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Biomedical subjects

P Rolfe

Publications and source records attributed to P Rolfe.

At least 109 records · Page 6Linked to original sources
PubMed1982

The continuous measurement of milk intake at a feed in breast-fed babies.

A method for the continuous measurement of milk intake during a breast-feed is described. A miniature Doppler ultrasound flow transducer, located in the tip of a latex nipple shield, is interposed between mother and baby during feeding. Preliminary results indicate the scope and current limitations of the method in terms of both populations and individual mother/infant pairs. An initial analysis of individual feeds indicates that two factors may contribute to the curtailment of intake during a feed from one breast: a progressive reduction in intake volume per suck, and/or an increase in the proportion of time spent pausing between bursts of sucking.

Breast Feeding↗
PubMed1982

Skin surface PO2 and blood flow measurements over the ischial tuberosity.

The effect of externally applied load on skin blood flow was examined over the ischial tuberosity by using skin surface oxygen measurements, photoelectric plethysmography, and thermal clearance measurements. The load applied to each transducer in turn was increased every 10 minutes until blood flow was occluded. Cut-off pressures of 40 to 48kPa (300 to 360 mmHg) were recorded. Differences between the average pressure over the entire indenter and pressures at its center were investigated. A combined pressure and PO2 measuring device is presented.

Humans↗
PubMed1981

Skin surface PO2 measurement and the effect of externally applied pressure.

The effect of externally applied load on the partial pressure of oxygen in tissue, measured at the skin surface (PSO2) was examined by applying a load to a transcutaneous O2 monitor mounted on the skin of healthy subjects. The load was increased every 4 minutes, and the PSO2 was recorded at the end of the 4-minute period. Three sites were investigated: the sacrum, the greater trochanteric area, and the lateral aspect of the thigh. Mean initial values for the 3 sites were found to be 10.1, 11.1, and 10.1 kPa, respectively. On increasing the applied load, values were found to reduce gradually at first and then at an increasing rate to zero at the "cut-off" load. The mean cut-off pressure for the 3 areas was 15.2, 18.8, and 18.1 kPa.

Humans↗
PubMed1980

Continuous limb blood flow estimation in the newborn using electrical impedance plethysmography.

This study aims to define a method for acquiring limb flood flow data from newborn babies on a continuous basis which would be suitable for automatic processing. Pulsatile electrical impedance and strain gauge signals were analyzed in 3 different ways. The results were compared with estimates of flow derived from venous occlusion plethysmography with a mercury-in-rubber strain gauge. Measurements were made from 33 babies. The impedance technique was easier to perform than the strain gauge technique. The reproducibility of the various estimates of flow is shown in Table 3. The beat-to-beat reproducibility of simultaneous pulsatile mesurements and of repeated measurements on different subjects was greater from the impedance recordings than from the strain gauge recordings. The results of linear regression analyses between the different flow estimates are shown in Table 4. The best correlation with flow measured using venous occlusion plethysmography was with flow calculated from the impedance pulse height, F(Zmax) (r = 0.76; n = 30; P < 0.001). The regression line between these 2 variables was not statistically significantly different from the line of identity, (P < 0.98), and the intercept is close to zero. The measurement of the impedance pulse height, delta Zmax, and the subsequent calculation of F(Zmax) could be automated and provide continuous beat-to-beat blood flow estimations.

Extremities↗
PubMed1979

O2 and N2O analysis with a single intravascular catheter electrode. An in-vitro study.

The simultaneous measurement of O2 and N2O in liquid, using a single polarographic catheter electrode, is described. It is shown that commercial PO2 intravascular electrodes, with silver cathodes, produce separate and distinct polarograms for O2 and N2O, and that these electrodes can be used for the measurement of both PO2 and PN2O.

Blood Gas Analysis↗
PubMed1979

A Doppler ultrasound technique for measuring human milk flow.

The authors describe the development of a Doppler ultrasound flow transducer used in conjunction with a zero-crossing demodulator for breast milk flow measurement. The results of the preliminary evaluation in vitro are presented in the paper. The design is at present being minaturised in order to use the transducer for in vivo measurement.

