Forced vital capacity

Forced vital capacity (FVC) quantifies the maximum air volume expired following a maximal inspiration and is one of the basic measures of analyzing flow changes such as reduced airway patency observed in asthma. To measure FVC, an individual inhales maximally and then exhales as rapidly and completely as possible. FVC primarily reflects the elastic properties of the respiratory tract. The gas volume forcibly expired within a given time interval, FEV (where t is typically one second, FEVj q)... 

Forced vital capacity (FVC) Maximum forced expired volume following a... 

A suspected diagnosis of COPD should be based on the patient s symptoms and/or history of exposure to risk factors. Spirometry is required to confirm the diagnosis. The presence of a postbronchodilator FEV,/FVC ratio less than 70% [the ratio of FEV, to forced vital capacity (FVC)] confirms the presence of airflow limitation that is not fully reversible.1,2 Spirometry results can further be used to classify COPD severity (Table 12-1). Full pulmonary function tests (PFTs) with lung volumes and diffusion capacity and arterial blood gases are not necessary to establish the diagnosis or severity of COPD. 

Pulmonary function tests (PFTs) indicate decreased forced expiratory volume in 1 second (FEN/,), decreased forced vital capacity (FVC), and increased residual volume. Values are typically worse during acute pulmonary exacerbations. 

Clinical evaluation entailed administration to 45 MPS I patients in a randomized, placebo-controlled clinical trial. The primary efficacy outcomes assessed were forced vital capacity and distance walked in 6 min, both of which were statistically higher relative to placebo after 26 weeks of treatment. The most serious adverse reaction noted was that of a severe anaphylactic reaction in one patient. The most common adverse effects reported were respiratory tract infection, rash and injection-site reactions. The product is manufactured by BioMarin Inc. and is distributed by Genzyme Corporation. 

Spirometry demonstrates obstruction (forced expiratory volume in 1 second [FEVJ/forced vital capacity less than 80%) with reversibility after inhaled P2-agonist administration (at least a 12% improvement in FEVj). Failure of pulmonary function to improve acutely does not necessarily rule out asthma. If baseline spirometry is normal, challenge testing with exercise, histamine, or methacholine can be used to elicit BHR. 

Assessment of airflow limitation through spirometry is the standard for diagnosing and monitoring COPD. The forced expiratory volume after 1 second (FEVj) is generally reduced except in very mild disease. The forced vital capacity (FVC) may also be decreased. The hallmark of COPD is a reduced FEVpFVC ratio to less than 70%. A postbronchodilator LEV, that is less than 80% of predicted confirms the presence of airflow limitation that is not fully reversible. 

Respiratory problems are diagnosed using a spirometer. The patient exhales as hard and as fast as possible into the device. The spirometer measures (1) the total volume exhaled, called the forced vital capacity (FVC), with units in liters (2) the forced expired volume measured at 1 second (FEV,), with units in liters per second (3) forced expiratory flow in the middle range of the vital capacity (FEV 25-75%), measured in liters per second and (4) the ratio of the observed FEVj to FVC X 100 (FEVj/FVC%). 

Draw and label the axes as shown. Next draw a horizontal line at the level of the forced vital capacity (FVC 4500 ml) to act as a target point for where the curve must end. Normal physiology allows for 75% of the FVC to be forcibly expired in 1 s (FEVi). The normal FEVi should, therefore, be 3375 ml. Mark this volume at a time of 1 s. Construct the curve by drawing a smooth arc passing through the FEVi point and coming into alignment with the FVC line at the other end. 

Volume-Time and flow- Volume Curves The characteristics measured by the maximal expiration are forced vital capacity ( o, 1-s forced expiratory volume (FEv,), peak expiratofy flow rate (Vn x)> and flow rates at and 25% of the remaining fvc (Vj . 2 ) for partial and maximal flow-volume curves. These measurements give an easily obtained, relatively reproducible evaluation of overall pulmonary mechanical performance, but provide little information on the mechanisms responsible for an observed change. 

B. Indications and nse Daily administration of Pulmozyme in conjunction with standard therapies is indicated in the management of cystic hbrosis patients to improve pulmonary function. In patients with a forced vital capacity (FVC) >40% of predicted. Daily administration of Pulmozyme has also been shown to reduce the risk of respiratory tract infections requiring parenteral antibiotics. 

Effects noted in study and corresponding doses Nasal irritation (p<0.05), mucosal atrophy (p<0.05), and ulceration (p<0.01), and decreases in spirometric parameters (forced vital capacity, forced expired volume in 1 second, and forced mid-expiratory flow) were observed in workers occupationally exposed to 0.002 mg chromium(VI)/m3 as chromic acid with a median exposure period of 2.5 years. About 60% of the exposed subjects were smokers, but no consistent association between exposure and cigarette smoking was observed. Short-term peak exposures to chromic acid correlated better with nasal septum damage than with 8-hour mean concentrations. 

Abbreviations G, confidence interval CMS, central nervous system EEG, electroencephaologram FVQ forced vital capacity FEV forced expiratory volume in 1 s PE F, forced expiratory flow, pg/ m micrograms per cubic meter NR, not reported ppb, parts per billion Raw, airway resistance SGaw, specific airway conductance VO MAX maximum oxygen uptake. 

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