Usmle 1 Pulmonary Physiology

• Notochord develops in the 3rd week of gestation

• Brain develops in the 8th week of gestation

• 12th week of gestation the other organ systems begin to form

• Lung develops in 1st trimester

• • It is derived from the Foregut
• • From the lip → 2nd part of the duodenum, including the respiratory tract = FOREGUT

• Surfactant is not completely made until 32-34 wks.

• • Lecithin Sphigomyelin ratio is 2:1 to indicate maturity
•    • < 2/1 = ↓ in surfactant → immature
•       • Beclamethasone → (+) surfactant production
•       • If preterm labor w respiratory distress → give synthetic surfactant via endotracheal tube → ↓ mortality
•    • > 2/1 = ↑ in surfactant → enough for labor = mature lungs
•       • Check for Phosphatidylglycerol →breakdown product of surfactant

• • Function
•    • Surfactant acts as an oil
•    • Main job is to decrease surface tension of alveoli → prevents collapse by keeping the alveoli open
•    • If no sufactant → Atelectasis = collapse of the alveoli

• Diffusion problem

• Collapsed alveoli → no oxygen exchange → Respiratory Distress Syndrome = Pulmonary distress in a Premature Baby:

• • When a premature baby is born he goes into respiratory distress until his alveoli pop open.
•    • Need to give baby Oxygen to create a concetnration gradient that will allow Oxygen to get into the lungs.
•    • More O2= more free radical formation → lungs undergo metaplasia and will form a hyalin membrane

• Induced by giving O2 to a baby who is hypoxic due to atelectasis.

• Try to figure blood gasses:

• • ↓pO2 will cause
• • ↑respiration → ↓pCO2
• • ↑pH

• Restrictive lung disease

• • Need to put baby on a ventilator, PEEP/CPAP
•    • This provides a positive airway pressure to keep the alveoli open → gives some RV
• • Complicaton: bilateral pneumothorax because of the increased pressure required to infuse the oxygen
•    • Will need chest tube.
• • The free radicals made by oxygen will irritate the airway and stimulates mucous production
• • Goblet cell hyperplasia and hypertrophy
• • Narrow airway lumen = Obstructive lung disease → Bronchopulmonary dysplasia (abnormal growth)

• common complication of Hyalin membrane disease

• obstructive lung disease

• Acts like asthma

   • Treated the same

• Majority of children will outgrow O2 by age 2 (when their lungs are almost adult size)

   • Will continue to have obstructive airway disease for the rest of their lives.

• Artifical surfactant is used to ↓ need for O2 and hospitalization

   • 1st give mother beclamethasone to ↑ baby’s own surgactant production

• ARDS –

• • Most common cause
•    • Sepsis
•       • Will need intubation and ICU
•       • Will have same disease course and complications as child
•       • 60% mortality rate

• Most commonly involves the Right main stem bronchus & straight down into the right lower lobe

• If the kid is standing/sitting upright and aspirates, it will go straight down to the superior segment of the R lower lobe

• If the kid is laying down it will enter the posterior segment of the right lower lobe

• Only way to aspirate into the upper lobes is to aspirate the foreign body while lying down on their side

   • Usually a seizure patient

• Always look for foreign body in recurrent R upper lobe pneumonia

• Diagnosis

• • Need to get Inspiratory/expiratory films
• • On inspiration everything inflates
• • On expiration one bronchus remains inflated

• Removal

• • For a child the best way is to lay them on their stomach and performa back thrust
• • For an adult → Heimliech Manuver

• Glottis

• Middle of the trachea (landmark → aortic arch)

• Bifuraction of the Trachea at T4

• MCC of Death → Bronchiectasis

    • bronchi are thickened from inflammation and infection

• Restrictive Disease = problem in the interstitium

• • O2 diffusion will be affected the most
•     • diffusion and perfusion limited
• • CO2 diffuses fast so it is airway limited
•     • airway problems, ventilation problems
• • signs of :dyspnea(SOB), and tachypnea(rapid breathing)
• • ↓pO2 ↓pCO2 ↑pH

