Jon-Emile S. Kenny MD [@heart_lung] A recent review of Paul Wood’s consummate approach to pulmonary hypertension is well-worth a read [1]. In it, the basic physiology of the calculated pulmonary vascular resistance [cPVR] is presented, as it often is, as a linear function. Recall, maybe traumatically, the grade-school equation y = mx + b. With this [… read more]
Jon-Emile S. Kenny MD [@heart_lung] Administering norepinephrine during sepsis resuscitation has a myriad of hemodynamic effects [1]. Importantly, the predominant mechanism probably varies around multiple patient, intervention and time-dependent elements. Most commonly, perhaps, norepinephrine is provided to raise ‘mean arterial pressure’ – an effect driven by its alpha-agonist stimulation of pre-capillary arterioles. While this plays a [… read more]
Jon-Emile S. Kenny MD [@heart_lung] When we model the circulation at the bedside, we resort to generalizations. While these mechanistic heuristics don’t completely capture the complexity of hemodynamics, they do help us think quickly when confronted by clinical urgency. For example, distilling ‘venous return’ into an upstream pressure and downstream pressure separated by a single resistance, [… read more]
Jon-Emile S. Kenny MD [@heart_lung] “As human beings, don’t we need questions without answers as well as questions with answers?” -Alan Lightman With the publication of REMAP-CAP, CAPE-COVID and CoDEX, the World Health Organization [WHO] Rapid Evidence Appraisal for COVID-19 Therapies [REACT] Working Group combined these results with 4 other randomized trials of corticosteroids in COVID-19. [… read more]
Jon-Emile S. Kenny MD [@heart_lung] “In that day there’s a moment when it all goes away …” -The Tallest Man on Earth A recent case series reporting experience with 3-dimensional trans-esophageal echocardiography in moderate-to-severe COVID-19 associated lung injury was published in Intensive Care Medicine. With only 9 patients described the findings are, nevertheless, noteworthy because of [… read more]
Jon-Emile S. Kenny MD [@heart_lung] “Let us try to assume our fundamental ambiguity.” -Simone de Beauvoir When the pre-peer review RECOVERY trial was released in mid-June of this year, clinicians lost equipoise to enroll hospitalized patients receiving at least oxygen for COVID-19 into trials including a treatment arm without corticosteroids. This brought to an early-halt three [… read more]
Thank you for the warm support regarding this volume. Errata will be listed on this page. Versions downloaded prior to Sept. 16, 2020 included the following error: chapter 2, page 43 incorrect equation 2. The axial pressure difference is directly proportional to both flow and resistance. This equation should match equation 3 in chapter 1, [… read more]
Jon-Emile S. Kenny MD [@heart_lung] Pulmonary Elastic Ergotrauma There are hidden hemodynamics in respiratory mechanics, as previously discussed. Recall that these relationships are illustrated by comparing volume-pressure, or compliance curves. Trans-pulmonary pressure, which approximates pulmonary stress, is the pressure in the airway compartment less the pleural pressure [1]. In a passive, mechanically-ventilated patient, the trans-pulmonary pressure [… read more]
Jon-Emile S. Kenny MD [@heart_lung] In part 1, evidence for and against spontaneous breathing effort in acute respiratory distress syndrome [ARDS] was briefly outlined. The mechanisms of patient self-inflicted lung injury [P-SILI] are touched upon herein with reconciliation of the clinical and experimental data. Mechanisms: basics A handful great reviews on spontaneous breathing in ARDS and [… read more]
Jon-Emile S. Kenny MD [@heart_lung] Background In an excellent review from early 2016, Gattinoni and Quintel note that ventilator induced lung injury [VILI] is better considered ventilation induced lung injury because VILI can develop during spontaneous breathing [1]. To support this claim, they reference a classic experimental study from the late 1980s by Mascheroni and colleagues [… read more]
Jon-Emile S. Kenny MD [@heart_lung] “ This is the way the world ends Not with a bang but with a whimper.” -T.S. Eliot As lightly discussed a few months ago, deploying corticosteroids in COVID-19 began, expectedly, with controversy. Russell and colleagues submitted a letter arguing against wholesale administration of corticosteroids in patients infected with SARS-CoV-2. They [… read more]
Jon-Emile S. Kenny MD [@heart_lung] “We’re on a road to nowhere …” -David Byrne Background In early March of this year, Fang and colleagues published a letter noting that patients with diabetes and/or hypertension treated with ACE inhibitors or angiotensin II type-1 receptor blockers [i.e. ARBs] increase their expression of the ACE2 enzyme. Parenthetically, they also stated [… read more]
Jon-Emile S. Kenny MD [@heart_lung] “Knavery and flattery are blood relations.” -Abraham Lincoln Background SARS-CoV-2 is a positive-sense, single-stranded RNA virus with spiked surface glycoproteins emanating from its viral envelope. It is a member of the Coronaviridae family, similar to the first SARS [SARS-CoV] and the Middle East Respiratory Syndrome [MERS]. SARS-CoV-2 preferentially targets respiratory epithelium, [… read more]
Jon-Emile S. Kenny MD [@heart_lung] “This whole thing is not about heroism. It’s about decency. It may seem a ridiculous idea, but the only way to fight the plague is with decency.” -Albert Camus Background In 2013, Dünser and colleagues communicated a rogue viewpoint in shock resuscitation – let us do away with strict macro-hemodynamic goals [… read more]
Jon-Emile S. Kenny MD [@heart_lung] “No facts are to me sacred; none are profane; I simply experiment, an endless seeker with no Past at my back.” -Ralph Waldo Emerson Background When Drs. Marini and Gattinoni author a letter describing a new phenotype of the acute respiratory distress syndrome [ARDS] encountered in patients infected with SARS-CoV-2, we [… read more]
Jon-Emile S. Kenny MD [@heart_lung] with illustrations by Carla M. Canepa MD [@_carlemd_] “…fires had been put out by volunteers using brickmason’s ladders and buckets of water carried in from wherever it could be found, and methods so disorderly that they sometimes caused more damage than the fires.” – Gabriel García Márquez In this second primer [… read more]
Jon-Emile S. Kenny MD [@heart_lung] with illustrations by Carla M. Canepa MD [@_carlemd_] “…but they all had an evasive tremor in their voices and an uncertainty in their eyes that belied their words.” – Gabriel García Márquez Background With early data illustrating upwards of 1 in 5 COVID-19 patients developing acute respiratory distress syndrome [ARDS], there is [… read more]
Jon-Emile S. Kenny MD [@heart_lung] with illustrations by Carla M. Canepa MD [@_carlemd_] “He found a glimmer of hope in the ruins of disaster …” – Gabriel García Márquez Background The coronavirus moniker originates from the appearance of the virus under the electron microscope – protein peplomers radiating from the viral envelope like a crown. Prior [… read more]
Jon-Emile S. Kenny MD [@heart_lung] About a year ago, I explored blood pressure – underscoring mean arterial pressure [MAP] as a determinant, but not necessarily an indicator, of perfusion. The inspiration for that post were these excellent reviews [1, 2] by the legendary Dr. Magder. With the recent 65 Trial [3], a deeper exploration of tissue [… read more]
Jon-Emile S. Kenny MD [@heart_lung] “Sich regen bringt Segen” -German proverb Background It is an overcast day in Bern, Switzerland. I have recently left Zermatt, having had the honour and pleasure of speaking at ‘The Big Sick’ conference. I spent the day roaming the narrowed passages of this old, beautiful city. In the midst of my [… read more]
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