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Biomedical subjects

J B Downs

Publications and source records attributed to J B Downs.

At least 55 records · Page 3Linked to original sources
PubMed1987

Titration of continuous positive airway pressure by real-time dual oximetry.

The clinical utility of combined pulse and pulmonary artery oximetry (dual oximetry) in titrating continuous positive airway pressure (CPAP) therapy was tested in 17 patients with acute respiratory failure. The level of CPAP was altered in 2.5 cmH2O increments and decrements, while conventional measurements of cardiopulmonary function and continuous dual oximetry were performed. Then, optimum CPAP levels were selected using both techniques independently. The difference in optimum CPAP determined by the two methods was 0 cmH2O in ten of 17 patients, less than or equal to 2.5 cmH2O in 14 of 17 patients, and 5.0 to 7.5 cmH2O in the remaining three patients. When a difference existed, CPAP level determined with dual oximetry was consistently lower than the level selected by conventional means. The results indicate that the estimates of venous admixture and oxygen utilization coefficient obtained using dual oximetry provide sufficient information for rapid and accurate titration of CPAP in the majority of patients with acute respiratory failure.

Acute Disease↗
PubMed1986

Effect of pleurotomy on pulmonary function after median sternotomy.

To determine whether pleurotomy during median sternotomy worsens postoperative pulmonary function, patients whose pleurae remained intact (N = 7) were compared with those whose pleural spaces were entered during median sternotomy (N = 31). Thirty-eight adults performed spirometry and N2 washout to determine functional residual capacity preoperatively and 2, 24, 48, and 72 hours after extubation. Two mediastinal drainage tubes were placed in every patient; no pleural drainage tubes were inserted. Chest roentgenograms were performed preoperatively and 24 and 72 hours after extubation. Preoperatively, functional residual capacity, forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and FEV1/FVC did not differ between groups. Postoperatively, in all patients developed a restrictive pulmonary defect, but mean functional residual capacity, FVC, FEV1 and FEV1/FVC did not differ between groups. In contrast to earlier reports, entering the pleural space did not worsen the restrictive pulmonary defect that results from median sternotomy when direct pleural drainage was avoided.

Adult↗
PubMed1985

Prevention of postoperative pulmonary complications with CPAP, incentive spirometry, and conservative therapy.

Continuous positive airway pressure (CPAP) administered at intervals with a mask and incentive spirometry (IS) were compared with a regimen of coughing and deep breathing (CDB) to determine which promoted the most rapid recovery of pulmonary function after upper abdominal operations in 65 adults. Postoperatively, FRC of patients in all groups was similar relative to preoperative values. However, mean FRC of patients who received CPAP increased more rapidly than did mean FRC of those receiving CDB when compared to the values obtained following operation (p less than 0.05). Incentive spirometry did not increase FRC to a greater extent than did CDB. Roentgenographic evidence of atelectasis 72 hours postoperatively was observed in 23 percent of CPAP patients (five of 22) and 42 percent and 41 percent of patients who received CDB (eight of 19) and IS (nine of 22). Two patients (3 percent) developed pneumonia. The low incidence of pneumonia regardless of the type of therapy may be attributable to vigorous, vigilant respiratory care in a population at high risk for developing pneumonia. Frequency and supervision of respiratory therapy may be more important than the type of therapy delivered after upper abdominal operations. Mask CPAP offers advantages because it requires no effort from the patient, and therapy is not painful.

Abdomen↗
PubMed1984

Comparison of continuous positive airway pressure, incentive spirometry, and conservative therapy after cardiac operations.

Of 38 patients undergoing median sternotomy for cardiac operations all developed profound restrictive defects in pulmonary function during the first 72 h after tracheal extubation. Although decreased lung volumes were refractory to correction by vigorous, aggressive pulmonary therapy during this period, frequent and supervised treatment may prevent further deterioration in pulmonary function. The overall incidence of pneumonia was only 3% (1/38). Continuous positive airway pressure delivered by mask proved to be a nearly effortless form of postoperative respiratory therapy that was less painful than incentive spirometry or coughing and deep breathing, and therefore may be preferable.