• Obstructive Disease = caused by Bacteria producing mucus in Airway

• • increased respiratory rate of dyspnea and tachypnea
• • normal pO2 ↑pCO2 ↓pH

• Function:

• • Create negative pressure around the fetus and absorbs external trauma to the mother’s abdomen
• • In order for the lungs to inflate in the baby you need negative pressure within the amnionic sac.
• • Amnionic fluid is there to keep pressure off of the baby while the negative pressure inflate the lungs

• Composition

• • 80% is filtrate of mom’s plasma
• • Baby must be able to Swallow & digest → then process → adds 20% to it then urinates in the amniotic sac

• baby can’t swallow or absorb fluid (neurological, muscular problem, GI obstruction)

• Mom continues to make 80% of the amniotic fluid but the baby isn’t swallowing it = the baby has a Neuromuscular disease (swallowing is a reflex) or GI obstruction

   • Think of Werdnig – Hoffman Syndrome

• Duodenal or esophageal Atresias can present this way.

• Low amnionic fluid

• Baby has renal defect (agenesis/obstruction) and can’t pee → can’t add 20%

• • Will cause increased pressure on the baby because there is no Amnionic fluid to protect the baby from any trauma
• •

• Potter’s syndrome

• • See the physical manifestation of oligohydramnios
• • ↑atmospheric pressure will cause facial deformity and baby’s facial features to be flattened (due to pressure) = smashed face

• No Abdominal wall muscles, therefore can’t bear down to pee, so there is no muscle to push fluid out creating ­ pressure and a prune like appearance in baby

• This baby will dies of infections (UTI) because always has a catheter

• Extrathoracic (outside chest cavity) and intrathoracic (inside chest cavity) are separated by glottis.

• Breath in → Extrathoracic collapses and intrathoracic expands

• Breath Out → Extrathoracic expands and intrathoracic narrows



• Main stem Bronchus

• • Breaks into parenchyma ½ way and gets smaller
• •

• After Main stain bronchi will divide into

• • large
• • medium
• • small bronchioles

• Terminal Bronchiole

• • Most dependent part of airway → therefore, most Lung Cancers like to form here
• •

• Will deposit in the terminal Respiratory bronchiole

• • Respiratory unit = the only 3 units where O2 Exchange occurs
•    • Resp bronchiole
•    • Alveolus
•    • Alveolar duct
•        • made of 1 layer of epithelium
•        • Can have O2

• Physiologic Dead Space

• • Composed of all CO2
• • Taking a deep breath can clean out the dead space

• Total ventilation = ventilation dead space  + ventilation alveolar

• • TV = VDead Space + VAlveolar 
• • VMinimum = TV x RR
•    • Tidal Volume = 10 – 15 cc/kg
• • Example:
•    • TV = 600 cc
•    • RR = 12
•    • VDS = 40%
•    • What is the ventilation in the alveoli? 

• The true measure of ventilation is in the pCO2 changes

• • If truly ventilating the pCO2 will drop
• • Patients presenting with SOB/tachypnea are not ventilating properly

• 500 cc is not universal!!!

• One can be breathing fast (tachypnic) but not ventilating properly!!!

• Diaphragm normally develops Ventral (midline) → Dorsal (back)

• Diaphragmatic hernia=

• • Intestines are in thoracic cavity
• • Present with bowel sounds in the chest cavity
•    • See a feeding tube curled into his chest on x-ray
• • Common types:
•    • Bochtalek (90%)
•        • Herniation is in the back
• • Morgagni (10%)
•    • Herniation is in the front/mid-line
• • Complication
•    • The lung won’t develop because the GI/Intestines are pushing down on the lungs and can’t inflate à pulmonary hypoplasia
•    • Next step is to try and close the hole
•       • Need at least 90% of the lung to develop in order to live.

