Saturday, August 4, 2012

Vital Signs: Respiratory Rate


There  is  only  limited  research  relating  to monitoring  respiratory  rate,  and  these studies  focused  on  issues  such  as  the inaccuracy of respiratory rate measurement and  respiratory  rate  as  a  marker  for respiratory dysfunction. 

Inaccuracies  in  respiratory  measurement have  been reported in the literature. One study  compared  respiratory  rate  counted using a 15 second count  period, to  a full minute,  and  found  significant  differences in the rates. Respiratory rates measurement in children under five years, for a 30 second  or  60  second  period,  suggesting the 60 seconds resulted in the least variability. 

Another study found that rapid respiratory rates  in  babies,  counted  using  a  stethoscope, were 20% to 50% higher than those counted from beside the cot without the aid of the stethoscope. 



The value of respiratory rate as an indica- tor of potential respiratory dysfunction has been investigated but findings suggest it is of limited value. One study found that only 33% of people presenting to an emergency department  with  a  oxygen  saturation  below 90% had an increased respiratory rate. 

An  evaluation  of  respiratory  rate  for  the differentiation  of  the  severity  of  illness  in babies under  6 months found it  not  to be very useful. Approximately half of the babies  had  a  respiratory  rate  above  50 breaths per minute, thereby questioning the value  of having a "cut-off" at 50 breaths per minute as the indicator of serious respiratory illness. It has also been reported that factors such as crying, sleeping, agitation and age have a significant influence on the respiratory rate. As a result of these and  similar  studies  the  value  of  respiratory rate as an indicator of serious illness is limited.

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