ORIGINAL ARTICLE Ultrasound lung ‘‘comets’’ increase after breath-hold diving Kate Lambrechts • Peter Germonpre ´ • Brian Charbel • Danilo Cialoni • Patrick Musimu • Nicola Sponsiello • Alessandro Marroni • Fre ´de ´ric Pastouret • Costantino Balestra Accepted: 11 October 2010 / Published online: 23 October 2010 Ó Springer-Verlag 2010 Abstract The purpose of the study was to analyze the ultrasound lung comets (ULCs) variation, which are a sign of extra-vascular lung water. Forty-two healthy individuals performed breath-hold diving in different conditions: dynamic surface apnea; deep variable-weight apnea and shallow, face immersed without effort (static maximal and non-maximal). The number of ULCs was evaluated by means of an ultrasound scan of the chest, before and after breath-hold diving sessions. The ULC score increased sig- nificantly from baseline after dynamic surface apnea (p = 0.0068), after deep breath-hold sessions (p = 0.0018), and after static maximal apnea (p = 0.031). There was no statistically significant difference between the average increase of ULC scores after dynamic surface apnea and deep breath-hold diving. We, therefore, postulate that extravascular lung water accumulation may be due to other factors than (deep) immersion alone, because it occurs during dynamic surface apnea as well. Three mechanisms may be responsible for this. First, the immersion-induced hydrostatic pressure gradient applied on the body causes a shift of peripheral venous blood towards the thorax. Second, the blood pooling effect found during the diving response Redistributes blood to the pulmonary vascular bed. Third, it is possible that the intense involuntary diaphragmatic con- tractions occurring during the ‘‘struggle phase’’ of the breath-hold can also produce a blood shift from the pul- monary capillaries to the pulmonary alveoli. A combination of these factors may explain the observed increase in ULC scores in deep, shallow maximal and shallow dynamic apneas, whereas shallow non-maximal apneas seem to be not ‘‘ULC provoking’’. Keywords Apnea Á Extravascular lung water Á Edema Á Hypoxia Á Static Á No-limits Á Underwater swimming Introduction Capillary stress failure inducing lung water accumulation may occur in otherwise healthy individuals as a result of exposure to environmental stress (West and Mathieu- Costello 1995a), as well as during underwater immersion (Koehle et al. 2005; Slade et al. 2001). The prevalence of lung water accumulation (acute pul- monary edema) during immersion was reported and studied previously during scuba-diving or swimming (Hampson and Dunford 1997; Pons et al. 1995; Weiler-Ravell et al. 1995; Wilmshurst et al. 1989). The occurrence of pul- monary edema in swimmers and divers was reported for the first time by Wilmshurst and co-workers. These Communicated by Guido Ferretti. K. Lambrechts Á P. Germonpre ´ Á B. Charbel Á D. Cialoni Á P. Musimu Á N. Sponsiello Á A. Marroni Á F. Pastouret Á C. Balestra (&) Environmental & Occupational Physiology Laboratory, Haute Ecole Paul-Henri Spaak, 91, Avenue Charles Schaller, 1160 Auderghem, Brussels, Belgium e-mail: balestra@daneurope.org P. Germonpre ´ Center for Hyperbaric Oxygen Therapy, Military Hospital, Brussels, Belgium P. Germonpre ´ Á D. Cialoni Á P. Musimu Á N. Sponsiello Á A. Marroni Á C. Balestra Apnea Academy/Dan Europe Research Task Force, Brussels, Belgium F. Pastouret Department of Rehabilitation Research, Vrije Universiteit Brussel, Brussels, Belgium 123 Eur J Appl Physiol (2011) 111:707–713 DOI 10.1007/s00421-010-1697-y