Biophysical Factors Inherent in Heart Rate Variability of Rats During Cooling and Re-Warming
Abstract
Variations in interbeat interval (IBI) determined from the ECG of telemetry-equipped rats were evaluated as markers of physiological status during hypothermia and re-warming. Animals were cooled to a core temperature (T(sub c)) of 19-20 deg C, maintained there for 30 min, and then re-warmed. Out of 19 hypothermia inductions, 14 were successfully re-warmed (S), and 5 were unsuccessfully re-warmed (U.S.). ECG and T(sub c) data were collected for 10 sec every 5 min. Six 10 sec strips were combined into blocks: Block 1- start of cool, Block 2- midway through cooling, Block 3- coldest period, and Block 4- end of 4 rewarming. Lorenz plots of IBI's in Blocks 1-4 demonstrated markedly increased IBI values with coldest T(sub c's) in Block 3; U.S. exhibited greater scatter in Block 3 than S. NSD (normalized standard deviation) of Block 1 was lower (p < 0.05) than any other Block for both S and U.S. trials. NSDs in U.S. trials were higher (p < 0.005) than for S for Blocks 1-3. Other time domain measures (SDSD and RMSSD) showed significant differences between S and U.S. rats in Block 3 only. This study in time domain analyses indicates that NSD may be the most useful in predicting fatal hypothermia when compared to RMSSD and SDSD.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 2002
- Accession Number
- ADA405122
Entities
People
- Amy M. Bastille
- Candace B. Matthew
- Ingrid V. Sils
- Richard R. Gonzalez
Organizations
- United States Army Research Institute of Environmental Medicine