Exam 4: Pulmonary Disorders Flashcards
normal value for blood gas pH
pH: 7.35-7.45
normal value for PaO2
PaO2: 80-100
normal value for PaCO2
PaCO2: 35-45
what is oxygenation
Refers to the ability to take in oxygen from the lungs and distribute it to the tissues and organs
Blood gas parameters- (to calculate total arterial oxygen content, must know)
- PaO2 less than 80 (partial pressure of O2)
- Hemoglobin concentration (amount of hgb available to bind w O2)
- Oxygen saturation SPO2 (% of available hgb that is bound to O2)
why is there a large drop in PO2 inspired air compared to PO2 in alveoli?
because of the water vapor at body temp is 47
How is oxyhemoglobin formed?
o Oxygen diffuses across the alveolar capillary membrane, it dissolves in the plasma, where it exerts pressure. As PaO2 increases oxygen in the plasma moves into the RBCs and binds with hemoglobin forming oxyhemoglobin
Binding occurs in the lungs= oxyhgb association/hgb saturation w/ O2
why is the CO2 in the tissue level increased?
at the tissue level, theres more CO2 because metabolism has occurred.
- the tissue creates CO2 and allows the CO2 in the venous blood to increase
describe bronchial vein
the venous blood does not go through the pulm system–>makes a little bypass through an internal shunt as a result there’s a small dilution that occurs.
what is hemoglobin desaturation
o Reverse process, O2 is released from hgb (this occurs in the tissues at cellular level)
describe oxyhemoglobin dissociation curve
o When hemoglobin saturations and desaturations are plotted on a graph, the result is a S-shaped curve known as, oxyhemoglobin dissociation curve.
For PaO2 <60 mmHg, oxygen is readily unloaded to peripheral tissues and hemoglobin’s affinity for oxygen molecule diminishes reflecting the steep part of the curve.
For PaO2 >60 mmHg, the curve becomes relatively flat, reflecting the maximum saturation of hemoglobin with oxygen in the lungs.
**The oxygen-hemoglobin dissociation curve shows how the hemoglobin saturation with oxygen (SO2,), is related to the partial pressure of oxygen in the blood (PO2)
The oxyhemoglobin curve is shifted to the right during
o Acidosis
o Hypercapnia
o Hyperthermia
o abnormal hemoglobin
o high levels of 2,3 DPG
Indicates decreased affinity of oxygen or increased ease with which oxyhemoglobin dissociates and oxygen moves into the cells
** decrease pH=curve shifts to right
The oxyhemoglobin curve is shifted to the left during
o Acute alkalosis
o hypocapnia (in the lungs when CO2 diffuses out of the blood into the lungs, the affinity for oxygen increases)
o hypothermia
o carboxyhemoglobin
o abnormal hemoglobin.
Indicates increased affinity for oxygen, which promotes association in the lungs and inhibits dissociation in the tissues.
- low levels 2,3 DPG
**increase pH=curve shifts to left and holds O2 more
what is the Bohr effect?
The shift in the oxyhemoglobin dissociation curve caused by changes in CO2 and hydrogen ion concentration in the blood
what is failure of ventilation
failure to get gas in/out of lungs for exchange
describe ventilation
Refers to ability to take in oxygen and remove CO2
* mechanical movement of gas or air into and out of the lungs
* known also as “Respiration”
what does ventilation depend on?
- production and elimination of carbon dioxide
- alveolar minute ventilation
o The amount of air that successfully got into the alveoli and could be removed from the body
o Calculated by-> RR x TV= minute ventilation
What can cause low ventilation?
- drug use
- low oxygen in the environment (low PIO2)
where is the respiratory center located?
- in the brainstem controls respiration from transmitting impulses to the respiratory muscles, causing them to relax and contract.
When CO2 rises, it can be detected by?
o Central chemoreceptors are in the MEDULLA and monitor arterial blood indirectly by sensing the changes in the pH of CSF.
They control rate of breathing!!!
Monitor pH, PCO2, PaO2
They sense pH low by detecting increase CO2 by detecting increase in H
* As CO2 converts to carbonic acid to enter CSF as H
If alveolar ventilation is low (i.e. COPD) PaCO2 in the arteries increases CO2 diffuses into CSF pH decreases chemoreceptors get activated and they increase the depth and rate of ventilation.
* In COPD, chemoreceptors become insensitive and kidneys have to compensate the low pH by retaining bicarb.
o Peripheral chemoreceptors are located in aortic bodies, aortic arch, and carotid bodies at the bifurcation of the carotids, near the baroreceptors.
Primarily sensitive to PaO2 and pH.
They will detect increase in CO2 and H (acidity) and lactic acid, as well as decrease PaO2 and pH
PaO2 (must drop below 60%) and pH drop cause them to be activated and ventilation is increased.
