Search PubMed⌕ Search

Biomedical subjects

S F Quan

Publications and source records attributed to S F Quan.

89 records · Page 5Linked to original sources
PubMed1983

Hemodynamic effects of high-frequency jet ventilation.

The hemodynamic effects of high-frequency jet ventilation (HFJV) and conventional ventilation were compared in normovolemic and functionally hypovolemic dogs. In normovolemic animals, no differences in hemodynamic function were found among spontaneous ventilation, conventional ventilation, and HFJV. When venous return was impaired by 15 cm H2O PEEP, cardiac index and stroke index were 25% higher with HFJV than with conventional ventilation (P less than 0.05). In another study with PEEP, conventional ventilation was compared to spontaneous ventilation, HFJV synchronized to five different parts of the cardiac cycle, and asynchronous HFJV. Heart rate was 15% lower and mean arterial pressure was 26% lower with conventional ventilation than with HFJV modes (P less than 0.05). There were no differences between synchronous and asynchronous HFJV. These results indicate that hemodynamic dysfunction may be less likely with HFJV than conventional ventilation. No advantage of synchronizing jet pulsations to a specific part of the cardiac cycle could be demonstrated.

Airway Resistance↗
PubMed1983

Mixed venous oxygen.

In critically ill patients, measurement of mixed venous oxygenation is useful as an indicator of the adequacy of tissue oxygenation and as an indirect reflection of cardiac output. The flexible fiberoptic pulmonary artery catheter oximeter permits continuous in vivo measurements of the mixed venous oxygen saturation. However, in some groups of critically ill patients, such as those with adult respiratory distress syndrome or sepsis, measurements of mixed venous oxygen may be misleading and should be interpreted with caution.

Cardiac Output↗
PubMed1983

Rapid diagnosis of pulmonary coccidioidomycosis. Cytologic v potassium hydroxide preparations.

In 26 patients with culture-proved pulmonary coccidioidomycosis, cytologic preparations of respiratory secretions were significantly more sensitive (38.5%) than potassium hydroxide (KOH) preparations (15.4%) in identifying spherules of Coccidioides immitis. Those patients able to produce sputum or having multiple-lobe pneumonitis on chest roentgenogram appeared to be more likely to have spherules identified in the sputum by either technique. In the absence of sputum production or multiple-lobe pneumonitis, neither cytologic nor KOH preparations were likely to disclose spherules. Because of its greater sensitivity, a cytologic preparation should be examined in addition to a KOH preparation when pulmonary coccidioidomycosis is a clinical consideration.

Adolescent↗
PubMed1982

Effects of arachidonic acid, PGF2 alpha, and a PGH2 analogue on airway diameters in dogs.

The effects of intravenous arachidonic acid, a prostaglandin H2 analogue [(15S)-hydroxyl-11 alpha, 9 alpha-(epoxymethano)prosta-5Z,13E-dienoic acid (PGH2-A)], and prostaglandin F2 alpha (PGF2 alpha) on lung mechanics and airway diameters were compared using tantalum bronchography in 20 paralyzed, artificially ventilated, pentobarbital-anesthetized dogs. These agents produced dose-related increases in lung resistance (RL) and decreases in dynamic compliance (Cdyn). Both RL and Cdyn changed maximally within 25 s after injection. RL, however, returned to base line within 2 min, whereas the decrease in Cdyn persisted much longer. Changes in the diameter of airways less than 2 mm produced small changes in RL and Cdyn. Larger changes in RL corresponded with changes in airways as large as 4 mm. Vagal reflexes or pulmonary edema were not important contributors to these effects. These data suggest that the changes in RL and Cdyn produced by intravascular injections of arachidonic acid, PGH2-A, and PGF2 alpha result from their direct effects on smooth muscle in airways as large as 4 mm.

Airway Resistance↗
PubMed1981

Extubation from ambient or expiratory positive airway pressure in adults.

End-expiratory pressure is often used to improve arterial oxygenation and prevent atelectasis in intubated spontaneously breathing patients. To compare the effect of extubation from low levels of expiratory positive airway pressure (EPAP) of extubation from ambient airway pressure, functional residual capacity (FRC) and arterial blood oxygen tension (Pao2) were measured in 12 spontaneously breathing patients during three conditions in the peri-extubation period: 1) intubated at 5 cm H2O EPAP (EPAP 5); 2) intubated at ambient airway pressure (EPAP 0); and 3) within one hour after extubation. During EPAP 5, mean +/- SE values for FRC (1864 +/- 230 ml) and Pao2 (114 +/- 8 torr) were the same as those obtained after extubation (FRC = 1794 +/- 159 ml, Pao2 = 117 +/- 5 torr). However, both FRC (1600 +/- 186 ml) and Pao2 (106 +/- 8 torr) were lower during EPAP 0 than after extubation or EPAP 5 (P less than 0.01-0.05). The magnitude of increase in FRC and Pao2 on extubation from EPAP 0 varied inversely with the patient's lung thorax compliance (r = -0.84, P less than 0.005). It was concluded that a period of EPAP 0 is not necessary in the weaning period, and that it may be deleterious in patients with compromised lung thorax mechanics.

