Search PubMed⌕ Search

Biomedical subjects

R L Chatburn

Publications and source records attributed to R L Chatburn.

34 records · Page 2Linked to original sources
PubMed1990

Patterns of practice in neonatal and pediatric respiratory care.

UNLABELLED: Because little information has been available regarding common respiratory care practices in neonatology and pediatrics, it has been difficult to develop departmental standards of care. We therefore conducted a national survey of current practices, hoping to establish whether any de facto standards exist in the U.S. METHODS: A 47-item multiple-choice survey instrument was mailed in 1988 to 689 U.S. hospitals that included all neonatal and perinatal high-risk centers. RESULTS: Response was received from 323 hospitals, for a 47% response rate. Some de facto standards do seem to exist, notably (1) q 2 h ventilator checks, (2) continuous measurement of oxygen concentration in oxygen hoods and ventilator circuits, (3) staffing ratio of four ventilator patients to one respiratory care practitioner, and (4) changing of ventilator circuits q 48 h. CONCLUSION: While we do not claim that such de facto standards have a scientific basis, we suggest that respiratory care services whose practices vary from the de facto standards should investigate why their own practices differ and whether they can be justified.

Child↗
PubMed1989

High-frequency jet ventilation in neonatal pulmonary hypertension.

To determine if high-frequency jet ventilation is beneficial in neonates with persistent pulmonary hypertension, we compared the ventilator settings, blood gas concentrations, and outcome of infants who met established criteria for a high predictive mortality. During a six-year period, 14 neonates who had severe respiratory failure and hypoxemia while receiving conventional ventilation were treated with high-frequency jet ventilation. Twenty-three comparable infants meeting the same criteria were treated exclusively with conventional ventilation. After initiation of high-frequency jet ventilation there was a significant reduction in mean airway pressure and partial pressure of arterial carbon dioxide (PaCO2). In contrast, neonates treated exclusively with conventional ventilation continued to have higher airway pressures and PaCO2. However, there was no difference in the alveolar-to-arterial oxygen gradient, air leakage, incidence of bronchopulmonary dysplasia, or duration of assisted ventilation or oxygen supplementation. Furthermore, mortality was comparable in both groups of infants. These preliminary observations suggest that high-frequency jet ventilation can reduce airway pressure and PaCO2 in neonates with persistent pulmonary hypertension but does not appear to improve outcome.

Carbon Dioxide↗
PubMed1989

Low frequency oscillatory ventilation through the suction channel of a pediatric bronchoscope.

To determine whether low frequency oscillatory ventilation (LFOV) may be safely applied through the suction channel of a pediatric fiberoptic bronchoscope, we devised a system using a combination of jet ventilation and constant air suction, both delivered with a single interface valve. The system was tested on an in vitro lung model and on rabbits. With tidal volumes of 12 mL, inadvertent increase in functional residual capacity (FRC) measured in the lung model was minimal. All rabbits experienced marked hypoventilation (PaCO2 62 +/- 2 torr) on introduction of the bronchoscope, which promptly improved with administration of LFOV (PaCO2 41 +/- 4 torr). That baseline FRC remained stable indicated that air trapping did not occur. We conclude that LFOV improves ventilation in rabbits during bronchoscopy without causing air trapping. A similar system might be applied during bronchoscopy in full-term and premature infants, thus facilitating safer and more complete visualization of their airways and preserving the possibility of obtaining samples by suction.

Animals↗
PubMed1988

Optimal positive end-expiratory pressure therapy in infants and children with acute respiratory failure.

