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Biomedical subjects

D J Strieder

Publications and source records attributed to D J Strieder.

At least 19 recordsLinked to original sources
PubMed1993

Regional lung mechanics and gas transport in lungs with inhomogeneous compliance.

The effect of respiratory frequency (f) on the distributions of ventilation, regional gas transport, lung volume, and regional impedance was assessed with positron imaging in lungs with nonuniform lung mechanics after unilateral lung lavage. Supine dogs were studied during eucapnic oscillatory ventilation at f between 1 and 15 Hz and at a constant mean airway pressure of 5 cmH2O. Substantial differences in mean lung volume and tidal volume (VT) between lavaged and control lungs were found at all f values, but pendelluft never exceeded 2% of mouth flow. For f < or = 10 Hz, VT distributed in direct proportion to lung volume, whereas gas transport per unit of lung volume, measured from washout maneuvers, was reduced by 20% in the lavaged lung. At 15 Hz, however, the distributions of VT and gas transport approached equality between both lungs. Regional impedance was analyzed with a model that included a Newtonian resistance, an inertance, and Hildebrandt's model of tissue viscoelasticity. The data obtained from this work provide useful insights with respect to the mechanisms of gas transport during high-frequency ventilation and suggest the impact of operating frequency in clinical situations where substantial interregional heterogeneity in lung compliance could be expected.

Animals↗
PubMed1990

Does lithium carbonate affect the ion transport abnormality in cystic fibrosis?

Lithium is known to affect several aspects of cellular regulation which may be related to ion channel function in epithelial cells. To determine whether the ion transport abnormality in cystic fibrosis (CF) is affected by lithium with resultant changes in clinical status, 36 CF patients, 12-37 years old, were enrolled in a 14 week, double-blind, placebo-controlled trial. Eighteen patients were randomly assigned to receive lithium carbonate for 10 weeks. At the end of therapy their average serum lithium concentration was 0.56 +/- 0.06 mmol (SEM) per liter. Their sweat chloride concentration fell from 92.1 +/- 4.8 mmol per liter to 87.4 +/- 4.0 mmol per liter after 10 weeks of therapy (P = 0.07) and rose to 94.4 +/- 3.5 mmol per liter 4 weeks after end of therapy (P less than 0.001 compared to results at end of therapy). Their forced vital capacity (FVC) fell from 72 +/- 5.3% of predicted to 66 +/- 5.1% of predicted after 4 weeks of therapy (P less than 0.01), and their forced expiratory volume in one second (FEV1) fell from 56 +/- 5.5% of predicted to 51 +/- 5.5% of predicted after 4 weeks of therapy (P less than 0.01). In a non-blind assessment, performed 19 weeks after the end of therapy, their FVC and FEV1 had risen and were not significantly different from baseline. Sweat chloride, FVC, and FEV1 remained unchanged in the placebo group throughout the period of study.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

In vivo estimation of tracheal distensibility and hysteresis in normal adults.

We used the acoustic reflection technique to measure the cross-sectional area of tracheal and bronchial airway segments of eight healthy adults. We measured airway area during a slow continuous expiration from total lung capacity (TLC) to residual volume (RV) and during inspiration back to TLC. Lung volume and esophageal pressure were monitored continuously during this quasi-static, double vital capacity maneuver. We found that 1) the area of tracheal and bronchial segments increases with increasing lung volume and transpulmonary pressure, 2) the trachea and bronchi exhibit a variable degree of hysteresis, which may be greater or less than that of the lung parenchyma, 3) extrathoracic and intrathoracic tracheal segments behaved as if they were subjected to similar transmural pressure and had similar elastic properties, and 4) specific compliance (means +/- SE) for the intrathoracic and bronchial segments, calculated with the assumption that transmural pressure is equal to the transpulmonary pressure, was significantly (P less than 0.05) smaller for the intrathoracic segment than for the bronchial segment: (2.1 +/- 2.0) X 10(-3) cmH2O-1 vs. (9.1 +/- 2.1) X 10(-3) cmH2O-1. Direct measurements of airway area using acoustic reflections are in good agreement with previous estimates of airway distensibility in vivo, obtained by radiography or endoscopy.

