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Physics Flashcards

1
Q

Over or underestimation of TDCO: Injectate bolus volume is greater than the programmed volume

A

Underestimation

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2
Q

Over or underestimation of TDCO: Large volume of fluid is administered during a CO reading

A

Underestimation

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3
Q

Over or underestimation of TDCO: Injectate solution’s actual temperature is colder than the preprogrammed Ti

A

Underestimation

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4
Q

Over or underestimation of TDCO: Self-measuring Ti probe is warmer than the actual injectate temperature

A

Underestimation

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5
Q

Over or underestimation of TDCO: Injectate bolus volume is less than the programmed volume

A

Overestimation

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6
Q

Over or underestimation of TDCO: Injectate solution’s actual temperature is warmer than the preprogrammed Ti

A

Overestimation

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7
Q

Over or underestimation of TDCO: Self-measuring Ti probe is colder than the actual injectate temperature

A

Overestimation

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8
Q

In order for a surgical fire to occur, all three components of the “fire triad” must be present. What are these 3 things?

A

hese include a fuel (e.g. surgical prep solution, surgical drapes, sponges, endotracheal tube, oxygen tubing), an oxidizer (e.g. oxygen, nitrous oxide), and an ignition source (e.g. lasers, electrocautery, drills, fiber optic light source).

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9
Q

Most popular ignition source for fires?

A

Electrocautery unit Lasers have the capability of generating the most heat, but the near-universal use of electrocautery makes it the most common ignition source.

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10
Q

Risk factors for OR fires:

A

Risk factors for operating room fires include monitored anesthesia care with an open oxygen delivery system, outpatient surgery, head/neck/upper chest surgeries (85% of all surgical fire claims), and older patient age.

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11
Q

SvO2 and sepsis-late vs early.

A

Peripheral tissues are unable to extract and utilize oxygen effectively in late sepsis. Since oxygen utilization decreases, more oxygen stays in the blood and SvO2 is increased. In early sepsis, oxygen demand may be too large for oxygen supply so there is potential for decreased SvO2. However, the microvascular shunting aspect of sepsis explains why there is reduced oxygen extraction seen with distributive shock.
As a whole, I would say that sepsis increases SvO2, but if they differentiate between early vs late, early has the potential for decreased SvO2.

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12
Q

Myocardial infarction and SvO2?

A

Myocardial infarction results in damage to cardiac cells resulting in both increased O2 demand and decreased cardiac output.

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13
Q

How does the SvO2 thing work? Normal SvO2 level?

A

When O2 demand increases or O2 delivery decreases, the body compensates by increasing cardiac output and/or increasing O2 extraction. An SvO2 less than 75% indicates that more O2 is being extracted from the blood by peripheral tissues before it returns to the right heart.

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14
Q

How often do pacemakers need to be evaluated?

A

Once every 3-12 mos

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15
Q

Electrocautery does what to a pacemaker?

A

It inhibits it, so whatever the underlying rhythm/rate is, the electrocautery will bring that out.

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16
Q

Asynchronous mode will ensure

A

proper pacing un-inhibited by electrocautery.

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17
Q

T/F: For patients that are not pacemaker dependent, placing a magnet could be detrimental.

A

For patients that are not pacemaker dependent, placing a magnet could be detrimental.

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18
Q

Why should you consider serum electrolytes with a pacemaker?

A

In addition, checking serum electrolytes (especially serum potassium) should occur because alterations can make capturing of the pacemaker easier (hyperkalemia) or more difficult (hypokalemia).

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19
Q

Positioning of pacemakers: 1-5

For position 3, what does D mean?

A

1: Chambers Paced
2: Chambers sensed
3: Response to sensing
4: Programmability
5: Multi-site pacing

For position 3, D means that it can both inhibit and trigger a response.

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20
Q

In aortic stenosis, are you relying on the atrial kick?

A

YEs please!

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21
Q

Why do EMI and pacing not get along? If you have to use EMI, which one is better? If you can’t use the better one, then what?

