PATHO - Term Test III (Respiratory System) Flashcards
The primary function of the pulmonary system is ___________. This function involves three steps which are:
exchange of gases
three steps:
1) ventilation, movement of air in/out of lungs
2) diffusion, movement of gases between air spaces in lungs and bloodstream
3) perfusion, movement of blood into and out of capillary beds of lungs to body organs and tissues
first two functions carried out by pulmonary system, third is by CV system
Structures of the pulmonary system
- two lungs
- upper and lower airways
- blood vessels that serve ^ structures
- diaphragm
- chest wall/thoracic cage
Lung lobe divisions
3 in the R lung (upper, middle lower)
2 in the L lung (upper, lower)
each lobe further divided into segments and lobules; right bronchus is more straight than the left
Mediastinum
space between the lungs that contains the heart, great vessels, and esophagus
_________ is a set of conducting airways that delivers air to each section of the lung
bronchi
The lung tissue surrounding the airways (bronchi) provide what funtion?
supports the airways by preventing distortion or collapse as gas moves in and out during ventilation
Diaphragm
dome-shaped muscle that separates thoracic and abdominal cavities and is involved in ventilation
The lungs are protected from exogenous contaminants through a variety of mechanical barriers. These barriers include what?
- Upper respiratory tract mucosa: Maintains constant temp and humidification of the gas coming into lungs; traps and removes foreign particles, some bacteria, and noxious gases from inspired air
- Nasal hairs and turbinates: trap and rremove foreign particles, some bacteria and noxious gases from inspired air
- Mucous blanket: protects trachea and bronchi from injury; traps most foreign particles and bacteria that reach lower airways
- Cilia: propels mucous blanket and entrapped particles towards oropharynx, where they can be swallowed or expectorated
- Irritant receptors in nares (nostrils): stimulation by chemical or mehanical irritants triggers sneeze reflex, which results in rapid removal of irritants from nasal passage
- Irritant receptors in trachea and large airways: stimulating by chemical or mechanical irritants triggers cough reflex to remove such irritants from lower airways
- Alveolar macrophages: ingest and remove bacteria and other foreign material from alveoli (phagocytosis), release inflammatory cytokines, and present antigens to adaptive immune system
Conducting Airways - structures and function
Structures:
- Upper airways: nasopharynx, oropharynx
- Larynx: connects upper and lower airways
- Lower airways: trachea, bronchi (23 divisions), terminal bronchioles
Function: allow air into and out of the gas-exchange structures of the lungs (no gas exchange occurs here!)
Upper airway structures (i.e. nasopharynx, oropharynx, etc.) are lined with what, which provides what function?
ciliated mucosa that warms and humidifies inspired air and removes foreign particles from it
Which is more efficient at filtering an humidifying air: nose or mouth?
nose
Larynx - Structure and Function
Structure:
- connects upper and lower airways
- consists of endolarynx and surrounding triangular-shaped bony and cartilaginous structures
- endolarynx: false vocal cords (supraglottis) and true vocal cords
- Glottis: slit-shaped space between true cords
- Vestibule: space above false vocal cords
- laryngeal box formed by 3 large cartilages (epliglottis, thyroid, cricoid) & 3 smaller ones (arytenoid, corniculate, cuneiform)
Function:
- supporting cartilages prevent collapse of larynx during inspiration and swallowing
- both set of muscles inolved with swallowing, ventilation, and vocalization
- internal laryngeal muscles control vocal cord length and tension (thus voice pitch); contract during swallowing to prevent aspiration
- external laryngeal muscles move larynx
Trachea - Structure and Function
Structure:
- branches into two bronchi at the carina → each bronchi then enter lungs at the hila (hilum; roots of the lungs) along with pulmonary blood and lymphatic vessels
- progressive branching until alveolar ducts
Function: connects larynx to bronchi, and supported by U-shaped cartilage (connecting conducting airways)
Three layers of the bronchial walls:
1) epithelial lining: single celled exocrine glands (goblet cells and ciliated cells)
- goblet cells produce mucous blanket
- ciliated epithelial cells push mucous towards trachea and pharynx to be swallowed/expectorated via coughing
- layer becomes thinner with progressive bronchi branching
2) smooth muscle layer
3) connective tissue layer
The conducting airways terminate where?
in the respiratory bronchioles, alveolar ducts, and alveoli
Structures considered part of the gas exchange airways include:
- Respiratory bronchioles
- Alveolar ducts
- Alveoli
- together sometimes called the acinus
Pores of Kohn - Structure and Function
Structure: tiny passages in the alveoli that permit some air to pass through septa from alveolus to alveolus
Function: promotes collateral ventilation and even distribution of air among the alveoli
The lungs contain approximately ______ alveoli at birth and ____ by adulthood. Total surface area of alveoli is about _____
25 million (at birth)
300 million (adulthood)
Total SA: ~70 m2 (you can park 20 cars in a space this size!)
The two types of epithelial cells in the alveolus
1) Type 1 alveolar cells: provide structure
2) Type II alveolar cells: secrete surfactant
Lung epithelial cells protect from external environment/foreign entry, needed for adequate gas exchange, regulating ion and water transport, and maintaining mechanical stability of the alveoli
What kind of special immunity cell components do alveoli have and what do they do?
alveolar macrophages - ingest foreign material that reaches the alveolus and prepare it for removal through the lymphatics
Which has lower pressure and resistance: pulmonary circulation or systemic circulation?
If there is a difference, what is the difference?
pulmonary - pulmonary arteries are exposed to ~1/5th of the pressure of systemic circulation (~18mmHg vs 90mmHg in aorta) & normally ~1/3 of pulmonary vessels are perfused at any given time
due to delicate structure of membrane of alveoli
Functions of the pulmonary circulation
- facilitates gas exchange
- delivers nutrients to lung tissues
- acts as a reservoir for LV
- filtering system that removes clots, air, and other debris from the circulation
Describe the branching/divisions of vascular network in pulmonary circulation.
Pulmonary arteries:
- pulmonary artery divides and enters lung at the hila and branches with each main bronchus and with bronchi at every division (meaning every bronchus/bronchiole has an artery/arteriole)
- arteriole divides at terminal bronchioles ⇒ forms capillary network around acinus
Pulmonary veins
- each pulmonary vein drains several pulmonary capillaries and are dispersed randomaly throughout lung before leaving at hila and into LA; has no valves
What are capillary walls made of and why is this beneficial in gas exchange?
- walls made of an endothelial layer and thin basement membrane, which often fuses with alveolar septum basement membrane (VERY LITTLE SEPARATION BETWEEN blood x gas)
- allows for efficient gas exchange
The shared alveolar and capillary walls makes up the _________________. What occurs here and how much blood runs through the alveolar surface area?
alveolocapillary membrane
gas exchange occurs across this membrame, and under normal conditions ~100mL is spread over 70-100 m2 of alveolar SA
True or False. Each bronchus or bronchiole has an accompanying artery or arteriole
True
Hilus
connection where everything goes in (blood vessels, bronchus, nerves) and pulmonary veins go out
Bronchial circulation - Function
- part of systemic circulation
- moistens inspired air and supplies nutrients to the conducting airways, large pulmonary vessels, and pleural membranes
- some of its capillaries draiwn into own venous system, some contribute to the normal venous mix of oxygenated and deoxy blood (right to left shunt)
- DOES NOT participate in gas exchange
Bronchioles are the main resistance vessels in he lungs. Their opening/closing is controlled by what?
smooth muscle
Lymphatic vessels in the lungs - Structure and Function
Structure:
- deep and superficial pulmonary lymphatic capillaries present
- fluid and alveolar macrophages migrate from alveoli to terminal bronchioles which then enters lymphatic system
- vessels leave lung at hilum through series of mediastinal lymph nodes
Function: immune defense, keeping lung free of fluid
Caliber of pulmonary artery lumina ________ as smooth muscle in arterial wall contracts, thus _________ pulmonary artery pressure
decreases; increases
Vasoconstriction and vasodilation in pulmonary circulation is primarily in response to what?
local humoral conditions (even though pulmonary circulation is innervated by ANS)
- relating to body fluids, especially with regard to immune responses involving antibodies in body fluids as distinct from cells
- basically in response to hormones, immunity factors
What is the most important cause of pulmonary artery constriction and what is the mechanism behind this?
