Regional anatomy

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Upper Limb - Regional Anatomy (Exam Study Notes)

Source: Gray's Anatomy for Students

1. Overview and Bones

The upper limb is divided into five regions:

Region	Key Bones
Shoulder girdle	Clavicle, scapula
Arm (brachium)	Humerus
Forearm (antebrachium)	Radius (lateral), Ulna (medial)
Wrist (carpus)	8 carpal bones
Hand	5 metacarpals + 14 phalanges

Mnemonic for carpals (proximal to distal, lateral to medial):

Proximal row: Scaphoid, Lunate, Triquetrum, Pisiform
Distal row: Trapezium, Trapezoid, Capitate, Hamate
"Some Lovers Try Positions That They Can't Handle"

2. Brachial Plexus

The most tested topic in upper limb anatomy.

Roots: Anterior rami of C5, C6, C7, C8, T1 - pass between anterior and middle scalene muscles, posterior to subclavian artery.

Brachial plexus - origins from C5 to T1, showing Roots, Trunks, Divisions, and Cords

Schematic (Roots → Trunks → Divisions → Cords → Branches):

Trunks:

Superior trunk = C5 + C6
Middle trunk = C7 alone
Inferior trunk = C8 + T1

Divisions: Each trunk divides into anterior and posterior divisions.

Cords (named by position relative to the 2nd part of the axillary artery):

Lateral cord = anterior divisions of Superior + Middle trunks
Medial cord = anterior division of Inferior trunk
Posterior cord = all three posterior divisions

Key terminal branches:

Cord	Terminal Nerves	Key Functions
Lateral	Musculocutaneous nerve, lateral root of median nerve	Arm flexors; forearm sensation
Medial	Ulnar nerve, medial root of median nerve	Intrinsic hand muscles; ring/little fingers
Posterior	Axillary nerve, radial nerve	Deltoid; all posterior compartment muscles

The "M" over the axillary artery: The musculocutaneous nerve, lateral root of median nerve, median nerve, medial root of median nerve, and ulnar nerve form a visible M-shape over the 3rd part of the axillary artery - a landmark for identifying plexus components in surgery.

3. Axilla

The axilla is the gateway to the upper limb - a pyramidal space formed by the clavicle, scapula, upper thoracic wall, and humerus. It has four walls, an inlet (continuous with the neck), and a floor.

All major structures passing into/out of the upper limb pass through the axilla, including the axillary artery, axillary vein, and brachial plexus.

Key spaces in the posterior axillary wall:

Quadrangular space: transmits axillary nerve + posterior circumflex humeral artery
Triangular space: transmits circumflex scapular artery
Triangular interval: transmits radial nerve + profunda brachii artery into the arm

4. Shoulder Region

Glenohumeral joint - ball-and-socket synovial joint, most mobile in body; least stable.

Rotator cuff muscles (SITS):

Muscle	Action	Nerve
Supraspinatus	Abduction (initiates 0-15°)	Suprascapular (C5, C6)
Infraspinatus	Lateral rotation	Suprascapular (C5, C6)
Teres minor	Lateral rotation	Axillary (C5, C6)
Subscapularis	Medial rotation	Subscapular nerves (C5, C6)

Axillary nerve exits the quadrangular space and innervates the deltoid and teres minor. It wraps around the surgical neck of the humerus - vulnerable in neck-of-humerus fractures and shoulder dislocations.

5. Arm (Humerus Region)

Two fascial compartments separated by medial and lateral intermuscular septa:

Anterior (flexor) compartment:

Muscles: Biceps brachii, brachialis, coracobrachialis
Nerve: Musculocutaneous nerve (C5, C6, C7)
Biceps: long head from supraglenoid tubercle, short head from coracoid process → flexion + supination
Brachialis: main elbow flexor (deep to biceps)

Posterior (extensor) compartment:

Muscle: Triceps brachii (3 heads: long, medial, lateral)
Nerve: Radial nerve (C7, C8)
Radial nerve travels in the spiral groove (radial groove) of the humerus - vulnerable in mid-shaft humeral fractures → wrist drop (inability to extend wrist/fingers)

Main artery: Brachial artery (continuation of axillary) runs in the anterior compartment medial to the biceps tendon, bifurcating at the cubital fossa into radial and ulnar arteries.