• Trachea :

• • Top 1/3 = Squamous cells (protect against abrasion)
• • Middle 1/3 = Transition cells
• • Lower 1/3 = short colunmnar epitherlium
•      • Beat upward → to swallow foreign debris and let stomach acid digest it

• Respiratory Epithelium

• • Tall columnar ciliated epithelium (bottom 1/3 and into bronchus)
• •

• Cilia

• • 9+2 (actin microtubules) configuration =
• • 9 microtubules surrounding 2 actin proteins)
• • Need a Dynein arm to have flexibility

• Dynein arm

• • Allow cilia to dissengage from mucus and push it forward to move it always is only one direction → toward the mouth → orad movement
• • When cough, mucus moves 1”/ cough
• • Sinus drainage → short cough
• • Bronchitis → deeper cough...
• • Also needed in sperm

• Defect of the Dynein Arm →not working = Can’t clear mucus

• Triad

• • Obstruction → Bronchiectasis
• • Infertility → because sperm are immotile
• • Situs inversus (liver/ kidney on other side= midgut rotation)

• Strep Pyogenes

•S pneumonia - encapsulated

• H influenza - encapsulated

• Neisseria Cataralis - encapsulated

• • These bacteria can live in the back of throat because they contain IgA Protease to protect against IgA activity
• • Therefore, they are the MCC of sinusitis, otitis, bronchitis, and pneumonia

• Cilia prevents these bacteria from entering the lung but if the cilia is paralyzed they can enter

• • Viral infections can paralyze cilia and allow for the encapsulated organisms to come into the lung = SUPER – INFECTION
• •

• Goblet cells:

• • Most numerous
• • serve to produce mucus

• Type I pneumocytes (95%) –

• • mostly macrophages
• • Found mostly in terminal bronchus where all the dust will settle

• Type II (5%) pneumocytes

• • produce surfactant
• • Found in alveoli, surrounding alveolar membrane
• • Can become type I, but can’t go the other way round. (Type I can not become Type II

• Dust/ Clara Cells

• • macrophages that ingest dust particles
• • found in terminal bronchus

• found throughout airway down to terminal bronchiole

     • Can’t have anything in the way of O2 diffusion – so will stop in terminal bronchiole

• Most abundant in medium size bronchioles

• • Therefore, the most constriction and dilatation occurs here
• • analogous to blood vessels (contain the most β2 receptors)
• • Asthma is a small airway disease but the wheezing is coming from the Medium bronchioles

• Tracheal and Laryngeal cartilage is of neural crest origin (septum)

• Trachea has 16-20 C shaped cartilage rings

     • Why C-Shape: Opening always faces backwards so esophagus, when full can compress trachea so you are less likely to aspirate.

• Mid main stem bronchus – start fully circling cartilage

      • Because of the lung tissue all around it, if it where not fully encircled it would collapse

• Stops at the Respiratory unit to allow for diffusion

      • Terminal Bronchiole – end of cartilage (because has to be only one layer of cells)

• Stridor: narrowing in extrathoracic airway

• Inspiratory sound only
• Problem is from Lip to the glottis
• need a lateral neck film
• Macroglossia (big tongue) 
• storage disease 
• hypothyroidism 
• Down’s
• 2nd Brachial Arch problem è microagnathia (small jaw)
• Pierre-Robin
• Treacher Collins

• Wheeze: narrowing in intrathoracic airway

• Rhonchi: air moving over mucus

• Crackles: collapsed airways “popping” open

• • Surfactant is missing
• • Alveoli have been scarred down

• Decreased breath sounds: space between alveolus and chest wall is occupied

• Dullness to percussion: as above

• Increased fremitus: consolidation on same side or atelectasis on opposite side

• Bronchophony, egophony, or "ee" to "aa" changes: as above

• Tracheal deviation: towards atelectasis and away from a pneumothorax

• Hyperresonance: pneumothorax on same side or atelectasis on opposite side

• Croup

• Bronchiolitis

• Bronchitis

• Pneumonia

• tracheitis

• Subglottic edema similar to bronchilitis.

