Figure 4.

Spirogram from the real-time monitoring of the breathing pattern showing the varying instant effect of laughter on the end-expiratory lung volume (EELV) in patients with COPD. Intense laughter can lead to dynamic hyperinflation in some patients with severe COPD (panel A). Most of the times there was no significant change in the EELV due to a single fit of laughter (panel B). In some instances, particularly as a consequence of smiling, the EELV markedly diminished (panel C). Smiling was able to reduce the EELV in both COPD and controls – at least as an instant effect.