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Logo of nihpaAbout Author manuscriptsSubmit a manuscriptHHS Public Access; Author Manuscript; Accepted for publication in peer reviewed journal;
 
J Pediatr. Author manuscript; available in PMC 2017 August 1.
Published in final edited form as:
PMCID: PMC4981540
NIHMSID: NIHMS782807

Count on it! Accurately measured respiratory rate is associated with lung function and clinical severity in children with acute asthma exacerbations

The physical exam exemplifies the confluence of art and science in pediatric practice. The wisdom of Sir William Osler holds true in our contemporary world of vast medical technology: “The whole art of medicine is in observation” (1903).1 The pulmonary exam is emblematic of this teaching, particularly in the child with an acute asthma exacerbation in whom formal measures of lung function are generally not available and in whom physical assessment of exacerbation severity and response to treatment will determine subsequent treatment and hospitalization decisions.2

Laennec deserves recognition for both invention of the stethoscope (1816) and advancing physical examination of the chest.3 Importantly, this exam begins with accurate assessment of respiratory rate (RR), a vital sign that is widely accepted as a window into the respiratory system in health and disease, yet is frequently neglected.4

We sought to examine whether RR is associated with three different measures of lung function and acute asthma disease severity–%-predicted total airway resistance (R5) by impulse oscillometry (%IOS), %-predicted forced expiratory volume in 1-second (%FEV1), and the Acute Asthma Intensity Research Score (AAIRS).5 The AAIRS comprises 7 physical signs, is scored 0 – 16 points (16 most severe) and does not include respiratory rate.

We performed a secondary analysis of data from a prospective study of children ages 5–17 years with acute asthma exacerbations.6 RR was measured for a 60 second interval with each participant on room air, at rest, supine and with the head of the bed elevated to approximately 30 degrees. AAIRS components were recorded individually and the total score calculated electronically in the study database. After the pulmonary examination, participants attempted impulse oscillometry for %IOS followed by spirometry for %FEV1 in accordance with American Thoracic Society (ATS) standards.7

Among 933 participants, median [IQR] age was 8.8 [6.9, 11.2], 551 (59%) were African-American, 569 (61%) were male, RR was 26 [22–31], %FEV1 in 553 participants who were able to perform spirometry meeting ATS acceptability criteria was 50% [36–71%].8 %IOS was 161% [123–214%, n=187] and AAIRS 5 [2–7, n=933]. In multivariable regression models adjusted for age, sex and race, RR was associated with %FEV1 (β-coefficient −1.7, 95%CI −2.0, −1.4), %IOS (β 2.9, 95%CI 1.3, 4.5) and the AAIRS (β 0.25, 95%CI 0.23, 0.28) (Figure).

Figure
Linear regression of %FEV1 (left panel), %IOS (middle) and AAIR Score (right) on respiratory rate. Grey bands represent 95% CI.

One of the fundamental components of the physical examination, simple observation of respiratory rate, continues to inform care of the acutely ill patient. Although respiratory rate does not replace %FEV1, %IOS or comprehensive severity scores when these are available, clinicians can readily distinguish a patient breathing at the median respiratory rate of our cohort (26) from one breathing at the lower or higher bounds of the IQR [22, 31] to estimate acute asthma exacerbation severity. As such, accurately measured respiratory rate is an additional domain of assessment to inform management of children with acute asthma exacerbations.

Acknowledgments

Supported by the National Institutes of Health (K23 HL80005 [D.A.], K24 AI77930 [T.H.], and Ul1 RR024975 [Vanderbilt Clinical and Translational Science Awards]).

Abbreviations

AAIRS
Acute Asthma Intensity Research Score
ATS
American Thoracic Society
FEV1
Forced expiratory volume in 1-second
IOS
Airway resistance by impulse oscillometry

Footnotes

Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

The authors declare no conflicts of interest.

Contributor Information

Donald H Arnold, Department of Pediatrics, Division of Emergency Medicine, Vanderbilt University School of Medicine, Nashville, TN. Center for Asthma Research, Vanderbilt University School of Medicine, Nashville, TN.

Cody Penrod, Department of Pediatrics, Division of Emergency Medicine, Vanderbilt University School of Medicine, Nashville, TN.

Daniel J Sprague, Department of Chemistry, Vanderbilt University, Nashville, TN.

Tina V Hartert, Department of Medicine, Division of Allergy, Pulmonary, and Critical Care Medicine, Nashville, TN. Center for Asthma Research, Vanderbilt University School of Medicine, Nashville, TN.

BIBLIOGRAPHY & REFERENCES CITED

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6. Arnold DH, Gebretsadik T, Abramo TJ, Sheller JR, Resha DJ, Hartert TV. The Acute Asthma Severity Assessment Protocol (AASAP) study: objectives and methods of a study to develop an acute asthma clinical prediction rule. Emergency Medicine Journal. 2012;29:444–450. [PMC free article] [PubMed]
7. Standardization of Spirometry, 1994 Update. American Thoracic Society. American Journal of Respiratory and Critical Care Medicine. 1995;152(3):1107–1136. [PubMed]
8. Lung function testing: selection of reference values and interpretative strategies. American Thoracic Society. Am Rev Respir Dis. 1991;144:1202–1218. [PubMed]