Mechanics of Breathing Flashcards
What is respiration simply put?
the exchange of gases between the atmosphere, blood, and body
What are the 3 main steps of respiration?
Pulmonary ventilation
External respiration
Internal Respiration
Simply explain pulmonary ventilation
“Breathing”
inhalation and exhalation of air with exchange of air between the atmosphere and the air spaces of the lungs
Simply explain external respiration
Pulmonary (lung and blood)
exchange of gases between the lung spaces and blood in the pulmonary capillaries across the respiratory membrane
blood gains O2 and loses CO2
Simply explain internal respiration
Tissue (blood–>tissues)
exchange of gases between capillary blood (cellular aerobic respiration)
The closed compartment housing the lungs and heart bound at the neck by muscles and connective tissue
Thorax … aka the chest
the dome-shaped sheet of skeletal muscle that separates the thorax from the abdomen
Diaphragm
What is the thoracic wall formed by?
the spinal column, ribs, sternum, and intercostal muscles
Each lung is surrounded by a closed sac called
pleural sac
the pleural surface coating the lung is called
visceral pleura
the outer layer of the pleural cavity that lines the interior thoracic wall and diaphragm is
parietal pleura
the two layers of pleura are separated by
intrapleural fluid
what is the purpose of intrapleural fluid
lubricates the pleural surfaces so they can slide past eachother without being separated easily. This prevents friction with breathing.
think of two glass slides with water in between
What are the primary muscles used to accomplish breathing
diaphragm and external intercostals
What are the big 4 accessory muscles used to accomplish breathing
internal intercostals
abdominal (rectus abdominis, obliques)
SCM
Scaleness (anterior, middle, posterior)
What are the other accessory muscles used for breathing
pectoralis (major, minor)
latissimus dorsi
serratus anterior
Movement of the diaphragm accounts for __% of change in intrathoracic volume during quiet inspiration
75%
where is the diaphragm attached? and what does it arch over?
around the bottom of the thoracic cage
liver
The diaphragm moves _________ like a piston when it contracts
downward
which muscle of inspiration runs obliquely downward and forward from rib to rib?
External intercostal muscles
What do external intercostal muscles do whenn they contract in inspiration?
elevate lower ribs when they contract
this pushes the sternum outward
and increases AP diameter of the chest
Where do the phrenic nerves innervating the diaphragm arise from?
cervical segments 3-5
Do you need both the diaphragm and the external intercostals to maintain adequate ventilation at rest
No, you can ventilate with only one, but you do best with both.
Which accessory inspiratory muscles help elevate the thoracic cage during deep labored breathing (exercising)
Scalene and SCM
Which muscles of expiration pass obliquely downward and posteriorly from rib to rib, pulling the ribcage downward when they contract?
Internal intercostals
What does the contraction of internal intercostals and pulling of the ribcage downward result in?
decrease intrathoracic volume and forced expiration
Which abdominal muscles aid in expiration by pulling the ribcage downward and inward?
rectus abdominus
internal and external obliques
Contraction of the abdominal muscles ________ intrabdominal pressure which pushes the diaphragm ________
increases
upward
Are any muscles required for expiration?
No, expiration is passive unless it is forced expiration which is when you see the use of these muscles
_______ and ________ constistute one respiratory cycle
an inspiration and expiration
What is the flow of air between the atmosphere and the lungs driven by?
presence of a pressure difference
Air moves into the lungs when the pressure inside the lungs is _____ than that of the atmosphere, which is _________
less
inspiration
Air leaves the lungs when the pressure inside the lungs is ________ than that of the atmosphere, which is ________
greater
expiration
During inspiration, the lungs must expand which ______ lung volume and _________ lung pressure to lower than atmospheric pressure
increases lung volume
decreases lung pressure
Inspiration _______ the alveoli and causes ______ of the principal muscles (diaphragm and external intercostals) and with deep inspiration, accessory muscles
expands the alveoli and causes contraction
___________ is dependent of elastic fiber recoil and inwards pull of surface tension due to alveoli fluid
expiration
When does expiration begin
when the muscles of inhalation relaxes
During expiration, lung volume __________ and alveolar pressure ___________ to higher than that of atmospheric pressure, which causes the air to flow outward
lung volume decreases
and alveoli pressure increases
What happens with labored breathing?
abdominal and internal intercostal muscles contract which moves the inferior ribs downward, contracts the abdominal viscera and forces the diaphragm up (superiorly)
Contraction of inspiratory muscles increases intrathoracic volume. What does this mean?
