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The Altitude Metaphor: Which View Do You Have?

Updated: Jun 16, 2020

Written by: Ingemar Davidson, MD, PhD & Billy Nolen, Airline Captain

The dialysis access clinical structure takes many forms affecting decision making and outcome. To illustrate these different delivery systems, let's use the altitude metaphor.

Much controversy surrounds the establishment of planning, placement and management of dialysis access.

This includes the dialysis type and modality selection, timing of access placement and who places the access. The lack of and the difficulty of performing randomized studies with multiple confounding factors, in the heterogeneous and rapidly changing ESRD population demographics, only partly explains the dialysis access conundrum. Add to this the rapidly developing and competing technologies, the wide spectrum of the professional experience, bias and socio-economic forces to make the ESRD problems multivariate and complex.

The complexity is further magnified by the several specialties seeing dialysis access through different lenses. Issues surrounding specialties are best illustrated by the Indian parable of five blind men examining an elephant and coming to vastly different conclusions as to what they find.

Figure 1. The expression "elephant in the room" is a metaphorical idiom in English for an important or enormous topic, problem, or risk that is obvious or that everyone knows, but no one wants to discuss.

A Patient-centered Dialysis Access Decision-making Algorithm

“The issue is not who places the access but who does it right, every time, to everyone, and everywhere” (1).

Another confounding factor is the widely different professional experience with which we make decisions about the best treatment of our fellow human beings. This makes the decision-making process complex and related not only to the skills and knowledge level of the individual but to his or her specialty as well. This illustrated in the Dreyfus Scale of Professional Development (Table 1) (2).

The initial Dreyfus Scale had only 5 categories with the expert being the highest. The expert level of competence is generally considered to be 10,000 hours of practice or about 10 years of professional experience – a concept popularized in Malcolm Gladwell’s book BLINK.

Table 1. Dreyfus Scale of Professional Development

  • NOVICE (Plays by the rule, low situation awareness (SA), low judgment)

  • ADVANCED BEGINNER (Follows guidelines, limited SA, all things equally important) 

  • COMPETENT (Long-term vision, planning, accountable, routine procedures

  • PROFICIENT (Holistic views, priorities, decisions made easy, some intuition, perceives deviations from normal, invited lecturer)

  • EXPERT (Intuitive grasp of situation, analytic: “I don’t follow rules, I make them”).

  • MASTER (Source of new knowledge and new ways, unique style, likes surprises)

  • PHILOSOPHER (Pre-Alzheimer)

(The connotations in Table 1 were added to project onto the medical profession.)

The dialysis access clinical structure takes many forms affecting decision making and outcome. To illustrate these different delivery systems, let's use the Altitude Metaphor.

Still at the Airport.

In this case it is an operator who only performs one procedures i.e. AVFs – for various reasons. From the aviation metaphor perspective, he or she has not even left the airport. This scenario represents very limited options for the patient.

My goal is to give you a progressively global view of dialysis access. Let's elevate ourselves so we can see the big picture of delivering dialysis access – applied worldwide.

The Bird's View.

In this scenario – at the bird’s level – the access options now include catheters, and grafts but not peritoneal dialysis (PD). There is a subliminal and unacceptable separation between PD and hemodialysis in many places, which in fact deprives our patients from the most appropriate first-time dialysis modality in 30-50% of cases.

An (unacceptable) reason not to consider PD is sometimes framed as: “I am a vascular surgeon, I don’t do PD."

The 5,000 ft View.

The next level of an access program includes peritoneal dialysis – this scenario is often associated with a transplant program in a major hospital or an academic institution. As an interesting side note - some transplant and dialysis access surgeons fly their own airplanes, usually propeller engined, which tend to fly at an altitude between 5,000 - 10,000 feet .

The 10,000 ft View.

On the next altitude level, we can see the entire city, where all access procedures including transplantation are done in a coordinated fashion. This metaphor represents a large hospital or an academic institution with resources and professionals meet all demands for a complete Renal Replacement Therapy (RRT) program. (Table 2). A complete RRT program has 4 arms: Transplant, PD, HD and palliative management.

Supersonic Speed Altitude at 60,000 ft.

If we decide to fly even higher or at 60K ft at supersonic speed, this image paraphrases the national level of ESRD and dialysis access planning, again now including disease prevention measures and transplant and national safety planning. The 60K ft level metaphor represents a national health care program.

National planning and decision-making are in principle not different from local planning – only more so in terms of impact and consequences for many individuals. The DOQI guidelines is an example of the level of altitude metaphoric national planning (3).

The image of the burning Concorde aircraft on takeoff from the ORLY airport in Paris, is a stark reminder that even the best and most sophisticated designed (healthcare) system can fail, when human errors intercept and rules are not followed.

The International Space Station – 350 miles up.

Can we “fly” even higher. Yes – Indeed we can. The International Space Station (ISS) symbolizes the global approach to ESRD.

As the ISS is an amazing technical achievement there is ample evident it has contributed to world peace – by requiring trust and cooperation between the world’s powers to achieve and this mission in space. Clearly the ESRD healthcare global community could do something similar, not even having to leave the airport!

