Intro to Pulmonology

Question 1

What is the function of the lungs and what does this function require?

Answer 1

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

Question 2

Alveolar Circulation: structure and function

Answer 2

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

Question 3

Pulmonary Arteries

Answer 3

transport de-oxygenated blood away from the heart to the lungs

Question 4

Pulmonary Veins

Answer 4

transport oxygenated blood to the heart from the lungs

Question 5

Many pulmonary illnesses area a result of …

Answer 5

right heart failure

most pulmonary hypertension is secondary to right heart problems

Question 6

Alveolar-Capillary Barrier

Answer 6

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

Question 7

Alveolar Epithelium is made up of what two types of cells?

Answer 7

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

Question 8

Diffusion Capacity (DLCO)

Answer 8

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

Question 9

Alveolar-Arterial Gradient (A-A Gradient)

Answer 9

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

Question 10

Pulmonary Shunting

Answer 10

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

Question 11

Hypoxic Pulmonary Vasoconstriction

Answer 11

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

Question 12

Symptoms of Pulmonary Disease

Answer 12

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

Question 13

Common Pulmonary Illness Triggers

Answer 13

smoke, exertion, infection, dust, fumes, pollen, hot/cold air, pet dander

Question 14

Obstructive Lung Disease

Answer 14

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

Question 15

Restrictive Lung Disease

Answer 15

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

Question 16

What fraction of air actually reaches alveoli?

Answer 16

2/3; the other 1/3 stays in conducting airways, or dead space

Question 17

A person’s Pulmonary Function Tests are compared to others of similar…..

Answer 17

age, height, gender, and ethnicity

Question 18

Total Lung Capacity (TLC)

Answer 18

the total amount of air that the lungs can hold

VC + RV

Question 19

Tidal Volume (VT)

Answer 19

volume of air exhaled during normal quiet breathing

Question 20

Inspiratory Reserve Volume (IRV)

Answer 20

max volume of air inhaled above VT

Question 21

Expiratory Reserve Volume (ERV)

Answer 21

max air exhaled beyond VT

Question 22

Residual Volume (RV)

Answer 22

leftover air in lungs; not all is exhaled; cannot be measured with spirometry

Question 23

Vital Capacity

Answer 23

max amount of exhaled air after max inhale

IRV + VT + ERV

Question 24

Forced Vital Capacity (FVC)

Answer 24

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

Question 25

Forced Expiration Volume in 1 Second (FEV1)

Answer 25

amount exhaled in second; should be at least 80%

affected by problems with small airways

Question 26

Importance of Nitrogen Content in Air

Answer 26

nitrogen makes up 78%; if it were not present, oxygen would quickly be absorbed in the capillaries and the alveoli would collapse

Question 27

Oxygen Saturation

Answer 27

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%

Question 28

Cyanosis

Answer 28

bluish hue to hypoxic tissue; late presentation (67% arterial O2 stat)

Question 29

Hypoxemia

Answer 29

low partial pressure of O2 in the blood

Question 30

Hypoxia

Answer 30

insufficient oxygen delivery to tissues

functional part of hypoxemia

Question 31

Adequate breathing requires both …

Answer 31

oxygenation and ventilation

Question 32

Oxygenation

Answer 32

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)

Question 33

Positive End Expiratory Pressure (PEEP)

Answer 33

increases pressure within alveoli, amount of pressure used to keep airway open

used in critical care especially

Question 34

Ventilation

Answer 34

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

Question 35

Arterial Blood Gas (ABG)

Answer 35

arterial pH, PaCO2, bicarb

usually drawn from artery at wrist – must be an artery

determines cause of acid/base imbalance (respirator vs. metabolic)

Question 36

Acid/Base Balance

Answer 36

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

Question 37

Ketoacidosis

Answer 37

due to excessive ketone production (Type 1 DM, starvation)

fails to put glucose into cell (no insulin); start to rely on ketones, creating acid

Question 38

Lactic Acidosis

Answer 38

due to marked tissue hypoperfusion or hypoxia (medication, muscle breakdown, toxins)

Question 39

How would GI illnesses affect the acid/base balance?

Answer 39

excessive vomiting (causes alkalosis); diarrhea (causes acidosis)

Question 40

Waveform Capnography (PETCO2, ETCO2)

Answer 40

measurement and graphical display of end-tidal carbon dioxide; real-time reflection of patient’s ventilation

Question 41

Chest X-Ray

Answer 41

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

Question 42

CT Scan

Answer 42

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

Question 43

• Ventilation Perfusion Scan (V/Q Scan)

Answer 43

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

Question 44

Flexible Bronchoscopy

Answer 44

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)

Question 45

What lab values indicate air trapping?

Answer 45

increased TLC and RV