• Presentation

• • Barking cough and Stridor
• • Steeple sign on neck X-ray

• Caused by:

• • Parainfluenze
• • RSV (send to ER immediately)
• • Adenovirus
• • Influenza

• Treatment

     • Dexamethasone

• Infectious asthma

• Includes all symptoms of asthma with acute infection

• MC in children < 2 years old → can be able to grow out of it

• Caused by:

• • Parainfluenze
• • RSV (send to ER immediately)
• • Adenovirus
• • Influenza

• URI (Upper Respiratory Infection)

• Acute = ↑ sputem production

• Chonic = ↑ mucous production for at least 3 consecutive months for 2 consecutive years

• MCC:

• • pneumo.
• • influenza
• • Catarallis

• Epiglotitis: H. Influenza B

• Tracheitis: C. Diptheria

• Pneumonia

• closure of trachea

• Presentation

    • Child will be drooling, stridor, muffled voice and fever

• MCC → H. influenza B

• Treatment

• • Must make an airway → Intubate in the ER
•     • Look for thumb sign on CXR

MCC → Diptheria → EF-2 ribosylation = gray pseudomembrane

Stridor since birth

• Inflammation in the alveolus

• MCC

• • Strep pneumonia: Rusty colored sputum
• • H flu: Staph Aureus
• • Neisseria
• • Klebsiella → currant jelly sputem, homeless alcoholic; likes fissures of lung
• • Common after flu → S. aureus
• • Actinomyces → sulfur granules
• • S aureus and pseudomonas → bullae production d/t elastase activity (pneumatocelle)
• • Anaerobic infection – foul smelling; (+) air/fluid levels, gas formation

• Atypicals

• Fungus

• Pneumoconioses

• Nocardia

• Sarcoidosis

• Chlamydia: from 0 to 2 mo

• Mycoplasma: from 10 to 30 y/o

• Legionella: over 40 y/o

• Histoplasmosis: midwest

• Blastomycosis: northeast

• Coccidiomycosis: southwest

• Paracoccidiomycosis: South America

• Aspergillus: moldy hay or moldy basement

• Sporothrix: rose thorn

• Asbestosis

• Silicosis

• Bissinosis

• berrylliosis

the only G+ that is partially acid fast

• noncaseating granulomas; large hilar adenopathy; high ACE levels

• Asthma

• • Intrinsic
• • Congenital
• • Cold air/Colds set this off

• • Extrinsic
• • Environmental
• • Offending agents
• • Dust mites >> Roach droppings >> Pet Dander

• Emphysema

• • Digestion of interstitium by elastase
• • Treat as an OBSTRUCTIVE disease but really is a restrictive disease

• MC intrathoracic = Squamous cell → PTH secretion

• Small Cell Carcinoma 

• • Anaplastic
• • Located at the carina
• • Produces 4 hormones:
•    • ACTH: 90%
•    • ADH: 5%
•    • PTH: 3%
•    • TSH: 2%

• MC Primary Lung CA → Bronchogenic Adenocarcinoma

• Most common lung mass in children is: Hamartoma

• Most common lung mass in adults is: Granuloma

• Most common TUMOR: adenoma

• Intrathoracic space

• • Chest wall
• • Pleural space

• Pulmonary vasculature

• Pulmonary airway

• RV:

• • Residual volume
• • the amount of air left in the lungs AFTER forced expiration
• • Can not be physiologically forced out
• • Maintains some compliance in the airway
• • Keeps alveoli from collapsing

• ERV:

• • Expiratory reserve volume
• • the amount of air that can still be FORCED out AFTER a normal exhalation
• • Fills up the dead space at rest; decreases the tidal volume that you would have to take in

