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| What is tidal volume? normal value
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volume of gas that moves in and out of lung during quiet breathing
6-8mL/kg | ||
| What is vital capacity? NV?
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Capability of taking deep breath and cough (Vt+IRV+ERV)
60mL/Kg +/- 20% | ||
| What can decreased VC?
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restrictive lung disease or atelectasis
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| What is the inspiratory capacity?
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largest volume of gas that can be inspired from resting expiratory level
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| What causes a decrease in inspiratory capacity?
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significant extrathoracic airway obstruction
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| T/F inspiratory capacity changes parrell changes in vital capacity
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T
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| What is functional residual capacity?
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volume of gas remaing at passive end expiration
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| What two primary physiologic functions does the FRC determine?
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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?
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low V/Q (venous admixture) increases and results in arterial hypoxemia
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| What disease processes decrease FRC and lung compliance? 4
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1. ALI
2. pulmonary edema 3. pulmonary fibrosis 4. atelectasis | ||
| What is the forced vital capacity?
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volume of gas that can be expired as forcefully and rapidly as possible after maximal inspiration
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| What is FRC usually equal to?
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Vital capacity
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| When are FVC values associated with increased PPCs?
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<15ml/kg
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| What changes in FVC and VC do you see in COPD patients?
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Decrease in FVC
VC is normal | ||
| What is FEV1?
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Percentage of the FVC that can be exhaled in one second
it is a measurement of flow | ||
| What is a normal FEV1/FVC ratio?
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75% of FVC
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| What disease, restrictive/obstructive, has a normal FEV1/FVC ratio?
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restrictive
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%?
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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?
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Early stages of obstructive airway diseases
It is representative of decreased flow in medium-sized airways | ||
| What is a strength of the MMFR?
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much more reliable and reproducable than FEV1/FVC
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| FEV1 is inc/dec in obstructive diseases, and inc/dec in restrictive diseases?
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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?
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MMFR
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| What is maximum voluntary ventilation?
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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?
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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
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Decreased MMV in pt with mod-severe obstructive disease because it exagerrates air trapping
Restrictive- normal | ||
| DLCO measures what?
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diffusing capacity of an inhaled gas, ie Carbon Monoxide
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| What disease process cause a decrease in diffusing capacity? 5
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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?
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Decreased FEV1/FCV ratio
Less than <75% | ||
| IN restrictive lung diseases what happens to VC, FVC, FEV1, and FEV1/FRC?
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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?
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Obstructive- large decrease
Restrictive- normal | ||
| What are preoperative signs of pulmonary disease that can be found during interview?
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hx of:
1. sputum production 2. wheezing or dyspnea 3. exercise intolerance 4. limited daily activities | ||
| When should an ABG be drawn?
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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?
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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?
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>65 years
smoking > 40 pack-years COPD Asthma productive cough exercise in tolerance of < 1 flight of stairs | ||
| What is the benefit of having asthmatic or COPD patient use bronchodilator preoperatively?
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decreases the risk of reflex bronchospasm during laryngoscopy
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| What is better for patient with severe obstructive disease under GA, spontaneous or mechanical ventilation?
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Mechanical ventilation, pt with severe obstructive disease is more likely to have hypercapnia with SV
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| What is a ventilator strategy for a patient with obstructive lung disease?
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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?
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Lower Vt and higher RR
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| WHo is more likely to develop arterial hypoxemia first, obstructive or restrictive lung disease?
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Restrictive lung disease because they have a decreased FRC, thus a smaller Oxygen reserve, compared to obstrutcitive who has an increased FRC
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| What is the normal decrease in FRC in healthy patients in supine spontaneous breathing patient? under GA?
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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?
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10 minutes, and is independent of spontaneous or controlled ventilation
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| What occurs to ventilation/perfusion as a result of gas trapping?
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Gas trapping causes increased areas of dead space ventilation and venous admixture
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| What is the typical Ve for patient with obstructive lung disease?
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1.5-2x normal
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| In a smoker how long does it take for carbon monoxide concentration to become normal?
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12-24 hours
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| What is the recommended time of smoking cessation prior to surgery?
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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?
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takes 2-3 weeks of abstenence, and sputum prodution increases during this time
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| What are the recommendations for smoking cessation prior to surgery?
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>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?
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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?
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FEV-4L
FVC-5L FEV/FVC- 80% | ||
| What are FEV, FVC, FEV/FVC in obstructive diseases
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FEV-1.3 (decreased)
FVC-3.1 (decreased) FEV/FVC 42% (decreased) | ||
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