1. Respiratory monitoring
Peter C. Rimensberger
Pediatric and Neonatal ICU
University Hospital of Geneva
Switzerland

2. Respiratory Monitoring
Basic Mechanism of PPV O2
CO2
Gas Exchange
Volume Change
Time
Gas Flow
Pressure Difference

3. . . Pressure – Flow – Time - Volume on the ventilator display
V / P / V . t
Curves .
V or V
P or V
Loops
- to assess patient-ventilator synchrony
to get some information on respiratory mechanics under dynamic conditions (!)
to detect erroneus ventilator settings
to guide in the search for optimal ventilator settings

4. Tobin M NEJM 2002

5. The Pressure-Volume Curve: Useful at bedside?
How to monitor
at bedside?
1) PV-tools +/-

6. Assessment of Static P-V Curve
Volume
Volume
Super-syringe method:
Stepwise inflation from a big syringe with multiple occlusions at each volume to record recoil pressure
Time consuming
Cumbersome to perform
Difficult to standardize
Patient must be paralyzed
Great risk of oxygen desaturation
The “Gold Standard” for P-V curves is the syringe method. However it has many disadvantages if tried on an ICU patient on a mechanical ventilator.
Pressure
Pressure

7. Slow Flow Single Inflation Method
Slow inspiratory flow with large Vt and ZEEP
The inspiratory curve of the dynamic P-V loop closely approximates the static curve (inluenced by flow and tube resistance)
Volume
UPIflex
Static curve
inspiration
The “slow flow single inflation method” can be performed in the ICU and has a good correlation to the gold Standard
Servillo: AJRCCM 1997
Lu: AJRCCM 1999
Kondili: ICM 2000
Casati Nogueira Gama: Artifical Organs 2001
LPIflex
Pressure

8. Is the static PV-curve useful?
Downie JM et al. AJRCCM e- publ February 5, 2004
Is the static PV-curve useful?
Jonson B AJRCCM 1999;159:1172–1178
Rimensberger PC Crit Care Med 1999; 27:

9. Pressure measurements under dynamic conditions
ETT 3 mm OD
Sondergaard S Ped Research 2002; 51:

10. Monitoring of the dynamic cycle: Is it better?
Kárason S Acta Anaesthesiol Scand 2000; 44: 571
0.8 Pmax Pmax
Volume
Pressure
Cdyn
C20
Overdistention Index: C20/Cdyn
Kárason S Acta Anaesthesiol Scand 2001; 45: 173

11. ongoing overdistension ongoing recruitment full recruitment
Ranieri VM Anesthesiology 2000; 93:1320–8

12. Lung protection and the open lung concept
How to monitor
at bedside?
1) PV-tools +/-
2) O2-response?
Brazelton TB Crit Care Med 2001; 29:2349

13. The oxygen response (limitations)
P/F-ratio, oxygen delivery and Crs during PEEP steps
Lichtwarck-Aschoff M AJRCCM 2000; 182:

14. The oxygenation response: Can it be used? PEEP and Vt effects in ALI
Recruitment
Overdistension
"static" compliance:
static PIP (Pplat) - PEEP
tidal volume
Cst =
Burns D J Trauma 2001;51:

15. Constant VT : Plateau - PEEP []
PEEP [cm H2O] 10 20 30 40 50
Airway pressure [cmH2O]
PEEP
Plateau
Prevalent
overdistention
Prevalent
recruitment
Balance 25 20 15 15 10 20 15 5
L. Gattinoni, 2003

16. Constant VT : PaCO2 and PaO25 10 15 20
PEEP [cmH2O] 40 60 80
100
[mmHg]
PaCO2
PaO2
Prevalent
overdistention
Balance
Prevalent
recruitment
L. Gattinoni, 2003

17. O2-improvement = Shunt improvement =
a) recruitment
PaO2
PaCO2 VA
b) flow diversion
PaO2 VA
PaCO2
L. Gattinoni, 2003

18. Prevalent overinflation = dead space effect
PEEP 20 1 2 1 –
PEEP
PaO2 and PaCO2 increase
L. Gattinoni, 2003

19. PEEP titration CO2-response Oxygenation Overdistention starts PEEP 25

20. The open lung concept: Maximum dynamic compliance and best oxygenation at the least pressure required
Steps of 5 cmH2O to 40/25
Pressure control ventilation
25/10
25/10
Overinflation ends
Overinflation starts

21. Continuous blood gas monitoring during HFO
CDP: 13 12 11 10 9 11
Overdistention
Collapse

22. PCO2 cascade PECO2 PETCO2 PACO2 PcCO2 PvCO2 VCO2 PvCO2 PaCO2
Ventilated/
perfused lung
PETCO2
Alveolar
VD/VT
Anatomic
VD/VT
PCO2
cascade
PcCO2
PvCO2
VCO2
PvCO2
PaCO2
L. Gattinoni, 2003

23. Ideal gas exchange Alveolar PCO2 = Arterial PCO2 Alveolar PCO2 =
End-tidal PCO2
NO SHUNT
NO ALVEOLAR VD/VT
End-tidal PCO2
Arterial PCO2
= 1

