Biomedical subjects

T E Healy

Publications and source records attributed to T E Healy.

At least 19 recordsLinked to original sources

PubMed1995

Pulmonary function and head lift during spontaneous recovery from pipecuronium neuromuscular block.

We have studied in seven healthy conscious volunteers the correlation between the electromyographic (EMG) and clinical criteria used to identify adequate recovery from sub-paralysing doses of pipecuronium. Pipecuronium (mean dose 1.88 (range 0.92-3.16) mg) was administered to reach a T4/T1 ratio of 0.5; full recovery to 1.0 was produced in a mean time of 25.3 (14-39) min. During recovery from neuromuscular block, we measured tidal volume, forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1) negative inspiratory pressure (NIP), peak expiratory flow rate (PEFR), mid-expiratory flow rate (MEFR) and 5-s head lift. The assessments were started when the train-of-four (TOF) ratio reached 0.5 +/- 0.001 and repeated at each 0.1 +/- 0.001 increase up to a ratio of 1.0. All volunteers showed ptosis and diplopia after the first dose and difficulty in swallowing with subsequent doses. They also experienced a pleasant, relaxing sedative sensation. All could sustain head lift for 5 s at a TOF ratio of 0.5 and higher, except for one subject who could not lift his head only at a ratio of 0.5. There was a statistically significant decrease in FVC, FEV1 and PEFR with a nonsignificant decrease in other pulmonary measurements, except for NIP which only decreased significantly at a ratio of 0.5. These changes are probably of no clinical importance. All the measured respiratory variables returned to control values at a TOF ratio of 0.9.

Adult↗

PubMed1994

Respiratory sinus arrhythmia: comparison with EEG indices during isoflurane anaesthesia at 0.65 and 1.2 MAC.

Respiratory sinus arrhythmia (RSA) is a cyclical variation in heart rate during breathing, where the heart rate increases during inspiration and decreases during expiration. RSA and the electroencephalogram (EEG) were monitored in 10 patients undergoing elective surgery with isoflurane and nitrous oxide in oxygen anaesthesia after induction with propofol. All patients were subject to controlled ventilation and recovery from competitive neuromuscular block was facilitated by neostigmine and glycopyrronium (seven patients) or atropine (three patients). Median and spectral edge (95%) frequencies of the raw EEG were derived off-line. RSA and EEG indices were obtained during preinduction (baseline), induction, incision, 0.65 and 1.2 MAC of isoflurane maintenance during surgery and recovery. Significant decreases in the level of RSA, median and spectral edge frequencies were observed during induction and significant increases in all indices were observed at recovery in all patients. Significant decreases in the median and spectral edge EEG frequencies occurred in patients treated with atropine both to counteract bradycardia after propofol induction and at antagonism of neuromuscular block (n = 3), compared with patients treated with glycopyrronium (n = 7). In contrast, the level of RSA did not decrease significantly with atropine. It is concluded that measurements of RSA could form the basis of a useful index of anaesthetic depth during isoflurane anaesthesia, even during the use of pharmacologically appropriate doses of atropine. However, any effects of atropine on the raw EEG and on indices derived from the EEG, should be characterized further so that these effects are not confused with changes in anaesthetic depth.

Adult↗

PubMed1994

Efficiency of the Carden "Ventmasta" in A and D modes during controlled ventilation in children.

We have determined the efficiencies of the enclosed Mapleson A and Mapleson D modes of the Carden "Ventmasta" ventilator during controlled ventilation in 19 anaesthetized children. In addition, we determined the suitability for the A mode of the fresh gas formula, VF = 0.6 x weight0.5. Efficiency was assessed in terms of the fraction of fresh gas delivered to the alveoli. When the minute volume to fresh gas flow ratio exceeded 1.5, fractional delivery of fresh gas was 23% greater in the A mode than in the D mode (0.74 vs 0.60) (P < 0.0001). Under the same conditions, mean end-tidal carbon dioxide concentration in 27 children undergoing ventilation in the A mode with VF = 0.6 x weight0.5 was 4.6% (range 3.5-5.4%). We conclude that the Carden system is up to 23% more efficient in the A mode than in the D mode, and that under the conditions of this study, normocapnia or mild hypocapnia was produced accurately using the formula VF = 0.6 x weight0.5.

Adolescent↗

PubMed1994

Determination of the onset of rebreathing in an enclosed afferent reservoir breathing system in anaesthetized, spontaneously breathing adults: a comparison of three methods.

