Fig 1.
A cartoon showing the exposure chamber and the setup of cough recording system.
Arrows point to the flow direction. The signals generated by video camera, microphone, and pressure transducer were collected and digitized continuously through a PowerLab system (ADInstruments Inc.) and recorded into computer files using LabChart 8.0 Pro software (ADInstruments Inc.).
Fig 2.
A screen shot showing our experimental recordings and analyses in real-time in a conscious guinea pig exposed to aerosolized CA.
The symbols (a)—(d) represent four windows in the screen. On the left side, the real-time video monitoring of animal body posture and the list of comments are presented in a- and b-windows, respectively. The channels (Ch) on the right side from the top to bottom are spectrogram (Ch1 in c-window), respiratory flow, sound, accumulated sneeze count/sneeze marker (SM), accumulated cough count/cough marker (CM), cough sound integrated intensity (CSII), cough sound duration (CSD), and respiratory frequency (fR) (Ch2 through Ch8 in d-window). In real-time, SM and CM are manually marked by symbol “*”, while the accumulated sneeze and cough count, CSII, CSD, and fR are automatically calculated and displayed on the screen. Note: the time-scale in c-window is set to 40-fold smaller than that in d-window for a better visual assessment of the cough-related spectrogram. Therefore, the cough spectrogram in c-window is corresponding to the last cough in d-window. The numbers with CM “*” in Ch5 as enlarged in the inset is the comment numbers but not the cough numbers. There are three columns in d-window: the scale and unit of the variable in each channel (left), the signals for each channel (middle), and the name and the value of each channel in real time (right). The lines in Ch5, 6 and 7 (the middle column) present the levels of cough numbers, intensity, and duration of individual coughs, while the values of the accumulated cough numbers, the cough intensity and duration of the last cough are displayed in Ch5, 6 and 7, respectively, of the right column.
Fig 3.
Acoustic analysis of a cough in response to inhalation of aerosolized CA in a conscious guinea pig.
A: The respiratory flow (top, an expiration and its followed inspiration) and waveform of a cough sound (bottom, the shaded part). B: Spectrogram of the cough sound. C: The power spectrum density (PSD) distribution of this cough sound. The power is mainly located in frequencies from 0.5 to 3.5 kHz with a peak around 1.0 kHz. D: The cough sound integrated intensity (CSII, top) and the peak cough sound intensity (PCSI, bottom) are indicated by the cycles; the cough sound duration (CSD) is measured in the top panel.
Table 1.
Characteristics of coughs evoked by aerosol exposure to CA and PGE2.
Fig 4.
Comparison of the cough responses to CA or PGE2 exposures in two conscious guinea pigs.
The traces from top to bottom are air flow (A), sound (B), cough number/cough marker (CM, C), and respiratory frequency (fR, D). Note: the coughs counted manually (with symbol “*”) and those counted automatically in C are perfectly matched for CA-evoked coughs but not for PGE2-evoked coughs because the sound signals in the latter are absent or much smaller than those in the former. Owing to the lack of cough response to vehicle, the relevant data were not shown here.
Fig 5.
Distributions of cough responses to CA (left column for cough numbers) and PGE2 (middle and right columns for cough and bout numbers).
The top and bottom in each column represent raw and group data. Horizontal bars = 10 min delivery of CA and PGE2 aerosol. N = 7 in each group; mean ± SE.
Fig 6.
Acoustic analysis of coughs evoked by aerosolized CA and PGE2.
Typical sound waveforms (top) and spectrograms (bottom) of the coughs evoked by CA and PGE2 are illustrated in A and B, respectively. A: At the top, the dashed lines separate the initial phases from the following phase in response to CA. The arrowheads in the middle panel of the spectrogram point to a series of horizontal bands, while the arrows in the right panel indicate the vertical lines. Note: The scale of the Y-axis at the top of B is different from that of A. B: Group data of sound power spectral densities (PSDs) in which the spots are the individual values of the PSDs (229 and 244 coughs in the CA and PGE2 groups respectively), and the lines with markers represent the averaged values and standard errors. The baseline values of power density (5 data points from each animal) were generated from the sound recordings before the first 5 coughs provoked by CA or PGE2 exposure. Compared to the baseline noise at a given audio frequency, PSDs in response to CA (0.5 to 3.5 kHz, P < 0.01) and PGE2 (0.5 to 2.75 kHz, P < 0.01; and 2.8 to 3.3 kHz, P < 0.05) are significantly higher. Both CA- and PGE2-evoked coughs have peak PSDs located over a range of 0.6 to 2.2 kHz, with the topmost value at approximately 1.0 kHz, but the PSDs at the corresponding frequencies in the PGE2-evoked coughs are much lower than those in CA-evoked coughs. C and D: Comparisons of the peak sound intensity and the integrated intensity between CA and PGE2 groups, respectively. The scattered dots are individual data and the dots with standard error bars are the mean values. The shaded areas indicate the distributions of individual data. All group data from 7 guinea pigs from the CA and PGE2 groups are presented as the mean ± SE. ** P < 0.01, PGE2 vs. CA.
Fig 7.
Ventilatory responses to inhalation of aerosolized CA and PGE2.
The responses of minute ventilation (VE), respiratory frequency (fR), and tidal volume (VT) to CA and PGE2 exposure are presented in the left, middle, and right panels, respectively. N = 7 in each group; mean ± SE. * P < 0.01, compared to baseline values (“100%”) and † P < 0.01 compared to the PGE2-induced responses.