6. Elbow Joint

Hinge-type synovial joint allowing flexion/extension; also incorporates proximal radioulnar joint for pronation/supination
Bones: Humerus (trochlea + capitulum) articulates with Ulna (trochlear notch) and Radius (head)
Anular ligament of radius holds the radial head against the radial notch of the ulna; important in pronation/supination
Fat pads lie over the olecranon, coronoid, and radial fossae - displacement ("sail sign") on X-ray indicates intra-articular effusion/fracture
Medial (ulnar) collateral ligament & Lateral (radial) collateral ligament stabilize the joint

7. Forearm

Two compartments:

Anterior (Flexor) Compartment

Three layers, all mainly innervated by median nerve (except flexor carpi ulnaris + medial half of flexor digitorum profundus → ulnar nerve):

Layer	Muscles
Superficial	Pronator teres, Flexor carpi radialis, Palmaris longus, Flexor carpi ulnaris
Intermediate	Flexor digitorum superficialis
Deep	Flexor digitorum profundus, Flexor pollicis longus, Pronator quadratus

Posterior (Extensor) Compartment

All innervated by radial nerve (deep branch / posterior interosseous nerve):

Layer	Muscles
Superficial	Brachioradialis, Extensor carpi radialis longus, ECRB, Extensor digitorum, Extensor digiti minimi, Extensor carpi ulnaris
Deep	Abductor pollicis longus, Extensor pollicis brevis, Extensor pollicis longus, Extensor indicis

Note: Brachioradialis is innervated by the radial nerve before it divides (C5, C6) - flexes the elbow when forearm is in mid-pronation.

8. Carpal Tunnel & Wrist

The carpal tunnel is formed by the carpal bones posteriorly and the flexor retinaculum anteriorly.

Contents of the carpal tunnel (9 tendons + 1 nerve):

Flexor digitorum superficialis (4 tendons)
Flexor digitorum profundus (4 tendons)
Flexor pollicis longus (1 tendon)
Median nerve

The ulnar nerve and artery pass OUTSIDE the carpal tunnel, through Guyon's canal.

Carpal tunnel syndrome: Compression of the median nerve → pain/paresthesia in the lateral 3½ digits, thenar wasting, weak opposition of thumb.

9. Hand

Palmar Arches

Arch	Source	Location
Superficial palmar arch	Mainly ulnar artery + radial superficial branch	Superficial to long flexor tendons
Deep palmar arch	Mainly radial artery + ulnar deep branch	Deep to long flexor tendons, over metacarpals

Allen's test checks adequacy of anastomosis between radial and ulnar arteries.

Nerves of the Hand

Nerve	Sensory	Motor
Median	Lateral 3½ fingers (palmar), distal dorsal tips of these fingers	Thenar muscles (LOAF: Lateral 2 lumbricals, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis)
Ulnar	Medial 1½ fingers (both surfaces)	All other intrinsic hand muscles (interossei, medial 2 lumbricals, hypothenar, adductor pollicis)
Radial (superficial branch)	Dorsum of lateral 3½ fingers (proximal)	None in hand

Thenar vs. Hypothenar Eminences

Thenar (base of thumb): median nerve - abductor pollicis brevis, opponens pollicis, flexor pollicis brevis
Hypothenar (base of little finger): ulnar nerve - abductor digiti minimi, flexor digiti minimi, opponens digiti minimi

Anatomical Snuffbox

Lateral border: Tendons of APL + EPB
Medial border: Tendon of EPL
Floor: Scaphoid + trapezium
Contents: Radial artery (pulse palpable here), terminal branches of superficial radial nerve, origin of cephalic vein
Clinical: Tenderness in snuffbox = scaphoid fracture until proven otherwise

10. Key Clinical Nerve Injuries

Nerve	Injury Site	Deformity	Muscle Loss
Radial nerve	Spiral groove (mid-shaft humerus)	Wrist drop	Cannot extend wrist/fingers
Median nerve	Carpal tunnel	"Ape hand" (thenar wasting)	No thumb opposition
Ulnar nerve	Medial epicondyle (elbow)	"Claw hand" (medial 2 fingers)	Intrinsic hand muscles
Axillary nerve	Surgical neck of humerus	Rounded shoulder	Deltoid paralysis
Musculocutaneous nerve	Axilla	Weak elbow flexion	Biceps/brachialis