Play into effect when central receptors become insensitive d/t chronic hypoventilation.
describe lung innervation and the three types
(by the ANS) three type of lung sensory receptors, that send impulses from the lungs to the dorsal respiratory group;
o stretch receptors
sensitive to increase size or volume of the lungs -> decrease RR and volume
o irritant receptors
sensitive to aerosols, gases, dust -> initiates a COUGH REFLEX, bronchospasm, and increased RR
o pulmonary C-receptors “J-receptors”
sensitive to increased pulmonary capillary pressure, -> stimulates rapid shallow breathing, laryngeal constriction on expiration, and mucus secretion, hypotension and bradycardia
what is the overall function of lung innervation
- cause bronchospasm (constriction of airway) to prevent foreign things from entering
*damage to spinal cord —>causes them to not be able to feel ventilation, they don’t have the perception
describe hyperventilation
Alveolar ventilation that exceeds metabolic demands
The lungs remove CO2 at a faster rate than it is produced by cellular metabolism, resulting in decreases PaCO2
* PaCO2 <50
* PaCO2 <36mmHg –> hypocapnia –>respiratory alkalosis
describe hypoventilation
Inadequate ventilation in relation to metabolic demands
It is caused by alterations in pulmonary mechanics or in the neurologic control of breathing
Alveolar minute volume is reduced
Less O2 available in the alveoli for diffusion into the blood
Can be corrected if alveolar ventilation is improved by increases in the rate and depth of breathing
* PaCO2 >50, low PaO2
* PaCO2 >44 mmHg CO2 is retained (hypercapnia) elevated H+ ions in blood resulting in respiratory acidosis.
what are some causes of low partial pressure inhaled O2 (PIO2)? (3)
- high altitude
- when o2 is taken out of your environment (e.g. nitrogen leaking into environment)
- fires with smoke (displaces O2)
what is VQ mismatch
the area in our lungs that are receiving ventilation are not well match with the areas of our lungs that are being perfused
(e.g. have a local atelectasis, alveoli are collapsing= those alveoli not going to give much o2 and not going to remove much CO2, the blood flow to that area is going to see decrease O2 and increase CO2 and pulm capillary are going to constrict and blood flow is going to be directed to other areas in the lungs that have good gas exchange—>when there is pathology going to have more areas in the lungs that have more VQ mismatch)
what are two components of the work of breathing?
- Elastic Forces
o Compliance - Frictional Forces
o Resistance
describe compliance
Ability of alveoli, lungs, thorax to expand under pressure (measure of lungs and chest wall distensibility)
* Determined by alveolar surface tension and the elastic recoil of the lungs/chest wall (elastic and collagen fibers and surface tension)
* THE PRESSURE NEEDED TO KEEP THE LUNGS OPEN!!
o “increase compliance means lungs are easier to expand/inflate, and has lost some elastic recoil”
i.e., Emphysema, aging
o “decrease compliance means that the lungs/chest is abnormally stiff/difficult to inflate”
i.e., Pneumonia, ARDS, pulmonary edema and fibrosis, problems with alveolar
* breath sounds; crackles
* Opposite of Elasticity:
“ability of alveoli, lungs, and thorax to contract/recoil”
“change in alveolar pressure over alveolar volume”
o decreased elasticity (thin rubber band) increased compliance
o increase elasticity (thick rubber band) decrease compliance
what is compliance measured by?
- Volume change/ pressure change (C = V/P)
o V, usually TV
o P, airway or pleural pressure
examples of problems: compliance
- Small airway obstruction will see increased RR and small tidal volume
o You will see increased work of breathing, prolonged expiration, and wheezing - Restricted breathing often seen with pulmonary fibrosis.
o There is stiffening of the lungs of chest wall and decreased compliance
o Small tidal volumes and increased RR
describe resistance
- Frictional Forces
o Resistance
The resistance of the respiratory tract to airflow during inhalation and exhalation - Determined by length, radius, diameter of airways, also density and velocity of gas (tissue and viscous resistance and airway resistance)
o Resistance to flow in the airways depends on whether the flow is laminar or turbulent, on the dimensions of the airway, and on the viscosity of the gas. - THE PRESSURE TO PUSH AIR INTO THE LUNG Normally very low
- Most resistance occurs in nose followed by the larynx/oropharynx
what is resistance measured by?
- pressure/rate of flow (R= P/F) Ohm’s law
o P, trans-airway pressure
o F,
examples of problems: resistance (2)
- Bronchodilation -> resistance is decreased to airflow (caused by SNS)
- Bronchoconstriction -> resistance is increased (caused by parasympathetic receptors)
o Resistance can also be increased by -> pulmonary edema, mucous, tumors, or foreign bodies, airway problems
Breath sounds; wheezes, stridor
describe work of breathing
- Determined by the muscular effort required for ventilation normally low
o The two forces of work that the body needs to do to get air inside lungs - Will increase when compliance and resistance are disrupted.
