by gnomey

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What is tidal volume? normal value
volume of gas that moves in and out of lung during quiet breathing

What is vital capacity? NV?
Capability of taking deep breath and cough (Vt+IRV+ERV)

60mL/Kg +/- 20%
What can decreased VC?
restrictive lung disease or atelectasis
What is the inspiratory capacity?
largest volume of gas that can be inspired from resting expiratory level
What causes a decrease in inspiratory capacity?
significant extrathoracic airway obstruction
T/F inspiratory capacity changes parrell changes in vital capacity
What is functional residual capacity?
volume of gas remaing at passive end expiration
What two primary physiologic functions does the FRC determine?
1. determines the point on the pulmonary volume-pressure cure for resting ventilation
2. primary determinant of oxygen reserve when apnea occurs
What happens to V/Q match when FRC is reduced?
low V/Q (venous admixture) increases and results in arterial hypoxemia
What disease processes decrease FRC and lung compliance? 4
1. ALI
2. pulmonary edema
3. pulmonary fibrosis
4. atelectasis
What is the forced vital capacity?
volume of gas that can be expired as forcefully and rapidly as possible after maximal inspiration
What is FRC usually equal to?
Vital capacity
When are FVC values associated with increased PPCs?
What changes in FVC and VC do you see in COPD patients?
Decrease in FVC
VC is normal
What is FEV1?
Percentage of the FVC that can be exhaled in one second

it is a measurement of flow
What is a normal FEV1/FVC ratio?
75% of FVC
What disease, restrictive/obstructive, has a normal FEV1/FVC ratio?

That is because the lungs don't have difficulty increasing transpulmonary pressure for expiration, they have difficulty decreasing transpulmonary pressure for inspiration
What is FEF25-75%?
the average forced expiratory flow during the middle half of the FEV maneuver

AKA maximum midexpiratory flow rate
A decrease in MMFR is sensitive in what respiratory diseases?
Early stages of obstructive airway diseases

It is representative of decreased flow in medium-sized airways
What is a strength of the MMFR?
much more reliable and reproducable than FEV1/FVC
FEV1 is inc/dec in obstructive diseases, and inc/dec in restrictive diseases?
Both of them have decreased FEV1 values, however their ability to forcibly exhale their VC over a duration of time is different.

ie COPDer has a decreased FEV1, but have a decreased FEV1/FVC ratio due to obstructed airways/loss of elasticity of alveoli  prolonging and decreasing slope of flow rate
What occurs first in obstructive airway diseases decreased FEV1/FVC or MMFR?
What is maximum voluntary ventilation?
largest volume of gas that can be breathed in 1 minute by voluntary effort

Pt breathes deeply and rapidly for 10,12,15 seconds
What does the MMV test measure?
endurance of ventilatory muscles

-indirectly reflects lung-thorax compliance and airway resistance
WHat happens to the MMV value in pt with airway diseases? obstructive vs. restrictive
Decreased MMV in pt with mod-severe obstructive disease because it exagerrates air trapping

Restrictive- normal
DLCO measures what?
diffusing capacity of an inhaled gas, ie Carbon Monoxide
What disease process cause a decrease in diffusing capacity? 5
Alveolar fibrosis r/t:
1. sarcoidosis
2. oxygen toxicity
3. pulmonary edema
4. asbestosis
5. berylliosis
What is the primary criterion on a PFT for airflow obstruction?
Decreased FEV1/FCV ratio

Less than <75%
IN restrictive lung diseases what happens to VC, FVC, FEV1, and FEV1/FRC?
there is a proportional decrease in all lung volumes, except that FEV1/FRC remains normal

Ultimate diagnosis of restrictive lung disease is to measure TLC
Differnce in FEV1/FRC in obstructive vs. restrictive lung disease?
Obstructive- large decrease
Restrictive- normal
What are preoperative signs of pulmonary disease that can be found during interview?
hx of:
1. sputum production
2. wheezing or dyspnea
3. exercise intolerance
4. limited daily activities
When should an ABG be drawn?
When you suspect CO2 retention or chronic hypoxemia

You need to draw them to establish baseline values, so you know how to guide treatment during and after the surgery
When does PFT have it's most benefit, when not?
Pt having a lung resection, PFT maybe have some predictive benefits

In all other patients PFTs seem not to predict or assign risk for PPC
What are independent risk factors that increase risk of having a PPC?
>65 years
smoking > 40 pack-years
productive cough
exercise in tolerance of < 1 flight of stairs
What is the benefit of having asthmatic or COPD patient use bronchodilator preoperatively?
decreases the risk of reflex bronchospasm during laryngoscopy
What is better for  patient with severe obstructive disease under GA, spontaneous or mechanical ventilation?
Mechanical ventilation, pt with severe obstructive disease is more likely to have hypercapnia with SV
What is a ventilator strategy for a patient with obstructive lung disease?
Slower RR, so that there is more time for exhalation

Higher Vt, but limit PAP to less than 40cmH2O, to maintain normal PaCO2
What is a ventilator strategy for a patient with restrictive lung disease?
Lower Vt and higher RR
WHo is more likely to develop arterial hypoxemia first, obstructive or restrictive lung disease?
Restrictive lung disease because they have a decreased FRC, thus a smaller Oxygen reserve, compared to obstrutcitive who has an increased FRC
What is the normal decrease in FRC in healthy patients in supine spontaneous breathing patient? under GA?
10-15% decrease in supine spontaneous breathing

add'n 5-10% in pt under GA
How long does it take for the FRC to reach its lowest level under anesthesia?
10 minutes, and is independent of spontaneous or controlled ventilation
What occurs to ventilation/perfusion as a result of gas trapping?
Gas trapping causes increased areas of dead space ventilation and venous admixture
What is the typical Ve for patient with obstructive lung disease?
1.5-2x normal
In a smoker how long does it take for carbon monoxide concentration to become normal?
12-24 hours
What is the recommended time of smoking cessation prior to surgery?
more than 8 weeks.

Pts who quit less than 8 weeks before surgery have a higher rate of complication than those who smoke up to surgery
How lung does it take normal mucociliary function to return?
takes 2-3 weeks of abstenence, and sputum prodution increases during this time
What are the recommendations for smoking cessation prior to surgery?
>8 weeks to maximize the effect of smoking cessation

At least 4 weeks to benefit from improved mucociliary function and have some reduction in PPC risk
What surgeries have the most profound decrease in FRC?
40-50% decrease in nonlaproscopic upper abdominal surgeries, d/t to restrictive effect

30% decrease in lower abdominal and thoracic surgeries

15-20% in all others
what is normal FEV, FVC, FEV/FVC?
FEV/FVC- 80%
What are FEV, FVC, FEV/FVC in obstructive diseases
FEV-1.3  (decreased)
FVC-3.1   (decreased)
FEV/FVC 42%  (decreased)
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