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Biomedical subjects

W W Fox

Publications and source records attributed to W W Fox.

86 records · Page 5Linked to original sources
PubMed1976

Optimum levels of CPAP for tracheal extubation of newborn infants.

Arterial oxygen tension and functional residual capacity were studied in 16 intubated, spontaneously breathing newborn infants recovering from respiratory disease. Studies were made at 2 cm H2O continuous positive airway pressure, at zero end expiratory pressure, and following extubation. The study showed that PaO2 and FRC at 2 cm H2O CPAP were the same as observed following extubation, but that both values were significantly lower at ZEEP.

Humans↗
PubMed1975

Treatment of laryngotracheobronchitis (croup). Use of intermittent positive-pressure breathing and racemic epinephrine.

Use of racemic epinephrine hydrochloride (Vaponefrin), delivered by intermittent positive-pressure breathing, in the treatment of laryngotracheobronchitis (croup) produced acute beneficial results in a controlled study. However, symptoms often recurred within two hours, suggesting that this form of treatment should not be used in the emergency room and the patient then sent home. This treatment had no effect on arterial oxygen gas pressure. The changes in clinical status 24 to 36 hours after admission into the study were similar for the patients in the treatment and control groups, suggesting that the natural history of the disease was not drastically altered by this form of treatment.

Acute Disease↗
PubMed1975

Early versus late introduction of continuous negative pressure in the management of the idiopathic respiratory distress syndrome.

To evaluate the effectiveness of the early application of continuous negative pressure about the thorax, 23 infants with the idiopathic respiratory distress syndrome who had adequate alveolar ventilation were assigned to early or late application of CNP. There were 11 infants in the early CNP and 12 in the late CNP group. There were no differences between the two groups with respect to birth weight, gestational age, age at admission to the study, initial FIO2 requirements, or initial PaO2, PaCo2, and AaPO2. None of the ENCP patients required mechanical ventilation, whereas four of the LCNP group did so. The FIO2 requirements were significantly less for the ECNP infants when compared to the LCNP ones. The mean duration of FIO2 requirements greater than 0.6 was 28.3 hours for those receiving ECNP and 60.7 hours for those in LCNP (P LESS THAN 0.05). This study suggests that the course of RDS may be modified by the early application of CNP.

Carbon Dioxide↗
PubMed1975

The therapeutic application of end-expiratory pressure in the meconium aspiration syndrome.

The effectiveness of end-expiratory pressure (EEP) in relieving hypoxemia in the meconium aspiration syndrome (MAS) was studied in 14 patients with the disorder. These infants demonstrated a direct, mean PO2 response of 12 torr/cm H2O EEP. A maximum PO2 response was observed in an EEP range of 4 to 7 cm H2O. EEP was equally effective whether patients were breathing spontaneously or were being mechanically ventilated. EEP is useful in the treatment of hypoxemia in the infants with meconium aspiration syndrome.

Blood Gas Analysis↗
PubMedDate not supplied

Physiologic effects of terbutaline on pulmonary function of infants with bronchopulmonary dysplasia.

This study defines the physiologic changes in pulmonary mechanics induced by subcutaneous terbutaline administration in ventilator-dependent infants with severe bronchopulmonary dysplasia (BPD). Eight such infants (mean +/- SEM weight = 2.56 +/- 0.32 kg, postnatal age = 13.0 +/- 3.2 weeks) were chosen for the study. Pulmonary mechanics and arterial blood gases were measured in the control state and at 30 and 60 minutes following the subcutaneous injection of 5 micrograms/kg terbutaline. There was a significant (p less than 0.001) improvement in lung compliance from baseline values at 30 minutes and at 60 minutes (38%). A significant (p less than 0.05) decrease of 23% in the average pulmonary resistance at 30 minutes and a 26% decrease at 60 minutes from control values were observed. An increase in the I/E ratio occurred in all patients at 60 minutes (p less than 0.01). In addition, clinical improvement was noted in six of eight infants. Administration of terbutaline demonstrated a significant improvement in the pulmonary mechanics of infants with severe BPD.

Bronchopulmonary Dysplasia↗
PubMedDate not supplied

Effect of high-frequency jet ventilation on preterm and rabbit tracheal mechanics.

The effect of high-frequency jet ventilation (HFJV) on both tracheal dimensions and mechanics was evaluated in preterm and term rabbit airways. Seven tracheal segments were studied at 27 days (group I) and 31 days (group II) of gestation, respectively. Tracheal dimensions and segmental pressure-volume relationships were determined before and after 60 minutes of HFJV (peak pressure 20 cm H2O; mean airway pressure 6.7 to 6.8 cm H2O at 10 Hz). Both tracheal lengths and diameters increased significantly (p less than 0.01) in each group and resulted in increased tracheal volumes: 109% in group I (p less than 0.01) and 60% in group II (p less than 0.01). The mean specific tracheal compliance decreased in group I, from 0.036 cm H2O-1 to 0.015 cm H2O-1 (p less than 0.01), and in group II from 0.029 cm H2O-1 to 0.021 cm H2O-1 (p less than 0.01). Furthermore, the collapsing transmural pressure (the pressure required for total collapse of tracheal segments) decreased significantly (p less than 0.01) in both groups. These data demonstrate significant dimensional and mechanical deformation of tracheal segments after HFJV. An increased propensity toward collapsibility is also observed following HFJV. These changes are similar to those with tracheomalacia. The influence of such deformation on tracheal gas flow during HFJV needs to be further investigated.

Animals↗
PubMedDate not supplied

Use of caffeine in infants unresponsive to theophylline in apnea of prematurity.

