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Pulmonary Function Testing
Published in Pudupakkam K Vedanthan, Harold S Nelson, Shripad N Agashe, PA Mahesh, Rohit Katial, Textbook of Allergy for the Clinician, 2021
Ekta Kakkar, Flavia CL Hoyte, Devasahayam J Christopher, Rohit K Katial
FVC is the total amount of air exhaled during forced expiration following a deep inhalation. If it is normal, this is an indication that the respiratory muscle strength is intact. In lung function testing, the ratio of FEV1/FVC is used to differentiate between obstructive and restrictive lung disease. Patients with obstructive defects have a disproportionate decrease in FEV1 compared to FVC. This results in a low FEV1/FVC ratio. The American Thoracic Society (ATS) guidelines outline that a FEV1/FVC ratio lower than 70 or 65% in patients over the age of 65, is consistent with obstructive disease. More recent updates consider a FEV1/FVC ratio below the lower limit of normal as diagnostic of obstruction where the lower limit of normal is equal to the 5th percentile in normal, healthy adults (Swanney et al. 2008). In restrictive disease, on the other hand, both FEV1 and FVC are reduced, resulting in a normal or even elevated FEV1/FVC ratio. Restrictive defects cannot be diagnosed by spirometry alone; decreased lung volumes, particularly TLC on a body plethysmography test would be needed to confirm the diagnosis. Table 16.2 below outlines the ways in which PFTs can aid in differentiating between obstructive and restrictive lung disease (Dweik 2011). It is important to note that a patient can have a mixed pattern of both obstruction and restriction.
Metabolic Effects of Exercise on Childhood Obesity
Published in Peter M. Tiidus, Rebecca E. K. MacPherson, Paul J. LeBlanc, Andrea R. Josse, The Routledge Handbook on Biochemistry of Exercise, 2020
Kristi B. Adamo, Taniya S. Nagpal, Danilo F. DaSilva
Available evidence indicates that adolescents with obesity, particularly trunk fat mass, have decreased ventilatory responses compared with their age-matched normal-weight peers, particularly in lung volume and expiratory flow limitation at sub-maximal exercise (76). Furthermore, lung capacities and functional exercise, as measured by the 6-min walk test, are lower in children with obesity compared to non-obese peers (83), and lung function in the paediatric population, measured as the ratio of FEV1 to forced vital capacity (FVC), decreases with increasing BMI (37). This lower FEV1/FVC ratio is driven by a disproportionate increase in FVC vs. FEV1 (60), suggesting that childhood obesity is associated with an imbalance between ventilation and airway flow. Higher cardiorespiratory fitness appears to offer protection and is associated with an improved FEV1/FVC ratio in children with obesity (60).
Pulmonary Function, Asthma, and Obesity
Published in David Heber, Zhaoping Li, Primary Care Nutrition, 2017
Spirometry measurements of lung function in morbidly obese subjects reveal a proportional reduction in forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1), suggesting the occurrence of restrictive lung disease (Carpio et al. 2014; Melo et al. 2014). The FEV1/FVC ratio is generally well preserved or elevated even in morbidly obese individuals, indicating that FEV1 and FVC are affected at the same rate (Wells et al. 1995; Thyagarajan et al. 2008). A reduction in expiratory flows in an obese individual is unlikely to indicate bronchial obstruction unless the flow measurements have been normalized for the reduction in FVC (Salome et al. 2010). In the supine position, the weight of the abdomen in obese individuals causes the diaphragm to ascend into the chest, resulting in the closure of small airways at the base of the lung, and thereby generating an intrinsic positive end-expiratory pressure that results in increased ventilatory work and consequent respiratory muscle impairment (Chlif et al. 2009; Arena and Cahalin 2014).
Changes after 12 years of follow-up severe asthma patients cohort: higher obstruction and comorbidities, but significant better quality of life
Published in Journal of Asthma, 2023
N. G. Santos Jr., R. M. Lima, R. A. Athanazio, R. M. Carvalho Pinto, K. Rabe, A. Cukier, R. Stelmach
In Summary, there was a significant change in FEV1, as functional evolution of patients shows a worsening in the mean FEV1, FEV1/FVC ratio. The newer data of pulmonary functional small airway characteristics show clearly that airways of those severe patients are globally affected. There was a maintenance of higher doses of medications, but the patients were not controlled measured by ACT and ACQ. There was significant reduction in the average of exacerbations and in the daily use of oral corticosteroid. The mean BMI remained the same and the proportion of patients with rhinitis, sinusitis and GERD increased over time, these being the most common comorbidities. A significant reduction both in the eosinophilic and neutrophilic profiles in induced sputum with a lower level of serum IgE and the same values of FeNO was observed. In quality of life, we observed a significant improvement in all domains of St George’s Respiratory Questionnaire (SGRQ) score in 62% of the patients.
Pulmonary functions and associated risk factors among school teachers in a selected Nigerian population
Published in International Journal of Occupational Safety and Ergonomics, 2022
Chidiebele Petronilla Ojukwu, Precious Chinecherem Ogualaji, Stephen Sunday Ede, Rita Nkechi Ativie, Chigozie Okwudili Obaseki, Adaora Justina Okemuo, Franklin Onyedinma Irem
The PFTs were then performed as follows. Each test was performed three times. To assess the FVC, the participants were asked to inhale maximally and then exhale forcefully for at least 6 s. The value of the FVC is read from the spirometer. To assess the vital capacity (VC), the participants were asked to inhale maximally and exhale maximally whether forcefully or not. In healthy subjects, the FVC is equal to the VC. To assess the FEV1, the participants were asked to inhale maximally and exhale forcefully for a maximum of 6 s. The volume of air exhaled after 1 s is read from the spirometer. The FEV1/FVC ratio is calculated from the ratio of the FEV1 to the FVC. This allows the identification of obstructive or restrictive respiratory defects. The maximal flow rate of the subjects during expiration (PEFR) and maximal flow rates between 25 and 75% of the vital capacity (FEF25–75%) were also measured.
Strategies for the prevention, diagnosis and treatment of COPD in low- and middle- income countries: the importance of primary care
Published in Expert Review of Respiratory Medicine, 2021
Foteini M Rossaki, John R Hurst, Frederik van Gemert, Bruce J Kirenga, Siân Williams, Ee Ming Khoo, Ioanna Tsiligianni, Aizhamal Tabyshova, Job FM van Boven
Currently, most standard spirometric reference values are modeled based on HICs data. As the risk factors and subsequent pathogenesis and morphology of COPD is distinct in LMICs, HICs’ values may not apply to all settings. Moreover, race and lifestyle influence lung function, the normal ranges may differ among different ethnicities and countries [26]. For example, it is known that a low FVC can reflect poor lung growth and, as previously mentioned, early-life disadvantages affect lung development [58]. A decreased post-bronchodilator FEV1/FVC ratio (<0.7 or below the lower limit of normal) confirms COPD diagnosis, so in a patient with decreased FVC the ratio may appear normal [20]. We emphasize on the importance of creating and validating diagnostic instruments and having a local reference value for spirometry measurements in order to avoid under- or over-diagnosis of COPD. This requires a better understanding of how COPD differs in these countries. Exploring the etiology and clinical picture will allow for custom and directed diagnostic techniques. Studies determining spirometry reference standards, taking into account the genetic and physiological characteristics for different populations are needed. Initiatives such as the GOLD and the BOLD studies, which aim to advance diagnosis of COPD patients globally and to develop reports and strategies for improving diagnosis, should be further supported and continued.