Effect of ultrasound-guided–pressure-controlled ventilation on intraoperative blood gas and ventilatory parameters during thoracic surgery

BACKGROUND AND AIMS: Identifying an ideal intraoperative ventilation strategy remains an area of research. We evaluated the effect of ultrasound-guided–pressure-controlled ventilation (UG-PCV) on the blood-gas and ventilatory parameters, during both two-lung ventilation (TLV) and one-lung ventilation (OLV) for thoracic surgery of unilateral pulmonary disease, compared with volume-targeted PCV (VT-PCV). METHODS: In a prospective, parallel-group and double-blinded design, 40 consecutive patients were randomised into two groups. Group A: Received VT-PCV at a tidal volume (TV) of 9 mL/kg for TLV and 5 mL/kg for OLV; group B: Received UG-PCV at an inspiratory pressure (2 cmH(2)O increments every 15 s) targeted to achieve the alveolar aeration at the base of the dependent lung (ultrasound-guided), for both TLV/OLV, respectively. Primary outcome included arterial oxygen partial pressure (PaO(2)) measured at baseline before anaesthesia induction (T1), at 30 min immediately before conversion from TLV to OLV (T2), at 30 min on OLV (T3) and before terminating OLV at the end of surgery (T4). Statistical tool included Mann-Whitney test. RESULTS: The PaO(2) (mmHg) was significantly higher in group B (374.5 ± 25.9, 321.7 ± 35.2 and 357.0 ± 24.7) as compared to group A (353.3 ± 38.1, 272.6 ± 37.9 and 295.3 ± 40.1), at T2, T3 and T4, respectively. The acid-base status remained preserved in group B, while gradual respiratory acidosis was observed in group A. The bicarbonate levels remained uniform in all patients. The TV and airway pressures were marginally higher in group B, with no intraoperative complications. CONCLUSION: The UG-PCV mode offered better oxygenation, homogenous acid-base balance and individualised alveolar ventilation for thoracic surgery.