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Biomedical subjects

M C Stock

Publications and source records attributed to M C Stock.

31 records · Page 2Linked to original sources
PubMed1987

Airway pressure release ventilation.

Airway pressure release ventilation (APRV) delivers continuous positive airway pressure (CPAP) and may support ventilation simultaneously. This investigation tested whether, after acute lung injury (ALI), APRV promotes alveolar ventilation and arterial oxygenation without increasing airway pressure (Paw) above the CPAP level and without depressing cardiac function. Ten anesthetized dogs randomly received either intermittent positive-pressure ventilation (IPPV) or APRV. APRV was delivered with a continuous-flow CPAP system. Expiration occurred when a switch in the expiratory limb opened and Paw decreased to near-ambient, which decreased lung volume. After baseline data collection, ALI was induced by infusing oleic acid iv. Two hours later, IPPV and APRV were administered randomly, and data were collected. With normal lungs, APRV and IPPV achieved similar gas exchange and hemodynamic function. During ALI, arterial oxygenation was improved, and peak Paw which did not exceed the CPAP level, was lower during APRV. Similar minute ventilations were delivered by both modes but resulted in lower PaCO2 with APRV. Thus, APRV decreased physiologic deadspace ventilation. Hemodynamic status was similar during both modes. Therefore, APRV is an improved method of oxygenation and ventilatory support for patients with ALI that will allow unrestricted spontaneous ventilation and may decrease the incidence of barotrauma.

Animals↗
PubMed1987

Is 50% oxygen harmful?

Pulmonary gas exchange after tracheal extubation was evaluated in 25 patients to determine the effect of 50% oxygen administered during mechanical ventilation following aortocoronary bypass grafting. Twenty-five patients received postoperative mechanical ventilation for 16 to 24 h, 13 with an inspired oxygen fraction (FIO2) of no more than 0.30 and 12 with an FIO2 of 0.50. After tracheal extubation, all patients spontaneously breathed room air (FIO2 0.21). Postextubation the calculated venous admixture of patients who had received 50% oxygen (0.20 +/- 0.03 [SD]) was significantly (p less than .01) greater than that calculated for patients who received lower oxygen concentrations (0.13 +/- 0.04). Consequently, the PaO2 of patients who had received 50% oxygen (60 +/- 5 torr) was significantly (p less than .03) lower than the PaO2 of patients who had received no more than 30% oxygen (66 +/- 7 torr). Thus, administration of 50% oxygen, supposedly nontoxic, to mechanically ventilated patients may cause impairment of pulmonary gas exchange after tracheal extubation. Although high concentrations of supplemental oxygen are sometimes required, unnecessary elevation of FIO2 is not likely to significantly increase oxygen delivery and may contribute to postextubation pulmonary dysfunction.

Adult↗
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↗
PubMed1986

Perioperative complications of elective tracheostomy in critically ill patients.

This study was designed to examine prospectively the incidence of perioperative complications associated with elective tracheostomy in critically ill patients. An experienced surgeon and anesthesiologist participated in every tracheostomy procedure. In 81 procedures, there was no loss of airway control for greater than 20 sec, no airway obstruction, no blood loss exceeding 50 ml, and no aspiration. One patient (1.2%) had cardiovascular instability. During the next 48 h, two patients (2.4%) required wound packing to control hemorrhage but did not require blood transfusion and two patients (2.4%) had evidence of supraclavicular subcutaneous emphysema that was physiologically inconsequential. There was no perioperative mortality or major morbidity associated with the tracheostomy procedure. We conclude that, under controlled conditions, elective tracheostomy can be performed safely in critically ill patients.

Adolescent↗
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↗
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↗