WEEK 2: Physiological consequences of lung disease Flashcards
What are obstructive lung diseases?
Give examples.
Obstructive lung diseases are a group of respiratory conditions characterized by a persistent airflow limitation, making it difficult for individuals to exhale air from their lungs.
COPD, Asthma, Bronchiectasis
Define restrictive lung diseases.
Give examples.
Restrictive lung diseases are a group of respiratory conditions characterized by a reduced expansion of the lung tissue, leading to decreased lung volume and impaired ability to inhale air.
EXAMPLES
1. Interstitial Lung Disease (ILD):
*ILD refers to a group of disorders that cause inflammation and scarring of the interstitium, which is the tissue that supports the air sacs in the lungs.
- Pneumoconiosis:
*This term refers to lung diseases caused by the inhalation of various types of dust, such as coal dust (coal worker’s pneumoconiosis), silica dust (silicosis), and asbestos fibers (asbestosis). These particles can lead to inflammation and fibrosis of the lung tissue over time. - Neuromuscular Disorders:
*Conditions that affect the nerves and muscles involved in breathing can lead to restrictive lung disease. Examples include muscular dystrophy, amyotrophic lateral sclerosis (ALS), and myasthenia gravis. - Thoracic Cage Abnormalities:
*Structural abnormalities of the chest wall, spine, or respiratory muscles can restrict lung expansion. Conditions like kyphosis, scoliosis, and ankylosing spondylitis can contribute to restrictive lung disease. - Obesity-Related Lung Disease:
*Severe obesity can lead to reduced lung expansion due to the increased pressure on the diaphragm and chest wall.
Outline Structural difference between obstructive and restrictive lung disease.
In obstructive lung disease
*Airways are affected
*Premature closure of the airways
*Air Trapping: Incomplete exhalation of air during breathing due to narrowed airways and loss of elastic recoil.
*Residual volume increased
*Lung parenchyma may/may not be affected
In restrictive lung disease
*Airways are not affected
*Lung parenchyma affected
*Reduced Lung Compliance:
*Decreased Total Lung Capacity:
*Reduced lung tissues (fibrosis)
General Differences:
1. Airflow vs. Lung Expansion:
Obstructive diseases primarily affect airflow and the ability to exhale.
Restrictive diseases primarily affect lung expansion and the ability to inhale.
- Location of Pathology:
Obstructive diseases often involve the large airways (bronchi).
Restrictive diseases affect the lung parenchyma, interstitium, or chest wall. - Reversibility:
Obstructive diseases may show partial reversibility with bronchodilators.
Restrictive diseases are generally not reversible, as the primary issue lies in the lung tissue itself.
Outline Features of obstructive lung disorder.
OBSTRUCTIVE
*FEV1 is less than normal predicted values
*FVC may be normal or slightly reduced.
*FEV1%FVC is less than 75
*Static lung volumes are elevated
*Increased work of breathing during expiration
Outline the complications/ consequences of obstructive lung diseases.
Consequences:
1. DECREASED Air flow (DECREASED FEV1, PEF).
INCREASED work of breathing»_space;»resp muscle fatigue»_space;» respiratory failure.
- DECREASED PaO2, INCREASED PaCO2»_space;» PHT»_space;» cor pulmonale (Right heart failure).
Outline Features of Restrictive lung disorder.
RESTRICTIVE
Small lung due to:
*Fibrotic lung parenchyma, stiff lung
*Pleural diseases, effusion, tumors, emphysema
*Restricted chest movements
*Cosmetics
Lung volumes:
Static lung volumes reduced.
Dynamic lung volumes [FEV1) and FVC proportionately reduced.
FEV1%FVC =>75
Describe Lung volumes in obstructive lung diseases.
- Tidal Volume (TV):
Normal or slightly increased. - Inspiratory Reserve Volume (IRV):
Decreased due to difficulty inhaling deeply. - Expiratory Reserve Volume (ERV):
Significantly reduced due to air trapping during expiration. - Residual Volume (RV):
Increased because of difficulty expelling air completely. - Vital Capacity (VC):
Reduced, primarily due to decreased expiratory reserve volume. - Total Lung Capacity (TLC):
Increased due to elevated residual volume. - Functional Residual Capacity (FRC):
Increased due to air trapping. - Forced Expiratory Volume in 1 second (FEV1):
Decreased, indicating reduced expiratory flow rates. - Forced Vital Capacity (FVC):
Decreased, contributing to a decreased vital capacity. - FEV1/FVC Ratio:
Decreased, reflecting airflow limitation.
10.Air Trapping:
Hyperinflated state due to increased TLC and RV.
Describe Lung volumes in restrictive lung diseases.
Everything is reduced, the curve is smaller.
Define hypoxemia.
Reduction PaO2 below 60 mm Hg.
Outline causes of hypoxemia.
Causes:
*Hypoventilation
*Diffusion impairment
*Shunts
*Ventilation/perfusion imbalance
Define hypercapnia.
Elevated PaCO2 above 49 mm Hg.
Outline causes of hypercapnia.
Causes
Hypoventilation
Ventilation perfusion imbalance
Outline causes of hypoventilation.
Related to respiratory centre
Related to spinal cord injuries
Related to cranial nerves damage
Related to muscles of respiration (diaphragm)
Related to damaged lung tissues
Describe features of hypoventilation
-Reduced PaO2
-Raised PaCO2 (respiratory acidosis)
-Hypoventilation
-Elevated plasma bicarbonate
-Hypoxemia that can be corrected by administration of enriched oxygen
*Beware of chronic hypoventilation as PaCO2 may be elevated more!
Outline membrane factors that result in Diffusion impairment.
Membrane factors
- Thickness
Asbestosis, oedema - Solubility coefficient
CO2 is readily soluble in the matrix than O2. - Partial pressure gradient
Higher gradient enhances gas exchange. - Molecular weight
Inverse relation to the square root of the molecular weight.
**Significance: Oxygen (O2) has a lower molecular weight than carbon dioxide (CO2), contributing to its faster diffusion across the alveolar-capillary membrane.