Table 2. Features or Programs Associated with Renal Replacement Therapy (RRT)

  1. Prevention starts in childhood

  2. A kidney transplant is the best dialysis machine

  3. PD is the most optimal/appropriate/right first-time dialysis modality in 30-40 %

  4. If poor vascular anatomy for AVF, consider a Graft

  5. Perhaps an early cannulation graft to avoid CVC from AVF failure to mature

  6. Move anastomosis proximal as "Distal first" concept is not valid in most cases >65 y)

  7. In co-morbid situations – consider Proximal Arterial Inflow (PAI)

  • Prevents steal

  • Avoid CVC

8. Palliative (medical) treatment only– end of life situations

This general algorithm follows what would be reasonable to consider when all options and support systems are in place. There are of course gray areas between these choices including patient specific wishes. One serious fact is that– on a global scale - treatment with dialysis or a kidney transplantation, may only be available to 10% of people who need this treatment to live.

SUMMARY. Take home message - what an effective ESRD program should look like.

This summary outlines my thinking about the algorithmic selection, the most optimal Renal Replacement Therapy (RRT), at the right time, individualized for all patients.

The subliminal message of this tabulation is that ignoring transplantation, PD, and Grafts excludes up to 50% of your ERSD patients from the best or right RRT options. 

  1. First, as medical professionals, our role is to prevent disease from happening in the first place. Obviously, we need an understanding of the patient (or population), which is not a reality in many societies. (Patient responsibility in the prevention of kidney disease is a subject for another opinionated editorial.)

  2. After all, the kidney is the best dialysis machine. Few patients (2.7% in the U.S. per year) qualify for a transplant each year due to lack of acceptance criteria (co-morbidity) and lack of available organs.

  3. There are several compelling reasons to make Peritoneal Dialysis (PD) the most appropriate first-time dialysis modality in select (qualifying) patients - even in cases of excellent vascular mapping results.

  4. Patients, who disqualify for PD, should get an AVF when vascular mapping confirms suitable vascular anatomy.

  5. In this algorithm design, grafts come in with various benefits. For example, with the early cannulation ability Central Venous Catheters (CVC) contact time is shortened and may be eliminated altogether.

  6. Grafts are also suitable in elderly patients using the upper arm, where vessels are larger and associated with a lower risk for steal or hand ischemia.

  7. You might even consider proximal arterial inflow (PAI) in the elderly and co-morbid patients to preemptively avoid steal and the use of CVC.

  8. Finally, many patients with ESRD are in the end stage of life when a central vein catheter CVC) is the best dialysis access. Perhaps, even more often, no access is the best option for your fellow human being.


1. Davidson I, Gallieni M, Saxena R, Dolmatch B. A patient centered decision-making dialysis access algorithm. J Vasc Access. 2007; 8:59-68

2. Dreyfus, Stuart E.; Dreyfus, Hubert L. (February 1980). "A Five-Stage Model of the Mental Activities Involved in Directed Skill Acquisition" (PDF). Washington, DC: Storming Media. Retrieved June 13, 2019

3. KDOQI, Kidney Disease Outcomes Quality Initiative. AJKD Vol 75 | Iss 4 | Suppl 2 | April 2020


Even though the CME module content of the Kidney Academy website is only partially built out, we believe this online platform is a strategic tool for learning and connecting, and given the current challenges presented by COVID-19 we have decided to launch the platform early to support the global dialysis access colleagues.

For a limited time Kidney Academy is offering:

About the Authors:

Dr. Davidson’s focus is organ transplantation and Dialysis Access in End Stage Renal Disease patients. He has spent most of his professional life as Professor of Surgery at UT Southwestern Medical Center at Dallas, TX, where he also was the Medical Director of the Vascular Access Clinic at Parkland Memorial Hospital. Dr. Davidson’s research and experience is reflected in books, peer reviewed publications and proceedings. He is a current reviewer and on the editorial board for J Vascular Access and He is the co-director of CiDA (Controversies in Dialysis Access) now at its 17th  year. Dr. Davidson initiated and maintains the development of several clinical activities, most notably Kidney Academy, an online training and collaboration program for the global dialysis access medical community and is a co-investigator for NIH grant supported Clinical Dialysis Access Consortium (DAC) studies.

Billy Nolen joined WestJet is February 2020 as Vice President – Safety, Security & Quality. In this role which reports to the CEO, Billy has responsibility for overseeing the safety and security across WestJet, Encore and Swoop, the 14,700 fellow WestJet employees and the millions of guests who fly aboard WestJet aircraft each year.

Billy brings more than 30 years of operations and corporate safety, regulatory affairs and flight operations experience to WestJet and will be joining from Qantas Airways Limited, where he served as Executive Manager, Group Safety & Health responsible for the safety performance of the Qantas Group.

Billy started his career as a 767, 757 and MD-80 pilot with American Airlines and later moved into leadership roles focusing on operational and corporate safety. Billy also served as Senior Vice-President, Safety, Security and Operations with Airlines for America where he collaborated with leaders across the airline industry to enhance safety performance.

To inquire about supporting Kidney Academy, Inc. via an unrestricted educational grant to support our mission of delivering education and collaboration to the global dialysis access community, please email directly at

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