Congenital diaphragmatic hernia causing cardiac arrest in a 30-year-old woman.

Congenital diaphragmatic hernia (CDH) usually presents in infancy with respiratory failure requiring urgent surgical correction. Mortality in this group of patients remains poor and persistent pulmonary hypertension is a significant contributor. It is therefore rare for patients to reach adulthood undiagnosed. CDH is often identified incidentally in adults but when symptoms arise, they relate to the organ involved, and include gastrointestinal symptoms of dyspepsia and obstruction, as well as respiratory complaints such as dyspnoea. We present the case of a 30-year-old woman who was admitted with non-specific symptoms of upper abdominal discomfort but whose deteriorating condition culminated in a cardiac arrest, as an unreported presentation of CDH. The patient presented initially with severe left upper quadrant pain. Her chest x-ray on admission suggested a raised left hemidiaphragm. She went on to have computed tomography (CT) of the thorax and abdomen as well as oesophagogastroduodenoscopy, which raised the suspicion of diaphragmatic eventration. Repeat CT was performed after the patient collapsed on the ward five days following admission, revealing tracheal deviation, and a strangulated Bochdalek hernia containing stomach and spleen. After transfer to the anaesthetic room, she suffered a cardiac arrest. Advanced life support was required to return spontaneous cardiac function. She was intubated and ventilated, and a needle thoracostomy was performed to decompress the tension gastrothorax. Emergency laparotomy revealed a gangrenous stomach and spleen. Total gastrectomy with primary Roux-en-Y reconstruction, splenectomy and insertion of a feeding jejunostomy were performed. The patient recovered well postoperatively and was discharged two weeks following surgery.

A new method for measuring nitrogen and gases in blood.

The authors developed a new apparatus for extracting nitrogen or other inert gases from blood by flushing (sparging) the specimen with another gas. To investigate the utility of the new methodology, the apparatus was used in conjunction with a mass spectrometer to measure the blood N2 content of healthy normobaric, non-smoking, adult volunteers; the mean was found to be 11.7 microliters/ml +/- 0.9 microliter. This compares closely with values cited in the literature. The within-subject variation for repeat samples taken several weeks apart was significantly (P < 0.003) less than the variation between different subjects, suggesting that there may be true differences in N2 content between different individuals. These data must be considered preliminary, a larger study is needed to investigate population differences in detail. The advantages of the new method are discussed.

A new method for the measurement of gas solubility.

A novel technique for the measurement of gas solubility and gas content in liquids and suspensions is described. Saturation of the liquid and subsequent extraction of the test gas both took place in a specially modified gastight syringe. The test gas was extracted from the saturated liquid by bubbling an inert carrier gas through the liquid ("sparging"). All gas exiting the apparatus was directed toward a mass spectrometer that measured the volume of extracted test gas in the presence of the carrier. The technique was used to measure the solubilities of nitrogen, oxygen, carbon monoxide, carbon dioxide, and nitrous oxide in olive oil at 37 degrees C. The Bunsen solubility coefficients so obtained are in good agreement with those obtained by classic techniques.

Demonstration of a problem in estimating sensible heat loss from the respiratory tract by thermometry.

We have investigated sensible respiratory loss, which is usually taken as the product of expired volume and the temperature difference between inspired and expired air (VE X delta T). Air temperature was measured with a 0.122 mm copper-constantan thermocouple mounted in the mouthpiece of a T-piece breathing system, and expired volume with a pneumotachograph. Changing air temperature (delta T) at the mouth and expired air volume (VE) were recorded simultaneously while the subject voluntarily breathed at different tidal volumes and rates. Inspired temperatures were controlled at 12.05 degrees C, 21.80 degrees C and 25.74 degrees C at a low dewpoint temperature of 4-5 degrees C. Temperature volume "loops" were constructed using an x-y plotter. The areas of each "loop" and enclosing rectangle (VE X delta T) were measured. The difference was divided by the weight of the rectangle to give the percentage of overestimation of sensible heat loss, which ranged from 5.5 to 17.2 per cent. The error increased significantly with decreasing tidal volume and increasing respiratory rate.

