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Prove it: Is it asthma or COPD?

A single prehospital treatment protocol for respiratory distress from asthma or COPD is reasonable


Medic 23 and Engine 16 respond to a private residence for shortness of breath. Both arrive to find a 59-year-old female who says she is having difficulty breathing, which she attributes to a bad cold. Although she has these episodes occasionally, she had a flu vaccination this year to try to keep it from happening again.

The patient is afebrile with a few scattered wheezes that seem to disappear after coughing. Her blood pressure is 136/88 mm Hg, heart rate is 109, respiratory rate is 30 and her room air pulse oximetry value is 91 percent. Her lead II ECG is sinus tachycardia.

The patient reports a history of asthma as a child that continued into adulthood but disappeared after her second child was born 26 years ago. Her mother died in her mid-60s from emphysema.

She says she does not take any regular medications. She once smoked about three packs of cigarettes a month, but quit two years ago.

Firefighters from Engine 16 begin oxygen therapy at 2 lpm via nasal cannula and the patient’s oxygen saturation value climbs to 95 percent. Paramedic Torres administers nebulized albuterol while they prepare for transport.

The patient responds well to treatment during the ride to the hospital. Once there, Torres transfers care to the emergency department staff without any complications.

Torres documents asthma as the primary diagnosis. However, his partner thinks it is early onset emphysema because of her family and smoking history.

Study review
Researchers in Australia sought to determine how accurately paramedics could diagnose acute episodes of asthma or COPD [1]. The researchers included all patients transported by St. John’s Ambulance – Western Australia (STA-WA) during a 12-month period and transported to one of eight hospitals in metropolitan Perth.

For the prehospital diagnosis, researchers searched the electronic patient care report for the appropriate asthma and COPD code, which was entered by the primary paramedic. The ED discharge diagnosis came from a mandatory field in the Emergency Department Information System, which was entered by a member of the ED clinical staff.

Examining the accuracy of paramedic diagnosis of asthma or COPD is a two-step process. First, the researchers had to compare the prehospital diagnosis to the ED discharge diagnoses.

The second step required the researchers to compare the ED discharge diagnosis of asthma or COPD to whatever diagnosis the paramedic made. The second step allowed researchers to find those patients with asthma or COPD that paramedics completely missed.

Results
During the study period, paramedics transported 2,252 patients who met the inclusion criteria. Paramedics diagnosed asthma in 1,117 of those patients, while the remaining 1,135 patients had a diagnosis of COPD.

As expected, the asthma patients were significantly younger (median age 51 vs. 74 years). Twenty percent of the asthma group was under the age of 16 years compared to 10 percent in the COPD group. There was also a significant difference in gender distribution with 57 percent of the asthma group being female compared to only 46 percent in the COPD group.

Patients with a prehospital diagnosis of asthma were more likely to be wheezing when compared to the COPD group (86 percent vs. 55 percent), although the presence of cough, accessory muscle use and the ability to speak were similar between the two groups.

Despite the fact that all patients reported some degree of respiratory distress, paramedics recorded pulse oximetry values for only 93 percent of the patients. Only 88 percent of the patients had a second (or more) pulse oximetry value recorded.

When the information was available, the mean initial pulse oximetry value for the asthma patients was 93 percent while the mean initial pulse oximetry value for the COPD patients was 88 percent. Both groups had significant improvements in pulse oximetry values after the prehospital administration of supplemental oxygen.

There was a significant difference in the use of bronchodilators between the two groups. Paramedics administered a bronchodilator to 89 percent of the asthma patients with a documented wheeze compared to 65 percent of the COPD patients with a documented wheeze.

Three patients with a prehospital diagnosis of asthma died in the emergency department compared to eight deaths in the COPD group.

Despite the fact that 2,252 transported patients met the inclusion criteria, complete emergency department records were available for only 2,115 patients, 1,067 of the group with a prehospital diagnosis of asthma and 1,048 of the group with a prehospital diagnosis of COPD.

