Total respiratory system notes physiology with all important points and topics in understanding way in exam point of view according to gk pal

Reading File

Finding Sources

Reading File

Finding Sources

Reading File

Finding Sources

Reading File

Finding Sources

Reading File

Searching Images

lung volumes and capacities spirometry diagram

A clinical photograph illustrating a patient performing a Pulmonary Function Test (PFT) via spirometry in a clinical or research setting. The image depicts an older adult male seated upright, wearing a nose clip to ensure mouth-only breathing. He is actively interacting with a handheld spirometer, holding the disposable mouthpiece with both hands to maintain a tight seal. The device is connected via a data cable to a computer system, which includes a monitor displaying an active interface, likely for real-time visualization of flow-volume loops and spirograms. On the desk, several replacement white cylindrical mouthpieces and the hardware interface are visible. This visual serves as an educational example of the standardized setup for measuring lung volumes and ventilation capacities, such as Forced Vital Capacity (FVC) and Forced Expiratory Volume in 1 second (FEV1), highlighting the necessary equipment and proper patient positioning during the procedure.

This composite of clinical photographs illustrates three standard methods for assessing physical performance and physiological capacity in a laboratory setting. Top Left: A participant undergoes maximal isometric strength measurement using an arm extension dynamometer. The subject is seated with the upper limb secured to a mechanical lever arm equipped with force transducers to quantify torque and muscular exertion. Top Right: A measurement of pulmonary function (spirometry) is shown. The participant uses a handheld spirometer with a nose clip to ensure isolated oral airflow, measuring lung volumes and capacities such as FVC and FEV1. Bottom: The participant is engaged in an anaerobic capacity assessment via a Wingate anaerobic test. This involves high-intensity cycling on a specialized ergometer to measure peak power, anaerobic fatigue, and total anaerobic work. These tests are essential in sports medicine and exercise physiology for evaluating cardiovascular fitness, neuromuscular strength, and metabolic efficiency.

Searching Images

oxygen hemoglobin dissociation curve

Summary : This figure illustrates the relationship between hemoglobin (Hb) level and oxygen delivery in individuals with sickle cell disease (SCD), highlighting the optimal Hb range for oxygen transport in SCD compared to normal individuals. line plot: # Title & Axes : • No explicit title on the plot, but the context is "Relationship between hemoglobin level and oxygen delivery in individuals with SCD." • X-axis: "Hemoglobin" (units not specified, but contextually g/dL). • Y-axis: "Oxygen delivery" (units not specified). • X-axis tick labels: 10, 15, 20. • Y-axis: No tick labels, only qualitative trend. # Data Points & Series : • Single red curve showing oxygen delivery as a function of hemoglobin level. • The curve rises from Hb = 10, peaks near Hb = 14–16, then declines toward Hb = 20. • Arrow and annotation for "Sickle Cell Anemia Hb_max ~10–11" indicating the optimal Hb range for SCD. • Dashed vertical line at "Normal Hb_max ~14–16" indicating the optimal Hb range for normal individuals. # Design Encodings : • Red solid line for the main curve. • Yellow arrow highlighting the SCD optimal Hb range. • Dashed vertical line for normal Hb_max. • Text annotations for "Sickle Cell Anemia Hb_max ~10–11" and "Normal Hb_max ~14–16". # Distribution & Trends : • The curve is unimodal, peaking at intermediate Hb levels. • Oxygen delivery increases with Hb up to a point, then decreases at higher Hb levels. • The optimal Hb for SCD is lower (~10–11 g/dL) than for normal individuals (~14–16 g/dL). # Analysis : • The figure visually demonstrates that the maximal oxygen delivery in SCD occurs at a lower hemoglobin level than in normal individuals, due to altered red cell viscosity and oxygen transport in SCD. • Increasing Hb above the SCD optimal range may decrease oxygen delivery, while lowering Hb to the optimal range can improve oxygen transport. • The curve supports clinical recommendations for transfusion targets in SCD patients to avoid excessive Hb levels that could impair oxygen delivery.