- most important cause: low alveolar PO2 (PAO2)
- caused by pulmonary venous hypoxia aka hypoxic pulmonary vasoconstriction
- results from ↑ intracellular calcium levels in vascular smooth muscle cells in response to low [O2] and presence of oxygen radicals
- can be reversible if alveolar PO2 is corrected
- Other causes: acidemia (also reversible)
- note that an elevated PaCO2 with no drop in pH will not cause constriction
- Other biochemical factors affecting vessel diameter: histamine, prostaglandins, serotonin, NO, bradykinin
Where in the lungs can hypoxic pulmonary vasoconstriction occur, and what phsyiological mechanisms cause adaptation to this vasoconstriction?
- can occur in one portion or entire lung
- if one segment: arterioles constrict locally, shunting blood to other well-ventilated areas in lung (reflexively improves efficiency by ↑ ventilation and perfusion matching)
- if all segments: vasoconstriction throughout pulmonary vasculature, results in pulmonary hypertension
- chronic alveolar hypoxia = permanent structural changes, pulmonary HTN, eventually leads to RHF (cor pulmonae)
Chest wall - Structure and Function
Structure: skin, ribs, intercostal muscles
Function: protects lungs from injury
- intercostal muscles: muscular work of breathing (in conjunction with diaphragm, accessory muscles, and abdominal muscles)
Thoracic cavity is contained by what structure?
Thoracic cavity encases what structure?
contained by: chest wall
encases: lungs
Pleura & pleura space - Definition
Pleura: serous membrane that adheres to the lungs (visceral pleura) and folds over itself to attach to chest wall (parietal pleura)
Parietal pleura: lines interior surface of thoracic wall and diaphragm; has costal, diaphragmatic, and mediastinal parts
Visceral pleura: adheres to surface of the lung
Pleural space/cavity: the area between the two pleurae, normally filled by a thin layer of intrapleural fluid secreted by pleura to lubricate pleural surfaces (<0.02mm thick, to allow them to slide over each other without separating); intrapleural pressure is usually -ve/subatmospheric (-4 to -10mmHg)
- usually the space is a potential space rather than a real space
3 functions of the pulmonary system
1) ventilates alveoli
2) diffuses gases into and out of blood
3) perfuses lungs so that organs and tissues of the body receive blood rich in oxygen and deficient in CO2
Definitions: Ventilation vs Respiration
Ventilation: the mechanical movement of gas or air into and out of lungs
Respiration: the exchange of oxygen and CO2 during cellular metabolism
Resp Rate
ventilatory rate/number of times gas is inspired and expired per minute
Minute voluume/minute ventilation calculation
ventilatory rate (breaths per min) x amount of air per breath (tidal volume)
expressed as litres per minute
Define tidal volume and state what the average tidal volume is
the amount of air that moves in or out of the lungs with each respiratory cycle
avg: 500cc of air per breath
Calculate the minute volume for a patient who is breathing 12 breaths per minute.
500cc (tidal volume) x 12 breaths per min = 6000 mL (or 6L)
The lung eliminates ___________ mEq of carbonic acid every day in the form of CO2, which is produced at a rate of ~ ________.
10 000 mEq
200 ml/min
Normal arterial CO2 pressure (Paco2)
40 mmHg
Dead-space ventilation (VD)
volume of air per breath that does not participate in gas exchange (i.e. ventilation without perfusion)
Anatomic dead space vs. alveolar dead space
Anatomic dead space: volume of air in the conduct airways (~150mL)
Alveolar dead space: volume of air in unperfused alveoli
dead space is ~ equivalent to the ideal body weight in lbs
How to calculate effective ventilation
(ventilatory rate x tidal volume) - dead space
Alveolar ventilation
the exchange of gas between the alveoli and the external environment (O2 in and CO2 out)
What actions would voluntary breathing be necessary?
talking, singing, laughing, and deliberately holding one’s breath
Respiratory center - Describe where it is located, what is controls, and its components
Location: brainstem
Function: controls respiration by transmitting impulses to respiratory muscles to cause them to relax/contract
Components: made of several groups of neurons
- dorsal respiratory group (DRG)
- ventral respiratory group (VRG)
- pneumotaxic center
- apneustic center
The basic automatic rhythm of respiration is set by what component of the respiratory center? What input does this center get in order to know how to regulate resp rate?
DRG - dorsal respiratory group
Receives afferent input from:
- peripheral chemoreceptors (in carotid and aortic bodies)
- mechanical, neural, and chemical stimuli
- lung receptors
Is ventral respiratory group (VRG) active during normal quiet respiration?
Nope. It’s go tboth inspiratory and expiratory neurons but it usually inactive during normal breathing; becomes active with increased ventilatory effort
Location and Function of: pneumotaxic center and apneustic center
Location: pons
Function: not part of generating primary rhythm; act as modifiers of the rhythm established
Pattern of breathing can be influenced by what 3 factors?
emotion, pain, disease
Identify the types and briefly describe the structure/function of lung receptors.
- they all send impulses from lungs to DRG
1) Irritant receptors (C fibers) - found in epithelium of all conducting airways
- sensitive to vapors, gases, and particulate matter (like inhaled dust)
- causes cough reflex
- also cause bronchoconstriction and increased ventilatory rate
2) Stretch receptors - in smooth muscles of airways
- sensitive to increases in size/volume of lungs
- decreases ventilatory rate and volume when stimulated (aka Hering-Breuer expiratory reflex)
3) J-receptors - aka juxtapulmonary capillary receptors (sensory nerve endings) found near capillaries in alveolar walls/septa
- innervated by vague nerve
- sensitive to increased pulmonary capillary pressure (reflex response: apnea (? noted in carolyn’s notes) followed by rapid, shallow breathing, hypotension, and bradycardia) - pulmonary chemoreflex
- respond to things like ex. pulmonary edema, PE, pneumonia, CHF, barotrauma, hyperinflation of lung, IV/intracardiac administration of chemicals like capsaicin
Hering-Breuer reflex
What is it, and discuss the difference in stimulation of this reflex in newborns vs adults.
a reflex triggered to prevent the over-inflation of the lung
reflex is active in newborns to help with ventilations; in adults, this reflex kicks in during high tidal volumes (ex. exercise) to protect excess lung inflation
Innvervation of the lung
1) Sympathetic division: branches from upper thoracic and cervical ganglia of the spinal cord
- contributes to smooth muscle tone, causes it to relax
2) Parasympathetic division: nerve fibers travel in vagus nerve to the lung; main controller of airway caliber (diameter of airway lumen) under normal conditions
- receptors under this division when stimulated, will cause smooth muscle contraction
Central chemoreceptors
Structure/location: near resp center
Function: monitor arterial blood (indirectly) via pH changes of CSF (i.e. sensitive to very small changes in H+ concentration and pH in CSF)
- CSF pH reflects arterial pH beccause CO2 can diffuse across BBB into CSF until Pco2 is equal on both sides
- CO2 entered into CSF combine with H2O to make carbonic acid which gives away its H+ causing stimulation of central chemoreceptors
- increases in Paco2 cause chemoreceptors to sense it and stimulate resp center to increase depth and rate of ventilation ⇒ Pco2 in arterial blood 2 diffuses out of CSF ⇒ pH returns to normal
In what situations wlil central chemoreceptors not be sensitive to small changes in Paco2 thus pH, and therefore have poor regulation over ventilations?
