US.1 The individual patient care cost ranges from $20,900 to $151,700 per pressure injury.

If you, like me, started your clinical career decades ago, you probably heard the term “pressure ulcer” over and over again. But the term “pressure injury” has become much more prevalent now when discussing wound care and prevention. One of the key reasons for the change is that the word “ulcer” connotes an open sore, while “injury” doesn’t have to. For example, if I have a patient who has a tightly strapped mask on his face and develops redness and swelling along the bridge of his nose, that is a pressure injury. The skin may not be broken at all. Regardless of what you call them, it is our responsibility as clinicians to minimize the chance of their occurrence.

Medicare estimated in 2007 that each pressure ulcer added $43,180 in costs to a hospital stay.2 In addition, 17,000 lawsuits are pressure injury related; the second most common claim after wrongful death.1 The good news is that most HAPIs are preventable. When it comes to medical-device related pressure-injuries (MDRPIs), sometimes prevention is not only a matter of proper equipment application, but equipment selection. In cases of patients who need noninvasive ventilation (NIV), equipment selection can be paramount in MDRPI prevention. One of the reasons I focus on noninvasive positive pressure ventilation (NiPPV) masks is because they are one of the most common medical devices that lead to pressure injuries, as




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and much of the industrialized world will increase by 210% from 2010.5 The authors note that “Despite uncertainties in the trends, the plausible ranges of predictions were all consistent with a substantial increase in the future burden. Similarly, projections remained consistent in a series of sensitivity analyses.”5

As we continue to see and anticipate an increase in patients with COPD exacerbations, clinicians need to continue to be vigilant about MDRPI prevention. Patients with COPD exacerbation tend to be older with more fragile skin and due to their hypercapnia, they are often put on NiPPV for symptom management. As established, NiPPV ranks high among devices that frequently cause HAPIs. It is

seen in Table 1.3

Depending on the study, pressure injuries from NiPPV interfaces occur in 5-30% of patients treated with the device.3 Some research even shows a frequency of up to 50%. This frequency is becoming particularly relevant due to the rise in hospitalizations from acute respiratory failure.4

Planning for MDRPI Prevention in the Face of Rising COPD Cases Between 2001 and 2009 such hospitalizations, including from CHF, ARDS, and COPD exacerbations, doubled from about 1 million a year to 2 million in the US.4 A population-based analysis by Khakban and colleagues predicts that by 2030, COPD-related hospitalization in North America

a device designed to have a tightly strapped, sealed mask and even with proper mask fit and frequent rotation and care, the first stages of pressure injuries can develop within a few short hours.2 This is why clinicians should be aware of their options when it comes to NIV to manage hypercapnic symptoms.

Vapotherm High Velocity Therapy as a Mask-Free form of NIV for COPD Symptom Management Vapotherm high velocity therapy has been clinically proven to be as effective as NiPPV for respiratory support in spontaneously breathing patients.6 When it comes to MDRPI prevention, the key difference between NiPPV and high velocity therapy is that the latter is a mask-free, open system. Its interface is a simple nasal cannula that does not require a seal and its chief mechanism of action is not pressure-based. Just like with any medical device, there is no guarantee that a cannula interface won’t cause a MDRPI, but studies have shown that nasal cannula interfaces are less likely to cause pressure

Device FrequencyCervical Neck Collar 7.2%; 33% in 5 days; 44% > 5 days

ETT 10.5%NGTs 8%

NiPPV Devices (BiPAP, CPAP) 5-30% and up to 50%Oxygen Tubing 12.9% (children)

13-19%Pulse Oximetry Monitors 9% (children)

Tracheostomy Flanges & Ties 8.1%Adapted from Black et al.

Table 1. Pressure Injury Frequency by Medical Device




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cause pressure injuries and intolerance, in the case of NiPPV, high velocity therapy is an attractive alternative. As our population continues to age and we continue to see an influx of respiratory distress hospitalizations, clinicians should be aware of all the available options in their tool kit.

injuries by comparison to NiPPV interfaces.7 This option may not only be appealing to COPD patients who have a history of repeated hospital visits or have a prolonged ICU stay, but also for palliative care of COPD patients.

