by John Gever, Contributing Writer, MedPage Today October 17, 2023
SAN FRANCISCO -- Chinese researchers reported a simple but clever solution to the problem of how to facilitate non-dependent lung collapse during single-lung ventilation, which is needed for many types of thoracic surgery. Pneumatic Auto Drain Valve
Their innovation? A homemade "valve" they made from a cheap, thin plastic glove with the fingertips cut off, attached to the ventilation tube, as reported by Peng Liang, MD, of West China Hospital at the Sichuan University in Chengdu, at the American Society of Anesthesiologists annual meeting.
The issue, Liang explained, is that conventional setups for single-lung ventilation still allow some inflation of the non-dependent lung even after it's been collapsed. As the dependent lung is ventilated, the mediastinum moves and this may result in air intake into the other lung. Maintaining full collapse in the latter is vital in thoracic procedures, either to keep it out of the surgeon's way or, if the surgery is for pulmonary hemorrhage or infection, to prevent fluids from leaking into the non-dependent lung.
A unidirectional valve on the ventilation tube that allows air to be expelled from the non-dependent lung but that blocks intake would prevent this problem. That's where the glove comes in.
Whereas a normal ventilation system leaves the distal end of the non-dependent lung tube open to room air, Liang and colleagues decided to place their homemade valve over that end. On exhalation, air flows out unimpeded. But if the non-dependent lung tries to inflate, the negative pressure causes the thin plastic to collapse, preventing air intake.
Liang's group tested their DIY setup in 60 patients, half assigned to the valve and half to conventional ventilation. Outcomes included median time to lung collapse and to "satisfactory" lung collapse (lung collapse score 8 on a 10-point scale), which took longer.
Significant differences were seen between groups, not large in absolute terms but still clinically relevant, Liang indicated.
For detectable lung collapse, the median was 3 minutes with the valve in place versus 5 minutes without (P=0.003). For satisfactory lung collapse, the corresponding figures were 18 and 23 minutes (P=0.008).
Lung collapse scores over time once ventilation began also favored the valve, with differences of about 1 full point at 5 minutes and a half-point at 10 minutes.
No patients developed hypoxemia, either with the valve or without it. Pneumothorax occurred in one patient in the valve group. No other post-operative lung complications were recorded.
John Gever was Managing Editor from 2014 to 2021; he is now a regular contributor.
The study had no commercial funding. Authors declared they had no relevant financial interests.
Source Reference: Liang P, et al "Unidirectional valve apparatus improved non-dependent lung collapse during one-lung ventilation: a prospective randomized controlled trial" ASA 2023; Abstract A1202.
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