Basic - Respiratory Flashcards
Why does smoking cause the hgb dissociation curve to shift leftward?
Cigarette smoke contains carbon monoxide
- high affinity for hgb
- Reduces 2,3 DPG
_____ blocks commonly cause ipsilateral phrenic n block, but is not associated with significant reduction in FRC if pt has otherwise normal pulmonary function
Interscalene block
*FRC is = to ?
ERV + RV
or
TLC - (IRV + TV)
what is closing capacity?
The volume in the lungs during expiration when the alveoli BEGIN to close
RV (residual volume) + CV (closing volume)
Why is FRC reduced in morbidly obese pts?
d/t decrease in ERV
During forced exhalation, which part of the lung is emptied first? Airway closure occurs where first?
Lung apices - emptied first
Lung bases - closes first
Lung resistance comprises of what 2 things?
Airway resistance
and
Elastic resistance
______ resistance affects airflow into the lungs.
- Peak inspiratory pressure (PIP) directly varies with flow resistance.
Airway resistance
______ measures resistance from the ventilator tubing to the segmental bronchi.
Peak inspiratory pressure (PIP)
______ resistance affects expansion of the lungs. Can be thought of as pulmonary compliance
- can affect both Peak inspiratory pressure (PIP) and plateau pressure (Pplateau)
Elastic resistance
Situations that increase airway resistance will increase _____ on the ventilator. Examples include ___
Peak inspiratory pressure (PIP)
- bronchospasm
- kinked ETT
- mucus plug
- airway secretions
*Pplateau unchanged
Situations that increase elastic resistance (or decrease compliance) will increase _____ on the ventilator. Examples include ___
PIP and Pplateau
- PTX
- PNA
- Pulm edema
- Abdominal insufflation
- Tburg
- Obesity
- ILD
When does the greatest decrease in FRC occur?
Going from 60 degrees to totally supine 0 degrees
(True/False) there is a significant decrease in FRC when changing from zero degrees to Tburg up to -30 degrees
False
unless you’re going past -30 degrees, theres no sig drop in FRC
FRC is directly proportional to ____, and is reduced by __% in females.
height
10%
How does positioning affect closing capacity?
it doesnt.
Factors that affect closing capacity
- COPD
- CHF
- Smoking
- Ongoing Surgery
- Age
*all alter transpulmonary pressure across airways, resulting in easier airway collapse at higher lung volume
Pressure vs Volume control
- Triangle wave
- Square wave
- Triangle wave: volume control
- Square wave: pressure control
What is the mechanism behind auto-PEEP or intrinsic PEEP?
the Alveolar pressure remains positive at end-expiration
- Lungs are unable to empty at end of exhalation and next breath starts
- worsens gas exchange
Why are COPD pts at increased risk for breath stacking?
Loss of elements that keep the lungs open during expiration
After smoking cessation, how long is mucocilliary function worsened?
2 weeks
- inc sputum production
deadspace vs intrapulmonary shunt
- what is it?
- which one is compromised in tburg?
deadspace: ventilation w/o perfusion
intrapulmonary shunt: perfusion w/o ventilation
*shunt is increased in t burg, no effect on deadspace
central sleep apnea vs obstructive sleep apnea?
CSA:
- brain respiratory centers do no function properly during sleep
- Fail to trigger inhalation
- apnea > 10s, >10x/hour
OSA:
- brain fxn fine
- snoring common
Overtime, why do pts with OSA develop CSA (mixed sleep apnea)?
d/t heart failure caused by OSA
- Hypoxia/hypercapnea -> pulm HTN -> RVH -> RVF
Pulmonary vascular resistance increases at (high/low) lung volumes. Why?
Both
PVR increases at low lung volumes d/t:
- as alveoli size decrease (and collapse), the geometry of pulmonary vessels surrounding alveoli bcome kinks -> resistance to flow
- as lung volume decrease below nl, volume of blood in the larger pulmonary vessels dec. -> dec vessel radius -> inc resistance to flow
Tense abdominal ascites causes a (restrictive/obstructive) lung disease pattern
Restrictive
- FEV1/FVC: normal (both are reduced)
what is vital capacity?
The maximal amt of air that can fill the lungs and participate in gas exchange
In restrictive lung disease, what spirometric patterns are decreased?
Forced vital capacity (FVC) - amt of gas that can be forcefully and maximally exhaled from a maximal inhaled vol FEV1 FRC TLC
*- proportional decrease in all lung volumes
Pts with (obstructive/restrictive) lung diseases present with low FEV1/FVC
Obstructive
- Decreased FEV1: airway collapse with forced exhalation
- FVC: inc or unchanged
In restrictive lung disease, what happens to FEV1/FVC?
Normal
- proportional decrease in all lung volumes
Bronchospasm is (smooth/skeletal) muscle mediated
smooth muscle
- Skeletal muscle relaxants have no effect
Ways to manage bronchospasm preoperatively
- Pretreat with corticosteroids days prior
- Topical lidocaine
- Albuterol
For respiratory acidosis, the pH will decrease by ___ for every acute _____ increase in PaCO2.
0.05
10mmHg
in respiratory acidosis, Bicarbonate will increase ___ and ____ for every 10 mmHg acute and chronic increase in PaCO2
*shortcut fashion
acute: 1 mEq/L
chronic: 4-5 mEq/L
Most common cause of shunt in perioperative period?
