Lung volumes capacity

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... 

The four standard lung capacities consist of two or more lung volumes in combination (see Figure 17.4) ... 

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. 

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. 

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). 

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... 

Recent work with insulin provides evidence that the total lung volume at the end of the delivery impacts the kinetics of absorption of this peptide delivery of fine particle insulin aerosol resulted in faster absorption with a higher plasma peak level in humans when the inhalation was done with a deep breath (close to vital capacity), as compared with a more shallow breath (about 50% of the vital capacity).The kinetics following the latter was similar to subcutaneous absorption of insulin. The exact reasons for this observation are unknown. However, the lung does have the above-described water channels that could expand during breathing. If the size of the peptide or protein molecule approaches the diameter of these channels, it would be expected that the channel expansion would lead to faster absorption. For molecules whose size exceeds the channel diameter, the lung volume does not play a role in their pulmonary absorption rate. ... 

Static lung volumes Vital capacity Maximum volume that can be expelled from the lungs by forced effort following maximum inspiration... 

Functional residual capacity (FRC) Volume of gas remaining in lungs at end of tidal expiration... 

Figure 4 Capacities and lung volumes of the lung. (Adapted from McClellan RO and Henderson RF (eds.) (1989) Concepts in Inhalation Toxicology, p. 364. New York Hemisphere, with permission.)...

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... 

Lung volumes can be determined by spirometry and reflect the volume of air remaining in the airways after various inspiratory or expiratory maneuvers. Lung capacities encompass two or more lung volumes (as shown by the provided formulas). 

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. 

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. 

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