Patient Comfort with Vapotherm High Velocity Therapy There are additional benefits to having a mask-free mode of ventilatory support. Carron and colleagues show in Table 2 a list of potential complications that can lead to a mask intolerance.8

In contrast, simply eliminating the need for a tightly sealed mask eliminates the root-cause for most of these complications. Vapotherm therapy delivers optimally humidified gas to the patient via a comfortable cannula. This means that patients can eat/drink, speak, and take oral medications all without therapy interruption and while minimizing the risk of mask-based pressure injuries—an advantage for both the patient and the clinician. While it is not always possible to choose a medical device that is less likely to

References1. AHRQ, Agency for healthcare quality and research advancing excellence in health. Preventing pressure ulcers in hospitals 2014; https://www.ahrq.gov/professionals/systems/hospital/pressureulcertoolkit/putool1.html2. Oomens CW, Bader DL, Loerakker S, Baaijens F. Pressure induced deep tissue injury explained. Annals of Biomedical Engineering 2015; 43(2), 297-305.3. Black, J., Alves P, Brindle CT, Dealey C, Santamaria N, Call E, Clark M. Use of wound dressings to enhance prevention of pressure ulcers caused by medical devices. Int Wound J 2013; doi: 10.1111/iwj.121114. Stefan MS, Shieh MS, Pekow PS, et al. Epidemiology and outcomes of acute respiratory failure in the United States,

IncidenceAir Leaks from Mask 80-100%

Mask Discomfort 30-50%Skin Breakdown 2-50%

Nasal Congestion 20-50%Oronasal Dryness 10-20%

Gastric Insufflation 10-50%Ventilator Dissynchrony 13-100%

Table 2. Complications that Lead to Mask Intolerance

Adapted from Carron et al.

20012009: a national survey. J Hosp Med. 2013;8(2):76–82.5. Khakban A, Sin DD, FitzGerald JM, McManus BM, Ng R, Hollander Z, et al. The projected epidemic of chronic obstructive pulmonary disease hospitalizations over the next 15 years: a population-based perspective. Am J Respir Crit Care Med 2017;195:287–291.6. Doshi, Pratik et al. High-Velocity Nasal Insufflation in the Treatment of Respiratory Failure: A Randomized Clinical Trial. Annals of Emergency Medicine, 2018. https://www.ncbi.nlm.nih.gov/pubmed/293108687. Black J, Kalowes P. Medical Device-Related Pressure Ulcers. Chronic Wound Care Management and Research Volume 3; 29 August 2016 Volume 2016:3 Pages 91—99.8. Carron M et al, Complications of non-invasive ventilation techniques: a comprehensive qualitative review of randomized trials, British Journal of Anaesthesia, 110 (6): 896–914 (2013).




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Ventilatory Support via an Open System —How Does it Work?

By Amrit Kahlon, MDAmrit Kahlon, MD is a Clinical Research Manager at Vapotherm in Exeter, NH. Dr. Kahlon has a background in medicine, trained as a medical doctor. He completed his premedical studies at The Medical University of Silesia and completed his medical degree at Atlantic University in 2016. Upon graduating from medical school, he has been extensively involved with various organizations and medical technology, working in the clinical research space, focusing on various modalities and treatment therapies for diseases in a variety of patient populations. Dr. Kahlon joined Vapotherm as a clinical research manager with the Department of Science & Innovation in 2019, working on clinical research projects associated with Vapotherm’s technology.

where the mask interface presents an aspiration risk, or whether the patient is experiencing claustrophobia, there are advantages to having ventilatory support that avoids tight-fitting masks. High velocity nasal insufflation (HVNI) offers such ventilatory support and the question becomes: how can it do that while being an open system using a nasal cannula interface? The primary mechanism of action of Vapotherm high velocity therapy, is the flushing of end-expiratory CO2 from the upper airway between breaths. This is accomplished rapidly and efficiently with a high velocity stream of optimally conditioned breathing gas. Because this is an

Traditional wisdom holds that the way to give a patient ventilatory support is to apply positive pressure. This is in part why noninvasive positive pressure ventilation (NiPPV) has been the gold standard treatment for hypercapnic patients, such as those with COPD exacerbations. NiPPV reduces the risks associated with invasive mechanical ventilation (IMV) while also being more tolerable for patients. While it is preferable to intubation, not all patients who are indicated for it tolerate the treatment. 12-33% of all NiPPV failure is ascribed to discomfort alone while 30-50% of patients may be intolerant.1 Whether it is a matter of fitting a mask on a bearded patient or treating a nauseous patient

open system, the fresh gas is insufflated through the nares and the end-expiratory CO2 is flushed out through the nose and mouth, as shown in Figure 1. This reduces the CO2 content of the next inspiration and fills the nasopharyngeal cavity with fresh gas. One way to visualize this effect is by looking at tracheostomies. By bypassing the upper airway, the patient is unburdened from rebreathing

Figure 1. High velocity flush




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Respiratory Rate — 12 breaths per minuteTidal Volume — 500 mlDead Space — 150 ml (approximately 1/3 of the tidal volume)

When plugging these numbers into the Alveolar Ventilation equation, we get 4.2 L/min:

4.2 L/min = (500ml – 150 ml) x 12

In this case, the 4.2 L/min is the “physiological target” that this hypothetical patient has. (Remember, the human body sets its own ventilation target and then, until failure, does work to meet it.) If we were to place this hypothetical patient on HVNI, the therapy would reduce the dead space, which would lead to one of two outcomes.

