Clinical trial NCT01506284: Assessment of Airways Mechanical Properties by FOT and LIR During Anesthesia
Official title: Assessment of Airways Mechanical Properties by Forced Oscillatory Technique (FOT) and Laser Interferometry (LIR) During Anesthesia.
Study type: OBSERVATIONAL
Overall status: COMPLETED
Conditions: Anesthesia
Keywords: Forced oscillatory technique
Laser interferometry
Intravenous anesthesia
Mechanical ventilation
Pressure controlled ventilation
Airways mechanical properties
Respiratory system reactance
Oscillatory mechanics
Atelectasis
Lead sponsor: Uppsala University Hospital
Sponsor class: OTHER
Collaborators: name: Politecnico di Milano
First posted: 2012-01-09
Enrollment: 14
Sex: ALL
Minimum age (years): 18
Maximum age (years): 80
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Time perspective: PROSPECTIVE
Sampling method: PROBABILITY_SAMPLE
Study population: Patients ASA classification I-II, scheduled for elective surgery requiring general anesthesia

Brief summary: The aims of the present study are:

1. To evaluate the effect of the induction of anaesthesia and paralysis in terms of changes in oscillatory mechanics parameters
2. To evaluate the mechanical properties of the respiratory system in terms of input and transfer oscillatory impedance in response to PEEP changes

Detailed description: It has been recently shown that respiratory system reactance (Xrs) obtained by the forced oscillation technique (FOT) at 5 Hz is more reliable than dynamic compliance for assessing lung collapse and the effects of lung RMs in a porcine ALI model ( Ref.1,2).

Specifically, Xrs (and its derived variable CX5, the oscillatory compliance at 5 Hz) identifies the minimum positive end-expiratory pressure (PEEP) level required to maintain lung recruitment with high sensitivity and specificity. Moreover, it has been recently demonstrated that Xrs may be used to identify the lowest level of PEEP able to prevent atelectasis and that PEEP setting strategy based on maximizing Xrs is able to limit lung injury compared to oxygenation-based approach in a porcine lavage model of lung injury. ( Ref.3)

Recently, at the biomedical engineering department of Politecnico di Milano measurements of chest wall displacement have been successfully performed by means of an optical sensor realized using a laser self-mixing interferometer (LIR). The advantage of this approach is that it is contact-less, that by deflecting the laser been it is possible to scan any region of the chest wall surface and that it allows to measure also low-frequency vibrations.

Protocol

1. The baseline pulmonary function will be assessed by spirometry before surgery.
2. Just before surgery measurements of oscillatory mechanics will be performed at the following stages:

   * awake patient
   * spontaneous ventilation through the laryngeal mask after induction of anesthesia
   * pressure controlled ventilation (PCV) after the administration of neuromuscular blocking agent and intubation and PEEP 0 cmH2O
   * PCV with PEEP 5 cmH2O
   * Recruitment maneuver (RM) (peak pressure 30 cmH2O and PEEP 15 cmH2O) for 2 minutes
   * PCV with PEEP 5 cmH2O after RM

At each stage the following measurements will be performed:

* Input impedance at 5-11-19 Hz by FOT
* the movements of the chest wall assessed by laser interferometry (LIR) applying two different stimulating waveforms: 5-11-19 Hz and 100 Hz
* functional residual capacity (FRC)
* arterial blood gas measurement (ABG)

Eligibility criteria: Inclusion Criteria:

* age \>18 years
* ASA I-II, scheduled for elective surgery requiring general anesthesia
* signed informed consent

Exclusion Criteria:

* patient refusal
* BMI \> 35
* co-existing respiratory disease (COPD, asthma, restrictive lung disease)
* pregnancy

Primary outcomes:
measure: Change in respiratory system impedance
timeFrame: baseline and 5 minutes of ventilation
Secondary outcomes:
measure: Change in chest wall displacement measured by LIR
timeFrame: baseline and 5 minutes of ventilation
measure: Change in oxygenation (paO2)
timeFrame: baseline and 5 minutes of ventilation
measure: Change in Functional residual capacity (FRC)
timeFrame: baseline and 5 minutes of ventilation
Other outcomes:
Locations:
city: Uppsala
country: Sweden
facility: Uppsala University Hopsital, Dep. of Anesthesia and Intensive Care
Study officials:
affiliation: Uppsala University Hospital
name: Peter Frykholm, MD, PhD
role: PRINCIPAL_INVESTIGATOR
References:
citation: Dellaca RL, Andersson Olerud M, Zannin E, Kostic P, Pompilio PP, Hedenstierna G, Pedotti A, Frykholm P. Lung recruitment assessed by total respiratory system input reactance. Intensive Care Med. 2009 Dec;35(12):2164-72. doi: 10.1007/s00134-009-1673-3. Epub 2009 Sep 30.
citation: Dellaca RL, Zannin E, Kostic P, Olerud MA, Pompilio PP, Hedenstierna G, Pedotti A, Frykholm P. Optimisation of positive end-expiratory pressure by forced oscillation technique in a lavage model of acute lung injury. Intensive Care Med. 2011 Jun;37(6):1021-30. doi: 10.1007/s00134-011-2211-7. Epub 2011 Apr 1.
citation: Kostic P, Zannin E, Andersson Olerud M, Pompilio PP, Hedenstierna G, Pedotti A, Larsson A, Frykholm P, Dellaca RL. Positive end-expiratory pressure optimization with forced oscillation technique reduces ventilator induced lung injury: a controlled experimental study in pigs with saline lavage lung injury. Crit Care. 2011;15(3):R126. doi: 10.1186/cc10236. Epub 2011 Apr 28.