- with inadequate ventilation/hypoventilation that is LONG TERM (like COPD), central chemoreceptors become insensitive to these small changes
Peripheral Chemoreceptors
Location: carotid bodies and aortic arch
Function:
- sensitive to Pao2
- when Pao2 and pH decrease, these receptors stimualte resp center to increase ventilation (but Pao2 has to be <60 mmHg to have influence on the ventilation changes)
- become the major stimulus to ventilation when central chemoreceptors become insensitive to chronic hypoventilation
In typical normal healthy humans, we use (CO2/O2) to drive our ventilations.
In individuals with chronically elevated CO2 levels, (CO2/O2) is used to drive ventilations
normal healthy: CO2
chronic high levels of CO2 patients: O2 (using a hypoxic drive to stimulate breathing)
Will ASA cause people to (hyper/hypo-) ventilate. Why?
hyperventilate because it’s acidic (acetylsalicylic acid) so body tries to blow it off
Opioids cause people to (hyper-/hypo-) ventilate. Why
- hypoventilate
- it tells your resp center that it doesn’t need to breathe anymore so you stop breathing
A patient with DKA with hyper/hypoventilate.
Hyperventilate - because they have too much sugar causing creation of acid (from metabolism)
The mechanics of breathing involved three aspects which are:
1) major and accessory muscles of inspiration and expiration
2) elastic properties of the lungs and chest wall
3) resistance to airflow through conducting airways
The major muscles of inspiration are:
The accessory muscles of inspiration are:
Major: diaphragm, external intercostal muscles
Accessory muscles: sternocleidomastoid, scalene muscles
Diaphragm - Structure and Function
Structure: dome-shaped muscle separating abdominal and thoracic cavities
- motor nerves of diaphragm exit from spinal cord from C3-C5 and run downward as phrenic nerve
Function: changes size of the chest cavitiy - increases volume when it contracts and flattens doward (creates a negative pressure that draws gas into lungs)
- contraction of external intercostal muscles elevate anterior portion of ribs and increase thoracic cavity volume via front to back diameter (from anterior - posterior)
- inspiration at rest USUALLY assisted by diaphragm only
Intercostal muscles are innervated by
intercostal nerves which leave the spinal cord between T1-T11, corresponding with muscle position
Function of accessory muscles of inspiration
- enlarge thorax by increase A-P diameter (but not as efficiently as diaphragm)
- assist inspiraiton when minute volume (volume of air inspired and expired per min) is high (exercise, disease causing increased work of breathing)
What are the major muscles of expiration?
trick question! there are none because normal, relaxed expiration is passive and requires no muscular effort
Accessory muscles of expiration - identify them and their function
abdominal and internal intercostal muscles
function: assist expiration when minute volume is high, during coughing, or when airway obstruction is present
- abdominal muscles contract to increase intra-abdominal pressure which pushes the diaphragm up and decreases the thoracic volume = expiration
- internal intercostal muscles pull down the anterior ribs to decrease AP diameter
Which level of the vertebrae, if transected/damaged, would cause loss of all use of respiratory muscles?
If the spinal cord is injured below ___, the diaphragm continues to work and some ventilation occurs.
resp muscle paralysis: above C3
some ventilation: below C5
Surface tension
refers the the tendency for liquid molecules that are exposed to air to adhere to one another, occurs at any gas-liquid interface
(think when you fill the glass with water to the top and it looks like it’s going to spill over but it doesn’t even if you’ve filled more than the glass you can hold - that’s surface tension)
Describe how the law of Laplace is used to determine the pressure required to keep an alveoli (in the shape of a sphere) open.
Law of Laplace: P = 2T/r
Pressure (P) equals to 2 x surface tension divded by radius of sphere
so the smaller the alveolar radius, the more and more pressure is requirerd to inflate it which were make taking breathes EXTREMELY dificult
Surfactant
- a lipoprotein (90% lipids, 10% protein) produced by type II alveolar cells that allow for alveolar ventilation because it lowers surface tension by coating the air-liquid interface of the alveoli
- includes two groups of surfactant proteins
- 1) has small hydrophobic molecules with detergent-like effect to separate liquid molecules (this decreases alveolar surface tension)
- 2) collectins - large hydrophilic molecules capable of inhibiting foreign pathogens
- allow alveoli to expand uniformly (on inspiration) and prevents it from collapsing on itself (on expiration)
At what age does surfactant production start?
starts ~2 weeks after they are born
major complication in preemies as their bodies don’t make enough surfactant so alveoli cannot open completely and trouble breathing
What would happen if surfactant was not produced in adequate quantities?
alveolar surface tension increases which causes alveolar collapse, decreased lung expansion, increased work of breathing, and severe gas-exchange abnormalities
The elasticity of the lung is caused by:
1) elastin fibers in alveolar walls and surrounding the small airways and pulmonary capillaries
2) surface tension at alveolar air-liquid interface
Elasticity of the chest wall is a result of
its bone and musculature configuration
Elastic recoil
tendency of the lungs to return to resting state after inspiration
- normal elastric recoil allows for passive expiration but may be insufficient for labored breathing (accessory muscles of expiration kick in here)
- ^ muscles also kick in in diseases like emphysema when disease compromises the elastic recoil/blocks conducting airways
What are the two opposite forces of recoil in the lungs and chest wall that keep it in equilibrium?
1) tendency for chest wall to recoil by expanding outward
2) tendency for lungs to recoil/inward collapse around the hila
these opposing forces create the small negative intrapleural pressure; happens at the end of expiration (resting level) where functional residual capacity is reached (volume remaining in lungs after normal passive expiration)
- we just overcome the the tendencies when we breathe in and out (i.e. overcome lung’s resistance to expand out by use of diaphragm and intercostal muscles)
Compliance
- measure of lung and chest wall distensibility; defined as volume change per unit of pressure change (or the amount of pressure that is must be generated to expand the lungs with a given volume)
- represents the relative ease of structures to be stretched (OPPOSITE of elasticity)
- ex. if compliance is improving = you need to exert less pressure to move the same volume of air; if a patient has decreased compliance for whatever reason (like increasing pulmonary edema) you’ll need to ventilate harder to build more pressure to move that same amount of air
Increased compliance means
lungs and chest wall are easier than normal to inflate and has lost some elastric recoil
Factors that increase compliance
Factors that decrease compliance
Compliance increases with: normal aging, disorders like emphysema
Compliance decreases with: those with ARDS, pneumonia, pulmonary edema, fibrosis
Airway resistance is determined by what factors?
length, radius/diameter, cross-sectional area of airways
density, viscosity, and velocity of gas (Poiseuille law)
Equation for airway resistance, also known as:
R = P/F (aka Ohm law)
Pressure (P)
rate of flow (F)
Describe how airway resistance changes throughout the conducting airways
- airway resistance normally very low
- 1/2 - 2/3rd of total airway resistance occurs in the nose
- next highest resistance is in oropharynx and larynx
- very little resistance in conducting airways of lungs (due to large cross-sectional area)
Define:
Inspiratory reserve volume (IRV)
Expiratory reserve volume (ERV)
Vital Capacity (VC)
Inspiratory reserve volume (IRV): amount of air that can be inspired forcefully after normal tidal volume inspiration, ~3300mL
Expiratory reserve volume (ERV): amount of air that can be forcefully expired after normal tidal volume expiration, ~ 1000mL
Vital Capacity (VC): the largest volume of air that can be moved in and out during ventilation, ~4500 - 5000mL
How is work of breathing determined?
by muscular effort (therefore oxygen and energy) required for ventilation
Work of breathing increases when
- muscular effort increases
- happens when lung compliance decreases in diseases like pulmonary edema
- chest wall compliance decreases (in spinal deformity, obesity)
- obstructed airways via bronchospasm or mucous plugging
- this increase can result in marked increase in o2 consumption and inadbility to maintain adequate ventilation
Define Gas transport
the delivery of oxygen to the cells of the body and removal of CO2
List the four steps in gas transport of oxygen to cells
1) ventilation of the lungs - air in and out of lungs
2) diffusion of oxygen from alveoli into capillary blood - high [O2] to low [O2]
3) perfusion of systemic capillaries with oxygenated blood - no exchange happening yet!
