Do Not Attempt Cardiopulmonary Resuscitation orders in acute medical settings: a qualitative study

BACKGROUND

Do Not Attempt Cardiopulmonary Resuscitation (DNACPR) orders have been shown to be independently associated with patients receiving fewer treatments, reduced admission to intensive care and worse outcomes even after accounting for known confounders. The mechanisms by which they influence practice have not previously been studied.

OBJECTIVES

To present a rich qualitative description of the use of the DNACPR form in a hospital ward setting and explore what influence it has on the everyday care of patients.

DESIGN

Multi-source qualitative study, primarily using direct observation and semi-structured interviews based on two acute wards in a typical middle-sized National Health Service hospital in UK.

RESULTS

The study identified a range of ways in which DNACPR orders influence ward practice, beyond dictating whether or not cardiopulmonary resuscitation should be attempted. Five key themes encapsulate the range of potential impacts emerging from the data: the specific design and primacy of the form, matters relating to clinical decision making, staff reflections on how the form can affect care, staff concern over 'inappropriate' resuscitation, and discussions with patients/relatives about DNACPR decisions. Overall, it was found that while the DNACPR form is recognized as serving a useful purpose, its influence negatively permeated many aspects of clinical practice.

CONCLUSION

DNACPR orders can act as unofficial 'stop' signs and can often signify the inappropriate end to clinical decision making and proactive care. Many clinicians were uncomfortable discussing DNACPR orders with patients and families. These findings help understand why patients with DNACPR orders have worse outcomes, as such they may inform improvements in resuscitation policies.

Comparison of shuttle walk with measured peak oxygen consumption in patients with operable lung cancer

BACKGROUND

The relationship between the shuttle walk test and peak oxygen consumption in patients with lung cancer has not previously been reported. A study was undertaken to examine this relationship in patients referred for lung cancer surgery to test the hypothesis that the shuttle walk test would be useful in this clinical setting.

METHODS

125 consecutive patients with potentially operable lung cancer were prospectively recruited. Each performed same day shuttle walking and treadmill walking tests.

RESULTS

Shuttle walk distances ranged from 104 m to 1020 m and peak oxygen consumption ranged from 9 to 35 ml/kg/min. The shuttle walk distance significantly correlated with peak oxygen consumption (r = 0.67, p<0.001). All 55 patients who achieved more than 400 m on the shuttle test had a peak oxygen consumption of at least 15 ml/kg/min. Seventy of 125 patients failed to achieve 400 m on the shuttle walk test; in 22 of these the peak oxygen consumption was less than 15 ml/kg/min. Nine of 17 patients who achieved less than 250 m had a peak oxygen consumption of more than 15 ml/kg/min.

CONCLUSION

The shuttle walk is a useful exercise test to assess potentially operable lung cancer patients with borderline lung function. However, it tends to underestimate exercise capacity at the lower range compared with peak oxygen consumption. Our data suggest that patients achieving 400 m on the shuttle walk test do not require formal measurement of oxygen consumption. In patients failing to achieve this distance we recommend assessment of peak oxygen consumption, particularly in those unable to walk 250 m, because a considerable proportion would still qualify for surgery as they had an acceptable peak oxygen consumption.

Relationship between pulmonary function and lung cancer surgical outcome

The British Thoracic Society and American College of Chest Physician guidelines outline criteria for investigating patients for lung cancer surgery. However, the guidelines are based on relatively old studies. Therefore, the relationship between pulmonary function test results and surgical outcome were studied prospectively in a large cohort of lung cancer patients. From January 2001 to December 2003, 110 patients underwent surgery for lung cancer. All underwent full lung function testing in order to predict post-operative lung function. The hospital mortality rate was 3% and major complication rate 22%. There was poor overall outcome in 13%. Mean pre-operative lung function values were: forced expiratory volume in one second (FEV1) 2.0 L (79.4% of the predicted value), and carbon monoxide diffusing capacity of the lung (D(L,CO)) 73.6% pred. The mean post-operative lung function values were: FEV1 1.4 L (55.6% pred), and D(L,CO) 51.3% pred. All lung function values were better predictors of poor surgical outcome when expressed as a percentage of the predicted value. Using a threshold of pre-operative FEV1 of 47% pred resulted in the most useful positive and negative predictive probabilities, 0.90 and 0.67, respectively. Lung function values expressed as a percentage of the predicted value are more useful predictors of post-operative outcome than absolute values. The threshold of predicted forced expiratory volume in one second for surgical intervention could be lower (45-50% pred) than is currently accepted without increased mortality.