Fluidic cycling devices for inspiratory and expiratory timing in automatic ventilators.

The theoretically desirable characteristics of fluidic timing devices for use in automatic ventilators are discussed. The principal limitation of most timers described is the separate control of inspiratory and expiratory time. It is more convenient to have one control for frequency and a separate control for I:E ratio. Two new circuits are described which allow this independent adjustment of frequency and I:E ratio.

The effect of naloxone and morphine on convulsions in mice following withdrawal from nitrous oxide.

The incidence of withdrawal convulsions was determined in mice following removal from a 70 per cent nitrous oxide environment. Groups of 20 mice received saline (control), naloxone or morphine subcutaneous injections five minutes prior to withdrawal. The observer was blind to the treatments. In comparison to the control group, the proportion convulsing was significantly (p less than 0.05) increased following naloxone 0.125 mg (n = 40), 0.25 mg, but not 0.5 mg. The proportion convulsing was significantly decreased following morphine 0.4 mg. Overall proportions of mice convulsing was 0.55 for the saline control group; 0.73 for naloxone 0.125 mg; 0.80 for naloxone 0.25 mg; 0.60 for naloxone 0.50 mg; and 0.38 for morphine 0.4 mg. Modification of this phenomenon by both an opiate antagonist and agonist suggests endorphin withdrawal as a possible mechanism. However, this should be regarded as indirect evidence pending further study of this area.

Althesin, ketamine and methohexitone at pressure--duration of action of a single i.v. dose.

General anaesthesia for emergency surgery in a pressurized habitat is likely to involve the use of i.v. agents. The anaesthetic property of such agents is known to be antagonized by pressure, but the effect on their duration of action is not easily predicted. The recovery of mice from a single i.v. dose of Althesin, ketamine or methohexitone was estimated by their ability to remain upright in a rotating drum. At 35 atm abs. duration of action was significantly reduced: P less than 0.05 for Althesin; P less than 0.01 for ketamine and methohexitone. A number of animals in each group, however, displayed recovery times that were comparable to control. The convulsion rate with methohexitone was 60% at 35 atm abs., whereas at 1 atm abs. it was 20%. The clinical implications of these findings are discussed.

A paediatric ventilator with a fluidic control system.

A paediatric ventilator has been designed basically as a fluidic-logic controlled T-piece occluder. Inspiratory and expiratory time, inflation pressure limit, positive end-expiratory pressure (PEEP), continuous positive airway pressure (CPAP) and inspiratory flow-rate are controlled independently and intermittent mandatory ventilation (IMV) is available. Warning systems are provided for failure of the driving as, low airway pressure and inspiratory pressure limit. The breathing circuit is isolated from the control and warning systems for ease of sterilization.

Behaviour of three resuscitators under hyperbaric conditions.

Three portable resuscitators were tested under hyperbaric conditions--the Pneupac Ventilator/Resuscitator, the Motivus Resuscitator (Type P.V.),and the Stephenson Minuteman Resuscitator. The first two delivered an inadequate tidal volume at 2 ATA. The third, while delivering a constant tidal volume, did so at an increasingly inadequate ventilatory frequency.

Intermittent mandatory ventilation with "Manley" ventilators.

A method is described whereby gas powered, minute volume divider, ventilators may be adapted to provide intermittent mandatory ventilation.

A fluidically controlled ventilator for bronchoscopy.

A simple time-cycled device uses an oscillating, fluidic, bistable element to control the high-pressure oxygen, supply to the ejector of a ventilating bronchoscope. Both manual and automatic modes of function are available, and inflation pressure and respiratory rate are controlled. Its construction is simple, the cost is low and the number of components is small.