4) diffusion of oxygen from systemic capillaries into cells - blood to interstitial fluid and into the cells
List the four steps of gas transport of CO2
1) diffusion of CO2 from cells into systemic capillaries
2) perfusion of pulmonary capillary bed by venous blood
3) diffusion of CO2 into the alveoli
4) removal of CO2 from lung by ventilation
Non-respiratory functions of the respiratory system (6)
1) provides a route for water loss and heat elimination - i.e. panting
2) enhances venous return - pressure in lungs puts pressure on vena cava to increase venous return
3) contributes to maintaining normal acid base balance - CO2 and pH levels regulating RR
4) enables speech, singing, and other vocalization
5) defends against inhaled foreign material - thanks to long trachea and nasal passageways that gives lots of SA to stop foreign material getting into the lungs
6) removes, modifies, activates or inactives various materials passing through pulmonary circulation - interacts with kidneys and RAAS (i.e. low oxygen may cue body to think that there is low Hb and stimulate kidney to make more erythropoietin to sitmulate bone marrow to make more RBCs)
Define: Barometric pressure (PB) and identify the barometric pressure at sea level
aka atmospheric pressure; the pressure exerted by gas molecules in air at specific altitudes
sea level: 760mmHg (the sum of pressures exerted by each gas in the air at sea level)
Define partial pressure and identify the main gases in the atomsphere.
describes the portion of the total pressure exerted by an individual gas
Main gases (at sea level): oxygen (20.9%); nitrogen (78.1%), and the few other trace gases
Calculate partial pressure of oxygen at sea level.
20.9% (% of oxygen in the air) x barometric pressure (PB which is 760 mmHg) = 159mmHg
note: you have to take into consideration water vapor as it will always exert a pressure when gas enters the lungs and becomes humidifed (so partial pressure of oxygen may be lower)
The amount of water vapor contained in a gas mixture is determined by:
a) temperature of the gas
b) barometric pressure
c) length of time exposed to water vapor
d) both temperature of gas and barometric pressure
a) temperature of the gas
At body temp (37C), water vapor exerts a pressure of 47 mmHg regardless of total barometric pressure. Therefore in saturated air (humidified) at sea level, the partial pressure of oxygen is:
(760 - 47) x 0.21 = 149 mmHg
water vapor has to be taken into account because when gas enters the lungs, it becomes saturated with water vapor (humidified) as it passes through the upper airways
Fraction of inspired oxygen (FIO2)
% of O2 in the inspired air (20.9%)
Formula to calculate PO2 available for diffusion into the blood
(Barometric pressure - water vapor) x FIO2 - (PaCO2/respiratory quotient)
(760 - 40) x 0.209 - (40/0.8) = 99mHg available for diffusion into blood
The adequacy of ventilation to deliver O2 to the alveoli can’t be measured directly, so it’s estimated by measuring the removal of CO2 from the blood (which is calculated by dividing the PaCO2 by the respiratory quotient (0.8))
Effective gas exchange depends on an approximately even distribution of what two components in all portions of the lungs, which are represented by what during measurements?
gas and blood
ventilation, perfusion (your V and Q)
When an individual is in an upright position (sitting/standing), the alveoli in which part of the lungs are less compliant meaning it’s more difficult to inflate. Why?
upper portion alveoli (in the apices) more difficult to inflate!
- when upright, gravity pulls the lungs down towards the diaphragm and compresses the bases of the lungs
- the alveoli in the apices have greater residual volume of gas, are bigger and less ness numerous compared to the bases
- surface tension increases as alveoli become larger, so the upper portions of the lungs are more difficult to inflate (less compliant) than the smaller alveoli in the lower portions of the lungs
- so during ventilation, most of the tidal volume is distributed to the bases of lungs where compliance is greater (ventilation is better in the basesssss)
For an individual in an upright position, perfusion is greatest where in the lungs?
greater perfusion in the bases of the lungs!
- in a standing position, heart has to pump against gravity to perfuse pulmonary circulation but some of that BP is dissipated when trying to go against gravity
- so BP at the apices is < at the bases and ↑ BP = ↑ perfusion so the bases would be better perfused
If a standing individual lays down or is side lying, which area of the lungs become best ventilated and perfused?
the areas that are most gravity-dependent (lower lobes that are also closer to the ground)
How does alveolar pressure gas pressure in the alveoli) affect distribution of perfusion in the pulmonary circulation?
depending on the gas pressure in the alveoli and pressure in the capillary bed in the venous/arterial side. If alveolar pressure > BP in capillary, then the capillary collapses and no blood flows through (this is most likely to happen in the areas of the lungs where BP is the lowest and gas pressure is the highest)
most likely to occur in the apices of the lungs
Describe the three different zones in the lungs that are used to describe how alveolar, venous, and arterial blood pressure affect perfusion distribution.
Zone I: PA > Pa > Pv
- alveolar pressure is the greatest so capillary bed collapses and normal blood flow ceases
- usually a very small part of the lung at the apex
Zone II: Pa > PA > Pv
- alveolar pressure is greater than venous pressure but not arterial pressure
- blood flows through this area but somewhat impeded by alvelar pressure
- normally above level of left atrium
Zone III: Pa > Pv > PA
- arterial and venous pressures are greater than alveolar pressure
- blood flow throug here not affected
- base of the lung
Describe what the following represents:
a) V/Q = 1
b) V/Q < 1
c) V/Q = 0
a) V/Q = 1 - means with every breath, you will get all the air available for perfusion (ideal world where there is not anatomical dead space)
b) V/Q < 1 - ventilation ↓, normal perfusion (seen in those with respiratory conditions characterized by bronchospasm, ex.) OR 0.8 would be normal conditions due to anatomical dead space
c) V/Q = 0 - no ventilation, normal perfusion (occlusion happening)
What does a right shift on the oxyhemoblogin dissociation surve mean and what can cause this?
Means: Hb has decreased affinity for oxygen, facilitates increased ease of oxygen to offload from Hb into the tissue cells
Causes: acidosis (low pH) and hypercapnia (↑ Paco2)
- increased CO2 and H+ levels decrease the affinity of Hb for oxygen
- it’s done to compensate for increased CO2 (you want to pick up more CO2 to bring back to the lungs by letting go of more O2
-
Other causes: hyperthermia, increased 2,3-DPG, increase in exercise level (bc increased metabolic activity)
mneumonic to remember the causes: CADET, face right (CO2, acidity, DPG, exercise, tempreature)
What does a left shift on the oxyhemolbogin dissociation curve mean and what causes it?
