Cite this post as:
Scott Weingart, MD FCCM. EMCrit Wee – The Philosophy of APRV – TCAV with Nader Habashi. EMCrit Blog. Published on April 10, 2020. Accessed on April 20th 2024. Available at [https://emcrit.org/emcrit/philosophy-of-aprv-tcav/ ].
Financial Disclosures:
Dr. Scott Weingart, Course Director, reports no relevant financial relationships with ineligible companies.
This episode’s speaker(s), (listed above), report no relevant financial relationships with ineligible companies.
CME Review
Original Release: April 10, 2020
Date of Most Recent Review: Jan 1, 2022
Termination Date: Jan 1, 2025
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If I get it right, the Patient is breathing spontaneously on a “PEEP or CPAP-level” of 30cmH20 during approximatly 90 percent of the respiratory cycle (during p-High), while you do not monitor the pressure during P-Low (which basically equals PEEPi). So in severe ARDS with limited recruitability (small baby lung) the patient is breathing spontaneously with a maximally distendet lung (at P-High of 30cmH20). Spontaneous breathing in a lung near total lung capacity does not sound lung protective to me. High pressures during APRV may improve oxygenation. That may be due to recruitment or it may be due to impairment… Read more »
Well, spontaneously breathing on Phigh of 30 doesn‘t change the pressure, the machine is not supporting with driving pressure, so it‘s just moving gas by muscle force. If the lung is near full capacity, the patient can only move minimal amounts of gas (try to breath in fully and take another breath, wont work so well) if it‘s not fully extended, the patient is going to recruit until he is by negative pressure, so i don‘t see the harm. About the outcome,, there are a lot of studies out there and i agree, there is no really hard evidence, but… Read more »
I have been using APRV with Covid patients and having wonderful results. Start with traditional mode. Use Pplat as starting Phigh. I start with a small Thigh of 2 sec using mostly bulk ventilation. I use Auto Release on the Drager at 75%. If C02 and Ph are good I extend the Thigh by 0.5 sec at a time. I usually do a peep study on the Pulmovista (Electrical Impedance Tomography) in conventional mode and switch to APRV and compare the distribution of ventilation. In my opinion APRV is the most protective.
What is the mechanism in TCAV for avoiding pressure release during (or just before) a patient initiated breath?
While this isn’t specific to the TCAV method, the only way that I’m aware of to avoid pressure release during a spontaneous breath is to have a ventilator capable of synchronization (synchronizing spontaneous breaths with the T-high and the T-low). These synchronization windows may require user input to set (like the Vyaire Avea) or the ventilator may set them without user input (as seen with AutoRelease on Drager).
How do I set the Tlow in a spontaneously breathing patient. Because the flow curve is deformed by the spontaneous breathing it’s impossible to find the 75% or am I wrong?
This may seem off base but when I scuba dive I use a breathing pattern similar to APRV. I take a moderate sized breath and then hold and release. My holds are 5- 15 seconds at a time (est). By doing this I use more lead weight than most experienced divers my size. But what I have noticed is that I use far less of my tank than my wife. Last time we went diving, it was drift diving in Belize, the dive masters were not letting us hang around at the end of the dive and they were shocked… Read more »
1. it was said in podcast that surfactant is not produced ever or in a reasonable amout of time by collapsed lung areas? https://emcrit.org/wp-content/uploads/2016/12/broken-lung.pdf references 4 and 71 have the word surfactant. 2. It was said in podcast that surfactant production takes at least 12 hours if and only if uncollapsed lung areas are held at a very slight or perfect tension? is this the anti-thesis below? : https://ccforum.biomedcentral.com/articles/10.1186/s13054-018-1991-3 who want to leave closed areas of the lung to rest, and dislike pressure of 15cm on up as damaging and ineffective at opening. Another argument is that the lymphatic draining… Read more »
INCREDIBLE – Thank you !!!
Two Bubble and or peep valves from a Y fitting might allow one to respond to exhale flow with a drop in pressure limited to say 0.3 seconds or something relative to the setting of the other Peep valve. This could be used inside a monoplace hyperbaric chamber as it auto adjusts with pressure, and is not a fire hazard. Increases in oxegen partial pressure by altitude do not increase pulmonary shunt as does 100 percent O2. “https://europepmc.org/article/MED/26585328#free-full-text “In healthy volunteers, breathing 100 % O2 over approx. 25 min under normobaric conditions doubled intra-pulmonary right-to-left shunt, while breathing air at… Read more »
A U tube on the bottom of a bubble bottle would cause the upwards gas bubbles to act as a piston pump reducing the pressure below the pressure that originally triggered the flow. This is a common technique for underwater archeology vacums etc. TCAV wants it to be short and sudden, I seems a delayed and constant oscillation is part of the Seattle bubble system, A TCAV might be a tight U in a separately adjustable bottle from the main bottle.
https://www.engineeringforchange.org/solutions/product/sea-pap-high-oscillation-continuous-positive-airway-pressure-device/
https://clinicaltrials.gov/ct2/show/NCT03085329
https://www.nature.com/articles/pr2010112 this study shows the frequency of bubble suction which is in the range of TCAV and could be separated and targeted to part of the TCAV breath cycle by two bubblers. maybe for high pressure time to be 10 times that of the the release. the ovepressure of exhaling effort rewarded by a pressure release pulse. Repeated coughing or cheating the system could deflate the lungs? They optimize at 135 degree angle, which I imagine provides better water re-entry, but is not much different than 180 degree. The length of horizontal connection and vertical tubing could influence pulse timing.… Read more »
Does anyone have more information as to why Pressure support is inferior to Automatic tube compensation in ApRV ? https://youtu.be/1mDvURCtJBw?t=1022 At this time in the video habashi explains a little bit why he thinks PS is inferior, because it can give PS for a long stretch of time, And another thought, if ATC is better than PS, and if we see the patient is spontaneously breathing at a rate of lets say more than 30, , would it make sense to tell the machine the tubus is a smaller one than what the patient actually has so as to over… Read more »
at our shop we use the BP 840 I wasnt able to reduce the T-low under less than 0,2 seconds, the machine just doenst allow it, but i noticed that for pretty much all the patients we had ( covid pneumonia, most of them already had been on a vent for >10 days by that point) 0,2 seconds was still too long, the expiratory flow would go as low as 50% of peak expiratory flow. Would like to know what habashi says to that. Dont use aprv then? is BP 840 not made for aprv in those patients with such… Read more »
Is there a good book you guys can recommend that goes deep into respiratory physiology and ventilator modes?
that includes more than just a paragraph about aprv 😛
Tobin’s Principles Mech Vent is the best textbook, but don’t use their APRV chapter at all–it is not TCAV. For TCAV, you need to read the articles linked in my prior APRV podcast.
Thank you so much for a very insightful and riveting talk on the dynamics of TCAV and what it means to use it in a patient. It seems as if we’ve been going at mechanical ventilation the wrong way for decades.
Honestly the Newport e360T that I use doesn’t support inverse ratio Ventilation to the degree that I would need for this to work. I’ve tried it but with a max 4:1 I find it difficult to achieve T high over 2s while maintaining meaningful T low
Where does the 75% of PEF come from and why would that lead to the best lung volumes?
Purely experimental?
And what if i find that the breathing mechNics just look better for certain patient at a PEF of say 50%?