This diagnostic image set displays two functional MR images (A and B) showing maternal-fetal units in a mouse model at embryonic days 14.5 and 17.5. The images feature overlaid color-coded AP50 maps, which represent fetal and placental oxygen-hemoglobin dissociation parameters. In both panels, the placenta and fetal liver are isolated as regions of interest. A vertical color bar on the right side indicates AP50 values scaled from 0 to 1.0, with cool colors (dark blue) representing lower values and warm colors (red/orange) representing higher values. Panel A (day 14.5) demonstrates a heterogeneous distribution of oxygenation parameters within the tissues, showing a mix of green, yellow, and blue pixels. Panel B (day 17.5) illustrates the progression of these physiological markers over time, with the placental AP50 values showing a significant spatial shift toward warmer colors, reflecting changes in oxygen transfer efficiency. These maps provide a non-invasive visual method for studying fetal oxygenation and placental function during gestation.

Here are your complete, exam-oriented Respiratory System Physiology Notes based on GK Pal's approach (aligned with Costanzo, Ganong, and Guyton - all standard Indian physiology exam references):

🫁 RESPIRATORY SYSTEM PHYSIOLOGY - COMPLETE EXAM NOTES

Based on GK Pal Physiology | Exam-Oriented

TOPIC 1: STRUCTURE OF THE RESPIRATORY SYSTEM

Zones of the Respiratory System

Zone	Structures	Function
Conducting Zone	Nose, nasopharynx, larynx, trachea, bronchi, bronchioles, terminal bronchioles	Warm, humidify, filter air. NO gas exchange
Respiratory Zone	Respiratory bronchioles, alveolar ducts, alveolar sacs	Site of actual gas exchange

Key Points on Airways

Trachea = 0th generation; divides into 23 generations total
Conducting airways lined with mucus-secreting + ciliated cells (mucociliary escalator)
Airways contain smooth muscle with dual autonomic innervation:
- Sympathetic (β2 receptors) → Bronchodilation (epinephrine, albuterol)
- Parasympathetic (muscarinic M3 receptors) → Bronchoconstriction

Alveoli

~300 million alveoli; total surface area ~70 m² (like a tennis court)
Two cell types:
- Type I pneumocytes - flat, gas exchange
- Type II pneumocytes - cuboidal, secrete surfactant

TOPIC 2: LUNG VOLUMES AND CAPACITIES ⭐ (Most Important for Exams)

Four Basic Lung Volumes (Cannot be subdivided)

Volume	Abbreviation	Normal Value	Definition
Tidal Volume	TV (VT)	500 mL	Air breathed in/out per normal breath
Inspiratory Reserve Volume	IRV	3000 mL	Extra air inspired after normal inspiration
Expiratory Reserve Volume	ERV	1100 mL	Extra air expired after normal expiration
Residual Volume	RV	1200 mL	Air remaining after maximal expiration

Key Exam Fact: RV cannot be measured by spirometry. Measured by helium dilution or body plethysmography.

Four Lung Capacities (Combination of volumes)

Capacity	Formula	Normal Value	Significance
Total Lung Capacity (TLC)	TV + IRV + ERV + RV	6000 mL	Maximum air lungs can hold
Vital Capacity (VC)	TV + IRV + ERV	4800 mL	Maximum air exhaled after max inspiration
Inspiratory Capacity (IC)	TV + IRV	3500 mL	Max air inhaled from FRC
Functional Residual Capacity (FRC)	ERV + RV	2300 mL	Air remaining after normal expiration = equilibrium point

FRC is the resting lung volume - where lung elastic recoil inward = chest wall elastic recoil outward. These forces balance each other.

