***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND The powers of the low-frequency ( LF ) and high-frequency ( HF ) oscillations characterizing heart rate variability ( HRV ) appear to reflect , in their reciprocal relationship , changes in the state of the sympathovagal balance occurring during numerous physiological and pathophysiological conditions . However , no adequate information is available on the quantitative resolution of this methodology . METHODS AND RESULTS We studied 22 healthy volunteers ( median age , 46.5 years ) who were subjected after a rest period to a series of passive head-up tilt steps r and omly chosen from the following angles : 15 degrees , 30 degrees , 45 degrees , 60 degrees , and 90 degrees . From the continuous ECG , after appropriate analog-to-digital conversion , a personal computer was used to compute , with an autoregressive methodology , time and frequency domain indexes of RR interval variability . Spectral and cross-spectral analysis with the simultaneously recorded respiratory signal excluded its contribution to LF . Age was significantly correlated to variance and to the absolute values in milliseconds squared of very-low-frequency ( VLF ) , LF , and HF components . The tilt angle was correlated to both LF and HF ( expressed in normalized units [ nu ] ) and to the LF-to-HF ratio ( r = .78 , -.72 , and .68 ; respectively ) . Lower levels of correlation were found with HF ( in ms2 ) and RR interval . No correlation was present between tilt angle and variance , VLF , or LF ( in ms2 ) . Individual analysis confirmed that the use of nu provided the greatest consistency of results . CONCLUSIONS Spectral analysis of HRV , using nu or LF-to-HF ratio , appears to be capable of providing a noninvasive quantitative evaluation of grade d changes in the state of the sympathovagal balance Traditional approaches to measuring the complexity of biological signals fail to account for the multiple time scales inherent in such time series . These algorithms have yielded contradictory findings when applied to real-world data sets obtained in health and disease states . We describe in detail the basis and implementation of the  multiscale entropy ( MSE ) method .  We extend and elaborate previous findings showing its applicability to the fluctuations of the human heartbeat under physiologic and pathologic conditions . The method consistently indicates a loss of complexity with aging , with an erratic cardiac arrhythmia ( atrial fibrillation ) , and with a life-threatening syndrome ( congestive heart failure ) . Further , these different conditions have distinct MSE curve profiles , suggesting diagnostic uses . The results support a general " complexity-loss " theory of aging and disease . We also apply the method to the analysis of coding and noncoding DNA sequences and find that the latter have higher multiscale entropy , consistent with the emerging view that so-called " junk DNA " sequences contain important biological information BACKGROUND An intensive hybrid program , combining constraint with bimanual training , improves upper extremity function as well as walking endurance of children with unilateral cerebral palsy ( UCP ) . Endurance improvement may be associated with the cardiac autonomic regulation system ( CARS ) adaptation , known to be impaired among these children . OBJECTIVE To examine the influence of an intensive hybrid program on CARS , walking endurance and the correlation with upper extremity function of children with UCP . METHODS Twenty-four children aged 6 - 10 years with UCP participated in a hybrid program , 10 days , 6 hours per day . Data were collected pre- , post- and 3-months post-intervention . Main outcome measures included the Polar RS800CX for heart rate ( HR ) and heart rate variability ( HRV ) data , the 6-Minute Walk Test ( 6MWT ) for endurance , and the Assisting H and Assessment ( AHA ) and Jebsen-Taylor Test of H and Function ( JTTHF ) for bimanual and unimanual function . RESULTS A significant reduction in HR and an increase in HRV at post- and 3-month post-intervention was noted ( χ22= 8.3 , p = 0.016 ) along with a significant increase in 6MWT with a median increase of 81 meters ( χ22= 11.0 , p = 0.004 ) at the same interval . A significant improvement was noted in unimanual and bimanual performance following the intervention . CONCLUSIONS An intensive hybrid program effectively improved CARS function as well as walking endurance and upper extremity function in children with UCP ( 213 ) Background Respiratory rate ( RR ) is an important vital sign which is strongly correlated with in-hospital mortality . At the same time , RR is the most likely vital sign to be omitted when assessing a patient . We believe that