Resp Physiology 1 Flashcards
What are the two main functions of the lungs?
Gas exchange
Acid-base balance
Which lung is larger?
Right lung
How many lobes does each lung have?
Right: 3 (upper, middle, lower)
Left: 2 (upper, lower)
What is the lingula?
Left lung equivalent of the right middle lobe
What supplies blood to the lungs for gas exchange?
Pulmonary artery
What supplies blood to the lung stroma (supporting tissue)?
Bronchial arteries
How many bronchial arteries are there?
Right: 1
Left: 2
Where do bronchial arteries originate from?
Left: Descending aorta
Right: Intercostal artery
What is the function of the trachea?
Conducts air to bronchi
What is the carina?
Bifurcation of the trachea into bronchi
What are the two groups of extrinsic muscles of the larynx?
Suprahyoid
Infrahyoid
What is the main nerve supply of the pharynx?
Pharyngeal plexus (CN IX, X, XI)
Which nerve is affected in Cricothyroid paralysis?
Superior laryngeal nerve (SLN)
Which nerve is affected in vocal cord paralysis?
Recurrent laryngeal nerve (RLN)
What happens in bilateral RLN (Recurrent laryngeal nerve) injury?
Stridor
What happens in unilateral RLN (Recurrent laryngeal nerve) injury?
Hoarseness
What are the two phases of breathing?
Inspiration (active)
Expiration (passive)
What law governs airflow resistance?
Hagen-Poiseuille law
F= ΔP⋅r4 / 8ηl
Where:
F = Flow
ΔP = Pressure difference
r = Radius of the tube
η = Viscosity of the gas
l = Length of the tube
This shows flow is most dependent on radius – small changes in airway diameter make a huge difference!
What law describes flow in the airways?
Darcy’s law: Flow = (P1 - P2) / R
F= P1-P2 / R
Where:
P 1 = Proximal (airway opening) pressure
P 2 = Distal (alveolar) pressure
R = Resistance
What happens in forced expiration?
Increased intra-thoracic pressure → airway compression
What muscles are used in quiet breathing?
Diaphragm
External intercostals
What muscles are used in forced inspiration?
Sternocleidomastoid
Scalene
What muscles are used in forced expiration?
Abdominals
Internal intercostals
What is tidal volume (VT)?
Normal breath (~500ml)
What is inspiratory reserve volume (IRV)?
Extra air inhaled after tidal volume
What is expiratory reserve volume (ERV)?
Extra air exhaled after tidal volume
What is residual volume (RV)?
Air remaining in lungs after maximal expiration
What is vital capacity (VC)?
VT + IRV + ERV
What is total lung capacity (TLC)?
VC + RV
What is anatomical dead space?
Conducting airways (~150ml)
What is alveolar dead space?
Alveoli not participating in gas exchange
What is physiological dead space?
Anatomical + alveolar dead space
How is compliance calculated?
C = ΔV / ΔP
Where:
C = Compliance
ΔV = Tidal volume (VT)
ΔP = Pressure difference
🔹 Static Compliance:
𝐶 =𝑉𝑇/𝑃Plat−PEEP
𝑃Plat = Plateau pressure
PEEP = Positive end-expiratory pressure
🔹 Dynamic Compliance:
𝐶=𝑉𝑇/𝑃Peak−PEEP
P Peak = Peak inspiratory pressure
Key Difference? Dynamic compliance includes airway resistance, static compliance does not.
What is static compliance?
Compliance measured without airflow
What is dynamic compliance?
Compliance measured with airflow
What are the two main types of lung disease?
Obstructive
Restrictive
What happens to FEV1/FVC in obstructive disease?
Decreased
What happens to FEV1/FVC in restrictive disease?
Normal or increased
What is an example of an obstructive lung disease?
COPD (Chronic Obstructive Pulmonary Disease)
Asthma
What is an example of a restrictive lung disease?
Pulmonary fibrosis
What happens to lung compliance in restrictive disease?
Decreased
What happens to lung compliance in obstructive disease?
Increased
What are causes of pulmonary oedema?
Heart failure
ARDS (Acute Respiratory Distress Syndrome)
Fluid overload
What is ARDS?
Acute Respiratory Distress Syndrome
What are the criteria for ARDS?
Acute onset
Bilateral infiltrates
No heart failure
PaO2/FiO2 <300
**
FiO 2/PaO 2 <40kPa
Severity Breakdown (Berlin Criteria):
Mild: 26.7–40 kPa
Moderate: 13.3–26.6 kPa
Severe: <13.3 kPa
**
What are causes of atelectasis?
Mucus plugging
Compression
Loss of surfactant
What are signs of PE (pulmonary embolism)?
Sudden dyspnoea
Pleuritic chest pain
Tachycardia
What is the most common ECG finding in PE?
Sinus tachycardia (44%)
Complete or incomplete RBBB (18%)
Right ventricular strain pattern – T wave inversions in the right precordial leads (V1-4) ± the inferior leads (II, III, aVF). This pattern is associated with high pulmonary artery pressures (34%)
SI QIII TIII pattern – deep S wave in lead I, Q wave in III, inverted T wave in III (20%). This “classic” finding is neither sensitive nor specific for PE
Causes of Hypoxia: “H-H-V-D-D”
Hypoventilation
High altitude
V/Q mismatch
Diffusion defect
Dead space
ARDS Criteria: “ABCD”
Acute onset
Bilateral infiltrates
CXR (no heart failure)
Decreased PaO2/FiO2
