1. Thermistor Qualitative signal
Measurement of the temperature of inspired and expired airflow
No linear correlation with ventilation
Unreliable for hypopnea detection

2. Nasal cannula Curvilinear relationship between pressure and flow
Good sensitivity to detect hypopnea and flow limitation
Mouth opening reduces performance

3. Measuring oronasal airflow
Thermistors : monitor temperature, not flow
Nasal cannulae :
P~ V² 3

4. Inductive Plethysmography
Quantitative: requires titration, can’t last overnight
Semi-quantitative: reliable for clinical use

5. Piezo sensors and strain gauges
Qualitative
In hypopnea detection should be linked to other signals
To be placed where maximal excursion of thorax and abdomen are detected

6. Continuous
Snoring
Intermittent
Snoring

8. Hernandez, L. et al. Chest 2001;119:442-450

9. Nasal cannula Normal flow Flow limitation Mouth opening
Cardiogenic oscillations (central apnea)

10. 10

11. 11

12. 12

13. 13

14. Thoraco-abdominal Movements
Paradoxical Movements
Movements in phase

17. EEG
O1A2
EEG
C3A2
EOG sx
EOG dx
EMG
ECG
flow
thorax
abd.
SaO2

18. 18

20. 20

21. 21

22. 22

23. 23

24. Hypopnea

25. 25

26. 26

27. 27

28. 28

29. 29

30. 30

31. Hernandez, L. et al. Chest 2001;119:442-450
Different sensors give different information
Hernandez, L. et al. Chest 2001;119:

32. 32

33. RERA
Flow limitation

34. 34

36. 36