To measure the accuracy of the prehospital diagnosis, researchers calculated the positive predictive value (PPV) for both the paramedic diagnosis of asthma and of COPD. The PPV is the probability that a patient with a prehospital diagnosis of asthma (or COPD) really does have asthma (or COPD).

For the 1,067 patients with a paramedic diagnosis of asthma, only 433 patients had an ED discharge diagnosis of asthma, thus giving it a positive PPV of 41 percent. In fact, 19 percent of the patients actually had COPD as the ED discharge diagnosis.

Paramedics were slightly more accurate when it came to diagnosing COPD. For the 1,048 patients with a paramedic diagnosis of COPD, 860 patients had an actual ED discharge diagnosis of COPD, giving it a PPV of 57 percent. Only 4 percent of the patients with a paramedic diagnosis of COPD actually had asthma.

For the second step of the study, researchers identified 2,204 patients with an ED discharge diagnosis of asthma or COPD who were transported by ambulance. Of the 653 patients with an ED discharge diagnosis of asthma, paramedics also diagnosed asthma in 66 percent of the cases.

This statistic is called sensitivity, which means the ability of paramedics to find asthma when it truly exists.

The sensitivity of paramedic diagnosis for COPD was much worse. For the patients with an ED discharge diagnosis of COPD, paramedics also diagnosed COPD in only 39 percent of the cases.

Combining the results from these two examination steps suggests that when paramedics make a diagnosis of asthma, they are correct about 41 percent of the time (PPV). However, in about one-third of the patients who really do have asthma, the paramedics attribute the signs and symptoms to some other condition.

When paramedics make a diagnosis of COPD, they are correct about 57 percent of the time (PPV). However, in about 39 percent of the patients who really do have COPD, the paramedics attribute the signs and symptoms to some other condition.

What this means for you
Respiratory distress is a common prehospital presentation. Asthma and COPD are two of the most common sources of lung disease in the United States [2]. Although both are considered separate diseases, the two conditions may coexist [3].

Some EMS treatment protocols require field personnel to differentiate between asthma and COPD in order to provide treatment [4,5]. Due to the limitations of providing medical care in the field, such as an inability to verify the patient medical’s medical history and limited diagnostic capabilities, this can be a very difficult task.

Other studies of prehospital management of respiratory-related complaints have produced conflicting results regarding diagnostic accuracy. Researchers studying oxygen use in the United Kingdom found prehospital diagnosis was accurate only 32 percent of the time for COPD and 29 percent of the time for asthma [6].

Researchers in Boston found paramedics and emergency department physicians agreed on the diagnosis of patients with dyspnea about 77 percent of the time [7]. However in this study, paramedics were only asked to determine whether the dyspnea was cardiac or non-cardiac related.

Similarly, researchers in New York City found paramedics and ED physicians agreed on the origin of difficulty breathing complaints about 81 percent of the time [8]. Again, the paramedics were only asked to determine whether the complaint had a cardiac, respiratory or other origin.

Researchers in Australia comparing the effects of prehospital administration of high-flow versus titrated oxygen administration to patients with acute exacerbations of COPD found the diagnostic accuracy of paramedics to be 53 percent [9].

Although the causal mechanisms that underlie these two respiratory conditions are different, field treatment for acute exacerbations are similar. Both conditions require oxygen administration if the patient is hypoxemic and both conditions require nebulized bronchodilators if bronchospasm is present.

Given the diagnostic limitations of the field and similarity in prehospital treatment, a single treatment protocol or guidelines for respiratory distress seems reasonable.

Study limitations
One limitation of the current study lies in using the ED discharge diagnosis as the gold standard for asthma and COPD. It assumes that ED physicians can reliably differentiate between these two conditions, an assumption that remains unproven.

ED misdiagnosis has been reported as high as 10 percent [10]. Additionally, the EDIS used here only allows one discharge diagnosis. In some cases, patients may have more than one problem and the asthma or COPD diagnosis was relegated to an unsearched field.

