respiratory system 1 Flashcards
lung compliance
distensibility of the lungs
what does a spirometer measure
lung volumes
what does an oesophageal balloon measure
pleural cavity pressure
what is the balloon for in an oesophageal balloon
to prevent mucosa from blocking the catheter tip
equation for lung compliance
C=(delta)V / (delta)P
slope of volume v pressure graph
slope is taken at the steepest point which occurs at FRC
what allows alveolar walls to stretch
elastic fibres and surface tension
what is hysteresis
the difference in pressure volume plot between inflation and deflation
how does pulmonary fibrosis effect lung compliance
it decreases it as alveoli become stiffened due to collagen formation
what is obstruction
narrowing of the airways
restrictive ventilatory defect
restriction of lung volumes
what is minute volume (equation)
minute volume= tidal volume x respiratory rate
what lung measurement is preserved the longest during disease and why
what occurs to all other volumes
minute volume as it is essential in maintenance of blood gases
they decrease
what is the preferred lung volume to be measured to diagnose restriction
total lung capacity
what is the clinical significance of restrictive ventilatory defect
the work of breathing will increase as increased load will be felt by the respiratory muscles to breathe a normal minute volume (patients will complain of dyspnoea)
what is functional residual capacity
the volume of air in the lungs at the end of quiet expiration
how does lung restriction effect functional residual capacity
why
lower FRC as to reduce the work of breathing because the load on the respiratory muscles is decreased when stiff lungs are under less stress
type 1 respiratory failure
hypoxemia
low pO2 normal pCO2
damage to lung tissue which prevents adequate oxygenation of the blood
type 2 respiratory failure
hypoxia & hypercapnia
low pO2 high pCO2
occurs when alveolar ventilation is insufficient to excrete the carbon dioxide being produced and introduce new oxygen
does hypoxia cause vasoconstriction or vasodilation of pulmonary arteries
vasoconstriction (in contrast to systemic vessels which dilate)
this diverts blood from poorly oxygenated regions
pulmonary oedema
excess fluid in the lungs most usually caused by heart problems
bronchiectasis
abnormal widening of the bronchi or their branches, causing a risk of infection
pneumothorax
a collapsed lung
occurs when air leaks into the space between your lung and chest wall
this air pushes on the outside of your lung and makes it collapse
a pneumothorax can be a complete lung collapse or a collapse of only a portion of the lung
what is silent chest in asthma
the airways are so constricted that even a wheeze can’t be heard
pulmonary fibrosis
replacement of elastin fibres with collagen fibres
does pulmonary fibrosis < or > lung compliance?
decrease
emphysema
elastin fibres are destroyed by enzymes rather than replaced
does emphysema < or > lung compliance
increase (so NOT a restrictive defect- it is obstructive)
2 causes of emphysema
- cigarette smoking which causes activation of elastase release from inflammatory cells. elastase is the enzyme that destroys elastic fibres
- a rarer cause is the congenital disease alpha 1- anti trypsin deficiency
respiratory distress syndrome
surfactant deficiency
who often gets respiratory distress syndrome
premature babies
adults in intensive care
what is peak flow measurement used for
to monitor obstructive airway diseases (units are L/min)
what does spirometry measure
measures the volume of gas exhaled and the rate of exhalation during a forced expiratory manoeuvre
FVC
volume of air subject can eject from full lungs during maximal expiration after full inspiration
FEV1
volume of air that can be ejected in the first second of the forced expiratory manoeuvre
what diseases can reduce peak flow and spirometry measurements
asthma & COPD (also emphysema & bronchitis)
what diseases can a low FEV suggest?
restrictive ventilatory defects such as pulmonary fibrosis, asbestosis, pulmonary oedema and muscular dystrophy
what diseases can reduced FEV1 (with slightly reduced FVC) suggest?
obstructive ventilatory defects including asthma, COPD and bronchiectasis
activation of what receptor causes bronchoconstriction
occurs due to the action of Acetylcholine on Muscarinic (M2 & M3) receptors on the bronchial smooth muscle
activation of what receptor causes bronchodilation
β2-adrenergic control
what drugs should be avoided in asthma
beta blockers and NSAIDS
what disease does low FEV1 and FVC suggest?
restrictive ventilatory defects eg pulmonary fibrosis (also reduced TLC)
