Modelling lung and tissue diffusion using a membrane oxygenator circuit

A simple model lung has been designed using a membrane oxygenator circuit comprising two membrane oxygenators primed with one to two litres of equine blood, giving reproducible results over several hours. Normoxia and normocapnia were achieved consistently over the duration of the test with a blood flow of 2.5 l/min, oxygenator ventilation gas flow of 5 l/min air with 0.3 l/min O2 and deoxygenator ventilation gas flow of 5 l/min 5% CO2 in N2 with 0.2 l/min CO2. The measured PaO2 was 81.3 (SD 3.35 mmHg), PvO2 38.3 (SD 1.38 mmHg), PvCO2 60.6 (SD 1.13 mmHg) and PaCO2 36.1 (SD 0.69mmHg). MO2 and MCO2 were 116 ml/min and 169 ml/min, respectively. An increasing linear relationship was observed for FiO2 and the corresponding PaO2 and, similarly, with FiCO2 and PvCO2, providing reference ranges for this model.

Two cases of parotid gland infection with bacteraemia due to meticillin-resistant Staphylococcus aureus

Parotid gland infection as a source of meticillin-resistant Staphylococcus aureus bacteraemia has been rarely reported. It is predominantly a disease of the elderly and is associated with significant mortality. Two cases are described here that presented over a 6 month history at a district general hospital. Many cases may be preventable with adequate hydration and good oral hygiene, combined with effective infection control.

Steady-state measurement of NO and CO lung diffusing capacity on moderate exercise in men

Using a rapidly responding nitric oxide (NO) analyzer, we measured the steady-state NO diffusing capacity (DL(NO)) from end-tidal NO. The diffusing capacity of the alveolar capillary membrane and pulmonary capillary blood volume were calculated from the steady-state diffusing capacity for CO (measured simultaneously) and the specific transfer conductance of blood per milliliter for NO and for CO. Nine men were studied bicycling at an average O(2) consumption of 1.3 +/- 0.2 l/min (mean +/- SD). DL(NO) was 202.7 +/- 71.2 ml. min(-1). Torr(-1) and steady-state diffusing capacity for CO, calculated from end-tidal (assumed alveolar) CO(2), mixed expired CO(2), and mixed expired CO, was 46.9 +/- 12.8 ml. min(-1). Torr(-1). NO dead space = (VT x FE(NO) - VT x FA(NO))/(FI(NO) - FA(NO)) = 209 +/- 88 ml, where VT is tidal volume and FE(NO), FI(NO), and FA(NO) are mixed exhaled, inhaled, and alveolar NO concentrations, respectively. We used the Bohr equation to estimate CO(2) dead space from mixed exhaled and end-tidal (assumed alveolar) CO(2) = 430 +/- 136 ml. Predicted anatomic dead space = 199 +/- 22 ml. Membrane diffusing capacity was 333 and 166 ml. min(-1). Torr(-1) for NO and CO, respectively, and pulmonary capillary blood volume was 140 ml. Inhalation of repeated breaths of NO over 80 s did not alter DL(NO) at the concentrations used.

Collaboration, facilities and communities in day care services for older people

Collaborative working in care for older people is often seen as a desirable goal. However, there can be problems with this approach. This paper reports on a single blind randomized controlled trial which was carried out to compare outcomes of rehabilitation in two settings: a day hospital and social services day centres augmented by visiting therapists. The subjects were 105 older patients. Principal outcome measures were the Barthel Index, Philadelphia Geriatric Centre Morale Scale and the Caregiver Strain Index. Two aspects of the trial are examined here. Firstly, we investigated whether trial patients were more disabled than regular day centre attendees. Levels of health and well being amongst trial patients were compared with those of a random sample of 20 regular attendees from both of the participating day centres and an additional voluntary sector day centre. Secondly, key staff from the different settings were interviewed to assess how well the day centre model had worked in practice. Trial patients were significantly more disabled than regular day centre attendees according to the Barthel Index (P < 0.001), but this difference was no longer significant after three months of treatment. The day centre model had several problems, principally discharge policy, acceptability, facilities and attitudes of staff and regular attendees. Positive aspects of the day centre model, as well as successful rehabilitation, included shared skills, knowledge and resources. This paper suggests that collaborative working in day centres requires multipurpose facilities. If health staff maintain a permanent presence, benefits can include improved joint working, easier access to health care and the use of rehabilitative therapy as a preventative strategy. Day care settings can be analyzed as representing different types of communities. Allowing older users a greater degree of choice in facilities may increase the acceptability of care.

The Huntingdon Day Hospital Trial: secondary outcome measures

OBJECTIVE

To compare day hospital to day centre rehabilitation using scales to measure mobility, activities of daily living and quality of life.

DESIGN

Single blind randomized controlled trial with home assessments at baseline (twice), six weeks and three months.

