Physiology Flashcards
definition of sleep
a behavioural state characterized by decreased awareness of external environment, decreased reactivity to stimuli, but with the capability to return rapidly to wakefulness.
association between sleep deprivation and
- mortality and morbidity - decreased cognitive function
in general, an elevated PCO2 is due to
inadequate alveolar ventilation
infective exacerbations of COPD are caused by what
bacterial bronchitis increased bronchospasm
how long does oxygen require to fully saturate in the lungs
0.25 seconds
mechanical effects of restrictive lung diseases
- breathlessness - increased work of breathing - reduced lung volumes - altered pattern of breath - reduced maximum ventilation
complications of asthma
- death - atelectasis - pneumothorax - airway remodelling - irreversible obstruction - chronic hypoxia –> pulmonary hypertension –> cor pulmonale
brainwave change, EMG change and EOG change from NREM to REM
EMG paralysed (inhibited) EEG becomes more desynchoronized EOG - rolling eye movements
clinical signs of pulmonary hypertension and RVH
- right ventricular heave - loud P2 and 4th heart sound - increased JVP with v waves
how does emphysema cause airway obstruction
due to loss of elastic recoil
what is the main regulator of breathing during sleep
chemical control (central and peripheral chemoreceptors)
what other sensors (other than chemoreceptors) contribute to breathing
- pulmonary stretch receptors - irritant receptors - J receptors - upper airway receptors - joint and muscle receptors - pain
what is the compensatory mechanism elicited by the lungs when there is low ventilation
vasoconstriction - directs perfusion away
what does the ventrolateral preoptic nucleus do
inhibits the arousal centres - sleep until the arousal centres get the upper hand - inhibit the VLPN - prevents sleep
summary of gas exchange and mechanical effects of restrictive lung diseases
- increased sensation of breathing - increased elastic WOB - reduced lung volumes - altered pattern of breathing - reduced maximum ventilation - abnormal gas exchange, which worsens with exercise
when do we do most of our deep sleep and most of our REM sleep
deep sleep - first part of the night REM - second half of the night
volume of CO2 and O2 removed/ produced per minute
200 ml/min CO2 250 ml/min O2
what are the physiological effects of disrupting the A-C membrane?
- abnormal gas exchange - abnormal lung mechanics - pulmonary vascular complications
pathogenesis of chronic bronchitis
chronic irritation by inhaled substances causes increased mucus production in the larger airways (due to hypertrophy of mucus secreting glands and increased goblet cells) and airway inflammation, scarring and narrowing in the smaller airways
what do central chemoreceptors respond to
H+ do not respond to oxygen!
Ventilation and arterial CO2, O2 and pH during metabolic acidosis
Ventilation is excessive for oxygen consumption PaO2 >100 PaCO2
What is ficks law
the rate of diffusion is proportional to the surface area, the constant, and the difference in partial pressures, and inversely proportional to thickness
in general, elevated PaCO2 is due to
inadequate alveolar ventilation
what is the function of orrexin
stabilises the arousal system
why does the WOB increase in restrictive diseases
because the inspiratory muscles need to generate higher pressures to overcome the reduced compliance of the lungs –> leading to recruitment of accessory muscles, increased oxygen consumption by respiratory muscles and risk of respiratory muscle fatigue if airway obstruction is severe
basal rates of CO2 and O2 (ml/min)
CO2 production - 200 ml/min O2 use - 250 ml/min
