1. Ventilation / Ventilation Control Tests
RET 2414
Pulmonary Function Testing
Module 5.0

2. Ventilation / Ventilation Control Tests
Objectives
Calculate tidal volume and minute ventilation
Describe two causes of increased ventilation
Identify an abnormal VD/VT ratio

3. Ventilation / Ventilation Control Tests
Objectives
Calculate dead space and alveolar ventilation
Describe one method for measuring breathing response to O2
Identify the normal breathing response to carbon dioxide (CO2)

4. Ventilation / Ventilation Control Tests
VT, Rate, Minute Ventilation
Tidal volume (VT) is
Volume of gas inspired or expired during each respiratory cycle
Respiratory rate (f)
Number of breaths per unit of time
Minute ventilation ( )
Total volume of gas expired per minute
alveolar ventilation ( )
dead space ventilation ( )

5. Ventilation / Ventilation Control Tests
VT, Rate, Minute Ventilation
VE = f x VT
Measured with volume displacement or flow-sensing spirometer .

6. Ventilation / Ventilation Control Tests
VT, Rate, Minute Ventilation
VT decreased in:
Severe restrictive patterns
Neuromuscular disorders
Decreased VT is usually accompanied by an increase in respiratory rate in order to maintain alveolar ventilation ( )

7. Ventilation / Ventilation Control Tests
VT, Rate, Minute Ventilation
Decreases in both VT and respiratory rate are often associated with respiratory center depression
Alveolar hypoventilation

8. Ventilation / Ventilation Control Tests
VT, Rate, Minute Ventilation
Normal respiratory rates ranges:
10 – 20 breaths/min
Increased in:
Hypoxia
Hypercapnia
Metabolic acidosis
Decrease lung compliance
Exercise

9. Ventilation / Ventilation Control Tests
VT, Rate, Minute Ventilation
Normal respiratory rates ranges:
10 – 20 breaths/min
Decreased in:
Central nervous system depression
CO2 narcosis; a condition resulting from high levels of carbon dioxide in the blood. Confusion, tremors, convulsions, and coma may occur if blood levels of carbon dioxide are too high (>70 mm Hg or higher).

10. Ventilation / Ventilation Control Tests
VT, Rate, Minute Ventilation
Normal minute ventilation ranges:
5 – 10 L/min
When used in conjunction with arterial blood gases, indicates the adequacy of ventilation

11. Ventilation / Ventilation Control Tests
VT, Rate, Minute Ventilation
Normal minute ventilation ranges:
5 – 10 L/min
increases in response to:
Hypoxia
Hypercapnia
Metabolic acidosis
Anxiety
Exercise

12. Ventilation / Ventilation Control Tests
Dead Space /Alveolar Ventilation
Dead space is the lung volume that is ventilated but not perfused by pulmonary capillary blood flow
Anatomic (conducting airways) VDan
Alveolar (non-perfused alveoli) VDA
VDan + VDA = VD
VD (Respiratory or Physiologic Dead Space)

13. Ventilation / Ventilation Control Tests
Anatomic Dead Space

14. Ventilation / Ventilation Control Tests
Dead Space /Alveolar Ventilation
The portion of ventilation wasted on the conducting airways and poorly perfused alveoli is usually expressed as a ratio:
VD/VT = (PaCO2 – PECO2) X 100
PaCO2
Modification of Bohr’s equation

15. Ventilation / Ventilation Control Tests
Dead Space /Alveolar Ventilation
For convenience VD is often estimated as equal to anatomic deadspace;
VD = 1 ml/lb of ideal body weight
Valid only if little or no alveolar dead space exists due to pulmonary disease

16. Ventilation / Ventilation Control Tests
Dead Space /Alveolar Ventilation
Normal VD/VT ratio in adults:
0.3 or 30% (0.2–0.4 or 20%–40%)
Increases with:
Pulmonary embolism
Acute pulmonary hypertension
Decreased cardiac output
Decreases with:
Exercise (increase cardiac output and perfusion of lung apices)

17. Ventilation / Ventilation Control Tests
Dead Space /Alveolar Ventilation
Alveolar ventilation is the volume of gas that participates in gas exchange in the lungs per minute

18. Ventilation / Ventilation Control Tests
Dead Space /Alveolar Ventilation
Alveolar ventilation at rest is approximately 4 – 5 L/min
The adequacy of can only be determined with an arterial blood gas (ABG)
Hypoventilation = PCO2 >45 with a pH <7.35
Hyperventilation = PCO2 <35 with a pH >7.45

19. Ventilation / Ventilation Control Tests
Dead Space /Alveolar Ventilation
Decreased can result from:
Increases in VD
Destruction/dilation airway walls
>FRC (air trapping/hyperinflation)
Bronchodilators
Decreases in

20. Ventilation / Ventilation Control Tests
Ventilatory Response to CO2
Ventilatory response to CO2 is a measurement of the increase or decrease in caused by breathing various concentration of carbon dioxide while PaO2 is kept normal

21. Ventilation / Ventilation Control Tests
Ventilatory Response to CO2
Procedure
1-7% CO2 is breathed through either an open or closed circuit while the following are measured:
PeTCO2
SaO2
P100

22. Ventilation / Ventilation Control Tests
Ventilatory Response to CO2
Normal response to an increased PACO2 is a linear increase in ventilation ( )
Approximately 3 L/min/mm Hg (PCO2)

23. Ventilation / Ventilation Control Tests
Ventilatory Response to CO2
Decreased in patients with:
COPD
Increased airway resistance (Raw)
Lesions in the CNS
Chemoreceptor dysfunction

24. Ventilation / Ventilation Control Tests
Ventilatory Response to Oxygen
Ventilatory response to O2 is a measurement of the increase or decrease in causes by breathing various concentration of O2 while PaCO2 is kept normal

25. Ventilation / Ventilation Control Tests
Ventilatory Response to Oxygen
Procedure
20%-12% O2 is breathed through either an open or closed circuit while the following are measured:
, PaO2, P100, PetCO2
The test is repeated with decreasing concentrations of O2

26. Ventilation / Ventilation Control Tests
Ventilatory Response to Oxygen
Normal response to a decreasing PaO2 is an exponential increase in ventilation ( ) once the PaO2 is less than 60 mm Hg (SaO2 <90%)
60 torr/90% Saturation O2

27. Ventilation / Ventilation Control Tests
Ventilatory Response to Oxygen
Significance and Pathology
Patients with obesity-hypoventilation syndrome, obstructive sleep apnea, and idiopathic hypoventilation will show a marked decrease response to hypoxemia

28. Ventilation / Ventilation Control Tests
Occlusion Pressure (P100 or P0.1)
P100 is the pressure generated during the first 100 milliseconds of inspiratory effort against an occluded airway.
It is a measurement of the neural output from the medullary centers that drive ventilation rate and volume

29. Ventilation / Ventilation Control Tests
Occlusion Pressure (P100 or P0.1)
Normally P100 values are:
1.5 – 5.0 cm H2O
Usually measured at varying PetCO2 values or levels of O2 desaturation to assess the effect of changing stimuli to ventilation

30. Ventilation / Ventilation Control Tests
Occlusion Pressure (P100 or P0.1)
P100 is usually plotted against PetCO2

31. Ventilation / Ventilation Control Tests
Occlusion Pressure (P100 or P0.1)
P100 values will normally increase with PaCO2 (hypercapnia) or PaO2 (hypoxemia)
Healthy patients typically increase occlusion pressure 0.5 to 0.6 cm H2O/mm Hg PCO2
Patients with COPD will not increase the P100 when the PaCO2 in increased