Pulm Phys & Pharm Flashcards
Alveolar pressure is the
Pressure inside of the lung
Intrapleural pressure is the
Pressure outside of the lung
Transpulmonary pressure (TPP)
The difference between:
Alveolar pressure - Intrapleural pressure
diffusion of CO2 vs O2
CO2 diffuses 20X faster than O2
Alveolar Surface tension for SPHERICAL SHAPE Equation?
Tension = Pressure x radius /2
What law describes alveolar surface tension?
Law of Laplace
What law describes the diffusion of a gas through a membrane?
Graham’s law
What law describes the greater the pressure difference (gradient), the greater the rate of diffusion?
Henry’s Law
What law describes the rate of diffusion of (O2, N2, CO2) is proportional to the partial pressure caused by each gas alone?
Dalton’s Law
What law describes lung compliance?
Boyle’s Law
-change in volume / change in pressure
V/Q ratios of upper vs lower areas of the lungs?
Upper areas of the lung have better ventilation in relation to perfusion = higher V/Q ratio
Lower levels of the lung have better perfusion than ventilation = lower V/Q
Ratio of change in volume to change in pressure
Compliance
Max pressure during the inspiratory phase time
Peak Pressure
ratio of change in driving pressure to change in flow rate
Resistance
energy expended to move gas in and out
Work of breathing
best vent settings to prevent barotrauma?
PC-VG
PS
Mechanisms of Gas exchange (3)
ventilation
perfusion
diffusion
Oxygen Content (CaO2)
= [Hb x 1.34 x Sao2%] x [Pao2 x 0.003]
Diffusion of gas is determined by: (4)
- Membrane thickness: thicker the membrane, slower the diffusion
- Surface area of the membrane: SA of lungs is massive
- Diffusion coefficient of the gas in the substance of the membrane
- the pressure difference between the two sides of the membrane.
Total body oxygen delivery is the product of?
- O2 content or arterial blood (CaO2) and
- rate of delivery of blood to the tissues (CO)
DO= CO X CaO2
CaO2= Hgb X 1.39 X SaO2 + (0.0031 X PaO2)
Define: CaO2
CaO2: oxygen content of arterial blood
Define: SaO2
SaO2: arterial oxygen saturation
Define: PaO2
PaO2: partial pressure of oxygen in arterial blood
Define the constant: 1.39
- 39
- the amount of oxygen (mL) bound to each gram (g) of hemoglobin
- (varies between 1.34-1.39)
- 1.39 mL O2 per g of Hb
Define the constant: 0.003
- 003
- solubility of O2 in plasma, amount of O2 dissolved in plasma
- dissolved O2 mL is a very small amount relative to the Hb bound O2 -(is only significant in very high PaO2 sates such as a hyperbaric chamber, or in anemia)
- mL o2 / mm Hg / 100 mL plasma
Total Oxygen consumption (VO2)
the total oxygen consumed by the tissues per minute
-Normals:
4 mL/kg/min
250 mL/min
VO2 = CO x (CaO2 - CvO2)
Total oxygen delivery (DO2)
is the total amount of oxygen delivered to the tissues per minute
-Normals:
16 mL/kg/min
1000 mL/min
DO2 = CO x CaO2
Oxygen Extraction Ratio (OEF)
The amount of oxygen consumed (VO2) as a fraction of oxygen delivery (DO2) defines the oxygen extraction ratio (OER)
-oxygen that is not extracted is returned to the mixed venous circulation
Normal: 25%-ish
OER = VO2/DO2
or
OER = CaO2 - CvO2 / CaO2
Mixed Venous Oxygen Saturation (SvO2)
% of oxygen bound to hemoglobin in blood returning to the right side of the heart. This reflects the amount of oxygen “leftover” after the tissues remove what they need.
-Normal: 65-80%
If SvO2 is 70%, it denotes tissue oxygen extraction OER to be 30%.
Causes of hypoxemia
Causes of low PaO2
- low inspired PO2
- hypoventilation
- V/Q mismatch
- R to L shunt
- diffusion impairment
Normal V/Q ratio
approximately equal to 0.8
Low V/Q:
Ventilation issues
-produces hypoxemia by decreasing the alveolar oxygen level (PAO2) and subsequently arterial oxygen level
High V/Q:
Perfusion issues
-the impact of high V/Q unit on blood oxygenation is minimal, it can cause hypoxemia if the compensatory rise in total ventilation is absent/impaired
Shunting usually causes ______ and dead space usually causes ______
hypoxemia
hypercarbia
Inspiration is impaired when there is a variable __________ obstruction
Extrathoracic obstruction
Ex: sleep apnea, incomplete NMB, vocal cord palsy
Expiration is impaired when there is a variable ___________ obstruction
Intrathoracic obstruction
Ex: bronchial tumor
Restrictive Lung Disease & FEV1/FVC
Both FEV1 and FVC are decreased bc compliance is poor
Therefore the FEV1/FVC ratio may be normal, or even increased
Obstructive Lung Disease & FEV1/FVC
FEV1/FVC ratio is decreased
Nerve associated with Laryngospasm
Superior Laryngeal N.
Post obstructive pulmonary edema (POPE)
Two types:
- Type 1: follows a sudden severe episode of upper airway obstruction
- Type 2: develops after surgical relief of chronic upper airway obstruction
-the release of obstruction causes sudden negative pressure and fast onset edema
regulation of bronchial muscle tone: SNS
- B2 adrenergic stimulators cause bronchodilation
- A1 adrenergic stimulators cause bronchoconstriction (must less effect than B2)
regulation of bronchial muscle tone: PSNS
-muscarinic Ach receptors cause bronchoconstriction
Main inhibitory transmitters responsible for airway smooth muscle relaxation?