Changes in Restrictive vs Obstructive Disease

Parameter	Obstructive (Asthma/COPD)	Restrictive (Fibrosis/Sarcoid)
TLC	↑ or normal	↓
RV	↑ (air trapping)	↓
FRC	↑	↓
VC	↓	↓
FEV1/FVC	< 0.7 (hallmark)	Normal or ↑

TOPIC 3: VENTILATION ⭐

Key Equations

Minute Ventilation (VE):

VE = VT × Respiratory Rate = 500 mL × 12/min = 6000 mL/min

Alveolar Ventilation (VA) - The important one!

VA = (VT - Dead Space) × RR = (500 - 150) × 12 = 4200 mL/min

Dead Space = 150 mL (anatomical dead space = conducting zone volume)

Types of Dead Space

Type	Definition	Value
Anatomical dead space	Volume of conducting airways (no gas exchange occurs)	~150 mL
Physiological dead space	Anatomical + alveolar dead space (includes non-perfused alveoli)	= Anatomical in healthy person
Alveolar dead space	Ventilated but not perfused alveoli	~0 in health; ↑ in PE

In healthy people: Physiological dead space ≈ Anatomical dead space In disease (e.g., pulmonary embolism): Physiological > Anatomical

Bohr's Equation (to measure dead space):

VD/VT = (PaCO2 - PeCO2) / PaCO2

Alveolar Gas Equation ⭐ (Exams love this!)

PAO2 = PiO2 - (PACO2 / R)

Where:

PiO2 = (PB - 47) × 0.21 = (760 - 47) × 0.21 = 149 mm Hg at sea level
R = respiratory quotient = 0.8 (normal)
PACO2 ≈ PaCO2 = 40 mm Hg

So: PAO2 = 149 - (40/0.8) = 149 - 50 = ~100 mm Hg

Normal Partial Pressures

Gas	Inspired Air	Alveolar	Arterial blood	Venous blood	Tissue
PO2	159 mmHg	100 mmHg	95-100 mmHg	40 mmHg	20-40 mmHg
PCO2	0.3 mmHg	40 mmHg	40 mmHg	46 mmHg	46+ mmHg

TOPIC 4: MECHANICS OF BREATHING ⭐

Muscles of Breathing

Phase	Primary Muscles	Accessory
Quiet Inspiration	Diaphragm (main!), External intercostals	-
Forced Inspiration	+ Scalenes, SCM, pectoralis minor	-
Quiet Expiration	PASSIVE - elastic recoil of lungs	-
Forced Expiration	Internal intercostals, abdominal muscles (rectus, obliques)	-

Key fact: Normal quiet expiration is entirely passive (no muscle work needed).

Compliance

Definition: Change in volume per unit change in pressure

C = ΔV / ΔP (units: mL/cmH2O)

Normal lung compliance = 200 mL/cmH2O

Condition	Compliance	Example
↑ Compliance	Lungs are too "floppy"	Emphysema (destruction of elastic tissue)
↓ Compliance	Lungs are stiff	Pulmonary fibrosis, ARDS, pulmonary edema, neonatal RDS (no surfactant)

Surface Tension and Surfactant ⭐⭐

LaPlace's Law:

P = 2T / r (for alveolus) Where P = pressure inside, T = surface tension, r = radius

Without surfactant: Small alveoli would have higher pressure → air would flow to larger alveoli → atelectasis (alveolar collapse)
Surfactant (dipalmitoyl phosphatidylcholine / DPPC) reduces surface tension, especially in small alveoli

Properties of Surfactant:

Secreted by Type II pneumocytes
Main component: Dipalmitoylphosphatidylcholine (DPPC)
Also contains SP-A, SP-B, SP-C, SP-D (surfactant proteins)
Reduces surface tension → prevents alveolar collapse
More effective in small alveoli (more concentrated)
Appears at 24-28 weeks gestation → fully mature by 35 weeks
Deficiency = Neonatal Respiratory Distress Syndrome (NRDS/HMD)
Treatment: Antenatal glucocorticoids (betamethasone) to accelerate lung maturity

Airway Resistance

Formula: R = ΔP / Flow (Ohm's law analogy)

