ICL 2.1: Fixed Obstructive Lung Disease: COPD and Bronchiectasis Flashcards
what is COPD?
a persistent respiratory symptoms and fixed airflow limitation that is due to both airway and/or alveolar abnormalities
usually caused by significant exposure to noxious particles or gases; especially cigarette smoke
a common, preventable and treatable disease
what are the causes of COPD?
- cigarette smoking
- biomass fuel used in cooking
- genetic predisposition
- SE status
what is the prevalence of COPD?
3rd leading cause of death in the US
leading cause of morbidity and mortality worldwide
prevalence is projected to increase in coming decades to do increased exposure to risk actors and population aging
what is the pathogenesis of COPD?
enhancement of the normal physiological inflammatory response of the respiratory tract to chronic irritants
primarily TH1/neotrophil and macrophage inflammation in comparison to asthma which is primarily tH2/eosinophil/mast cell inflammation
mechanisms for amplified inflammation in the 10-15% of heavy smokers who develop COPD is not understood
lung inflammation persists after smoking cessation and defective airway clearance allows nasal bacterial flora to colonize airways which exacerbate inflammation = pneumococcus, H. influenza, M. catarrhalis
what is the pathophysiology of COPD?
- airflow limitation
- gas trapping
- hyperinflation
narrowing of peripheral airways is due to inflammation and irritation plus reduced elastic recoil due to parenchymal destruction
- hypoxia and hypercapnia due to V/Q mismatch
- mucus hyper secretion due to increased number of goblet cells and enlarged submucosal glands in response to chronic airway irritation
- pulmonary HTN due to hypoxic vasoconstriction of small arteries
what is the pathophysiologic cause of air trapping seen with COPD?
air trapping in alveoli is caused by collapse of small airways, not the alveoli themselves
breakdown of alveoli connections to adjacent small airways removes support necessary to prevent early collapse during exhalation
what is the effect of increased airway resistance/obstruction on breathing seen in COPD?
- sharply reduced effort-independent air flow at high volume than in normal
- air is trapped in alveoli due to slow flow resulting from obstruction during end expiration
air trapping raises alveolar pressure and trans pulmonary pressure which causes the diaphragm to become flattened and it’s no longer able to generate inspiratory pressures high enough to overwhelm the transpulmonary pressure
reduced function of the diaphragm and high lung pressures increase the work of breathing…
when should you be suspicious that someone has COPD?
- dyspnea
- chronic cough or sputum production
- h/o exposure to risk factors
how do you diagnose COPD?
spirometry is REQUIRED to make the diagnosis
post-bronchodilator FEV1/FVC < 0.70 confirms fixed airflow limitation = COPD
which of the following is correct regarding altered mechanism of breathing in COPD?
A. collapse of alveoli at higher than normal lung volumes is associated with air trapping and hyperinflation
B. increased alveolar elastic recoil is associated with collapse of small airways at higher lung volumes
C. an FEV1/FVC of 0.8 is consistent with COPD
D. an FEV1/FVC of .5 prior to bronchodilator is consistent with COPD
A. collapse of alveoli at higher than normal lung volumes is associated with air trapping and hyperinflation
how do you diagnose chronic bronchitis?
mostly history based:
- productive cough that lasts at least 3 months over a period of at least 2 years
- polycythemia = increased RBCs
- hypxemia which leads to increased EPO levels
so you diagnose COPD based on FEB1/FVC > 0.7 first and then you specifically diagnose chronic bronchitis in a COPD patient based on their history of a cough for 2+ years
how do you diagnose emphysema?
based on structural changes:
- CXR ro CT which shows: enlargement or air oscar, increased AP diameter, flattened diaphragm, increased lung field lucency
- DLCO: decreased lung diffusing capacity secondary to alveolar wall destruction
- decreased alpha-1 antitrypsin
so you diagnose COPD based on FEV1/FVC < 0.7 first and then you diagnose emphysema specifically based on imaging showing structural changes
which of the following is correct regarding chronic bronchitis and emphysema sub-types of COPD?
A. CPD and chronic bronchitis are each diagnosed based on a combination of history, PE, PFT, and imaging
B. each COPD patient has primarily either chronic bronchitis or COPD, not a combination of both
C. in patients with FEV1/FVC below 0.7, a consistent history is what provides diagnosis of chronic bronchitis
D. the key determinant of whether a COPD patient is a blue bloater or pink puffer is the degree of obstruction
C. in patients with FEV1/FVC below 0.7, a consistent history is what provides diagnosis of chronic bronchitis
what’s the difference between a blue bloater and pink puffer?
chemoreceptor sensitivity!
blue bloaters have less intense ventilatory response to CO2 resulting in hypoventilation –> as a consequence they have a high PaCO2, lower PaO2, and a higher Hb due to secondary polycythemia – they often have cor pulmonale due to chronic hypoxia vasoconstriction resulting in pulmonary HTN and subsequently lower extremity edema from CHF
punk puffers have a more intense ventilatory response to increased CO2 levels so they have proper ventilation, normal PCO2 and normal oxygen levels so they aren’t cyanotic and remain pink
chronic bronchitis has similar features to what other condition?
obstructive sleep apnea/obesity hypoventilation syndrome = Pickwickian syndrome
both of them have hypoventilation due to less sensitive response to increased CO2 levels
so they both have high PaCO2, low PaO2, and high Hb as a result of secondary polycythemia
cor pulmonale response from chronic hypoxia
