Mr. Taylor A. Teckchandani Profile

Taylor A. Teckchandani

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Proceedings Article | 21 February 2020 Presentation + Paper

The effects of acute hypoxia on heart rate variability parameters

Taylor Teckchandani, Jyotpal Singh, David Mac Quarrie, J. Patrick Neary

Proceedings Volume 11237, 112370F (2020) https://doi.org/10.1117/12.2547898

KEYWORDS: Heart, Hypoxia, Electrocardiography, Oxygen, Carbon monoxide, Biological research, Statistical analysis, Sensors, Amplifiers, Calibration

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We investigated the effects of acute hypoxia on heart rate variability (HRV) parameters during supine rest and moderate-intensity exercise. 27 male (age= 28±11 yr, height= 177±6 cm, mass= 79±9 kg) and 4 female (age= 25±7 yr, height= 169±7 cm, mass= 60±5kg) participants were recruited. Participants rested for 30 minutes in a supine position, after which 5 minutes of isometric squat-stands (0.05 Hz) were performed. This was performed under both normoxic and hypoxic (14.8% oxygen; ~2750m) conditions. Within subject comparisons were made between the last 5 minutes of each supine portion, and between the squat-stand maneuvers at normoxia vs. hypoxia. Depending on normality distribution, a Wilcoxon signed-rank test or a paired sample t-test was used with alpha set at p<0.05. Significant differences in %LF (48±18 vs 56±16), %HF (44±19 vs 35±18), LF/HF ratio (1.8±2 vs 2.3±1), NN₅₀ beats (104±61 vs 82±70), pNN₅₀ (36±22 vs 27±24), SD1 (50±31 vs 42±30), SD2 (101±55 vs 90±46), SD2/SD1 ratio (2.4±1 vs 2.7±1), and % determinism (97±2 vs 98±1) were seen between normoxia and hypoxia, respectively. Significant differences in NN₅₀ (92±26 vs 81±30), pNN₅₀ (21±6 vs 17±7), SD2 (188±60 vs 177±56) and sample entropy (0.3±0.2 vs 0.2±0.1) were also seen during squat-stands between normoxia and hypoxia, respectively. These results suggest changes in physiology and HRV parameters during exposure to acute hypoxia. This research has implications for autonomic function and its influence on cardiac control at altitude.

Proceedings Article | 21 February 2020 Presentation + Paper

Effects of normobaric hypoxia on cardiac mechanical function using seismocardiography

Taylor Teckchandani, David Mac Quarrie, Jyotpal Singh, J. Patrick Neary

Proceedings Volume 11237, 112370E (2020) https://doi.org/10.1117/12.2546378

KEYWORDS: Hypoxia, Oxygen, Electrocardiography, Heart, Computer aided diagnosis and therapy, Statistical analysis, Mechanics, Capillaries

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This study investigated the effects of normobaric hypoxia on mechanical cardiac function during resting and short-term moderate intensity exercise. The cardiac contraction force and ventricular twist of eleven healthy male participants (24±5 years, 176±3cm, 76±9kg) were assessed using seismocardiography (SCG). The SCG was placed superficially to the sternum, 1 cm above the Xiphoid process. An isometric squat-stand maneuver performed at 0.05 Hz for 5 minutes was used as the exercise stimulus. Participants began by resting supine for 30-minutes under normobaric normoxia (712mmHg, 577m, 19.8% oxygen), followed by the squat-stand maneuver. Participants repeated the supine and squat-stand maneuver in a normobaric hypoxic (712mmHg, ~2750m, 14.8% oxygen) environmental simulation chamber. SCG was measured for 30 seconds at the end of normoxic rest (T1), end of normoxic squat-stands (T2), end of hypoxic rest (T3), and end of hypoxic squat-stands (T4). An average of 5 cardiac beats from the SCG were analyzed to determine contraction force and ventricular twist (milligravity, mG). No significant differences were found under resting conditions between T1 and T3 (13±2, 15±3 mG). Furthermore, no significant differences were found comparing squat-stands between normoxia (T2, 35±6 mG) and hypoxia (T4, 45±9 mG), although there were trends showing an increase in contraction force during hypoxia (p=0.2). Ventricular twist mechanics showed similar responses. These results suggest that acute shortduration normobaric hypoxia had no significant effect on the contractility and ventricular twist mechanics of the heart after a moderate-intensity squat-stand exercise. This shows that mechanical cardiac function can be assessed using SCG.

Proceedings Article | 21 February 2020 Presentation + Paper

Cerebral hemodynamic effects of 30-minute supine rest and postural changes at normoxia and hypoxia using near infrared spectroscopy

Jyotpal Singh, Taylor Teckchandani, David Mac Quarrie, J. Patrick Neary

Proceedings Volume 11237, 112370C (2020) https://doi.org/10.1117/12.2544509

KEYWORDS: Hypoxia, Near infrared spectroscopy, Hemodynamics, Chromophores, Oxygen, Nervous system, Prefrontal cortex, Blood, Brain

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We investigated the effects of hypoxia on neurophysiological parameters during rest and moderate intensity exercise to understand cerebral metabolism. 31 male (age= 31±13 yr, height= 177±5 cm, mass= 79±9 kg) and 4 female (age= 25±7 yr, height= 169±7 cm, mass= 60±5kg) participants were recruited. Near-infrared spectroscope (NIRS) was placed over the right prefrontal cortex to measure relative changes in oxy (HbO₂), deoxy (HHb), total (tHb) and hemoglobin difference (HbDiff). Participants rested in a supine position for 30-minutes, followed by a 2-minute washout period before beginning a 10-second squat-stand (0.05 Hz) maneuver for 5 minutes. Thereafter participants repeated the supine and squat-stand protocol in a normobaric environmental chamber (14.8% oxygen; ~2750m). The difference from the last 5 minutes of supine rest was compared to the first 5 minutes in both conditions. The difference between the supine rest vs. squat-stand was compared in both conditions. NIRS standard deviation (SD) was compared during the 30-minutes of supine rest vs. the 5 minutes of squat-stand. A Wilcoxon signed-rank test was use to compare paired samples. Results showed a significant decrease in HbO₂, tHb and HbDiff, a significant increase in HHb at the end of the supine rest in hypoxia vs. normoxia, and an increase in SD of all parameters in hypoxia. For squat-stand, there was a significant decrease in HbDiff and a significant increase in HHb in hypoxia, with a significant increase in SD of all parameters in hypoxia. These results suggest altered cerebral metabolism at altitudes about 2750m during rest and exercise.

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