Main site of airway resistance = medium bronchi (NOT large airways or small airways)
Small airways contribute little to total resistance because they are numerous and in parallel

Factors affecting airway resistance:

Factor	Effect on Resistance
↑ Sympathetic (β2)	↓ Resistance (bronchodilation)
↑ Parasympathetic	↑ Resistance (bronchoconstriction)
Histamine, leukotrienes	↑ Resistance
↑ Lung volume	↓ Resistance (airways pulled open)
Mucus/obstruction	↑ Resistance

TOPIC 5: GAS EXCHANGE (DIFFUSION) ⭐

Fick's Law of Diffusion

Vx = D × A × ΔP / Δx

Where:

D = diffusion coefficient (proportional to solubility / √MW)
A = surface area
ΔP = partial pressure gradient
Δx = membrane thickness

Key comparisons:

CO2 diffuses 20x faster than O2 (because solubility of CO2 is 20x that of O2)
So CO2 problems are almost always ventilation problems, not diffusion problems

Lung Diffusing Capacity (DL)

Normal DLco (for CO) = 25 mL/min/mmHg
↓ DLco in: emphysema, pulmonary fibrosis, pulmonary embolism, anemia
↑ DLco in: polycythemia, supine position, exercise, left-to-right shunts

Diffusion-Limited vs Perfusion-Limited Exchange ⭐

Type	Mechanism	Examples
Perfusion-limited	Gas equilibrates quickly; exchange limited by blood flow	O2 (normal), CO2, N2O
Diffusion-limited	Gas never equilibrates; limited by membrane diffusion	CO, O2 (exercise, fibrosis, altitude)

O2 is normally perfusion-limited but becomes diffusion-limited in disease or exercise.

TOPIC 6: OXYGEN TRANSPORT ⭐⭐

Two Forms of O2 in Blood

Form	% of Total	Comments
Dissolved O2	2%	Follows Henry's law; only form that creates PO2; ~0.3 mL/100mL at PaO2 100 mmHg
O2 bound to Hb	98%	~20 mL/100mL; essential for adequate delivery

O2 Content Formula:

CaO2 = (1.34 × Hb × SaO2) + (0.003 × PaO2)

Normal: (1.34 × 15 × 1.0) + (0.003 × 100) = 20.1 + 0.3 = ~20 mL O2/100 mL blood

O2 Delivery (DO2):

DO2 = Cardiac Output × CaO2 = 5000 × 20 mL/L = 1000 mL/min

Normal O2 consumption (VO2) at rest = 250 mL/min

Hemoglobin Structure

4 subunits: each with a heme (iron-porphyrin) + globin chain
Adult Hb (HbA): α2β2
HbF: α2γ2 - higher O2 affinity (left shift) → takes O2 from mother's blood
1 Hb can carry 4 O2 molecules
O2-binding capacity = 1.34 mL O2/g Hb (Hüfner's constant)

Hemoglobin Variants

Variant	Iron State	O2 Binding	Cause
Oxyhemoglobin	Fe²⁺	YES	Normal
Deoxyhemoglobin	Fe²⁺	NO (ready to bind)	Normal
Methemoglobin	Fe³⁺	NO	Nitrites, sulfonamides, congenital (↓ methemoglobin reductase)
Carboxyhemoglobin	Fe²⁺ + CO	NO (CO binds 240x stronger than O2)	CO poisoning

Oxygen-Hemoglobin Dissociation Curve ⭐⭐⭐

Sigmoidal (S-shaped) due to cooperative binding
P50 = PO2 at which Hb is 50% saturated = 26-27 mmHg (normal)

Right Shift (↓ affinity, ↑ P50) = O2 unloading to tissues:

↑ Temperature, ↑ PCO2, ↑ H⁺ (↓ pH), ↑ 2,3-DPG, ↑ altitude (chronic)

Mnemonic: CADET, face RIGHT (CO2, Acid/H⁺, DPG, Exercise, Temperature)

