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Biomedical subjects

D J Hatch

Publications and source records attributed to D J Hatch.

At least 91 records · Page 5Linked to original sources
PubMed1984

Percutaneous arterial cannulation in children. Concurrent and subsequent adequacy of blood flow at the wrist.

For percutaneous arterial monitoring in children, the Medicut (polypropylene) is an appropriate choice of cannula. Morbidity associated with its use is low. We studied blood flow and clinical signs relating to 70 arterial cannulations in 62 patients. In the few patients exhibiting flow disturbances either whilst the cannula was in situ or following decannulation, we observed no associated clinical signs of vascular insufficiency of the forearm, wrist or digits. Also, most patients showed normal, antegrade blood flow past the cannula in situ and following decannulation. Eight patients showed retrograde flow which, in six cases, spontaneously reverted to normal whilst the child was still in hospital. The results of this study increased our confidence in the appropriateness, safety and ease of use of these polypropylene cannulae in children where peripheral arterial vessel diameters are small.

Adolescent↗
PubMed1984

Metabolic correlates in infants and children during anaesthesia and surgery.

In 58 infants and children with body weights between 2.8 and 20.5 kg carbon dioxide production (VCO2 ml min-1) was measured during halothane anaesthesia for minor surgical procedures. In 22 cases measurements were made during both spontaneous and controlled ventilation during the same operation. A non-rebreathing circuit was used. Expired ventilation volume was measured with a dry gas meter and expired gas collected during 3-5 min in a Douglas bag. The carbon dioxide fraction of exhaled gas was determined with a sampling Gould capnograph. A respiratory quotient (RQ) of 0.8 was used to calculate oxygen consumption (VO2 ml min-1). During spontaneous breathing, regression analysis of the relationship between VCO2 and kg and between VO2 and kg showed high intercepts while corresponding relations to kg3/4 revealed an almost direct proportionality. Thus, VCO2 and VO2 ought to be related to body weight in kg3/4 in spontaneously breathing children. The mean value (+/- 1 s.d.) for VCO2 was 11.4 +/- 3.1 ml kg-3/4 and for VO2 14.2 +/- 3.9 ml kg-3/4. During controlled ventilation, the relationship between kg b.w. showed for VCO2 as well as for VO2 an almost direct proportionality with a mean value (+/- 1 s.d.) for VCO2 of 6.3 +/- 1.6 ml min-1 kg-1 and for VO2 of 7.8 +/- 2.0 ml min-1 kg-1. Prediction of VO2 for infants and children of this size could be based upon 14 X kg3/4 during halothane anaesthesia and surgery.

Anesthesia, Inhalation↗
PubMed1984

Accuracy of prediction of fresh gas flow requirements during spontaneous breathing with the T-piece.

In 40 spontaneously breathing children (7.3-47.9 kg) anaesthetized with halothane for minor surgical procedures the fresh gas flow (FGF) at onset of rebreathing (FGFr) was determined and end-tidal CO2 concentration (ETCO2), minute ventilation (VE), tidal volume (VT) and respiratory rates (f) were registered. The accuracy of predicting the FGFr from 2 X VE, 3 X VE and from two formulae (FGF = 15 X kg X f and FGF = 3 X (1000 + 100 X kg) was evaluated. FGFr ranged from 3.5 to 10 l min-1. FGF calculated from 2 X VE was inadequate. Calculations of FGF from 3 X VE and with the two formulae gave an adequate FGF in more than 80% of the children. No serious under-estimations were found. In a few cases FGF level was overestimated by more than 150%. It is suggested that when the theoretical calculation of FGF results in flow rates well over 10 l min-1 an upper flow rate limit of 10 l min-1 may be used in children weighing less than 30 kg since no child required a FGF over this rate.

Anesthesia, Inhalation↗
PubMed1982

Resistance to airflow through bedding materials used in infancy.

Various bedding materials used in infancy, including duvets (or continental quilts), were tested for airflow using the British Standards Institution tests for pillows or fabrics. Resistance was also measured when the items were placed on a dummy infant face. Measurements were made on washed and unwashed garments, which were tested both dry and wet. Results suggest that all the bedding materials tested are safe for use even in the newborn period. The duvets produced slightly lower resistance to breathing than conventional blankets and sheets. In view of the wide variety of infant bedding fabrics it seems desirable for standard airflow performance requirements to be introduced.

Bedding and Linens↗
PubMed1982

Critical assessment of jacket plethysmographs for use in young children.

In infants and very young children changes in thoracic gas volume (Vtg) during tidal breathing and during intermittent positive-pressure lung inflations have been estimated from pressure changes within double-layered rubber jackets covering the thorax and abdomen. In vitro and in vivo assessments demonstrated the linearity of these jackets over the range of volume changes found in these young subjects during respiratory function tests, and the small intrajacket background pressure (2.5 cmH2O) had minimal effects on resting lung volume and lung mechanics. These jackets can be used to monitor tidal volume in quiet subjects, and if an intermittent positive-pressure inflation technique is used static compliance can be accurately measured. The hysteresis of natural rubber and the direct contact of the recording system with the subject renders it unsuitable for the measurement of lung mechanics during tidal breathing and for the estimation of Vtg during airway occlusions.

Child, Preschool↗
PubMed1982

Lung volume and lung mechanics in infancy lateral or supine posture?

