M2 Pulmonary Week 1 - Key Facts Flashcards
3 Major Medullary Controls of Inspiration
Dorsal Resp. Group (DRG) - Inspiration
Ventral Resp. Group (VRG) - Inspiration + Expiration
Pre-Botzinger Complex - Rhythm
Muscles of Inspiration (3) + Expiration (2)
Inspiration - Diaphragm + SCM + External Intercostals
Expiration (Normally Passive) - Internal Intercostals + Rectus Abdominis
Major Respiratory Chemoreceptors (3) - Location + Detection
Carotid Chemoreceptors - CN IX
Aortic Body Chemoreceptors - CN X
Central Chemoreceptors - Medulla
Central only respond to CO2/pH
Peripheral - CO2 still biggest player
Small + Large Vessel Response to Inspiration
Small - Alveoli open - compresses the vessels resulting in “holding” of blood to allow better gas exchange
Large - Inspiration causes dilation and an overall increase in total flow to/from the lungs
Receptors for Bronchodilation and Constriction
Dilation - B2
Constriction - M3
Physiologic Hypoxic Vasoconstriction - Key Pathway
Alveolar hypoxia –> Impedes K+ smooth muscle K+ channels resulting in more intracellular Ca2+ and vasoconstriction - Reduces flow to under-ventilated regions
Perfusion Limitation vs. Diffusion Limitation
Perfusion Limitation = Flow to the lungs all blood leaves fully oxygenated (in capillaries for 75ms but only needs 25ms)
Diffusion Limitation = Blood is not oxygenated due to increased time for diffusion (takes 60ms instead of 25ms) - Increased flow rate with exercise = hypoxemia + dyspnea
Diffusion Limitation Causes - Fibrosis = Inflammation + Mucus + Edema
Oxyhemoglobin Dissociation Curve - Causes of Right Shift (6) + Left Shift (6)
Right Shift - BAT Ace - BPG (2,3) + Altitude (High) + Temp (High) + Acidosis (Low pH) + CO2 (High) + Exercise
Left Shift - Main = Fetal Hb
Also - Low BPG, Temp, and CO2 (High pH)
Compliance vs. Elasticity + Associated Disease
Compliance - Change in Volume/Change in Pressure
Distensibility/Ability to Inflate/Opposite of Stiff
Lost in Restrictive Lung Disease
Elasticity - Opposite of compliance = ability to recoil/snap back
Lost in Obstructive Lung Disease
Anatomical vs. Physiological Dead Space
Anatomical - Volume in conducting airway that does not reach respiratory broncioles - No Gas Exchange - Approx 150ml of 500 ml tidal volume
Physiological - Total volume that does not participate in in gas exchange - Includes functional dead space (ventilated alveoli that do not participate in gas exchange)
Physiological Dead Space Calculation + Normal Value
Dead Space = Tidal Volume * [(PaCO2 - PECO2) / PaCO2]
PaCO2 = Arterial
PECO2 = Expired CO2
Normal Person (with V/Q Matching) - Expired CO2 = 40 mmHg just like PaCO2 = Limited/No Dead Space CO2 used due to rapid diffusion - If the blood gets to the ventilated area it should diffuse
Alveolar Minute Ventilation Calculation
Minute Ventilation = RR * (VT - VD)
RR = Resp. Rate
VT = Tidal Volume
VD = Dead Space
Minute Ventilation = RR * VT
Perfusion Matching in Ventilation - Dehydrated Patient - 2 Keys
Dehydrated Patient = Low volume = decreased apex perfusion
Mechanical Ventilation supplies high ventilation to apex - no flow to balance = high arterial CO2 from increased dead space
Alveolar Gas Equation
PAO2 = FIO2 * ( PATM - 47) - PaCO2 / 0.8
Simplified = PAO2 = 0.21 * (760 - 47) - PaCO2 * 1.25
A-a Gradient - Equation + Normal Range + Indication
A-a = PAO2 - PaO2 - Normal = 100 - 95
Normal Range = 5-15 —– 30 = Definitely Pathology
Hypoxemia with normal A-a = Issue with getting air to the ventilation zone = Not primary lung disease
Hypoxemia with abnormal A-a = Issue with diffusion = Primary Lung Disease
Pathologies Causing Abnormal A-a (3) vs. Pathologies with Normal A-a (3)
Abnormal A-a
1) V/Q Mismatch (Responds to supplemental O2) - Either ventilation without perfusion (PE) or vice-versa (Asthma, Lobar Pneumonia)
2) Pathological Shunting (Does not respond to O2)
3) Diffusion Block - E.g. Exercise (speed up flow) + Pulmonary Fibrosis (to thick)
Normal A-a
1) Low PO2 of Inspired Air - High Altitude
2) Alveolar Hypoventilation - High PaCO2 - Not moving out enough CO2 so it stays in the lungs and prevents O2 from entering
3) Sedation/Muscle Issues
Major Lung Volumes (4) and Capacities (4)
Volumes IRV = Inspiratory Reserve Volume TV = Tidal Volume ERV = Expiratory Reserve Volume RV = Residual Volume
Capacities
IC = Inspiratory Capacity = IRV + TV
FRC = Functional Residual Capacity = ERV + RV
TLC = Total Lung Capacity = IRV + TV + ERV + RV = IC + FRC
VC = Vital Capacity = IRV + TV + ERV = TLC - RV
FVC vs. FEV1 + Ratio - Description + Pathological Changes (2)
FVC = Maximal Exertional VC FEV1 = Maximal Expiration in 1 Second - Normal 80%
FEV1/FVC Ratio - How much of your maximal capacity can you blow out in 1 second?
Normal = 4L of 5L = 80%
Obstructive Disease = Air Trapped in + Can’t Exhale - Low Ratio + High RV + TLC
Restrictive Disease = Everything Decreased Proportional = Normal Ratio
3 Major Classes of Disease with Reduced Diffusion Capacity
1) Obstructive - CF + Emphysema
2) Interstitial Lung Disease (Restrictive)
3) Pulmonary Vascular Disease (Endothelial Damage)
Hypoxemia vs. Hypoxia
Hypoxemia = Low Arterial Oxygen = Free Oxygen - Can't tell how much is in blood (Hb) Hypoxia = Low Oxygen Delivery = More broad (e.g. low cardiac output)
Central vs. Peripheral Cyanosis - Causes
Central
Bluish discolaration of the lips + tongue - Can be warm and well perfused
Causes - Diseaes of Heart/Lung/Hb
Peripheral
Decreased circulation + increased O2 extraction
Causes - CHF + Shock + Raynaud’s + Cold
Example of Tachypnea with no Dyspnea
Acidosis - Breathing hard to get rid of CO2
Four Classes of Diseases Causing Dyspnea + Examples
Structural/Mechanical - Asthma, Chronic Bronchitis etc.
Restriction of Lung Wall - Can’t expand
Intrinsic - Parenchyma (CHF/ARDS)
Extrinsic - Obesity, Ascities, Pregnancy etc.
Increased Dead Space - PE + Emphysema
Increased Respiratory Drive - Hypoxemia = Acidosis + Exercise + Reduced CO/Hb
Cough Pathway + Sensitization + Stimulants (5)
Cough receptors stimulated –> Vagus Nerve –> Nucleus Tractussolitariusof the Medulla –> Effect Response
Causes
1) Cigarette Smoke2
2) Pulmonary Congestion
3) Atelectasis
4) Low Compliance
5) GERD (Stomach Cough Receptors)
Sensitization - Bradykinin/Substance P from inflmmation - Reduces threshold of cough receptors