Left Shift (↑ affinity, ↓ P50) = O2 loading in lungs:

↓ Temperature, ↓ PCO2, ↓ H⁺ (↑ pH), ↓ 2,3-DPG, HbF, CO, Methemoglobin

Bohr Effect: ↑ CO2 and ↑ H⁺ causes right shift (tissues produce CO2/H⁺ → favors O2 unloading)

2,3-DPG:

Produced in RBCs (glycolysis byproduct)
Binds to β chains of deoxy-Hb → stabilizes deoxy form → right shift
↑ in: anemia, high altitude, chronic hypoxia
↓ in: stored blood (banked blood) - important in massive transfusion!

Cyanosis

Appears when deoxy-Hb > 5 g/dL in capillary blood
Central cyanosis = arterial desaturation
Peripheral cyanosis = ↑ O2 extraction at periphery (vasoconstriction, heart failure)

TOPIC 7: CARBON DIOXIDE TRANSPORT ⭐

Three Forms of CO2 in Blood

Form	% of Total	Location
Dissolved CO2	5%	Plasma; solubility = 0.07 mL/100mL/mmHg
Carbaminohemoglobin	5%	CO2 + amino groups on Hb/proteins
Bicarbonate (HCO3-)	90%	Inside RBCs → plasma (most important!)

HCO3- Formation (Chloride Shift) ⭐⭐

In tissues:

CO2 + H2O → H2CO3 → H⁺ + HCO3⁻

Catalyzed by carbonic anhydrase (CA) inside RBCs
HCO3⁻ exits RBC in exchange for Cl⁻ entering → Hamburger shift / Chloride shift
H⁺ is buffered by Hb

In lungs: The process reverses - HCO3⁻ + H⁺ → CO2 → exhaled

Haldane Effect: Deoxygenation of Hb increases CO2 carrying capacity

At tissues: Hb gives up O2 → deoxy-Hb → better CO2 carrier → ↑ CO2 pickup
At lungs: Hb binds O2 → oxy-Hb → ↓ CO2 carrying → CO2 released

TOPIC 8: VENTILATION/PERFUSION (V/Q) RATIO ⭐⭐

Normal V/Q Ratio = 0.8 (VA = 4.2 L/min; Q = 5 L/min)

Regional V/Q Differences in Upright Lung

Region	V/Q	PO2	PCO2	Explanation
Apex	>0.8 (↑, ~3.3)	High (~130 mmHg)	Low (~28 mmHg)	Gravity: less blood flow to apex
Base	<0.8 (↓, ~0.6)	Low (~89 mmHg)	High (~42 mmHg)	More blood flow; relatively less ventilation

Both ventilation AND perfusion increase from apex to base, but perfusion increases MORE steeply.

V/Q Extremes

Condition	V/Q	Equivalent	Example
Dead space	∞ (V/Q = ∞)	Ventilated, not perfused	Pulmonary embolism
Shunt	0 (V/Q = 0)	Perfused, not ventilated	Pneumonia, atelectasis

Hypoxic Pulmonary Vasoconstriction (HPV) ⭐

Low alveolar PO2 → constricts pulmonary arterioles (opposite to systemic!)
Redirects blood away from poorly ventilated alveoli → improves V/Q matching
Occurs in chronic hypoxia (altitude, COPD) → chronic pulmonary hypertension

TOPIC 9: PULMONARY CIRCULATION ⭐

Feature	Pulmonary	Systemic
Pressure	25/8 mmHg (mean ~15)	120/80 mmHg
Resistance	Low	High
Response to hypoxia	Vasoconstriction (HPV)	Vasodilation
Wall thickness	Thin	Thick
O2 effect	Low O2 → constrict	Low O2 → dilate