Means: Hb has increased affinity for oxygen, promoting assocaition in the lungs and inhibiting dissociation in the tissues
Causes: alkalosis (high pH) and hypocapnia (decreased Paco2)
- in the lungs, CO2 diffuses from blood into alveoli so blood CO2 level is reduced and affinity of Hb for oxygen is increased so that more O2 can be transported from lungs into the tissues
- Other causes: hypothermia, decreased 2,3-DPG (substance normally present in erythrocytes)
Clubbing
selective bulbous enlargement of the distal segment of a digit (fingers or toes), painless
- severity grading from 1-5 based on extent of nail bed hypertrophy and amount of changes in nails themselves
- rarely reversible
-
Causes: common diseases that disrupt normal pulmonary circulation and cause chronic hypoxemia (bronchiectasis, CF, pulmonary fibrosis, lung abscess, congenital heart disease
- potentially also lung cancer without hypoxemia due to inflammatory cytokines (hypertrophic osteoarthropathy)
- Mechanism: unknown but potentially whole megakaryocytes enter systemic circulation and become impacted in the fingertip circulation ⇒ fragments that activated to release platelet derived growth factor (PDGF) which promotes growth, vascular permeability, and monocyte/neutrophil chemotaxis ⇒ more vascular smooth muscle cells and fibroblasts ⇒ periosteal changes near nail bed
V/Q mismatch refers to what
abnormal distribution of ventilation and perfusion
Describe what shunting is in terms of V/Q mismatch
- low V/Q (inadequate ventilation of well-perfused areas of the lungs)
- occurs in atelectasis, asthma due to bronchoconstriction, pulmonary edema & pneumonia when alveoli are filled with fluid
- when blood passes through portions of the pulmonary capillary bed that receive no ventilation, pulmonary capillaries in that area constrict causing a right to left shunt (no oxygen picked up and it just continues on to back to the LA) resulting in decreased systemic PaO2 and hypoxemia
Flail chest
Description: fracture of several consecutive (two or more adjacent) ribs in two or more places OR fracture of the sternum and several consecutive ribs causing instbaility of the chest wall and paradoxical movement of the flail segment
S/S: on inspiration, unstable portion moves inward while chest expands; on expiration it moves outward while chest wall falls (paradoxical movement)
- you will also see movement of mediastinum towards opposite lung during inspiration
- decreased tidal volume so increased RR to compensate (TEMPORARILY) but many progress to hypercapnic respiratory failure
Treatment: hand on injury
- SPLINT x VENTILATION
- possible intubation
- stabilize flail segment
- load and go
- Monitor for:
- pulmonary contusion/cardiac contusion (which can contribute to hypoxia)
- hemothorax
- pneumothorax
Pneumothorax
Description: presence of air or gas in pleural space due to rupture in visceral pleura (the one that surrounds the lungs) or parietal pleura and chest wall
Physiology: air separates the visceral and parietal pleurae which destroys the negative pressure in the pleural space and disrupts eqm b/w elastic recoil forces between lung and chest wall
- lung tends to recoil by collapsing toward hilum
List the muscles involved in inspiration and expiration as shown in the diagram.
Atelectasis
Description, Types, Pathophysiology, S/S, Treatment
Description: collapse of lung tissue; 3 types
- 1) Compression atelectasis: caused by external pressure exerted by tumor, fluid, air in pleural space or by abdominal distention pressing on a portion of lung, causing alveoli to collapse
- 2) Absorption atelectasis: results from removal of air from obstructed or hypoventilated alveoli (gradually absorbed out and into the blood, and then the lungs collapse) or from inhalation of concentrated oxygen (replacing nitrogen) or anesthetic agents
- 3) Surfactant impairment (adhesive) atelectasis: results from decreased production or inactivation of surfactant (can’t reduce surface tension can’t prevent lung collapse after expiration) → can occur due to premature birth, aspiration, ARDS, anesthesia induction, or mechanical ventilation
Pathophsyiology: tends to occur after surgery especially in those who have been given general anesthesia (post-op ppl often in pain, breathe shallowly, don’t wanna move and thus producing viscous secretions that tend to pool in dependent portions of the lungs i.e. thoracic and upper abdominal surgery
- atelectasis causes ↑ shunt, ↓ compliance, V/Q mismatch may lead to perioperative hypoxemia
S/S: dyspnea, cough, fever, leukocytosis (Easily mistaken with infection)
Treatment: prevention of post-op atelectasis
- deep breathing exercises - promotes ciliary clearance of secretions; stabilizes alveoli by redistributing surfactant, promotes collateral ventilation through pores of Kohn (promotes expansion of collapse alveoli)
- frequent position changes
- early ambulation
- Post-op noninvasive positive pressure ventilation (NIPPV) in high risk individuals
Pulmonary Edema
Description: excess water in the lung
Predisposing factors: heart disease, ARDS, inhalation of toxic gases
Pathophysiology:
- 1) most common cause: L sided heart disease → when LV fails, filling pressures on this side of the heart increase causing an increase in pulmonary capillary hydrostatic pressure → when hydrostatic pressure > oncotic pressure in capillaries, fluid moves from capillay into interstitial space (between alveoli and capillary)
- when lymphatic system cannot keep up with removing fluid, pulmonary edema occurs
- 2) second cause: capillary injury that increases capillary permeability (ARDS, inhalation of toxic gases) → capillary injury and inflammation causes water and plasma proteins to leak out of capillary and move into interstitial space (↑ interstitial oncotic pressure) → water moves out of capillary and into lung
- 3) another cause: obstruction of lymphatic system by tumors/fibrotic tissue; by increased systemic venous pressure
S/s: dyspnea, hypoxemia, increased WOB; inspiratory crackles (rales), dullness to percussion over lung bases
- if severe edema: pink frothy sputum, hypoxemia worsens, hypoventilation with hypercapnia may develop
Treatment: depends on cause
- if due to ↑ hydrostatic pressure due to HF: improving cardiac output (diuretics, vasodilators, improving cardac muscle contraction) & oxygen
- If due to ↑ capillary permeability resulting from injury: removing offending agent, support and maintain adequate ventilation and circulation & oxygen
- potentiall mechanical ventilation is
Acute lung injury (ALI)/Acute Respiratory Distress Syndrome (ARDS)
Description, Predisposing factors/causes, pathophysiology, S/S, diagnosis, treatment
Description: represent a spectrum of acute lung inflammation and diffuse alveolocapillary injury
- Defined as:
- 1) acute onset of bilateral infiltrates on chest radiograph
- 2) low raito of PaO2 to FIO2 under positive airway pressure
- 3) not derived from hydrostatic pulmonary edema
Predisposing factors/causes: genetic factors, sepsis, multiple trauma
- other causes: pneumonia, burns, aspiration, cardiopulmonary bypass surgery, pancreatitis, blood transfusions, drug OD, inhalation of smoke/noxious gases, fat emobli, high supplemental [O2}, radiation therapy, DIC
- high mortality rate
- >30% of ICU cases are complicated by ARDS
Pathophysiology: causes acute injury to alveolocapillary membrane ⇒ massive pulmonary infection, increased capillary permeability, severe pulmonary edema, shunting, V/Q mismatch, and hypoxemia
- ARDS can occur directly (gastric acids, toxic gases) or indirectly (sepsis, trauma, etc.); progresses through 3 overlapping phases:
-
1) Exudative phase (within 72 hours): neutrophils and other cells release inflammatory cytokines which damage alveolocapillary membrane + ↑ capillary permeability ⇒ fluid and shit leaks out from capillary to pulmonary interstitium and flood alveoli (hemorrhagic exudate)
- surfactant inactivated
- causes pulmonary edema and hemorrhage ⇒ decreased lung compliance and imapred alveolar ventilation
- inflammatory cytokines also cause pulmonary vasoconstriction = V/Q mismatch
-
2) Proliferative phase (within 4-21 days): pulmonary edema resolves; type II pneumocytes, fibroblasts, and myofibroblats proliferate
- exudate becomes a cellular granulation and looks like hyaline membranes
- progressive hypoxemia
-
3) Fibrotic phase (within 14-21 days): remodeling and fibrosis of lung tissue
- fibrosis progressively obliterates alveoli, resp bronchioles, and interstitium leading to ↓ in FRC and continuing V/Q mismatch with severe RL shunt
- acute respiratory failure
-
1) Exudative phase (within 72 hours): neutrophils and other cells release inflammatory cytokines which damage alveolocapillary membrane + ↑ capillary permeability ⇒ fluid and shit leaks out from capillary to pulmonary interstitium and flood alveoli (hemorrhagic exudate)
Clinical Manifestations: progressive from 1-6
- dyspnea and hypoxemia c/ poor response to supplemental oxygen
- hyperventilation and resp alkalosis
- ↓ tissue perfusion, metabolic acidosis, and organ dysfunction
- ↑ WOB, ↓ tidal volume, hypoventilation
- hypercapnia, resp acidosis, worsening hypoxemia
- resp failure, ↓CO, hypotension, 💀
