Total lung capacity

Capacity, total lung (TLC) The volume of gas contained in the lungs at full inhalation. 

TLC See Capacity, total lung or threshold limit concentration. 

Define functional residual capacity, inspiratory capacity, total lung capacity, and vital capacity... 

Total lung capacity (TLC) Total volume of air that can be contained within... 

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. 

Total lung capacity Inspiratory capacity Functional residual capacity... 

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). 

This is a test to assess the degree of airway limitation. It is easy to perform and relatively inexpensive. The patient takes a full inspiration to total lung capacity and then blows out forcefully into the peak flow meter. The best of three recordings are normally taken. The peak flow measures the expiratory flow rate in the first 2 ms of expiration and can overestimate the extent of lung function in patients with moderate to severe airway limitation. Other tests such as... 

Abbreviations QOAD, chronic obstructive airway disease FEFM, forced expiratory flow rate at 50% vital capacity FEFJSJ forced expiratory flow rate at 25% vital capacity FE V forced expiratory volume at Is NR, not reported PEFR, peak expiratory flow rate Raw, airway resistance TLC, total lung capacity. 

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. 

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. ... 

Total lung capacity Volume of gas in lungs at end of maximum inspiration... 

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... 

Total lung capacity Volume in the airways after a maximal inspiration = IRV + TV + ERV + RV... 

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. 

Figure 7 Forced expiratory flow maneuvers in normal and obstructed airways. A maximal expiratory effort from total lung capacity results in a rapid expiration of air from the lungs, the volume of which is equivalent to the forced vital capacity (FVC) and the rate of which is dependent on the caliber of the airways. The volume of air expired in the first second of a maximal expiratory effort is the FEV10. In subjects with obstructed airways, air flow is retarded as reflected in a smaller FEV10 (FEV10ob) than in subjects with normal airways (FEV10).

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