A

EMI may result in oversensing by the pacer causing inappropriate inhibition on the pacing function. If electrocautery is required, a bipolar cautery device should be used if possible else the grounding pad should be placed as far away from the pacemaker as possible without the electrical pathway going through the pacemaker. If feasible, bursts should be limited to less than 10 seconds.

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22
Q

Let’s say that you can’t avoid monopolar EMI in a pt with a pacemaker, what could you do? What happens if you place a magnet over an AICD?

A

Reprogramming of the device may be the best way to avoid intraoperative problems if monopolar electrocautery is planned. Most clinicians will place the patient into an asynchronous mode (AOO, VOO, DOO), this causes the pacemaker to fire at a fixed preset rate, independent of the patient’s underlying cardiac activity. The rate will need to be higher than the patients underlying rhythm to try to ensure that an R-on-T phenomenon does not occur, protecting the patient from arrhythmias.
This is crucial for patients that are not pacemaker dependent. (to prevent the R on T thing) Setting the patient in asynchronous mode can result in competition with the patient’s intrinsic rhythm and may result in the development of a malignant arrhythmia, thus appropriate means to treat this should be available (namely a defibrillator and appropriate antiarrhythmic and blood pressure support medications). In addition, if the patient has an automated implantable cardioverter defibrillator (AICD), this needs to be deactivated if electrocautery is planned under certain circumstances. Tachyarrhythmia therapies, such as overdrive pacing, also need to be disabled. This may also be completed with a magnet in modern devices. Of note, a magnet does not affect pacemaker function for modern AICDs. Rather, magnets inhibit defibrillation in those devices.

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23
Q

Placing a magnet and going into asynchronous mode is not without risk-explain.

A

Placing a magnet is not without risk since asynchronous pacing may trigger ventricular asynchrony in patients with hypoxia, electrolyte imbalances, and myocardial ischemia.

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24
Q

T/F:Whenever minute ventilation (calculated as tidal volume * respiratory rate) exceeds fresh gas flow, rebreathing of exhaled gases will occur, leading to a lower FiO2, compared to the dialed O2 concentration.

A

True, this question was saying that you want to prevent rebreathing of gases, and so basically,When using deep breathing, minute ventilation can easily exceed the fresh gas flow delivered by the anesthesia machine. For example, if one assumes a 70 kg patient with normal pulmonary function has a ~5 L vital capacity, breathing four vital capacity breaths every 30 seconds would mean a minute ventilation of 40 L/min. Even if the patient does not achieve vital capacity in each breath, deep breathing can exceed the 15 L/min delivered by the anesthesia machine, leading to rebreathing and lowering FiO2.

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25
Q

Frequency and how it relates to penetration and resolution

A

Higher frequency (aka wavelength) means better resolution, but worse penetration. Lower frequency gives better penetration but sacrifices resolution.

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26
Q

Velocity =

A

VFW. Velocity = Frequency * Wavelength

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27
Q

What is the mechanism by which a magnetic resonance imaging machine causes skin burns underneath a standard pulse oximeter probe?

A

Induction of electrical current within the probe.

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28
Q

How does a magnetic field create hazards?
Range of Tesla units in MRI?
How does an MRI basically work?

A

There is a potential for generating heat in the monitoring wires as a result of electromagnetic induction, circuit resonance, or an “antenna” effect.
Range of Tesla units: .05-3.0 Tesla units
Basically, the magnetic field can orient the protons in a hydrogen ion, which is the basic principle of MRI.

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29
Q

How do you avoid thermal injuries in MRI?

A

To avoid thermal injuries, it is important to make sure that the monitoring wires are kept straight (avoid loops), that they do not touch the patient in more than one location, and that the wires are not worn out or frayed.

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30
Q

The problem metals with MRI are:

What are the 4 zones of the MRI?

A

Ferrous. The MRI suite is typically divided into four zones. Zone I is the public area with free access. Zone II is the intermediate area between the public and the MRI suite. Zone III is where the introduction of ferromagnetic materials may pose a risk. All movement into Zone III is strictly controlled. Zone IV is the scanner room itself. MRI personnel must screen all individuals entering into Zone III and beyond for any objects or materials that can create a hazard.

