Using Infant's Heart Rate as Alternative Marker to Determine Respiratory Infection Severity

Because ARIs are common in infants and can negatively impact their health beyond infancy, simple and objective measures of the level of severity are necessary for clinical management decisions.

Acute respiratory infections (ARIs) in very young children can be both a short and long-term burden for patients, caregivers, and healthcare systems in general. For example, infections of the lower respiratory tract in infants often lead to hospitalization,1 while infections of the larger family of ARIs are frequent causes for ambulatory visits in the outpatient setting.2 The longer-term consequences of ARIs in the very young, particularly lower respiratory tract infections (LRTIs), include an increased risk for recurrent wheeze as these children age, and an increase in the incidence of allergic asthma that can extend into a patient’s late teenage years.3,4

Because ARIs are common in infants and can negatively impact their health beyond infancy, simple and objective measures of the level of [SA1] severity are necessary for clinical management decisions. Such measures have been devised for inpatients, but are impractical outside of a hospital setting. The modified Tal is regarded as the simplest respiratory severity score; however, it requires measuring oxygen saturation in room air by pulse oximetry, referred to as the respiratory severity score-oxygen saturation (RSS-OS). Because this component of the modified Tal can represent a challenge in certain environments, a surrogate marker for this value is needed.

The challenges associated with attaining the RSS-OS prompted a study by Hector P. Rodriguez, PhD, MPH, associate professor of Health Policy and Management and associate director of the new Center for Healthcare Organizational and Innovation Research (CHOIR) at the University of California Berkeley School of Public Health, and his colleagues at the Vanderbilt Center for Asthma Research at Vanderbilt University in Nashville, Tennessee. The study was conducted to assess the utility of substituting the RSS-OS in the modified Tal with a simpler measure, the infant's heart rate (RSS-HR).5 The results were recently published in BMC Research Notes.

Out of a prospective cohort of 674 term healthy children enrolled as infants presenting with acute respiratory illness from the Tennessee Children’s Respiratory Initiative, the study assessed a subset of 497 infants with documented heart rates during an acute respiratory illness.6 The majority of the infants in the subset (85%) had LRTIs and 15% had upper respiratory tract infections (URIs). Similarly, the majority (83%) were inpatients, while 17% were outpatients. The study results were presented as the median RSS-HR and RSS-OS for inpatients and outpatients, as well as for those with LRTIs and UTIs.

These values revealed that both the median RSS-HR and RSS-OS were significantly higher in infants who were inpatients as compared to those who were outpatients. Additionally, the median RSS-HR and RSS-OS were significantly higher in infants with LRTIs as compared to those with URIs. Although these results indicated good agreement between the two scores regarding disease severity, the traditional RSS-OS demonstrated better internal consistency.

By showing that both assessments provided very similar results, Rodriguez et al were able to claim that the RSS-HR can be a plausible substitute for the RSS-OS in the modified Tal. In their own words, Dr. Rodriguez and his colleagues stated, "This usefulness may be especially true in locations where assessment tools like pulse oximetry are not readily available, such as underserved communities and developing/undeveloped countries."

Additionally, Rodriguez et al offered an interpretation of their results by stating, "Our study demonstrated that it may be possible to broaden the applicability of the modified Tal by using an alternative score replacing the factor of oxygen saturation with heart rate." Furthermore, they speculated that, "These findings may have clinical implications, and usefulness in research as it could be used to not only distinguish URI versus LRTI, but also determine the level of acuity of respiratory illness."

The results of this study represent an important addition to the tools available to those investigating ARI disease severity in infants. By providing this alternative measurement, Dr. Rodriguez and his colleagues have essentially transformed the modified Tal, as stated in their research, "This score has the advantage of being ascertained exclusively through physical exam, without the need for additional equipment." Such a finding is significant, as a purely physical exam may be a much more attractive and achievable option for clinicians.

William Perlman, PhD, CMPP is a former research scientist currently working as a medical/scientific content development specialist. He earned his BA in Psychology from Johns Hopkins University, his PhD in Neuroscience at UCLA, and completed three years of postdoctoral fellowship in the Neuropathology Section of the Clinical Brain Disorders Branch of the National Institute of Mental Health.


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  6. Hartert TV, Carroll K, Gebretsadik T, Woodward K, Minton P, Vanderbilt Center for Asthma Research, et al. The Tennessee Children’s Respiratory Initiative: objectives, design and recruitment results of a prospective cohort study investigating infant viral respiratory illness and the development of asthma and allergic diseases. Respirology. 2010;15(4):691—9. doi:10.1111/j.1440-1843.2010.01743.x.