Positive end-expiratory pressure (PEEP) has become a mainstay in the treatment of hypoxemic acute respiratory failure (ARF). Whereas PEEP improves arterial oxygen tension by decreasing intrapulmonary shunting, it may also impair cardiac output and hence decrease systemic oxygen transport. Inasmuch as optimizing oxygen transport is a goal of therapy in ARF, we sought to determine if the level of PEEP that results in maximal oxygen transport could be estimated from measurements of compliance of the respiratory system (Crs) or PaO2. We studied the effects of PEEP application on cardiorespiratory parameters in 15 children who required mechanical ventilation for ARF. Static Crs, PaO2, central venous and arterial blood pressures, indicator dilution cardiac index (CI), and oxygen transport were determined at 0, 3, 6, 9, 12, and 15 cm H2O PEEP. PaO2 increased significantly at PEEP levels greater than or equal to 9 cm H2O (p less than 0.001), while CI fell by 15% between 0 and 15 cm end-expiratory pressure (p less than 0.02). Crs and oxygen transport did not change significantly with increasing levels of PEEP. The level of PEEP resulting in maximal oxygen transport ranged from 0 to 15 cm H2O, and in all patients it corresponded to PEEP of best CI. At levels of PEEP above that associated with maximal oxygen transport, CI and oxygen transport fell significantly, while PaO2 continued to rise. No relationship between Crs and oxygen transport was observed. In our normovolemic patients with ARF, neither PaO2 nor Crs predicted PEEP of maximal oxygen transport.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1988

Bronchoscopic findings in infants treated with high-frequency jet ventilation versus conventional ventilation.

To identify tracheobronchial abnormalities associated with assisted ventilation, 40 infants with respiratory distress syndrome randomized to receive either short-term (48 hours) conventional or high-frequency jet ventilation were studied. Flexible fiberoptic bronchoscopy (n = 13) was performed and/or clinical and radiographic assessments were used to evaluate for laryngeal, tracheal, and bronchial lesions. There was no bronchoscopic evidence of necrotizing tracheobronchitis after either high-frequency jet ventilation (n = 8) or conventional ventilation (n = 5). Laryngotracheomalacia and nodular vocal cords were the most common abnormalities noted, and they occurred with equal frequency in both groups. Study infants who were not bronchoscoped had no clinical or radiographic evidence of tracheal or mainstem bronchial obstruction. One patient did have microscopic evidence of necrotizing tracheobronchitis at autopsy, however. It is concluded that short-term treatment of respiratory distress syndrome with high-frequency jet ventilation may be performed without undue risk of tracheobronchial injury.

Bronchi↗
PubMed1987

Randomized trial of high-frequency jet ventilation versus conventional ventilation in respiratory distress syndrome.

To compare high-frequency jet ventilation (HFJV) with pressure-limited time-cycled conventional ventilation (CV), we randomized 41 infants with clinical and radiographic evidence of respiratory distress syndrome during the first day of life to receive either HFJV or CV. Standardized ventilatory protocols were used for 48 hours, after which CV was administered to both groups. Despite comparable oxygenation (arterial/alveolar oxygen tension ratio), mean airway pressure was lower in the HFJV group (9 +/- 2 vs 13 +/- 2 cm H2O, P less than 0.001), and thus the arterial/alveolar oxygen tension ratio corrected for mean airway pressure was improved in the HFJV group (P less than 0.05). PaCO2 was lower during HFJV (37 +/- 3 vs 42 +/- 3 mm Hg, P less than 0.05) despite a comparable peak inspiratory pressure. The incidence of air leaks, progression of intraventricular hemorrhage, and mortality during the 48-hour period did not differ between the two groups. Bronchoscopies in eight infants given HFJV and five given CV revealed no microscopic evidence of necrotizing tracheobronchitis, but one infant given HFJV had evidence of necrotizing tracheitis at autopsy. We conclude that for 48 hours during the acute stage of respiratory distress syndrome, HFJV can maintain adequate gas exchange at lower mean airway pressure than during CV, without an increase in the incidence of side effects.

Clinical Trials as Topic↗
PubMed1986

Effect of varying inspiratory and expiratory times during high-frequency jet ventilation.