Effect of lung cancer surgery on quality of life

BACKGROUND

Health related quality of life (HRQOL) after surgery is important, although very limited data are available on the QOL after lung cancer surgery.

METHODS

The effect of surgery on HRQOL was assessed in a prospective study of 110 patients undergoing potentially curative lung cancer surgery at Papworth Hospital, 30% of whom had borderline lung function as judged by forced expiratory volume in 1 second. All patients completed the EORTC QLQ-C30 and LC13 lung cancer module before surgery and again at 1, 3 and 6 months postoperatively.

RESULTS

On average, patients had high levels of functioning and low levels of symptoms. Global QOL had deteriorated significantly 1 month after surgery (p = 0.001) but had returned to preoperative levels by 3 months (p = 0.93). Symptoms had worsened significantly at 1 month after surgery but had returned to baseline levels by 6 months. Low values on the preoperative HRQOL scales were not significantly associated with poor surgical outcome. However, patients with low preoperative HRQOL functioning scales and high preoperative symptom scores were more likely to have poor postoperative (6 months) QOL. The only lung function measurement to show a marginally statistically significant association with quality of life at 6 months after surgery was percentage predicted carbon monoxide transfer factor (Tlco).

CONCLUSION

Although surgery had short term negative effects on quality of life, by 6 months HRQOL had returned to preoperative values. Patients with low HRQOL functioning scales, high preoperative symptom scores, and preoperative percentage predicted Tlco may be associated with worse postoperative HRQOL.

The value of performing head CT in screening for cerebral metastases in patients with potentially resectable non-small cell lung cancer: experience from a UK cardiothoracic centre

AIM

To evaluate the whether screening for cerebral metastases in neurologically intact patients with potentially resectable non-small cell lung cancer patients is both worthwhile and cost-effective.

METHODS

We prospectively performed computed tomography (CT) of the head in 105 consecutive patients with potentially resectable lung cancer over an 18-month period. None of these patients had neurological symptoms or signs.

RESULTS

Five patients (4.8%) with cerebral metastases were identified using CT. At our institution the financial saving of avoiding five thoracotomies was pound sterling 45,000, whilst the cost of performing 105 head CTs was pound sterling 16,000. This represented a substantial saving for the healthcare provider and preserved the quality of life in five patients.

CONCLUSIONS

We conclude that screening for cerebral metastases in neurologically intact patients with potentially resectable non small cell lung cancer patients is both worthwhile and cost effective.

Kyphosis secondary to tuberculosis osteomyelitis as a cause of ventilatory failure. Clinical features, mechanisms, and management

STUDY OBJECTIVES

To investigate the relationship of thoracic kyphosis following tuberculosis to the development of ventilatory failure and to assess the efficacy on nocturnal noninvasive ventilatory support.

DESIGN

Retrospective consecutive case series with crossover from a phase without noninvasive ventilatory support to a phase with this treatment.

SETTING

The Respiratory Support and Sleep Centre, Papworth, Hospital, Cambridge, England.

PATIENTS

Seven patients with thoracic kyphosis following tuberculous osteomyelitis which had been contracted by the age of 4 years were studied. Their mean age was 53 (SD 7.1) years and the mean angle of kyphosis was 113.60. All patients were in ventilatory failure.

INTERVENTIONS

The patients were treated with nocturnal noninvasive ventilation with either an individually constructed cuirass shell and a negative pressure pump or nasal intermittent positive pressure ventilation using a volume preset ventilator.

MEASUREMENT AND RESULTS

Each patient underwent an initial clinical assessment along with radiologic studies of the spine, pulmonary function tests, daytime arterial blood gas tensions, and overnight recordings of arterial saturation, and transcutaneous carbon dioxide tension. They were reassessed in detail at a mean of 5 years after starting ventilatory support. Symptoms, vital capacity, daytime carbon dioxide tension, and overnight oximetry had all improved following treatment. Temporary withdrawal of ventilatory support led to severe sleep fragmentation in four patients and the appearance of central apneas and hypopneas in the other three. Six of the 7 patients were alive at a mean of 5.7 years after starting nocturnal ventilation.