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31
Q

What are examples of ferromagnetic metals?

A

nickel, iron, cobalt, tungsten

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32
Q

SBP amplification with intra-arterial blood pressure monitoring of distal sites (e.g. radial artery) results from:
Is pulse pressure wider further away from the aorta?

A

Pressure wave reflection

yes, pulse pressure is wider farther away

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33
Q

Explain the pressure wave thing:

How does this affect MAP?

A

Proximally, the resistance to flow is low due to greater vessel diameter and compliance, therefore degradation of pressure is limited. As blood travels distally in the vascular tree to the arterioles, the resistance to flow increases dramatically with greater decrement in pressure. Thus, pressure waves diminish at the level of the arterioles secondary to increased resistance but the upstream pressure waves are augmented by the retrograde reflection of the previous pressure wave resulting in SBP amplification. Despite amplification mechanisms, mean arterial pressure remains relatively unchanged. Mean arterial pressure in the aorta is only slightly higher than that in the periphery.

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34
Q

Explain resonance:

A

Resonance (C) refers to amplification of the arterial pressure signal due to changes in the transducer system itself. The signal is amplified with long, compliant transducer tubing because it generates higher harmonic frequencies that may approximate the resonant frequency of the system and increase the amplitude. An example of this is when you go over speed bumps with a car you may notice that the faster you go over the bumps the more the car will bounce
Longer tubing=amplified signal.

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35
Q

What ratios do IABP improve? How Sway?

A

myocardial oxygen supply/demand ratio Because the balloon inflates during diastole, it increases coronary perfusion pressure (increases supply) and because it deflates suddenly right at the time the ventricle is about to eject blood, it decreases afterload (decreased wall tension -> decreased oxygen demand).

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36
Q

Why do IABPs make both systolic and diastolic pressure lower than they normally would be?

A

Because of abrupt balloon deflation, the minimum diastolic pressure falls to lower levels that it would have on a non-assisted beat, this end-diastolic aortic pressure is the impedance the ventricle must overcome to eject blood (i.e. afterload).
3) Consequently, the ventricle can eject all of the stroke volume without developing high pressures, resulting in a lower systolic pressure in the beat following the IABP-assisted beat.

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37
Q

With the IABP, can the diastolic be higher than the systolic pressure? explain

A

Because of abrupt balloon deflation, the minimum diastolic pressure falls to lower levels that it would have on a non-assisted beat, this end-diastolic aortic pressure is the impedance the ventricle must overcome to eject blood (i.e. afterload).
3) Consequently, the ventricle can eject all of the stroke volume without developing high pressures, resulting in a lower systolic pressure in the beat following the IABP-assisted beat.
Look at photo

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38
Q

TEE, ECG, and PCWP and their order of HIGHEST to lowest sensitivity in detecting myocardial ischemia

A

Among TEE, ECG, and PCWP, TEE is the most sensitive modality for detecting myocardial ischemia followed by ECG then PCWP.

39
Q

Do you avoid benzos in ECT? Why or why not?

A

Benzodiazepines should be avoided since an increase in the seizure threshold occurs.

40
Q

Explain pH stat, and if anything is added
What does pH stat maintain? based on what temp?
So as the patient is getting cooled, what happens to CO2 and O2? What does pH stat do about it?

A

In pH-stat management, CO2 is infused into the blood to maintain normocarbia and normal pH at the hypothermic temperature the patient is at during the operation. So if the patient is being cooled to 27 degrees Celsius, then the blood gas will be corrected for a body temperature of 27 degrees Celsius. As blood gets colder the partial pressures of CO2 and O2 decrease. So in pH-stat management, the CPB circuit infuses CO2 into the blood to maintain a normal pH at whatever the body temperature is at that point in the case

41
Q

What does pH stat do to P50?

A

pH-stat management adds CO2 to blood which causes a decrease in pH causing a Bohr shift with the rightward shift of the oxyhemoglobin dissociation curve (increased P50).

42
Q

Is there a difference in myocardial preservation in alpha stat vs pH stat?

