Anatomy - COPD Flashcards
What happens to PaO2 and PaCO2 during exercise?
They remain normal
What does graph look like for ventilation against exercise intensity?
What is the mechanism during the start of exercise?
Neural mechanism - proprioceptors detect movement causing anticipation of extra demand
What happens to ventilation during moderate exercise and what is the mechanism?
Ventilation rate = exercise when graph plateaus
Mechanism = CO2 released from active cells causes increase in ventilation
Central chemoreceptors maintain PaCO2 and PaO2
What happens to ventilation during strenuous exercise and what happens?
Ventilation increases due to high body temperature and metabolic acid production
VR can increase from 5-6 l/min to 120 l/min
Hyperventilation = decrease in PaCO2
What are the cardiovascular adaptations to exercise?
- Skeletal muscle contraction
- Activation of sympathetic nervous system
- Myocardial contractile force
- Cardiac acceleration
- Peripheral vasoconstriction
- Blood vessel compression
- Translocation of blood from peripheral vessels into heart and lungs
- Cardiac output increase and blood-flow to active muscles
What happens during acute exposure to high altitude?
Peripheral chemoreceptors detect acute hypoxia so try to increase breathing
+ ventilation = less PaCO2 and alkylation of cerebrospinal fluid
+ breathing = die from alkalosis
- breathing = die from hypoxia
What happens during chronic exposure to high altitude?
Mild hypoxia = less PO2
+ ventilation from hypoxic drive
- PCO2
- PCO2 = + cerebrospinal fluid alkylation = + HCO3-
HCO3- exported by choroid plexus cells to correct pH
What happens hours and days after chronic high altitude exposure?
Breathing controlled around lower PCO2 (hours)
Correction of blood alkalinity by HCO3- excretion in urine (days)
+ oxygen carrying capacity of blood
What happens on return from chronic high altitude exposure?
Left upper quadrant (abdomen) pain from spleen enlargement
+ cardiac output
Correction of systemic acid-base imbalance
What are the two types of chemoreceptors and where are they found and what are they sensitive to?
Central chemoreceptors –> in medulla –> sensitive to change in H+ concentration and pCO2
Peripheral chemoreceptors –> within aortic arch and carotid arteries –> sensitive to changes in arterial pO2 and pH
What happens in peripheral chemoreceptors?
Decreased arterial O2 = hyperventilation
Stimulated when arterial pO2 = below 13.3 mmHg
+ PCO2 = less importance than CCR response
Fall in pH = carotid detects it, not aortic bodies
What happens during acidic pH imbalance?
Hypoventilation = respiratory acidosis
Fall in pH
+ H+ concentration
+ CO2 in lungs
Compensation = kidneys excrete + [H+] and + [HCO3-] reabsorption
What happens during alkaline pH imbalance?
Hyperventilation = respiratory alkalosis
Increase in pH
- [H+]
Decrease in CO2
Compensation = kidneys reabsorb + [H+] and + [HCO3-] excretion
What happens in uncontrolled diabetes when there’s a pH imbalance?
Metabolic acidosis
- ability for kidney H+ excretion and HCO3- reabsorption
Compensation = + ventilation = - PaCO2
Why do you vomit?
pH imbalance causing metabolic alkalosis
- acid
+ base - + HCO3-
- ventilation = + PaCO2
What are the order of priority of responses to PCO2, PO2 and pH?
PCO2
pH
PO2
What are the properties of response to PCO2?
CCRs = most sensitive to PCO2 change
Levels held within 0.3kPa
PCRs detect rapid PCO2 changes but less sensitive
Levels held within 1.3 kPa
PCO2 controlled to avoid acid-base problems
What are the properties of the response to pH?
- pH = +ventilation
Influenced by PCO2 levels
What are the properties of response to PO2?
PCRs detect PO2 changes
Have wider control margin
PCRs stimulation when levels below 13.3 kPa
Controlled to avoid hypoxia
Health problem related to chemical ventilation?
Cheyne-Stokes –> CNS disease, head trauma, + intracranial pressure, heart failure
What is the function of neural regulation?
Sets ventilation rhythm and pattern
Controls respiratory muscles
Neural control = fast acting impulses
What is the function of chemical regulation?
Detects central and peripheral arterial PCO2 and pH and peripheral PO2
What is a health issue related to nervous ventilation?
Respiratory depression –> rate / depth of respiration = insufficient to maintain adequate gas exchange, a result of medullary and pons effects, some drug side effects, is reversed by analeptics
What is the dorsal respiratory group and it’s function?
Medulla respiratory control system
- DRG fibres innervate diaphragm and external intercostal muscles
- Inspiration caused by diaphragm contraction and thoracic cavity expansion
- DRG neurons = switch on (inspiration) for 2s and switch off (expiration) for 3s causing rhythmic pattern
What is the ventral respiratory group and it’s function?
Medulla respiratory control system
- VRG fibres innervate abdominal muscles and internal intercostal muscles
- Activity = enhanced during forced expiration, small role in inspiration
What are the 2 types of pons respiratory control systems and their function?
Pneumotaxic centre:
Signals transmitted to DRG
Role = limit inspiration
Fine-tunes breathing and sends inhibitory impulses to DRG
Limit inspiration period to 2s
Prevents lung over-inflation
Apneustic centre:
Responsible for prolonged inspiratory gasps (apneusis)
Prolong DRG stimulation
Apneusis observed in severe brain injury
What is the role of the vague nerve in respiratory control?
