Changes in Cardiac Autonomic Regulation after Acute Lung Exposure to Carbon Nanotubes: Implications for Occupational Exposure

Figure 4

Differences in the frequency domain indexes of heart rate variability obtained by computing the power spectral density (see Section 2 for the details) in response to acute instillation of, respectively, PBS (control group) and SWCNTs (experimental group). LFn: low frequency values expressed in normalized units; HFn: high frequency values expressed in normalized units; VLFn: very low frequency values expressed in normalized units; LFn/HFn: the ratio of normalized low-frequency (LF) to high-frequency modulation (HF) of the RR intervals which is considered to be an indirect marker of the sympathovagal balance (LFn/HFn).