A

Alpha-stat vs. pH-stat management has no bearing on myocardial preservation.

43
Q

What does pH stat do as far as CBF?

A

pH-stat management infuses extra CO2 into the blood, causing increased CBF and improved homogenous cerebral cooling during hypothermic cardiopulmonary bypass.

44
Q

Your faves:
So when you go up high, what happens to the barometric pressure? How does that affect Concentration of volatiles? What about the parital pressure of volatiles?
Concentration aka ____.

A

A decrease in barometric pressure caused by an increase in altitude will increase the delivered concentration (percentage) of a volatile anesthetic from a variable-bypass vaporizer but the delivered partial pressure (mm Hg) of the anesthetic remains essentially unchanged.
aka percentage

45
Q

So, if you take a vaporizer up high and dial it at 1%, what’s happening-is it compensating? if so how? Do you need to increase the dial?

A

Even after bringing the same vaporizer with the same dialed 1% to 5500 meters (barometric pressure of 0.5 atm or 380 mm Hg), the vaporizer is designed to compensate for the change in barometric pressure and continue to deliver isoflurane at nearly the same partial pressure of 7.6 mm Hg. It does this by increasing the vaporizer output such that the delivered concentration increases to approximately 2% (7.6 mm Hg / 380 mm Hg) despite still being dialed at 1%.

46
Q

What about high altitudes and end-tidal percent concentration as measured by gas analyzers? Which law does this follow?

A

As barometric pressure decreases, the same end-tidal percentage corresponds to a lower partial pressure of volatile anesthetic. This is due to Dalton’s law of partial pressures which says the total pressure exerted by a mixture of gases is the sum of the individual gases’ partial pressures. Therefore, at an altitude of 5500 m, if end-tidal isoflurane reads 1%, the patient will really only receive the partial pressure equivalent of 0.5 MAC. Similarly, if the vaporizer dial is set to deliver 1%, the end-tidal gas monitor should read approximately 2% isoflurane, but the patient is still receiving the partial pressure equivalent of 1 MAC.

47
Q

effects of the volatile anesthetic are directly dependent on ______, not ________.

A

effects of the volatile anesthetic are directly dependent on alveolar partial pressure, not alveolar concentration

48
Q

How do you convert percentage of anesthetic concentration into partial pressure?

A

The percent volatile anesthetic can be converted to partial pressure (mm Hg) by multiplying the percent by 760 mm Hg. For example, 1% isoflurane at sea level produces a partial pressure of 0.01 * 760 mm Hg = 7.6 mm Hg.

49
Q

Desflurane is different than iso or sevo when it comes to the rules of altitude. What’s consistent with them? Why? what should you do if giving des at high altitudes?

A

Desflurane vaporizers generally operate differently: they are typically heated to 39 °C which creates a constant desflurane vapor pressure of 2 atm within the vaporizer, independent of barometric pressure.t then delivers the anesthetic at a fixed percent concentration, not partial pressure. This means that at higher altitudes, the partial pressure of desflurane delivered to the alveoli is reduced due to the fall in atmospheric pressure (again, due to the Dalton law). In order to compensate, the inspired concentration should be manually increased with the dial setting.

50
Q

How can you improve the quality of EKG monitoring in MRI?

A

The quality of the ECG tracing can be optimized by placing the leads close together and toward the center of the magnetic field where the radiofrequency of the magnetic field causes minimal changes.

51
Q

If all of the electricity in the hospital goes out, what can still be used on the anesthesia machine? What can not?

A

In the setting of a power failure or if using a powered down anesthesia workstation, the oxygen delivery and manual positive pressure ventilation capabilities of the workstations are almost always still functional. If vaporizers are mechanical (e.g. variable-bypass, flow-over) they are also likely to be functional-basically just NOT desflurane. Monitoring (CO2 etc) is always fully dependent on electricity.

52
Q

What is FRC? Adding what can increase it?

A

FRC is the amount of air left in the lung at the end of a passive tidal volume breath. Adding PEEP can increase FRC.

