Pulmonary barotrauma of descent (lung squeeze) has been described
in breath-hold divers when the lung volume becomes smaller than the
residual volume (RV), with the effect of increased ambient pressure.
However, the ratio between the total lung capacity and the RV is not
the only factor that plays a role in the lung squeeze. Blood shift into
the thorax is another important factor. We report three cases of
hemoptysis in breath-hold divers who dove for spear fishing in
shallower depths than usual. All of the divers performed voluntary
diaphragmatic contractions at the beginning of their ascent, while
their mouths and noses were closed. We suggest that the negative
intrathoracic pressure due to the forced attempt to breathe in with
voluntary diaphragmatic contractions contributes to alveolar
hemorrhage, since it may damage the pulmonary capillaries.