The American review of respiratory disease
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Am. Rev. Respir. Dis. · Nov 1987
Pulmonary vascular tone improves pulmonary gas exchange in the adult respiratory distress syndrome.
Hemodynamics, blood gases, lung mechanics, and the distributions of ventilation-perfusion ratios (VA/Q) were studied before and after iv diltiazem, 0.5 mg/kg over 30 min, in 6 patients with pulmonary hypertension secondary to the adult respiratory distress syndrome (ARDS) ventilated with 7 to 20 cm H2O positive end-expiratory pressure (PEEP). Diltiazem decreased systemic and pulmonary arterial pressures without changes in cardiac output and in filling pressures of the heart, and with a slowing of heart rate. Pulmonary vascular resistances decreased from 401 +/- 59 to 329 +/- 58 dyne.s.cm-5.m2 (mean +/- SEM), p less than 0.01. ⋯ Lung compliance and airway resistances did not change. Diltiazem increased true shunt from 23 +/- 5 to 30 +/- 7% of total blood flow (p less than 0.02) without other modification in the pattern of VA/Q distribution as measured by the multiple inert gas elimination technique. These results suggest that pulmonary vascular tone contributes to the maintenance of VA/Q matching in patients with ARDS.
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Am. Rev. Respir. Dis. · Oct 1987
Comparative StudyAtrial natriuretic peptide concentrations and pulmonary hemodynamics in patients with pulmonary artery hypertension.
To define the relationship between plasma levels of immunoreactive atrial natriuretic peptide (IR-ANP) and hemodynamic parameters in patients with chronic pulmonary artery hypertension, we measured plasma concentrations of the peptide in 15 patients during right heart catheterization. Eleven patients had chronic obstructive pulmonary disease and 4 had pulmonary vascular disease of diverse etiology. At rest, plasma concentrations of IR-ANP positively correlated with mean pulmonary artery pressure (r = 0.70, p less than 0.01) and pulmonary vascular resistance (r = 0.88, p less than 0.001), but not with right atrial pressure. ⋯ Plasma concentrations of IR-ANP increased from 131 +/- 22 to 191 +/- 30 pg/ml (p less than 0.003) at maximal exercise, whereas pulmonary artery pressure increased from 29 +/- 1.5 to 56 +/- 2.5 mm Hg and right atrial pressure from 5 +/- 1 to 13 +/- 2 mm Hg. Increases of plasma IR-ANP concentrations correlated with changes in pulmonary artery pressure and right atrial pressure but not with changes in pulmonary capillary wedge pressure. These findings suggest that ANP is released in response to an increase in pulmonary artery pressure and are consistent with the hypothesis that ANP could modulate the pulmonary vascular tone in patients with pulmonary artery hypertension.
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Am. Rev. Respir. Dis. · Oct 1987
Comparative StudyThe effects of ventilatory pattern on hyperinflation, airway pressures, and circulation in mechanical ventilation of patients with severe air-flow obstruction.
Patients with severe air-flow obstruction receiving mechanical ventilation are at risk of inadvertent pulmonary hyperinflation with morbidity and mortality caused by pneumothorax and circulatory depression. Nine patients with severe air-flow obstruction (5 asthma, 4 chronic air-flow obstruction) requiring mechanical ventilation were studied while sedated and therapeutically paralyzed. Pulmonary hyperinflation during steady-state ventilation was quantified by measuring total exhaled volume during 20- to 40-s apnea (end-inspiratory lung volume, VEI). ⋯ Peak airway pressure (Ppk) was predominantly related to inspiratory flow and did not reflect changes in lung volume. Levels of ventilation required for normocapnia prior to paralysis (15.7 +/- 2.3 L/min) were associated with hypotension in 7 patients and probable hyperinflation in excess of 1.96 +/- 0.17 L above FRC. VEI is a simple, reproducible measurement of pulmonary hyperinflation and may be more important than Ppk in the causation of barotrauma.(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. Rev. Respir. Dis. · Oct 1987
Comparative StudyMild emphysema is associated with reduced elastic recoil and increased lung size but not with air-flow limitation.
Thirty-nine excised human lungs were examined to identify early changes in the small airways, their size distribution, and their elastic recoil in relation to mild degrees of emphysema. Elastic recoil measurement, single-breath nitrogen (SBN2) tests, and FEV1 were obtained from 18 lungs with no emphysema and 21 emphysematous lungs with no greater than Grade 5 emphysema score. The mean number of alveolar attachments per brochiole was determined from all the bronchioles cut in cross section. ⋯ When data from both groups were combined, elastic recoil was shown to be related to both the number of alveolar attachments (p less than 0.03) and the mean diameter of the small airways (p less than 0.01). We conclude that structural and functional changes in lungs with mild emphysema include reduced elastic recoil, increased lung size, and some size distribution changes in the small airways. Mild emphysema is not associated with air-flow limitation.