Acoustics↗
PubMed1986

A general dimensionless equation of gas transport by high-frequency ventilation.

To identify a general relationship between eucapnic oscillatory flow (Vosc) and frequency (f) in high-frequency ventilation (HFV), we searched the literature for eucapnic HFV data in different mammalian species. We found suitable results for rat, rabbit, monkey, dog, human, and horse, which we expressed in terms of two dimensionless variables, Q = Vosc/Va and F = f/(VA/VD), with VA the alveolar ventilation and VD the volume of the conducting airways. The experimental HFV data define the linear regression equation in Q = 0.54 In F + 0.92 (R = 0.94). Krogh's equation for conventional ventilation (CV), Vosc = VA + fVD, in dimensionless terms becomes Q = 1 + F, which is valid for low F. The intersection of the CV and HFV equations at F = 5.0 defines a transition frequency, ft = 5.0 (VA/VD). At that point the alveolar ventilation per breath, VA/f, represents 20% of VD, and tidal volume (VT) equals 1.20 VD. For eucapnia ft ranges from 5.9 Hz in the rat to 0.9 Hz in the dog. The dimensional form of our HFV equation, VA = 0.13 (VT/VD)1.2 (VTf) is very similar to other empirical equations reported for dogs in noneucapnic settings. Therefore the dimensionless equation should also be valid within a species at noneucapnic settings.

Animals↗
PubMed1986

Effects of mean airway pressure on gas transport during high-frequency ventilation in dogs.

In 10 anesthetized, paralyzed, supine dogs, arterial blood gases and CO2 production (VCO2) were measured after 10-min runs of high-frequency ventilation (HFV) at three levels of mean airway pressure (Paw) (0, 5, and 10 cmH2O). HFV was delivered at frequencies (f) of 3, 6, and 9 Hz with a ventilator that generated known tidal volumes (VT) independent of respiratory system impedance. At each f, VT was adjusted at Paw of 0 cmH2O to obtain a eucapnia. As Paw was increased to 5 and 10 cmH2O, arterial PCO2 (PaCO2) increased and arterial PO2 (PaO2) decreased monotonically and significantly. The effect of Paw on PaCO2 and PaO2 was the same at 3, 6, and 9 Hz. Alveolar ventilation (VA), calculated from VCO2 and PaCO2, significantly decreased by 22.7 +/- 2.6 and 40.1 +/- 2.6% after Paw was increased to 5 and 10 cmH2O, respectively. By taking into account the changes in anatomic dead space (VD) with lung volume, VA at different levels of Paw fits the gas transport relationship for HFV derived previously: VA = 0.13 (VT/VD)1.2 VTf (J. Appl. Physiol. 60: 1025-1030, 1986). We conclude that increasing Paw and lung volume significantly decreases gas transport during HFV and that this effect is due to the concomitant increase of the volume of conducting airways.

Animals↗
PubMed1985

Tracheal bronchus: association with respiratory morbidity in childhood.

An aberrant right upper lobe (RUL) bronchus arising from the trachea (tracheal bronchus) can be responsible for recurrent pneumonia. In this hospital, 2% of children requiring bronchoscopy for respiratory symptoms are found to have a tracheal bronchus, which is frequently thought to be an incidental finding. We reviewed findings in 18 patients to determine when a tracheal bronchus is of clinical significance. The age at presentation ranged from 1 day to 54 months (mean 17 months). The children had recurrent pneumonia (nine), stridor (six), respiratory distress (two) and a thoracic mass (one). Other congenital abnormalities were present in 14, including Down syndrome (two), tracheoesophageal fistula (two), and fused or hypoplastic first and second ribs (four). Recurrent RUL pneumonia was present in five. Bronchiectasis or bronchial stenosis was shown by bronchography in four of five; in all five the right upper lobe was surgically resected, with resolution of the recurrent pneumonias. The presence of a clinically significant tracheal bronchus should be considered in every child with recurrent RUL pneumonia, especially in children with Down syndrome or rib abnormalities; if bronchiectasis or bronchial stenosis is found, surgical resection should be performed.