We used three methods to determine the onset of rebreathing in the Ohmeda enclosed afferent reservoir breathing system and compared the results with the previously published rebreathing characteristics of this system. Of the methods studied, expiratory limb capnography proved unsuitable for determining the onset of rebreathing in this system. Inspiratory limb capnography and minimum inspired carbon dioxide at the mouth did enable the onset of rebreathing to be determined. However the fresh gas flow:minute volume ratio at which rebreathing occurred as determined by these criteria was less than that determined by the Kain and Nunn criteria and thus offer no clinical advantage over the latter.

Adult↗

PubMed1993

Measurement of breath-by-breath gas exchange during general anaesthesia.

We describe a single flow transducer breath-by-breath gas exchange measurement system suitable for use during general anaesthesia. The system uses a Fleisch No. 2 pneumotachograph, a mass spectrometer and a microcomputer to give real-time continuous measurements. Correction for apparent gas exchange attributable to changes in gas stored in the lung (functional residual capacity) is available. The correction assumes no gas exchange of either nitrogen or argon for air-breathing subjects or argon only during anaesthesia, while the inspired concentrations are maintained at atmospheric values. The method has been tested against Douglas bag measurement and compared with results from conventional systems used by other authors. The system measurements show broad agreement with Douglas bag measurements, although the limits of agreement are wide for air-breathing volunteers. The system between-breath variation was typical of breath-by-breath methods in other areas of medical research.

Anesthesia, General↗

PubMed1993

Respiratory sinus arrhythmia: an index of light anaesthesia.

This study was designed to test if changes in the degree of respiratory sinus arrhythmia (RSA) can be used as an index of light anaesthesia. An on-line, real-time data logging system was used to record simultaneously the EEG and ECG waveforms from 10 patients undergoing routine surgery using i.v. propofol (Diprivan) anaesthesia. The degree of RSA was determined in real-time. The median frequency of the EEG was derived off-line and correlated with the degree of RSA. Time series analysis was performed on the derived indices off-line. Significant changes in the degree of RSA occurred in response to changes in propofol infusion in all patients; these changes corresponded also to changes in the median frequency of the EEG. Heart rate and ventilatory frequency are measured routinely during surgery and it is suggested that on-line monitoring of RSA, derived from these standard signals, provides a more convenient and objective index of lightening anaesthesia than either EEG analysis or classical estimates of anaesthetic depth based on arterial pressure or heart rate.

Adult↗

PubMed1993

Extending a pipecuronium neuromuscular block. Increments of atracurium or vecuronium as an alternative to pipecuronium.

Ten patients received increasing doses of pipecuronium at induction of anaesthesia. A dose response relationship was then constructed from which ED90 and ED95 values were measured as 43.4 micrograms.kg-1 and 50.5 micrograms.kg-1 respectively. A further 30 patients received pipecuronium in a dose sufficient to produce greater than 90% neuromuscular block. When the first contraction of the train-of-four had returned to 10% of control, a small increment of atracurium (1.1 mg), vercuronium (0.25 mg) or pipecuronium (0.21 mg) was administered, and this was repeated subsequently using the same criterion of recovery on each occasion. The duration and intensity of the block with pipecuronium increments remained constant. The duration of the block following atracurium or vecuronium was progressively less with subsequent increments until steady state was reached. The final mean durations at steady state were pipecuronium 7.37 min, atracurium 6.99 min, and vecuronium 5.15 min.

Adolescent↗

PubMed1992

Fresh gas requirements of an enclosed afferent reservoir breathing system during controlled ventilation in children.

An enclosed afferent reservoir breathing system (EAR) designed by Ohmeda was evaluated during anaesthesia with controlled ventilation in 104 healthy children. Carbon dioxide production and arterial carbon dioxide tension were measured in 12 children in order to determine the proportion of fresh gas (VF) involved in gas exchange. When the ratio of minute volume ventilation to fresh gas flow (VE:VF) exceeded 1.5, fractional utilization of fresh gas with the EAR was 0.92. This value and values of carbon dioxide production obtained from 43 children were used to derive a simple formula relating fresh gas flow requirements to body weight. The formula, VF = 0.6 x weight 0.5, was assessed in 49 children weighing 10-70 kg. The mean end-tidal partial pressure of carbon dioxide in these patients was 4.5 kPa (range 3.8-5.2 kPa). We conclude that the EAR has an efficiency of 92% in the use of fresh gas during controlled ventilation in healthy children, provided the VE:VF ratio is greater than 1.5. Under these conditions, normocapnia to mild hypocapnia was produced accurately using the formula VF = 0.6 x weight 0.5.

