Table 4.
Comparison of HRV parameters between thermoregulatory units
| HRV parameter | Open crib (n = 7) |
Closed incubator (n = 13) |
p |
|---|---|---|---|
| LF power, ms2 | |||
| Before grounding | 161 (94) | 27.9 (7) | 0.003 |
| Grounding | 192 (91) | 74.1 (17) | 0.12 |
| After grounding | 102 (24) | 42.4 (8.1) | 0.036 |
| HF power, ms2 | |||
| Before grounding | 10.2 (4.8) | 4.6 (0.9) | 0.19 |
| Grounding | 16.0 (8.6) | 8.2 (1.4) | 0.5 |
| After grounding | 7.8 (3.0) | 5.3 (0.8) | 0.56 |
| SDNN, ms | |||
| Before grounding | 17.3 (3.4) | 7.6 (1) | 0.001 |
| Grounding | 15.7 (2.8) | 11.2 (1.1) | 0.12 |
| After grounding | 15.9 (1.9) | 9.5 (0.9) | 0.008 |
| Heart rate, bpm | |||
| Before grounding | 155 (3.7) | 160 (3.1) | 0.65 |
| Grounding | 154 (4.4) | 158 (3.2) | 0.82 |
| After grounding | 155 (4.3) | 159 (2.8) | 0.81 |
Values are expressed as mean (SE). Comparison of HRV parameters between 7 infants in open cribs compared with 13 infants in closed incubators with heat on. Independent t tests were done on the natural log-transformed data of all the parameters displayed. p < 0.05 is significant.
LF, low-frequency; HF, high-frequency; HRV, heart rate variability; SDNN, standard deviation of beat-to-beat intervals between normal heart beats.