Introduction: Changes of intra-thoracic pressures may affect cardiac function . The aim of the present study was to evaluate the impact of negative pressure ventilation (NPV) by means of a cuirass ventilator on diastolic function of the left ventricle in patients (pts) undergoing laser therapy (LT) of lesions obstructing the airways tract.
Method: Six consecutive pts scheduled for elective LT were enrolled. Intraoperative monitoring consisted of two-leads ECG, NIBP, pulse-oximetry, ET-CO2 Anaesthesia was performed by TCI of propofol at 1.5-2 μg mL−1 plasma target, fentanyl 50-100 μg, atracurium 0.3mg/Kg. Ventilation was performed by applying a negative pressure of 60-80 mmHg to the anterior wall of the thorax through a cuirass at a rate of 12-14 cycles min−1 with a NEV-100 ventilator.
At the end of the surgical procedure an omniplane transoesophageal echo probe was introduced in all pts. A study of LV function was then performed under NPV. We registered the LV propagation velocity (Vp) by colour M-mode, the early diastolic velocity of mitral annulus by Tissue Doppler, and the end diastolic area (EDA) in the transgastric mid-papillary view. Pts were then brought to spontaneous ventilation, and after 5-10min the echo parameters were registered again. Echo data under spontaneous and negative ventilation were compared. Statistical analysis was performed with Student's t test (P < 0.05).
Results: Under NPV colour M-mode, evaluation showed an increase of Vp (from 38 ± 5.8 to 48 ± 13.1 cm/sec, P < 0.05) when compared with data under spontaneous ventilation. Early diastolic velocity of mitral annulus by Tissue Doppler was higher under NPV (9.2 cm sec−1 vs. 8.3cm sec−1 under spontaneous ventilation, P < 0.05), and EDA was larger during NPV (13.8 cm2 vs. 11.6cm2, P < 0.05). Blood gas data showed a decrease of pH (from 7.44 ± 0.05 to 7.35 ± 0.05), an increase of PO2 (from 78.7 ± 35 to 118.6 ± 40) and of PCO2 (from 39.2 ± 8 to 49.8 ± 2).
Discussion: NPV is a safe and feasible method for the management of lung ventilation during LT, although in a small group of patients, our preliminary experience showed that NPV may positively affect LV diastolic function. Being aware that a larger experience is necessary, we conclude that NPV seems to be a promising method of ventilation even in cardiac patients with diastolic impairment.
1 Ambrosino N, Cobelli F, Torbicki A, et al. Hemodynamic effects of negative-pressure ventilation in patients with COPD. Chest