Diagnosis: hx of lung injury, physical exam, blood gas analysis, radiologic exam, measurement of serum biomarkers
Treatment: EARLY DETECTION, supportive therapy, preventing complications
- supportive therapy
- maintaining adequate oxygenation and ventilation while preventing infection
Asthma
Description, Predisposing factors/causes, Pathophysiology (lol good luck), S/S, Dx, Tx
Description: chronic inflammatory disorder of the bronchial mucosa causing bronchial hyperresponsiveness, airway constriciton, REVERSIBLE variations in airflow obstruction
Prevalence: all ages
Prediposing factors/causes: familial disorder (genetic component)
- other risk factors: age of onset of disease, levels of allergen exposure, urban residence, exposure to indoor and outdoor air pollution, tobacco smoke, recurrent respiratory tract viral infections, GERD, obesity
- high level of exposure to allergens during childhood increases risk for asthma but also decreased exposure to certain infectious organisms creates an immunological imbalance favouring development of allergies and asthma (hygiene hypothesis)
Pathophysiology: it’s all really about air going in but cannot be pushed out due to swelling so we really need to use accessory muscles to push out leading to wheezes
- airway exposure to antigen intiates innate and adaptive immune response in sensitized ppl
- bronchial mucosa gets inflamed, airways are hyperresponsive (thanks to our lymphocyte and leukocyte friends)
- there is an immediate (early) and late (delayed) response
- early asthmatic response: APCs present antigen to T-helper cells → differerentiate into Th2 cells releasing inflammatory cytokines and ILs that activate B lymphocytes and eosinophils →IgE made! & bind to mast cells → more stuff released from mast cell (inflammatory mediators like histamine, bradykinin, PAF, prostglandins) → vasodilation, increased capillary permeability, mucosal edema, bronchospasm, mucus secretion → airways narrowed and airflow obstructed
-
late response: 4-8 hours after early response; eosinophils, neutrophils and lymphocytes cause a latent release of inflammatory mediators again causing bronchospasm, edema, and mucus secretion
- leukotrienes cause prolonged smooth muscle contraction
- eosinophils cause direct tissue injury with fibroblast proliferation and airway scarring
- impaired mucociliary function + mucus accumulation and cell debris forming plugs in the airway
- untreated inflammation can lead to LT damage (irreverisble) - i.e. airway remodeling
- airway obstruction increases resistance to airflow, decreases flow rates (esp expiratory flow) → leads to air trapping, hyperinflation distal to obstructions and increased WOB
- airflow isn’t distributed evenly in the lungs due to varying resistance and continued air trapping increases intrapleural and alveolar gas pressures, causes decreased perfusion of alveoli (so your V/Q is shit and all over the place in different parts of the lung)
- lung receptors notice increased lung volume and obstruction, so it triggers hyperventilation (this results in early hypoxemia without CO2 retention) → hypoxemia further increases hyperventilation through stimulation of resp center (PacO2 decreases, H increases = resp alkalosis)
- too much air trapping eventually leads to lungs/thorax being hyperexpanded, resp muscles are now also very stretched (so decreased tidal volume with increasing CO2 retension and resp acidosis) = resp failure
Clinical Manifestations: asymptomatic between attacks w/ normal pulmonary function tests
- During an attack: starts with chest constriction, expiratory wheezing, dyspnea, nonproductive coughing, prolonged expiration, tachycardia, and tachypnea
- severe attacks: accessory muscle use, wheezing hear on inspiration and expiration
- pulsus paradoxus (decrease in SBP during inspiration of more than 10mmHg)
- hypoxemia with associated resp alkalosis
- status asthmaticus (if bronchospasm not reversed and becomes severe) - hypoxemia worsens, expiratory flows and volumes decrease further and ventilation decreases (acidosis develops) - life threatening
- silent chest (no audible air mvoement ) and PaCO2 >70mmHg = you’re fucking dead soon so you better get epi because ventolin isn’t going anywhere
Dx: peak flor measurements, ABG, history of allergies and recurrent episodes of wheezing, dyspnea, cough or exercise intolerance; spirometry
- during acute attacks: assess for triggers, hypoxemia and resp alkalosis that may turn into hypercapnia with resp acidosis = ventilate
Treatment: oxygen, inhaled beta-agonist bronchodilators; oral corticosteroids (epi)
- Management of asthma: avoid triggers, use of peak flow meter, short-acting beta-agonist inhalers, anti-inflammatory meds and inhaled corticosteroids
- if corticosteroids don’t work, luekotriene antagonists
- if more severe, long acting beta agonists to control persistent bronchospasm
- be mindful when bagging these patients, you might push a lot of air in that won’t come out leading to potential damage and pneumos
Conditions for salbutamol and epinephrine as per Bronchoconstriction medical directive?
Contraindications for use of either of these drugs?
What is salbutamol and what are the doses and routes for giving salbutamol to a patient as per the Bronchoconstriction Medical Directive?
Bronchodilator - opens up airways
What is epinephrine and what are the doses and routes for giving epi to a patient as per the Bronchoconstriction Medical Directive?
Epinephrine is a chemical that narrows blood vessels and opens airways in the lungs. These effects can reverse severe low BP wheezing, severe skin itching, hives, and other symptoms of an allergic reaction
Chronic Bronchitis
Description, Pathophysiology, S/S, Diagnosis, Treatment
Description: hypersecretion of mucus and chronic productive cough for at least 3 months of the year (usually winter) for at least 2 consecutive years
Pathophysiology:
- inspired irritants result in airway inflammation with neutrophils, macrophages, and lymphocytes into the bronchial wall
- inflammation leads to bronchial edema, more and bigger mucous glands and goblet cells in airway epithelium, smooth muscle hypertrophy with fibrosis, and airway narrowing
- thick and strong ass mucus produced and can’t be cleared due to impaired ciliary function
- lung defences become less effective = high risk of pulm infection and injury (bacteria collecting here)
- leads to airway osbtruction (hypertrophied smooth muscle constricts especially on expiration), air trapping (airways collapse early in expiration; expands thorax and resp muscles stretched so mechanical disadvantage), loss of SA for gas exchange, frequent exacerbations (infections, bronchospasms) → leads to cough, dyspnea, decreased tidal volume, hypoxemia, hypercapnia, cor pulmonale
- obstruction causes V/Q mismatch with hypoxemia
- process starts with affecting larger bronchi and then eventually all airways
S/S: productive cough, dyspnea (late), intermittent wheezing, occasional barrel chest, always prolonged expiration, cyanosis, chronic hypoventilation, polycythemia, cor pulmonale (RHF); history of smoking
- also note these people don’t use their PaCO2 to stimulate breathing changes cause it’s chronically elevated
- note that chronic bronchitis and emphysema are collectively called COPD so some of the stuff here may also overlap with emphysema
Diagnosis: history of symptoms, physical exam, chest imaging, pulmonary function tests (FEV1 /FVC ratio <0.7), blood gas analysis
Treatment: stop smoking to prevent further disease progression
- bronchodilators, mucolytics (expectorants), antioxidants, anti-inflammatory drugs ⇒ controls cough and reduces dyspnea
- chest physicala therapy (deep breathing, postural draining)
- during acute exacerbations (infection and bronchospasm): antibiotics, steroids, potentially mech. ventilation
- last resort: chronic use of oral steroids
- home oxygen therapy (those with severe hypoxemia)
Pneumonia
Description, Types, Incidence, Risk Factors, Modes of Infection, Pathophysiology, S/S, Dx, Tx
Description: infection of the lower resp tract caused by bacteria, viruses, fungi, protozoa, or parasites
- the 6th leading cause of death in US
- categorized as: community-acquired (CAP), health care-associated (HCAP), hospital-acquired (HAP), or ventilator-associated VAP
Types:
- HCAP: occuring in those with recent hospitalizations, living in nursing home or extended care facility, home infusion therapy, chronic dialysis, or home wound care
- HAP: 2nd most common nosocomial infection (hospital acquired) but has GREATEST mortality
-
VAP: nosocominal infection occurring in 9-27% of individuals who require intubation and mechanical ventilation - most common is influenza and resp syncytial virus (RSV)
- bacterial colonization of oropharynx occurs after ET tube palaced with subsequent aspiration and pooling of bacteria near ET tube cuff (and then create a biofilm) - this can be reduced with raising head of bed, improval oral hygiene, suctioning
-
CAP: one of the most common reasons for hospitalizations - most common microorganism (Streptococcus pnumoniae)
The causative microorganism influences the clinical presentation of the individual, the treatment plan and the prognosis.
