Chapter 21_1 flashcards
(30 cards)
Classification of Lung Disease based on PFTs
Pulmonary Function Tests (PFTs / spirometry) are used to classify lung diseases into: 1. Obstructive Disease: Characterized by an increase in resistance to airflow. 2. Restrictive Disease: Characterized by reduced expansion of lung tissue and decreased total lung capacity (TLC).
Risk Factors for Lung Disease (General)
Smoking (primary cause of some, e.g., COPD), secondhand smoke, occupational and environmental exposures to harmful substances (e.g., coal, silica, asbestos, radon, indoor chemical agents).
Bronchodilation vs. Bronchoconstriction: Control
Smooth muscle in bronchi and bronchioles controls airway diameter. Sympathetic nervous system (via beta-2 adrenergic receptors) causes bronchiole dilation. Parasympathetic nervous system causes bronchiole constriction.
Chemical Mediators of Bronchoconstriction
Leukotrienes (secreted by WBCs) and Histamine (released by mast cells) stimulate bronchoconstriction.
Lung Compliance: Definition & Factors Affecting It
The flexibility of the lungs to expand and contract. Reduced by illness (pneumonia, bronchitis), inflammation (pulmonary fibrosis, sarcoidosis), making lungs stiffer and increasing work of breathing.
Pleural Membrane & Pleural Space: Function
Pleural membrane lines the chest cavity (parietal pleura) and envelops the lungs (visceral pleura). Pleural space is the area between these linings, normally a vacuum with a thin film of lubricating fluid (surfactant). Negative intrathoracic pressure in this space enables lungs to inflate easily.
Consequences of Air/Fluid in Pleural Space
If air (pneumothorax) or fluid (pleural effusion) enters the pleural space, the positive pressure pushes against lung tissue, preventing full expansion.
Hypoxia vs. Hypoxemia vs. Hypercapnia: Definitions
Hypoxia: Lack of oxygen available to body tissues. Hypoxemia: Lack of sufficient oxygen in the bloodstream. Hypercapnia: Elevated carbon dioxide (CO2) levels in the body or bloodstream (PCO2 > 45 mm Hg).
Chronic Hypercapnia: Effect on Breathing Stimulus
With prolonged hypercapnia, central chemoreceptors (medulla) become insensitive to high CO2. The primary stimulus for ventilation shifts to peripheral chemoreceptors, which are triggered by low oxygen levels (hypoxic drive).
Chronic Hypoxia: Body’s Compensatory Responses
- Increased ventilation. 2. Increased erythropoietin (EPO) secretion by kidneys, stimulating RBC production by bone marrow. 3. Pulmonary arterial vasoconstriction (can lead to pulmonary hypertension and cor pulmonale if chronic).
Pulmonary Assessment: Smoking History (Pack-Years)
Calculated as: (Number of years smoked) x (Number of packs smoked per day). Example: 2 packs/day for 60 years = 120 pack-year history.
Pulmonary Assessment: Key History Components
Smoking habits, occupational/environmental exposures, drug use, nonrespiratory disorders (cardiac, HIV, autoimmune), genetics (AAT deficiency), symptoms (dyspnea, cough, hemoptysis, orthopnea).
Pulmonary Physical Exam: Inspection - Key Findings
Breathing rate/rhythm/depth, use of accessory muscles (retractions), cyanosis (bluish discoloration from hypoxia), thoracic cage shape (normal width:depth is 2:1; “barrel-chest” 1:1 in COPD), clubbing of fingers (chronic hypoxia).
Pulmonary Physical Exam: Palpation - Tactile Fremitus
Palpable vibration on chest wall when patient speaks (“ninety-nine”). Increased fremitus suggests consolidation (pneumonia); decreased suggests pleural effusion or pneumothorax.
Pulmonary Physical Exam: Percussion - Tones & Significance
Resonant: Normal air-filled lung. Dull: Solid mass or fluid consolidation (e.g., pneumonia, pleural effusion). Hyperresonance: Overinflated lungs (e.g., emphysema, pneumothorax).
Normal Breath Sounds & Locations
Bronchial: Over trachea (loud, high-pitched, expiratory > inspiratory). Bronchovesicular: Over main bronchi (intermediate pitch, inspiratory = expiratory). Vesicular: Peripheral lung fields (low pitched, inspiratory > expiratory).
Adventitious Breath Sounds: Crackles (Rales)
Noncontinuous sounds, like deflated alveoli opening/closing against fluid. Heard in heart failure, pneumonia.
Adventitious Breath Sounds: Wheezes
High-pitched, whistling sounds due to constricted airway diameter. Inspiratory or expiratory. Common in asthma, COPD.
Adventitious Breath Sounds: Rhonchi
Low-pitched, snore-like sounds due to secretions or inflammation in larger bronchi.
Adventitious Breath Sounds: Pleural Friction Rub
Grating, scratchy sound heard during inspiration and expiration; due to inflammation of pleural surfaces rubbing together.
Vocal Resonance Abnormalities Indicating Pneumonia
Bronchophony: Spoken words sound clearer and louder. Egophony: Patient says “e,” sounds like “a”. Whispered Pectoriloquy: Whispered sounds become clear and distinctive.
Pulmonary Diagnostic Tests: General List
Chest x-ray, CT scan, MRI, V-Q scan, Arterial Blood Gases (ABGs), Pulse Oximetry, Bronchoscopy, Thoracocentesis, Pulmonary Function Tests (PFTs).
Pulmonary Function Tests (PFTs) / Spirometry: General Purpose
Measure different lung volumes and airflow rates as patient exhales into a device. Used to categorize pulmonary disorders as obstructive or restrictive.
PFTs: Key Lung Volumes & Capacities (Box 21-1)
Total Lung Capacity (TLC): Air in lungs after maximal inhalation. Functional Residual Capacity (FRC): Air remaining after normal exhalation. Residual Volume (RV): Air remaining after complete exhalation. Tidal Volume (TV): Normal breathing volumes.
