Pregnancy
Lara Wijayasiri, Kate McCombe, Paul Hatton, David Bogod in The Primary FRCA Structured Oral Examination Study Guide 1, 2017
Respiratory system: Anatomy: capillary enlargement and mucosal congestion can lead to voice changes and difficulty breathing in some women. The diaphragm is elevated by 4 cm, thoracic circumference increases as the ribs ‘splay’ out and breathing becomes largely diaphragmatic by term.Volumes: FRC reduces by up to 20% and closing volume encroaches on FRC, leading to airway closure and increasing the risk of hypoxia. This is made worse when supine, obese or multiple pregnancy. VT increases but TLC and VC remains unchanged.Ventilation: respiratory rate and minute ventilation increase. Dead space increases due to bronchodilation.Mechanics: chest wall compliance reduces but lung compliance remains unchanged.Oxygen consumption increases: by up to 60%, increasing the risk of developing hypoxia during induction of anaesthesia.ABG: pH increases (to ~7.5), PO2 increases (to ~14 kPa), PCO2 reduces due to hyperventilation (to ~3.5 kPa) and HCO3− reduces (to ~18 mmol/L).
Indoor Air Pollution
William J. Rea, Kalpana D. Patel in Reversibility of Chronic Disease and Hypersensitivity, Volume 4, 2017
Measurements of carbon dioxide levels in a California high school with various ventilation rates were reported by Berks et al.7 Carbon dioxide levels indoors and outdoors were similar (300–500 ppm) in the early morning hours before the occupants arrived. After 7 a.m., as people arrived at the school, the carbon dioxide levels climbed throughout the day until 3 p.m., when the occupants began to leave. The maximum indoor levels recorded during the day were about 1600 ppm with a ventilation rate of 2.5 ft3/minute per occupant. Throughout this study, outdoor levels of carbon dioxide remained fairly constant. After school ended, the indoor carbon dioxide levels fell exponentially back to outdoor levels by 9 p.m. Berks et al.7 also found higher indoor carbon dioxide levels associated with lower forced-ventilation rates. Similar findings were reported by Edgar et al.3 in our studies at the EHC-Dallas. Elevation of carbon dioxide levels occurred particularly in our first ECU where ventilation was not as good as in subsequent units. In these latter ECUs where efficient depollution devices were utilized, elevated carbon dioxide levels appeared to be much less of a problem. Although the presence of CO2 in the environment is normally unobtrusive, we observed that the chemically sensitive do not function well when CO2 levels in the ECU were elevated, even though these levels were not toxic.
Pharmacokinetic/Physiologically Based Pharmacokinetic Models in Integrated Risk Information System Assessments
John C. Lipscomb, Edward V. Ohanian in Toxicokinetics and Risk Assessment, 2016
The U.S. EPA’s compiled biological values (38) were used for all physiological parameters except for alveolar ventilation in the human, which was calculated from the standard U.S. EPA value for the ventilation rate in the human, 20 m3/day, assuming a 33% pulmonary dead space. The partition coefficients for Fischer-344 (F344) rats were taken from Gargas et al. (39), and those for Sprague–Dawley rats were taken from Barton et al. (40). The Sprague–Dawley values were also used for modeling of Wistar rats. Blood/air partition coefficients for the other species were obtained from Gargas et al. (39) and the corresponding tissue/blood partition coefficients were estimated by dividing the Sprague–Dawley rat tissue/air partition coefficients by the appropriate blood/air value.
Particle and inhalation exposure in human and monkey computational airway models
Published in Inhalation Toxicology, 2018
Nguyen Lu Phuong, Nguyen Dang Khoa, Kiao Inthavong, Kazuhide Ito
To simulate the airflow pattern and particle deposition in the human and monkey models, the inspiratory flow rates are needed. According to Fanger (1970), under normal circumstances, the pulmonary ventilation rate is primarily known as a function of the metabolic rate and a proportionality constant. We then selected the representative breathing airflow rate corresponding to the metabolic rate. The type of airflow regime (from laminar–turbulent flow) is also difficult to define due to the complexity of the airway structures. The numerical simulations of realistic human nasal airways reveal a laminar flow regime for flow rates less than 20 L/min (Garcia et al., 2007; Naftali et al., 2005; Schroeter et al., 2008). Kelly et al. (2000) have reported that the laminar flow regime dominates for flow rates around 10 L/min. In this study, steady flow rates of 10, 20 and 30 L/min were used with a prescribed laminar–turbulent flow regime for the human airway. Steady inhalation flow rates of 2.2, 4.6 and 6.9 L/min were applied for the monkey model as representative flow regimes that are similar to the human airway. Further, these flow rates were considered a function of metabolic rate (e.g. light [rest], moderate and intense activity) in accordance with the experimental condition reported by Kelly et al. (2005). The walls of the airway and the turbinate are assumed to be rigid structures. The fluid conditions were specified at the trachea opening, with the velocity perpendicular to the cross-section of the trachea opening and defined using a constant magnitude.
Air pollution and human health risks: mechanisms and clinical manifestations of cardiovascular and respiratory diseases
Published in Toxin Reviews, 2022
Habib Allah Shahriyari, Yousef Nikmanesh, Saeid Jalali, Noorollah Tahery, Akram Zhiani Fard, Nasser Hatamzadeh, Kourosh Zarea, Maria Cheraghi, Mohammad Javad Mohammadi
Good ventilation of homes and better stoves are the keys decrease in emitting smoke from cooking and heating fuels (Vestbo et al.2013, Majeed et al.2020). Based on result, different studies improved stoves can improve indoor air quality (Yorifuji et al. 2016). Using alternative energy sources such as solar cooking and electrical heating is also effective. Using fuels such as kerosene or coal might be less bad than traditional biomass such as wood or dung (Pirozzi and Scholand 2012). Improvements in both air quality and health outcomes are the main advantage of emission control (Yorifuji et al.2016). Combination of controlling the indoor air sources and selecting appropriate ventilation rate (increased to remove remaining pollutants) was the most effective to reduce health risks (Asikainen et al.2016).
Prehospital Airway Management: A Systematic Review
Published in Prehospital Emergency Care, 2021
Nancy Carney, Annette M. Totten, Tamara Cheney, Rebecca Jungbauer, Matthew R. Neth, Chandler Weeks, Cynthia Davis-O'Reilly, Rongwei Fu, Yun Yu, Roger Chou, Mohamud Daya
Research is needed to clarify whether there are situations in which certain airway approaches are superior, in particular in pediatric populations. Ideally, trials would compare all three airway approaches. Studies should clearly identify devices and airway management methods used (e.g., whether adjuncts were used with BVM [OPA, NPA]) to allow for more accurate and direct comparisons of the different airway methods. Research should incorporate objective measures of success in oxygenation and ventilation (e.g., waveform capnography, video monitoring, in-line ventilation rate, flow, tidal volume, and pressure, etc.). Resuscitation time bias remains an important issue in cardiac arrest studies, and efforts should be made to accurately capture airway intervention times to mitigate this concern. Research also is needed to identify optimal methods to acquire and maintain airway management skills in the prehospital setting. Further studies are also needed with regard to the impact of race and sex on the outcomes of different airway management strategies.
Related Knowledge Centers
- Breathing
- Capnography
- Fever
- Stethoscope
- Respiratory Center
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- Pneumograph
- Electrocardiography
- Photoplethysmogram
- Minute Ventilation