At a recent EMS refresher, a room full of paramedics professed astonishment that you could do a 15-lead, 18-lead, and yes, even a 24-lead EKG with their cardiac monitor, and many of them had no idea why you should. Nor did they grasp that they could use the capnograph for anything more than looking for “shark fins” or confirming tube placement; that the waveform for your pulse oximeter is called a plethysmograph and can be interpreted to yield valuable clues about the patient’s condition; or for that matter, that a manual BP cuff works just as accurately upside down.
On a class break, one medic, a sales rep lamented, “Man, I can tell you from experience that most medics don’t utilize half the features we have in our monitors. Half don’t care, and the other half just didn’t pay attention during the in-service.”
We’re in an age where most adults carry around in their pockets a smartphone that can access the sum total of human knowledge, with more computing power than the machines we used to put a man on the moon … yet mainly used to text and look at cat pictures. I suppose it’s not surprising, then, that we barely use half the functions of our cardiac monitors.
Here are five ways you can wring more functionality from your cardiac monitor.
1. Use the MAP
It’s no secret that, when we need accuracy the most, NIBP machines are woefully inaccurate. In fact, they may even be as inaccurate as human ears and may overestimate systolic pressures in hypotensive patients by as much as 20%. Yet, the accuracy of NIBP mean arterial pressure is comparable to invasive arterial lines [1]. That’s because NIBP machines actually measure MAP directly, and calculate systolic and diastolic pressure from it.
Ditch the systolic blood pressure, and titrate your treatment efforts to a MAP > 65 mmHg. If you want even greater accuracy, attach monitor leads, pulse oximeter and NIBP cuff on the same patient. Modern prehospital monitors screen those numbers against each other to rule out erroneous readings.
2. Surf the waves
The ECG waveform isn’t the only useful waveform on your monitor. Plethysmography and waveform capnography are useful surrogates for metabolism and perfusion. We all use etCO2 on respiratory patients, but did you know that it is a reliable surrogate for lactate monitoring in sepsis and highly accurate in detecting or ruling out DKA? [2-7].
It can also help identify fluid responsiveness, as can your pulse oximeter plethysmograph (roughly half the hypotensive patients we give fluid bolus to are incapable of increasing their cardiac output with those boluses) [8].
This is a capability that pulse oximeter manufacturers are only beginning to exploit. Masimo’s fingertip pulse oximeter, the Mighty Sat, calculates a Pleth Variability Index, a useful parameter in detecting central hypovolemia and the degree of shock [9-12].
3. Use Your CPR assist features
My agency uses a stopwatch and metronome to ensure high-quality CPR, but the features of the Physio Control Lifepak 15 make it redundant. The monitor screen has a clock with digital seconds display, and an audible CPR metronome. It’s as simple to use as “OK, everybody watch the clock on the monitor. We’re doing compressor switch, rhythm check and defib on the even-numbered minutes, and med pushes on the odd-numbered minutes. At 1:45 of a compression cycle, I’m going to charge the defibrillator and count down to zero … ” And face it, the CPR metronome is much less embarrassing than explaining why the CPR playlist you’re playing from your phone includes “Another one bites the dust” or Drowning Pool’s “Let the bodies hit the floor.”
4. Use your code summary and event recorder more extensively
Make sure your cardiac monitor is synchronized with your dispatch clock, and remind everybody to time-stamp every intervention by pressing the EVENT button on the monitor. We all know what a pain it is to document a resuscitation.
It’s much easier to reconcile times and interventions if everything is printed right there on your Code Summary, and imports directly into your ePCR. You can even configure custom pick lists with specific monitor displays and event options for cardiac arrest, STEMI, DKA, sepsis and so on.
5. Move those electrodes around
As EMS educator Bob Page likes to say in his Multi-Lead Medics course, “Lead II, you’ve got no clue.” Likewise, I’ve heard countless paramedics explain the necessity of a 12-lead by saying, “We’re gonna get a look at your whole heart.”
Actually, you’re not. You’re just getting twelve different views of the left ventricle. If you want to know about the right ventricle, lateral wall of the left ventricle, posterior wall, or highlight atrial activity, you need more leads than 12. Move around to learn more about your patient.
Follow these simple tips, and you can wring a lot more functionality out of your monitor/defibrillator.
References
- Lehman LW, Saeed M, Talmor D, Mark R, Malhotra A. Methods of blood pressure measurement in the ICU. Crit Care Med. 2013 Jan;41(1):34-40.
- Hunter CL, Silvestri S, Dean M, Falk JL, Papa L. End-tidal carbon dioxide is associated with mortality and lactate in patients with suspected sepsis. American Journal of Emergency Medicine. 2013 Jan; 31(1):64-71.
- McGillicuddy DC, Tang A, Cataldo L, Gusev J, Shapiro NI. Evaluation of end-tidal carbon dioxide role in predicting elevated SOFA scores and lactic acidosis. Internal Emergency Medicine. 2009 Feb; 4(1):41-4.
- Soleimanpour H, Taghizadieh A, Niafar M, Rahmani F, Golzari SEJ, Esfanjani RM. Predictive Value of Capnography for Suspected Diabetic Ketoacidosis in the Emergency Department. West J Emerg Med. 2013 Nov; 14(6): 590–594.
- Fearon DM, Steele DW. End-tidal carbon dioxide predicts the presence and severity of acidosis in children with diabetes. Acad Emerg Med. 2002 Dec;9(12):1373-8.
- Gilhotra Y, Porter P. Predicting diabetic ketoacidosis in children by measuring end-tidal CO2 via non-invasive nasal capnography. J Paediatr Child Health. 2007 Oct;43(10):677-80.
- Chebl RB, Madden B, Belsky J, Harmouche E, Yessayan L. Diagnostic value of end tidal capnography in patients with hyperglycemia in the emergency department. BMC Emerg Med. 2016; 16: 7.
- Monnet X, Bataille A, Magalhaes E, Barrois J, Le Corre M, Gosset C, Guerin L, Richard C, Teboul JL. End-tidal carbon dioxide is better than arterial pressure for predicting volume responsiveness by the passive leg raising test. Intensive Care Med. 2013 Jan;39(1):93-100.
- Cannesson M, Desebbe O, Rosamel P, Delannoy B, Robin J, Bastien O, Lehot JJ. Pleth variability index to monitor the respiratory variations in the pulse oximeter plethysmographic waveform amplitude and predict fluid responsiveness in the operating theatre. BJA: British Journal of Anaesthesia, Volume 101, Issue 2, August 2008, Pages 200–206.
- https://www.masimo.co.uk/siteassets/uk/documents/pdf/clinical-evidence/whitepapers/lab3410f_whitepapers_perfusion_index.pdf
- Lu W, Dong J, Xu Z, Shen H, Zheng J. The pleth variability index as an indicator of the central extracellular fluid volume in mechanically ventilated patients after anesthesia induction: comparison with initial distribution volume of glucose. Med Sci Monit. 2014;20:386–392. Published 2014 Mar 8
- http://www.masimo.com/technology/co-oximetry/pvi/
This article, originally published on March 11, 2020, has been updated.
