Respiratory physiology & neurobiology
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Respir Physiol Neurobiol · Mar 2012
Rapid intravenous infusion of 20 mL/kg saline alters the distribution of perfusion in healthy supine humans.
Rapid intravenous saline infusion, a model meant to replicate the initial changes leading to pulmonary interstitial edema, increases pulmonary arterial pressure in humans. We hypothesized that this would alter lung perfusion distribution. Six healthy subjects (29 ± 6 years) underwent magnetic resonance imaging to quantify perfusion using arterial spin labeling. ⋯ There were no significant changes in lung density. These data suggest that saline infusion increased perfusion to nondependent lung, consistent with an increase in intravascular pressures. Dependent lung may have been "protected" from increases in perfusion following infusion due to gravitational compression of the pulmonary vasculature.
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Respir Physiol Neurobiol · Mar 2012
Alveolar LCI vs. standard LCI in detecting early CF lung disease.
Multiple breath washout (MBW) is a sensitive technique that detects early airways disease. However in very young children, large equipment and physiological dead space relative to lung volumes may result in a higher Lung Clearance Index (LCI). We investigated whether alveolar LCI (aLCI) is a more sensitive index than standard LCI in children. ⋯ However, the difference in sensitivity (aLCI vs. LCI) was not significant (p=0.36). We conclude that LCI is minimally affected by airway deadspace, or relative equipment deadspace, and is an appropriate measure of lung function in infancy.
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Respir Physiol Neurobiol · Mar 2012
Effects of intra-abdominal pressure on respiratory system mechanics in mechanically ventilated rats.
We investigated the effects of intra-abdominal pressure on respiratory system compliance at different PEEP levels. 20 ventilated rats underwent four pressure levels (7, 9, 11, 13 mm Hg) of helium pneumoperitoneum and were allocated to one of the four PEEP groups (0, 3, 6 and 9 cm H(2)O). From the expiratory pressure-volume curve the mathematical inflection point (MIP) was calculated. Volume-dependent compliance was analyzed using the SLICE-method. ⋯ The level of intra-abdominal pressure alters respiratory system mechanics in healthy lungs. Intratidal compliance can be used to guide the PEEP adjustment in intra-abdominal hypertension. If counterbalanced by PEEP, elevated intra-abdominal pressure has no negative effects on oxygenation or hemodynamics.
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Respir Physiol Neurobiol · Jan 2012
Naloxone pro-drug rescues morphine induced respiratory depression in Sprague-Dawley rats.
Respiratory depression is the main obstacle for the safe administration of morphine for acute pain after injury. Due to this complication, new delivery methods are needed to insure that safe and effective doses of opioid analgesics are administered during emergencies. A depot formulation containing a naloxone pro-drug was designed to release the antidote when morphine causes dangerous hypoxic conditions in the blood. ⋯ Non-invasive two-chamber plethysmography was used to monitor and record respiration and to test the capability of the naloxone pro-drug to respond to and rescue morphine-induced respiratory depression in the animal. We show that the pro-drug formulation can both prevent and reverse severe morphine induced respiratory depression. The animal model demonstrates that co-administration of the naloxone pro-drug reliably antagonizes profound respiratory depressive effects of morphine.
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We examined the influences of acute lung injury and hypoxia on neurological outcome. Functional performance was assessed using a neurocognitive test and a neurologic deficit score (NDS) five days before. On experimental day, mechanically ventilated pigs were randomized to hypoxia only (HO group, n=5) or to acute lung injury (ALI group, n=5). ⋯ Oxygenation was comparable between groups although significantly higher inspiratory pressures occured after ALI. Cytokines showed a trend towards higher levels after ALI. Neurocognitive compromise after ALI seems due to a more pronounced inflammatory response and complex mechanical ventilation.