Although high-frequency jet ventilation may reduce barotrauma, the optimal ventilator settings at which complications are minimized have not been determined. To develop ventilator strategies applicable to the human infant, we studied six New Zealand rabbits before and after saline lung lavage. Changes in functional residual capacity (delta FRC) and airway pressure gradient (peak inspiratory pressure minus positive end-expiratory pressure) were measured while inspiratory time (TI) and expiratory time (TE) were varied. Frequencies of 120, 240, and 480 cycles per minute and inspiratory to expiratory ratios of 1:1, 1:3, 1:5, and 1:9 resulted in TI that varied from 12 to 250 msec, and TE from 62 to 450 msec. Analysis of variance demonstrated that as TI was shortened, a significantly higher airway pressure gradient was necessary to maintain a constant tidal volume. As TE was shortened, air trapping, as determined from both inadvertent positive end-expiratory pressure and delta FRC, significantly increased. Lung lavage increased the airway pressure gradient at each TI, but decreased air trapping at each TE. At no time did entrainment contribute to the delivered tidal volume. We conclude that a relatively narrow range of TI and TE may be necessary for optimal use of high-frequency jet ventilation to reduce airway pressures and minimize the risk of air trapping.

Animals↗
PubMed1986

Measurement of tidal volume during high-frequency jet ventilation.

The measurement of tidal volume during high-frequency jet ventilation is difficult due to the high-frequency components of the inspiratory flow. To validate tidal volume measured with a screen pneumotachograph placed on the expiratory limb, we simultaneously determined tidal volume with a body plethysmograph in seven anesthetized normal adult New Zealand rabbits before and after saline lung lavage. Four to six comparisons of tidal volume were obtained by varying peak inspiratory pressures at each combination of frequency (120, 240, and 480/min) and inspiratory to expiratory time ratio (1:1, 1:3, 1:5, 1:9). Overall, 90% of the tidal volumes measured with the pneumotachograph were within 10% of 1 ml of the volumes determined with the plethysmograph, independent of frequency, inspiratory to expiratory time ratio, and lung compliance. There was unidirectional outward flow at the pneumotachograph during inspiration when both normal and saline lavaged lungs were being ventilated, suggesting a lack of gas entrainment. We conclude that a pneumotachograph on the expiratory limb may be used to measure tidal volume and gas entrainment in vivo during high-frequency jet ventilation. Determination of tidal volume may serve to optimize ventilator settings during high-frequency jet ventilations and facilitate an understanding of the mechanism involved in gas exchange.

Animals↗
PubMed1986

Efficacy of computer-assisted management of respiratory failure in neonates.

We modified an algorithm for mechanical ventilation of infants with respiratory distress syndrome to create an interactive user-friendly computer program. To determine the effectiveness of this computer program, we evaluated the correction of deranged arterial blood gases in three groups of neonates: group I, treated before the introduction of the computer into the nursery; group II, managed by pediatric residents with the guidance of the computer program; group III, treated after the introduction of the computer into the nursery but managed without consideration of the computer output. Arterial blood gas values improved more frequently in the neonates managed with computer consultation (group II, 65/75, 87%) than in both control groups (group I, 37/57, 65%, P less than .005; and group III, 46/63, 73%, P less than .05). Furthermore, increases in ventilatory support in the presence of normal arterial blood gas values occurred only in patients managed without computer guidance. In a teaching institution, more effective care of neonates with respiratory failure may be facilitated by computer-assisted management of mechanical ventilators.

Blood Gas Analysis↗
PubMed1984

Decrease in airway pressure during high-frequency jet ventilation in infants with respiratory distress syndrome.

Using a crossover study design, we compared a system of high-frequency jet ventilation with appropriate humidification to pressure-limited conventional ventilation in 12 preterm infants with a birth weight of 1.9 +/- 0.6 kg and gestational age of 32 +/- 2 weeks who had severe respiratory distress syndrome. After a control period of conventional ventilation, high-frequency jet ventilation was administered for 1 to 3 hours at a constant rate (250/min) and inspiratory to expiratory time (1:3 or 1:4) in the same fraction of inspired oxygen as during conventional ventilation. Average peak inspiratory pressure decreased from 29 +/- 3 cm H2O during conventional ventilation to 20 +/- 4 cm H2O during high-frequency jet ventilation (P less than 0.001), whereas positive end expiratory pressure was unchanged, resulting in a reduction in mean airway pressure from 14 +/- 3 to 10 +/- 2 cm H2O (P less than 0.001). There was a simultaneous decrease in PaCO2 (39 +/- 4 to 34 +/- 4 mm Hg, P less than 0.01), but PaO2 did not change. These data indicate that short-term high-frequency jet ventilation maintains gas exchange in infants with respiratory distress syndrome despite a lower PIP and Paw, and results in smaller airway pressure swings than during conventional ventilation. Thus, high-frequency jet ventilation may offer hope for reducing barotrauma in this population.