Bronchi↗
PubMed1985

Postural hypoxemia in cystic fibrosis.

We measured arterial blood gases in the sitting and supine position in 33 patients with cystic fibrosis (CF). Arterial PO2 ranged from 48 to 97 mm Hg in the sitting position and fell by 1 to 23 mm Hg in 26 patients, rose by 1 to 4 mm Hg in five, and was unchanged in two when supine. Mean PO2 change for the group was a 6.5 (+/- 6.8) mm Hg decrease (sitting to supine), and substantial falls were more likely to occur in patients with mild to moderate, rather than severe, obstructive lung disease. There were no significant changes in PCO2 or pH with posture. Postural hypoxemia was not completely explained by greater airway closure as measured by the single-breath nitrogen method in 11 patients or by worse radiographic change in the upper lung zones. Arterial PO2 should always be compared in the same body position in CF patients, preferably while supine. Postural hypoxemia also may contribute to the lower PO2 at night in CF patients.

Adolescent↗
PubMed1984

Empyema in children: clinical course and long-term follow-up.

Sixteen patients, aged 1 month to 15 years, were studied to determine the clinical course and long-term outcome of empyema in previously healthy children. The pathogens responsible were Haemophilus influenzae type b (seven patients), Staphylococcus aureus (five patients), Streptococcus pneumoniae (three patients), and viridans group Streptococcus (one patient). All patients had loculated fluid showing on chest roentgenographs. Chest tube drainage yielded 20 to 1,495 mL (mean 293 mL) during the first three days, accounting for 83% of total drainage. Chest tubes were removed after three to 17 days (mean ten days). Only slight roentgenographic improvement showed during chest tube drainage. Three patients required an open thoracotomy because of an unsatisfactory clinical response. Hospitalization ranged from eight to 77 days (mean 25 days). All patients had residual pleural thickening shown on chest roentgenographs taken at discharge. Thirteen patients were seen 5 to 140 months (mean 66 months) after discharge. Findings from physical examination were normal in 12 of the 13 patients. Pulmonary function tests in ten of the 13 patients revealed (mean percent predicted +/- 1 SD): vital capacity 92 +/- 12, residual volume 85 +/- 31, total lung capacity 92 +/- 13, peak flow rate 96 +/- 17, forced expiratory volume in 1 second 90 +/- 13, and maximal mid-expiratory flow rate 93 +/- 25. In all but one patient, findings on chest roentgenograms were normal or showed slight pleural thickening. Children with loculated empyema can be treated successfully with antibiotics and chest tube drainage. Few patients require open drainage, and further surgery is rarely required. The long-term outcome is excellent.

Adolescent↗
PubMed1983

Management of pneumothorax in cystic fibrosis.

The increased longevity of patients with cystic fibrosis has resulted in a concomitant increase in the frequency with which pneumothorax is seen. While several approaches to this problem have been available from both a medical and surgical standpoint, unsettled questions remain regarding the efficacy of various modalities of therapy. A review of our own experience with 170 episodes of pneumothorax has provided a basis for proposing what appears to be a reasoned approach to therapy. During the past 12 years, 65 patients ages 5 to 32 years experienced 170 episodes of pneumothorax. Of the 211 trials of treatment, all yielded a high rate of initial resolution (70% to 100%) but rates of recurrence were high. The recurrence rates were: observation 60%, thoracentesis 79%, trochar thoracotomy 63%, tetracycline sclerosis 86%, and silver nitrate 43%. Quinacrine sclerosis yielded an acceptable recurrence rate of 12.5% and partial pleurectomy had no recurrence. There was no statistical difference in the pulmonary function parameters determined before pneumothorax and after chemical pleurodesis or partial pleurectomy. Based upon the data obtained in this review, we recommend that initial management of the pneumothorax include evacuation of the pneumothorax using a chest tube and then chemical pleurodesis using quinacrine sclerosis. In those cases where this pleurodesis fails, upper-partial pleurectomy with obliteration of pleural blebs via a limited thoracentesis is the treatment of choice. An occasional patient requires a concomitant lobectomy.

