Blood flow to respiratory muscles and major organs during inspiratory flow resistive loads

Abstract

To determine whether diaphragmatic fatigue in the intact animal subjected to loaded breathing is associated with a decrease in diaphragmatic blood flow, seven unanesthetized sheep were subjected to severe inspiratory flow resistive (IFR) loads that led to a decrease in transdiaphragmatic pressure (Pdi) and a rise in arterial PCO2 (PaCO2). Blood flow to the diaphragm, other respiratory muscles, limb muscles, and major organs was measured using the radionuclide-labeled microsphere method. With these loads blood flow increased to the diaphragm (621 +/- 242%) and all the other inspiratory and expiratory diaphragm (621 +/- 242%) and all the other inspiratory and expiratory muscles; there was no statistically significant change in blood flow to these muscles at the time when Pdi decreased and PaCO2 rose. Blood flow also increased to the heart (103 +/- 34%), brain (212 +/- 39%), and adrenals (76 +/- 9%), whereas pancreatic flow decreased (-66 +/- 14%). Limb muscle blood flow remained unchanged. We conclude that in unanesthetized sheep subjected to IFR loads 1) we did not demonstrate a decrease in respiratory muscle blood flow associated with diaphragmatic fatigue and ventilatory failure, and 2) there is a redistribution of blood flow among major organs.

Peripheral perfusion index as a predictor of failed weaning from mechanical ventilation

“…Switching the patient from assisted to spontaneous ventilation is usually associated with increased oxygen demands [5], which might not be matched with a proportional increase in the oxygen delivery. During the SBT, blood flow is diverted towards respiratory muscles; this impairs the oxygen delivery to other tissues [6,7]. Subsequently, various indices for peripheral tissue perfusion were reported to be impaired in patients with failed extubation trials such as serum lactate [8], central venous oxygen saturation [9], thenar oxygen saturation, [15], mottling score, and knee oxygen saturation [16].…”

“…Spontaneous breathing trial is usually associated with increased oxygen demands [5] which is sometimes not matched with equivalent increase in oxygen delivery [5]. Diversion of blood flow towards respiratory muscles during the SBT impairs oxygen delivery to other tissues [6,7]. Impairment of various indices for peripheral tissue perfusion was found to be associated with higher risk of failed extubation [8,9].…”

Respiratory muscle injury, fatigue and serum skeletal troponin I in rat

“…cultured cells (Van Nieuwenhoven et al 1996) and perfused Langendorff rat hearts (Vorderwinkler et al 1996), cTnI levels increase within 5 min, a result supported by measurements of cTnI levels after reperfusion of human myocardium following cardioplegic arrest (Bleier et al 1998). During IRL, perfusion of the diaphragm and other respiratory muscles increases (Mayock et al 1992; Pang et al 1993; Janssens et al 1995; Rochester & Bettini, 1976; Robertson et al 1977); if anything, therefore, washout of skeletal cytosolic proteins should be enhanced.…”

Regulation of ventilatory muscle blood flow

“…Peak parasternal intercostal and diaphragmatic blood flows reached <340 and 280 ml • 100 g 21 • min 21 , respectively, in response to severe inspiratory resistive loading. Figure 1 illustrates the main findings of Pang et al (93). Notice the substantial rise in parasternal and diaphragmatic blood flow during resistive loading.…”

“…Augmentation of ventilatory muscle metabolic demands during loaded breathing has also been shown to elicit a moderate rise in blood flow to the diaphragm and other inspiratory muscles (74,99,101). The highest rise in ventilatory muscle blood flow during resistive loading was reported in conscious sheep (93). Peak parasternal intercostal and diaphragmatic blood flows reached <340 and 280 ml • 100 g 21 • min 21 , respectively, in response to severe inspiratory resistive loading.…”