title: Oxygen delivery-independent effect of blood flow on diaphragm fatigue.
abstract: To determine the effect of blood flow on diaphragm fatigue independent of oxygen delivery, the left hemidiaphragm was vascularly isolated in 14 pentobarbital-anesthetized, mechanically ventilated dogs. Fatigue (decline in tension generation) of the left diaphragm was induced by phrenic nerve stimulation at 10 Hz, 12/min, duty cycle of 0.5 for 8 min. Two stimulation periods separated by 30 min of rest were performed in each animal. Diaphragmatic O2 delivery during the two periods was the same. In Group 1 (n = 8), the diaphragm was autoperfused from the femoral artery (high O2-low flow) during the first stimulation period. The tension generated by the diaphragm during this period declined progressively to 47.7% of initial values. In the second period in this group, the diaphragm was pump perfused with arterial blood, diluted with an equal volume of 6% dextran at a flow rate twice that of the first period (low O2-high flow). Tension in this period declined to 76% of initial tension (p less than 0.05 compared with high O2-low flow). In Group 2 (n = 6), stimulation performed while perfusing the diaphragm in the first period with diluted arterial blood at a flow rate twice that recorded during autoperfusion (low O2-high flow) produced a decline in tension to 70% of the initial values. In the second period, the diaphragm was perfused with undiluted arterial blood at a flow rate equal to 50% of that of the first period (high O2-low flow). Tension during this period declined to 56% of initial values (p less than 0.05 compared with low O2-high flow).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Division of Pulmonary, Royal Victoria Hospital, Montreal, Quebec, Canada.
authors.forename: M E
authors.initials: ME
authors.lastname: Ward
authors.forename: S A
authors.initials: SA
authors.lastname: Magder
authors.forename: S N
authors.initials: SN
authors.lastname: Hussain
mesh_terms: D000818:Animals; D003964:Diaphragm / Q000098:blood supply* / Q000503:physiopathology; D004285:Dogs; D004558:Electric Stimulation; D009119:Muscle Contraction / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology; D010791:Phrenic Nerve / Q000502:physiology; D011652:Pulmonary Circulation / Q000502:physiology; D012121:Respiration, Artificial; D012131:Respiratory Insufficiency / Q000503:physiopathology*