Ventilation Distribution After Bariatric Surgery

University of Trieste

Status: Completed

Conditions: Bariatric Surgery Candidate; Atelectasis, Postoperative Pulmonary

Treatments: Device: Continuous positive airway pressure; Device: High flow nasal cannula; Device: Facemask

Study type: Interventional

Funder types: Other

Identifiers

NCT03975348

123/2018

Details and patient eligibility

About

Obese patients have an increased risk of developing post-operative respiratory complications due to their comorbidities. They have a restrictive ventilatory defect with reduction of lung volumes and expiratory flow limitation, higher airway resistance and collapsibility of the upper respiratory tract. These abnormalities are worsened by general anesthesia and opioid administration. It has been proved that oxygen therapy with HFNC (high flow nasal cannula) increases lung volumes through a continuous positive airway pressure (CPAP)-effect. This also improves gas exchange and decreases anatomical dead space. At the present time, CPAP represents the gold standard for the prevention of postoperative pulmonary complications. The purpose of this study is to evaluate lung ventilation, gas exchange and comfort with HFNC compared with CPAP during the post-operative period in patients who undergo laparoscopic bariatric surgery.

Full description

Immediately after bariatric surgery, patients will follow a pre-determined schedule of oxygen therapy with conventional facemask (from the beginning to minute 10), HFNC (with a flow of 40 L/min from minute 11 to 20, 60 L/min from minute 21to 30, 80 L/min from minute 31 to 40, 100 L/min from minute 41 to 50, 80 L/min from minute 51 to 60, 60 L/min from minute 61 to 70, 40 L/min from minute 71 to 80), conventional facemask again (washout, from minute 81 to 90) and CPAP (10 cmH2O, from minute 91 to 100). Lung ventilation will be evaluated with electrical impedance tomography (EIT), which measures thoracic impedance variations related to changes in lung aeration. At the end of each 10 minutes-period the following data will be collected: electrical impedance tomography data (to calculate the global inhomogeneity index, Δ end-expiratory lung impedance and tidal impedance variation), hemodynamic parameters, respiratory rate, SpO2, pain (numerical rating scale), level of sedation (Ramsey score) and patient comfort (modified Borg scale). An arterial blood gas will be collected at the end of the following steps: baseline facemask, HFNC 40 and 100 L/min, washout facemask and CPAP. Data about anesthetic/analgesic drugs and ventilation parameters will also be collected.

Enrollment: 15 patients

Sex: All

Ages: 18+ years old

Volunteers: No Healthy Volunteers

Inclusion criteria

• Patient's consent to the trial
• Candidate to laparoscopic bariatric surgery (sleeve gastrectomy or Roux-en-Y gastric bypass)
• BMI 35-50 kg/m2
• ASA class 1-3

Exclusion criteria

• Obesity hypoventilation syndrome
• Contraindication to EIT (e.g. implantable cardioverter-defibrillator)

Trial design

Primary purpose: Treatment

Allocation: Non-Randomized

Interventional model: Crossover Assignment

Masking: None (Open label)

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15 participants in 10 patient groups

Baseline conventional facemask

Other group

Description:

The patients will receive oxygen therapy through conventional facemask for 10 minutes

Treatment:

Device: Facemask

HFNC 40 L/min up

Experimental group

Description:

The patients will receive oxygen/air mixture through high flow nasal cannula at incremental, then decremental flows, starting at 40 L/min for 10 minutes

Treatment:

Device: High flow nasal cannula

HFNC 60 L/min up

Experimental group

Description:

High flow nasal cannula at 60 L/min for 10 minutes

Treatment:

Device: High flow nasal cannula

HFNC 80 L/min up

Experimental group

Description:

High flow nasal cannula at 80 L/min for 10 minutes

Treatment:

Device: High flow nasal cannula

HFNC 100 L/min

Experimental group

Description:

High flow nasal cannula at 100 L/min for 10 minutes

Treatment:

Device: High flow nasal cannula

HFNC 80 L/min down

Experimental group

Description:

High flow nasal cannula at 80 L/min for 10 minutes

Treatment:

Device: High flow nasal cannula

HFNC 60 L/min down

Experimental group

Description:

High flow nasal cannula at 60 L/min for 10 minutes

Treatment:

Device: High flow nasal cannula

HFNC 40 L/min down

Experimental group

Description:

High flow nasal cannula at 40 L/min for 10 minutes

Treatment:

Device: High flow nasal cannula

Washout conventional facemask

Other group

Description:

Again, the patients will receive oxygen therapy through conventional facemask for 10 minutes, to reduce the influence of HFNC on CPAP therapy

Treatment:

Device: Facemask

CPAP

Active Comparator group

Description:

The patients will receive CPAP at 10 cmH2O for 10 minutes

Treatment:

Device: Continuous positive airway pressure