Assessment of lung recruitment with continuous negative extrathoracic pressure after one-lung ventilation: an experimental investigation

Abstract

Background: Lung recruitment manoeuvres following one-lung ventilation (OLV) have the potential to induce lung injury. Application of continuous negative extrathoracic pressure ventilation (CNEP) for lung recruitment has yet to be explored. We investigated the effects of CNEP following OLV on lung expansion, gas exchange, and haemodynamics.

Methods: An endotracheal blocker was inserted in 10 anesthetized pigs (45±0.5 kg) and OLV was ensured with pressure-regulated volume control mode (PRVC) (FiO₂: 0.5, respiratory rate: 30-35/min, tidal volume (VT): 5 ml/kg, positive end-expiratory pressure: 5 cmH₂O). Electrical impedance tomography, blood gas, cardiac output (CO) and extravascular lung water (EVLW) were measured after 1 hour of OLV. Double-lung ventilation was then started, combining PRVC (VT: 7 ml/kg) and CNEP (-15 cmH₂O) without active recruitment of the collapsed lung beforehand and measurements were repeated at 5 minutes and 1 hour.

Results: Five minutes following initiation of CNEP oxygenation and CO₂ elimination improved (154.1±13.3 vs 173.8±22.1 mmHg and 52.6±11.7 vs 40.3±4.5 mmHg, p<0.05 respectively) and lung aeration increased in the non-collapsed lung (p<0.05). After an hour of CNEP, no additional improvement in gas exchange was noted despite increase in aeration of the collapsed lung (p<0.05). CO and EVLW remained stable under CNEP.

Conclusions: Application of CNEP in the presence of whole lung atelectasis proved to be efficient in recruiting the lung without inducing lung oedema. Combining CNEP to positive pressure ventilation may offer beneficial effects at reducing atelectasis following lung collapse during thoracic procedures.