24. Single breath CO2-tracing
The values come from the measurement of the CO2 tracing where phase I is CO2 free and represents gas from the airway (ariway dead space). The second phase is te rapid upswing when convective airway are washed out with alveolar gas. The third phase is the ”plateau” which actually is gradually ascending value due to a) sequential emptying of lung regions with different V/Q-ratios; b) within units V/Q mismatching secondary to incomplete gas mixing; c) the continual release of CO2 into the alveoli during expiration.
Phase III Alveolar gas – called plateau but ascends gradually due to
sequential emptying of lung regions with different V/Q-ratios
within units V/Q mismatching secondary to incomplete gas mixing
the continual release of CO2 into the alveoli during expiration
Phase II Rapid S-shape upswing = washout of convective airway with alveolar gas
Phase I CO2-free = gas from airways
Modified from “The Single breath test for carbon dioxide” by Roger Fletcher (1986)

25. CO2 in ventilatory monitoring
etCO endtidal value
FeCO2 fraction of CO2 in expired gas
VCO2 minute elimination (”production”)
VTCO2 tidal elimination
We are used to use Carbondioxide during monitoring in the ICU and OR the most common to use is the endtidal value of CO2 and the fraction of expired CO2 during anesthesia. Since many years we have had the possibility to measure tidal and minute elimination of CO2 on the Servo ventilators but I have not – have you??

26. VTCO2 Following VTCO2 continuously could
help us to understand the effectiveness of different ventilation modes and settings
Could VTCO2 continuously followed
help us to do recruitment maneuvers with minimized overdistension?
Following VTCO2 continuously could help us understand the effectiveness of different ventilation modes and settings.
Could it possibly help us to do recruitment maneuvers with minimized overdistension?

27. Volumetric Capnography (NICO2) Single Breath CO2 Analysis
Validated against a metabolic analyzer by Kallet et al, Resp Care 2005
and used in many studies for dead space fraction measurements

28. Volumetric Capnography Single Breath CO2 Analysis
CO2 and Volume
instead of
CO2 and Time
Capnogram

29. Volumetric Capnography Single Breath CO2 Analysis
III II I

30. Indicator of Lung Overdistension During PEEP Titration
Optimum End Expiratory Airway Pressure in Patients with Acute Pulmonary Failure
Suter PM, Fairley HB, Isenberg MD. NEJM 1975
Best PEEP corresponds to the lowest dead space fraction and the highest compliance

31. Indicator of Lung Overdistension During PEEP Titration
Effects of PEEP on Dead Space and its Partitions in ALI
Beydon L, et al. Inten Care Med 2002
Anatomic dead space increased slightly with PEEP
Alveolar dead space did not vary systematically with PEEP
In individual patients a decrease or increase of alveolar dead space paralleled a positive or negative response to PEEP in regards to oxygenation

32. And then put the pig on the new ventilation with 17/10 and read that the Cdyn has increased from 11 to 17. The cyclic pressure-difference has decreased from 25/6 to 17/10 which means from 19 to 7 and tidal volume from 207 to 117 and the PaCO2 value is about the same from 6,4 to 5,2. VT
PIP / PEEP 25/6 24/12 40/12 15/8 40/12 17/10
Cdyn

33. Lung protection and the open lung concept
How to monitor
at bedside?
1) PV-tools +/-
2) O2- + CO2-response
3) Chest CT and imaging methods?
Gattinoni L AJRCCM 2001; 164:1701–1711

34. Information from CT studies: Lung heterogeneity
and intratidal collapse and decollapse
In heterogeneous lung injury inflation behaviour is heterogeneous
PA = 35 cmH2O
PA = 15 cmH2O
Adapted from Suter P NEJM 1975; 292:

35. CT to assure more homogenoeus lung volume distribution
Barbas C Curr Opin Crit Care 2005;11:18–28
Barabs

36. CT-aeration - and how to detect overdistention? At ZEEP and
poorly areated
normal
CT-aeration
- and how to detect overdistention?
Diffuse CT-attenuations
At ZEEP and
2 PEEP levels
Focal CT-attenuations
Rouby JJ AJRCCM
2002;165:1182-6

37. Electrical Impedance Tomography (EIT)
Frerichs I et al. J Appl Physiol 2002; 93: 660–666
Volume
distribution
Frerichs I, Dargaville P, Rimensberger PC Intensive Care Med 2003; 29:2312-6

38. Volume distribution Tidal volume distribution
Frerichs I, Dargaville P, Rimensberger PC Intensive Care Med 2003; 29:2312-6

39. EIT to assure more homogenoeus lung volume distribution
Barbas C Curr Opin Crit Care 2005;11:18–28
Barabs

40. Concepts of respiratory monitoring in the ICU
Control system
Diagnostic tool
To improve outcome
1. Assure gas transfer/exchange
2. Assure Vt-delivery (V-t / V-t / P-t curve characteristics) .
Biomechanical properties of lung and airways
To improve understanding of lung disease and ventilator-patient interaction
To avoid errors / incidents

41. From classical respiratory monitoring to tracking thoracic volume changes during ventilation maneuvers
Flow-, Volume- and Pressure-measurements
Pressure-volume methods: static vs. dynamic observe dynamic compliance changes
Gas exchange response: pO2 and pCO2
Lung-Volume measurement methods: RIP, dilution methods, CT / MRI / EIT
Tidal-volume distribution: EIT