Decreasing size of cardiogenic oscillations reflects decreasing compliance of the respiratory system during long-term ventilation.
Part of the energy produced by the heartbeat is transferred to the lung and promotes intrapulmonary gas mixing. It is likely that this transmission in the form of local mechanical disturbances affects and reflects respiratory mechanics. The effects of the cardiogenic oscillations were studied in seven piglets during 7 h of monotonous mechanical ventilation. During the 1st h of ventilation, every heartbeat triggered a noticeable transient increase in lung volume of 14 ml (95% confidence interval = 10-17 ml). After 7 h, the increase in lung volume due to heartbeat significantly decreased to 7 ml (95% confidence interval = 2-9 ml, P < 0.05). During the course of ventilation, overall lung compliance and gas exchange were progressively compromised. We conclude that 1) sufficient mechanical energy is transferred from the beating heart to the lung to increase lung volume, and 2) the ability of the heartbeats to help increase lung volume is reduced during long-term ventilation, which reflects the changes in lung compliance.
Lichtwarck-Aschoff
Michael
M
Department of Surgical, Uppsala University, Sweden. m.lichtwarck-aschoff@t-online.de
Suki
Bela
B
Hedlund
Anders
A
Sjöstrand
Ulf H
UH
Markström
Agneta
A
Kawati
Rafael
R
Hedenstierna
Göran
G
Guttmann
Josef
J
D000818:Animals; D000831:Animals, Newborn; D001683:Biological Clocks / Q000502:physiology*; D008170:Lung Compliance / Q000502:physiology*; D008176:Lung Volume Measurements / Q000379:methods; D009200:Myocardial Contraction / Q000502:physiology*; D012123:Pulmonary Ventilation / Q000502:physiology*; D012121:Respiration, Artificial / Q000379:methods*; D013552:Swine; D013997:Time Factors