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
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