Atelectasis
Pulmonary shunt is (increased/decreased) by increasing oxygen concentrations
Increased
- leads to blunting of hypoxic pulmonary vasoconstriction and microatelectasis
Which is always higher, PaCO2 or ETCO2?
PaCO2
- spontaneously breathing: 2-5 mmHg higher
- ventilated: 5-10mmHg higher
What contributes to the difference btwn PaCO2 and ETCO2?
dead space ventilation
- decreased cardiac output causing decreased lung perfusion
- decreased lung perfusion
- inc in regional lung ventilation
- cardiogenic shock
- PE
- overinflation during PPV
- High PEEP
- R->L intracardiac shunt
- Esophageal intubation
The lung receive innervation from the sympathetic system via ___.
T2-T7
Parasympathetic system via vagal efferent and afferent nerves
ABG of pt w/ severe CO poisoning?
Metabolic acidosis
- nl PaO2
- Falsely elevated SaO2
How does Deadspace change with positioning? Neck positioning?
Upright: increase
- apex of lungs are essentially non-perfused d/t gravity
Supine: decrease
Extension: increase
Flexion: decrease
- deadspace: ventilation w/o perfusion
- portion of lung not involved in perfusion (therefore, not involved in gas exchange)
Common causes of increased deadspace (5)
- Anticholinergics
- Bronchodilators
- Increase pulmonary vascular resistance (emphysema and COPD)
- Positioning (supine, neck extension)
- Decreased Cardiac output
In ACUTE respiratory acidosis, Bicarbonate will increase ____ for every 1 mmHg increase in PaCO2 above 40 mmHg and increase ____ for every 10 mmHg increase in PaCO2
0.2 mmol/L
2 mmol/L
In CHRONIC respiratory acidosis, Bicarbonate will increase ____ for every 1 mmHg increase in PaCO2 above 40 mmHg, and increase ____ for every 10 mmHg increase in PaCO2
0.4 mmol/L
4 mmol/L
Arterial oxygen content (CaO2) equation
CaO2 = (Hgb * 1.36 * SaO2) + (0.003 * PaO2)
SaO2 = % hgb saturated with O2, nl = 95%
Commonly observed capnography in pts with COPD who received single lung transplant
Double Peak
- Difference btwn healthy transplanted lung, and diseased native lung
- First peak: rapid exhalation of healthy, transplanted lung
- Second peak: slower rate of rise of exhaled CO2 from diseased, obstructed lung
Trace nl capnogram in your head
Phase 1-2:
- Beginning of expiration
Phase 2-3:
- Early expiration
Phase 3-4:
- expiratory alveolar plateau
- continued exhalation of CO2 from lung alveoli
Phase 4-1: sharp downstroke
- inspiration
For respiratory alkalosis, for every 10mmHg decrease in PCO2, HCO3- decreases by ___ (acute), or ___ (chronic)
2
4
For respiratory acidosis, for every 10mmHg increase in PCO2, HCO3- increases by ___ (acute), or ___ (chronic)
1
4
Impairment of airflow during the EXPIRATORY phase is a result of a variable ______ airway obstruction or ____
INTRAthoracic
- distal tracheal tumor
- mediastinal mass
- below vocal cords
COPD
Impairment of airflow during the INHALATIONAL phase is a result of a variable ______ airway obstruction
EXTRAthoracic
- above vocal cords
- vocal cord paralysis
- glottic stricture
- proximal t
in pts having acute bronchospasm under GA, first line medical treatment:
beta agonist
- albuterol
Why are infants prone to bradycardia during laryngoscopy and intubation?
d/t predominance of parasympathetic nervous system
What does intubation with PEEP do to CVP, PAP, CI, and PCWP?
Increase CVP, PAP, and CI
Decrease PCWP (indirect estimate of LAP)
- increasing RV afterload
- decreasing LV afterload
Obese individuals have decreased FRC (ERV + RV), which is reduced most?
ERV
- leading to decrease in lung compliance, airway closure, and decreased PaO2
*RV is preserved
Why is morphine and atracurium not the safest choice in pts with asthma?
associated with histamine release -> induces bronchospasm
Treatment for bronchospasm if you can ventilate? What if you cant?
Can: Deepen anesthetic, inhaled B2 agonist, inhaled anticholinergics
Cant: IV epi, subQ terbutaline
- Mast cell stabilizer
- strong B2-agonist activity
Summary of Respiratory system changes with aging: (6)
- Decreased vital capacity
- Increased residual volume
- Increased closing capacity
- Increased anatomic dead space
- Increased lung compliance
- Increased pulmonary vascular resistance
Why does hyperventilation lower extracellular K levels?
Hyperventilation -> lower plasma CO2 levels -> L shift in bicarb buffer system -> lowers H+ [ ] -> K+ shifts intracellularly to maintain electrical neutrality
How does Na affect MAC requirements?
Hypernatremia increases MAC req
Hyponatremia decreases MAC req
Oxygenation is solely dependent on _____ during apnea
FRC
Oxygen consumption in an adult is ____ mL/kg
FRC in adult _____
3-4 mL/kg/min (adults)
7-8 (kids)
30 mL/kg
FGF must be equal to _______ to prevent rebreathing in the Mapelson A circuit.
FGF must be equal to _______ to prevent rebreathing in the Mapelson D,E,F circuit.
minute ventilation
2-3x minute ventilation
