Taking into consideration the variations in airways resistance between inspiration and expiration, it is easy to conclude that different types of VC are not equal. The differences between the four types of VC are minimal in those with no ventilatory defect [ 61 ]. In OLD, formation of flow limiting segments occurs early due to narrowing of airways. IC can directly be measured by spirometry, which is advantageous in places where there are no facilities to measure RV and TLC. There are accumulating evidences that indices derived from IC are helpful to assess severity, prognosis and response to treatment of many OLD [ 66 — 69 ].
This fact is further supported by the finding of French et al. Likewise, lung hyperinflation secondary to air trapping can be estimated by calculating the difference between lung volumes measured by plethysmography and dilutional techniques. This assumption was validated by Tantucci et al. The results confirmed that comparing FRC pl with FRC He was helpful in identifying asthmatic patients at risk of tidal airway closure induced by methacholine.
In addition, Tantucci et al. Typical changes in the static lung volumes and capacities in OLD are summarized in Fig. In a recent study involving asthmatic patients during methacholine challenge, FEV 1-Sp overestimated bronchoconstrictor response in those with larger lung volume [ 73 ]. FEV 1-Sp also overestimated bronchodilator response following administration of salbutamol to the same patients.
In another study, FEV 1-Sp and FEV 1-Pl were simultaneously measured in 47 and 51 subjects with dominant emphysema and dominant chronic bronchitis, respectively [ 74 ]. The results confirmed larger lung volumes and lower FEV 1-Sp in emphysematous patients compared with those with dominant chronic bronchitis.
When FEV 1-Pl was used instead of FEV 1-Sp , the disease severity was less in classes with dominant emphysema than those with dominant chronic bronchitis.
Decreased TLC in patients with spirometric evidence of airways obstruction e. This fact explains the findings of Balfe et al. According to Balfe et al. However, NSP was also demonstrated in patients with restrictive ventilatory defects [ 80 ].
Possible explanation for NSP in patients with restrictive ventilatory defects remains for further investigations and researches. Simultaneous increase in RV with VC reduction is indicative of obstructive lung disease.
Therefore, decreased VC readings are better interpreted in conjunction with other clinical and spirometric indicators of OLD. In RLD like central obesity, decreased chest wall compliance reduces FRC and ERV, which may induce premature formation of flow limiting segments during quiet breathing. NSP was also demonstrated in patients with restrictive ventilatory defects, which needs further investigations and researches.
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Energy Flow 3. Carbon Cycling 4. Climate Change 5: Evolution 1. Evolution Evidence 2. Natural Selection 3. Classification 4. Cladistics 6: Human Physiology 1. Digestion 2. The Blood System 3. Disease Defences 4. Gas Exchange 5. Homeostasis Higher Level 7: Nucleic Acids 1.
DNA Structure 2. Transcription 3. Translation 8: Metabolism 1. Metabolism 2. The objective of this study was to evaluate the changes in vital capacity in with height and gender. The volunteers' height was measured in cm. Vital capacity of the subjects was measured using standard protocol.
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