53
Q

Pts with obstructive lung dz-do they need longer in inspiration or expiration?

A

They need longer in expiration to get the air out of their lungs

54
Q

Ascites causes someone to have the respiratory mechanics of someone with:

A

Restrictive lung disease

55
Q

Can carbon dioxide be measured with infared light? What about oxygen?

A

Carbon dioxide can be measured with infrared light, oxygen can not.

56
Q

ETCO2 is measured by infared spectrophotometry, but how? What is it proportional to? What is it not proportional to?

A

End-tidal CO2 (ETCO2) is measured by infrared spectrophotometry where a wavelength of infrared light is passed through a gas sample and the amount of energy detected is inversely proportional to the gas partial pressure.

It operates on the principle that the amount of infrared light absorbed at a specific wavelength is proportional to the partial pressure of the gas analyzed because absorption will be greater with a greater amount of gas molecules. Intensity of IR light detected will therefore be inversely proportional to the amount of gas in the sample.

57
Q

Infared spectrophotometry can only be used with which types of gases? And so which gases does it work with?

A

Infrared spectrophotometry only works with gases that are polar, have dissimilar atoms, and are asymmetric.
CO2, N2O, and volatile agents are measured in this manner. Because O2, N2, and xenon are nonpolar, symmetric, and do not have dissimilar atoms, they do not absorb infrared light and cannot be measured in this manner.

58
Q

Risk factors for ACS:

A
  • Decreased abdominal wall compliance: abdominal surgery, prone positioning, major trauma or burns
  • Increased intraluminal contents: gastroparesis, ileus, volvulus
  • Increased intra-abdominal contents: acute pancreatitis, distended abdomen, intra-abdominal infection/abscess/tumors, laparoscopy with excessive inflation pressures, peritoneal dialysis
  • Capillary leakage: acidosis, hypothermia, increased APACHE-II score, massive fluid resuscitation, massive transfusion
  • Miscellaneous risk factors: age, bacteremia, coagulopathy, elevated head of bed, obesity, PEEP>10, peritonitis, pneumonia, sepsis, shock
59
Q

Clinical manifestations of ACS are seen earlier in which type of patients?

A

Clinical manifestations are seen earlier in patients with chronic renal insufficiency, cardiomyopathy, and pulmonary disease.
BUT chronic renal insufficiency is NOT an independent risk factor for renal insufficiency

60
Q

Skin temp and how it correlates with real temp

A

Skin temperature is normally within 2 degrees Celsius of core temperature, despite significant changes in ambient temperature and skin blood flow.

61
Q

If bladder flow is low, then can you count on the bladder temp as being accurate?

A

No

62
Q

Which sites correlate with core temperature?

A

Sites Correlating With Core Temperature:

1) Esophageal
2) Tympanic
3) Pulmonary artery
4) Nasopharyngeal

63
Q

Where to place esophageal temp probe?

A

distal 1/3 of esophagus.

64
Q

FYI:The esophagus and pancreas do not follow the typical distal vs proximal pattern where distal is considered further from the midline. For the esophagus, the distal 1/3 is closest to the stomach and the proximal 1/3 is closest to the mouth.

A

Okay (Waka Flocka face)

65
Q

You are supervising a resident providing anesthesia for an endovascular repair of an abdominal aortic aneurysm. The resident is positioned one foot from the radiation source and is exposed to 8 mrem per second of fluoroscopy. If you encourage her to step one foot back, you will decrease her radiation exposure to which of the following

A

Radiation exposure is inversely proportional to the square of the distance (1/radius^2). By doubling the radius from the source of radiation, the resultant incident radiation is 1/4th. Eight mrem per second divided by four is two mrem per second at the new distance.

Answers A & B & D: 8 mrem/s / (2 feet ^ 2) = 2 mrem/s

66
Q

What is the most common type of laser used in airway surgeries? What is the laser responsible for most airway fires?

A

Carbon dioxide is the most common type of laser used for airway surgeries and accordingly, is responsible for most airway fires.

