Pressure-controlled vs Volume Controlled Ventilation on RV Function During OLV
Condition: Lung Diseases
MeSH terms: Lung Diseases
Study type: Interventional
Phase: Phase 3

Summary: 
      The use of pressure controlled ventilation (TV) during one lung ventilation (OLV) for
      thoracic surgery is associated with comparable oxygenation with volume controlled ventilation
      (VCV) with added benefits of decreasing airway pressures and shunt fraction. The later may
      improve the right ventricular (RV) function during OLV. We postulate that the use of PCV
      during OLV for thoracic surgery would preserve RV function than during VCV. After local
      ethics committee approval and informed consent, we will randomly allocate 28 patients
      scheduled for elective thoracic surgery OLV to randomly crossed from PCV to VCV mode (n= 14
      for each) during with VT of 6 mL/kg, I: E ratio 1: 2.5, PEEP of 5 cm H2O, recruitment
      maneuvers and respiratory rate will be adjusted to maintain normocapnia. Intraoperative
      changes in the right ventricular function (peak systolic and diastolic tricuspid annular
      velocity (TAV), end-diastolic volume (EDV), end-systolic volume (ESV), and RV fractional area
      changes (RV-FAC)), hemodynamic and oxygenation parameters, peak and plateau airway pressures,
      compliance will be recorded.
    

Detailed description: 
      One-lung ventilation (OLV) provides excellent operative field for thoracic procedures, but is
      opposed by the harmful impairment of cardiac index and right ventricular (RV) function which
      may influence postoperative morbidity and mortality. In our previous study, we demonstrated
      significant reductions in RV ejection fraction (REF) and CI values after the initiation of
      OLV attributable to the increased right ventricular afterload, stroke work and end-diastolic
      volume augmented by increased airway pressures. This may be harmful with the patients with
      advanced obstructive lung diseases and those with pulmonary hypertension. Thus there is no
      doubt that decreases in airway pressures will be associated with better RV function.

      Volume controlled ventilation (VCV) is the commonly used traditional ventilation mode for OLV
      during thoracic procedures but its use is associated with deleterious increases in airway
      pressure which may impede RV function.

      Pressure controlled ventilation (PCV) is an alternative mode of ventilation which is widely
      used in the patients with acute respiratory distress syndrome (ARDS) and acute lung injury
      (ALI), whereby high initial flow rates are delivered to quickly achieve and maintain the set
      inspiratory pressure followed by rapidly decelerating flow.These high initial flow rates lead
      to a more rapid alveolar inflation.

      PCV has been suggested as a useful tool to improve oxygenation as well as decreases in
      intra-pulmonary shunt (Qs/Qt) and airway pressures compared with VCV during OLV for patients
      undergoing thoracic surgery. Whereas, others demonstrated comparable arterial oxygenation
      with the use of PCV and VCV during OLV.

      However, the use of PCV offers advantages over VCV during OLV in the term of reducing mean
      and bronchial peak airway pressures and intrapulmonary shunt, hence limiting the risk for
      barotrauma and impaired RV function.

      Up to the investigators knowledge, there is no available study of the effects of PCV and VCV
      on RV function during OLV after thoracic surgery.

      The investigators hypothesize that the use of PCV during OLV will be associated with
      preserved RV function than during the use of VCV. They will compare the effects of the use of
      PCV and VCV with 5 cm H2O level of PEEP and recruitment maneuvers during OLV on the right
      ventricular function (peak systolic and diastolic tricuspid annular velocity (TAV),
      end-diastolic volume (EDV), end-systolic volume (ESV), and RV fractional area changes
      (RV-FAC)), hemodynamic parameters (heart rate (HR), mean arterial blood pressure, (MAP)),
      oxygenation parameters (arterial oxygen and carbon dioxide tension (PaO2 and PaCO2,
      respectively), and arterial tension to inspired fraction of oxygen (PaO2/FiO2) ratio),
      ventilation parameters (peak and plateau airway pressures (Ppk and Ppl, respectively) and
      compliance) and the ICU and hospital length-of-stays, morbidity and 30-day mortality.

      Sample size calculation:

      A priori power analysis of the previous published data11 showed that the investigators will
      need to study 13 pairs to detect a 20% difference in the mean maximal systolic TAV values
      (7.0 cm/s) with a SD of 1.4 cm/s, after start of OLV, a type-I error of 0.05 and a power of
      90%. We will add 10% more patients for a final sample size of 28 patients to account for
      patients dropping out during the study.