surface area of alveolar capillary membrane
50-100 m2
what drives circadian rhythms
the suprachiasmatic nucleus
thought during wake, NREM and REM
W - logical, progressive NREM - day dreamy REM - illogical, bizzare
main causes of increased capillary hydrostatic pressure
Left ventricular dysfunction mitral stenosis fluid overload pulmonary veno-occlusive disease
what happens to CO2 with sleep
at onset - decreased drive - decrease in minute ventilation - leads to increase in CO2 - stimulates breathing - equilibrium reached (but CO2 slightly higher than wakefulness)
what are the forces that inspiration has to overcome
resistive - airflow through bronchi elastic - expansion of lungs and chest wall
2 major arousal systems acting on the cerebral cortex and thalamus
cholinergic ascending system - affects the thalamus monoaminergic system - innervates the cortex
what happens to ventilatory components during anxiety
VE excessive for oxygen consumption PaO2 >100 PaCO2
thickness of alveolar capillary membrane
0.5 microns
how does smoking cause emphysema
- draws in inflammatory mediators - neutrophils release proteases that break down elastin - inhibition of anti-proteases
what tells you (from lung function test) that a patient is gas trappin
high TLC, RV and RV/TLC
why doesnt the pulmonary artery pressure increase during exercise in a normal person
due to recruitment and dilatation of pulmonary vessels
mechanisms to increase pulmonary vascular resistance
- VASOCONSTRICTION = chronic hypoxia –> vasoconstriction (spasm of SM) –> diverts blood through just a few vessels so increases the pressure - OBLITERATION= chronic inflammation –> destruction of alveoli and BVs due to fibrosis –> volume of capillar
definition of bronchiectasis
irreversible, abnormal dilatation of bronchi/bronchioles
how many sleep cycles are typical per night
4-6
mean pulmonary artery pressure
15 mmHg
definition of chronic bronchitis
clinical definition persistent cough productive of sputum for at least 3 months in 2 consecutive years for which no other cause can be identified
how long is a typical sleep cycle
90-120 minutes
typical sleep requirement of infants
up to 18 hours
pneumonic for causes of disease and each meaning
I DIVINE TIME Congenital/Genetic Acquired: - Infectious - Degenerative - Inflammation/Immune reactions - Vascular - Iatrogenic (drugs, surgery, radiotherapy) - neoplastic - environmental - trauma - idiopathic - metabolic - endocrine
whee does laminar and turbulent flows occur
laminar - in small airways (poiseulles law applies - 8nl/pi x r4 turbulent - during high flows (large airways)
normal lymphatic flow from the lungs
20ml/hour
definition of asthma and then simplified definition
- increased responsiveness of the airways to various stimuli leading to episodic bronchoconstriction which is at least partly reversible - reversible bronchoconstriction
main obstructive lung diseases
COPD - chronic bronchitis, emphysema, small airway disease asthma bronchiectasis
normal range for HCO3
22-28
main causes of increased capillary permeability
toxins sepsis multiple trauma aspiration of gastric acid
complications of chronic bronchitis
- superimposed infective exacerbations - hypoxia, pulmonary hypertension, cor pulmonale - squamous metaplasia –> squamous dysplasia - premalignant
reasons for breathlessness (broadly)
respiratory cardiac muscle weakness metabolic anaemia psychogenic
how long is the Hb in contact with the blood-gas barrier at rest
0.75 seconds
pathophysiology of asbestosis
progressive, diffuse inflammation and fibrosis of lung parenchyma causing disruption and destruction of the A-C membrane
Obstructive and restrictive lung diseases are a group of lung diseases which are:….
