Forced expired volume

FIGURE 5.21 Representative spirogram (top) and flow-volume curve (bottom) during forced expiration. FEV o shown in the spirogram corresponds to the arrow in the flow-volume curve indicating forced expired volume in one second. 

Forced expired volume (FEV,) Gas volume forcibly expired within the time... 

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

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%). 

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. 

IIIC)]. A study of children enrolled in the longitudinal cohort study, the Tucson Children s Respiratory Study (USA), showed that RSV lower respiratory tract infections before 3 years were associated with an increased risk of infrequent wheeze, and frequent wheeze at age 6. Risk decreased with age and was not observable at age 13. RSV lower respiratory tract infections were also associated with lower forced expired volumes, but there was no difference after inhalation of salbutamol [154(IIIC)]. 

FIGURE 3. Correlation of ascorbic acid concentration in plasma and the relation of applied FEV, (forced expiration volume) and optimal FEV,. 

Forced expiration is commonly used to assess pulmonary function in both healthy and impaired individuals. Static measures of lung volumes (TLC, Vj, FRC) fail to detect dynamic changes in pulmonary function that are attributable to disease (e.g., asthmatic airway constriction). Obtaining maximum expiratory flow-volume (MEFV) curves (Fig. 5.21) permits derivation of key parameters in detecting changes in lung function. 

FEV, forced expiratory volume in the first second of expiration MDI, metered-dose inhaler PEF, peak expiratory flow. 

The volume of gas that remains in the lungs after a maximal forced expiration (ml). 

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. 

C asthmatic (5 men and S wmen, aged 18-25) 0 0,0.8, or 1.8 45 min (15 min exercise, 15 min nest, 15 min exercise) No treatment related effects, including increase in severity of upper respiratory lower respiratory, other symptoms no significant differences between treated and control groups in pulmonary function tests (total respiratory resistance, thoracic gas volume at functional residual capacity, forced expiratory volume, forced viral capacity, maximal flow at 50% and 75% of expired vital capacity) no changes in nasal power data between treated and control groups Stevens et al. 1992... 

The Navy s proposed SEAL 2 for exposure to sulfur dioxide is 6 ppm. The Navy did not describe how it derived this SEAL, although it could have been derived from a study by Andersen et al. (1974), who exposed 15 males at 1,5, and 25 ppm for 6 h, and observed a significant decrease in nasal mucous flow rate and an increase in nasal airflow resistance in subjects exposed at 5 and 25 ppm for 6 h. A decrease in forced expiratory volume at 1 s and in forced expiratory flow during the middle half of expired flow volume was observed in the subjects exposed at all concentrations. 

Forced vital capacity (FVC) measures the maximum volume of air expelled from the lung in a single forced expiration there is no time limit. Forced expiratory volume in one second (FEVi) measures the volume of air which can be expelled from the lung in one second. In a normal individual 80% of the vital capacity can be expired in one second, but patients with obstructive disease have difficulty in emptying the lung and this value is significantly reduced. 

Forced expiratory flow measurements. Spirometric techniques are used to measure the time course of expired volumes. The same ventilatory... 

The combinations or sums of two or more lung volumes are termed capacities (see Fig. 25-1). Vital capacity (VC) is the maximal amount of air that can be exhaled after a maximal inspiration. It is equal to the sum of the IRV, Vt, and ERV. When measured on a forced expiration, it is called the forced vital capacity (FVC). When measured over an exhalation of at least 30 seconds, it is called the slow vital capacity (SVC, VC). The VC is approximately 75% of the total lung capacity (TLC), and when the SVC is within the normal range, a significant restrictive disorder is unlikely. Normally, the values for SVC and FVC are very similar unless airway obstruction is present. 

Another test used to distinguish upper airway obstruction from COPD and asthma is the FEVi/FEVq.s (FEV at 1 second/FEV at 0.5 second). This ratio is usually greater than 1.5 in patients with upper airway obstruction. This is so because the FEV0.5 is proportionately more reduced in upper airway obstruction because forced expiration measured at 0.5 second better reflects obstruction at high lung volumes. The abnormahty seen on the flow-volume loop has been referred to as straightening of the curve during early expiration. 

Residual volume (RV) The volume of gas remaining in the lung at the end of the most forceful expiration. 

A second way of looking at forced expiration is with a maximum expiratory flow-volume (MEFV) curve, which describes maximum flow as a function of lung volume during a forced expiration (Fig. 12). In healthy human subjects, flow rates or flow-volume curves reach a maximum and will not increase with additional effort after the lungs have emptied 20-30% of their volume (Fry and Hyatt, 1960). This phenomenon of flow limitation is due to airway compression over most of the lung volume. Thus, flow rate is independent of effort and is determined by the elastic recoil force of the lung and the resistance of the airways upstream of the collapse point. In obstructive diseases of the lung this curve is shifted to the left, whereas restrictive diseases shift the curve in the opposite direction (also shown in Fig. 12). 

Chest. Is there superficial chest wall trauma, tenderness, crepitation, dullness, or hyperresonance Are crackles present This measurement should be made by asking the patient to hold a forced expiration at residual volume for 30 seconds, then listening carefully at the lung bases for inspiratory crackles. Is wheezing present This examination should be undertaken by listening for wheezes bilaterally in the chest both posteriorly and anteriorly under circumstances of forced expiration. 

Volume of gas exhaled over a given time interval during a complete forced expiration... 

FIGURE 21.13 Spirometer volume-time tracing typical of spirometry during forced expiration. In this representative test, the FEVl is 3.64 L and the FVC is 4.73 L. 

Forced expiratory volume-1 second (FEVf)—The volume of air that can be forcibly expelled during the first second of expiration. 

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