Respiratory Final Flashcards
What are high risk results from PFT’s?
FEV1 < 2L
FEV1/FVC ratio < 0.5%
VC adults < 15cc/kg/ child <10cc/kg
VC < 40-50% of predicted value
What are post operative extubation criteria?
- VSS, awake, alert, RR < 35
- On 40% FiO2, PaO2 > 70mmHg , PaCO2 < 55
- MIF MORE than -20 cmH2O
- VC > 15cc/kg
MECHANICAL intubation criteria?
- RR > 35,
- VC <15cc/kg adult, VC , 10cc/kg child
- MIF LESS negative than -20 cmH2O
OXYGENATION intubation criteria?
- 40% FiO2, PaO2 < 70mmHg
- A-a gradient > 350mmHg on 100% O2
VENTILATION intubation criteria?
- PaCO2 > 55 ( except chronic hypercarbia/COPD)
- Vd/Vt > 0.6 ( 30% anatomical dead space)
CLINICAL intubation criteria ?
- Airway burn
- Chemical Burn
- Epiglottis ( usually small children)
- Altered Mental Status
- Rapidly declining pulmonary function
- Fatigue ( common in elderly)
What are your normal ABG values?
pH: 7.35 – 7.45 PCO2: 35 – 45 mmHg PO2: 75 – 105 mmHg Bicarbonate: 20 – 26 mmoles/L Base excess: -3 to +3 mmoles/L
What does an increasing or decreasing CO2 by 10mmHg do to your pH?
Inversely decreases or increases by 0.08
What is hypoxemia?
Decreased BLOOD PO2 < 75
What is hypoxia?
A low O2 state.
What is the A-a gradient?
Measures lung efficiency
What is the equation for PAO2?
= (PB - PH2O) x (FiO2) - ( PaCO2/0.8)
What is a roughly a normal A-a gradient?
Age/3
- Should be less than 20mmHg difference
When is the A-a gradient widened?
V/Q mismatch Pneumothorax Shunt PE Diffusion Issues
T/F: The A-a gradient normal with hypoventilation and low FiO2?
TRUE
How do you manage an abnormal A-a gradient?
Treat underlying cause
- Supplemental O2
- Adjust ventilation
- add PEEP
- Treat atelectasis
What equation is bicarbonate calculated from?
H= 24 x ( PaCO2/ HCO3)
An increase or decrease in bicarb by 10mmoles does what to your pH?
A directly proportionate increase and decrease by 0.15
What is the equation for TOTAL body bicarb deficit?
deficit = base deficit x weight in kg x 0.4 = in mEq/L
How much total body bicarb deficit do you replace?
replace 1/2 the deficit
Respiratory acidosis, an acute cause?
- Hypoventilation with Hypercarbia ( opioids)
- CNS depression – trauma, drugs
- Decreased FRC – obesity ( osa)
- Upper or lower airway obstruction
Chronic cause of respiratory acidosis?
- COPD
- Emphysema
- Asthma
How does the Body compensate for respiratory acidosis?
1-2 Days KIDNEYS compensate increasing H+ excretions and increase HCO3 being absorbed into the blood.
= increasing HCO3 value, and PARTIALLY restoring pH
What are causes of respiratory alkalosis?
Hyperventilation with Hypocarbia
- -PRENANCY
- -Anxiety
- -Hypoxic respiration ( mountain climbing )
- Artificial ventilation
- -CNS disorders
- -Encephalitis
- -Narcotic Withdraw
- -Early septic shock
- -Hypermetabolic states
How does the body compensate for respiratory alkalosis?
Kidneys increase HCO3 excretion and retain H+ = partially correcting pH and resulting in a lower HCO3
What are causes of metabolic acidosis?
- Trauma ( hypoperfusion) = Lactic acidosis
- DKA
- ASA ingestion
- High protein intake
- Diarrhea ( losing HCO3)
How does the body compensate for metabolic acidosis?
-Respiratory ( central chemoreceptors) with HYPOCARBIA
- More rapid than renal compensation
-Eventual H+ excretion from the kidneys
= lowering CO2 and partially correcting pH
What are causes of metabolic alkalosis?
- Bicarb over infusion
- Vomiting or excessive NG suction ( H+ loss)
Compensation for metabolic acidosis?
Respiratory compensation –>hyperventilate,
-However hypoventilation is limited due to eventual hypoxic drive
= increasing CO2 retention and partial correction in pH
T/F: Pulse oximetry is a mandatory intraoperative monitor?
True
Infrared light represents what? and is measured at what wavelength?
Oxyhemoglobin - 940nm
Corresponds with 100% saturation
Red light represents what? and is measured at what wavelength?
Deoxygenated hemoglobin and 660 nm
-Corresponds to 50% saturation
Hemoglobin variants
Describe carboxyhemoglobin
From CO2 poisoning, is viewed as oxyhemoglobin by the pulse ox and shows up as 100%
-This is an overestimation of the true oxygenation, co oximeter used to distinguish between the two
What happens in Methemoglobin ?