CONCLUSION

These results show that ventilatory failure may develop, after an interval of many years, in patients with a severe thoracic kyphosis due to tuberculosis in childhood. Noninvasive nocturnal ventilatory support can control the symptoms of ventilatory failure, improve the physiologic abnormalities, and is associated with prolonged survival.

Multiple recurrent intrapulmonary and endobronchial mesenchymomas (hamartomas)

A patient is described with multiple, benign, chondromatous intrapulmonary and endobronchial mesenchymomas of the lung, which recurred after resection on two occasions over a period of 30 years. In such a patient presenting at a young age or with a history of previous recurrence, a wedge excision may be necessary to prevent further recurrence.

Massive hemothorax due to enlarging arteriovenous fistula in pregnancy

A 37-year-old woman with hereditary telangiectasia suffered a life-threatening hemothorax due to an enlarging pulmonary arteriovenous malformation in pregnancy. This was treated by emergency right lower lobectomy and excision of arteriovenous malformations in the right middle and upper lobes, with no postoperative complications, and the subsequent delivery of a normal infant. Women with hereditary telangiectasia contemplating pregnancy should be screened for the presence of PAVM to anticipate complications.

Inspiratory muscle relaxation rate after voluntary maximal isocapnic ventilation in humans

We have investigated whether the capacity of the inspiratory muscles to generate pressure and flow during a ventilatory load is related to changes in inspiratory muscle relaxation rate. Five highly motivated normal subjects performed voluntary maximal isocapnic ventilation (MIV) for 2 min. Minute ventilation and esophageal, gastric, and transdiaphragmatic pressures were measured breath by breath. We observed that ventilation, peak inspiratory and expiratory pressures, and inspiratory flow rate declined from the start of the run to reach a plateau at 60 s that was sustained for the remainder of the exercise. In a subsequent series of studies, MIV was performed for variable durations between 15 and 120 s. The normalized maximum relaxation rate of unoccluded inspiratory sniffs (sniff MRR, %pressure loss/10 ms) was determined immediately on stopping MIV. Sniff MRR slowed as the duration of MIV increased and paralleled the decline in inspiratory pressure and ventilation observed during the 2-min exercise. No further slowing in MRR occurred when ventilation became sustainable. We conclude that, during MIV, the progressive loss of ventilation and capacity to generate pressure is associated with the early onset and progression of a peripheral fatiguing process within the inspiratory muscles.

The effect of posture and abdominal binding on respiratory pressures

We examined the effect of posture on the generation of respiratory pressures in 6 highly trained subjects. Transdiaphragmatic pressure was measured at FRC during bilateral percutaneous phrenic nerve stimulation (twitch Pdi) and maximal sniffs (sniff Pdi), with the abdomen bound and unbound. Maximum static inspiratory (PImax) and expiratory (PEmax) mouth pressures were measured with the abdomen unbound. Three postures were examined: seated (Se), semi-supine (30s), and supine (Su). Changes of posture did not significantly alter twitch Pdi. By contrast, sniff Pdi and static mouth pressures were significantly reduced in the Su posture. Abdominal binding significantly increased twitch Pdi only. We conclude that voluntary respiratory manoeuvres requiring activation, recruitment and coordination of different muscle groups are performed better in the Se position. We suggest that posture be standardised for serial comparative measurements of voluntary respiratory pressures in a given subject.