Adolescent↗

PubMed1992

Fresh gas requirements of an enclosed afferent reservoir breathing system in anaesthetized, spontaneously ventilating children.

We have determined the minimum fresh gas flow rate (VF) for use with the Ohmeda enclosed afferent reservoir breathing system (EAR) in 10 anaesthetized children breathing spontaneously. First, we determined the VF required to prevent rebreathing as detected by increased total ventilation (VE) and end-tidal carbon dioxide partial pressure. Second, we used a mathematical model to calculate the degree of rebreathing occurring at each VF. A VF equal to the predicted alveolar ventilation was sufficient to prevent clinically detectable rebreathing in all patients. From the model, no rebreathing occurred when VF/VE was 0.78 or more. We have shown previously that the EAR functions efficiently during controlled ventilation with a VF = 0.6 x weight 0.5. As this VF is slightly greater than the predicted alveolar ventilation, we suggest that the EAR may be used with a VF = 0.6 x weight 0.5 regardless of the mode of ventilation.

Adolescent↗

PubMed1992

Effect of physiotherapy on the auditory evoked response of paralysed, sedated patients in the intensive care unit.

Auditory evoked response (AER) was recorded before, during and after physiotherapy in 11 paralysed (atracurium 0.56 (SD) 0.13 mg kg-1 h-1), sedated (propofol 2.2 (1.0) mg kg-1 h-1; fentanyl 4.4 (2.3) micrograms kg-1 h-1) and critically ill patients undergoing ventilation in the intensive care unit (ICU). The latency of the negative wave, NB, was reduced by physiotherapy (mean 44.8 (SD) 7.9 ms before, 41.0 (6.8) ms during (P less than 0.01, non-parametric Friedman test) and 45.6 (6.3) ms after physiotherapy); NB amplitude showed no consistent change (-0.81 (1.4) microV, -0.81 (1.5) microV and -0.71 (1.3) microV, respectively). NB latency responded to patient arousal at constant levels of sedation and this requires further evaluation as a means of monitoring sedation in paralysed patients in the ICU.

Adult↗

PubMed1992

Physical characteristics of an enclosed afferent reservoir breathing system.

We have assessed the characteristics of the Ohmeda Enclosed Afferent Reservoir Breathing System (EAR) using simulated spontaneous ventilation and controlled ventilation. The additional work of breathing through the system was measured and shown to be comparable to that of a modified Mapleson D breathing system (Bain) for fresh gas flows producing similar end-tidal carbon dioxide concentrations. It was shown under conditions of simulated controlled ventilation that end-tidal gas concentration was relatively insensitive to variations in inspired to expired ratio (I: E), tidal volume (VT) and deadspace (VD). Measurement of the volume of carbon dioxide rebreathed using simulated spontaneous ventilation led to the prediction that rebreathing of carbon dioxide would begin to occur in the EAR when fresh gas flow to total ventilation ratio (VF: VE) was approximately 0.87. However, comparison of the results of model lung tests and clinical data suggests that great caution should be taken in extrapolating such results into clinical advice.

Anesthesia, Closed-Circuit↗

PubMed1992

Fractional delivery of fresh gas: a new index of the efficiency of semi-closed breathing systems.

In earlier clinical studies, we have found a significant difference in the fractional utilization of fresh gas (FU) when using an enclosed afferent reservoir breathing system (EAR) for adult patients compared with children. This difference was explained by a large arterial to end-tidal carbon dioxide difference in the adults, reflecting a larger alveolar deadspace. In the present study, a new index of breathing system efficiency, fractional delivery of fresh gas (Fd) is proposed, which is independent of alveolar deadspace. In order to demonstrate this, values of Fd were calculated for the EAR during controlled ventilation of adults, children and a lung model. There were no significant differences between the groups. A maximum efficiency of 0.94 for the EAR was close to the theoretical limit of 1.0 predicted by the results at minute volume ventilation to fresh gas flow ratio (VE:VF) values greater than 2.0. For adult patients, the values of Fd were shown to be significantly greater than the values of FU at the same VE:VF ratio (Fd = 0.91, FU = 0.72 at VE:VF = 2.0 (P < 0.05)).

Adolescent↗

PubMed1992

The Mancunian way.