Sends afferent information from lungs to DRG
Role = prevent over-inflation of lungs by switching off inspiration
What is the function of the cerebral cortex in respiration?
- Stimulates inspiratory muscle motor neurons
- Bypasses medullary centres when consciously controlling breathing
- Limited ability to breath-hold à respiratory centres automatically reinitiate breathing when O2 conc. in blood reach critical levels
- Drowning victims = eventually reinstate breathing, water in lungs as result
What is the function of the hypothalamus in ventilation?
- Strong emotions, pain, changes in temperature = can alter respiratory rate and rhythm
- Apnoea = can be induced by anger, pain or temperature decrease
- Tachypnoea = can be induced by excitation or temperature increase
What are stretch receptors and their function?
Respiratory reflexes
- In smooth muscle of trachea and bronchi
- Sensitive to lung expansion
- Lung expansion – respiratory centre – inspiration is shorter and shallower – prevent lung over-inflation
What are juxtapulmonary receptors and their function?
Respiratory reflexes
- In alveolar wall between epithelium and endothelium close to pulmonary capillaries
- Stimulation = congestion, oedema, histamine
- Activation = apnoea or rapid shallow breathings, bronchoconstriction and mucus secretion
What are irritant receptors and their function?
Respiratory reflexes
- Between epithelial cells
- Sensitive to irritant gases, smoke, dust
- Activation = results in rapid, shallow breathing, cough, bronchoconstriction, mucus secretion, augmented breaths (gasps)
What are the properties of respiratory reflexes?
- Send signals via afferent fibres of vagus nerve, to respiratory centres
- Stimulation of bronchiole receptors = airways constrict
- Stimulation of tracheal receptors = coughing
- Stimulation of nasal cavity receptors = sneezing
What are the 6 steps of prescribing?
- Step 1: Define the patient’s problem
- Step 2: Specify the therapeutic objective
- What do you want to achieve with the treatment?
- Step 3: Verify the suitability of your P-treatment
- Check effectiveness and safety
- Step 4: Start the treatment
- Step 5: Give information, instructions and warnings
- Step 6: Monitor (and stop?) treatment
What 3 things must you remember when prescribing?
Allergies
Drug interactions
Monitoring
What are the different unit types for dosages?
- g, mg, or microgram
- Microgram not mg or mcg
- e.g. 125 micrograms digoxin
- Nanogram not ng
- mL for volumes e.g. 125 mg /mL
- Write ‘Units’ in full (not u)
- e.g. insulin, heparin
- Check is appropriate for age, weight, renal function, hepatic function
What information must you include for as required drugs?
- Indication
- Frequency
- Minimum dosage interval
- Maximum dose in 24 hours
What to remember during patient counselling?
- What the medicine is for
- When to take the medicine
- How to take the medicine
- Dose
- Frequency
- Key side effects
- What to do if miss a dose
- How long for treatment
What things stimulate acute inflammatory response?
- Microorganisms
- Trauma
- Ischaemic necrosis
- Radiation damage (sunburn)
- Chemical damage
What is the purpose of the acute inflammatory reaction?
- Destroy and neutralise damaging agent
- Liquefy and remove dead tissue
- Prepare damaged area for healing
What allows the acute inflammatory response to carry out it’s function?
Acute inflammatory exudate
Composed of:
- Fluid
- Fibrin
- Neutrophils
How does acute inflammatory exudate work?
- Fluid dilates toxins
- Fluid carries nutrients, mediators and antibodies
- Neutrophils phagocytose living tissue (bacteria) and necrotic debris
What happens during stage 1 of exudate formation?
- Dilation of blood vessels near damaged tissue
- Increase in blood flow initially, then slows
- Axial flow pattern of blood is lost
What happens during stage 2 of exudate formation?
- Increased capillary permeability
- Water, salts and protein leak into damaged area
- Fibrinogen = important protein
What happens during stage 3 of exudate formation?
- Neutrophils adhere to endothelium
- Neutrohpils migrate to damaged area
- Fibring formed in tissues
What are the 4 types of exudate?
Serous
Purulent
Fibrinous
Fibrino-purulent
What happens during the resolution stage of inflammation?
- Exudate eliminates damaging agent
- Macrophages remove dead cells and exudate
- Cells re-grow
- Normal tissue function and structure returns
What happens during the resolution stage with no tissue damage?
- No damage to architecture
- Exudate forms
- Liquified exudate is reabsorbed
What is an abscess and what causes them?
Large accumulation of liquid purple tissue exudate (puss) in area where tissue damage has led to extensive necrosis
Bacteria
What are the steps of organisation of repair?
- Remove debris
- Grow new vessels
- Lay down collagen
- Mature collagen
- Granulatin tissues matures to a scar
What are the steps of organisation of exudate?
- Capillaries grow into damaged area
- Fibroblasts migrate and multiply
- Fibroblasts synthesis collagen
- New capillaries regress
- Fibroblasts regress
What are the mechanisms of chronic inflammation?
- Macrophage is main effector
- Acitvated by gamma interferon
- Phagocytic role
- Secretory role
What is granulomatous inflammation?
Form of chronic inflammation where neutrophils are ineffective and macrophages are involved early
Granuloma formed from aggregates of macrophages around damaging agent