Respiratory muscle weakness in the Lambert-Eaton myasthenic syndrome

Respiratory muscle function was assessed in six patients with the Lambert-Eaton myasthenic syndrome. Five had histologically proved small cell carcinoma of the lung; the sixth later developed metastases from an unknown primary site. Two patients had ventilatory failure, one without respiratory symptoms; another, who had emphysema, had dyspnoea and orthopnoea. The remaining three patients had no respiratory symptoms. Four patients had limb muscle weakness as judged by the maximal voluntary contraction of the quadriceps muscle (range for all subjects 32-100% predicted). Transdiaphragmatic pressure (Pdi) was measured during a maximal unoccluded sniff (Pdi: sniff), a maximal sustained inspiratory effort against a closed airway (Pdi: Pimax), and phrenic nerve stimulation (Pdi: twitch). Mild to moderate diaphragmatic weakness was present in all six patients in proportion to the degree of leg weakness (Pdi: sniff 30-64% predicted; r = 0.6; Pdi:Pimax 6-69% predicted, r = 0.8); this was associated with very low or absent Pdi:twitch during phrenic nerve stimulation. Four patients had weakness of the expiratory muscles. Improvement in muscle strength was documented in two patients after tumour chemotherapy and specific treatment with 3,4-diaminopyridine and prednisolone; one patient was still alive five years from first diagnosis. It is concluded that the respiratory muscles may be implicated in this condition more often than has previously been recognised. As the lack of mobility may cause respiratory symptoms to be minimised, the presence of respiratory muscle weakness may remain undiagnosed unless formal measurement of respiratory muscle function is made.

The effect of posture and abdominal binding on respiratory pressures

We examined the effect of posture on the generation of respiratory pressures in 6 highly trained subjects. Transdiaphragmatic pressure was measured at FRC during bilateral percutaneous phrenic nerve stimulation (twitch Pdi) and maximal sniffs (sniff Pdi), with the abdomen bound and unbound. Maximum static inspiratory (PImax) and expiratory (PEmax) mouth pressures were measured with the abdomen unbound. Three postures were examined: seated (Se), semi-supine (30s), and supine (Su). Changes of posture did not significantly alter twitch Pdi. By contrast, sniff Pdi and static mouth pressures were significantly reduced in the Su posture. Abdominal binding significantly increased twitch Pdi only. We conclude that voluntary respiratory manoeuvres requiring activation, recruitment and coordination of different muscle groups are performed better in the Se position. We suggest that posture be standardised for serial comparative measurements of voluntary respiratory pressures in a given subject.

Respiratory muscle weakness and fatigue

Respiratory muscle weakness can result from a variety of neuromuscular disorders, and it is now possible to identify different patterns of weakness and quantify the extent of this weakness using reliable, sensitive tests of respiratory muscle strength. However the quantification of respiratory muscle 'fatigue' has proved more difficult, and it is now recognized that there is unlikely to be one single index of fatigue, rather a whole sequence of changes that occur in response to loading. It is likely that in practice, a close interplay between respiratory pump capacity, demands on the pump and more especially, adaptive changes in respiratory drive, protect the respiratory muscles from overt peripheral contractile failure, and that the fall in tension following prolonged muscular activity involves many different closely inter-related processes. Investigation of these processes is likely to be more rewarding than attempts to develop a single 'test of fatigue', and may lead to an improved understanding of the role of respiratory muscle dysfunction in ventilatory failure.

Diaphragm strength in the shrinking lung syndrome of systemic lupus erythematosus

The cause of the reduced lung volume in the 'shrinking lung' syndrome of systemic lupus erythematosus (SLE) was investigated in 12 patients with the condition. Nine patients described persistent episodes of pleuritic chest pain. Narrow section (3 mm) computed tomography of the thorax revealed no interstitial fibrosis or significant pleural disease. Assessment of diaphragmatic function using manoeuvres more reliable than the maximal occluded efforts previously used alone to assess respiratory muscle strength, showed that diaphragm strength was unequivocally normal in nine of 12 patients. In three, maximum transdiaphragmatic pressure was moderately reduced, but phrenic nerve stimulation demonstrated that this was due to incomplete activation of the diaphragm during a maximal voluntary effort, rather than to a primary abnormality of the diaphragm. Results of maximum lung recoil pressures and dynamic compliance, and analysis of the 12-s maximum voluntary ventilation, suggested a restriction in chest-wall expansion, although it was not possible to identify the underlying cause of this on the basis of our results. We conclude that the 'shrinking lung' syndrome of SLE is not explained by a primary abnormality of the diaphragm.