Brachial plexus injuries:

Erb's palsy (upper trunk C5-C6): "Waiter's tip" deformity - arm adducted, medially rotated, forearm pronated. Caused by forceful neck-shoulder separation (difficult delivery, motorcycle fall)
Klumpke's palsy (lower trunk C8-T1): Intrinsic hand muscle paralysis + claw hand. May include Horner syndrome if T1 sympathetic fibers involved

11. Superficial Veins

Vein	Course
Cephalic vein	Originates from lateral dorsal venous network → anatomical snuffbox → lateral forearm → deltopectoral groove → drains into axillary vein
Basilic vein	Medial dorsal network → medial forearm → pierces deep fascia → drains into brachial vein → forms axillary vein
Median cubital vein	Connects cephalic and basilic at the cubital fossa - standard IV access site

Quick-Reference Summary Table

Region	Key Nerve	Key Artery	High-Yield Clinical
Shoulder	Axillary (C5-C6)	Posterior circumflex humeral	Rotator cuff tears, shoulder dislocation
Arm	Musculocutaneous (ant), Radial (post)	Brachial	Radial nerve palsy - wrist drop
Elbow	Median, Radial, Ulnar	Brachial bifurcation	Lateral epicondylitis ("tennis elbow")
Forearm	Median (ant), Radial (post), Ulnar (FCU, FDP)	Radial + Ulnar	Pronator syndrome
Wrist/Carpal tunnel	Median	Radial artery	Carpal tunnel syndrome
Hand	Median (lateral), Ulnar (medial)	Superficial + deep palmar arches	Scaphoid fracture, dupuytren's, mallet finger

Gray's Anatomy for Students, Chapter 7 - Upper Limb

Pulmonary edema Criteria Classification Clinical signs and symptoms Examination and evaluation Investigation Management

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Pulmonary Edema - Complete Exam Study Notes

Sources: Harrison's Principles of Internal Medicine 22E, Robbins & Cotran Pathologic Basis of Disease, Guyton & Hall Medical Physiology, Tintinalli's Emergency Medicine, Murray & Nadel's Respiratory Medicine

1. Definition & Pathophysiology

Pulmonary edema is the abnormal accumulation of fluid in the pulmonary interstitium and/or alveoli, impairing gas exchange and lung mechanics.

Fluid accumulates when factors increasing filtration out of the pulmonary capillaries outweigh lymphatic clearance, causing pulmonary interstitial fluid pressure to rise from the normal negative range into positive territory.

Starling forces governing fluid movement:

Increased hydrostatic pressure in capillaries → pushes fluid out
Decreased colloid osmotic pressure (hypoalbuminemia) → less fluid retained in vessels
Increased capillary permeability → protein-rich exudate leaks across alveolar wall
Lymphatic obstruction → impaired fluid removal

Pulmonary Edema "Safety Factor" (Guyton):

Normal pulmonary capillary pressure = ~7 mmHg
Plasma colloid osmotic pressure = ~28 mmHg
Edema does not develop until capillary pressure exceeds ~28 mmHg (acute safety factor of ~21 mmHg)
In chronic elevation (e.g., mitral stenosis), lymphatics hypertrophy 10-fold → patients can tolerate capillary pressures of 40-45 mmHg without lethal edema

2. Classification & Causes

(Robbins & Cotran, Table 15.1)

Type 1 - Hemodynamic (Cardiogenic) Pulmonary Edema

Mechanism	Causes
Increased hydrostatic pressure (most common)	Left-sided heart failure, volume overload, pulmonary vein obstruction
Decreased oncotic pressure	Hypoalbuminemia, nephrotic syndrome, liver disease, protein-losing enteropathy
Lymphatic obstruction (rare)	Lymphangitic carcinomatosis, post-transplant

Type 2 - Non-Cardiogenic (Increased Permeability) Pulmonary Edema

Caused by injury to alveolar walls (microvascular endothelium or alveolar epithelium):

Direct lung injury:

Infections: bacterial pneumonia, viral (SARS-CoV-2), fungal
Inhaled toxins: high-concentration oxygen, smoke, chlorine gas, phosgene
Aspiration: gastric contents, near-drowning
Radiation, lung trauma

Indirect (systemic) injury:

