The American review of respiratory disease
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Am. Rev. Respir. Dis. · Oct 1992
Lung mechanics and gas exchange during pressure-control ventilation in dogs. Augmentation of CO2 elimination by an intratracheal catheter.
Increased awareness of pressure-related injury to the alveolar-capillary interface has renewed interest in modes of ventilation that limit alveolar distention such as pressure-controlled ventilation (PCV). We examined respiratory system mechanics and gas exchange during PCV in six dogs. Our data conformed to the predictions of our single-compartment mathematical model of respiratory dynamics during PCV (J Appl Physiol 1989; 67:1081-92). ⋯ We conclude that during PCV at a fixed Pset and Tl/Ttot increasing frequency caused VT to fall and VE to reach a plateau. Declining VT was associated with a rise in PaCO2 because of a subsequent fall in alveolar ventilation. Insufflating fresh gas by an intratracheal catheter increased alveolar ventilation and improved CO2 elimination by washing out the anatomic dead space.(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. Rev. Respir. Dis. · Sep 1992
Effect of positive end-expiratory pressure on right ventricular function in humans.
The effect of positive end-expiratory pressure (PEEP) on right ventricular (RV) function in humans is complex. Previous studies have been limited in their interpretation by not defining either pericardial pressure (Ppc) or RV volumes. Accordingly, we measured RV volumes and pressures and Ppc as PEEP was increased from zero to 15 cm H2O in 12 patients after thoracotomy, using a pulmonary arterial catheter equipped with a rapid responding thermistor that allowed measurement of RV ejection fraction (ef), while Ppc was measured via a pericardial balloon catheter. ⋯ Similarly, there was no relation between Ppa and ESV when either mean or peak Ppa values relative to Ppc were used. The relations between EDV and both SV and RVef were weak (r = 0.54 and 0.55, respectively). RVef varied inversely with ESV (r = -0.77), although it showed no relation to transmural peak Ppa (r = 0.28).(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. Rev. Respir. Dis. · Sep 1992
Case ReportsImproved diaphragmatic function after surgical plication for unilateral diaphragmatic paralysis.
We studied pulmonary function tests, maximal voluntary ventilation, arterial blood gases, and respiratory muscle strength and recruitment pattern in a 37-yr-old symptomatic man before and after surgical plication for a left unilateral diaphragmatic paralysis. After plication, FVC, FEV1, TLC and FRC increased, whereas residual volume remained unchanged. Arterial PO2 improved from 70 to 87 mm Hg. ⋯ This indicates more effective diaphragmatic recruitment after the procedure. We conclude that surgical plication may be of benefit to patients with symptomatic unilateral diaphragmatic paralysis. The improvement is due to improved respiratory muscle function.
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Am. Rev. Respir. Dis. · Sep 1992
Comparative StudyRisk factors for morbidity in mechanically ventilated patients with acute severe asthma.
Acute severe asthma is associated with significant morbidity and mortality. We retrospectively quantified hypotension, pulmonary barotrauma, and cardiac arrhythmias in all patients with severe asthma admitted to the intensive care unit (ICU) and prospectively evaluated the predictive value of a measurement of dynamic hyperinflation (DHI) in those patients who required mechanical ventilation. In the first study, 88 ICU admissions for severe asthma over 5 yr (73 patients, 40 +/- 18 yr, 36 men, 37 women) were evaluated. ⋯ There were no ICU deaths, but high incidences of pulmonary barotrauma (27%) and hypotension (41%) were found. Both minute ventilation (VE and VEI) were significantly higher in patients who developed complications (VE 13.7 +/- 3.0 versus 11.2 +/- 2.5 L/min, VEI 26.1 +/- 4.7 versus 20.0 +/- 7.4 ml/kg, p less than 0.05) but only VEI had a threshold value significantly predictive of complications. For VEI less than 1.4 L, 0/5 (0%) patients had complications; for VEI greater than or equal to 1.4 L, 11/17 (65%) had complications (p = 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. Rev. Respir. Dis. · Sep 1992
Comparative StudyAdaptations of the peripheral circulation to PEEP.
The purpose of this study was to determine the role of changes in the parameters of venous return on the homeostatic adaption to the application of PEEP. We studied 13 dogs anesthetized with alpha-chloralose, intubated, and ventilated. We measured central venous pressure (CVP), arterial pressure (Pao) and cardiac output by thermal dilution. ⋯ The rise in MCFP matched the rise in CVP so that the pressure gradient for venous return did not change. However, there was also an increase in the resistance to venous return, which resulted in a lower cardiac output than expected for the rise in MCFP. In conclusion, homeostatic adjustments to PEEP included a decrease in vascular capacitance, which is partially offset by a rise in the resistance to venous return.