Lung Volumes

1. Inspiratory Reserve Volume: • Volume that can be inspired beyond a • restful inspiration • Tidal Volume: • Volume of a single breath, usually at • rest • Expiratory Reserve Volume: • Volume which can be expired beyond a • restful expiration • Residual Volume: • Volume remaining in the lungs after • maximum expiration. This volume keeps • the alveoli inflated. Lung Volumes • Vital Capacity: the maximum volume which can be ventilated in a single breath • VC = IRV + TV + ERV • VC varies with gender, age, and body build • Measuring VC gives a device for diagnosis of respiratory disorder, and a benchmark for judging effectiveness of treatment. • VC is reduced in restrictive disorders but not in disorders that are purely obstructive. • FEV1 :the % of vital capacity (forced expiratory volume) expelled in the first second. Should be at least 75%. Reduced in obstructive disorders.

2. Influences on Volumes • At sea level, a person develops a slightly smaller lung capacity than a person who spends their life at a high altitude because the partial pressure of oxygen is lower at higher altitude. Therefore, oxygen less readily diffuses into the bloodstream and the body's diffusing capacity increases in order to process more air. • Altitude sickness can occur because the lungs remove adequate amounts of carbon dioxide but they do not take in enough oxygen.

4. Obstructive Respiratory Disorders • People with obstructive lung disease have difficulty exhaling all the air from the lungs. Because of damage to the lungs or narrowing of the airways inside the lungs, exhaled air comes out more slowly than normal. At the end of a full exhalation, an abnormally high amount of air may still linger in the lungs. • Affects FEV1 :the % of vital capacity (forced expiratory volume) expelled in the first second. Should be at least 75%. This percentage is reduced in obstructive disorders. • Examples/causes of obstructive respiratory disorders: • Chronic obstructive pulmonary disease (COPD): includes emphysema and chronic bronchitis • Asthma • Cystic fibrosis

5. Restrictive Respiratory Disorders • People with restrictive lung disease cannot fully fill their lungs with air. Their lungs are restricted from fully expanding. Restrictive lung disease most often results from a condition causing stiffness in the lungs themselves. In other cases, stiffness of the chest wall, weak muscles, or damaged nerves may cause the restriction in lung expansion. • Vital Capacity(IRV + TV + ERV) is reduced in people with restrictive disorders • Examples/causes of restrictive respiratory disorders: • Interstitial lung disease such as idiopathic pulmonary fibrosis • Sarcoidosis • Obsesity • Scoliosis • Neuromuscular disease, such as muscular dystrophy or amyotrophic lateral sclerosis (ALS)