title: Spleen and cardiovascular function during short apneas in divers.
abstract: We investigated the spleen volume changes as related to the cardiovascular responses during short-duration apneas at rest. We used dynamic ultrasound splenic imaging and noninvasive photoplethysmographic cardiovascular measurements before, during, and after 15-20 s apneas in seven trained divers. The role of baroreflex was studied by intravenous bolus of vasodilating drug trinitrosan during tidal breathing. The role of lung volume was studied by comparing the apneas at near-maximal lung volume with apneas after inhaling tidal volume, with and without cold forehead stimulation. In apneas at near maximal lung volume, a 20% reduction in splenic volume (P = 0.03) was observed as early as 3 s after the onset of breath holding. Around that time the heart rate increased, the mean arterial pressure abruptly decreased from 89.6 to 66.7 mmHg (P = 0.02), and cardiac output decreased, on account of reduction in stroke volume. Intravenous application of trinitrosan resulted in approximately 6-mmHg decrement in mean arterial pressure, while the splenic volume decreased for approximately 13%. In apneas at low lung volume, the early splenic contraction was also observed, 10% without and 12% with cold forehead stimulation, although the mean arterial pressure did not change or even increased, respectively. In conclusion, the spleen contraction is present at the beginning of apnea, accentuated by cold forehead stimulation. At large, but not small, lung volume, this initial contraction is probably facilitated by downloaded baroreflex in conditions of decreased blood pressure and cardiac output.
authors.affiliation: Department of Physiology, University of Split School of Medicine, Split, Croatia.
authors.forename: Ivan
authors.initials: I
authors.lastname: Palada
authors.forename: Davor
authors.initials: D
authors.lastname: Eterovic
authors.forename: Ante
authors.initials: A
authors.lastname: Obad
authors.forename: Darija
authors.initials: D
authors.lastname: Bakovic
authors.forename: Zoran
authors.initials: Z
authors.lastname: Valic
authors.forename: Vladimir
authors.initials: V
authors.lastname: Ivancev
authors.forename: Mihajlo
authors.initials: M
authors.lastname: Lojpur
authors.forename: J Kevin
authors.initials: JK
authors.lastname: Shoemaker
authors.forename: Zeljko
authors.initials: Z
authors.lastname: Dujic
mesh_terms: D000328:Adult; D001049:Apnea / Q000000981:diagnostic imaging / Q000503:physiopathology*; D017704:Baroreflex; D001794:Blood Pressure; D002302:Cardiac Output; D002319:Cardiovascular System / Q000187:drug effects / Q000294:innervation / Q000503:physiopathology*; D003080:Cold Temperature; D004242:Diving; D006339:Heart Rate; D006801:Humans; D007275:Injections, Intravenous; D008168:Lung / Q000503:physiopathology; D008176:Lung Volume Measurements; D005996:Nitroglycerin / Q000008:administration & dosage; D009929:Organ Size; D017156:Photoplethysmography; D013154:Spleen / Q000000981:diagnostic imaging / Q000187:drug effects / Q000294:innervation / Q000503:physiopathology*; D013157:Splenic Artery / Q000000981:diagnostic imaging / Q000503:physiopathology; D013997:Time Factors; D014463:Ultrasonography; D014655:Vascular Resistance; D014665:Vasodilator Agents / Q000008:administration & dosage
chemical_list: D014665:Vasodilator Agents; D005996:Nitroglycerin