Tasty Morsels of Critical Care

Welcome back to the tasty morsels of critical care podcast. Today we’re going to have a quick overview of the oesophageal balloon. If you’re directed to a patient in your long case who has an oesophageal balloon in, then you’re probably having a bad day. It would seem very unfair to have too many questions on this but an awareness of their existence and some cliff notes on their basic use might come in handy especially if you’re doing well and you’re in the medal type territory of the exam. Exams aside they’re a useful gateway drug into some important respiratory mechanics that are relevant to all of us. At their most basic these are fancy NG tubes with an inflatable balloon that should end up in the lower third of the oesophagus. Inflating the balloon with a small amount of air allows you to transduce the pressure at the area the balloon lies. While that sounds straightforward there are large sections of review papers dedicated to troubleshooting placement and means of assuring the number you generate is actually accurate. I refer you to the below references for further reading. The pressure measured is called the oesophageal pressure, often abbreviated to Pes because it seems the Americans won the spelling war on that one. Oesophageal pressure is a reasonable surrogate (with assumptions of course) for pressure within the pleural space. Once we have an estimate of pleural pressure we can subtract that from the plateau pressure displayed on the vent and we end up with a fancy number called the transpulmonary pressure. The transpulmonary pressure or Ptp is the distending pressure applied to the lung either from the muscles of spontaneous ventilation or from positive pressure ventilation from the ventilator. Whoopdy do says the examiner – you now have another number you don’t really know what to do with. What should we use this data for, the examiner is asking? Well a short list of useful aspects you can look at with the oesophageal balloon include At this stage you’d be hoping the examiner is satiated and you can move on to something else but in the unlikely and terrifying event that they ask for more detail you might want to mention some of the following. Our typical approach to safe ventilation in the passively ventilated patient is to look at driving pressures and tidal volumes. But this takes no account for the contribution of the chest wall. In the very obese patient there is a lot of flesh pressing down on the chest wall, this leads to an increasingly positive pleural pressure. It would make sense that we would need more pressure to distend the lungs in this scenario. The balloon in this scenario will allow you to set your PEEP appropriately. The Ptp at end expiration needs to sit somewhere in the 0-10cmH20 range to avoid derecruitment and in end inspiration it needs to be less than 25cmH20. This may need a lot more PEEP or less driving pressure than you’re used to giving and the balloon can help you feel safe about doing that. In the patient weaning from the ventilator in a spontaneous mode the oesohpageal balloon can be used to make an estimate of the contribution of the patients muscular effort to the transpulmonary pressure. Your patient may be on 10/5 on a pressure support mode and you may well be lulled into a false sense of security that because the pressure numbers on the vent are modest then the pressures being exerted across the lung are also modest. What we are not measuring in this scenario is the distending pressure being applied to the lungs by the respiratory muscles, the Pmus. The balloon in this scenario can give an estimate of this as it reflects the negative pleural pressure generated by the patients inspiratory efforts allowing us to come up with a Ptp number that takes Pmus into consideration. Sometimes this might encourage you to increase the support from the vent, sometimes this might encourage you to increase the sedation depending on the context. So given all the wonderful things the...

Welcome back to the tasty morsels of critical care podcast. This is the second of 2 parts on PE in critical care. The first focused on risk stratification and this one will focus on management. There is a link to ... Read More »

Welcome back to the tasty morsels of critical care podcast. I haven’t managed to cover PE on the podcast yet. I have been involved in lots of small PE projects over the years and have developed something of an interest ... Read More »

Welcome back to the tasty morsels of critical care podcast. Hypertriglyceridaemua induced pancreatitis came up at a recent trainee presentation and I thought despite it being pretty niche and rare, it’s still common enough that it might be fair game ... Read More »

Welcome back to the tasty morsels of critical care podcast. Today we’re going to try and cover the not insubstantial topic of acute liver failure from Oh’s Manual chapter 44. As you can imagine this will be a superficial skim ... Read More »

Welcome back to the tasty morsels of critical care podcast. Today we look at the other diabetes. We are of course all familiar with the sweet urine of diabetes mellitus but this time we will look at the tasteless or ... Read More »

Welcome back to the tasty morsels of critical care podcast. Following on from the recent post on Heparin, today we’re going to talk about one of its more significant complications – Heparin Induced Thromboyctopaenia or HIT for short. In my ... Read More »

Welcome back to the tasty morsels of critical care podcast. Following on from our initial post in this entirely accidental series on “things you don’t want to find in the chest drain” we turn our eyes (if not our noses) ... Read More »

Welcome back to the tasty morsels of critical care podcast. Today we look at quite a niche topic, that of chylothorax. We are used to many things in the pleural space, like simple fluid or blood or air but the ... Read More »

Welcome back to the tasty morsels of critical care podcast. We’re going to cover a bit of an environmental/tox topic today and look at carbon monoxide poisoning from Oh’s manual chapter 83 on burns. I have previously covered this on ... Read More »

Welcome back to the tasty morsels of critical care podcast. We’ve been talking about pulmonary hypertension, last time we had a pretty broad overview with a focus on group 1 or pulmonary arterial hypertension. This time we’re going to go ... Read More »

Welcome back to the tasty morsels of critical care podcast. This time we’re looking at pulmonary hypertension. Mainly cause I recently had to give a talk on it so it’s fresh in my rapidly diminishing brain cells and thought I ... Read More »

Welcome back to the tasty morsels of critical care podcast. Last time i was butchering my way through a diagnostic approach to hyponatraemia, particularly the forms likely to end up in the critical care end of the hospital. This time ... Read More »

Welcome back to the tasty morsels of critical care podcast. Today we cover an incredibly common inpatient issue – hypnatraemia. We’ll often find 1 or 2 of these in our high dependency unit at any given time, mainly due to ... Read More »

Welcome back to the tasty morsels of critical care podcast. Today we’ll cover some key exam content, all be it not something you’re likely to run into in the ICU too often. The thyroid is a deceptive little organ, tucked ... Read More »

Welcome back to the tasty morsels of critical care podcast. Today we’ll talk about one of the niche and shall I say “advanced” in inverted commas therapies in intensive care practice. ECMO. And to be precise we’ll be talking about ... Read More »

Welcome back to the tasty morsels of critical care podcast. Way back in the way back in tasty morsel number 43 we discussed inotropes and vasopressors but there was a noticeable AHD analogue shaped hole in that post that i ... Read More »

Welcome back to the tasty morsels of critical care podcast. Today we’re going to verge into challenging territory for an audio podcast in that we’re going to the discuss the very visual topic of dynamic LV outflow tract obstruction. This ... Read More »

Welcome back to the tasty morsels of critical care podcast. Following hot on the heels of tasty morsel number 72 on cardio renal syndrome is its partner in nephron injury: hepatorenal syndrome. This gets covered in a sub section of ... Read More »

Welcome back to the tasty morsels of critical care podcast. Today we tackle a somewhat nebulous syndrome. Something we throw around with a few hand wavy explanations but often light on detail. Hopefully in a few minutes you’ll at least ... Read More »