# Heart Rate and Rhythm Changes in Dogs Treated in a Hyperbaric Oxygen Chamber
## 3 Results  
Thirty-four dogs with different health statuses were enrolled in the study. Among them were 11 completely healthy individuals undergoing prophylactic therapy at the request of their owners and 25 individuals with various medical conditions, including neurological problems, skeletal-related conditions, and cardiovascular diseases, as shown in Table 1. The largest group of dogs comprised a mix of breeds (12 dogs): American Staffordshire Terriers (3), Border Collies (3), and Huskies (3). Fifteen males and seventeen females were included in the study. After the qualification examinations, 32 dogs were qualified to participate in the procedure due to the exclusion criteria. Two patients were excluded from the study due to severe arrhythmias. The first involved a Tosa Inu dog with advanced DMVD and tricuspid regurgitation, ascites, and grade III atrioventricular block with slow ventricular action. The second patient, a mixed-breed dog, had fixed bigeminy alternating with trigeminy with premature supraventricular and ventricular origination. The median values and interquartile ranges of the heart rates for the different stages of the procedure are provided in Table 2. During the procedure, a significant decrease in heart rate was observed in group 2 and group 3 (\(p<0.05\)) in a period of 1.5 h of the HBOT period compared to the rest of the periods included in the procedure (30 to the 30-min recording before the start of the procedure, chamber compression, and the decompression period of the chamber). This significance was not observed in group 1. In the same group, there was a significant increase in heart rate during the chamber decompression period (\(p<0.05\)) compared to the rest of the periods of the HBOT procedure (30-min recording before the start of the procedure, HBOT, and chamber compression period). These data are shown in Table 2 and Figure 1. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Group 1** & **Group 2** & **Group 3** \\ \hline N & 6 & 15 & 11 \\ Number of different breeds & 2 & 7 & 6 \\ Age (years) & 13 (4–22) & 9.58 (3–14) & 9.6 (4–14) \\ Body weight (kg) & 14.8 (4–27) & 26.2 (4.4–44) & 17.3 (8–23) \\ Temperature & 38.1 (37.5–38.7) & 38.6 (37.8–39.5) & 38.5 (37.9–39.2) \\ Sex (female/male) & 3:3 & 8:7 & 6:5 \\  & & Elbow joint dysplasia \(n=1\) & \\  & & Hip joint dysplasia \(n=2\) & \\ Health condition & Degenerative mitral valve & Hip joint degeneration \(n=2\) & \\  & disease (6) & Cruciate ligament rupture \(n=2\) & \\  & & Spondylnosis \(n=5\) & \\  & & Ischemic stroke \(n=3\) & \\ \hline \hline \end{tabular} The age and weight of the patients are presented as averages and their minimum and maximum ranges.  
\end{table} 
Table 1: Demographic and health variables of the animals included in groups 1 ( degenerative mitral valve disease), 2 (non-cardiac diseases), and 3 (healthy individuals). \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Variable**} & **Group 1** & **Group 2** & **Group 3** \\  & \(n=6\) & \(n=15\) & \(n=11\) \\ \hline Number of QRS bases (median, IQR) & 4061.5 (3588–4350) & 3603 (2796–4559) & 3973 (3444–4358) \\ \hline Min HR base (median, IQR) & 87 (75–100) & 62 (51–94) & 66 (55–88) \\ \hline Max HR (median, IQR) & 206.5 (204–210) & 205 (154–215) & 201 (195–213) \\ \hline Average HR (median, IQR) & 134.5 (112–145) & 121 (101–153) & 128 (104–135) \\ \hline Number of QRS compressions (median, IQR) & 484 (410–602) & 483 (379–547) & 603 (448–624) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Representation of heart rate variables at each part of the hyperbaric oxygen treatment procedure. Figure 1: Plot showing median and interquartile ranges for all groups (**A**–**C**) and for all individuals included in the study (**D**). (**A**) Degenerative mitral valve disease; (**B**) non-cardiac diseases; (**C**) healthy; (**D**) all individuals. * within a group, values differ significantly (\(p<0.05\)).