chronic, diffuse and non-infectious
what happens at anaerobic threshold
- disproportionate increase in VE for work - causes PaCO2 to decrease and pH to drop slightly due to lactic acid production
1 gm combines with how much O2
1.3 ml O2
What does ARDS cause
- type 1 respiratory failure due to low V/Q units and shunt and stiff lungs
diseases that can disrupt the A-C membrane
- inflammation - infection -fibrosis -emphysema -fluid -cancer
what do peripheral chemoreceptors respond to
reduced oxygen, reduced pH, increased CO2
over a long period, people with severe OSA can develop…
(chronic hypoxia, chronic hypercapnea, and compensated respiratory acidosis (HCO3- is high) Re-setting of the respiratory centre –> day time hypoventilation)
main 2 reasons thought for why we need sleep
brain development repair and maintenance
what happens to the controllers of breathing during sleep
loose higher centres, emotional drive and non-specific inputs other inputs downregulated significantly
definition of emphysema
abnormal, permanent enlargement of air spaces distal to the terminal bronchiole (from destruction of the alveolar wall without fibrosis)
what are the effects of pulmonary oedema
-mechanism changes - (decreased compliance, restrictive ventilatory defect, increased airway resistance and increased WOB) - reduced gas exchange - due to shunt, low V/Q and diffusion impairment - increased pulmonary vascular resistance
rate of diffusion is determined by
Ficks Law
symptoms of OSA
- snoring - witnessed apnoeas - arousals - choking - mood change, poor memory, decreased libido - difficult to treat HT, unexplained RF
what do you do/feel as a result of increased airways obstruction
-increased sensation of breathing - increased respiratory muscle effort - active exhalation - prolonged inspiration and expiration - altered pattern of breathing - reduced maximum ventilation - sometimes gas trapping
what defines obstruction via spirometry
FEV1/FVC lower than 80% in younger and 70% in elderly
compliance of the lungs is effected by:
- tissue composition - surface tension in alveoli
5 functions of the lungs
1) protect the heart from physical trauma 2) act as a flotation device 3) oxygenate pulmonary arterial blood 4) remove carbon dioxide from blood 5) maintain acid-base balance
what causes restrictive lung diseases
inflammation and fibrosis of inter-alveolar septa
definition of breathlessness
RECOGNITION by the subject of an INAPPROPRIATE relationship between RESPIRATORY WORK and TOTAL BODY WORK
what does the Suprachiasmatic nucleus do
- receives input from rods, cones and meanopsin - receives input from the intergeniculate leaflet of the lateral geniculate thalamic nulceus - projects to the paraventricular nucleus which connects with the pineal gland which secretes melatonin
causes of hypoventilation (5)
- reduced respiratory centre activity - neuromuscular disease - chest wall deformity - gross obesity - SDB
main components controlling breathing
- medulla - inflation reflex - peripheral stimuli (pain, touch, temp) - Joint receptors - non-specific drive - central and peripheral chemoreceptors - emotional stimuli
how much oxygen in the blood
200ml / Litre
what is the sleep centre
ventrolateral preoptic nucleus
brainwave change, EMG change and EOG change from W to sleep
EEG more synchornized and lower in amplitude EMG - reduced EOG - slow rolling eye movements
pathogenesis of bronchiectasis
- airway gets filled with mucus - infection behind it –> severe destruction of airways and surrounding elastic tissue
definition of small airways disease
chronic inflammation, fibrosis and obstruction of terminal bronchioles caused by cigarette smoke
definition of OSA
transient obstruction of the throat during sleep preventing breathing, and disturbing sleep
causes of pulmonary hypertension
- increased LA pressure - increased pulmonary blood flow - increased pulmonary vascular resistance
MUD reasons for dyspnoea
clinical disease diseased or deconditioned psychogenic maximum effort
complications of emphysema
- hypoxia (caused by airways obstruction and low DLCO) - pulmonary hypertension –> cor pulmonale - pneumothorax
effect of inspiration on cardiovascular system
- decreased venous return to LA - decreased CO - decreased systolic BP on inspiration
symptoms of psychogenic breathlessness
- need to take deep inspiration - at rest, but not at exercise - anxiety - tingling in fingers, feet, face or head - oppressive/compressed chest
movement during W, NREM and REM
W - continuous, voluntary NREM - move alot REM - commanded but inhibited
sensation and perception during wake, NREM and REM
W - vivid, externally generated NREM - Dull or absent REM - vivid, internally generated
How do restrictive lung diseases look on xray
ground-glass/reticulo-nodular
What are kerley b lines and what are they caused by
dilated interlobular septa caused by dilated lymphatics
what is the ratio of increasing HCO3 for increase in CO2
2-3 mmol/L increase in HCO3- for every 10mmHg increase in CO2
how does smoking predispose to pulmonary infection
- inhibition of the muco-ciliary esculator - increased mucus - inhibition of leukocyte function - direct damage to the epithelial layer
respiratory causes of dyspnoea
airways disease alveolar disease pulmonary vascular disease pleural and chest wall disease respiratory muscle disease
effects of sleep deprivation
- cognitive impairment - impaired immune system - risk of diabetes type 2 - increased HRV - risk of heart disease - decreased reaction time and accuracy - tremors -aches - growth suppression - risk of obesity - decreased temp