pressure in the airway becomes negative and air flows down INTO lungs
The lung recoil pulls chest back into expiratory position and pressures balance out. What does this mean
Pressure in the airway becomes positive and air flows OUT of the lungs
Lung capacities contain 2 or more ________
volumes
Where are volumes and capacities recorded on
diagnostic spirometry
What is diagnostic spirometry used to assess
a patients lung function in comparison with normal population
or
comparing measurements from the same patient throughout therapy
The amount of air that moves into the lungs with each inspiration during quiet breathing (normal breathing)
or the amount that moves out with expiration
Tidal volume (TV)
Normal value of TV
500-700 mL of air
the air inspired with MAXIML inspiratory effort in excess of the tidal volume
“breathe in as long and as deeply as you can”
Inspiratory reserve volume (IRV)
Normal value you IRV
2L of air
The volume of air expelled by an ACTIVE expiratory effort AFTER PASSIVE EXPIRATION
Expiratory reserve volume (ERV)
The air left in lungs after MAXIMAL expiratory effort
Residual Volume (RV)
Normal value of RV
1.3 L of air
Total lung capacity comprises all components of Volume. What is the equation?
TLC = TV + IRV + ERV + RV
What is the normal value for TLC
5L of air
this capacity refers to the maximum amount of air expired from the fully inflated lungs or maxium inspiratory level
Vital Capacity (VC)
What is the equation for VC and what is the normal value for VC?
VC=TV+IRV+ERV
3.5L of air
This capacity refers to the maximum amount of air inspired from the end-expiratory level
Inspiratory Capacity (IC)
What is the equation for IC
IC = TV + IRV
this capacity represents the volume of the air remaining in the lungs after each expiration of a NORMAL breath
Functional Residual Capacity (FRC)
What is the equation for FRC
FRC = RV + ERV
This capacity is the LARGEST amount of air that can be expired after MAXIMAL INSPIRATORY EFFORT
Forced Vital Capacity (FVC)
What is FVC an index of and what does it measure
index of pulmonary function and measures strength of respiratory muscles
the friction of Vital Capacity expired during the FIRST SECOND
Forced Expiratory Volume in the First Second (FEV1)
What is the FEV1/FVC ratio useful for classifying
classes of airway disease (ie lung disease)
When is FVC reduced?
obstructive and restrictive pulmonary disease
What is important for determining between obstructive and restrictive?
In obstructive (1.0), FEV1 is reduced way more than in restrictive (1.8)… making the % FEV1/FVC ratio more reduced in obstructive (50%) than restrictive (90%)
In restrictive the FEV1/FVC ratio is often higher than that of a normal individual.
What does FEV1, FVC, and FEV1/FVC in a healthy individual
FEV1 : 3.3
FVC : 4.0
FEV1/FVC : ~ 80%
Which lung disease is marked by a decrease in both FVC and FEV1/FVC ratio (<80%)
Obstructive lung disease
What are some examples of obstructive lung disease?
ASTHMA
airway obstruction
airway inflammation
airway hyper-responsiveness to many stimuli
Which lung disease is marked by a decrease in FVC but WITHOUT a decrease in FEV1/FVC ratio (>80%)
Restrictive Lung Disease
What are some examples of restrictive lung disease?
Pulmonary fibrosis
irreversible interstitial lung disease (respiratory failure and pulmonary hypertension)
What are the FEV1/FVC ratios for normal, obstructive, and restrictive?
normal 80%
obstructive <75%
restrictive >80%
What term represents the mechanical properties of the lungs that allows them to recoil and return to their original shape following expansion
Lung Elasticity
What term describes the total compliance of both lungs, measuring the extent to which the lungs will expand (change in volume of lungs) for each unit increase in the transpulmonary pressure?
Lung compliance
Which term describes the difference in pressure between the inside and outside of the lung?
Transpulmonary pressure
if you have a decrease in compliance what does that look like? what about an increase?
Decrease: stiff difficult to expand
Increase: can stretch and expand
Low lung compliance = an increase or decrease in transpulmonary pressure?
increase
Lung compliance is correlated with __________
Lung elasticity is correlated with _________
compliance = inspiration (Stretch)
elasticity = expiration (recoil)
When the pressure outside the lungs is negative, the lungs are able to expand, fill with air, and lung volume is ___________
increased
when the pressure outside the lungs is positive then the lungs will collapse and there will be a _______ in lung volume
decrease
Elasticity and compliance are _________ proportional
inversely
In chronic respiratory disease such as emphysema, what happens to elasticity and compliance?
elasticity goes down and compliance goes up
this means it is hard to push air out when exhaling
What does an increase in compliance result in in emphysema?
Increased lung compliance cause the alveoli to stay closed.
this results in decreased surfactant and increase in surface tension due to the alveoli expanding and expanding resulting in alveolar collapse.
Is compliance increased or decreased in fibrosis?
decreased
What clinical diagnosis does the following describe?
