Thesis
Respiratory response to graded FIO2 exposure in mice
University of Iowa
Master of Science (MS), University of Iowa
Autumn 2023
DOI: 10.25820/etd.006944
Abstract
Chronic intermittent hypoxia, CIH, is widely used in research to examine the physiological effects of sleep apnea. These studies commonly utilize mice as an experimental model. In room air, mice experience periodic apneas and arterial oxygen desaturations (1-3). Activation of the carotid body could stabilize breathing and decrease these events. Therefore, we hypothesized that C57BL/6, CD1, BALB/c, and 129S1 mice will experience fewer arterial desaturation and apnea events with decreasing fractional inspired oxygen (FIO2). We placed mice (5 male, 5 female) between 6 – 12 weeks old from each strain in an Emka® unrestrained barometric plethysmograph and measured pulse oximetry using the STARR LifeSciences MouseOx® Plus system. These mice were exposed to different levels of FIO2 for 10 minutes each: 0.21, 0.15, 0.12, 0.09, 0.30 ± 0.01. We used the American Academy of Sleep Medicine’s (AASM) definition of a desaturation event as a 3% deviation from the average oxygen saturation. An apnea event has previously been defined as a period of suspended breathing lasting 0.5 seconds or longer (2). We found the occurrence of an apnea event was usually followed by a desaturation event at decreasing levels of FIO2. Interestingly, most desaturation events were not preceded by an apnea event, suggesting that an apnea event causes a desaturation but there are desaturation events caused by other factors. Additionally, mice did not show fewer desaturation events when exposed to decreasing levels of FIO2. Actually, mice experienced more desaturation events at low levels of FIO2 (p < 0.001). We did not find a relationship between graded levels of FIO2 and apnea events (p = 0.922). The data demonstrate that most arterial desaturation events occur independent of apneas in mice, suggesting there is another cause for hypoxemia. These conclusions can be used to further investigate the cause of spontaneous desaturation events experienced by mice in room air.
Details
- Title: Subtitle
- Respiratory response to graded FIO2 exposure in mice
- Creators
- Hardik Kalra
- Contributors
- Melissa Bates (Advisor)Michael H. Tomasson (Committee Member)Mark Chapleau (Committee Member)
- Resource Type
- Thesis
- Degree Awarded
- Master of Science (MS), University of Iowa
- Degree in
- Health and Human Physiology
- Date degree season
- Autumn 2023
- DOI
- 10.25820/etd.006944
- Publisher
- University of Iowa
- Number of pages
- vi, 23 pages
- Copyright
- Copyright 2023 Hardik Kalra
- Grant note
- This study was supported by National Heart, Blood, and Lung Institute Grant HL-152365.
- Language
- English
- Date submitted
- 12/03/2023
- Description illustrations
- Illustrations, tables, graphs, charts
- Description bibliographic
- Includes bibliographical references (pages 20-21).
- Public Abstract (ETD)
Chronic intermittent hypoxia, CIH, is widely used in research to examine the physiological effects of sleep apnea. These studies commonly utilize mice as the experimental model. A recent study found that in room air, mice periodically stop breathing (apnea) and their blood oxygen levels drop intermittently (arterial desaturation). Activation of the chemoreceptor reflex which senses chemical composition in the blood could stabilize breathing and decrease desaturation events. Therefore, we hypothesized that C57BL/6, CD1, BALB/c, and 129S1 mice will experience fewer periodic drops in blood oxygen and apnea events with decreasing FIO2. FIO2 (fractional-inspired oxygen) is an estimation of the oxygen content a person or animal inhales. We placed an individual mouse (5 male, 5 female total) from each strain in an Emka® unrestrained barometric plethysmograph and measured blood oxygen using the STARR LifeSciences MouseOx® Plus system. Mice were exposed to different levels of FIO2 for 10 minutes each: 0.21, 0.15, 0.12, 0.09, 0.30 ± 0.01. We defined a desaturation event as a 3% deviation from the average oxygen saturation at each FIO2. An apnea event was defined as a period of suspended breathing lasting 0.5 seconds or longer. We found that in most cases when mice had an apnea event, they experienced a desaturation event within 10 seconds. Interestingly, in most cases when they had a desaturation event it was not because of an apnea event. Additionally, mice did not show fewer desaturation events when exposed to decreasing levels of FIO2. Mice experienced more desaturation events at low levels of FIO2 (p < 0.001). We did not find a relationship between graded levels of FIO2 and apnea events (p = 0.922). These data demonstrate that arterial desaturation events occur independent of apneas in mice, suggesting there is another cause for their hypoxemia. These findings should be used to further investigate the cause of spontaneous desaturation events and apnea events in room air.
- Academic Unit
- Health and Human Physiology
- Record Identifier
- 9984546541202771
Metrics
1 File views/ downloads
33 Record Views