Ventilation Strategy Reduces Postoperative Atelectasis

Region Västmanland

Status: Withdrawn

Conditions: Pulmonary Atelectasis

Treatments: Procedure: No CPAP/PEEP and 100 % oxygen; Procedure: CPAP/PEEP and 30 % oxygen

Study type: Interventional

Funder types: Other

Identifiers

NCT01911923

Dnr 2008 / 251

Details and patient eligibility

About

Atelectasis is common during and after general anesthesia. The investigators hypothesized that a ventilation strategy with a combination of 1) continuous positive airway pressure (CPAP) or positive end-expiratory pressure (PEEP) and 2) a reduced end-expiratory oxygen fraction (FETO2) before commencing mask ventilation with CPAP after extubation would reduce the area of postoperative atelectasis.

Full description

During general anesthesia, the combination of reduced functional residual capacity (FRC), high inspiratory oxygen fraction (FIO2), and airway closure are the main factors implicated in the atelectasis, shunt and shunt-like effects that account for the majority of the impaired oxygenation seen during general anesthesia.

Previous studies have shown that formation of atelectasis during preoxygenation and induction of anesthesia can be avoided by adding a continuous positive airway pressure (CPAP) followed by a positive end-expiratory pressure (PEEP).During emergence from anesthesia, high concentrations of oxygen predispose to atelectasis formation. Even a recruitment maneuver, followed by ventilation with 100% oxygen with a PEEP/CPAP of 10 cm H2O until extubation, failed to improve postoperative oxygenation compared with that achieved with zero end-expiratory pressure (ZEEP).This failure may have been caused by the presence of lung regions with high oxygen concentrations.

The investigators hypothesized that by inducing and discontinuing anesthesia during CPAP/PEEP and deliberately reducing FIO2 after extubation, postoperative atelectasis would be reduced compared with standard protocols. To test our hypothesis, the investigators studied 1) a control group with no CPAP/PEEP and a FIO2 of 1.0 while breathing spontaneously after extubation, and 2) an intervention group that was on CPAP/PEEP of 6 cmH2O from induction to extubation and that received an FIO2 of 1.0 until extubation and then an FIO2 of 0.3 via a facemask while on CPAP after extubation.

Sex: All

Ages: 20 to 75 years old

Volunteers: No Healthy Volunteers

Inclusion criteria

1. Adult patients up to 75 years of age.
2. American Society of Anesthesiologists (ASA) physical status class I-III.
3. Be able to climb two flight of stairs without stopping.
4. SpO2 of ≥ 94% when breathing air in the supine position.
5. A body mass index (BMI, weight in kilograms divided by the square of the height in meters) of < 31.

Exclusion criteria

1. Patients with chronic obstructive pulmonary disease.
2. Smokers.
3. Ex smokers if smoked more than 5 pack years.
4. Overt heart failure
5. Known or predicted difficult intubation.

Trial design

Primary purpose: Treatment

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: Double Blind

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0 participants in 2 patient groups

No CPAP/PEEP and 100 % oxygen

Active Comparator group

Description:

This is the control group

Treatment:

Procedure: No CPAP/PEEP and 100 % oxygen

CPAP/PEEP and 30 % oxygen

Experimental group

Description:

This is the intervention group

Treatment:

Procedure: CPAP/PEEP and 30 % oxygen