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Monitoring of Ventilation and Air Leakage during CPAP. Gerd Schmalisch. Clinic of Neonatology Charité-Universitätsmedizin Berlin. Outline. Ventilation and air leakage measurements during MV Peculiarities of ventilation monitoring during CPAP Theoretical background

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Monitoring of Ventilation and Air Leakage during CPAP

Gerd Schmalisch

Clinic of Neonatology

Charité-Universitätsmedizin Berlin



  • Ventilation and air leakage measurements during MV
  • Peculiarities of ventilation monitoring during CPAP
  • Theoretical background
  • Air leakages and volume correction
  • Clinical studies
  • Conclusions and outlook

Volume monitoring during MV

Displayed volume:


Displayed air leakage:


Relationship between volume error and displayed leak during MV

Mahmoud R, et al. Acta Paediatr. 98 (2009) 1116-1122


Endotracheal tube leakage in newborns

Frequency distribution of ET leakage of 163 ventilated (>5h) newborns

No ET leakage:

79/163 (48%)

ET leakage < 20%:

125/163 (77%)

ET leakage >40%:

12/163 (7.4%)

Temporarily ET leakage >40% during MV

59/163 (36%)


Peculiarities of ventilation monitoring during CPAP

  • Different aims of monitoring
  • Different patient interfaces
  • Much higher air leakages
  • Spontaneous breathing (breath detection)
  • Worse signal-to-noise ratio

No suitable equipment !


Current ventilation monitoring during CPAP

Indirect methods

  • Breathing belts (inductive (RIP), capacitive)
  • Transthoracic impedance
  • Pressure capsules


  • No influence on breathing (resistance, dead space)
  • Measurement of thoraco-abdominal synchrony


  • No reliable measurement of VT, V’E,…
  • No information about air leakages

Direct ventilatory measurements during CPAP


  • Oro- /nasopharyngeal tube
  • Endotracheal tube
  • Face mask
  • Binasal prongs
  • Head box
  • Benveniste valve
  • Infant Flow™ nCPAP System

Schmalisch G. Yearbook equipments and technology in NIPPV - 2009


Ventilation and leak flow

How we can separate breathing flow and leakage flow?

(Prerequisite for breath detection and ventilation measurements)


Bubble CPAP and variable leak flow

Under this conditions is the separation of breathing flow and leakage flow is a big challenge!


Quantification of the air leakage - 1

Schmalisch G. Year book of NIPPV 2009


Quantification of the air leakage - 2

The quantification of air leakages by the leak flow is more informative than by the currently use of percentages.


Relationship between air leakage and volume error

- modeling and in-vitro measurements -

Volume error

V`E - measured minute ventilation

maxV‘CPAP - maximal CPAP flow

Tin/Tex - inspiratory/expiratory time

Schmalisch G, et al. Med. Eng Phys. 31 (2009) 124-130

Fischer HS,, et al. Physiol. Meas. 29 (2008) 95-107


Clinical applications – 1

Hückstädt T et al. Intens. Care Med. 29 (2003) 1134-1140

Clinical cross-over study N=69

  • Comparison of Infant Flow system vs. Babylog 8000 by TB parameters
  • Custom-made equipment (Flow-Through Technique)
  • 49/69 (72%) infants excluded due to incompensable air leaks

Clinical applications – 2

Fischer HS, et al. Intens. Care Med. (2009) (in press)

Clinical cross-over study N=32

  • Air leaks during mononasal CPAP with and without nostril occlusion
  • Commercial Ventilator (Leoni M, Heinen&Löwenstein)
  • 11/32 (34.4%) infants excluded due to air leaks >90%

* After BTPS Correction

1) Schmalisch G, et al. BMC Pediatrics 2009


Effect of mouth opening on measured leak

Nasopharyngeal CPAP with occluded contralateral nostril

Fischer HS, et al. Intens. Care Med. 2009 (in press)


Clinical impact of air leakages during CPAP

Consequences of air leakages during nasal mask ventilation in adults

Rabec CA et al. Leak Monitoring in Noninvasive Ventilation. Arch Bronconeumol 2004;40(11):508-17

What is relevant for the CPAP treatment in newborns?



  • Monitoring of ventilation and air leakages during CPAP is much more difficult compared to mechanical ventilation
  • For most CPAP interfaces used in neonates no suitable measuring technique is available
  • Air leakages during CPAP (e.g. mouth leaks) are very common and should be quantified by the leak flow.
  • To which extent a breath detection (e.g. for CPAP triggering) and volume monitoring is possible in the presence of large air leakages is still unknown.
  • New clinical studies are necessary to investigate the effect of air leakages on the efficiency of the CPAP treatment.