The measurement of inspiratory muscle strength by sniff esophageal, nasopharyngeal, and mouth pressures

Sniff esophageal pressure (Pes) is a useful measurement of global inspiratory muscle strength, although it does require passage of an esophageal balloon. We investigated the relationship between nasopharyngeal pressure (Pnp) or pressure within the mouth (Pmo) and Pes during a maximal sniff from FRC without a noseclip. We measured Pes, Pnp, and Pmo simultaneously in 10 normal volunteers, and in 12 patients with inspiratory muscle weakness. In both groups, Pnp and Pmo were slightly less but very close to Pes. In normal volunteers, the mean ratio Pnp/Pes was 0.92 +/- 0.006 (mean +/- SE) and Pmo/Pes was 0.95 +/- 0.006. Regression analysis showed Pes = 4.57 + 1.05 Pnp (r = 0.995, p less than 0.001) and Pes = 0.74 + 1.05 Pmo (r = 0.994, p less than 0.001). Similar relationships between Pnp, Pmo, and Pes were found over a wide range of pressures generated by submaximal sniffs in normal subjects. In patients, the mean ratio Pnp/Pes was 0.90 +/- 0.02 and Pmo/Pes was 0.87 +/- 0.03. Regression analysis showed Pes = 5.12 + 1.0 Pnp (r = 0.949, p less than 0.001) and Pes = 11.2 + 0.882 Pmo (r = 0.936, p less than 0.001). We conclude that Pnp and Pmo predict Pes during a maximal sniff in both normal subjects and in patients with inspiratory muscle weakness. Sniff Pnp and/or Pmo may provide a useful and less invasive method of measuring maximal inspiratory pressures during a sniff.

Clinical significance of severe isolated diaphragm weakness

We studied six patients with isolated bilateral paralysis or severe weakness of the diaphragm, present for 2 to 60 months (mean = 25), to document the clinical and respiratory sequelae of the condition. Severe diaphragm dysfunction was confirmed by the demonstration of the very low maximal transdiaphragmatic pressure (Pdi) generated by either a sniff (13 +/- 6 cm H2O, normal 148 +/- 24) or a static inspiration (11 +/- 8, normal 108 +/- 30) and during bilateral phrenic nerve stimulation (0.8 +/- 2.0, normal 22 +/- 4). Resting arterial blood gases were normal (SaO2 = 95 to 97%) and no oxygen desaturation occurred during maximal exercise on a treadmill. Maximum voluntary ventilation was low and related to PImax (r = 0.89). Overnight sleep monitoring showed that time spent in rapid eye movement sleep was normal (mean 55 +/- 36 min, range 26 to 117 min). Mean maximum increment in transcutaneous CO2 was within normal limits (6 +/- 2 mm Hg, range 3 to 9 mm Hg). Three patients had occasional brief episodes of oxygen desaturation (mean maximal decrease 13 +/- 10%, range 2 to 27%); however, only two of these spent a measurable proportion of total sleep time (TST) with an SaO2 of less than 80% (1% and 3% TST, respectively). No patient has developed any symptoms of nocturnal hypoventilation or chronic respiratory failure during periods of observation of up to five yr. We conclude that bilateral paralysis or very severe weakness of the diaphragm does not of itself lead to respiratory failure unless weakness of other respiratory muscles is present.

Comparison of two different mouthpieces for the measurement of Pimax and Pemax in normal and weak subjects

We investigated the effect of mouthpiece design on maximum static expiratory (PEmax) and inspiratory (PImax) mouth pressures. We measured PEmax from total lung capacity (TLC) and PImax from residual volume (RV) in 21 healthy volunteers, and in 40 patients referred for respiratory muscle testing. We compared two different mouthpieces, a semi-rigid plastic flanged type fitting inside the lips, and a 4 cm diameter rubber tube held against the lips. The tube mouthpiece gave significantly higher values for PEmax (p less than 0.02) in all subjects. PImax was also significantly higher (p less than 0.005) with the tube mouthpiece in subjects who recorded normal pressures. We conclude that maximum pressures are obtained in all normal subjects with the rubber tube mouthpiece, and that differences in quoted normal ranges of maximum static respiratory pressures reflect in part the design of the mouthpiece and the way in which it was used.

Comparison of two different mouthpieces for the measurement of Pimax and Pemax in normal and weak subjects

We investigated the effect of mouthpiece design on maximum static expiratory (PEmax) and inspiratory (PImax) mouth pressures. We measured PEmax from total lung capacity (TLC) and PImax from residual volume (RV) in 21 healthy volunteers, and in 40 patients referred for respiratory muscle testing. We compared two different mouthpieces, a semi-rigid plastic flanged type fitting inside the lips, and a 4 cm diameter rubber tube held against the lips. The tube mouthpiece gave significantly higher values for PEmax (p less than 0.02) in all subjects. PImax was also significantly higher (p less than 0.005) with the tube mouthpiece in subjects who recorded normal pressures. We conclude that maximum pressures are obtained in all normal subjects with the rubber tube mouthpiece, and that differences in quoted normal ranges of maximum static respiratory pressures reflect in part the design of the mouthpiece and the way in which it was used.