Adolescent↗
PubMed1983

Clinical and bacteriological responses to three antibiotic regimens for acute exacerbations of cystic fibrosis: ticarcillin-tobramycin, azlocillin-tobramycin, and azlocillin-placebo.

In a randomized, double-blind study, cystic fibrosis patients 11-30 years of age with an acute exacerbation of their pulmonary disease were treated with either ticarcillin-tobramycin, azlocillin-tobramycin, or azlocillin-placebo for 10 days. There was significant improvement in Shwachman scores and pulmonary function tests. Concentrations of sputum bacteria were significantly reduced, but after therapy patients had a mean of 10(7) bacteria/ml of sputum. Pseudomonas was transiently eliminated in only one patient. The three regimens had similar impacts on pulmonary function and sputum bacterial concentration. Antibiotic resistance was noted more frequently in the azlocillin-placebo group, but this trend was not statistically significant. Improvement in pulmonary function did not correlate with bacteriological response. Four weeks after discharge, 62% of the improvement in forced expiratory volume in one second and 75% of the improvement in vital capacity remained, but concentrations of sputum bacteria had returned to pretreatment levels, and antibiotic-resistant bacteria persisted.

Acute Disease↗
PubMed1983

Randomized, double-blind evaluation of azlocillin for the treatment of pulmonary exacerbations of cystic fibrosis.

Patients with cystic fibrosis hospitalized because of deterioration in their pulmonary disease were randomly assigned to receive ten days of intravenous antibiotic therapy with either ticarcillin plus tobramycin (previously the standard regimen at our hospital), azlocillin plus tobramycin or azlocillin plus placebo. Pulmonary function and microbiological responses were similar in the three treatment groups, although patients receiving azlocillin and placebo tended to have a smaller reduction in the concentration of bacteria in the sputum and a greater rate of acquisition of antibiotic-resistant organisms. Overall, in-hospital treatment was associated with a significant improvement in Shwachman score, pulmonary function tests, and PO2. Improvement was noted by day 5 of therapy, continued through day 10, and was partially maintained at follow-up clinic visit one month after discharge. There was also a statistically significant reduction in sputum bacterial concentration, but patients cultured at the conclusion of antibiotic therapy still had a mean of 10(7) cfu/ml in sputum. Pseudomonas aeruginosa, the principal pathogen recovered from sputum cultures in this study, was transiently suppressed to sub-detectable levels in only one patient. There was no correlation between microbiological response and change in any parameter of pulmonary function. By follow-up clinic visit, sputum bacteria had returned to pre-treatment levels, and antibiotic-resistant organisms persisted in all patients from whom they had been recovered during hospitalization.

Adolescent↗
PubMed1983

Respiratory system impedance from 4 to 40 Hz in paralyzed intubated infants with respiratory disease.

To describe the mechanical characteristics of the respiratory system in intubated neonates with respiratory disease, we measured impedance and resistance in six paralyzed intubated infants with respiratory distress syndrome, three of whom also had pulmonary interstitial emphysema. We subtracted the effects of the endotracheal tube after showing that such subtraction was valid. Oscillatory flow was generated from 4 to 40 Hz by a loudspeaker, airway pressure was measured, and flow was calculated from pressure changes in an airtight enclosure mounted behind the flow source (speaker plethysmograph). After subtraction of the endotracheal tube contribution, resistance ranged from 22 to 34 cmH2O liter-1 s; compliance from 0.22 to 0.68 ml/cmH2O; and inertance from 0.0056 to 0.047 cmH2O liter-1 s2. Our results indicate that, for these intubated infants, the mechanics of the respiratory system are well described as resistance, compliance, and inertance in series. Most of the inertance, some of the resistance, and little of the compliance are due to the endotracheal tube. When the contribution of the endotracheal tube is subtracted, the results are descriptive of the subglottal respiratory system. These data characterize the neonatal respiratory system of infants with respiratory distress syndrome (with or without pulmonary interstitial emphysema) in the range of frequencies used during high frequency ventilation.

