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Physiologic Changes
Published in Vincenzo Berghella, Obstetric Evidence Based Guidelines, 2022
Uterine enlargement and abdominal distension result in a 4- to 5-cm cephalad displacement of the diaphragm and a 5- to 7-cm increase in thoracic circumference. This results in a decrease in expiratory reserve volume, residual volume, and functional residual capacity. There is a compensatory increase in inspiratory capacity, while total lung capacity and vital capacity do not change [14]. Chest wall compliance is increased, but inspiratory muscle strength is preserved with an overall increase in the oxygen cost of breathing [14]. However, it is important to recognize that there is no significant change in the parameters of forced vital capacity, peak expiratory flow rate (PEFR), or forced expiratory volume in 1 second (FEV1) during pregnancy.
Pulmonary Function, Asthma, and Obesity
Published in David Heber, Zhaoping Li, Primary Care Nutrition, 2017
Obesity significantly interferes with pulmonary function by decreasing lung volumes, particularly the expiratory reserve volume (ERV) and functional residual capacity (FRC). Strength and resistance may be reduced as the result of muscle weakness, especially in those with sarcopenic obesity associated with aging. These mechanical limitations lead to inspiratory overload, which increases respiratory effort, oxygen consumption, and respiratory energy expenditure. Body fat distribution significantly influences the function of the respiratory system, likely via the direct mechanical effect of fat accumulation in the chest and abdominal regions, as well as the systemic cytokines released by visceral fat. Asthma and obstructive sleep apnea (OSA) are obesity-associated diseases that involve interactions among environmental, genetic, and behavioral factors.
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
Many of the lung volumes described can be measured by observing ventilation through a simple water volumetric spirometer. The residual volume (RV) (and therefore FRC and total lung capacity) cannot be measured in this way, requiring the use of gas dilution techniques. The volumes given in the following list are average values for adults (Figure 16.5): Functional residual capacity (FRC). This is the 2500 mL of air in the lungs at the end of a normal expiration (when the subject is standing). The FRC is the volume of the lungs at which the elastic outward force of chest wall expansion is balanced by the inward recoil of the lungs; muscular tone in the diaphragm is also involved (when this is lost, FRC falls by 400 mL).Tidal volume. This is a normal resting breath, usually about 500 mL. Tidal volume is measured by spirometry as the volume difference between resting inspiratory volume to the FRC.Inspiratory reserve volume. This is the volume of air that can be inspired over and above the resting tidal volume, and it is normally about 3000 mL.Inspiratory capacity. This is the total volume (3500 mL) that can be inspired from the resting expiratory state from the FRC.Vital capacity. This is the maximal volume (4500–5000 mL) expired after a maximal inspiration.Total lung capacity. This is the total volume (6000 mL) of air in the lungs after a maximal inspiration (this cannot be measured by simple spirometry).Expiratory reserve volume. This is the additional volume (1500 mL) that can be expired at the end of a normal expiration (from the FRC).Residual volume (RV). This is the volume of air (1000–1200 mL) remaining in the lungs after a maximal expiration. RV and FRC cannot be measured by simple spirometry because the lungs cannot be emptied completely after a forced expiration. They can be measured indirectly using a dilution technique involving 10% helium. The helium dilution technique is an excellent technique for the measurement of FRC and RV in normal individuals. In patients with diseased lungs, the helium dilution technique gives a falsely low FRC value because of trapped gas in the lungs. This problem can be overcome by using the body plethysmography technique where the lung volume is determined by applying Boyle's law.
Association of fractional exhaled nitric oxide with asthma morbidity in urban minority children
Published in Journal of Asthma, 2023
Laura Chen, Ilir Agalliu, Adam Roth, Deepa Rastogi
PFTs included spirometry and lung volumes, which were conducted as per ATS guidelines (22,23) on the same clinic visit day as FeNO measurements. For spirometry, percent predicted forced vital capacity (FVC), forced expiratory volume in on second (FEV1), FEV1/FVC and mid-expiratory flow rates, forced expiratory flow at 25–75% (FEF25-75%), based on the National Health and Nutrition Examination Survey (NHANES) reference values (24) and for lung volumes, percent predicted functional residual capacity (FRC), expiratory reserve volume (ERV), residual volume (RV) and total lung capacity (TLC) as well as the RV/TLC ratio, calculated using equations developed by the ATS workshop (25), were included in the analysis. Lower airways obstruction was defined as FEV1/FVC <80% (26).
Pediatric Glittre ADL-test in cystic fibrosis: Physiological parameters and respiratory mechanics
Published in Physiotherapy Theory and Practice, 2021
Ana Carolina Almeida, Renata Maba Gonçalves Wamosy, Norberto Ludwig Neto, Francieli Camila Mucha, Camila Isabel Santos Schivinski
After collecting oscillometry data, spirometry was performed in order to characterize the lung disease. The examination was conducted in compliance with the ATS (Miller et al., 2005), and included the maneuver of slow vital capacity (SVC), followed by forced vital capacity (FVC). The absolute values and percentages of predicted inspiratory capacity (IC), expiratory reserve volume (ERV), forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC ratio and peak expiratory flow (PEF) were considered according to Polgar and Weng (1979), as well as forced expiratory flow at 25%-75% of FVC (FEF25-75%) according to Knudson, Slatin, Lebowitz and Burrows (1976). The data were presented as percentage of predicted according to the Global Lung Initiative (Quanjer et al., 2012).
How to apply the personalized medicine in obesity-associated asthma?
Published in Expert Review of Respiratory Medicine, 2020
Angelica Tiotiu, Marina Labor, Denislava Nedeva, Silviya Novakova, Ipek Kivilcim Oguzulgen, Stefan Mihaicuta, Fulvio Braido
Obesity has direct effects on respiratory function by the reduction of all lung volumes, mainly Functional residual capacity (FRC) and Expiratory reserve volume (ERV), both due to a compression of the thorax by subcutaneous fat over the trunk and the occupation of the thoracic cavity by visceral fat [35]. This leads to a lesser extent of total lung capacity with a normal or mildly restrictive pattern of lung function (with proportional reductions of both Forced expiratory volume in 1s FEV1 and Forced vital capacity FVC) and to increase of respiratory system impedance. Airways responsiveness is increased when lung volumes decreases below normal FRC due to increased airway narrowing and augmented closure of peripheral airways [28]. The greater collapsibility of noncartilaginous small airways at the end of expiration and their cyclical opening/closure during tidal breathing may damage the epithelium inducing a proinflammatory response in the airways [36].