Cardiopulmonary Bypass↗
PubMed1984

Pulmonary function before and after prolonged continuous positive airway pressure by mask.

This investigation examined whether prolonged continuous positive airway pressure (CPAP) applied by face mask could sustain an increase in functional residual capacity (FRC). Before median sternotomy, nine adults performed multiple-breath nitrogen washout to determine FRC and spirometry. The day after operation, lung volumes were measured before and 10 min after the 4-h application of 7.5 cm H2O of CPAP with a mask. Mean FRC, forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1), and FEV1/FVC after CPAP were similar to pretreatment values. Although CPAP can restore FRC to preoperative values, and did increase FRC in these patients, FRC deteriorates within 10 min after CPAP is removed. Therefore, when a sustained increase in FRC is desired after median sternotomy, CPAP should be applied without interruption.

Critical Care↗
PubMed1983

Continuous positive airway pressure improves oxygenation in dogs after the aspiration of blood.

Fourteen dogs were anesthetized, intubated, and breathed room air spontaneously. We then instilled 2 ml/kg of fresh nonheparinized donor blood into their tracheas. Seven dogs received no treatment and served as controls (group A); respiratory rate (RR) increased from 25 +/- 11 (mean +/- SD) to 103 +/- 33 breath/min, HR decreased from 179 +/- 28 to 136 +/- 42 beat/min, PaO2 decreased from 82 +/- 10 to 30 +/- 4 torr, pulmonary venous admixture (Qsp/Qt) increased from 0.14 +/- 0.10 to 0.72 +/- 0.06, and venous oxygen tension (PVO2) decreased from 46 +/- 4 to 22 +/- 5 torr 10 min after the aspiration of blood; all changes were statistically significant (p less than .05). After 4 h, RR and HR returned to control values, but PaO2 was only 58 +/- 10 torr. Cardiac output, oxygen consumption (VO2), and pulmonary and systemic BP and resistances were not significantly affected. Thirty-five min after the other 7 dogs aspirated blood (group B), 10 cm H2O of continuous positive airway pressure (CPAP) was applied while they breathed spontaneously. CPAP reduced Qsp/Qt to 0.31 +/- 0.10 and 0.15 +/- 0.11 30 and 90 min after its application, respectively (p less than .05). By 4 h, the PaO2 of group B dogs was 81 +/- 15 torr (p less than .05 compared with group A). CPAP also increased arteriovenous oxygen content difference (C[a-v]O2) compared with the nontreated dogs. Four hours after the aspiration of blood, all dogs were extubated. Twenty-four hours later, arterial blood gases were normal in all dogs of both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

Intermittent mandatory ventilation (IMV): a primary ventilatory support mode.

Respiratory therapy should be directed at underlying pathophysiology, not symptomatology. Mechanical ventilation, oxygen, and CPAP should be administered to patients independently and in appropriate amounts. Removal of each of these therapeutic interventions should occur in a similar fashion. The method for determining optimal mechanical ventilation, oxygen concentration, and CPAP level is not unlike that recommended for many other therapeutic interventions. Each should be applied to achieve a predetermined goal, each should be continually reevaluated, and each should be withdrawn when indicated. Optimal CPAP should be applied to improve matching of ventilation and perfusion and to improve pulmonary mechanics so that the requirement for oxygen and mechanical ventilation is reduced. A reduction in inspired oxygen concentration may prevent absorption atelectasis and allow more rapid discontinuation of mechanical ventilation and CPAP. Minimal mechanical ventilatory support eliminates iatrogenic respiratory alkalosis and improves distribution of ventilation. This approach minimizes the detrimental effects of mechanical ventilatory support on acid-base balance and cardiovascular function and decreases the possibility of pulmonary barotrauma. Twelve years of prospective evaluation have demonstrated numerous advantages of IMV. This approach has simplified the management of patients with compromised respiratory function and has decreased morbidity and mortality (10).

Hemodynamics↗