67
Q

Lens for CO2 lasers:

A

glass/plastic

68
Q

Lens for argon lasers:

A

Amber/orange

69
Q

Lens for krypton lasers:

A

Amber/orange

70
Q

Lens for Nd:YAG

A

Green

71
Q

Lens for KTP-Nd:YAG

A

Red

72
Q

Tell me about the Nd:YAG laser-what damage is done?

A

The Nd-YAG laser is a general-purpose laser that thermally coagulates several millimeters of tissue upon exposure. The light passes through the cornea but can permanently damage the retina within milliseconds of exposure. Protective eyewear with green filters should be worn to prevent eye damage.

73
Q

What is considered a wide complex QRS in kids? And wide complex tachy with evidence of cardiopulmonary compromise should be treated how? What about if they’re hemodynamically stable?

A

Wide complex QRS is defined as greater than 0.09 seconds duration in children. Wide complex tachycardia with evidence of cardiopulmonary compromise should be treated with synchronized cardioversion (0.5-1 J/kg).If the patient with a wide complex tachycardia is hemodynamically stable without evidence of cardiopulmonary compromise then adenosine may be administered.

74
Q

Narrow complex tachycardia in kids: how is it divided? HR in kids? TReadtment?

A

Narrow complex tachycardia can be divided into probable sinus tachycardia versus probable supraventricular tachycardia (SVT). P-waves are present in sinus tachycardia and HR is typically less than 220/min for an infant and 180/min for children (150/min for adults). Supraventricular tachycardia has either absent P-waves or morphologically abnormal P-waves with fixed HR typically > 220 for infants and > 180 for children. Vagal maneuvers and/or adenosine are recommended as first line therapy for SVT. If adenosine is ineffective or IV/IO access is not available, then proceed with synchronized cardioversion. Sinus tachycardia therapy includes treating the cause.

75
Q

When would you use unsynchronized defibrillation?

A

Unsynchronized defibrillation is recommended for ventricular fibrillation.

76
Q

Would you use vagal maneuvers in wide complex tachycardia?

A

No

77
Q 
Compared to a central waveform (a-line), a peripheral a line will have: 
Systolic pressure? 
Pulse pressure? 
dicrotic notch? 
diastolic wave?
A

Relative to a more central arterial waveform, a more peripheral arterial waveform will have a higher systolic pressure, a wider pulse pressure, a more delayed and slurred dicrotic notch, and a more pronounced diastolic wave.

78
Q

Plan for SSEP and MEP monitoring:

A

1) 0.5 MAC of volatile agent to avoid the profound evoked potential depression seen with 1 MAC
2) Short-acting succinylcholine is used instead of longer acting rocuronium (which would make MEP monitoring inaccurate and unobtainable)
3) Intravenous agents (propofol and remifentanil infusions) to supplement the anesthetic which offer less depression of evoked potentials than inhaled agents

79
Q

What happens to the ratio of dead space ventilation to alveolar ventilation with jet ventilation? Most common complication with jet ventilation?

A

he ratio of dead space ventilation to alveolar ventilation increases significantly due to the small tidal volumes delivered with jet ventilation and accordingly, hypercarbia is a frequent complication of its use.

80
Q

Does placement of a magnet stop bi-ventricular pacing function?

A

Of note, placement of a magnet does not typically stop biventricular pacing function, so a conduction delay may not be seen.

81
Q

What is TAPSE?

A

Tricuspid annular plane systolic excursion (TAPSE) is a measure of right ventricular function. A TAPSE of 1.1 cm is moderately depressed. Isolated right heart failure is not an indication for CRT.

82
Q

CRT is indicated in which patients?

A

1) LVEF less than or equal to 35% PLUS
2) Intraventricular conduction delay greater than 120 msec PLUS
3) Heart failure symptoms (NYHA class II, III, or IV) PLUS
4) Sinus rhythm

83
Q

How would you figure this out? A blood gas sent from a patient in deep hypothermic cardiac arrest showed pH 7.25 and PaCO2 55 mm Hg when run at 37 °C. If the patient’s temperature is 27 °C, which of the following would be the expected temperature-corrected values?

