Intro to Pulmonology Flashcards
What is the function of the lungs and what does this function require?
maintain pO2 and pCO2 within normal physiologic range
requires:
CNS-mediated respiratory drive via the brainstem
patent airways
inspiratory muscles to create negative thoracic pressure
perfusion of lungs
gas diffusion across alveolar capillary barrier
passive expiration via elastic recoil and relaxation of diaphragm
Alveolar Circulation: structure and function
large bronchial tree ending in hundreds of millions of alveoli to increase surface area for gas exchange
there is a dense network of capillaries surrounding each alveolus; allow gas molecules to be in close proximity to capillaries, which optimizes diffusion of gases between alveolus and bloodstream
Pulmonary Arteries
transport de-oxygenated blood away from the heart to the lungs
Pulmonary Veins
transport oxygenated blood to the heart from the lungs
Many pulmonary illnesses area a result of …
right heart failure
most pulmonary hypertension is secondary to right heart problems
Alveolar-Capillary Barrier
highly permeable to molecular O2, CO2, CO, and many other gases
if too thick, gases have difficulty diffusing across barrier
this very thin layer also makes anything else that gets into the lungs readily absorbed into the bloodstream -
reason why smoking is a fast, effective way to get nicotine and other drugs into the system
Alveolar Epithelium is made up of what two types of cells?
type I pneumocytes: large flattened squamous cells; 95%
type II pneumocytes: 5%; secrete ‘surfactant’ which decreases the surface tension between the thin alveolar walls, and prevents alveolar collapse with exhalation
Diffusion Capacity (DLCO)
method to quantify gas diffusion across alveolar-capillary membrane
typically measures carbon monoxide (CO)
performed in a pulmonary function lab, requires special equipment
low DLCO indicates impaired gas transfer from alveoli to capillary blood, such as in lung resection, emphysema (do to loss of functioning alveolar-capillary units), interstitial lung disease (thickening of alveolar-capillary membrane), pulmonary vascular disease, anemia
Alveolar-Arterial Gradient (A-A Gradient)
measure of the difference between PAO2 (Alveolar) and PaO2 (arterial)
should be minimal/low
if elevated, this indicates that the lungs are not adequately getting O2 from the air and into the blood, such as in pulmonary edema, pulmonary embolism, COPD, pulmonary fibrosis, pneumonia, right to left cardiac shunting – most ‘lung diseases’
requires special blood draw
Pulmonary Shunting
pathological condition in which alveoli are perfused with blood, but not ventilated
most common cause of hypoxia
insufficient airflow (COPD, asthma, PNA)
lungs attempt to compensate with hypoxic pulmonary vasoconstriction
Hypoxic Pulmonary Vasoconstriction
the pulmonary vascular smooth muscle constricts when areas of the lung are not adequately exchanging oxygen, so that blood flow is re-routed to areas of the lung with better oxygenation
can be maladaptive and lead to secondary pulmonary arterial hypertension and eventually right heart failure if it is extensive
Symptoms of Pulmonary Disease
dyspnea/ shortness of breath/ air hunger/ exercise intolerance
cough
wheezing
others: chest pain, tightness, or heaviness; headaches, lightheadedness; fever/chills; anorexia, early satiety, weight loss; anxiety/depression
Common Pulmonary Illness Triggers
smoke, exertion, infection, dust, fumes, pollen, hot/cold air, pet dander
Obstructive Lung Disease
airways are narrowed, so stale air cannot escape the alveoli, and/or alveoli lack elasticity to fully exhale
air comes in, but can’t get out
Restrictive Lung Disease
inability to get air into the lungs, often associated with thickening of the alveolar-capillary membrane and/or there are extrinsic limitations, such as obesity or chest deformation
cannot get air in
What fraction of air actually reaches alveoli?
2/3; the other 1/3 stays in conducting airways, or dead space
A person’s Pulmonary Function Tests are compared to others of similar…..
