This month, we received an email from a reader who disagrees with some of the statements made in the August article “Struggling to Breathe: Decision making in the assessment & treatment of acute respiratory distress.” Author Mike McEvoy, PhD, NRP, RN, CCRN, responds to his input and concerns. We also feature comments from readers on Thom Dick’s August column, “Heroes: Are we a little too loosey-goosey with that word?”
I just read the article “Struggling to Breathe” by Mike McEvoy in the August issue of your magazine. I have been involved with EMS for over 30 years and read your magazine on a regular basis. I have also read many articles by Dr. McEvoy that have provided excellent insight into EMS. However, in this most recent article I think he missed the mark in a few areas. First, he states that “shortness of breath, or dyspnea, is a subjective complaint.” From a patient’s standpoint, this may be true since they often use “short of breath” and “trouble breathing” interchangeably. But from a clinician’s standpoint, there’s a very distinct difference. Shortness of breath can also be viewed as a symptom or even a sensation the patient feels and cannot be observed by the clinician. On the other hand, dyspnea (difficult breathing) a sign can be obvious to the healthcare provided as described in the article. I think having shortness of breath and dyspnea casually together in the same sentence leaves the reader the impression they are the same.
Second, on page 53 he states, “Two BLS vital sign measurements that are helpful in assessing and monitoring the degree of respiratory distress are respiratory rate and oxygen saturation.” The article would leave the reader to believe that pulse oximetry is good for monitoring when in fact there are inherent weaknesses (not mentioned in the article) such as the lengthy delay in the drop of a patient’s oxygen saturation—even a patient in respiratory arrest can have a good oxygen saturation for several minutes. A second statement, “Pulse oximetry is an incredibly valuable monitoring tool for patients with acute respiratory distress.” The caveat to that statement is if the patient has good distal circulation, is not cold, has good cardiac output, not a cigarette smoker, not in bright light and does not have finger nail polish on just to name a few. The true measure of a patient’s ability to move air is CO2 not O2.
Third, on page 55 he makes the following statement, “Experts recommend starting CPAP at 8–12 cm of water pressure and gradually increasing the pressure up to 20 cm.” With the ever expanding use of CPAP in the prehospital setting starting CPAP at 8–12 cm H2O could create a compliance issue and may be harmful for some patients, especially those with COPD that may have weak areas in their lungs. In addition, all positive pressure devices reduce cardiac output by reducing pre-load that is why many EMS CPAP protocols start at 5 cm H2O and titrate up as needed to a maximum of 10 cm H2O. Placing a patient on 20 cm H2O will not only reduce cardiac output it will have a negative effect on the work of breathing by making it more difficult to exhale.
Steven C. LeCroy, MA, CRTT, EMTP
Clinical Manager EMS Products
Author Mike McEvoy, PhD, NRP, RN, CCRN, responds: I appreciate the input from Mr. LeCroy and respect his experience. Many clinicians have difficulty separating subjective from objective assessment findings. Using the terms, “shortness of breath” and “dyspnea” in the same sentence was no mistake; they are the same, as also noted by the authors in the opening sentence of the reference I cited. My point to our readers is that subjective information compels the EMS provider to search for objective findings such as the imminent indicators of respiratory arrest, keys indicators of work of breathing and vital signs I describe later. Respiratory assessment is like any other patient exam—you will never find something you don’t look for.
The pitfalls of pulse oximetry are well taken, and points that were actually mentioned elsewhere in the article. While I would certainly agree that capnography is a much better tool than pulse oximetry for assessment of breathing, I described pulse oximetry as a BLS vital sign helpful in assessing and monitoring the degree of respiratory distress, not as the best tool in the box. The points about circulation, body temperature, nail polish, cardiac output and extraneous light raise an important point about keeping your equipment up to date. Over the past 8 years, all of the major pulse oximeter manufacturers have incorporated confidence algorithms into their devices to prevent users from getting erroneous measurements in the presence of low perfusion, motion and extraneous light. Older or sometimes even newer, low budget or generic pulse oximeters were often subject to these interferences. Users should know their equipment and buyers should assure that EMS equipment is updated to reflect advances in technology. The one concern I did mention with modern day (or “next generation”) pulse oximeters is their inability to account for dyhemoglobins (as seen with carbon monoxide poisoning); the ability to “see” dyshemoglobins is limited to presently to only one pulse oximetry device.
Lastly, Mr. LeCroy confirms my statement that there is no standardized approach to initiating CPAP. In an acute care setting, such as an ICU, initiating non-invasive ventilation is an art as much as a science. We are sadly lacking in any substantial research or published consensus papers that could be used to guide prehospital initiation and titration of CPAP. Until we have some good science, prehospital CPAP titration will continue to be guided by local, “best opinion” protocols.
Thank you, Thom, for your insightful and touching article, “Heroes.” My Uncle Walt was a photographer and gunner in B-17s in the European theater. He never bragged, or even spoke of it, until I became a naval flight officer and I got curious and asked. The photographer was in the last aircraft over target with the mission of obtaining "bomb damage assessment." With a gunner's belt to hold them in, they held huge cameras over open holes in the aircraft and snapped away. Now if the first planes may have been able to achieve surprise, the last ones sure didn't, and they were met with all kinds of angry opposition. And yet these men, day after day, mission after mission, crawled into their aircraft and flew out, knowing that they had a very good chance of not coming back. Uncle Walt was a very gentle man, and a gentleman; and he was a real hero.
Bill Blackwell, CDR USN (Ret.), NREMT-I