1. Alveolar Ventilation During General Endotracheal Anesthesia
Valentyna Groelle, RN, BSN, SRNA

2. Objectives Review the physiology of alveolar ventilation
Discuss pulmonary changes after induction of general endotracheal anesthesia
Describe how to perform two major types of alveolar recruitment maneuvers

3. Conducting vs Gas Exchange Airways

4. Alveolar-Capillary Gas Exchange

5. Physiology of Gas Exchange
Ventilation
External Respiration
Internal Respiration

6. West’s Zones of the Lung
“Dead space”
“Shunt-like”

7. Alveolar Ventilation Alveolar Ventilation VA= RR x (VT-VD)
Physiologic Dead Space
VD/VT = (PaCO2−PECO2)/PaCO2

8. Alveolar Gas Exchange in Lung Disease

9. ARDS

10. Asthma

12. COPD and Air Trapping
NORMAL
COPD

13. Atelectasis

14. A-a Gradient
A-a Gradient= PAO2-PaO2
PAo2=FiO2(Patm-PH2O)-PaCO2/0.8

15. Increased A-a gradient
Causes of Hypoxemia
Normal A-a gradient
Increased A-a gradient
Hypoventilation
Low Inspired O2
Right to Left Shunt
V/Q Mismatch
Diffusion Impairment

16. Causes of Hypoxemia Normal A-a gradient
Hypoventilation
Neuromuscular disorder
CNS disorder
Depression of CNS by drugs
Low Inspired Oxygen
PiO2=(Patm-PH2O)xFiO2
High altitude
Low FiO2

17. Causes of Hypoxemia Increased A-a gradient
Right to Left Shunt
(alveoli blocked from ventilation)
CHF
ARDS
Drowning
(due to congenital abnormalities)
Intra-cardiac shunt
Intra-pulmonary fistulas

18. Causes of Hypoxemia Increased A-a gradient
V/Q Mismatch (due to lung dead space or shunt) PE
Atelectasis
PNA
Obstructive lung disease (asthma, COPD)
Pneumothorax
“Shunt-like”
“Dead-space”
VA= 4-6 L/min
Q=5-6 L/min
V/Q=

19. Causes of Hypoxemia Increased A-a gradient
Diffusion impairment
Interstitial lung disease
Environmental disease

20. Induction of General Anesthesia

21. Cessation of Sigh Breaths

22. Absorption Atelectasis
Solubility of gases in blood plasma:
Carbon dioxide>oxygen>nitrogen

23. Airway Closure from ↓ FRC

24. Compressive Atelectasis
Transpulmonary P =Intrapulmonary/Alveolar P-Intrapleural P
Transpulmonary P= 760mmHg-756mmHg= +4mmHg

25. Open Lung Ventilation Alveolar Recruitment Maneuvers Low Tidal Volumes
PEEP

26. Alveolar Recruitment Maneuvers
1. The lung’s opening pressure
2. The lung’s closing pressure
3. The open-lung PEEP

27. Sustained Inflation Recruitment Maneuvers

28. Cycling Maneuvers

29. Hemodynamic Pre-Conditioning Phase
PEEP of 5 cmH2O= 3.67 mmHg
PEEP of 10cmH2O= 7.35 mmHg
PEEP of 13cmH2O= 9.55mmHg
Normal CVP: 0-8 mmHg
Normal PAP (systolic): mmHg
Normal PAP (diastolic): 8-15mmHg

30. Cycling Maneuvers

31. SI vs Cycling Recruitment Maneuvers

32. Questions