Fe2 in Hb is oxidized to Fe3 and cannot transport O2, cyanosis seen when 15% of Hg is in methemoglobin form
**Absorbs equally at both wavelengths 1:1 shows an SpO2 of 85%
What causes Methemoglobin ?
- Nitrates
- Nitrites
- Nitroglycerine
- Nitroprusside
- Sulfonamides
- Benzocaine ( hurricane spray)
How do we treat Methemoglobin?
Low does methylene blue
-Ascorbic acid
What two things do not affect the pulse oximetry?
Fetal Hemoglobin and bilirubin
Capnograhy: Rapidly and reliably indicates _____ intubation but does not reliably detect ______ intubation
Esophageal
Endobronchial
What is the gold standard for tracheal intubation
End-tidal CO2
During surgery where a pt is in the lateral position, which long will be better ventilated? Is this a problem?
The nondependent lung will be better ventilated but the dependent lung will be better perfused causing a V/Q mismatch.
In the ____ and ____ position the dependent lung is better perfused (gravity) and ventilated
Awake & Lateral
Positive pressure ventilation favors the upper or lower lung and why?
The upper lung because it is more compliant.
T/F: The upper lung is favored.
True
T/F: Hypoxic pulmonary vasoconstriction improves a the right-to-left shunt.
True
Factors that inhibit hypoxic pulmonary vasoconstriction.
- Very high or very low pulmonary artery pressure
- Hypocapnia
- High or low mixed venous PO2
- Vasodilators (NTG, Nitroprusside, Beta-adrenergic agonist, calcium channel blockers)
- Pulmonary infections
- Inhalation agents.
During OLV what should your FiO2 be?
80-100%
Tidal Volumes should be kept at ______ during OLV.
10cc/kg
How do you ensure placement during OLV?
Fiberoptic scope
Add ___ of CPAP to nondependent lung and add ___ PEEP to dependent lung
5cm H2O for both
Malignant Hyperthermia is triggered by what?
Inhalation agents (not N2O), and/or succinylcholine.
Malignant Hyperthermia leads to an acute __________ state
Hypermetabolic
T/F: The ryanodine receptor (Ca release channel) fails in the sarcoplasmic reticulum leasing to decrease in Ca reuptake
True. This causes increase intracellular Ca leading to sustained muscle contraction, glycolysis, and heat production.
Malignant Hyperthermia has abnormal excitation-contraction coupling which results in what?
Prolonged and irreversible muscle contracture
What is the first most sensitive sign of MH?
Unexplained tachycardia
What is the most specific sign of MH?
Increase EtCO2- hypercapnia. Also decrease in SaO2 and SpO2.
What are the signs and symptoms of MH?
Muscle rigidity, dysrhythmias, tachypnea, cyanosis, sweating, unstable BP, mottling, trismus (masseter spasm), cola-colored urine, hyperthermia (least sensitive sign)
What would labs looks like in MH?
Metabolic Acidosis then a combined metabolic respiratory acidosis, hyperkalemia, hypercalcemia, hyperphosphatemia, creatinine kinase (CK) >1000 IU, myoglobinuria, hypoxemia
What is diffusion hypoxia?
This results from the dilution of alveolar O2 concentration by a large amount of N2O “outgasing” or leaving the pulmonary capillary blood at the conclusion of N2O administration.
How do you avoid diffusion hypoxia?
Administering 100% O2 following N2O use.
Factors that increase MAC
- *Age: term infant to 6 months of age has the highest MAC requirements
- Hyperthermia
- *Chronic EtOH abuse
- Hypernatremia
- Drugs that increase CNS catecholamine.
Factors that decrease MAC
- Hyperthermia
- IV anesthetics, opioids,
- Preop Meds
- Neonate/Premature infants
- Elderly
- *Pregnancy
- Acute EtOH ingestion
- Lithium
- Cardiopulmonary Bypass
- Hyponatremia
- Alpha 2 agonist (precede)
- Calcium Channel Blockers
- Severe Hypoxemia (PaO2 <38mmHg)
Factors that have no effect on MAC
- *Thyroid gland dysfunction
- Gender
- Hyper/Hypokalemia
- Hyper/hypocarbia
What is the second gas effect?
The ability of a large volume uptake of a first gas (N2O) to accelerate the rate of rises of the alveolar partial pressure of a concurrently administered companion gas (agent) thus speeding induction).
What is an example of the second gas effect?
Alveolar space: 70% N2O, 30% O2 and ISO 1% -> rapid uptake of 1/2 of the N2O -> 35% O2, and ISO now 1.53%
Nicotine stimulates sympathetic ganglia, which releases ________ from the ________ ________ and causes an increase in what?
Releases catecholamines from the adrenal medulla, increasing HR, BP, and SVR. This persists for 30 minutes after last cigarette.
25 pack per year increases physiologic age by how many years?
8 years