Lung volumes vital capacity

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

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 is the measurement of the ventilatory capacity of the lungs. Forced vital capacity (FVC) is the maximum volume of air that can be exhaled forcefully after a maximum inspiration. 

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. 

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. 

Forced vital capacity (FVC) measures the maximum volume of air expelled from the lung in a single forced expiration there is no time limit. Forced expiratory volume in one second (FEVi) measures the volume of air which can be expelled from the lung in one second. In a normal individual 80% of the vital capacity can be expired in one second, but patients with obstructive disease have difficulty in emptying the lung and this value is significantly reduced. 

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. ... 

---