West's Zones of the Lung ⭐⭐

Zone	Location	Condition	Blood Flow
Zone 1	Apex	PA > Pa > Pv	No flow (only in pathology/PPV)
Zone 2	Mid	Pa > PA > Pv	Intermittent (flow ∝ Pa - PA)
Zone 3	Base	Pa > Pv > PA	Continuous (flow ∝ Pa - Pv)

(PA = alveolar pressure, Pa = arterial pressure, Pv = venous pressure)

TOPIC 10: CONTROL OF BREATHING ⭐⭐

Respiratory Centers in the Brainstem

Center	Location	Function
Dorsal respiratory group (DRG)	Medulla	Inspiration neurons (basic rhythm)
Ventral respiratory group (VRG)	Medulla	Expiration + forced breathing
Pneumotaxic center	Upper pons	Limits inspiration; switches off inspiration
Apneustic center	Lower pons	Prolongs inspiration (held in check by pneumotaxic)

Cutting between pons and medulla → apneusis (prolonged inspiratory gasps) Cutting above pons (at pons-midbrain junction) → normal rhythm maintained

Central Chemoreceptors ⭐⭐

Location: Ventral surface of medulla (not in the NTS)
Stimulus: ↑ PCO2 → ↑ H⁺ in CSF (CO2 crosses blood-brain barrier freely; H⁺ does not)
Most important regulator of breathing under normal conditions
Insensitive to hypoxia directly
In chronic hypercapnia (COPD) → central receptors adapt → these patients rely on hypoxic drive (peripheral)

Peripheral Chemoreceptors ⭐⭐

Location: Carotid bodies (IX nerve, main) + Aortic bodies (X nerve)
Stimuli (in order of importance):
1. ↓ PaO2 (< 60 mmHg - significant threshold!)
2. ↑ PaCO2
3. ↓ pH
4. ↓ arterial pressure
Only receptors that respond to hypoxia (↓ PO2)
Carotid bodies are the most important peripheral chemoreceptors

Key exam point: PaO2 must fall below 60 mmHg before peripheral chemoreceptors significantly stimulate ventilation

Other Receptors

Receptor	Location	Stimulus	Response
Pulmonary stretch receptors	Airway smooth muscle	Lung inflation	Terminate inspiration (Hering-Breuer reflex)
Irritant receptors (Rapidly adapting)	Bronchial epithelium	Dust, smoke, chemicals	Bronchospasm, cough, hyperpnea
J receptors (juxtacapillary)	Alveolar walls near capillaries	Pulmonary edema, embolism	Rapid shallow breathing, dyspnea
Proprioceptors	Joints, muscles	Movement/exercise	Early ↑ in ventilation at start of exercise

Hering-Breuer Reflex

Lung inflation → activates pulmonary stretch receptors → inhibits inspiration (via vagus)
Prevents over-inflation
More important in newborns and during anesthesia; minimal role in awake adults

TOPIC 11: PULMONARY FUNCTION TESTS (PFTs) ⭐

Spirometry - Key Measurements

Parameter	Normal	Significance
FVC (Forced Vital Capacity)	~4.8 L	Total air exhaled forcefully
FEV1	~3.4 L	Air exhaled in 1st second
FEV1/FVC	>0.75	Key ratio for obstruction
PEFR	400-600 L/min	Peak Expiratory Flow Rate

Obstructive vs Restrictive Pattern

Test	Obstructive	Restrictive
FVC	Normal or ↓	↓
FEV1	↓↓	↓
FEV1/FVC	< 0.7	Normal or ↑
TLC	↑	↓
RV	↑	↓
DLCO	↓ (emphysema)	↓ (fibrosis)

TOPIC 12: SPECIAL TOPICS ⭐

Neonatal Respiratory Distress Syndrome (HMD)

Cause: Immature lungs → ↓ surfactant → ↑ surface tension → alveolar collapse
Seen in premature infants < 35 weeks
Risk factors: prematurity, maternal diabetes, C-section without labor
Treatment: Exogenous surfactant (beractant, poractant), antenatal betamethasone