• FRC: 

• • functional residual capacity
• • FRC = RV + ERV

• TV:

• • Tidal volume
• • the amount of air you take IN during a NORMAL inhalation effort
• • 10 – 15 cc/kg

• IRV:

• • inspiratory reserve volume
• • the amount of air you can FORCE INSPIRE after a normal inhalation effort

• TLC:

• • Total lung cap
• • ALL the air in your lungs at the END of a deep breath
• • RV + ERV +TV + IRV

• VC:

• • Volume cap
• • all the air you can breathe in AFTER forced exhalation
• • ERV + TV + IRV

• Obstructive Disease

• • RV changes 1st = ↓
• • In both TV changes last

• Restrictive Disease

• • VC drops 1st; TLC drops next
• • In both TV changes last

• Beginning: expansile forces of the CHEST WALL is greater ( 0 to 49%)

• Middle: expansile forces of the LUNG is greater ( 50 to 99%)

• End: recoil force of the chest wall EQUALS the expansile force of the lung

• Beginning: recoil forces of the CHEST WALL are greater ( 0 to 49%)

• Middle: recoil forces of the LUNG are greater ( 50 to 99%)

• End: the recoil force of the lung EQUALS the expansile force of the chest wall

• FRC: baseline > intrathoraxic pressure is negative ( - 3 to – 5)

• TV: intrathoraxic pressure gets more negative ( -10 to -12)

• TLC: intrathoraxic pressure most negative (-20 to -25)

• Intrathoraxic Pressure should always be NEGATIVE

• Should ALWAYS remain negative

• Should decrease with inspiration

• If it gets positive, then it will resist any blood or air from entering the thorax

• If you do not breathe in, there will be NO pressure gradient for blood to enter the thorax

• Kussmaul sign: increased JVD with inspiration

• Pulsus paradoxicus: exaggerated drop in BP( more than 10mmHg) or pulse ( more than 10bpm) on inspiration

• Mcc: pericardial tamponade or pneumothorax

• is when fluid in the pericardium builds up

• if equal pressure on both sides of chest

• Mcc: trauma or cancer

• CXR: enlarged cardiac shadow

• ECHO: compressed small heart

• Tx: pericardiocentesis

• If recurrent: put in a pericardial window

• if NOT equal pressure on both sides of chest

• Traumatic

• Spontaneous

• • Associated with estrogen use or collagen disease
• • Less than 25% occupation & asymptomatic
• • More than 25% occupation or symptomatic

• Tx: chest tube placement

• As you breathe in, the lung Inflates, pulling on traction fibers attached to vessels

• As vessels DILATE, flow increases

• As flow increases, oxygen dilates the vessels, significantly increasing Q

• The increased Q keeps the pulmonary valve open longer, INCREASING S-2 splitting

• (1) gravity

• (2) less resistance

• (3) more oxygen goes to the bottom of the lungs with each breath

• Normal RR = 12 to 16 breaths/min

• Q increases on inspiration and decreases on expiration.

• It is caused when the closure of the aortic valve (A2) and the closure of the pulmonary valve (P2) are not synchronized during inspiration

• Increases on inspiration due to Increased pulmonary blood flow

• Decreases on expiration due to decreased pulmonary blood flow

• This is why RIGHT sided heart sounds increase on INSPIRATION

• This is why LEFT sided heart sounds increase on EXPIRATION

• Directly related to DIFFUSION and PERFUSION

• More oxygenation is accomplished at the bottom of the lungs only on inspiration

• Most of oxygenation is accomplished at the top of the lungs > ALWAYS OPEN!

