Chronic Hypoxic Lung diseases Flashcards
What happens to mean pulmonary artery pressure in high altitude hypoxia?
Increases due to increased pulmonary vascular resistance which is asymptomatic & well tolerated in most individuals
How is COPD charcterised?
Airway obstruction that is not completely reversible
What are 2 components of COPD?
Emphysema
Small airways disease
Define Emphysema.
Irreversible destruction of airways distal to terminal bronchioles
What are 2 major causes of COPD worldwide?
Cigarette smoking
Indoor exposure to biomass combustion
What is respiratory failure?
Failure to maintain normal PaO2 and PaCO2 under normal environmental conditions
What is type 1 respiratory failure?
Hypoxaemia with normal or reduced PaCO2
What is type 2 respiratory failure?
Hypoxaemia with hypercapnia
What are 3 causes of abnormal blood gases in lung disease?
Increased V-Q mismatch
Generalized alveolar hypoventilation
Diffusion block
How do lung diseases affect V-Q?
Alter regional compliance & resistance in a non-homogenous way
Cause intrapulmonary shunt
What does V-Q mismatch produce?
Large regions of alveolar hypoxia in COPd & most of the cardiac output passes through hypoxic alveoli
What does hypoventilation cause?
Widespread alveolar hypoxia throughout lungs in COPD
What 4 respiratory diseases does pulmonary hypertension occur in?
Idiopathic pulmonary fibrosis
Cystic fibrosis
Kyphoscoliosis
Obesity hypoventilation syndrome
What is the upper limit of normal PA pressure?
< 20mmHg
How is pulmonary vascular resistance calculated?
PVR = PAP - LAP(mmHg)/CO (l/min)
What are 2 structural changes that are directly caused by COPD?
Destruction & loss of vascular bed
Obstruction of vascular lumen caused by inflammation
What are 2 possible mechanisms of pulmonary hypertension in COPD?
structural changes
hypoxic pulmonary hypertension
What are 4 characteristics of PAH without alveolar hypoxia?
Progressive increase in mPAP
Progressive reduction in exercise tolerance with dyspnoea
right ventricular failure
50% mortality after 2 yrs
What are the effects of arterial septostomy in PAH?
Reduction of flow through RV & lungs - reduced mPAP
Entry of desaturated blood into LA
mixing of venous & pulmonary venous blood in LA
Reduced SaO2
increased survival & exercise capacity
What is brisket disease?
Susceptible cattle migrate to high altitude and develop pulmonary hypertension resulting in right heart failure, oedema (brisket) & death
What are charcteristics of subacute mountain sickness?
Excessive Pulmonary hypertensiom
CO falls
Normal Hb abd SaO2
What is the enlarged heart due to?
Right ventricular failure
Is aortic pressure elevated in SMS?
No
What is right ventricular failure due to?
Increased pulmonary hy[ertension
When does chronic mountain sickness occur?
Long term residents at high altitude (middle age)
What are 2 characteristics of chronic mountain sickness?
Progressive increase in PVR leading to RVF
Increase in Hct
What happens in sensitive individuals at high altitude?
Hypoxia alone without lung disease can cause fatal pulmonary hypertension
What lung disease could be at risk of PVF?
COPD
What is the MoA of long-term oxygen therapy?
Supplemental oxygen for ~18hrs
Increases inhaled oxygen to get PaO2 above 90%
When is long term oxygen therapy given?
Patients with COPD
Which group was PVR substantially lower, NOT or COT?
COT - indicates that in COPD correcting oxygen brings down hypertension
Is hypoxic pulmonary hypertension part of the story in pulmonary hypertension in COPD?
Yes
Does long term oxygen therapy increase survival rate?
Yes