- More muscular effort needed when lung and chest wall compliance is decreased/ resistance increased
Describe pathophysiological mechanisms that can result in hypoxemia.
Hypoxemia
- Reduced oxygenation of arterial blood (PaO2)
- Results from problems with one more of the major mechanisms of oxygenation
o Oxygen delivery to the alveoli
*Oxygen content of the inspired air (FiO2 or PiO2)
*Ventilation of the alveoli
o Diffusion of oxygen from the alveoli into the blood
*Balance between alveolar ventilation and perfusion (V/Q mismatch)
*Diffusion of O2 across alveolocapillary membrane
o Perfusion of pulmonary capillaries
clinical manifestations of hypoxemia (5)
- Cyanosis
- confusion
- tachycardia
- edema
- decreased renal output
Describe Normal P(A-a) O2 that can result in hypoxemia.
o Partial pressure of O2 in the alveoli is called, PAO2 (the big A)
o Partial pressure of O2 in the arterial blood is called, PaO2 (small a)
o “ALVEOLAR-arterial gradient measures the difference between oxygen concentration in the alveoli and arterial system—important to help narrow the different diagnosis for hypoxemia”
what is Normal P(A-a) O2 dependent on?
Dependent of two factors;
* Amount of O2 in inspired air and is expressed as %, called PiO2
* Amount of alveolar minute ventilation (TV x RR)
Oxygen delivery to the alveoli (#)
Normally 12-15mmHg
* Increases as you age
Problems that are considered as a “Normal A-a”
- Low PiO2 (inhaled oxygen concentration)
(caused by low oxygen in the environment)
o i.e., in an airplane (high altitude) - Alveolar hypoventilation
- Results in an increase PACO2 and decrease in PAO2
- Examples-
o Lack of neurologic stimulation of the respiratory center- over sedation, drug overdose, neurologic damage
- neuromuscular disease, trauma, chest deformity, air trappingo Large airway obstruction
- laryngospasm, foreign body aspiration, neoplasmo Increased work of breathing
- emphysema, severe asthma
These processes are happening outside the body:
* High altitude
* Low oxygen content of gas mixture
* Enclosed breathing spaces (suffocation)
** If the A-a gradient is normal, then the cause of hypoxia is low oxygen content in the alveoli, either due to low O2 content in the air (low FiO2, as in the high altitude) or more commonly due to hypoventilation like the central nervous system (CNS) depression, OHS, or obstructed airways as in COPD exacerbation.
Increased P(A-a) O2 that can result in hypoxemia.
o Problems that are considered as a “Wide A-a”
*V/Q mismatch
* “balance between alveolar ventilation and perfusion”
o V: amount of air getting into alveoli
o Q: amount of blood perfusing the capillaries around the alveoli
* Most common cause of hypoxemia!!
* Refers to an abnormal distribution of ventilation and perfusion
examples of Increased P(A-a) O2 : VQ mismatch
o Atelectasis
o Pulmonary embolism
o Acute respiratory distress syndrome
i.e., mucus plug-
* mucus impedes some ventilation
* there is low ventilation in relation to blood flow
o asthma
o chronic bronchitis
o pneumonia
describe shunt that can result in hypoxemia.
- a form of mismatch
o Very bad (worse than V/Q)
o “Alveoli are not ventilating enough” (low V/Q)
o INADEQUATE VENTILATION OF WELL-PERFUSED AREAS OF THE LUNGS
o No ventilation but there is blood flow through capillaries
When blood passes through portions of the pulmonary capillary bed that receive no ventilation, right-to-left shunt occurs, resulting in decrease systemic PaO2 and hypoxemia
o The alveoli could be filled with infection, fluid, secretions
As a result- there is no way for air to reach capillary bed for oxygen/CO2 exchange
what are some examples of shunt
ARDS/ pulmonary edema (alveoli are filled with fluid)
Asthma (bronchoconstriction)
Atelectasis
describe Alveolar Dead Space that can result in hypoxemia.
- “Alveoli are not perfused enough” (high V/Q)
- POOR PERFUSION OF WELL VENTILATED PORTIONS OF THE LUNGS results in “wasted ventilation”
o i.e., embolus- most common cause of high V/Q
impairs blood flow to a segment of a lung
describe Diffusion of O2 from alveoli into the blood (diffusion defect) that can result in hypoxemia.
- “Diffusion of oxygen across alveolocapillary membrane abnormality”
o The membrane is thickened or surface area for the diffusion is decreased!
o Alveoli can’t inflate fully - CO2 diffusion is not altered as it can easily diffuse in and out
- Example-
o Pulmonary Edema
There is excess fluid that can come around alveoli (abnormal thickness/tissue swelling)
o Fibrosis
Formation of fibrous lesions/tissues makes it thick - Interstitial lung disease (ILD)
Increases the time required for diffusion
o Emphysema
Destruction of alveoli, decreases the alveolocapillary membrane surface area available for diffusion
