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A 37 year old patient with chronic active hepatitis progressing to cirrhosis presented with increasing breathlessness and was found to be hypoxic with finger clubbing. A progressive exercise study with measurement of oxygen saturation (Sao2) showed abnormally high ventilation and desaturation to 81% at 100 W. Serial studies over nearly two years showed, first, deterioration, then improvement with lower ventilation and higher saturation levels at all work loads. This could not be correlated with any change in treatment with azathioprine, prednisolone, or propranolol. (Thorax 1994;49:725-727) About one third of patients with hepatic cirrhosis are found to have arterial hypoxaemia without any of the usual cardiorespiratory causes. A few have obvious cyanosis with clubbing. The hypoxia is due either to right to left shunts through large arteriovenous connections within the lungs, or to peripheral vasodilatation of the fine branches of the pulmonary artery at both precapillary and capillary levels'2 leading to incomplete diffusion equilibration between alveolar and end capillary blood. The pathophysiology has recently been fully reviewed. ' Case report The patient presented at the age of 27 with nose bleeds, jaundice, anaemia, and swelling of legs and abdomen. Chronic active hepatitis was diagnosed by liver biopsy and, over subsequent years, further biopsies showed progression to cirrhosis despite treatment with prednisolone and azathioprine which had been prescribed for about five years, in varying dosage, before the present study. The cause of the chronic active hepatitis was never established. An autoantibody screen, including antibodies to smooth muscle and mitochondria, was negative. Hepatitis B serology was negative, and hepatitis C serology was not available at that time. The concentration of plasma ac-antitrypsin was not directly measured, but the level of a1-globulin was increased.Ten years after his first attendance he complained of breathlessness and was referred for respiratory assessment. He was clubbed but not cyanosed at rest. He said he was unusually short of breath on exertion, but there was no serious limit to his exercise tolerance and throughout the period of the study he worked full time as a welder on a British Rail track gang, and could play 36 holes of golf in a day without discomfort. During the period of study standard liver function tests were abnormal, and varied without any systematic trend with ranges as follows: bilirubin 55-90,mol/l, albumin 30-32 g/l, alkaline phosphatase 191-344 IU/1, gamma-GT 93-134 IU/1, and alanine transaminase 28-87 IU/l. He continued to drink alcohol, but it was difficult to assess in what quantity.Blood gas measurements were obtained sitting (Pao2 9-2 kPa, Paco2 4.3kPa) and lying (Pao2 9 3 kPa, Paco2 3-8 kPa). Pure oxygen wasgiven from a balloon reservoir with careful exclusion of leaks from the breathing circuit whereupon Pao2 rose to 60-6 kPa. A pulmonary perfusion scan with technetium-99 m labelled albumin microspheres, analysed according to th...

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Background -In normal subjects intravenous adenosine infusion has been shown to stimulate ventilation with a consequent fall in arterial partial pressure of carbon dioxide (Paco2), probably by an action on the carotid bodies.

SummaryThe at rest to 2.61 1 ( S E M 0.14) at -10 cmHzO dp < 0.05; n = 5) and 2.47 ( S E M 0.12) at -20 c.mH20 of mean chamber pressure. Vital capacity was unchanged by increasing extrathoracic pressure as M'US total lung cupacity . Key wordsEquipment; Hayek Oscillator, nomograms.With the introduction of the Hayek OscillatorTM (Flexco Medical Instruments AG, Zurich, Switzerland) ( Fig. 1) external high frequency oscillation (EHFO) is a practical option in ventilatory support. It has been used to improve gas exchange in adults with acute respiratory failure on the intensive therapy unit [l, 21, has been shown to increase pulmonary blood flow in children following cardiac surgery [3] and has even been used to ventilate anaesthetised and paralysed patients undergoing microlaryngeal surgery, as tracheal intubation was not necessary [4, 51.The Hayek Oscillator can operate around a negative pressure baseline. Previous attempts at EHFO with compression alone have resulted in a gradual reduction in functional residual capacity [6] and lung collapse [7]; they relied upon the elastic recoil of the chest wall to restore normal lung volumes. By operating around a negative baseline there is more control over end expiratory lung volume and the reduction in functional residual capacity can be minimised.The mean pressure within the cuirass is termed mean chamber pressure. A positive end expiratory pressure of + 5 cmHIO will compress the chest and a negative inspiratory pressure of -5 cmHzO will expand it, resulting in an overall mean chamber pressure of OcmH20. The pressure difference between end expiratory (+ 5 cmH,O) and end inspiratory chamber pressure ( -5 cmHzO) is termed, the span. Changes in these two variables together with variations in frequency have been shown to alter minute and tidal volume in an animal model [8]. However, the effect of these changes has not been characterised in humans. We report the frequencyltidal volume and frequency/minute