Sepsis/SIRS, burns, pancreatitis, extensive trauma
Blood transfusion-related (TRALI)
Drugs: heroin, cocaine, bleomycin, methadone, amphotericin B, hydrochlorothiazide, paraquat

Type 3 - Edema of Uncertain/Mixed Origin

Cause	Notes
High-altitude pulmonary edema (HAPE)	Hypoxic pulmonary vasoconstriction, rapid ascent
Neurogenic pulmonary edema	CNS trauma/hemorrhage → massive sympathetic surge
Re-expansion pulmonary edema	After rapid drainage of pneumothorax or pleural effusion
Flash pulmonary edema	Acute MI, hypertensive crisis with RAS

3. Killip Classification (Cardiogenic - MI Context)

(Harrison's 22E)

Class	Features	Hospital Mortality (1967)	Modern Mortality
I	No signs of pulmonary or venous congestion	0-5%	~1-2%
II	Moderate HF: basal rales, S3 gallop, tachypnea, right-sided failure signs	10-20%	~5%
III	Severe HF: frank pulmonary edema	35-45%	~10-15%
IV	Cardiogenic shock: SBP <90 mmHg, peripheral cyanosis, confusion, oliguria	85-95%	~50-60%

4. Clinical Signs and Symptoms

Symptoms

Symptom	Details
Dyspnea	Rapid onset at rest; most prominent feature
Orthopnea	Difficulty breathing when lying flat (increased venous return)
Paroxysmal nocturnal dyspnea (PND)	Waking at night, relieved by sitting upright
Cough	May be productive of pink, frothy sputum (alveolar flooding)
Anxiety/air hunger	Due to hypoxemia and sympathetic activation
Fatigue, reduced exercise tolerance	In subacute presentations

Signs on Examination

Respiratory:

Tachypnea (>20 breaths/min), use of accessory muscles
Bibasal crackles (fine crepitations) - fluid in alveoli; "wet crackles"
Wheeze - "cardiac asthma" due to peribronchial cuffing and airway compression
Reduced air entry at bases if pleural effusion present
SpO2 low; central cyanosis in severe cases

Cardiovascular:

Tachycardia
Hypertension (catecholamine release) OR hypotension (cardiogenic shock)
S3 gallop (ventricular volume overload)
S4 gallop (diastolic dysfunction)
Murmurs (mitral regurgitation, aortic stenosis as precipitating cause)
Elevated JVP (right heart failure / volume overload)

Peripheral:

Pitting pedal/ankle edema
Cold, clammy peripheries (low cardiac output)
Hepatomegaly (right heart congestion)

Positional sign: Patient sits upright, leaning forward - cannot lie flat.

5. Examination and Evaluation

Bedside Assessment

Vitals: HR, RR, BP, SpO2 - tachycardia, tachypnea, hypoxia are hallmarks
Position: Patient typically upright, distressed
Respiratory exam: Crackles, wheeze, percussion dullness (effusions)
Cardiac exam: Murmurs, gallops (S3/S4), JVP
Peripheral exam: Edema, perfusion, signs of chronic heart failure
Weight: Recent gain >2 kg is a clue to volume overload

Hemodynamic Parameters (ICU/PAC)

Parameter	Cardiogenic PE	Non-Cardiogenic PE
PCWP	>18 mmHg	Normal (≤18 mmHg)
Cardiac output	Low	Normal or high
Pulmonary vascular resistance	Elevated	Normal/elevated
Protein content of edema fluid	Low (transudate)	High (exudate)

Pulmonary artery catheterization (PAC) is indicated when etiology is uncertain, edema is refractory to therapy, or accompanied by refractory hypotension.

6. Investigations

1. Chest X-Ray (CXR) - Most Important Initial Investigation

Classic CXR findings in cardiogenic pulmonary edema:

Pulmonary edema CXR showing "batwing" bilateral perihilar consolidation (A) and CT showing bilateral perihilar ground-glass with small right pleural effusion (B)

Stage	CXR Finding	Description
Stage 1: Interstitial	Upper lobe vascular diversion (cephalization)	Pulmonary venous pressure 12-18 mmHg
Stage 2: Interstitial edema	Kerley B lines (short horizontal lines at bases), peribronchial cuffing, haziness	PCWP 18-25 mmHg
Stage 3: Alveolar edema	"Bat-wing" / "butterfly" pattern - bilateral perihilar alveolar consolidation; air bronchograms	PCWP >25 mmHg
+	Cardiomegaly (CTR >0.5), bilateral pleural effusions

In non-cardiogenic PE (ARDS): Bilateral diffuse alveolar infiltrates without cardiomegaly or upper lobe vascular diversion; Kerley B lines absent.