The value of sniff esophageal pressures in the assessment of global inspiratory muscle strength

Esophageal pressure generated during a maximal sniff (sniff Pes) was compared with mouth pressure generated during a maximal inspiration against a closed airway (Pimax) as a measure of global inspiratory muscle strength in 61 patients referred for investigation of respiratory muscle function. Transdiaphragmatic pressure (Pdi) was also measured during both maneuvers to compare maximal diaphragmatic strength. Sniff Pes (males, 68 +/- 27 cm H2O; normal greater than 53; females, 66 +/- 21; normal greater than 48) was greater than Pimax (males, 45 +/- 24 cm H2O; normal greater than 42; females, 42 +/- 24; normal greater than 17) in 55 of the 61 patients, both in absolute values and as a percentage of normal. In 36 patients Pimax and sniff Pes were both normal (mean +/- 2 SD), whereas in 13 patients they were both low. In 11 patients, Pimax was low, but sniff Pes was normal. One patient had a reduced sniff Pes but a Pimax at the lower limit of normal. In the 36 patients in whom both Pimax and sniff Pes were normal, Pdi was also normal or only moderately reduced, and in the 13 patients in whom both Pimax and sniff Pes were reduced, Pdi was very low. However, in the group of 11 patients with a low Pimax but a normal sniff Pes, Pdi was normal or only moderately reduced, suggesting that Pimax was falsely low, perhaps because of difficulties with the technique. Conversely, in the single patient with a low sniff Pes but a Pimax just within the normal range, Pdi was very low. We conclude that measurement of esophageal pressure during a maximal sniff is a useful test of inspiratory muscle strength and overcomes the difficulty some patients have in carrying out the Pimax maneuver.

Hypothyroidism presenting with respiratory muscle weakness

A 58-yr-old woman presented with recurrent chest infections, breathlessness, and orthopnea. She complained of nonspecific tiredness and aching limbs. A chest radiograph showed an elevated right hemidiaphragm. Thyroid function tests showed her to be severely hypothyroid (T4 = 23 nmol/L; TSH greater than 50 mU/L). Measurement of maximal respiratory mouth pressures (expiratory: 50 cm H2O, normal, 94 +/- 33; inspiratory: 15 cm H2O, normal, 71 +/- 27) suggested global respiratory muscle weakness. Severe bilateral diaphragm weakness was demonstrated by a greatly reduced maximal transdiaphragmatic pressure (Pdi) (Pdi Pimax = 0, normal, 65 +/- 31 cm H2O; sniff Pdi = 25 cm H2O, normal, 121 +/- 25). No Pdi was detectable on stimulation of the right phrenic nerve, whereas, on the left, it was 11 cm H2O (normal 7 to 15 cm H2O). Phrenic nerve conduction time was prolonged to both sides (right, 12 ms, left, 10 ms; normal, less than 9.5 ms). The relaxation rate of Pdi after a maximal sniff and after bilateral phrenic nerve stimulation was abnormally slow (7.4%/10 ms, 6.3%/10 ms, respectively). Three months after starting treatment with thyroxine she had become euthyroid, and phrenic nerve conduction times and Pdi relaxation rates had returned to normal. Maximal respiratory pressures, vital capacity, and maximal voluntary ventilation improved progressively on treatment, although maximal respiratory pressures still had not reached the normal range after six months. We conclude that hypothyroidism may present with breathlessness due to respiratory muscle weakness and/or phrenic nerve neuropathy and is reversible with treatment.

Diaphragm weakness in Charcot-Marie-Tooth disease

Two patients are described with Charcot-Marie-Tooth disease and chronic peripheral neuropathy. Both had dyspnoea, orthopnoea, and evidence of severe diaphragm weakness. Expiratory muscle function was well preserved and abnormalities of gas exchange during sleep were only minor.

