Lungs volumes and capacities

Spirometry is the most widely available and useful PFT. It takes only 15 to 20 minutes, carries no risks, and provides information about obstructive and restrictive disease. Spirometry allows for the measurement of aU lung volumes and capacities except RV, FRC, and TLC and allows assessment of FEVi and FEF25%-7s%. Spirometry measurements can be reported in two different formats—standard spirometry (Eig. 25-2) and the flow-volume loop (Fig. 25-3). In standard spirometry, the volumes are recorded on the vertical (y) axis and the time on the horizontal (x) axis. In flow-volume loops, volume is plotted on the horizontal (x) axis, and flow (derived from volume/time) is plotted on the vertical (y) axis. The shape of the flow-volume loop can be helpful in differentiating obstructive and restrictive defects and in the diagnosis of upper airway obstruction (Fig. 25 ). This curve gives a visual representation of obstruction because the expiratory descent becomes more concave with worsening obstruction. 

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. 

Four primary lung volumes and capacities are usually measured (Fig. 9). Each capacity includes two or more of the primary volumes. The lung volumes and capacities are defined as follows. 

Fig. 9. Primary lung volumes and capacities and how they vary in obstructive or restrictive diseases.

The term volume is used for elemental differences of lung volume, whereas the term capacity is used for combination of lung volumes. Figure 7.3 illustrates the interrelationship between each of the following lung volumes and capacities ... 

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. 

Bullectomy, lung volume reduction surgery, and lung transplantation are surgical options for very severe COPD. These procedures may result in improved spirometry, lung volumes, exercise capacity, dyspnea, health-related quality of life, and possibly survival. Patient selection is critical because not all patients benefit. Refer to the ATS/ERS COPD standards for a detailed discussion of appropriate selection of surgical candidates.1... 

A short-term study of guinea pigs exposed to zinc oxide fume 3 hours/day for 6 days at the threshold limit value (TLV) of 5mg/m revealed pulmonary function changes and morphologic evidence of small airway inflammation and edema. Pulmonary flow resistance increased, compliance decreased, and lung volumes and carbon monoxide diffusing capacity decreased. Some of these changes persisted for the 72-hour duration of postexposure follow-up. 

Lung volumes are changed differently by restrictive and obstructive disease. In restrictive disease most volumes and capacities are decreased to the same extent and the ratio of FEV1/FVC is within the normal range (> 0.8). In obstructive disease FEVi is greatly reduced and the FEVi/FVC ratio is... 

All the static lung volumes and capaeities except FRC and RV can be measured directly through use of a simple spirometer (an apparatus traditionally consisting of a cylindrical bell immersed in water and equipped with outlets that a person can breathe into, or inhale from, to measure expiratory or inspiratory volumes). Functional residual capacity and RV are measured indirectly by using several alveolar gas dilution techniques. 

Lam HF, Peisch R, Amdur MO. 1982. Changes in lung volumes and diffusing capacity in guinea pigs exposed to a combination of sulfur dioxide and submicron zinc oxide mixed in a humidified furnace. Toxicol AppI Pharmacol 66 427-433. 

Complete pulmonary function tests (PFTs), including spirometry, lung volumes, and diffusing capacity, should be obtained in all patients (6). While PFT abnormahties are not specific, documentation of restrictive physiology helps confirm the presence and extent of impairment. Obstructive or mixed physiology can be seen in bronchiolocentric forms of DPLD such as HP, RB-ILD, and sarcoidosis, or in patients with concomitant COPD. 

Pulmonary function tests in both children and adults classically show a restrictive ventilatory defect with reduced lung volumes and diffusing capacities. These abnormalities have been shown to be consistent and sensitive indicators of disease in LIP (43). Gas exchange abnormalities leading to hypoxemia may also... 

LSO (lateral superior olive), 5-11 Lubrication, see Joint lubrication Lungs, 7-1-7-2 and pleural tissues, 7-5 conducting airways in, 7-2-7-4 diffusing capacity, 7-15-7-16 lung capacities and lung volumes, 7-6 lung volumes and gas... 

Decrease in lung capacity, alveolar volume, and diffusing capacity for carbon monoxide values remained depressed for at least 72 h after last exposure. Persistent inflammation of proximal portion of alveolar ducts and adjacent alveoli. 

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. 

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