Blood Gas Analysis↗
PubMed1984

An in-hospital evaluation of the sonic mist ultrasonic room humidifier.

It is generally recognized that nebulizers can be a source of nosocomial infection. 'Cold mist' room humidifiers are a particular problem because they are difficult to sterilize. We evaluated a new device, the Sonic Mist ultrasonic room humidifier, to determine how quickly it became contaminated during continuous use by a population of cystic fibrosis patients. In addition, the study was designed to test the effectiveness of placing a bacterial filter on the air inlet of the humidifier. We found that the entire humidifier could withstand repeated gas sterilization. Data obtained from 18 humidifiers involving cystic fibrosis patients indicate that the earliest humidifier contamination occurred after 5 days of continuous use. Although all patients had large numbers of gram-negative bacilli as predominant sputum flora, only 7 episodes of contamination were found during 34 humidifier-use periods. Three units equipped with filters became contaminated (5-7 days) and four unfiltered units became contaminated (6-11 days), indicating that the use of an inlet filter made no apparent difference. The organisms recovered from contaminated units were not found as sputum flora and would not generally be considered of clinical significance in cystic fibrosis sputum cultures. Probable sources of the organisms were room dust and hand contamination. A further test of the inlet filter was performed by exposing filtered and unfiltered units to mist from an intentionally contaminated humidifier. Again, the contamination rate was low and the filter apparently made no difference. These results indicate that the Sonic Mist humidifier may be appropriate for hospital use if adequate sterilization and contamination-monitoring practices are followed.

Cross Infection↗
PubMed1983

A new patient-circuit adapter for use with high frequency jet ventilators.

Current techniques of connecting a patient's endotracheal tube to the delivery circuit of a high frequency jet ventilator have several disadvantages. We describe a rigid, interchangeable adapter with a built-in jet injector that connects to any type or size of endotracheal tube. The device is reusable and avoids some of the disadvantages, such as catheter kinking, difficulty in accommodating injectors of different diameters, and tracheal tube obstruction, inherent in other commonly used techniques. It has been used successfully on 44 patients ranging in size from premature infants to adults.

Respiration, Artificial↗
PubMed1982

Mean airway pressure: theoretical considerations.

Several recent articles have suggested the use of mean airway pressure (Paw) as an index of the physiological effect of ventilating pressures. To facilitate the understanding of this parameter, operational formulas are derived by applying the explicit, mathematical definition of Paw to several clinically relevant pressure waveforms. These formulas are then generalized to apply to any wave shape. It is shown that any pressure waveform can be characterized by a waveform constant K, knowledge of which permits the estimation of Paw using information from either airway pressure recordings or the control settings and pressure gauges on conventional ventilators.

Air Pressure↗
PubMed1982

Modification of a ventilator pressure monitoring circuit to permit display of mean airway pressure.

We modified the pressure gauge of a Bourns BP200 infant ventilator to allow it to display either mean airway pressure (Paw) or conventional airway pressure fluctuations. The modification consists of a pneumatic toggle switch and a needle valve connected in-line to the pressure gauge. When the switch is activated, the resistance of the needle valve and the compliance of the pressure gauge combine to form a pneumatic low-pass filter, whose output is read as Paw on the pressure gauge.

Humans↗
PubMed1982

A heat and humidification system for high frequency jet ventilation.

The clinical application of high frequency jet ventilation (HFJV), especially in pediatrics, has been hindered by the lack of adequate heating and humidification of the delivered gas. A technique of injecting particulate water into the gas from the jet ventilator has been described in the literature. However, it has been used primarily on adults and may cause fluid overload or hypothermia when used on infants. We describe a device for use during HFJV that provides gas (free of particulate water) to the patient at or near body temperature, with a relative humidity of 91%. This system has been used on 34 persons (14 premature infants, 17 small children, and 3 adults) without complications associated with improper conditioning of inspired gas.

Adult↗