SETTING

Mainly rural health district. Day hospital and social services day centres in market towns.

INTERVENTIONS

Day hospital treatment or day centre rehabilitation by a physiotherapist and two health support workers.

MAIN OUTCOME MEASURES

World Health Organization mobility scale scored with and without aid, Nottingham Extended Activities of Daily Living Scale and Nottingham Health Profile.

SUBJECTS

One hundred and five physically disabled older patients living at home referred for day hospital rehabilitation or maintenance before discharge from hospital (66) or referred as outpatients (39).

RESULTS

At three months there were no statistically significant differences between rehabilitation at day hospital and day centre for any of the outcome measurements. However, there were significant improvements between baseline and three months for the following subscales [mean change per six-week period (95% confidence interval) ]: WHO mobility subscale (with aid) -0.67 (-0.99,-0.35); Nottingham Health Profile mobility subscale -10 (-15.5,-4.5) Nottingham extended ADL mobility subscale +3.08 (1.78,4.37); Nottingham extended ADL leisure subscale +1.66 (0.96,2.36).

CONCLUSION

There were no differences between day hospital and day centre in the outcomes measured. Day rehabilitation appeared to improve functional ability and mobility and scales reflecting these domains deserve further evaluation as outcome measures in this patient group. However, no improvement in quality of life was observed.

A randomized controlled trial of day hospital and day centre therapy

OBJECTIVE

To compare the outcome of day hospital to day centre rehabilitation.

DESIGN

Single blind randomized controlled trial with home assessments at baseline (twice), six weeks and three months.

SETTING

Mainly rural health district. Day hospital and social services day centres in market towns.

SUBJECTS

One hundred and five physically disabled older patients living at home referred for day hospital rehabilitation or maintenance before discharge from hospital (66) or referred as outpatients (39).

INTERVENTIONS

Day hospital treatment or day centre rehabilitation by a physiotherapist and two health support workers.

MAIN OUTCOME MEASURES

Barthel Index, Philadelphia Geriatric Morale Scale and Caregiver Strain Index.

RESULTS

More day centre (23/55) than day hospital patients (6/50) (p <0.001) withdrew from allocated treatment by choice or because of operational difficulties. Both groups improved significantly in functional ability and reduction of care-giver strain by three months but there was no significant difference between groups. The mean improvement in Barthel Index (standard error) for day hospital = +1.5 (0.41) (n = 34) and day centres = +1.5 (0.48) (n = 38). The mean difference (95% confidence interval) between day hospital and day centre was 0 (-1.28, +1.28). Likewise the mean Philadelphia Geriatric Morale Scale improvement for day hospital +1.8 (0.66) (n = 35) and day centres was +0.9 (0.63) (n = 38). The mean difference was -0.88 (-2.7, +0.95). The mean reduction in Caregiver Strain for day hospital was -1.45 (0.5) (n = 23) and day centre was -1.59 (0.47) (n = 27). The difference was -0.14 (1.52, +1.24). (These analyses are all on an intention-to-treat basis.)

CONCLUSION

Whilst the improvement in functional ability and care-giver strain was similar in both groups, day centre rehabilitation was less popular and had practical difficulties. If these difficulties can be overcome the model should be tested elsewhere.

Delayed cyanide poisoning following acetonitrile ingestion

Acetonitrile (methyl cyanide) is a common industrial organic solvent but is a rare cause of poisoning. We report the first recorded UK case. Acetonitrile is slowly converted to cyanide, resulting in delayed toxicity. We describe a case of deliberate self-poisoning by a 39-year-old woman resulting in cyanide poisoning 11 hours later which was successfully treated by repeated boluses of sodium nitrite and thiosulphate. The half-life of conversion of acetonitrile was 40 hours and harmful blood cyanide levels persisted for over 24 hours after ingestion. Departments treating or advising in cases of poisoning need to be aware of the delayed toxicity of acetonitrile. Monitoring in an intensive care unit of cases of acetonitrile poisoning should continue for 24-48 hours.

Reduction of pulmonary capillary blood volume in patients with severe unexplained pulmonary hypertension

BACKGROUND

Unexplained or primary pulmonary hypertension results in an obliteration and obstruction of resistance pulmonary arteries. In these patients gas exchange is impaired and the measurement of gas transfer for carbon monoxide is usually reduced. This has been thought to represent a reduction in pulmonary alveolar capillary blood volume (Vc). A single breath test, measuring simultaneously the uptake of both nitric oxide (NO) and carbon monoxide (CO), provides a simple and practical measurement of membrane diffusion (Dm) and Vc.

METHODS

A standard single breath test for the measurement of gas transfer for carbon monoxide (TLCO) was adapted to include NO (40 ppm) in the inhaled gas mixture and a breath-hold time at total lung capacity of 7.5 seconds was used. Twelve patients with primary pulmonary hypertension and 10 similar normal volunteers were studied while seated at rest.