2. ECG

Evidence of acute MI (ST elevation, Q waves) → prompt revascularization
Arrhythmias (AF, VT) as precipitants
LVH (hypertensive/valvular disease)
Sinus tachycardia

3. Blood Tests

Test	Purpose / Findings
BNP / NT-proBNP	BNP <100 pg/mL excludes heart failure; BNP >500 pg/mL supports cardiac cause; NT-proBNP <300 pg/mL excludes HF
Troponin (I or T)	Detects ACS as precipitant; elevated in cardiogenic shock
ABG (Arterial Blood Gas)	Hypoxia (↓PaO2), respiratory alkalosis early, metabolic/respiratory acidosis late
Serum electrolytes, U&E, creatinine	Renal function (guides diuretic dosing); hyponatremia = poor prognosis
FBC	Anaemia (precipitant), leukocytosis (infection)
LFTs + albumin	Hypoalbuminemia → reduced oncotic pressure
Serum glucose, HbA1c	Hyperglycaemia in decompensation
Thyroid function (TFTs)	Hypo/hyperthyroidism as precipitant
Blood cultures	If sepsis-triggered non-cardiogenic PE

4. Echocardiography

Identifies systolic vs. diastolic LV dysfunction
Valvular lesions (mitral stenosis, mitral regurgitation, aortic stenosis)
Estimates LVEF (preserved vs. reduced)
Pericardial effusion/tamponade
Wall motion abnormalities (acute MI)

5. Bedside Lung Ultrasound (POCUS)

B-lines (comet-tail artifacts): ≥3 B-lines per intercostal space = interstitial syndrome
More sensitive and faster than CXR for detecting pulmonary edema
Differentiates cardiac from non-cardiac causes of dyspnea (especially useful in emergency)

6. Pulmonary Artery Catheterization (PAC)

Gold standard for differentiating cardiogenic from non-cardiogenic PE
PCWP >18 mmHg = cardiogenic; ≤18 mmHg = non-cardiogenic
Reserved for refractory, uncertain, or complex cases

7. Management

The goal is simultaneous support of oxygenation + treat the underlying cause.

A. Position and Immediate Measures

Sit patient upright with legs dangling - reduces venous return and preload
IV access, continuous monitoring (SpO2, ECG, BP)
Identify and treat precipitants: arrhythmia, MI, infection, non-compliance with medications

B. Oxygenation and Ventilatory Support

Modality	Indication	Details
Supplemental O2	All hypoxic patients	Target SpO2 ≥92% (avoid >98%)
High-Flow Nasal Cannula (HFNC)	Acute hypoxic RF, normal PaCO2	Better outcomes than BiPAP in non-cardiogenic setting
NIV - BiPAP / CPAP	Cardiogenic PE, respiratory fatigue	Reduces preload, improves oxygenation, reduces intubation need; beneficial in cardiogenic PE
Mechanical ventilation (intubation)	Failure of NIV, severe respiratory failure	PEEP reduces preload and afterload; redistributes lung water; improves gas exchange

C. Preload Reduction

Drug	Mechanism	Dose/Route
Furosemide (loop diuretic)	Immediate venodilation then diuresis	IV: 0.5 mg/kg (up to 1 mg/kg in renal insufficiency or chronic use); first-line diuretic
Bumetanide / Torsemide	Alternative loop diuretics	Useful in furosemide resistance
Sublingual GTN (nitroglycerin)	Venodilator + coronary vasodilator; immediate	0.4 mg × 3 doses every 5 min; first-line for cardiogenic PE
IV GTN	Sustained preload/afterload reduction	5-10 μg/min, titrate up if no hypotension
IV Nitroprusside	Potent venous + arterial vasodilator	0.1-5 μg/kg/min; for hypertensive PE; needs arterial line; avoid in reduced coronary perfusion
Nesiritide (IV BNP)	Arterial + venous vasodilation + diuresis	Reserved for refractory cases; avoid in ACS/MI
Morphine	Venodilation, anxiolysis, ↓catecholamines	2-4 mg IV boluses; use cautiously - some registry data show increased mortality
ACE inhibitors	↓Preload and afterload	Especially in hypertensive patients + MI; short-acting agent first