Breast Feeding↗
PubMed1977

Effect of continuous positive airway pressure breathing on cardiorespiratory function in infants with respiratory distress syndrome.

A method of investigating the cardiorespiratory responses to continuous positive airway presslre (CPAP) in infants with respiratory distress syndrome is described. All measurements were made immediately before and within five minutes of application or any change in level of CPAP. Ventilation was derived from a pneumotachograph and dynamic compliance calculated. We have also measured arterial pH, oxygen and carbon dioxide tensions, arterial blood pressure and central venous pressure. Arterial oxygen tension increased in association with a decrease in the alveolar-arterial oxygen gradient. No consistent changes occurred in pH or carbon dioxide tension. Heart rate and mean arterial blood pressure remained the same but the arterial pulse pressure narrowed and the increase in central venous pressure averaged 17% of the applied airway pressure. There were less variations in both tidal volumes and instantaneous respiratory rates with CPAP compared with spontaneous breathing without CPAP. The respiratory rate decreased, but there were no consistent changes in tidal volume, resulting in a lesser reduction of minute ventilation. Dynamic compliance decreased on CPAP. With correct use of CPAP, and improvement in oxygenation generally occurs without obvious adverse cardiorespiratory effects. CPAP must nevertheless be used cautiously and in conjunction with close monitoring; because when the appropriate pressures are exceeded, it is possible that both circulatory and ventilatory function might be severely compromised.

Blood Pressure↗
PubMed1976

Effect of feeding on ventilation and respiratory mechanics in newborn infants.

Measurements of ventilation and respiratory mechanics were made before and after tube feeding in 24 infants. In 12 infants with the respiratory distresssyndrome tidal volume tended to fall after feeding; as the respiratory rate increased after feeding; as the respiratory rate increased after feeding, minute ventilation remained unchanged. Hypoventilation is therefore unlikely to be the cause of hypoxaemia after feeding. Compliance, resistance, and the work of breathing showed no changes after feeding. In 12 healthy infants feeding had no effects on pulmonary function. There was a slight rise in compliance and a tendency for work of breathing to fall after feeding. Respiratory rate, tidal volume, and minute ventilation remained unchanged. There was therefore no evidence of adverse effects of feeding on any of the factors measured. It is suggested that hypoxaemia without hypoventilation after feeding in infants with pre-existing respiratory distress syndrome might be attributable to a reduction in functional residual capacity associated with a greater extent of airways closure than before feeding.

Enteral Nutrition↗
PubMed1975

Air temperature recordings in infant incubators.

Air temperatures were continuously recorded inside four incubators with proportional heating control and six incubators with on/off heating cycles, during routine use. The air temperatures in the former were constant throughout, with a gradient between the roof and above-mattress air temperature not exceeding 1 degree C. In contrast, the recordings from the latter models showed a regular cyclical oscillation, the duration of the cycle varying from 14 to 44 minutes. Each incubator had a characteristic profile. The roof air temperature could vary by as much as 7-1 degrees C and the above-mattress air temperature by as much as 2-6 degrees C during the cycle. The oscillation persisted in the air temperatures recorded inside an open-ended hemicylindrical heat shield when used inside these incubators, but was markedly reduced inside a closed-ended heat shield, Carbon dioxide concentration did not increase significantly inside the latter.

Body Temperature↗
PubMed1975

Monitoring in newborn intensive care.

The major difference between adult and newborn intensive care is the importance in the latter of respiratory problems requiring extensive surveillance and support. Impaired gas exchange in the lung, together with disturbed breathing patterns, often including the temporary cessation of breathing (apnoea), are characteristic of respiratory distress in pre-term infants. New apnoea monitors continue to be introduced, and the recent development of means for the continuous measurement of arterial oxygen in the newborn, thus allowing dangerously high and low oxygen levels to be avoided, must represent a significant advance in both physiological measurement and neonatal intensive care.

Apnea↗