American journal of respiratory and critical care medicine
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Am. J. Respir. Crit. Care Med. · Nov 1995
Comparative StudyPharmacologic characterization of endothelin receptor responses in the isolated perfused rat lung.
Endothelin receptor subtypes were characterized in isolated perfused rat lungs using the peptide ETA-receptor antagonists BQ 610 and BQ 123, the nonpeptide mixed ETA-/ETB-receptor antagonist bosentan, and the ETB-receptor agonist IRL 1620. Intra-arterial injection of 1 nmol IRL 1620 caused an enhanced reduction in pulmonary conductance compared with 1 nmol endothelin (ET-1) or 0.33 nmol IRL 1620. Pretreatment of lungs with BQ 610, BQ 123, or bosentan aggravated the bronchoconstriction induced by 1 nmol ET-1 so that it was comparable to that induced by 1 nmol IRL 1620. ⋯ ET-1, but not IRL 1620, provoked the release of thromboxane B2. The main effect of ETA-receptor stimulation is vasoconstriction, whereas ETB-receptor stimulation causes bronchoconstriction. Both actions, however, are attenuated by the other receptor, i.e., the ETA-induced vasoconstriction is attenuated by ETB-receptor-induced release of vasodilators such as prostacyclin, whereas the ETB-receptor-induced bronchoconstriction is attenuated by an unknown ETA-receptor-dependent bronchodilatory mechanism.
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Am. J. Respir. Crit. Care Med. · Oct 1995
Randomized Controlled Trial Comparative Study Clinical TrialSupplemental oxygen during sleep in children with sleep-disordered breathing.
Supplemental O2 is sometimes used to treat children with the obstructive sleep apnea syndrome (OSAS). However, its effects have not been studied. We therefore evaluated the use of supplemental O2 during sleep in children with OSAS. ⋯ We conclude that breathing supplemental O2 during sleep in children with OSAS results in improved oxygenation and in most cases does not exacerbate sleep-disordered breathing. However, end-tidal PCO2 should be monitored in children with OSAS receiving O2 therapy. We speculate that supplemental O2 does not depress the ventilatory drive during sleep in most children with OSAS.
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Am. J. Respir. Crit. Care Med. · Oct 1995
Comparative StudyClinical risk factors for pulmonary barotrauma: a multivariate analysis.
Previous investigations have suggested that elevated airway pressures increase the risk of ventilator-induced pneumothorax. However, risk factor analysis using multivariate techniques has not been done. We investigated the hypothesis that airway pressures would not independently correlate with pneumothorax when underlying disease was considered. ⋯ A similar analysis performed on the ARDS population revealed independent correlation only with male sex. Trends toward elevation in airway pressures were seen that did not reach statistical significance. We conclude that development of pneumothorax is most closely correlated with underlying disease, specifically ARDS, and that the associations previously noted between airway pressures and barotrauma largely relate to the occurrence of high airway pressures in ARDS.
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Am. J. Respir. Crit. Care Med. · Oct 1995
The load of inspiratory muscles in patients needing mechanical ventilation.
We studied 31 consecutive mechanically ventilated patients with acute respiratory failure in two stages: (1) During spontaneous breathing through the respirator, switching from full mechanical assistance to continuous positive airway pressure mode with 0 cm H2O pressure. We measured maximum inspiratory pressure and continuously monitored the pattern of breathing. After 8 to 25 min, none of the patients were able to sustain spontaneous breathing and mechanical ventilation was required to resume. (2) Subsequently, during mechanical ventilation, by manipulating the variables of the ventilator we simulated the pattern of spontaneous breathing the patients had just before the re-institution of mechanical ventilation. ⋯ When we plotted the Pi/Pimax and Ppeak/Pimax against the dynamic increase in FRC, we found that the Pi/Pimax of 13 patients (42%) and the Ppeak/Pimax of 25 of 31 patients (81%) were placed above a hypothetical critical line, representing the critical inspiratory pressures above which fatigue may occur. In addition, almost all patients were gathered around the critical line. We conclude that during discontinuation from mechanical ventilation (MV) almost all patients breathe against a high inspiratory load and their inspiratory muscles perform work that may lead to fatigue.
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Am. J. Respir. Crit. Care Med. · Oct 1995
Effects of PEEP on acinar gas transfer in healthy and lung-injured dogs.
We measured cardiorespiratory variables and 133xenon washout from a nonperfused lung region (XeW) in six anesthetized/paralyzed dogs, mechanically ventilated with 60% O2 at different positive end-expiratory pressures (PEEP). XeW in this technique represents directly measured acinar gas transfer (3). Measurements were repeated after induction of lung injury by lavaging the lungs 11 to 13 times with 600 ml saline. ⋯ At 20 cm H2O PEEP, Valv and CL were not different from control values (p > 0.05), and XeW was higher than control values (p < 0.05). At estimated alveolar volumes above 400 ml, values for XeW before and after lavage were similar. We conclude that, during severe lung injury: (1) increasing PEEP to moderate levels will increase acinar gas transfer but, after a certain lung volume is reached, further increases in PEEP will have effects similar to the healthy condition; (2) overall mechanical properties of the lung do not reflect the responses to PEEP of the lung periphery.