• Inspiratory Reserve Volume:
Lung Volumes
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.
• 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.
Influences on Volumes
Larger Volumes
Smaller Volumes
taller people
shorter people
non-smokers
smokers
people who live at higher altitudes
people who live at lower altitudes
• 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.
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
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)