respiratory integration Flashcards
what does low Sa02 and high CO2 cause
Hypoxaemia
Hypercapnia = hypercarbia
Poor Tissue Perfusion
Poor Oxygen Capacity
what does respiratory failure cause
Due to resp. path.
compensation
Cardiac Failure- Low Output
Anaemia
what is the difference between dyspnoea, apnoea, hypopnea and bradypnoea
Dyspnoea – difficulty or discomfort in breathing
Hypopnoea – low minute ventilation, low tidal volume (Overly shallow breathing)
Bradypnoea – Low breathing rate
Apnoea – breathing stops, muscles of resp stop
what is narcosis
a state of confusion, stupor, unconsciousness or euphoria (like drunkenness)
what are narcotic drugs
opioids: morphine & heroine, reduce respiratory drive
what are the types of narcosis
N2 Narcosis – during scuba diving, high partial pressure of N2 in blood leads to impairment of judgment. Can be relieved by ascending to less depth (i.e. toward surface)
CO2 Narcosis – when plasma CO2 is chronically high, body reduces homeostatic response to CO2 (ie less respiratory drive)
is it possible to have a high PaO2 but a low SaO2
yes - Hb pathologies, other gases (CO) & poisons interfering with Hb binding to O2, etc
but not high SaO2 and low PaO2 - High SaO2 will unload O2 into solution until equilibrium is reached
so SaO2 is main measure of oxygen delivery to tissues
what is clubbing
growth of nail beds due to chronic hypoxia
what causes respiratory failure
Must be due to respiratory pathology
Cannot be due to homeostatic respiratory compensation for kidney or liver pathologies
what causes respiratory failure type 1
Hypoxaemia, normal arterial CO2
breathing appropriately
Inspired O2 does not arrive inside capillaries of perfused alveoli (or at high concentration inside aorta)
eg V-Q mismatch, diffusion problems, shunt,
Transfer factor (DLCO)
what causes respiratory failure type 2
Hypoxaemia with pathologically elevated CO2 due to respiratory causes
hypoventilation
what is anatomical dead space
no gas exchange occurs
In adult: 150 ml, of tidal volume of 500 ml
While exhaling, this air is identical to atmospheric air
Physiological Dead Space = anatomical dead space + alveolar dead space
what is residual volume
amount of gas remaining in the lungs after maximal expiratory effort
While inhaling, this air is identical to expired (ie high CO2, lower O2) alveolar air. Arrives from deepest recesses of alveoli.
what is infection of airways
Airways have mucus and cilia to protect alveoli When airways collapse or clog, CO2 builds up behind obstruction makes breathing (moving air in and out of lungs) difficult
what is infection of alveoli
When alveoli collapse or clog, no CO2 can leave blood: alv dead sp
This is the reason pneumonia causes V-Q mismatch
what results in type 2 respiratory failure
acidosis
Increased airways resistance (COPD, asthma, suffocation)
Reduced breathing effort (e.g. narcotic drugs, opiates)
Partial closure of airways (e.g. chronic bronchitis)
Neuromuscular problems (e.g. myasthenia gravis)
Chest defects that interfere with breathing
what are types of type 2 respiratory failure
obstructive and restrictive
what is obstructive lung disease
An obstruction (or ubiquitous obstructions) in airways increase resistance to air flow
Typically more difficult to exhale
Rate of exhalation (FEV1) is smaller
But in many cases the total volume is preserved
what is restrictive lung failure
Lung/chest stiffness (or neuromuscular dysfunction) limit ability of lung/chest to drive airflow
more difficult to inhale
TOTAL VOLUME of exhalation, FVC, is smaller
So is the RV and the FRC (and thus the TLC)
what are examples of obstructive airways
COPD
Asthma
Bronchiectasis
CF
what is COPD
Often a mixture of emphysema and chronic bronchitis
Chronic bronchitis – airways narrow, mucus, cough
Emphysema – alveolar walls destroyed, making big air spaces that cannot be emptied, shortness of breath and fatigue
What are blue bloaters in COPD
air trapping (large chest), cyanotic. Mostly Bronchitis
What are pink puffers in COPD
Not cyanotic, increase internal airway pressure during exhalation to keep alveoli and airways open. Mostly Emphysema
CO2 retention – COPD patients who receive excessive supplemental O2 lose respiratory drive
why are pressure-volume curves are important in intubated (mechanically-ventilated) patients
Increases in impedance can be due to an increase in airway resistance, or a decrease in compliance
Airway Resistance is NOT measured at equilibrium
what is hysteresis in compliance
Normal. Slope of pressure vs volume is 1 / Impedance. Low slope = high impedance. Hysteresis is caused by finite delay of airflow due to friction in airway
Restriction. Increased impedance due to decreased compliance.
Obstruction. Increased impedance due to airway obstruction.
what is air trapping in obstructive disease
When increased air (with expiratory levels of O2 & CO2) remains in the lungs at the end of expiration.
Caused by increased airway resistance (R)
Results in Increased Residual Volume
what happens if air trapping is chronic
lungs remodel such that
Total Lung Capacity is Increased
Thoracic cavity may change shape
Detected as increase in Residual Volume
what is spirometry like normal, obstructive and restrictive
A = Normal, late breath is convex B = obstructive, late breath is concave C = restrictive, late breath is convex like normal, but maximal volume is low b/c had less inspired air to start
what are restrictive pulmonary diseases
Difficulty with inhalation Interstitial lung disease e.g. pulmonary fibrosis Autoimmune diseases that reduce lung compliance Obesity e.g. obesity hypoventilation syndrome Scoliosis Neuromuscular disease E.g. muscular dystrophy or amyotrophic lateral sclerosis (ALS)
what is hypoventilation as a compensatory breathing change
Hypoventilation to acidify In metabolic alkalosis Vomitting Antacids Dehydration>Aldosterone Result: High CO2 levels
what is hyperventilation as a compensatory breathing change
Hyperventilation to de-acidify In metabolic acidosis Diabetic Ketoacidosis Chronic kidney disease (“kidney failure”) Also psychogenic Pain Anxiety Result: Low CO2 levels
what is respiratory failure type 1
Low PiO2 (e.g. at high altitude)
V-Q mismatch (e.g. pulmonary embolism)
Diffusion problem (e.g. Pulmonary Hypertension)
Shunt (when some non-oxygenated blood is mixed with oxygenated blood in aorta blood)
Why does type 1 resp failure lead to hypoxaemia but not hypercapnia?
excess of O2 in compared to what blood can take up and excess CO2 in blood compared to expired air
the airways remain patent, there is a homeostatic increase in minute ventilation to dispose of the extra CO2
what is an extreme type of V/Q mismatch
Physiological dead space Ventilation occurs, but NOT perfusion Example: pulmonary embolism Shunt Perfusion occurs, but NOT ventilation Examples: complete airway obstruction, lobar pneumonia True shunt does *not* respond to breathing 100% O2 VQ mismatch will benefit from 100% O2
what causes V-Q Mismatch, Perfusion with impaired Ventilation
Conditions that cause changes in or collapse of a subset of the alveoli such as Lobar Pneumonia Asthma Pulmonary oedema
what causes Ventilation with impaired Perfusion
pulmonary embolus or
decreased cardiac output
Shock
Extreme V-Q Mismatch: How does Alveolar Collapse lead to Low O2 Saturation
pneumonia - lungs filled with with fluid but other lobes ventilate normally
CO2 high - vasoconstriction stops perfusion
alveolus collapses, CO2 does NOT build up as cannot unload where liquid is
So this region of lung is perfused, but blood gets no O2
Air sacs downstream of blocked airway accumulate CO2
