Effect of heliox on heart rate kinetics and dynamic hyperinflation during high-intensity exercise in COPD.
Respiratory mechanical abnormalities in patients with chronic obstructive pulmonary disease (COPD) may impair cardiodynamic responses and slow down heart rate (HR) kinetics compared with normal resulting in reduced convective oxygen delivery during exercise. We reasoned that heliox breathing (79% helium-21% oxygen) and the attendant reduction of operating lung volumes should accelerate HR kinetics in the transition from rest to high-intensity exercise. Eleven male ambulatory patients with clinically stable COPD undertook constant work-rate cycle testing at 80% of each individuals' maximum work capacity while breathing room air (RA) or heliox (HX), randomly. Mean response time (MRT) for HR and dynamic end-expiratory lung volume (EELV) were measured. Resting EELV was not affected by HX breathing, while exercise EELV decreased significantly by 0.23 L at isotime during HX breathing compared with RA. During HX breathing, MRT for HR significantly accelerated (p = 0.002) by an average of 20 s (i.e., 17%). Speeded MRT for HR correlated with indices of reduced lung hyperinflation, such as EELV at isotime (r = 0.88, p = 0.03), and with improved exercise endurance time (r = -0.64, p = 0.03). The results confirm that HX-induced reduction of dynamic lung hyperinflation is associated with consistent improvement in indices of cardio-circulatory function such as HR kinetics in the rest-to-exercise transition in COPD patients.
Laveneziana
Pierantonio
P
Laboratoire de Physio-Pathologie Respiratoire, Equipe de Recherche ER 10, Faculté de Médecine Pierre et Marie Curie (site Pitié-Salpêtrière), Université Paris VI, Paris, France. pier_lav@yahoo.it
Valli
Gabriele
G
Onorati
Paolo
P
Paoletti
Patrizia
P
Ferrazza
Alessandro Maria
AM
Palange
Paolo
P
D000368:Aged; D004311:Double-Blind Method; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D017079:Exercise Tolerance / Q000187:drug effects / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects*; D006371:Helium / Q000494:pharmacology*; D006439:Hemodynamics / Q000187:drug effects*; D006801:Humans; D001239:Inhalation / Q000187:drug effects*; D007320:Inspiratory Capacity / Q000187:drug effects; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000494:pharmacology*; D005082:Physical Exertion / Q000187:drug effects / Q000502:physiology; D010919:Placebos; D029424:Pulmonary Disease, Chronic Obstructive / Q000473:pathology / Q000503:physiopathology*
D010919:Placebos; D006371:Helium; C038949:heliox; D010100:Oxygen