<P> Spirometry is used to measure lung function . The total lung capacity (TLC), functional residual capacity (FRC), residual volume (RV), and vital capacity (VC) are all values that can be tested using this method . Spirometry is used to help detect, but not diagnose, respiratory issues like COPD, and asthma . It is a simple and cost effective screening method . Further evaluation of a person's respiratory function can be done by assessing the minute ventilation, forced vital capacity (FVC), and forced expiratory volume (FEV). These values differ in men and women because men tend to be larger than women . </P> <P> TLC is the maximum amount of air in the lungs after maximum inhalation . In men the average TLC is 6000 ml, and in women it is 4200 ml . FRC is the amount of air left in the lungs after normal exhalation . Men leave about 2400 ml on average while women retain around 1800 ml . RV is amount of air left in the lungs after a forced exhalation . The average RV in men is 1200 ml and women 1100 ml . VC is the maximum amount of air that can be exhaled after a maximum inhalation . Men tend to average 4800 ml and women 3100 ml . </P> <P> Asthma, COPD, and smokers have reduced airflow ability . People who suffer from asthma and COPD show decreases in exhaled air due to inflammation of the airways . This inflammation causes narrowing of the airways which allows less air to be exhaled . Numerous things cause inflammation some examples are cigarette smoke and environmental interactions such as allergies, weather, and exercise . In smokers the inability to exhale fully is due to the loss of elasticity in the lungs . Smoke in the lungs causes them to harden and become less elastic, which prevents the lungs from expanding or shrinking as they normally would . </P> <P> Dead space can be determined by two types of factors which are anatomical and physiological . Some physiological factors are having non-perfuse but ventilated alveoli, such as a pulmonary embolism or smoking, excessive ventilation of the alveoli, brought on in relation to perfusion, in people with chronic obstructive lung disease, and "shunt dead space," which is a mistake between the left to right lung that moves the higher CO2 concentrations in the venous blood into the arterial side . The anatomical factors are the size of the airway, the valves, and tubing of the respiratory system . Physiological dead space of the lungs can affect the amount of dead space as well with factors including smoking, and diseases . Dead space is a key factor for the lungs to work because of the differences in pressures, but it can also hinder the person . </P>

What is the pressure in the lungs after expiration