A similar restriction on data entry exists in the prehospital ePCR. The choice of what to enter into the prehospital diagnosis or impression field was left to the paramedic’s discretion, which could affect the accuracy measurement.

For example, if the patient was experiencing an acute exacerbation of COPD caused by a respiratory infection (which is common), the paramedic may have recorded COPD as the diagnosis. Alternatively, the paramedic may have entered respiratory infection, which could lower accuracy rates.

Finally, one threat to the ability to generalize these results lies in the difference in paramedic training in Australia, which generally far exceeds the training required in the United States. To be a paramedic at St. John’s Ambulance – Western Australia, candidates must complete of a three-year university-based training program that awards a baccalaureate degree in paramedicine [11].

It is reasonable to believe paramedics trained in less time might have lower accuracy rates than demonstrated here.

A number of limitations reduce the accuracy of prehospital diagnosis of asthma and COPD. Signs and symptoms associated with the two conditions overlap further impacting diagnostic accuracy. Because field treatment of the two problems is similar, EMS agencies should adopt treatment protocols that focus on symptom management rather than clinical diagnosis.

 

References

  1. Williams, T. A., Finn, J., Fatovich, D., Perkins, G. D., Summers, Q., & Jacobs, I. (2015). Paramedic differentiation of asthma and COPD in the prehospital setting is difficult. Prehospital Emergency Care, 19(4), 535-543. doi:10.3109/10903127.2014.995841
  2. U.S. Department of Health and Human Services. (2012). Disease statistics. Retrieved from www.nhlbi.nih.gov/about/documents/factbook/2012/chapter4#4_5
  3. Kim, S. R., & Rhee, Y. K. (2010). Overlap between asthma and COPD: Where the two diseases converge. Allergy, Asthma, and Immunology Research, 2(4), 209–214. doi:10.4168/aair.2010.2.4.209
  4. Georgia Department of Public Health. (2013). Emergency medical services prehospital clinical operating guidelines. Retrieved from https://dph.georgia.gov/sites/dph.georgia.gov/files/EMS%202013%20clinical%20guidelines_0.pdf
  5. Oklahoma State Department of Health. (2014). State of Oklahoma emergency medical services protocols. Retrieved from https://www.ok.gov/health2/documents/2014%20State%20of%20Oklahoma%20Protocols%20Field%20Edition.pdf
  6. Denniston, A. K., O’Brien, C., & Stableforth, D. (2002). The use of oxygen in acute exacerbations of chronic obstructive pulmonary disease: A prospective audit of pre-hospital and hospital emergency management. Clinical Medicine, 2(5), 449–451. doi:10.7861/clinmedicine.2-5-449
  7. Pozner, C. N., Levine, M., Shapiro, N., & Hanrahan, J. P. (2003). Concordance of field and emergency department assessment in the prehospital management of patients with dyspnea. Prehospital Emergency Care, 7(4), 440–444. doi:10.1197/S1090-3127(03)00214-4
  8. Ackerman, R., & Waldron, R. L. (2006). Difficulty breathing: Agreement of paramedic and emergency physician diagnoses. Prehospital Emergency Care, 10(1), 77–80. doi:10.1080/10903120500366888
  9. Austin, M. A., Wills, K. E., Blizzard, L., Walters, E. H., & Wood-Baker, R. (2010). Effect of high flow oxygen on mortality in chronic obstructive pulmonary disease patients in prehospital setting: Randomized controlled trial. BMJ (Clinical Research Edition), 341, c5462. doi:10.1136/bmj.c5462
  10. O’Conner, P. M., Dowey, K. E., Bell, P. M., Irwin, S. T., & Dearden, C. H. (1995). Unnecessary delays in accident and emergency departments: Do medical and surgical senior house officers need to vet admissions? Journal of Accident and Emergency Medicine, 12(4), 251-254. doi:10.1136/emj.12.4.251
  11. St. John’s Ambulance – Western Australia. (n.d.). Graduate student ambulance officer program. Retrieved from http://www.stjohnchangelives.com.au/assets/templates/main/documents/STJO0841B_web.pdf

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