RESULTS

The patients had reduced values for TLCO and TLNO. The mean (SD) value of Dm in the patients was 36.7 (32.1) mmol/min.kPa compared with 52.8 (23.9) mmol/min.kPa in the normal subjects. Vc in the patients was 0.03 (0.03) 1 and 0.06 (0.01) 1 in the normal subjects.

CONCLUSIONS

The simultaneous measurement of NO and CO uptake is possible in healthy volunteers and patients with primary hypertension. In these patients capillary blood volume is reduced compared with normal subjects.

Elevated exhaled nitric oxide in patients with hepatopulmonary syndrome

The hypoxaemia of hepatopulmonary syndrome, seen in severe chronic liver dysfunction, occurs as a result of precapillary pulmonary arterial dilatation and arteriovenous communications. These abnormalities contribute to the mismatch between ventilation and perfusion, and the right to left blood flow shunting. Nitric oxide (NO) is a powerful vasodilator concerned with the regulation of pulmonary vascular tone in man. Using a chemiluminescence analyser, we have measured endogenously produced NO in the exhaled air of three patients with the hepatopulmonary syndrome, six normoxaemic cirrhotic patients and six healthy volunteers. The subjects breathed NO-free air throughout the measurements. The molar rate of production of exhaled NO was raised almost threefold in the patients with hepatopulmonary syndrome compared with normal volunteers and with normoxaemic cirrhotic patients. Hypoxia per se, achieved in the normal volunteers by breathing a hypoxic gas mixture, reduced rather than increased the exhaled NO. One hepatopulmonary syndrome patient received an orthotopic liver transplant and achieved normoxaemia after 3 months. The exhaled NO also returned to normal. Increased pulmonary production of NO could contribute to the development of the hepatopulmonary syndrome.

Case report: perinephric-splenic fistula--a complication of percutaneous perinephric abscess drainage

A case of acute perinephric abscess due to chronic parenchymal disease and calculi is presented. During percutaneous drainage a reno-splenic vein communication developed acutely. The aetiology and treatment complications of perinephric abscesses are reviewed.

Mixed expired nitric oxide in primary pulmonary hypertension in relation to lung diffusion capacity

The mixed expired nitric oxide (NO) production of the lungs of patients with primary pulmonary hypertension (PPH) and normal subjects was measured to determine the relationship between NO production and the diffusion capacity of the lung (KCO). Expired air was collected from eight patients with PPH and 20 healthy volunteers for analysis by a chemiluminescent analyser. Mean pulmonary artery pressure in the PPH patients was 59.5 +/- 6.45 mmHg and their mean cardiac output was 2.95 +/- 0.35 l/min. All patients and subjects underwent measurements of FEV1, VC and KCO. The rate of production of NO in mixed exhaled air was lower in the PPH group compared to the controls (2.85 +/- 0.7 vs. 4.69 +/- 0.35 nM/min; p < 0.05). There was a good correlation of expired NO with the KCO (r = 0.7; n = 30; p < 0.001). When corrected, KCO differences in exhaled NO were not significant (p = 0.09). We conclude that the low exhaled NO observed in PPH patients is a reflection of the reduced blood capillary volume in these patients rather than a decreased basal production of NO.

Measurement of exhaled nitric oxide in man

BACKGROUND

Nitric oxide is released from pulmonary endothelial cells and contributes to the low pulmonary vascular resistance. The resistance pulmonary arteries are in close anatomical proximity to membranous airways, so it is likely that some pulmonary endothelial nitric oxide will enter the airspace to allow its measurement in the exhaled breath.

METHODS

Exhaled air was collected from a single full exhalation and during tidal breathing. This was analysed for concentrations of nitric oxide, nitrogen dioxide, and carbon dioxide to give alveolar (FA) and mixed expired (FE) concentrations. Eight normal subjects were studied and laboratory air was similarly analysed using, respectively, chemiluminescent and infrared analysers.

RESULTS

There was no relation between FA concentrations and the laboratory air concentrations. From the single breath, the ratio of (Fano/Faco2) x (Feco2/Feno) had a mean value of 0.92 (95% confidence interval 0.7 to 1.14). As this does not differ from unity, nitric oxide is likely to be derived from the same regions of the lungs as carbon dioxide. During tidal breathing the Feno ranged from 8.3 to 20.3 parts per billion.

CONCLUSIONS

It is possible to measure endogenous pulmonary nitric oxide production in the exhaled air in man.

