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Mechanical Properties of the Lungs
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
The functional residual capacity is the lung volume at end-expiration after a normal tidal volume. It is the sum of the expiratory reserve volume and the residual volume. It is the point at end-expiration when the forces acting to spring the chest wall outwards (outward elastic recoil of chest wall) are balanced by forces acting to collapse the lungs inwards (inward recoil of the lungs); muscular tone in the diaphragm is also involved (when this is lost, FRC falls by 400 mL) (Figure 16.6). Less compliant lungs (e.g. pulmonary fibrosis) result in a lower FRC. In emphysema, increased distensibility (due to alveolar damage) results in a higher FRC.
Physiology of the Airways
Published in Anthony J. Hickey, Sandro R.P. da Rocha, Pharmaceutical Inhalation Aerosol Technology, 2019
Anthony J. Hickey, David C. Thompson
Spirometry is the measurement of the volume of air moving into or out of the airways. In this process, various ventilatory maneuvers are undertaken that permit an estimation of pulmonary volumes and capacities (Figure 2.6). Such measurements are valuable for diagnosis of airway disease because pathological conditions can modify specific pulmonary volumes. Definitions of the specific lung volumes are provided in Table 2.4. Measurements of lung volumes are generally normalized for a subject’s body size (weight, height, or surface area), age, and gender. This process permits a comparison with standardized or predicted lung volumes, thereby allowing identification of lung pathophysiologies using a simple procedure. Some examples of the way in which airway disorders alter lung volumes are described in the following. During an episode of airway obstruction (as in asthmatic bronchospasm), expiration of air is difficult, and air becomes trapped in the lower airways. This results in an increase in the residual volume and functional residual capacity and a decrease in vital capacity. In conditions that adversely affect respiratory muscles, such as poliomyelitis or spinal cord injuries, voluntary control of inspiratory or expiratory movement is diminished (or absent) and vital capacity is reduced.
Single Best Answer Questions
Published in Vivian A. Elwell, Jonathan M. Fishman, Rajat Chowdhury, SBAs for the MRCS Part A, 2018
Vivian A. Elwell, Jonathan M. Fishman, Rajat Chowdhury
What causes a reduction in pulmonary functional residual capacity?AsthmaPulmonary fibrosisEmphysemaPneumoniaPulmonary oedema
Functional and structural impairments of the pulmonary system in middle-aged people with cervical and upper thoracic spinal cord injuries
Published in The Journal of Spinal Cord Medicine, 2023
Mattias Hill, Sophie Jörgensen, Gunnar Engström, Margaretha Persson, Per Wollmer, Jan Lexell
IOS assesses the mechanical properties of the pulmonary system. To our knowledge, IOS has not been studied in middle-aged people with SCI.4–6 Two components – resistance and reactance – are included in IOS (cf. Table 1). Our results indicate an increased airway resistance (R5 and R20; cf. Table 1) compared to controls, and the most plausible explanation is a reduced functional residual capacity in people with cervical and upper thoracic SCI.1 Lower functional residual capacity causes a collapse of alveoli and closure of small airways, which leads to an increase in airway resistance.27 In addition, interrupted sympathetic innervation has been hypothesized to cause a greater airway resistance in younger men with tetraplegia.4,7 The differences in airway resistance should be treated with some caution as salbutamol influenced the results of the controls. Salbutamol has been demonstrated to affect R20 more than the variability (decrease 8.3% at 200 µg).28 Thus, it is possible that the difference in R20 is overestimated and, accordingly, the difference in R5-R20 is underestimated.
Targets for obstructive sleep apnea pharmacotherapy: principles, approaches, and emerging strategies
Published in Expert Opinion on Therapeutic Targets, 2023
In control system terminology as related to breathing, the ‘plant’ is the volume of gases stored in the body, including the functional residual capacity of the lungs. The ‘gain’ component is how much a given change in ventilation causes a change in blood gases such as arterial CO2. The ‘CO2reserve’ is the magnitude of increased ventilation that is sufficient to lower arterial CO2 to a threshold beyond which breathing ceases (i.e. the ‘apnea threshold’). A higher plant gain therefore results in smaller increases in ventilation being necessary to lower arterial CO2 beyond the apnea threshold, and unstable breathing results. Such an effect can occur from wakefulness to sleep, for example, when functional residual capacity decreases.
Risk assessment of components in tobacco smoke and e-cigarette aerosols: a pragmatic choice of dose metrics
Published in Inhalation Toxicology, 2021
Peter M. J. Bos, Lya G. Soeteman-Hernández, Reinskje Talhout
The following parameters are used in the approach; default values for these parameters are presented in Table 1. The Tidal Volume (TV) is the volume of air that is inhaled or exhaled during breathing at rest. The volume of air that remains in the lungs at the end of the exhalation phase in rest is called the Functional Residual Capacity (FRC). Default values considered to be average values for an average adult human being are 500 mL for TV and 2 L for FRC. Further, during a breathing cycle, approximately 30% of an inhaled volume of air will not reach the alveoli where gas exchange takes place, i.e. the dead space volume. Default parameter values on human smoking behavior are obtained from Djordjevic et al. (2000). After drawing a puff and one subsequent breathing-cycle, the interval until the next puff is set at 20 sec in smokers. Starting from a breathing-frequency at rest of 12 min−1, a 20-sec interval corresponds to four breathing cycles between puffs. Assuming thirteen puffs per cigarette, the time to smoke a cigarette lasts between 5 and 6 min.