Class notes
Pathophysiology
- Course
- Institution
Notes for all lecture content including pathophysiology of the following systems: -Respiratory -Cardiovascular -Gastrointestinal -Endocrine -Neurology
[Show more]
Seller
Follow
saramohamed2
Content preview
Respiratory -Lecture 1 (Pulmonary refresher)Wednesday, January 8, 2020 1:42 PM
⚫ PURPOSE OF THE RESPIRATORY SYSTEM
○ Deliver oxygen to tissues
○ Remove carbon dioxide waste from tissues
○ Acid/base buffering
▪ Respiratory
▪ Metabolic
⚫ 4 FUNCTIONAL COMPONENTS OF THE RESPIRATORY SYSTEM
1. Mechanics
○ Movement of gas into the lung
▪ Lung mechanics (pulmonary)
▪ Chest wall mechanics
- Respiratory muscles contained in the thorax, neck, abdomen, etc.
○ Flow (convective) depends on pressure and resistance
▪ Convective ; occurs primarily in large upper airways where bulk movement of gases move from a generally high pressure area to low
pressure area
- Occurs quickly, high velocity
▪ Diffusive ; individual gas molecules move within individual partial pressure gradients
- Lower velocity
- Driving force for gas exchange in alveoli
○ Major and complex contributor to lung disease
2. Gas Exchange
○ Diffusive flow of gas: air <--> blood
○ O2 and CO2 transport (hemoglobin)
○ Ventilation/perfusion matching (a primary cause of poor O2 delivery in disease)
▪ Different amount of air going into lungs based on various factors (example; gravity, posture)
▪ Mismatch between ventilation going to one place and perfusion of blood flow going to another place in respiratory disease
3. Control of Breathing
○ Effectors- neurons to muscles
○ Sensors - neurons to CNS
▪ Give us information about mechanical movement of the lung as well as the chemical environment
▪ Mechano : lung, upper airways, chest wall
▪ Chemo : O2 and CO2 (central and peripheral)
○ Often deregulated in respiratory disease
4. Acid Base Balance
○ Balance blood and tissue pH to optimize cell function
○ Henderson-Hasselbalch:
pH=pKa + log
○ Respiratory vs metabolic regulation
⚫ STRUCTURE/FUNCTION
○ Gas transport: Airways
○ Bulk airflow
○ High velocity
○ Very few in number, but large diameter airways
○ Gas Exchange: Alveoli
○ Transfer of gases from air to blood
○ Slow velocity
○ Diffusive flow
○ Large number, small diameter
PHGY350 Page 1
, ○
⚫ DESCRIBING BREATHING
○ Tidal volume (VT)- volume of each breath (L; ~10ml/kg)
○ Frequency of breathing (f)
○ Minute ventilation (VE) = VT x f = L/min
▪ Further broken down into
VE= (VT/Ti) x (Ti / Ttot) (won't use this)
respiratory drive x duty cycle
- Respiratory drive- how badly you want to breathe in
- Duty cycle- how much of respiratory phase is dedicated to breathing in
⚫ ANATOMY AND IMPACT ON BREATHING : CONDUCTING ZONE & RESPIRATORY ZONE
Trachea to terminal bronchioles
No gas exchange -thick walled airways
Gas transport by "bulk flow"
Location of anatomic dead space (VD) (150mL)
Respiratory bronchioles and alveoli
Gas transport by diffusion …
- Including gas exchange at alveolar-capillary membrane
Large surface and cross-sectional areas
Site of alveolar ventilation (VA)
Not all air can be accessed for gas exchange
⚫ IMPACT OF ANATOMIC DEAD SPACE
○ PO2 = 150 mmHg
○ PCO2= 0 (fresh air)
Gas left in conducting
airways is unchanged Conducting area (trachea)
Gas in alveolar spaces
exchanges with
pulmonary capillary
blood
↓PO2 , ↑PCO2
A first-ever breath out Gas exchange
Entire lung filled with used gas
PHGY350 Page 2
, Entire lung filled with used gas
○ All gases in lung and conducting airways are like alveolar gas
○ What happens when we take a second breath in (usual breathing) ?
Impact of VD on alveolar ventilation
○ The next breaths are a mixture of fresh gas and "re-breathed" gas (previously contained in the alveolus and taken from the anatomic dead space)
Fresh
"Re-breathed"
Therefore…
○ Alveolar ventilation; amount of the gas that enters the alveoli that is 'fresh"
○ Total gas entering the lung (minute ventilation; VE)
= alveolar ventilation + dead space ventilation
○ Dead space (VD) = volume of conducting zone
○ Alveolar volume (VA) = volume of respiratory zone (reaches alveoli)
⚫ CONSEQUENCES OF RAPID SHALLOW BREATHING
○ VD is constant, however VE is achieved
○ Thus, rapid, shallow breathing impairs ventilation
▪ Minute ventilation is the same
▪ Breathing heavily doesn’t mean breathing effectively
⚫ IMPACT OF VD WHEN EVALUATING SUBDIVISIONS OF LUNG VOLUME/ LUNG FUNCTION TESTING
PHGY350 Page 3
, End-inspiratory lung volume
VOLUME OF
AIR BEING
BREATHED
End-expiratory lung volume
(anything involving RV)
➢ Total lung capacity
▪ Total amount air lungs can possibly hold
➢ Vital capacity
▪ Amount of air you can voluntarily move
▪ Breathe out as far as you possibly can and then breathe in as much as you possible can, total dynamic range you have access t o= vital capaci
▪ Used when diagnosing respiratory disease
➢ Functional residual capacity
▪ Equilibrium point
▪ Natural point lungs will come to
▪ Least energetic point
➢ Residual volume
▪ Air left in lungs
▪ Prevents airways from collapsing
➢ End expiratory volume
▪ Point you start to breath in
➢ End-inspiratory volume
▪ Point you start to breathe out
Q: You are helping a COPD patient learn the use of oxygen therapy, which in this case relies on a tank of 40% oxygen at sea l evel (barometric pressure =
760mmHg).
a) What is the PO2 in the dry air?
PO2 = (FiO2)(PB) = 0.4 (760) = 304mmHg
Fi= fractional concentration
PB= barometric pressure
b) What is the PiO2 in the inspired air the patient is breathing?
when you bring air into the body, it enters a warm, humid environment, thus need to consider partial pressure of water
PiO2 = (0.4)(760-47)= 285.2mmHg
(FiO2)(PB - P H2O)
47mmHg for pressure of water vapor in airways
Q: During a trip from T.O to Sydney, Australia you review gas laws as applied to the aircraft environment (barometric pressur e = 565mmHg)
a) What is the fractional concentration of oxygen?
Stays the same - FiO2= 0.2093 (~21%)
b) What is the PiO2 (in the inspired air) you are breathing?
PiO2 = (FiO2)(PB - P H2O)
= (0.2093)(565-47)
=108.4mmHg
-lower at higher altitudes / lower barometric pressures
PHGY350 Page 4
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller saramohamed2. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $7.69. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
78252 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now