Residual volume , lung

Reductions in expiration flow rate are indicative of bronchial disease, such as asthma or bronchitis. Reductions in FVC are due to reduction in the lung or chest volume, possibly as a result of fibrosis (an increase in the interstitial fibrous tissue in the lung). The air remaining in the lung after exhalation is called the residual volume (RV). An increase in the RV is indicative of deterioration of the alveoli, possibly because of emphysema. The RV measurement requires a specialized tracer test with helium. 

Most lung volumes can be measured with a spirometer except total lung capacity (TLC), functional residual capacity (FRC) and residual volume (RV). The FRC can be measured by helium dilution or body plethysmography. 

After 2 h of ozone exposure, there was a significant change (p < 0.05) in Fvc, KMF, and airway resistance (Raw) Several other measures (feVi, Vjq, and V35) were lower after 2 h of exposure, but the statistical significance was borderline. However, after 4 h of exposure, all flow measures were significantly decreased, compared with controls. After 4 h, increased, FVC decreased further, and feV decreased significantly. Residual volume, functional residual capacity, and total lung volume did not change as a result of the ozone exposure. 

Male Wistar rats exposed to 243 ppm [437 mg/m ] acetaldehyde atmospheres for 8 h per day on five days per week for five weeks showed increases in functional residual capacity, residual volume, total lung capacity and respiratoiy frequency. These changes were interpreted as being caused by damage to the peripheral regions of the lung parenchyma (Saldiva et al., 1985). 

The most common test of lung function in humans is the forced exhalation test, which evaluates both lung volumes and flow performance. After inhaling maximally, the individual exhales as rapidly and deeply as possible to reach residual volume. The volumes of air exhaled per unit time and the airflow during exhalation are recorded. The forced expiratory volume measured in one second (FEVi), along... 

FVC, forced vital capacity FEVi, forced expiratory volume in one second RV, residual volume TLC, total lung capacity Tco, carbon monoxide transfer factor. 

Q8 The majority of the test results support a diagnosis of obstructive pulmonary disease. Chandra s FEVi is greatly decreased and the ratio FEVi/FVC is <0.7, a significant value in determining whether the condition is restrictive or obstructive. A larger residual volume and total lung capacity than normal is typical of obstructive lung disease. 

Q9 Bronchoconstriction, airway oedema and breakdown of alveolar walls all contribute to airflow obstruction. Air cannot be easily moved out of the lung during expiration and becomes trapped in the alveoli and small air passages. The air remaining in the lung following a maximal expiration (residual volume) therefore increases. This extra volume of air contributes to an increase in total lung capacity, and over the years alters both the volume and shape of the chest. 

In 42 solvent inhalers aged 11-31, residual volumes were significantly higher than in 20 controls aged 10-26 lung tissue obtained at autopsy from three inhalers contained microscopic abnormalities similar to those seen in experimental panlobular emphysema (10). 

The term "RV" in the density formula means "residual volume." RV Is the amount of air remaining in the lungs after maximal exhalation. The KV can be measured at the same time as the underwater weighing. A technique for measuring the air... 

In lung function tests, high-dose aerosolized pentamidine (600 mg/month) was associated with an increased pulmonary residual volume, reduced flow rates, and increased airway reactivity (SEDA-18, 291). 

Residual volume (RV) Volume of gas in lungs at end of maximum expiration... 

The approach most commonly used to evaluate effects on distal airways in clinical and occupational medicine is the maximum forced expiratory maneuver, which allows measurement of airflows as a function of lung volume from total lung capacity to residual volume. Typically, the forced vital capacity (FVC) and the forced expiratory volume at 1 s (as a % of FVC) (FEVi) are measured. Peak expiratory flow is a frequently used measure since simple portable devices permit self-evaluation by patients with obstructive disease. Decreased airflow rates are seen with emphysema, chronic bronchitis, and following... 

Peak flow measurements. Perhaps the simplest measurement of expiratory airflow involves the use of a peak flowmeter. Subjects inspire maximally (i.e., to total lung capacity) and expire rapidly and maximally to residual volume into the mouthpiece of the instrument that provides a measurement of the peak expiratory flow. These instruments are simple to operate and often are provided to asthmatic patients for self-measurement and documentation of their ventilatory function. 

For MDIs, lung deposition can be enhanced by (1) gentle exhalation to residual volume rather than to functional residual capacity, (2) slow inhalation (lOL/min) rather that fast inhalation (50L/min), and (3) breath hold of 10 sec rather than none at end of puff inhalation. These observations were based on measurement of urinary albuterol at 30-min postinhalation, which is considered to reflect lung delivery and to avoid gastrointestinal (GI) tract deposition [36], The effect of inhalation flowrate through an aerosol device can greatly affect particle size, a factor that may explain in part the reduced deposition with suboptimal flowrates. Failure to quickly achieve optimal inspiratory flowrate via a budesonide Turbuhaler can result in an increase in size from <6.6 microns to... 

The air in the lung is divided into four compartments tidal volume—the air exhaled during quiet breathing inspiratory reserve volume—the maximal air inhaled above tidal volume expiratory reserve volume—the maximum air exhaled below tidal volume and residual volume—the air remaining in the lung after maximal exhalation. The sum of all four components is called the total lung capacity. 

The air within the lung at the end of a forced inspiration can be divided into four compartments or lung volumes (Fig. 25-1). The volume of air exhaled during normal quiet breathing is termed tidal volume (Vt). The maximal volume of air inhaled above tidal volume is called the inspiratory reserve volume (IRV), and the maximal air exhaled below tidal volume is called the expiratory reserve volume (ERV). The residual volume (RV) is the amount of air remaining in the lungs after a maximal exhalation. 

FIGURE 25-1. Lung volumes and capacities. ERV = expiratory reserve volume FRC = functional residual capacity IC = inspiratory capacity IRV = inspiratory reserve volume RV = residual volume TLC = total lung capacity VC = vital capacity Vj = tidal volume. 

Spirometry measures three of the four basic lung volumes but cannot measure RV (residual volume). RV must be measured to determine the TLC. TLC should be measured anytime there is a reduced VC. In... 

FIGURE 25-5. Maximum expiratory flow-volume curves from patients with fixed obstruction, variable extrathoracic obstruction, and variable intrathoracic obstruction. RV = residual volume TLC = total lung capacity. 

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

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