Respiratory physiology & neurobiology
-
The use of mechanical ventilation has become widespread in the management of hypoxic respiratory failure. Investigations of pulmonary mechanics in this clinical scenario have demonstrated that there are significant differences in compliance, resistance and gas flow when compared with normal subjects. This paper will review the mechanisms by which pulmonary mechanics are assessed in mechanically ventilated patients and will review how the data can be used for investigative research purposes as well as to inform rational ventilator management.
-
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.
-
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.
-
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.