D. Inotropic Support (Reduced Cardiac Output / Cardiogenic Shock)

Drug	Class	Notes
Dobutamine	Sympathomimetic β1-agonist	First-line inotrope; reduces PCWP, increases CO
Dopamine	Catecholamine	Higher doses: vasopressor effect
Milrinone	PDE-3 inhibitor (inodilator)	50 μg/kg loading dose → 0.25-0.75 μg/kg/min; vasodilates + inotrope; avoid in hypotension

E. Renal Replacement Therapy

Indicated when refractory volume overload + metabolic acidosis (pH <7.15-7.25), hypoxemia, or persistent hyperkalemia
Continuous RRT (CRRT) preferred over intermittent HD in hemodynamically unstable patients
In ESRD: urgent dialysis is definitive treatment

F. Treat Underlying Cause (Simultaneous)

Precipitant	Specific Treatment
Acute MI	PCI/revascularization; thrombolytics if PCI unavailable
Arrhythmia	Cardioversion (AF), rate control
Hypertensive emergency	Nitroprusside, IV labetalol
Acute MR / valvular disease	Intra-aortic balloon pump + surgical repair
Infection/sepsis	Broad-spectrum antibiotics
ARDS	Lung-protective ventilation (low tidal volume 6 mL/kg), prone positioning, conservative fluid strategy

G. Long-Term Management (Cardiogenic PE)

ACE inhibitors / ARBs (reduce mortality in HF)
Beta-blockers (carvedilol, bisoprolol) - once stabilized
Mineralocorticoid receptor antagonists (spironolactone/eplerenone)
SGLT-2 inhibitors (empagliflozin, dapagliflozin) - reduce HF hospitalization
Oral loop diuretics for maintenance
Treat underlying cause (revascularization, valve replacement, AF management)

8. Cardiogenic vs. Non-Cardiogenic PE - Key Differentiating Features

Feature	Cardiogenic	Non-Cardiogenic (ARDS)
History	HF, MI, valvular disease	Sepsis, aspiration, trauma
JVP	Elevated	Normal or low
S3 gallop	Present	Absent
Peripheral edema	Present	Absent
CXR heart size	Cardiomegaly	Normal heart size
Kerley B lines	Present	Usually absent
Distribution	Perihilar "bat-wing"	Diffuse, peripheral
PCWP	>18 mmHg	≤18 mmHg
BNP/NT-proBNP	Markedly elevated	May be mildly elevated (sepsis, PE)
Edema fluid protein	Low (transudate)	High (exudate)
Response to diuretics	Good	Poor

Quick-Reference Summary

PULMONARY EDEMA AT A GLANCE
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Cardiogenic (↑PCWP):         Non-Cardiogenic (normal PCWP):
  LVF, MI, MR, AS               ARDS, sepsis, TRALI
  Volume overload                Aspiration, drugs

Symptoms: Dyspnoea, PND, orthopnoea, pink frothy sputum
Signs:    Tachypnoea, crackles, wheeze, S3, ↑JVP, oedema

Investigations:
  CXR: bat-wing, Kerley B, cardiomegaly, effusions
  BNP: >500 = cardiac; <100 = excludes HF
  ABG: hypoxia ± hypercapnia
  ECG: MI, arrhythmia, LVH
  Echo: LV function, valves
  PCWP (PAC): >18 = cardiogenic

Management:
  1. Sit upright + O2 → target SpO2 ≥92%
  2. NIV (BiPAP/CPAP)
  3. Sublingual GTN → IV GTN
  4. IV Furosemide (0.5-1 mg/kg)
  5. Inotropes if low CO (dobutamine)
  6. Treat cause (MI → PCI, AF → rate control)
  7. Renal replacement if refractory
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Harrison's Principles of Internal Medicine 22E, pp. 2373-2374 | Robbins & Cotran Pathologic Basis of Disease, pp. 630-631 | Guyton & Hall Medical Physiology, pp. 508-509 | Tintinalli's Emergency Medicine | Murray & Nadel's Respiratory Medicine

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