one reason for this could be the difficulty in measure the RR , since it is not read off a monitor , but counted manually . Also there is the possibility of assessment bias and the inter-observer reliability becomes important . We therefore set out to investigate how the nursing staff counting the actual number of respirations per minute would agree with the nursing staff using a predefined ordinal scale . Methods For this prospect i ve study , we recorded five videos of  a young healthy man breathing approximately 5 , 10 , 15 , 30 and 60 times per minute . The videos were shown in a r and om order to a suitable sample of the nursing staff . The participants were r and omized into two groups ; one to count the exact number of breaths per minute , and one to use a predefined ordinal scale . Results Comparing the exact number of breaths per minute , the Intra Class Coefficient ( ICC ) was 0.99 ( 95 % CI : 0.97–1.00 ) . Comparing the RR using the predefined scale , the overall Kappa Fleiss Coefficient was 0.75 . Conclusions The inter-observer agreement was high when comparing the use of the actual number of breaths per minute and substantial when comparing the use of the predefined scale . This is the largest inter-observer study on RR to date . However , further studies on the use of scaled comparisons of RR are needed Spectral estimates of heart rate variability ( HRV ) often involve the use of techniques such as the fast Fourier transform ( FFT ) , which require an evenly sample d time series . HRV is calculated from the variations in the beat-to-beat ( RR ) interval timing of the cardiac cycle which are inherently irregularly spaced in time . In order to produce an evenly sample d time series prior to FFT-based spectral estimation , linear or cubic spline resampling is usually employed . In this paper , by using a realistic artificial RR interval generator , interpolation and resampling is shown to result in consistent over-estimations of the power spectral density ( PSD ) compared with the theoretical solution . The Lomb-Scargle ( LS ) periodogram , a more appropriate spectral estimation technique for unevenly sample d time series that uses only the original data , is shown to provide a superior PSD estimate . Ectopy removal or replacement is shown to be essential regardless of the spectral estimation technique . Resampling and phantom beat replacement is shown to decrease the accuracy of PSD estimation , even at low levels of ectopy or artefact . A linear relationship between the frequency of ectopy/artefact and the error ( mean and variance ) of the PSD estimate is demonstrated . Comparisons of PSD estimation techniques performed on real RR interval data during minimally active segments ( sleep ) demonstrate that the LS periodogram provides a less noisy spectral estimate of HRV Paced breathing is a frequently performed technique for cardiovascular autonomic studies . The relative timing of inspiration and expiration during paced breathing , however , is not consistent . We , therefore , examined whether indexes of heart rate variability and spontaneous baroreflex sensitivity would be affected by the respiratory time ratio that is set . We studied 14 healthy young adults who controlled their breathing rates to either 0.1 or 0.25 Hz in the supine and sitting positions .  Four different inspiratory-to-expiratory time ratios ( I/E ) ( uncontrolled , 1:1 , 1:2 , and 1:3 ) were examined for each condition in a r and omized order . The results showed spectral indexes of heart rate variability and spontaneous baroreflex sensitivity were not influenced by the I/E that was set during paced breathing under supine and sitting positions . Porta 's and Guzik 's indexes of heart rate asymmetry were also not different at various I/E during 0.1-Hz breathing , but had larger values at 1:1 during 0.25-Hz breathing , although significant change was found in the sitting position only . At the same time , Porta 's and Guzik 's indexes obtained during 0.1-Hz breathing were greater than during 0.25-Hz breathing in both positions . The authors suggest that setting the I/E during paced breathing is not necessary when measuring spectral indexes of heart rate variability and spontaneous baroreflex sensitivity under the conditions used in this study . The necessity of paced breathing for the measurement of heart rate asymmetry , however , requires further investigation 
    Output:
    
Pediatric patients with CP presented a significantly higher resting heart rate and reduced HRV , different autonomic responses to movement stimuli compared to children with normal development , but also reduced HRV parameters in the children dependent on adult assistance for mobility compared to those generally independent .