      Interventions:

      In all patients, standard monitors will be applied. A thoracic epidural or paravertebral
      catheter will be inserted with no more use of local anesthetics during the study to avoid
      their effects on hypoxic pulmonary vasoconstriction.12 An arterial line (20 G) and a right
      internal jugular vein catheter will be inserted. Anesthetic technique will be standardized in
      all studied patients. Anesthesiologists who will give the anaesthetic will be not involved in
      the patient's assessment. General anesthesia will be induced with propofol (2-3 mg/kg),
      fentanyl (2-3 µg/kg), and cisatracurium (0.2 mg/kg) will be given to facilitate tracheal
      intubation with a left-sided double-lumen tube (DLT). The correct position of its tip will be
      confirmed with a fiberoptic bronchoscope. Anesthesia will be maintained with 1-1.5 minimum
      alveolar concentration (MAC) of sevoflurane and increments of fentanyl (0.5µg/kg) and
      cisatracurium (0.04 mg/kg).

      The patients' lungs will be mechanically ventilated using VCV mode, fraction of inspired
      oxygen (FiO2) of 0.5 in air, tidal volume (VT) of 8 mL/kg (predicted body weight),
      inspiratory to expiratory [I: E] ratio of 1:2.5, a positive end-expiratory pressure (PEEP) of
      5 cm H2O, respiratory rate (R.R) will be adjusted to achieve an PaCO2 of 35-45 mm Hg, peak
      inspiratory pressures (Ppk) will be limited to 35 cm H2O and a low fresh gas flow (FGF) (<2
      L/min) in a semi closed circuit system.

      Transesophageal echocardiography (TEE) will be inserted and the right ventricular function
      will be assessed with the measurements of EDV, ESV, RVEF, both maximal systolic and diastolic
      TAV at the tricuspid annulus at the RV free wall recorded from the apical 4-chamber views
      using pulsed wave Doppler tissue imaging.

      All operations will be performed by the same surgeons. Intraoperative hypoxemia will be
      defined as decrease in arterial oxygen saturation less than 90% will be treated with
      increasing of FiO2 to 1.0. Addition of low level of 2 cm H2O of CPAP will be considered if
      the later fails to correct hypoxemia. 1 Intraoperative fluid therapy will include intravenous
      infusion of 2 ml/kg/hour of Lactated Ringer's solution and blood losses will be compensated
      with colloids and with red blood cell concentrates if the hemoglobin levels decreases below 8
      to 9 g/dL. Mean arterial blood pressure will be maintained greater than 60 mm Hg using bolus
      doses of ephedrine 5 mg or phenylephrine 100 ug. Urine output will be maintained to be
      greater than 0.5 ml/kg/hour.

      At the end of surgery, the nondependent will be re-expanded and TLV will be resumed as before
      surgery, sevoflurane will be discontinued, the residual neuromuscular block will be
      antagonized, and the patient will be extubated. Postoperative analgesia will be accomplished
      with the use of continuous epidural/paravertebral infusion of bupivacaine 0.125% and fentanyl
      2 µg/mL.

      Statistical Analysis:

      Data will be tested for normality using the Kolmogorov-Smirnov test. Fisher exact test will
      be used for categorical data. Repeated two-way ANOVA and paired t-test will be used to study
      the changes in the primary and secondary endpoints during each intervention. The Wilcoxon 2
      rank sum test will be used for the non-parametric values. We will avoid the carryover effect
      (persistence of the effect of the first intervention on the operative conditions into the
      second period) through the comparison of the effects of period (time effect) and the order of
      treatment using independent t-tests. Data will be expressed as mean ± SD, number (%), or
      median [range]. A value of P < 0.05 will be considered to be statistically significant.
    

Intervention name(s): The PCV-VCV group; The VCV-PCV group
Intervention type(s): Other; Other
Intervention description(s): During the PCV period, the inspiratory pressure will be adjusted to deliver a TV of 6 mL/kg (predicted body weight) to the patient's dependent lung. During the VCV period, the patient's dependent lung will be ventilated with a TV of 6 mL/kg (PBW). Whereas FiO2, I: E ratio, PEEP, frequency, Ppk, and a FGF will be maintained as during two-lung ventilation (TLV) and the lumen of the nondependent lung will be left open to air. Dependent lung recruitment maneuvers will be repeated at 30-minute intervals by raising the inspiratory pressure up to 35 cmH2O for 10 seconds.; During the PCV period, the inspiratory pressure will be adjusted to deliver a TV of 6 mL/kg (predicted body weight) to the patient's dependent lung. During the VCV period, the patient's dependent lung will be ventilated with a TV of 6 mL/kg (PBW). Whereas FiO2, I: E ratio, PEEP, frequency, Ppk, and a FGF will be maintained as during two-lung ventilation (TLV) and the lumen of the nondependent lung will be left open to air. Dependent lung recruitment maneuvers will be repeated at 30-minute intervals by raising the inspiratory pressure up to 35 cmH2O for 10 seconds.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Double (Investigator, Outcomes Assessor)
Primary purpose: Treatment
Keywords: Thoracic surgery; one lung ventilation; pressure-controlled ventilation; volume-controlled ventilation; right ventricular function