Incidence/Prevalence: highest in elderly
Risk Factors: advanved age, compromised immunity, underlying lung disease, alcoholism, altered consciousness, impaired swallowing, smoking, endotracheal intubation, malnutrition, immobilization, underlying cardiac or liver disease, and living at nursing home
Modes of infection: aspiration of oropharyngeal secretions - the most common route of lower RTI
- inhalation of microorganisms that have been released into the air when an infected individual coughs, sneezes, talks; or from aerosolized water
- ET tubes become colonized with bacteria that form biofilms (protected colonies of bacteria that are are resistant to host defences and antibiotics)
- infection anywhere in the body or from IV drug use (can lead to bacteremia that causes bacteria from the blood to spread to the lung)
Pathophysiology: in healthy lungs, pathogens that get to the lung normally just get expelled/controlled
- ptahogens recognized by alveolar macrophages stimulate T & B cells causing widspread inflammation in the lung and recruitment of typical immunity cells
- resulting inflammatory mediators and immune complexes can damaged bronchial mucous membranes and alveolocapillary membrane, resulting in acini and terminal bronchials to fill with infectious debris and excudate
- some pathogens cause release toxins that further damage lungs and consolidation of lung tissue (mucus filled)
- the accumulation of exudate in the acinus leads to dyspnea and to V/Q mismatch and hypoxemia
- Most common and lethal cause of outpatient and inpatient pneumonias: pneumococcus ⇒ can infect the lungs through inhalation of aerosolized bacteria or more commonly by aspiration or colonized oropharyngeal secretions (these bacteria have capsules that makes phagocytosis hard and release toxins)
- Viral pneumonia: seasonal, usually self limiting CAP ⇒ destroys ciliated epithelial cells (which usually expel pathogens) and invade goblet cells and bronchial mucous glands; bronchial walls become edematous and infiltrated with leukocytes
Clinical Manifestations: most cases preceded by viral UTRI
- fever, chills, productive or dry cough, malaise, pleural pain, dyspnea and hemoptysis
- pulmonary consolidation (on physical exam) demonstrated by dull percussion, inspiratory crackles, increased tactile fremitus (palpable chest vibrations when someone speaks), egophony (prolonged “a” heard on auscultation over consolidated lung tissue when person says “e”), whispered pectoriloquy (also on auscultation)
- potential S/S of underlying systemic disease or sepsis
Diagnosis: hx taking and physical exam (tachypnea, tachycardia, cracks, bronchial breath sounds, pleural effusion findings); WBC count (elevated); oxygenation and pH, chest X-rays (show infiltrates in the lungs), stains and cultures of resp tract secretions, and blood cultures
Treatment: prevention - avoidance of aspiration, resp isolation of immunocompromised people, vaccination
-
management: establishing adequate ventilaion and oxygenation
- adequate hydration and good pulmonary hygiene (e.g. deep breathing, coughing, chest physical therapy)
- antibiotics given within 4 h to treat bacterial pneumonia
- viral pneumonia: treated with supportive therapy alone (potentially antivirals if severe)
Pulmonary Artery Hypertension (PAH)
Description: as defined as a mean pulmonary artery pressure (MPAP) >25mmHg at rest (normal is 15-18mmHg)
Classifications:
- 1) No known cause OR associated with inheritance, drugs or toxin, connective tissue disease or infection
- 2) PAH attributable to left heart disease
- 3) PAH caused by chronic lung disease or hypoxia, or both
- 4) Chronic thromboembolic PAH
- 5) PAH caused by other multifactorial mechanisms including blood, metabolic, and systemic factors
Causes: COPD (most common lung disease associated with PAH); interstitial fibrosis; but any condition causing chronic hypoxemia can lead to PAH
Pathophysiology:
- Idiopathic pulmonary arterial hypertension (IPAH) aka the 5th category (above) is characterized by endothelial dysfunction with overproduction of vasoconstrictors (eg. thromboxane, endothelin) and decreased production of vasodilators (NO, prostacyclin)
- vascular growth factors released ⇒ fibrosis and thickening of vessel walls (remodeling) with luminal narrowing and abnormal vasoconstriction
- leads to resistant to pulmonary artery blood flow = pressure increases here + in RV
- Gas exchange reduced with restriction in lung volumes
- As resistance and pressure ↑, RV has to work harder = RV hypertrophy (cor pulmonale) followed by right HF
- Category 3: PAH associated with lung resp disease or hypoxia is serious complication of conditions like COPD, hypoventilation with obesity (these also have hypoxic pulmonary vasoconstriction that further increase pulm artery pressure)
Clinical Manifestations: may not be detected until quite severe
- Sx masked by other forms of pulm or CV disease
- first indication: abnormality seen in chest radiography (enlarged R heart border) or ECG showing RVH
- Fatigue, chest discomfort, tachypnea, dyspnea (particularly with exercise)
- peripheral edema, JVD, precordial heave, accentuation of pulmonary component of the 2nd heart sound
Diagnosis: Right heart catheterization
- to determine cause: chest x-ray, ECHO, CT
- IPAH dx made when all other causes ruled out
Treatment: oxygen, diuretics, anticoagulants, avoiding contributing factors (air travel, decongestant meds, NSAIDs, pregnancy, tobacco use)
- Meds (not curative): prostacyclin, endothelin antagonists, PDE-5 inhibitors, guanylate cyclas activator
- lung transplant (if no remission)
- most effective tx for PAH associated with lung resp disease/hypoxia or both: treatment of primary disorder (and supp oxygen to reverse hypoxic vasoconstriction)
Laryngeal Cancer
Description: cancer of the larynx
Prevalence/Risk Factors: <1% cancers in US; primary risk factor is tobacco smoking which is further heightened with smoking x alcohol consumption combo
- HPV (6 and 11) also linked to both benign and malignant laryngeal disease
- highest incidence: men 50-75 y.o.
Pathophysiology:
- carcinoma of true vocal cords (glottis) more common than of supraglottic structures (epiglottis, aryepiglottic folds, arytenoids, false cords)
- tumors of subglottic area rare
- squamous cell carcinoa the most common cell type
- metastasis develops by spreading to draining lymph nodes; distant metastasis is rare
Clinical Manifestations:
- hoarseness (that can lead to voice loss if progress), dyspnea (rare with supraglottic tumors but can be severe in subglottic), cough (may following swallowing)
- laryngeal pain with supraglottic lesions
Diagnosis: external inspection and palpation of larynx and lymph nodes of neck; indirect laryngoscopy (imaging procedures) & biopsy;
Treatment: combined chemo and radiation or surgical resection
- swallowing and speech difficulties may occur aftter tx (sequelae) - swallowing and speech therapy
- extensive lesions need total laryngectomy
Croup
Description: an acute laryngotracheitis, almost always occurs in children between 6 months and 5 years (peak incidence at 2 y.o.)