If air enters the intrapleural space, that shifts the intrapleural pressure from being negative to being EQUAL to atmospheric pressure (not good)
Pneumothorax
The shift in pressure in a pneumothorax changes the equilibrium that had existed between the lung and chest wall, causing the lungs to ________ and the chest wall to _______
lungs collapse
chest wall expands
In mallory’s words describe a pneumothrax
damage to pleura
lung collapses due to intrathoracic pressure being less than atmospheric pressure
“sucking air in, we are pushing lung tissue over”
What does a pneumothorax look like on scan?
no vasculature seen on side with pneumothorax
ONWARD TO REGULATION OF BREATHING!!!
What are the two principal areas of the respiratory center?
Medullary respiratory center
Pontine input
What are the two collections of nuclei that makes up the medullary respiratory center?
DRG (dorsal respiratory group)
VRD (ventral respiratory group)
Input and output of DRG is via…..
Does DRG gave to do with inspiration or expiration
Input –> CNIX and CNX
Output –> phrenic nerve
sends impulses to diaphragm and intercostal muscles to allow for INSPIRATION
Is VRG responsible for inspiration or expiration?
What does VRG do?
EXPIRATION
Sets BASIC rhythm of breathing
When is Pontine Input active?
both inspiration and expiration
Does the upper or lower pons smooth the transition between inspiration and expiration
Upper pons
Does the upper or lower pons transmits nerve impulses to the DRG to inhibit inspiration
Lower Pons
What are the two neural mechanisms that regulate respiration?
Voluntary control
Automatic control
Voluntary control is located in the cerebral cortex and sends impulses the respiratory motor neurons via the ____________ _____
corticospinal tracts
Autonomic control is driven by impulses from ___________ cells in the. ________
pacemaker cells in the medulla
impulses from which part of the spinal cord activate the diaphragm via phrenic nerves?
cervical
impulses from which part of the spinal cord activate the external/internal intercostals and other expiratory muscles?
thoracic
What type of innervation occurs when motor neurons to expiratory muscles are inhibited when those supplying inspiratory muscles are active (and vice versa)
Reciprocal
What are additional inputs that regulate breathing?
Chemoreceptors
hering-Bruer Reflex
What are chemoreceptors sensitive to change in?
CO2, H+, and O2
What responds to changes in CSF
Medulla
What is within the arch of the aorta and sensitive to change in the blood
Aortic Bodies
What is within walls of right and left common carotids and sensitive to change in blood
Carotid bodies
What occurs in the Hering-Breur (inflation) Reflex?
stretch receptors located in muscles of bronchi and bronchioles that stop further inhalation when overstretched
is chemical control achieved by positive or negative feedback via chemorecptors?
Negative
What are specialized cells that mediate the effects of variations in blood chemistry on respiration
Chemoreceptors
What are the 2 types of chemoreceptors involved in chemical control?
Central and Peripheral
Where are central chemoreceptors found?
Brainstem
Where are peripheral chemoreceptors found?
aortic arch and carotid bodies
What is the function of central chemoreceptors?
respond to changes in the pH of CSF (which is influenced by CO2 levels in the blood (inc in CO2 across BBB = dec in PH))
What is the function of peripheral chemoreceptors?
Respond to changes in levels of O2 and CO2 in blood
An increase in CO2 leads to a decrease in CSF which stimulates which chemoreceptor to increase respiratory rate and breathing to remove CO2 from body?
Central
When lots of CO2 crosses the BBB it is broken down into _________ which _______ pH
BICARBONATE
DECREASES CSF PH
What is located in the airway walls and lungs and are sensitive to lung volume?
Stretch receptors
Does an increase or decrease in lung volume stimulate stretch receptors?
Increase (inhalation)
When stretch receptors are stimulated by inhalation what does this cause (leads to a reflex)
this signals respiratory centers in the brainstem to decrease respiratory rate and tidal volume
this is known as hering-breuer reflex
If there is a decrease in lung volume (exhalation), activity of stretch receptors leads to what?
increase in respiratory rate and tidal volume
A decrease in lung volume reduces mechanical resistance to airflow leading to what?
air is able to flow easier in and out of the lungs.
During exercise, increased blood flow is circulated to where?
the muscles
An increase in extraction of O2 from the blood in exercising muscles leads to
increase in ventilation because we are trying to get rid of the CO2 and increase the O2 in our body.
Does ventilation increase or decrease with onset of exercise?
increase
When ventilation increases with exercise what effect does it have on gas exchange in the body?
increase in amount of O2 entering blood in the lungs and increase in pulmonary flow
this causes an increase in the amount of o2 added to each unit blood
Increase in O2 uptake is proportional to ___________, until maximum is reached
Workload
What happens after O2 uptake levels off?
lactate levels rise
Why do lactate levels rise?
because we begin using anaerobic respiration in which lactate is a byproduce of carbohydrates for energy