CO Poisoning ⭐

CO has 240x greater affinity for Hb than O2
Produces carboxyhemoglobin → cannot carry O2
Left-shifts O2-Hb dissociation curve → impairs O2 unloading at tissues
PaO2 is NORMAL (dissolved O2 still normal) but O2 content and saturation are severely reduced
Pulse oximetry is falsely normal in CO poisoning!
Treatment: 100% O2 (speeds CO dissociation from Hb)

High Altitude Physiology ⭐

Response	Acute	Chronic
PO2	↓	↓
Ventilation	↑ (hypoxic drive)	↑
PaCO2	↓ (hyperventilation)	↓
pH	↑ (respiratory alkalosis)	Compensated
2,3-DPG	-	↑ (right shift)
Hb	-	↑ (polycythemia)
RBCs	-	↑
EPO	-	↑
Pulmonary vasculature	HPV	Remodeling → pulmonary HTN

Exercise Physiology - Respiratory ⭐

VE (minute ventilation) increases proportionally with exercise intensity
VCO2 and VO2 both ↑ with exercise
At anaerobic threshold: VCO2 rises faster than VO2 (excess CO2 from buffering lactic acid)
Breathing during exercise is stimulated by: proprioceptors (first!), then CO2/H⁺/K⁺

QUICK REVISION TABLE: ALL NORMAL VALUES ⭐⭐⭐

Parameter	Normal Value
Tidal Volume (VT)	500 mL
IRV	3000 mL
ERV	1100 mL
RV	1200 mL
TLC	6000 mL
VC	4800 mL
FRC	2300 mL
IC	3500 mL
Anatomical dead space	150 mL
Respiratory rate	12-20/min
Minute ventilation	6 L/min
Alveolar ventilation	4.2 L/min
PiO2 (inspired)	159 mmHg
PAO2 (alveolar)	100 mmHg
PaO2 (arterial)	95-100 mmHg
PvO2 (venous)	40 mmHg
PaCO2	40 mmHg
PvCO2	46 mmHg
SaO2	98%
P50	26-27 mmHg
Normal V/Q	0.8
Lung compliance	200 mL/cmH2O
DLco	25 mL/min/mmHg
FEV1/FVC	>0.75
Hüfner's constant	1.34 mL O2/g Hb

MOST FREQUENTLY ASKED EXAM POINTS 🎯

RV and FRC cannot be measured by spirometry (need helium dilution/body plethysmography)
Normal quiet expiration is passive (no muscle contraction)
Surfactant secreted by Type II pneumocytes; component = DPPC
FEV1/FVC < 0.7 = obstructive pattern
CO2 diffuses 20x faster than O2 (higher solubility despite larger MW)
Central chemoreceptors respond to CO2/H⁺; Peripheral (carotid bodies) respond to hypoxia
PaO2 must fall < 60 mmHg to stimulate peripheral chemoreceptors significantly
Hering-Breuer reflex - lung inflation → stops inspiration (via vagal stretch receptors)
West Zone 3 (base) has the best blood flow; Zone 1 (apex) can have no flow
CO poisoning - PaO2 is normal but SpO2 (pulse ox) is falsely high; treat with 100% O2
Right shift of O-Hb curve: ↑ Temp, ↑ CO2, ↑ H⁺ (acidosis), ↑ 2,3-DPG → aids O2 unloading at tissues
Chloride shift (Hamburger phenomenon) - HCO3⁻ exits RBC, Cl⁻ enters
HPV (Hypoxic Pulmonary Vasoconstriction) - opposite to systemic vessels
2,3-DPG - ↓ in stored blood, ↑ at altitude/chronic anemia
V/Q at apex ~3.3; at base ~0.6 in upright position

Sources: Costanzo Physiology 7th Edition, Ganong's Review of Medical Physiology 26th Edition, Guyton & Hall Textbook of Medical Physiology - cross-referenced and compiled for GK Pal exam syllabus

This is a shared conversation. Sign in to Orris to start your own chat.