Atelectasis, Oxygenation
Conditions
Keywords
Atelectasis, Oxygenation, Positive end-expiratory pressure, Mechanical ventilation, General anesthesia, Computed tomography
Brief summary
A study on healthy patients undergoing anesthesia for non-abdominal surgery - evaluation of positive end-expiratory pressure versus zero positive end-expiratory pressure on the amount of atelectasis in the early postoperative period.
Detailed description
Positive end-expiratory pressure (PEEP) is often used during mechanical ventilation to preserve end-expiratory lung volume. After emergence and extubation, this volume will diminish instantly. Some patients will have difficulties to restore functional residual capacity (FRC) during the early phase of recovery. If routine high FIO2 has been delivered together with maintained PEEP prior to extubation, several important prerequisites are established for the development of postoperative atelectasis. The investigators hypothesize that establishing zero positive end-expiratory pressure (ZEEP) immediately prior to emergence preoxygenation, will prevent gas with high oxygen concentration from entering dorso-basal areas of the lungs, and thereby prevent postoperative atelectasis formation. This randomized controlled study will study patients undergoing non-abdominal day case surgeries under general anesthesia. The patients in the two study groups will receive mechanical ventilation with identical settings, comprising low TV, moderate PEEP, and no RM. At the end of surgery, the lungs will be examined by CT, and any atelectasis areas will be calculated. Randomization will occur after the first CT. The patients will be allocated to zero PEEP (ZEEP) or maintained PEEP during emergence preoxygenation and extubation. Importantly, the intervention group will have ZEEP established while still having low ETO2 levels, prior to any preoxygenation. The study subjects will be examined with CT no.2 approximately thirty min after extubation. Primary endpoint measure will be atelectasis area as a percentage of total lung area. Blood gases will be collected for comparison of oxygenation as a secondary outcome measure.
Interventions
PROCEDUREPEEP
Positive end-expiratory pressure remains during emergence preoxygenation and awakening and until the study subject is extubated.
PROCEDUREZEEP
Zero positive end-expiratory pressure (ZEEP) during emergence preoxygenation and awakening.
Sponsors
Region Västmanland
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
PREVENTION
Masking
DOUBLE (Subject, Outcomes Assessor)
Masking description
Sealed envelopes.
Eligibility
Sex/Gender
ALL
Age
40 Years to 75 Years
Healthy volunteers
No
Inclusion criteria
* American Society of Anesthesiology (ASA) class I-II * Non-abdominal day case surgery under general anesthesia
Exclusion criteria
* Body mass index (BMI) ≥30 kg/m2 * Arterial oxygen saturation (SpO2) breathing air \<95 % * Chronic Obstructive Pulmonary Disease (COPD) or symptomatic asthma * Symptomatic congestive heart failure * Ischemic heart disease * Hemoglobin \<100 g/L * Active smokers * Active smokers and ex-smokers with a history of more than 6 pack years. * Need for interscalene or supraclavicular plexus block for postoperative pain relief (risk of phrenic nerve paralysis).
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Change in atelectasis area | Within 3 hours from induction of anesthesia. First CT after surgery, before emergence. Second CT approx 25 min after extubation. Study complete after that, no further CT. | Atelectasis area as studied by computed tomography. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Change in oxygenation | Within 3 hours from induction of anesthesia. First blood gas after surgery, before emergence. Second approx 25 min after extubation. Study complete after that, no further blood gases. | Arterial blood samples will be collected for measurement of arterial oxygen partial pressure. |
Countries
Sweden
Outcome results
None listed