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Biomedical subjects

S W Malin

Publications and source records attributed to S W Malin.

8 recordsLinked to original sources
PubMed1992

Cardiorespiratory effects of changing inspiratory to expiratory ratio during high-frequency oscillation in an animal model of respiratory failure.

To examine the effects of varying inspiratory/expiratory ratio (I/E) on cardiorespiratory function during high-frequency oscillation (HFO), 11 saline-lavaged rabbits were ventilated at I/E = 1:2, 1:1.5, 1.5:1, and 2:1 in a paired comparison to a baseline of I/E = 1:1. HFO was delivered by a SensorMedics model 3100 oscillator at a frequency of 10 Hz. Pressure amplitude and proximal mean airway pressure (PPaw) were held constant as I/E was varied from baseline to the experimental I/E. During each paired observation, PaO2, PaCO2, cardiac output, blood pressure, and distal mean airway pressure (DPaw) were measured. We found that as I/E was increased or decreased from 1:1, no significant changes in PaO2, PaCO2, blood pressure, or cardiac output occurred. We conclude that in this model, varying I/E has no significant effect on oxygenation, ventilation, or cardiovascular function.

Analysis of Variance↗
PubMed1992

Effects of dexamethasone on pulmonary function following extubation.

Dexamethasone is often given to intubated neonates to facilitate successful extubation. To study the effects of dexamethasone on pulmonary function immediately following extubation, we conducted a randomized, blinded, placebo-controlled trial in 51 infants. All infants had been intubated for a minimum of 3 days but no more than 30 days. Mean weight at extubation was 2.41 kg in treated infants, 2.25 kg in control infants. When infants were deemed ready for extubation, dexamethasone 0.5 mg/kg/dose or an equal volume of normal saline was given in three doses 8 hours apart. The final dose was given 1 hour before extubation. Esophageal pressure, air flow integrated to tidal volume (Vt), respiratory rate, and heart rate were measured before extubation, immediately following extubation, and every 20 minutes for 80 minutes. Total pulmonary resistance (RTP), dynamic lung compliance (CL), and minute ventilation (VE) were calculated. Forty-two infants completed the study; 19 infants received dexamethasone and 23 received placebo. There was no difference between the two groups in gestational age, weight at study, or length of intubation. Vt, RTP, VE, and CL were not significantly different between the two groups over time; however, RTP increased over time in the placebo group. Heart rate was significantly lower in the dexamethasone group. We conclude that dexamethasone appears to have limited effect on pulmonary function immediately following extubation in the population studied. Further studies should evaluate the drug effect beginning at least 1 hour after extubation.

Dexamethasone↗
PubMed1990

Capillary blood gases in the neonate. A reassessment and review of the literature.

Heel puncture capillary blood gas (CBG) measurements continue to be used in neonates for estimating arterial blood gas values. Review of the literature reveals general agreement that CBG PO2 values are of little use in predicting arterial PO2 and that CBG pH values are reliable predictors of arterial pH; opinion varies regarding CBG PCO2. We conducted a two-part study comparing postductal arterial and CBG values. First, 50 infants were studied, each only once. All infants had umbilical arterial catheters in place. Blood was obtained simultaneously from the umbilical artery catheter and the warmed heels. Results demonstrated poor predictability of arterial values from CBG pH and PCO2 as well as for PO2. Second, to determine if variation both within and among individuals was similar, repeated measurements were made in 27 additional infants comparable to the first group. We obtained 3 to 28 simultaneous postductal arterial and CBG samples from each infant. A random-effects nested analysis of variance indicated that for pH, variation was largely the result of between-subject or within-subject replicates effects, while for PO2 and PCO2, most variation was explained by differences between the two techniques (umbilical artery catheter vs CBG). The results indicate that CBG measurements do not accurately predict arterial values in neonates. Extreme caution should be used when management decisions are based on CBG values.

Blood Gas Analysis↗
PubMed1990

Measurement of tidal volume using a pneumotachometer during high-frequency oscillation.

To assess the accuracy of a pneumotachometer (PN) for tidal volume (VT) measurements during high-frequency oscillation (HFO), we determined simultaneously VT using a PN and a full body plethysmograph (PL) in 12 rabbits. HFO was delivered with an oscillator at a frequency of 10 Hz, mean airway pressure of 8 cm H2O, and inspiratory time of 50%. Pressure amplitude (delta P) was varied as follows: 40, 60, 80, 20, 100, 40 cm H2O. Finally, in ten rabbits a spacer equal in deadspace (VD) to that of the PN (15 ml) was left in-line for 5 min. Blood gases were obtained before and after the spacer was added. We found that VT-PN correlates well with VT-PL (r = .92), although the difference between VT-PN and VT-PL is greater at large VT. Significant respiratory acidosis developed with the spacer in-line. PN may be used to trend VT during HFO but PN must not be left in-line, as increased VD seriously affects ventilation.

Animals↗
PubMed1987

Abuses of oxygen.

Explore the source record for details and available documents.

Bronchopulmonary Dysplasia↗
PubMed1987

Optimal thermal management for low birth weight infants nursed under high-powered radiant warmers.

Servocontrol of skin temperature for the critically ill premature neonate nursed on a radiant warmer bed has been assumed to be analogous to skin temperature control for infants nursed in convection-warmed incubators. There are significant differences between these two warming techniques, and no definitive data exist to aid the clinical specialist in governing radiant warmer control. Eighteen low birth weight premature infants less than 2 weeks of age were studied under powerful overhead radiant warmers to determine the optimal skin temperature for servocontrol of radiant heater output. Anterior abdominal wall temperature was servocontrolled at 35.5 degrees, 36.5 degrees, and 37.5 degrees C in a randomized fashion for three periods of 90 minutes each after thermal equilibrium was established. Oxygen consumption was measured during the entire 90-min sample period at each temperature by a computerized metabolic apparatus to determine the optimal thermal neutral control temperature defined as minimal oxygen consumption with normal body temperature. Skin, deep rectal, and environmental temperature measurements, as well as behavior assessments, were made concurrently. Oxygen consumption was significantly elevated at 35.5 degrees C (8.62 +/- 0.73 mL/kg/min, mean +/- SEM) compared with 36.5 degrees C (7.30 +/- 0.55 mL/kg/min). Changing servocontrol temperature to 37.5 degrees C produced no further significant decrease in oxygen consumption (7.41 +/- 0.70 mL/kg/min), and nine infants manifested supranormal deep rectal temperatures (greater than 37.5 degrees C). Optimal abdominal skin temperature control at 36.5 degrees C (slightly warmer than previously reported but less than 37.5 degrees C) is recommended for premature neonates nursed on radiant warmer beds.(ABSTRACT TRUNCATED AT 250 WORDS)

Beds↗
PubMed1985

Nonsurgical management of obstructive aortic thrombosis complicated by renovascular hypertension in the neonate.

The use of umbilical artery catheters has become commonplace in the intensive care nursery and has facilitated management in the very ill newborn infant. Thrombotic complications associated with the use of such catheters may be as high as 30%. The successful, nonsurgical management of either complete or partial aortic thrombosis, associated with renovascular hypertension, is reported in three infants. Aggressive supportive medical management resulted in a satisfactory outcome in all three infants.

Aortic Valve Stenosis↗