Airway Resistance↗
PubMed1982

Pneumothorax in cystic fibrosis: management and outcome.

We reviewed our experience over the past 12 years to determine the best method of management, to determine the morbidity and the physiologic outcome of medical vs surgical treatment of pneumothorax complicating CF, and to assess the influence of age, sex, and Shwachman scores on survival. Sixty-five patients, ages ranging from 5 to 32 years (mean 18 years). Shwachman scores ranging from 25 to 87 (mean 57), and a male-female ratio of 1:1, experienced 170 pneumothoraces, 93 first episodes, and 77 recurrences, requiring 211 trials of management. All methods of management except needle aspiration resulted in a fair rate of resolution (70 to 100%), but recurrence rates were high for observation (60%), needle aspiration (79%), trocar thoracotomy (63%), tetracycline sclerosis (86%), and silver nitrate sclerosis (43%). The recurrence rates were 12.5% for quinacrine sclerosis and 0% for parietal pleurectomy. Quinacrine sclerosis and parietal pleurectomy were the most effective methods of management. There was no significant difference in pulmonary function before pneumothorax and after pleural sclerosis or parietal pleurectomy. Age, sex, and severity of pulmonary disease were all independent variables influencing prognosis. Severity of disease, rather than the occurrence of a pneumothorax, appears to be the major cause of death. We recommend that quinacrine sclerosis should be considered for management of the first pneumothorax, and parietal pleurectomy if it fails.

Adolescent↗
PubMed1982

Interaction of oscillatory and unidirectional flows in straight tubes and an airway cast.

Because oscillatory resistance of the respiratory system is often measured during tidal breathing, we studied the interaction between simultaneous oscillatory and unidirectional flows in three straight tubes (radius ranging from 0.3025 to 0.679 cm and length either 30.7 or 173 cm) and a central airway cast (tracheal radius 0.685 cm). Oscillatory flow was generated by a loudspeaker, airway pressure was measured with a transducer, and flow was calculated from pressure changes in an airtight enclosure mounted behind the flow source (loudspeaker plethysmograph). Oscillatory resistance, i.e., the real part of impedance, was determined from 2 to 64 Hz. In the absence of unidirectional flow, frequency dependence of resistance was observed for the two 30.7-cm-long tubes to match previously published theory. Frequency dependence of resistance for the airway cast was similar to that of the tube of comparable inlet radius. In the presence of unidirectional flow, oscillatory resistance at low frequency was independent of frequency and determined by the magnitude of the unidirectional flow. Oscillatory resistance at high frequency was frequency dependent but still influenced by the magnitude of the unidirectional flow. Our results indicate that the presence of unidirectional flow alters the oscillatory resistance of tubes and the cast at any given frequency, presumably by changing the shape of the boundary layer.

Airway Resistance↗
PubMed1980

Sleep hypoxemia in young adults with cystic fibrosis.

Hypoxemia, obstructive apnea, and disordered breathing during sleep have been documented in adult patients with chronic obstructive pulmonary disease. We studied sleep, oxygen saturation, and breathing in nine patients (ages 17 to 26 years) with cystic fibrosis (CF) lung disease by means of all-night polygraphic tracings. Two had brief episodes of oxygen desaturation during rapid eye movement (REM) sleep, and one patient with severe disease had prolonged desaturation with episodic worsening associated with disordered breathing in REM sleep and with cough. No patient had apnea or any evidence of upper airway obstruction, in contrast with studies of older patients. In three patients, nocturnal coughing contributed to disruption of sleep cycles. Sleep oxygen desaturation may contribute to the development or progression of cor pulmonale in some patients with CF, but it seems to be most severe only in those with advanced disease.

Adult↗