Comment to: Pulmonary gas exchange after foam sclerotherapy (Research letter), by Moro L, Rossi Bartoli I, Cesari M, Scarlata S, Serino F-M, Antonelli Incalzi R. JAMA Dermatol 2014;150:207-9.

A venous gas microembolization should lead to some loss of gas exchange surface, with consequent gas exchange abnormalities and reduction in the transfer factor of the lung for carbon monoxide (TLCO). Aim of this proof-of-concept study was to verify whether TLCO worsens after foam sclerotherapy (FS) treatment.
Eleven consecutive voluntary patients [7 women and 4 men, mean age of 64 (SD=12) years], scheduled to undergo FS for varicose veins, were enrolled in the study. The patients (7 women and 4 men) had mean age of 64 (SD=12) years. Respiratory function tests (RFT) were performed after an overnight fasting and 24 h smoke-free using a Baires computerized system. The following parameter were obtained and adjusted for hemoglobin concentration: TLCO, CO diffusion index (through alveolus-capillary barrier), and kCO (i.e., TLCO adjusted for alveolar volume). FS was performed mixing 1% polidocanol with physiological gas (70% CO₂, 30% O₂). The mean volume of injected foam was 6 cc (standard deviation, SD=2.82) in SSV (2 cases) and 6.25 cc (SD=1.67) in GSV (9 cases).
The timetable of the study was: General clinical assessment; After 10 min, RFT (time 0, T0); After 10 min, sclerotherapy; After 20 min, RFT (time 1, T1); After 7 days, RFT (time 2, T2). None of the patients reported adverse events of the FS. No statistically significant difference across study time-points was reported for RFT (all P values >0.05). Lung bubble microembolism seems unlikely to complicate FS, at least if a CO₂/O₂-based mixture (less emboligen than an air-based mixture) is used. It is possible that gas exchange modifications may occur in case of major respiratory alterations. However, the TLCO parameter we adopted, is highly sensitive even to clinically silent modifications. In conclusion, bubble microembolism either is not a typical effect of FS or only minimally impact on gas exchanges. Other mechanisms may be accounted for FS-related respiratory adverse effects.