1. Slightly less likely - We’d see a drop in tidal volume which would maintain the same respiratory rate to meet the 4.2 L/min target:

4.2 L/min = (450ml – 100 ml) x 12

2. More likely to happen - We’d see a reduction in the respiratory rate to meet the body’s ventilatory demand of 4.2 L/min:

4.2 L/min = (500ml – 100ml) x 10.5

In either case though, whether we see a drop in tidal volume or in respiratory rate, both would result in lower work of breathing. That is how the primary mechanism of HVNI works. As long as the patient has a spontaneous respiratory drive, HVNI provides ventilatory support via this principle.

Other Mechanisms of Action Although the flush of end-expiratory CO2 is the primary mechanism of action, HVNI also achieves its efficacy in part through the following:3

• Some distending airway pressure - Primarily during exhalation

dead space volume. A tracheostomy mechanically bypasses the dead space, the high velocity purge functionally minimizes it by changing the dead space to a fresh gas reservoir. Let us review some basics of alveolar ventilation.

Alveolar Ventilation = (Tidal Volume — Dead Space) x Respiratory Rate The Alveolar Ventilation equation is the similar to the equation for Minute Ventilation (Tidal volume x respiratory rate), but adjusted to account for dead space. In order for NiPPV to achieve ventilation, the mechanism most greatly impacts the “Tidal Volume” portion of the equation.2 This is the traditional mechanism of action for positive pressure ventilation that clinicians are well-familiar with. However, the equation shows it is also possible to achieve alveolar ventilation by affecting the other parameter in the equation: Dead Space. To illustrate this concept, let us consider an average adult’s respiratory parameters:




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efficacy comparable to NiPPV.4

Vapotherm high velocity therapy is designed to deliver high velocity, which is a key component in its efficacy. Unlike most conventional large-bore HFNC, Vapotherm therapy uses a small-bore cannula. In the 2016 study “Computational Fluid Dynamics Modeling of Extrathoracic Airway Flush: Evaluation of High Flow Nasal Cannula Design Elements” Miller and colleagues demonstrated that small-bore cannula prongs flush the upper airway dead space faster than a large-bore cannula.5

Figure 2 shows the velocity comparison between HVNI and conventional high flow. As illustrated, HVNI requires a lower flow rate to achieve greater velocity. In doing so, it generates greater turbulent energy which in turn leads to greater flush efficiency. For example, HVNI achieves the same velocity at approximately 15 L/min that HFNC systems require 60 L/min to achieve. This differentiator in velocity translates into a real-life impact on the treatment of patients.

against the high velocity flow.

• Warming gas flow (typically 33-37°C) - Which decreases inspiratory resistance and reduces metabolic burden for the patient.

• Humidification - Optimal humidity preserves mucociliary function and aids in mucus clearance from airways.

Why High Velocity Therapy Isn’t High Flow It is obvious that there are several surface parallels between HVNI and high flow nasal cannula (HFNC) products. The two often get conflated and the comparison is understandable at first glance—both deliver high liter flows of conditioned gas though a cannula interface. However, there are significant mechanistic differences between these devices and the likely explanation for the difference in clinical outcomes. At the time of this writing high velocity therapy is the only Mask-Free NIV™ for spontaneously breathing patients that includes a velocity-based mechanism of action which gives it clinical

The bottom line is that the more tachypneic a patient, the more important it is that their end-expiratory CO2 be flushed rapidly – before they take their next breath in. The high velocity mechanism of HVNI achieves this rapid flush. Due to the speed of this flush, the patient breathes in less CO2 and more oxygenated gas, reducing the work of breathing and augmenting alveolar ventilation as a result. This is ultimately how HVNI succeeds in providing ventilatory support to spontaneously breathing patients and gives clinicians another tool at their disposal.

References1. Carron M, Fero U, BaHammam AS, et al. Complications of non-invasive ventilation techniques: a comprehensive qualitative review of randomized trials. British journal of anaesthesia. 2013;110(6):896-914.2. Mehta S, Hill NS. Noninvasive

Figure 2. Velocity comparison between HVNI and HFNC




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Ventilation. AJRCCM. 2001;163:540-557.3. Dysart K, Miller TL, Wolfson MR, Shaffer TH. Research in high flow therapy: mechanisms of action. Respiratory medicine. 2009;103(10):1400-1405.4. Doshi P, Whittle JS, Bublewicz M, et al. High-Velocity Nasal Insufflation in the Treatment of Respiratory Failure: A Randomized Clinical Trial. Ann Emerg Med. 2018;72(1):73-83 e75.5. Miller TL, Saberi B, Saberi S. Computational Fluid Dynamics Modeling of Extrathoracic Airway Flush: Evaluation of High Flow Nasal Cannula Design Elements. Journal of Pulmonary & Respiratory Medicine. 2016;6(5):376.

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unmasking copd exacerbations

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