Adolescent↗
PubMed1981

Lung volumes, mechanics, and oxygenation during spontaneous positive-pressure ventilation: the advantage of CPAP over EPAP.

To determine if continuous positive airway pressure (CPAP) or expiratory positive airway pressure (EPAP) is superior for achieving or maintaining effective lung volume in spontaneously breathing critically ill patients in acute respiratory failure, the authors measured functional residual capacity (FRC), airway and esophageal pressures, and arterial oxygen tensions when CPAP and EPAP were 5 and 10 cm H2O. Arterial oxygenation, FRC, and transpulmonary pressure at end-expiration were greatest when CPAP was 10 cm H2O. Lung compliance did not change. The authors conclude that CPAP at 10 cm H2O is the more effective technique, either because it allows relaxation of chest wall musculature on expiration, or because EPAP at 10 cm H2O increases chest wall muscle tone.

Acute Disease↗
PubMed1980

Changes in venous admixture with alterations of inspired oxygen concentration.

To assess the change in venous admixture during breathing of 100 per cent oxygen (FIO2 1.0), shunt fraction (Qs/Qt) was calculated at a maintenance FIO2 (FIO2m:0.27--0.70) and at FIO2 1.0 in 40 studies of 34 patients with acute respiratory failure. At FIO2 1.0 Qs/Qt increased in 26 studies, but did not increase in 14 studies. Patients in whom Qs/Qt increased during breathing of oxygen and mild respiratory failure, as indicated by low Qs/Qt values at FI02m and a low incidence of diffuse parenchymal infiltrates on chest roentgenograms. All patients who had recently had cardiovascular surgical procedures were in this group. Respiratory failure was more severe in those in whom Qs/Qt decreased with oxygen, as indicated by high Qs/Qt values at FIO2m, evidence of diffuse pulmonary disease by roentgenography, and signs of adult respiratory distress syndrome. The authors conclude that changes in Qs/Qt in response to FIO2 1.0 in acute respiratory failure are related to the severity of respiratory insufficiency.

Acute Disease↗
PubMedDate not supplied

Suppression of atrial ectopy with intravenous metoprolol in chronic obstructive pulmonary disease patients.

To determine the efficacy of a cardioselective beta blocker in the treatment of atrial ectopy in patients with chronic obstructive pulmonary disease (COPD), we administered intravenous metoprolol (0.2 mg/kg) to six patients with atrial ectopic depolarizations (AEDs) and chronic partially reversible airflow limitation (FEV1 = 1.24 +/- 0.21 liter, mean +/- S.E.). Metoprolol reduced the mean frequency of AEDs from 713 +/- 237 per hour to 218 +/- 127 per hour. Furthermore, three of six patients experienced an 85 per cent or greater decrease in AEDs. No changes were observed in FEV1, FVC, or FEF25-75 over the course of the study. These data suggest that intravenous metoprolol is effective in reducing the frequency of AEDs and that it can be administered to patients with COPD without causing an increase in airflow limitation.

Aged↗
PubMedDate not supplied

Piriprost pretreatment attenuates the smoke-induced increase in 99mTcDTPA lung clearance.

We studied the effects of acute smoke exposure on lung permeability, eicosanoids, and inflammatory cell activity. Thirty-five New Zealand white rabbits were anesthetized, paralyzed, and exposed to 60 tidal volume breaths of diesel fuel-polycarbonate plastic smoke or sham smoke within 10 min. At 1 h postexposure the rabbits were killed and their lungs were removed for bronchoalveolar lavage (BAL) or pathologic procedures. Smoke exposure caused decreases in technetium-labeled diethylenetriamine pentaacetate (99mTcDTPA, mol. wt. 492 Da) biological half-life (t1/2), BAL plasminogen activator, and BAL leukotriene B4 (LTB4). In addition, alveolar macrophage acid phosphatase enzyme activity increased in smoke-exposed rabbits. The leukotriene synthesis inhibitor, piriprost (U-60,257), given before smoke exposure, caused attenuation of the changes in 99mTcDTPA uptake and plasminogen activator, swelling of type I alveolar cell epithelium, a large increase in lung inflammatory cells, and decreases in BAL LTB4, prostaglandin E2 (PGE2), and TxB2 (stable metabolite of thromboxane, TxA2). We conclude that changes in alveolar-capillary barrier permeability and plasminogen activator activity occur within 1 h after exposure to smoke and may play an early role in the inflammatory process associated with smoke inhalation injury. Furthermore, piriprost attenuates the smoke-induced increase in alveolar-capillary barrier permeability and decrease in plasminogen activator activity and causes a swelling of type I alveolar epithelium. However, our data suggest that neither lung eicosanoids or the alveolar macrophage lysis process plays a major role in the smoke-induced increase in alveolar-capillary barrier permeability.

Animals↗