The authors have examined early records of the administration of ether anaesthesia in Manchester and the lives of several medical men involved in these events. Charles Strange, a dentist and chemist, in a letter to the Manchester Guardian published on 14 January 1847, described a self-administration of ether for dental extraction, but George Bowring, a surgeon, subsequently claimed the first anaesthetic administered by a doctor in Manchester. The merits of these claims are discussed in the light of the circumstances surrounding these events.

Anesthesia, Dental↗

PubMed1992

The additional work of breathing through Portex Polar 'Blue-Line' pre-formed paediatric tracheal tubes.

The work of breathing through north- and south-facing Portex Polar 'Blue-Line' paediatric tracheal tubes of sizes 3.0-7.0 mm ID has been measured using sinusoidal flow at equivalent ventilatory rates of 10-50 breaths min-1 with tidal volumes of 10-500 ml. North-facing tubes are designed to sit with the connection on the forehead after intubation, whilst south-facing ones are designed so that the connection sits on the chin of the patient. It was found that the total work of breathing through north-facing tubes is approximately 8% higher than the total work of breathing through south-facing tubes of the same size, irrespective of tidal volume or respiration rate. The total work of breathing was dependent on total tube length but independent of tube design. The endotracheal connectors themselves were found to contribute a significant proportion of the total work of breathing but there was no significant difference between the inspiratory and expiratory performance of the tubes.

Anesthesiology↗

PubMed1991

Efficiency of an enclosed afferent reservoir breathing system during controlled ventilation.

We describe an enclosed afferent reservoir (EAR) breathing system developed by Ohmeda and designed to operate efficiently in spontaneous and controlled ventilation. The efficiency of the system was evaluated by calculating the fractional utilization of fresh gas in 10 ASA I-III patients during anaesthesia with controlled ventilation. Maximum efficiency occurred when the minute ventilation to fresh gas flow ratio was greater than 1.5. Under these conditions, fractional utilization was relatively constant with a value of 0.73 (95% confidence interval 0.69-0.78). The minimum fresh gas flow for use during controlled ventilation was determined in another eight ASA I-III patients when the minute volume to fresh gas ratio was greater than 1.5. In view of an increased arterial to end-tidal carbon dioxide partial pressure difference in patients in the first part of the study (1.03 kPa), normocapnia was defined as an end-tidal carbon dioxide partial pressure of 4.3 kPa. Normocapnia was achieved with a mean fresh gas flow of 66 ml kg(-1) min(-1), while 70 ml kg(-1) min(-1) produced mild hypocapnia.

Aged↗

PubMed1990

Back pain following general anaesthesia and surgery: evaluation of risk factors and the effect of an inflatable lumbar support.

Factors that contribute to postoperative lumbar back pain and the effect of an inflatable lumbar support on the incidence of postoperative backache were examined. The study consisted of two parts, a pilot study in which mathematical models for appropriate support pressures were produced and the main study to assess the role of an inflatable lumbar support. The use of a support reduced the incidence of back pain on the first postoperative day from 46 to 21 per cent (P = 0.007). The patient's sex, height, weight, and the presence or absence of obesity were not found to be significant factors in the incidence of postoperative back pain. Previous back pain or arthritis in any joint tended to be associated with an increase in the severity and incidence of postoperative back pain. Postoperative back pain was more severe after procedures lasting more than 40 min. Early mobilization reduced the amount of back pain. In conclusion, patients benefit from the use of an inflatable lumbar support if they have previously suffered from backache or if they are to be anaesthetized for more than 40 min.

Adult↗

PubMed1990

The effect of diclofenac and nefopam on postoperative dental pain.

Eighty-two outpatients who received general anaesthesia for surgical removal of maxillary or mandibular third molars were given either diclofenac 75 mg or nefopam 20 mg intramuscularly for postoperative pain control. They and the control group were also allowed oral paracetamol as required. The results showed that there was no significant pain relief from these single intramuscular injections.

Adult↗

PubMed1989

Effect of oral doxapram on morphine-induced changes in the ventilatory response to carbon dioxide.

A double-blind crossover volunteer trial has been carried out to determine if oral doxapram reduces the respiratory depression caused by morphine 0.12 mg kg-1 i.m. Doxapram was given to the subjects 90 min before the morphine and significantly reduced the displacement of the ventilatory response to carbon dioxide caused by the morphine. This occurred despite the fact that the plasma concentrations of doxapram were significantly lower when the subject had been given morphine than when a placebo injection had been administered. Doxapram alone in doses of 300 mg and 600 mg did not alter significantly the respiratory variables measured in this study.

Administration, Oral↗