In 23 infants and young children aged from 3 wk to 2 1/2 years, lung volume, by plethysmography, dynamic lung compliance and total pulmonary resistance with air-filled balloons and pneumotachography, have been measured in the supine and right lateral postures in order to observe any possible systematic differences in either body position. Fourteen subjects were studied under light sedation, the remaining nine under general anaesthesia before elective surgery. In the sedated group, no significant differences were found between the two positions for lung mechanics. In the anaesthetised group the only measurement that varied with position was dynamic lung compliance, being lower in the supine posture (P less than 0.05). In one of the sedated infants with predominantly left sided lung disease, large position dependent changes in lung volume and lung mechanics were observed suggesting that care should be taken in interpreting lung function tests in infants with unilateral lung disease. In the anaesthetised subjects, the finding of reduced ratios of esophageal to mouth pressure change during brief airway occlusions, suggests that under these conditions pleural pressure changes were unequally distributed.

Adult↗
PubMed1980

Ventilatory management of neonates undergoing surgery. A review of the first 3 years' experience in a neonatal surgical intensive care unit.

The results of the ventilatory management of babies, obtained in the first 3 years of a neonatal surgical intensive care unit, are assessed. Overall mortality figures and detailed examination of the cause of death in individual diagnostic groups support a selective approach to intermittent positive pressure ventilation (IPPV) based mainly on clinical criteria. The adoption of a policy of prophylactic IPPV after operation would achieve virtually no improvement in mortality.

Abdomen↗
PubMed1980

An anaesthetic scavenging system for paediatric and adult use.

A scavening dish is described which removes large volumes of contaminated air. It can be placed close to the open-tailed bag of the paediatric T piece to provide a safe, convenient and efficient scavenger without any modification of the patient circuit. Measurements before and after installation have shown it to be capable of reducing nitrous oxide levels in the operating theatre to between 40 and 0 parts per million. The dish has been incoporated into a scavening system which can also be used with a standard antipollution valve or ventilator exhaust port.

Adult↗
PubMed1980

Improved esophageal balloon technique for use in infants.

Esophageal balloons of three different wall thicknesses, two different lengths, and two different diameters were made to assess which type of balloon gave the most consistent and reliable measurements of dynamic compliance (CL) and pulmonary resistance (Rp). The balloons were subjected to in vitro testing to determine their pressure-volume characteristics and working range and then used in infants to compare in vivo results from one balloon to another. The optimal balloon was found to have a length of 35--50 mm, a diameter of 7.6 mm, and a wall thickness of 0.045--0.075 mm. The use of unsuitable balloons or inappropriate volumes of air within the balloon resulted in applied pressures being under-recorded, both in vitro and in vivo, with consequent overestimation of CL and underestimation of Rp during infant lung function tests. Recommendations are made concerning the techniques of making and using esophageal balloons.

Esophagus↗
PubMed1978

Tracheal tubes and connectors used in neonates--dimensions and resistance to breathing.

The dimensions of tracheal tubes and connectors in common use were measured together with the resistance to breathing at flow rates occurring in babies breathing quietly. The outside diameters of rubber tubes varied more than those of plastic tubes. The main factors influencing resistance were the internal diameter and a sudden change in diameter or direction of flow. These are of particular importance in tubes of 2.5 mm i.d. and less and may cause an increase in the work of breathing during spontaneous ventilation. The resistance of small Cole pattern tubes was greater than that of plain tubes of similar o.d.

Humans↗
PubMed1977

The effects of prolonged naso-endotracheal intubation in children. A study in infants and young children after cardiopulmonary bypass.

The results of 458 prolonged nasotracheal intubations are described in 435 infants and young children up to 5 years of age after open heart surgery, in whom the upper airway was normal. No deaths occurred which could be attributed to the technique, and no tubes became obstructed. Sub-glottic stenosis did not occur when a loose-fitting endotracheal tube was used, and stridor after extubation was rare. If necessary, the technique can be used with safety for several weeks.

Airway Obstruction↗
PubMed1976

The effect of positive end expiratory pressure on lung mechanics and arterial oxygenation after open heart surgery in young children.

The effect of positive end expiratory pressure (PEEP) during mechanical ventilation of the lungs was measured in 10 young children, aged 3 weeks to 30 months, who were being ventilated artificially after cardiopulmonary bypass surgery. Changes in the end-tidal lung volume were measured directly using a jacket plethysmograph, and were assumed to indicate change in functional residual capacity (FRC). Simultaneous changes in compliance and blood-gases were measured also. FRC was increased in all subjects, and in most this increase was accompanied by an increase in arterial oxygenation. There was no significant alteration in the mean values of dynamic or static compliance in the group, although dynamic compliance increased during PEEP in six patients. PEEP may be of value after cardiopulmonary bypass in young children when oxygenation is poor despite high inspired oxygen fractions. The possible mechanisms by which it increases PaO2 are discussed.

Cardiopulmonary Bypass↗
PubMed1976

Thoracic gas volume in early childhood.

A total body plethysmograph is descirbed which was used to study thoracic gas volume (TGV) in infants and young children from birth to 2 1/2 years, and was suitable for use even in very sick babies. Normal TGV values were obtained in 42 studies of 35 healthy infants and young children, and 16 children with abnormal lung volume are described. TGV correlated well with length, weight, chest circumference, and age in the healthy infants. A low TGV was found in children with respiratory difficulties after cardiac and thoracic surgery, in respiratory distress syndrome of the newborn, and in association with pulmonary infection and chest cage abnormalities. Abnormally high TGV was most frequently seen in infants with small airways disease.

Asthma↗
PubMed1975

Change in end-tidal position in children after suxamethonium.

The change in end-tidal position (ETP) after suxamethonium-induced paralysis was measured in 15 children during routine general anaesthesia. In all patients the onset of muscle paralysis was associated with an increase in lung volume from ETP. This increase may be the result of paralysis of the expiratory muscles which are active during anaesthesia.

Age Factors↗