Nitric oxide yields of contemporary UK, US and French cigarettes

To determine what governs nitric oxide (NO) yields of cigarettes and to obtain a range of yields for contemporary cigarettes 17 UK, 14 US, 8 French and 1 Turkish brand were analysed using a chemiluminescent analyser and standard smoking machine. The country of origin appeared to be the major factor affecting NO yield. US and French brands exceeded UK values by 3-5 fold. Apart from a reduced NO yield in UK ventilated filtered brands, the design of a cigarette and its tar, nicotine and carbon monoxide (CO) yield had little effect on NO yield. It is argued that these international differences in NO yields reflect differences in the nitrate content of tobaccos traditionally used in manufacture in those countries over many years. Despite their probable increased lifetime exposure to NO (and by implication nitrosamine exposure) there appears to be little evidence that US and French smokers are at greater risk of lung disease than their UK counterparts.

Biochemical and clinical correlates of diuretic therapy in the elderly

To estimate the frequency of diuretic-related electrolyte disorders in the elderly, 561 consecutive admissions to three acute geriatric units were studied. For the 287 admissions to one unit, discharge/death diagnoses were also examined in relation to admission diuretic therapy. Sodium concentrations were significantly lower, and urea and creatinine significantly higher, in patients on diuretics, though the size of the differences was small. Comparing different preparations sodium concentrations were significantly lower on Moduretic than on Dyazide or Navidrex K and on frusemide when combined with a potassium-retaining diuretic rather than a potassium supplement. Potassium concentrations were significantly lower on Bendrofluazide alone compared to Navidrex K or Moduretic. Diuretics were positively associated with cardiac failure, ischaemic heart disease, airflow obstruction and obstructive large bowel disorders but negatively with Parkinson's disease. No significant association was found with falls, immobility or confusion. Major electrolyte disorders on diuretics appear to be unusual but important differences exist between preparations. Similarly major illness resulting from diuretic therapy is rare but minor morbidity may be more common.

Chemical specificity of coughing in man

The purpose of this study was to test whether cough response to inhaled ultrasonically nebulized fluid is dependent on the ionic content of the fluid. Coughing was recorded in human volunteers during inhalation of aqueous solutions in a series of double blind randomized experiments. The occurrence of cough was found to be dependent on the concentration of chloride ions in the inhaled fluid, cough frequency progressively increasing as chloride ion concentration was reduced. It is proposed that the ion composition of the surface lining fluid of the airway may moderate the cough response by means of a chemo-receptor, although tonicity may also be important.

Methemoglobin levels in smokers and non-smokers

The authors analyzed the blood of a group of 336 smokers and 336 non-smokers to determine if tobacco smoke, potentially the major source of nitrogen oxide pollution for 40% of the adult population, significantly reduces oxygen carrying capacity as a result of methemoglobin formation. Each blood sample was analyzed for carboxyhemoglobin, methemoglobin, and hemoglobin using an automated spectrophotometer. The mean value of methemoglobin in the smokers did not exceed that in the non-smokers; in fact, the level in the non-smokers was significantly greater. As expected, carboxyhemoglobin levels in smokers substantially exceeded those in non-smokers. The authors conclude that methemoglobin arising from cigarette smoke exposure does not interfere with the oxygen carrying capacity of the blood in smokers.

Pulmonary epithelial permeability after inhaling saline, distilled water "fog" and cold air

It is recognized that hyperventilation of cold air and the inhalation of fine mists of distilled water provoke significant bronchoconstriction in the asthmatic individual, yet little is known as to how these provocations affect the structural integrity of the alveolar epithelial membrane. In 11 normal subjects, the following effects have been studied: cold air hyperventilation for three minutes, inhalation of 80 L of ultrasonically nebulized distilled water "fog," and 80 L of isotonic saline "fog" on the half time clearance (T1/2) from the alveoli of technetium 99m diethylene triamine penta acetate (DTPA), inhaled as an aerosol. The DTPA T1/2 provided a measurement of pulmonary epithelial permeability.

Carbon monoxide yield of cigarettes and its relation to cardiorespiratory disease

Estimates of the carbon monoxide yield of their cigarettes have been obtained for 4910 smokers (68% of all smokers) in the Whitehall study of men aged 40 to 64. In the 10 years after examination 635 men died. When men smoking cigarettes with high carbon monoxide yield were compared with those smoking cigarettes with a low yield, and after adjusting for age, employment grade, amount smoked, and tar yield, the risk of death was 32% lower for coronary heart disease, 49% higher for lung cancer, and 10% lower for total mortality; these differences were not statistically significant. Among men who said that they inhaled the risk of fatal coronary heart disease was 51% lower in the high carbon monoxide group (p less than 0.01), while the risk of lung cancer was 75% higher. These results provide no evidence that a smoker can reduce his risk of death by smoking a brand with a low carbon monoxide yield; he might even increase it. The complex interactions between characteristics of the smoker, smoking behaviour, constituents of tobacco smoke, and health are again demonstrated.