Causes/Incidence: 85% cases (virus - most common parainfluenza; others: RSV, rhinvirus, adenovirus, rubella virus, or atypical bacteria)
- higher in males, most common in winter months
- ~15% of cases have strong family hx of croup
-
spasmodic croup - usually in older children (unknown etiology but can be triggered by cold, allergy, or viral infection)
- develops acutely usually without fever and tends to recur
Pathophysiology: caused primarily by subglottic inflammation and edema from infection
- the subglottic space is loos so allows for accumulation of mucosal and submucosal edema (vs in larynx, the mucous membranes are tightly adhered to cartilage so not as much space to swell)
- cricoid cartilage also the structurally narrowest point of the airway which makes edema in this area critical
- spasmodic croup also causes bronchoconstriction but with less inflammation and edema
- summary: inflammation and edema ⇒ upper airway obstruction ⇒ increased airflow resistance ⇒ increased WOB ⇒ generates more negative intrathoracic pressure that may exacerbate collapse of upper airway ⇒ resp failure
Clinical Manifestations: rhinorrhea, sore throat, low grade fever for a few days, then develops harsh (seal-like) barking cough, inspiratory stridor, hoarse voice
- quality of voice, cough, and stridor may tell you the location of the obstruction:
- snoring: enlarged tonsils or adenoids
- inspiratory stridor: airway compromised at level of supraglottic larynx, vocal cords, subglottic region, upper trachea
- Expiratory stridor: narrowing or collapse in trachea or bronchi
- noise during both inspiration and expiration: fixed obstruction of vocal cords or subglottic space
- Hoarseness/weak cry: obstruction at vocal crods
- croupy cough: constriction below vocal cords
- most resolve spontaneously in 24-48 hours, do not want hospital admission
- severe croup may show deep retractions, stridor, agitation, tachycardia, maybe pallor/cyanosis
- spasmodic croup: hoarseness, barking cough, stridor; sudden onset, usually at night and without prodromal symptoms; resolves quickly
Diagnosis: Westley croup score (for severity)
Treatment: Degree of symptoms determines level of treatment
- most do not need tx (mild stridor cases may need outpatient tx)
- glucocorticoids (injection, oral dexamethasone, or nebulized budesonide)
- for acute resp distress: nebulized epinephrine which stimulates α-and β-adrenergic receptors and decreases mucosal edema and airway secretions (opens up the airway, reduces inflammation)
- oxygen (or heliox- helium/oxygen mix for severe cases)
Conditions and Contraindications for use of epinephrine for croup, as per Croup Medical Directive?
Treatment of croup as per Croup Medical Directive in ALS PCS?
Consider age, weight, route, concentration
Respiratory Distress Syndrome (RDS) of the Newborn
Description: previously known as hyaline membrane disorder (HMD); aka surfactant deficiency disorder (SDD) - a significant cause of neonatal morbidity and mortality characterized by poor lung structure and lack of adequate surfactant
- Vermont Oxford Neonatal Network definition: PaO2 <50mmHg on room air, central cyanosis in room air, need for supplemental oxygen to maintain PaO2 >50mmHg, and classic chest film appearance
Prevalence: almost exclusively in premature infants, and incidence has increased in US over the past 2 decades; occurs in 50-60% of infants born at 29 weeks gestation and decreases significantly by 36 weeks
- death rates have declined since intro of atenatal steroid therapy and postnatal surfactant therapy
Risk factors: premature birth/low birth weight; male gender; c-section without labour; diabetic mother; perinatal asphyxia
Pathophysiology: caused by surfactant deficiency which decreases alveolar SA available for gas exchange (without surfactant, the alveoli collapse at the end of each exhalation)
- surfactant is normally not secreted by alveolar cells until ~30 weeks gestation (newer textbook says 20-24)
- preemies are also born with underdeveloped and small alveoli that are difficult to inflate and have thick walls and inadequate capillary blood supply = gas exchange ++impaired
- their chest walls are also weak and highly compliance so the rib cage tends to collapse inward with respiratory effort
- net effect: atelectasis resulting in significant hypoxemia = metabolic acidosis
- atelectasis requires ++ negative inspiratory pressure to open alveoli with each breath ⇒ increased WOB ⇒ hypercapnia ⇒ hypoxemia + hypercapnia cause pulmonary vasoconstriction ⇒ increased intrapulmonary resistance and shunting ⇒ hypoperfusion of the lung & decrease in effective pulmonary blood flow
- increased pulm vascular resistance may even cause partial return to fetal circulation with right to left shunting through ductus arteriosus and foramen ovale
- increased pulmonary capillary permeability + need for mechanical ventilation (which damages alveolar epithelium) both result in leakage of plasma proteins into alveoli air spaces (creating appearance of hyaline membranes which looks glassy/transparent) and this causes further inactivation of surfactant
Signs and Symptoms: appears within minutes of birth → tachypnea (RR >60 /min), expiratory grunting, intercostal and subcostal retractions, nasal flaring, cyanosis
- severity increases over first 2 days of life (newer textbook says first hours of life)
- apnea, irregular respirations when baby tires
- chest radiograph shows diffuse granular densities within first 6 hours of life (“ground glass” appearance associated with alveolar flooding)
- clinical manifestations reach a peak within 3 days after which there is gradual improvement
Diagnosis: basis of premature birth or other risk factors, chest radiographs, pulse ox readings, analysis of amniotic fluid or tracheal aspirates to measure lung maturity
Treatment: prevention of premature birth (the ultimate treatment for RDS)
- for those at risk for preterm birth: antenatal tx with glucocorticoids to induce significant and rapid acceleration of lung maturation and stimulation of surfactant production in fetus
- For babies <1000g: administration of synthetic or natural surfactant through nebulizer or nasal CPAP ventilation (start 15-30min after birth)
- Supportive care: oxygen, mechanical ventilation (but before of harm this could cause)
- most infants survive RDS and most recovery within 10-14 days (however may have subsequent bronchopulmonary dysplasia)
Cystic Fibrosis (CF)
description, prevalance, pathophysiology, clinical manifestations, Dx, Treatment
Description: autosomal recessive inherited disease that results from defective epithelial chloride ion transport
- CF gene located on chromosome 7 and mutations divided into 6 classes with varying severity
- Classes 1-3: more severe disease
- Classes 4-6: milder pulmonary disease and pancreatic insufficiency
Prevalence: primarily whites; median age of dx is 6 y.o.; mean age of survival ~40s; high carrier frequency
Pathophysiology: multiorgan disease affecting the lungs, GI tract, and reproductive organs
- abnnormal expression of the cystic fibrosis transmembrane conductance regulator (CFTCR) protein which is an activated chloride channel present on surface of many types of epithelial cells
- most important effects are on the lungs and likely cause of death would be from resp failure
- mucus plugging, chronic inflammation, chronic infection of the small airways
- mucus plugging - due to increased production (more goblet cells and glands and bigger) and altered properties of mucus (dehydrated and viscous due to defective chloride secretion and excess sodium absoprtion)
- periciliary fluid also deplete causing cilia to not be able to move = mucus adheres to the epithelium and bacteria and other WBC byproducts accumulate
- lots of neutrophils in the airways releasing oxidants and proteases that damage lung structural proteins = all causing inflammation
- CF airway microenvironment favours bacterial colonization (Staphylococcus aureus, Haemophilus influenzae common in younger children; Pseudomonas aeruginosa in at least 75% of children with CF) ⇒ their biofilm allows for rapid mutation and antibiotic resistant
- chronic inflammation leads to microabscess formation, bronchiectasis, patch consolidation, pneumonia, peribronchial fibrosis, cyst formation; may also have pneumothorax and hemoptysis
- vasculature gets remodelled due to localized chronic hypoxia and arteriolar vasoconstriction
- pulmonary HTN and cor pulmonale may develop in late stages of disease
Clinical Manifestations: respiratory or GI symptoms
- Resp: persistent cough or wheeze, excessive sputum production, recurrent or severe pneumonia
- over time: barrel chest and digital clubbing
- chronic sinusitis, nasal polyps
Diagnosis: immunoreactive trypsinogen (IRT) blood screening, sweat test (reveals [Cl-] > 60 mEq/L), genotyping for mutations; sibling with CF taken into account
Treatment: primarily focused on pulmonary health and nutrition
- promoting mucus clearance (via chest physical therapy, bronchodilators, aerosolized dornase alfa enzyme and hypertonic saline to liquefy mucus)
- oral, inhaled, or IV antibiotics - treat exacerbations of pulmonary infection and with antibiotic resistance
- recombinant human growth hormone - improves lung function, height, and weight
- lung transplantation (if end stage)