Vasoactive intestinal peptide (VIP)
Nitric oxide (NO)
Main excitatory transmitters responsible for airway bronchoconstriction?
Substance P (SP)
Neurokinin A (NKA)
Primary Inhaled beta agonist
albuterol
Primary Inhaled Anticholinergics
Ipratropium (atrovent HFA)
- short-acting
- maintenance therapy for COPD and rescue therapy for COPD and asthma
tiotropium (Spiriva respimat)
Inhaled Corticosteroids
Budesonide (Pulmicort Flexhaler, Pulmicort Respules)
Fluticasone (Flovent HFA)
Drugs that affect Leukotrienes
- glucocorticosteroids (prednisone)
- 5-lipoxygenase antagonists (zileuton)
- LTD4 antagonists (zafirlukast)
Leukotrienes
- mediators of airway inflammation
- produced by mast cells and eosinophils and are primary mediators of bronchoconstriction and edema in asthmatic airways
- are products made from the arachidonic acid produced by phospholipase A2
LTD4 receptor antagonist
- montelukast (Singulair)
- zafirlukast (Accolate)
5-lipoxygenase Inhibitor
Zileuton (Zyflo)
Mast Cell Stabilizers / Degranulation inhibitors
Cromolyn
Nedocromil
Phosphodiesterase Inhibitors
Roflumilast
Anesthetics that cause bronchodilation
Inhaled volatiles
Ketamine
Propofol
5-Lipoxygenase inhibitors (e.g., zileuton) MOA bronchodilation
-block the synthesis of leukotrienes while CysLT 1 antagonists block the effect of leukotrienes on airway cells.
Steroids MOA bronchodilation
-nonspecifically block activation of many inflammatory cells in the airway responsible for cytokine production that alter signaling pathways of airway cells favoring edema, mucus secretion, and airway smooth muscle contraction.
B2 agonists MOA bronchodilation
-both directly relax airway smooth muscle and block activation of inflammatory cells.
Muscarinic antagonists MOA bronchodilation
-block M 3 muscarinic receptors on airway smooth muscle as well as muscarinic receptors on epithelium and nerves.
Left shift vs Right shift in oxyhemoglobin disassociation curve
Left = increased affinity (less release of O2 to tissues)
- decreased temp
- decreased 2-3 DPG
- decreased H+
- carbon monoxide
- fetal Hb
Right = decreased affinity (increased release of O2 to tissues)
- increased temp
- increased 2-3 DPG
- increased H+
- maternal Hb
- sickle cell
Alveolar Gas Equation (PaO2)
= Fio2 (Atm - H2oVP) - PaCo2 / RQ
Atm = 760
H20 VP at 37 degrees = 47
RQ ~ 0.8 (ratio of Co2 produced to that of O2 consumed VCO2/VO2)
What happens to us at altitude?
- decreased PAo2 causes decreased Pao2 (which carotid body senses, and initiates hyperventilation)
- increased MV (RR + TV)
- decreased pCo2, lowers H+ in the blood, which causes renal bicarb loss
What occurs when Ach binds to M3 receptors in the lungs?
bronchoconstriction
- bronchi and bronchioles innervated by vagus nerve, and releases Ach to Muscarinic receptors causing bronchoconstriction
treatment: ipratropium, an inhaled anticholinergic
From a pulmonary standpoint (not HR) what would happen if you reversed NMBs with neostigmine alone (without glycopyrrolate) ?
At end of cases, if you gave neostigmine alone, it would inhibit acetylcholinesterase raise Ach levels and muscarinic receptors would be activated leading to bronchoconstriction. So that is why we give glycopyrrolate along with it.
Sympathomimetic effects on the pulm system?
circulating catecholamines affect airways by activating B2 receptors and causing bronchodilation
-albuterol, epi
Histamine effects on the pulm system?
H1 stimulation causes bronchoconstriction (predominant effect of histamine)
dynamic compliance
=VT/ Peak pressure - Peep
-resistance to gas flow present in tubing , ETT, airway, lungs, or chest wall
Decreased: ETT obstruction, bronchospasm
static compliance
=VT/ Pplat-Peep
-measure of airway pressure required to hold the lungs and chest wall and end inspiration when gas flow is absent
Decreased: stiff lungs, pneumonia
What is closing capacity?
is the tidal volume in the lungs at which its smallest airways, the respiratory bronchioles collapse
can cause V/Q mismatching
Obesity effects on lung physiology
- decreased lung volumes (ERV, FRC, TLC)
- low FRC causes them to desaturate quickly with apnea
- restrictive ventilation defect (rather than obstructive), decreased FEV1 and FVC so FEV1/FVC ratio is “normal”
Classes of bronchodilator therapies?
- Beta 2 adrenergic agonists
- Anticholinergics (parasympatholytics)
- Methylxanthines (phosphodiesterase inhibitors)
- Inhaled or systemic corticosteroids
- leukotriene inhibitors
- mast cell/degranulation inhibitors
- phosphodiesterase inhibitors
Goal EtO2 during preoxygenation
> 90%
factors that decrease safe apnea time:
low FRC (obesity, pregnancy), shunt physiology, increased O2 consumption (fever), inadequate preoxygenation
Complicated airway as a result of facial and airway edema caused by angioedema can be caused by what drugs?
-ace inhibitors like lisinopril
Indications for hyperbaric oxygen
- air embolism
- CO poisoning
- cyanide poisoning
- gas gangrene
- infections/wound healing
- extreme anemia
- central retinal artery occlusion
oxygen toxicity
- high concentrations of O2 over long periods of time
- lungs, brain, eyes
lungs - tracheobronchial irritation causing cough, burning chest pain, ARDS
brain - seizures, N/V, twitching
eyes - narrowing visual fields, change in refraction (myopia)
