The importance of an inspiratory hold and a prolonged inspiratory ramp for the detection of bronchopleural leaks in an model.

BACKGROUND

Before the chest is closed, the airtightness of the remaining lung is regularly checked after anatomical and non-anatomical lung resections. The thoracic cavity is filled with sterile water and the lungs are reventilated with a peak inspiratory pressure (Pinsp) of +25 mbar at a positive end-expiratory pressure (PEEP) of +5 mbar. The surgeon inspects the surface of the lung, especially the sutures, for leaks. In the event of a leak, air escapes in varying amounts; this can range from individual air bubbles to a massive leak of air. At this stage, the surgeon is still able to take corrective measures. Methods range from suturing to covering the leak site with a collagen fleece. An overlooked leak usually has serious consequences. Despite the leak test described above, air leaks continue to occur postoperatively. This study on pig lungs aims to investigate whether an air leak can be better unmasked by extending the inspiration in the form of a ramp or by maintaining Pinsp for 5 seconds ("inspiratory hold").

METHODS

Heart-lung packages removed from freshly slaughtered pigs (weight: 90 kg) were connected to a ventilator via a tracheally inserted tube. Compared to the standard leak test (Pinsp = +25 mbar, PEEP = +5 mbar, frequency 10 1/min), two groups of n=15 each were examined. Group 1: inspiratory ramp 2.0 and group 2: "inspiratory hold" for 5 seconds at an inspiratory pressure of +25 mbar. Air tightness of lung lesions (diameter: 1 cm) with a depth of 0.8 and 1.8 cm was examined. A group comparison was performed using a nonparametric Mann-Whitney test (P<0.05).

RESULTS

The comparison of the standard group versus the ramp group was not significant at a lesion depth of 0.8 cm after 1 minute (P=0.07). This also applies to a lesion depth of 1.8 cm (P=0.09). After 5 minutes, the standard group showed significantly better recognition compared to the ramp group at both 1 and 5 minutes (P=0.03 and P=0.03). When comparing the standard group to the "inspiratory hold", this group showed a highly significant detection of air leaks, particularly in lesions measuring 0.8 cm. This result was not as distinct for the deeper lesion. After an observation period of 5 minutes, the "inspiratory hold" group was nevertheless superior to the standard group at both lesion depths (P=0.008 and P=0.02).

CONCLUSIONS

The intraoperative detection of air leaks from the lung parenchyma can be improved by an "inspiratory hold" maneuver compared to the standard approach.