Diaphragm strength in patients with recent hemidiaphragm paralysis

Eleven patients with unilateral diaphragm paralysis of recent onset were studied to investigate the effect of the paralysis on inspiratory muscle function. Nine of the patients had noticed a decrease in exercise tolerance, which was not explained by any other pathological condition. Hemidiaphragm dysfunction was confirmed by the demonstration of a greatly reduced or absent transdiaphragmatic pressure on stimulation of the phrenic nerve in the neck, by means of surface bipolar electrodes (unilateral twitch Pdi), compared with normal values on the contralateral side. Transdiaphragmatic pressure was 44.6% (9.4%) predicted during a maximal sniff and 30.3% (16.8%) predicted during a maximal static inspiration against a closed airway, confirming diaphragm weakness. Maximum static inspiratory mouth pressures were also low (61.7% (12.7%) predicted), consistent with a reduction in inspiratory muscle capacity. Phrenic nerve conduction time was prolonged on the affected side in nine patients, consistent with phrenic nerve dysfunction, whereas on the unaffected side it was normal. It is concluded that recent hemidiaphragm paralysis causes a reduction in transdiaphragmatic pressure that is associated with a reduction in maximum inspiratory mouth pressure. Phrenic nerve stimulation is a useful technique with which to confirm and quantify hemidiaphragm dysfunction. Measurement of phrenic nerve conduction time provides useful information about the underlying pathology.

Fenoterol solution via nebuliser--optimum dosage

We report the results of a double-blind controlled study of 20 asthmatic patients to determine the optimum dose of fenoterol given by nebuliser. Lung function was monitored after four different doses (0.5 mg, 1.25 mg, 2.5 mg, 5 mg) and placebo. All four doses of fenoterol were found to be significantly superior to placebo. Doses of 5 mg and 2.5 mg were also significantly more effective than the 0.5 mg dose up to 3 h. There was no significant difference between the three highest doses. In this study of relatively stable asthmatics, the increased bronchodilatation obtained with the higher doses of fenoterol (5 mg and 2.5 mg) was not sufficient to offset the higher incidence of side-effects, and we therefore recommend 1.25 mg as a starting dose. Higher doses may be needed for severely ill patients in whom side-effects are not such an important consideration.

Domiciliary nebulisers in asthma: a district survey

Fifty three patients who were found to be using a home nebuliser for asthma completed a questionnaire. The results showed some confusion about the criteria for recommending whether a patient should buy a nebuliser and for its correct use. Twelve patients had not received any instruction on the use of their nebuliser, and only 11 of those old enough used a peak flow meter in conjunction with it. Eight patients aged 7-15 were using inhaled sympathomimetic aerosols only at the time of buying a nebuliser as compared with most of the older patients, who were using regular oral steroids. Forty nine patients assessed their asthma as moderate to severe, but eight of these were not attending a hospital clinic. Several patients were using 20 mg salbutamol or more every day, and on occasion doses of up to 50 mg a day were reported. It is recommended that patients should be assessed before they buy a nebuliser and advice given on correct use by a district nebuliser service, organised either by respiratory function technicians or in physiotherapy departments for adults together with a paediatric health visitor for children.

Pituitary Cushing's disease arising from a previously non-functional corticotrophic chromophobe adenoma

Severe pituitary Cushing's disease of sudden onset after 18 years of unsuccessful treatment for a previously non-functioning chromophobe adenoma is described in a middle-aged woman. Initial presentation with symptoms of optic nerve compression had been preceded by two years of amenorrhoea. Transfrontal resection of a chromophobe adenoma followed by radiotherapy, performed both at this time and again after a recurrence eight years later, failed to eradicate the tumour. Ten more years elapsed before she rapidly developed florid features of Cushing's syndrome. Plasma ACTH levels were markedly elevated and were only partially reduced by further transfrontal surgery, complete removal of the tumour proving impossible. Subsequent bilateral adrenalectomy was performed to control her hypercortisolism and a course of cytotoxic chemotherapy was administered in an attempt to treat the tumour recurrence. Immunocytochemical staining of tumour obtained at surgery demonstrated ACTH immunoreactivity both before and after the development of Cushing's disease. Although silent corticotrophic adenomas of the human pituitary, including chromophobic tumours, have been previously described, this is the first report of such a tumour becoming functional, sufficient to cause clinically evident Cushing's disease.