Eleven premature infants with severe apnea unresponsive to therapeutic theophylline levels were studied to determine if caffeine is an effective treatment in such cases. Apnea was documented and quantitated with thermistor-pneumocardiograms measuring heart rate, thoracic impedance, and nasal air flow. Infants with prolonged central or mixed apnea were then treated with caffeine and restudied. Caffeine reduced the total number of apneic episodes of greater than 10 sec duration by 80% (P less than 0.01) and prolonged episodes of apnea (greater than 20 sec) by 88% (P less than 0.05). These data suggest that caffeine may be effective in the management of apnea of prematurity, particularly the prolonged type, unresponsive to theophylline.

Apnea↗
PubMedDate not supplied

Effect of early furosemide administration in neonates with respiratory distress syndrome.

The effect of early furosemide-induced diuresis was prospectively evaluated in 39 neonates less than 24 hr of age with clinical respiratory distress syndrome (RDS) who received either four doses of furosemide (1 mg/kg) or no diuretic. Measurements of FiO2 alveolar-arterial oxygen gradient (P[A-a]O2), peak inspiratory pressure (PIP), and urine output as a fraction of intake (O/I) were averaged for every 8 hr. The furosemide group overall showed a significant decrease (P less than 0.01) in FiO2, P[A-a]O2, and PIP with an earlier (32 hr vs 52 hr) and more pronounced diuresis (35% greater O/I) when compared to the controls. This effect was accentuated in the subgroup with 1,000-1,500 g birth weight (significantly lower FiO2 and P(A-a)O2 from 16 to 48 hours), while no increase in urine output was observed for the infants weighing less than 1,000 g. A significant reduction in supplemental oxygen and need for ventilatory support at 96 hr of age was observed in the furosemide-treated, less than 1,500-g infants. The incidence of patent ductus arteriosus was not increased following furosemide therapy, and no significant difference in echocardiographic parameters was observed in 21 infants from both groups, who were followed daily during the first week of life. This study suggests that early furosemide-induced diuresis, particularly in infants weighing 1,000-1,500 g at birth, promotes improvement in pulmonary functions in RDS and leads to faster reduction in oxygen and ventilatory support.

Birth Weight↗
PubMedDate not supplied

The PaO2 response to changes in end expiratory pressure in the newborn respiratory distress syndrome.

To quantitate the effect of changes in end-expiratory pressure (EEP) upon PaO2 in infants with the respiratory distress syndrome, arterial blood gas (ABG) data was reviewed in 28 neonates. A total of 94 ABG specimen pairs were analyzed (specimen I taken before EEP adjustment; specimen II taken after EEP change). An overall change in PaO2 of 15 torr was noted per cm H2O change in EEP. Patients in whom the level of EEP was low (0-3 cm H2O) at the time of Sample I had a greater change in PaO2 (p less than 0.01) than infants whose Sample I ABG was taken at mid-range of EEP (4-6 cm H2O) or at high ranges (7-12 cm H2O). At the high ranges of EEP a minimal and variable PaO2 response was observed. The PaO2 response was not statistically different between neonates on controlled ventilation and those breathing spontaneously. Survivors had a greater PaO2 response than did nonsurvivors, but because of the variables affecting respiratory distress syndrome (RDS) patients, it could not be determined if this PaO2 response had a prognostic value. From this data, the clinician is provided with a guide to the expected PaO2 response when a change in EEP is made.

Humans↗
PubMedDate not supplied

A closed system device for diagnosis and evaluation of neonatal pneumothoraces.

A closed system device with teflon needle, sideholes, and attached stopcock was designed and evaluated for diagnosis and evacuation of neonatal pneumothoraces. Experience with this device has demonstrated specific advantages over existing needles and techniques. Since the system is airtight, diagnosis of pneumothorax can be performed without the risk of introducing air. In addition, the needle sideholes provide more complete and efficient evacuation of air and fluids from the pleural cavity.

Humans↗
PubMedDate not supplied

On-line techniques for perfluorochemical vapor sampling and measurement.

The authors developed a compact gas sampling and perfluorochemical (PFC) measuring system for use in total and partial liquid ventilation systems, based on a precision two-thermistor thermal detector (TD). They describe the sensitivity and linearity of their on-line method for PFC analysis of expired gases and show how it may be used in partial liquid ventilation studies for determining PFC saturation and loss. Gas is sampled for a short time from a breathing circuit through a heated tube at a selectable point in the breathing cycle. Inspiration is sensed by a pressure transducer. The sample of gas is pulled into the heated (48 degrees C) thermistor chamber by suction and held there while the cooling effect of the vapor changes the thermistor temperature. Dry air in another chamber affects a second thermistor, and the difference of these responses is amplified. The raw signal is corrected for the effects of varying O2 levels by a fuel cell. This signal is sampled and held and displayed on a front panel display. Calibration is performed in percentage saturation at 37 degrees C using the PFC in use at that temperature, or another standard such as O2. In-vitro testing showed a linear response in the thermal detector device (R2 = 0.99) over the range of vapor pressures tested (0-14) mmHg) and was reproducible to within 3%. When electronically corrected for changes in O2 concentration, there was less than a 2% change in PFC saturation. The TD responses to CO2 (R2 = 0.99) and water vapor (R2 = 1.0) were linear and approximately equal and opposite over the normal operating ranges of expired gases. In-vivo results in rabbits showed a significant (R2 = 0.73; p < 0.01) correlation between the auto-sampler and manual collection modes for determination of PFC in expired gas.

Animals↗