Week 5 Lung Volumes And Capaitys Lecture Bites Flashcards
Breathing
varying amounts of air move in and out of the lungs
Lung Volumes
Measured directly by spirometry
Lung Capacity
Combinations of different lung volumes
Air movement will depend upon:
Age
• Sex
• Height/weight • Ethnicity
• Physical fitness • Altitude
• Disease status
Tidal volume
Volume of one breath at rest = VT
~500 mL in and out of the lungs
~70% reaches the respiratory zone ~30% remains in the conducting airways
Inspiratory reserve volume
Additional inhaled air from a very deep breath
• ~3100 mL (male)
• ~1900 mL (female)
Expiratory reserve volume
Additional exhaled air
• Exhale as forcefully as possible
• ~1200 mL (male)
• ~700 mL (female)
Residual volume
Air remaining in the lungs
• Cannot be measured by
spirometry
• Keeps alveoli inflated
Lung capacities
Inspiratory Capacity
(IC = VT + IRV)
• The maximal volume of air that can be inspired following a normal, quiet expiration
Functional Residual Capacity (FRC = ERV + RV)
• The volume remaining in the lungs after a normal, passive exhalation
Capacities
Vital Capacity
(VC = IRV + VT + ERV)
• The maximal amount of air that can be inhaled after a maximum exhalation
Total Lung Capacity
(TLC = IRV + VT + ERV + RV)
• The maximum volume of air the lungs can accommodate
Forced Expiratory Volume (FEVt)
The volume of air maximally forced from the lungs at a given time in seconds
• FEV1 = at the end of the 1st second
• FEV2 = at the end of the 2nd second
• FEV3 = at the end of the 3rd second
FEV is the most important measurement of lung function
Forced Vital Capacity (FVC)
The total amount of air exhaled during the FEV test
FEV1/FVC
• The proportion of vital capacity exhaled in the first second of forced expiration to the full, forced vital capacity
• Expressed as FEV1%
• Normal values are ≥70% (but varies with age)
• Obstructive disease <70% or below normal
range
Aging and the respiratory system
• Airways and tissues become less elastic and more rigid
• Chest wall becomes more rigid
• Decrease in lung capacity
• Reduction: blood O2, macrophage activity, ciliary action
• Increased susceptibility to pneumonia, bronchitis, emphysema • Altered ability to perform exercise
Pathophysiology of lung diseases
Primarily Alveoli Affected
• COVID-19 (SARS-CoV-2) • Pneumonia
• Primarily Airways Affected
• Chronic Obstructive Pulmonary Disease (COPD) • Asthma
COVID-19
SARS-CoV-2
• Severe acute respiratory syndrome coronavirus 2
• Symptoms
• Mild to moderate upper respiratory illness
• Lower respiratory illness including pneumonia and bronchitis
• Vulnerable individuals are at higher risk
• Alveoli damage
• Hypoxia, Oedema, Hypoxaemia
Pneumonia
Before Covid-19, leading cause of infectious disease mortality
• Lower respiratory tract infection
• Acute infection or inflammation of pulmonary
alveoli
• Causative microorganisms
• Bacteria e.g., streptococcus pneumoniae, mycoplasma pneumoniae
• Respiratory viruses e.g., haemophilus influenzae
Release of damaging toxins and stimulate inflammation
• Toxins and immune response
• Damage pulmonary alveoli and bronchial mucous membranes • Inflammation and oedema lead to fluid on the lungs
• Interferes with gas exchange
• Often preceded by viral upper respiratory infection
• Susceptible individuals – elderly, infants, immunocompromised, smokers, obstructive lung disease
COPD
Chronic Obstructive Pulmonary Disease
• Chronic and recurrent obstruction of airflow - increases airway
resistance
• Principal types • Emphysema
• Chronic bronchitis
• Causes:
• Cigarette smoke
• Air pollution
• Exposure to dust/gases • Pulmonary infection
Emphysema
Destruction of the pulmonary alveoli walls
• Abnormally large air spaces that remain filled with air during exhalation • Reduced surface area for gas exchange
• Blood O2 is reduced
• Lung elasticity is decreased
• Treatment: bronchodilators & oxygen therapy
Chronic bronchitis
Excessive secretion of bronchial mucus
• Productive cough, shortness of breath, wheezing, pulmonary hypertension • Cigarette smoking is the leading cause
• Irritants
• Chronic inflammation
• Increase in size & number of mucous glands & goblet cells in airway epithelium
• Thickened and excessive mucus – narrows airway and impairs ciliary function • Inhaled pathogens become embedded
Asthma
Characterised by:
• Chronic airway inflammation
• Airway hypersensitivity • Airway obstruction
• Obstruction can be due to:
• Smooth muscle spasms in bronchia &
bronchiole walls
• Oedema of the airway mucosa
• Increased mucus secretion
• Airway epithelium damage
Triggered by:
• Allergens e.g., pollen, house dust mites
• Exercise
• Cold air
• Cigarette smoke
• Acute phase
• Smooth muscle spasm
• Excessive mucus secretion
Chronic phase • Inflammation
• Fibrosis
• Oedema
• Necrosis of bronchial epithelial cells
• Mediating chemicals – leukotrienes, prostaglandins, histamine, platelet activating factor
Symptoms
• Difficultybreathing • Coughing
• Wheezing
• Chest tightness
• Tachycardia
• Treatment
• Acute
• Beta2-adrenergic agonist – relax bronchiole smooth muscle & open airway • Sympathetic nervous system stimulation
• Chronic
• Suppress chronic inflammation - corticosteroids