A

For each degree Celsius temperature decrease, the pH of blood increases by approximately 0.017. Since the arterial blood gas (ABG) sample is run at 37 °C, the temperature-corrected value is that which corresponds to the patient’s temperature: 10 °C lower. Therefore, the pH at 27 °C would be: 7.25 + (10 x 0.017) = 7.42, corresponding with the closest answer choice of 7.40.

84
Q

Gases and temperature: When cold, does more exist in the gaseous or dissolved form? Which form does partial pressure depend most on?

A blood gas sent from a patient in deep hypothermic cardiac arrest showed pH 7.25 and PaCO2 55 mm Hg when run at 37 °C. If the patient’s temperature is 27 °C, which of the following would be the expected temperature-corrected values?

A

As temperature increases, gases become less soluble and more exists in the gaseous (rather than dissolved) form. Conversely, as temperature decreases, gases become more soluble in solution with less in the gaseous form. Since the partial pressure exerted by a gas is dependent on the amount of gas in the gaseous (rather than dissolved) form, partial pressures of gas decrease as temperature is decreased. Clinically, this is most apparent during hypothermia. When corrected for colder temperatures, an ABG will show decreased partial pressures of oxygen and carbon dioxide. Accordingly, in this example, since the PaCO2 value of 55 mm Hg is obtained from a sample run at 37 °C, the temperature-corrected (to 27 °C) PaCO2 value must be lower.

It is important to realize that only the partial pressures of gases in blood (e.g. CO2, O2) change as temperature changes. The total amount (content) of the gases does NOT change.

85
Q

What are the 2 metals that are MRI safe?

A

Aluminum and brass are the two metals considered MRI safe.

86
Q

What is the alveolar gas equation? Figure this question out:
A 22-year-old medical student is planning a hiking trip to Mount Rainier in Washington state (Barometric pressure 447 mmHg). She wishes to calculate her expected PAO2. What MOST closely approximates this value assuming her PaCO2 on arterial blood gas analysis would be 40 mmHg?

A

Alveolar Gas Equation: PAO2 = FiO2 * (Patm - PH2O) - PaCO2/RER

Answer is 34
Where PAO2 is the calculated alveolar partial pressure of oxygen, FiO2 is the inspired percentage of Oxygen (21% on room air), Patm is the atmospheric pressure (760 mm Hg at sea level), pH2O is the partial pressure of water vapor (47 mm Hg), PaCO2 is the arterial partial pressure of carbon dioxide, and RER is the respiratory quotient (considered to be 0.8 normally). Using the values provided in the stem a PAO2 of 34mm Hg is obtained.
But use 447 as used in stem

87
Q

What does it mean if there is a large difference between peak and plateau airway pressures?

A

It suggests airway obstruction such as from a kinked endotracheal tube.

88
Q

plateau pressure: aka

A

Aka alveolar pressure

89
Q

Normal difference between peak and plateau pressures: What does it mean if there’s not a huge difference between the two?

A

If the peak and plateau pressure are not significantly different (normal is 4-10 cm H2O), it suggests an issue with respiratory compliance such as poor positioning, pulmonary fibrosis, pneumothorax, obesity, or chest wall deformity or compression. Efforts to fix these problems (if modifiable) should be sought.

90
Q

Look at peak pressure and plateau pressure photos:

A

Okay

91
Q

Evaluation of the ventilator pressure waveforms, especially with volume control, can provide diagnostic information about respiratory system compliance and resistance. Elevated peak pressures with a large difference between peak and plateau pressures suggest increased airway resistance. Elevated plateau pressures (without a significant difference between peak and plateau pressures) suggest decreased respiratory compliance.

A

Freebie

92
Q

Hydromorpone-is it better than morphine with renal failure?

A

Yes it is.

93
Q

Full face CPAP vs nasal CPAP in infants:

A

Nasal CPAP decreases atelectasis and maintains recruitment

94
Q

FRC is lower in neonates, but when does that start changing?

A

Functional residual capacity is lower in neonates, but this increases over the first few days of life and reaches adult levels at about day 4.

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