age, height, gender, and ethnicity
Total Lung Capacity (TLC)
the total amount of air that the lungs can hold
VC + RV
Tidal Volume (VT)
volume of air exhaled during normal quiet breathing
Inspiratory Reserve Volume (IRV)
max volume of air inhaled above VT
Expiratory Reserve Volume (ERV)
max air exhaled beyond VT
Residual Volume (RV)
leftover air in lungs; not all is exhaled; cannot be measured with spirometry
Vital Capacity
max amount of exhaled air after max inhale
IRV + VT + ERV
Forced Vital Capacity (FVC)
max amount of exhale when forced
take as much breath in as you can and blow out as much as you can
taken three times for an average; 80% is considered normal
Forced Expiration Volume in 1 Second (FEV1)
amount exhaled in second; should be at least 80%
affected by problems with small airways
Importance of Nitrogen Content in Air
nitrogen makes up 78%; if it were not present, oxygen would quickly be absorbed in the capillaries and the alveoli would collapse
Oxygen Saturation
measured with spectrometry
measures what is bound to heme molecules
benefits: rapid, non-invasive, low cost, accurate within 2% of true O2 stat
limits: cannot distinguish O2 from other molecules (ex. CO); inaccurate if poor perfusion (cold hands); cannot assess ventilation (CO2); less accurate if O2 stats are below 70%
Cyanosis
bluish hue to hypoxic tissue; late presentation (67% arterial O2 stat)
Hypoxemia
low partial pressure of O2 in the blood
Hypoxia
insufficient oxygen delivery to tissues
functional part of hypoxemia
Adequate breathing requires both …
oxygenation and ventilation
Oxygenation
getting oxygen out of alveolar air into the bloodstream
can be improved by increasing oxygen contend of inhaled air (cannot be 100%) and by increasing partial pressure of oxygen (PAO2)
Positive End Expiratory Pressure (PEEP)
increases pressure within alveoli, amount of pressure used to keep airway open
used in critical care especially
Ventilation
inhaling and exhaling; delivers fresh air to alveoli and allows expulsion of stale air
CO2 regulation is essential for acid/base balance
PCO2 is increased by increasing respiratory rate and tidal volume
Arterial Blood Gas (ABG)
arterial pH, PaCO2, bicarb
usually drawn from artery at wrist – must be an artery
determines cause of acid/base imbalance (respirator vs. metabolic)
Acid/Base Balance
normal extracellular pH is 7.35-7.45; outside of this range, proteins denature, causing enzymes and ion channels to fail
acidosis <7.35 – 7.45 < alkalosis
primarily regulated by CO2 in respiration and bicarbonate in the kidneys
any acid and base in the body can also affect pH, though they typically occur in small amounts and contribute minimally in normal healthy states
Ketoacidosis
due to excessive ketone production (Type 1 DM, starvation)
fails to put glucose into cell (no insulin); start to rely on ketones, creating acid
Lactic Acidosis
due to marked tissue hypoperfusion or hypoxia (medication, muscle breakdown, toxins)
How would GI illnesses affect the acid/base balance?
excessive vomiting (causes alkalosis); diarrhea (causes acidosis)
Waveform Capnography (PETCO2, ETCO2)
measurement and graphical display of end-tidal carbon dioxide; real-time reflection of patient’s ventilation
Chest X-Ray
risk: radiation exposure (low dose)
cost: relatively inexpensive
quick, accessible
interpretation varies widely, low sensitivity/specificity
indications: Shortness of breath, Cough (severe acute, or chronic) – not mild acute upper respiratory infection (URI), Chest pain, Chest wall trauma, Chest wall deformities (kyphosis, scoliosis), Hypoxia, Foreign body aspiration
CT Scan
RISK: radiation exposure, invasive (IV contrast), side effects (extravasation, discomfort, allergy)
More expensive
IV contrast (angiography): improves view of blood vessels (r/o PE) & lymph nodes
contraindication: Allergy to iodine (consider pre-medicating), renal failure (consider pre-hydration)
cost: moderately expensive
good visualization of pulmonary parenchyma, chest structures, vessels
does not tell you about function, incidental findings are common
Common indications: symptoms unexplained by chest x-ray or repeat x-ray still abnormal; concern for pulmonary embolism (must use IV contrast); pulmonary nodules/masses, intra-airway lesions; mediastinal or hilar adenopathy (contrast recommended); loculated or unilateral pleural effusion, pleural thickening
• Ventilation Perfusion Scan (V/Q Scan)
less sensitive than CT or pulmonary angiography
indication: rule in pulmonary embolism
can be used to diagnose a PE, but a normal scan does not rule out a PE
can be used in patients with renal failure or other contraindications for IV contrast
Flexible Bronchoscopy
flexible scope is passed into bronchial tree
indication: as deemed necessary by pulmonologist, may include mass/nodule in or near a major airway, mediastinal adenopathy, non-resolving pneumonia
cost: expensive
direct visualization of airways, obtain biopsy, cultures, perform interventions
risks of anesthesia, pneumothorax, bleeding, death, can’t get into small airways; not good for peripheral airways (better for centrally located)
What lab values indicate air trapping?
increased TLC and RV