• Inversely related to pCO-2

• Definition: patent airway

• Measurement: pCO-2 ( on ABG’s)

• More V to the bottom of the lungs only on inspiration

• Most V at the top of the lungs because it is ALWAYS PATENT

• V /Q is greatest at the top of the lungs, equally matched in the middle, least at the bottom

• If you change one, you MUST change the other in the SAME direction

• ANY V / Q mismatch will lead to hypoxia

• Eisenmeger Syndrome

• • Pulmonary HTN that reverses blood flow
• • Rx:  Nitrous Oxide → dilates pulmonary vessels

• The Only Pressure That Gets Positive With Each Breath

• P_a = P_atm   at IRV and FRC

• P_a < P_atm   at inspiration

• P_a = P_atm   at end of deep breath

• P_a > P_atm   at expiration

• ability to distend and increase volume

• Black = normal

• Red = obstructive leaving air inside

• Blue = emphysema, trouble breathing in and breathing out. (obstruction)

• Carotid Body

• • located at the bifurcation of the internal and external carotids
• • Measures PO2, PCO2, pH, and H+ ions
• • Afferent (CN IX) and Efferent (CN X)

• AORTIC BODY

• • found in the arch of the aorta
• • Measures pCO-2, pH, and H+ ions
• • Afferent and Efferent are both CN X

• J-receptors: found in the interstitium of lungs

• • Senses interstitial particles
• • Increases respiratory rate (Tachypnea)

• Slow adapting receptors: found in the ribs,especially the sternocostal junctions

• • Senses stretch and inflation of ribs
• • Causes exhalation

• Maxillary

• Ethmoid

• Sphenoidal

• Frontal

• More sensitive to elevated pCO-2

• Hypoxia and Hypercarbia (abnormally elevated CO₂) are synergistic



• Forms of pCO-2:

• • regulated in pons
• • 90% in the form of HCO-3 (acid)
• • ↑HCO₃ → metabolic alkalosis → low vol state
• • ↑pCO₂ detected by pneumatic center
• • if u give O₂ it will knock out apneustic center and kill the patient
• • 7% as carbaminohemoglobin and carboxyhemoglobin
• • 3% is dissolved ( .03pCO2 )

• Pneumatic

• Apneustic

• Medulla

• Responsible for BASIC functions; has a RR of 8 to 10

• BRAIN DEAD: no function above the medulla and flat EEG but can still breathe

• COMATOSE: cerebral cortex is still alive, but patient unable to respond

• Central Apnea: NO inspiratory effort, with or without bradycardia, in 20 seconds or more

• • Apnea monitor
• • Tx: Caffiene; theophylline

• Obstructive Apnea: occlusion of airway during sleep, usually caused by obesity

• • Snoring will cause R sided hypertrophy and HF
• • Weight loss
• • Progesterone
• • CPAP
• • Surgery: Uvulopalatoplasty

• RESPONDS to the environment

• Locked-In syndrome: damage to pons; patient only able to blink as response

• Most sensitive to osmotic shifts > Central Pontine Demylinolysis

• Apneustic center: senses hypoxia; causes inspiration

• Pneumotactic center: senses hypercarbia; causes exhalation (obst lung disease)

• pCO₂ regulator

• RAPID, DEEP breathing

• ↑pCO₂

• Means METABOLIC ACIDOSIS

• Pneumotactic center is desensitized, as in COPD

• A lesion below the pneumotactic center but above the apneustic center

• knock out the medulla

• Occurs when ↓ glucose and ↓ blood supply

• Remove ATP from medulla (when hungry)

• Born with a extra, high cervical rib

• When the child turns his head the cervical rib will impinge on the subclavian → a vacuum forms and forces blood to stop being shunted to vertebral artery

• atherosclerosis of proximal subclavian

• Once they raise their arms cut off subclavian artery and pass out

• Seen in elderly

• Bronchitis

• • Acute
• • chronic

• Bronchiolitis

• Asthma

• • Intrinsic
• • extrinsic

• Cystic fibrosis

• Bronchiectasis

• Emphysema

• • Panacinar
• • Centroacinar
• • Distoacinar
• • Bullous

• Staph aureus

• Pseudomonas