title: Increased propensity for apnea in response to acute elevations in left atrial pressure during sleep in the dog.
abstract: Periodic breathing is commonly observed in chronic heart failure (CHF) when pulmonary capillary wedge pressure is abnormally high and there is usually concomitant tachypneic hyperventilation. We hypothesized that acute pulmonary hypertension at pressures encountered in CHF and involving all of the lungs and pulmonary vessels would predispose to apnea/unstable breathing during sleep. We tested this in a chronically instrumented, unanesthetized dog model during non-rapid eye movement (NREM) sleep. Pulmonary hypertension was created by partial occlusion of the left atrium by means of an implanted balloon catheter in the atrial lumen. Raising mean left atrial pressure by 5.7 +/- 1.1 Torr resulted immediately in tachypneic hyperventilation [breathing frequency increased significantly from 13.8 to 19.9 breaths/min; end-tidal P(CO2) (P(ET(CO2))) fell significantly from 38.5 to 35.9 Torr]. This tachypneic hyperventilation was present during wakefulness, NREM sleep, and rapid eye movement sleep. In NREM sleep, this increase in left atrial pressure increased the gain of the ventilatory response to CO2 below eupnea (1.3 to 2.2 l.min(-1).Torr(-1)) and thereby narrowed the CO2 reserve [P(ET(CO2)) (apneic threshold) - P(ET(CO2)) (eupnea)], despite the decreased plant gain resulting from the hyperventilation. We conclude that acute pulmonary hypertension during sleep results in a narrowed CO2 reserve and thus predisposes toward apnea/unstable breathing and may, therefore, contribute to the breathing instability observed in CHF.
authors.affiliation: Laboratoire de Physiologie, Faculté de Médecine de Nancy, Université Henri Poincaré, Nancy, France.
authors.forename: Bruno J
authors.initials: BJ
authors.lastname: Chenuel
authors.forename: Curtis A
authors.initials: CA
authors.lastname: Smith
authors.forename: James B
authors.initials: JB
authors.lastname: Skatrud
authors.forename: Kathleen S
authors.initials: KS
authors.lastname: Henderson
authors.forename: Jerome A
authors.initials: JA
authors.lastname: Dempsey
mesh_terms: D000818:Animals; D001049:Apnea / Q000209:etiology* / Q000503:physiopathology*; D016279:Atrial Function, Left / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology; D002245:Carbon Dioxide / Q000032:analysis; D002302:Cardiac Output / Q000502:physiology; D002628:Chemoreceptor Cells / Q000502:physiology; D004285:Dogs; D005105:Expiratory Reserve Volume / Q000502:physiology; D005260:Female; D006333:Heart Failure / Q000150:complications*; D006339:Heart Rate / Q000502:physiology; D006976:Hypertension, Pulmonary / Q000150:complications / Q000503:physiopathology*; D006985:Hyperventilation / Q000209:etiology / Q000503:physiopathology; D012123:Pulmonary Ventilation / Q000502:physiology; D015656:Respiratory Mechanics / Q000502:physiology; D012890:Sleep / Q000502:physiology*; D012893:Sleep Wake Disorders / Q000209:etiology / Q000503:physiopathology; D014851:Wakefulness / Q000502:physiology
chemical_list: D002245:Carbon Dioxide