Intermittent positive pressure ventilation by nasal mask: technique and applications.

Intermittent positive pressure ventilation delivered non-invasively through a well-fitting nasal mask has been used to control nocturnal hypoventilation in three patients with severe, combined cardiorespiratory and skeletal disease. The advantages of this approach to domiciliary ventilation are described and the requirements of the ventilator are defined.

Use of prostacyclin and ultrafiltration in adult respiratory distress syndrome.

A primigravida with severe kyphoscoliosis developed cardio-respiratory failure in pregnancy. Cardiac arrest occurred 10 days after Caesarean section; gastric acid was aspirated then and was followed by the development of adult respiratory distress syndrome. Initial recovery, with clearing of peripheral oedema, was followed by a recurrence of respiratory distress associated with infection. Profound hypoxaemia and oliguria unresponsive to diuretics were relieved by the infusion of prostacyclin combined with fluid removal by ultrafiltration. This treatment may be of value in the management of respiratory distress syndrome when pulmonary oedema is the dominant feature.

Non-invasive mechanical ventilation for acute respiratory failure.

The value of mechanical ventilation using intermittent positive pressure ventilation delivered non-invasively by nasal mask was assessed in six patients with life threatening exacerbations of chronic respiratory disease. Median (range) arterial oxygen and carbon dioxide tensions were 4.4 (3.5-7.2) kPa and 8.7 (5.5-10.9) kPa respectively, with four patients breathing air and two controlled concentrations of oxygen. The arterial oxygen tension increased with mechanical ventilation to a median (range) of 8.7 (8.0-12.6) kPa and the carbon dioxide tension fell to 8.2 (6.5-9.2) kPa. Four patients discharged after a median of 10 (8-17) days in hospital were well five to 22 months later. One died at four days of worsening sputum retention and another after five weeks using the ventilator for 12-16 hours each day while awaiting heart-lung transplantation. This technique of mechanical ventilation avoids endotracheal intubation and can be used intermittently. Hypercapnic respiratory failure can be relieved in patients with either restrictive or obstructive lung disease in whom controlled oxygen treatment results in unacceptable hypercapnia. Respiratory assistance can be tailored to individual need and undertaken without conventional intensive care facilities.

The intensive care of asthma.

Severe acute asthma is potentially lethal. Deaths occur in hospital unless patients are assessed accurately on admission, monitored regularly, and treated vigorously. Mechanical ventilation is required infrequently and is associated with additional hazards. The principles of management of the severely ill asthmatic are outlined here.

Cardiorespiratory consequences of unfused idiopathic scoliosis.

A retrospective survey was carried out on approximately 800 scoliotic subjects attending a chest clinic over 25 years. One hundred thirty-one patients with unfused idiopathic scoliosis were identified and further consideration was restricted to 54 who were assessed at 30 years of age or older. Sex, age of onset of curvature, severity at the time of presentation, degree of dyspnoea, presence of independent cardiac or pulmonary disease and smoking habit were recorded. Measurements of lung function were compared with predicted figures calculated according to span, age and sex. Disabling dyspnoea or cardiorespiratory failure were associated with either scoliosis of early onset (curve first noticed before 5 years) or with independent cardiac or pulmonary disease. Only one of 28 patients with unfused idiopathic scoliosis of adolescent onset developed disabling dyspnoea in later life attributable solely to spinal deformity. A similar conclusion was drawn from a separate survey of mortality in 86 patients, 19 of whom suffered from idiopathic scoliosis. Cardiorespiratory failure attributable to the scoliosis was the cause of death of 11 patients, in 10 of whom the curve had first been noticed at less than 5 years of age whereas the onset was during early adolescence (11 years) in only one.

Prevention of neurological damage during open-heart surgery.

A previous study of neurological damage related to open-heart surgery suggested that the onset of cardiopulmonary bypass is a time of particular hazard, and there is evidence that both microemboli from the extracorporeal circulation and inadequate cerebral perfusion may be contributory factors. Measures to eliminate or minimize these hazards have been introduced, and a clinical survey has been undertaken to evaluate their efficacy. There has been a very highly significant decrease in the incidence of neurological damage as judged by comparison with the results of a similar survey carried out before these measures were introduced. In spite of limitations imposed by differences in workload, perfusion techniques, and methods of data collection, it is concluded that the prophylactic measures have been responsible for the reduction in the incidence of neurological damage.

An unexpected complication of the intubating laryngeal mask.

Fatal oesophageal perforation occurred as a complication of elective general anaesthesia for cataract extraction in a 77-year-old female patient. Tracheal intubation had been achieved, albeit with difficulty, in the course of a clinical trial of the intubating laryngeal mask.

Respiration during sleep in kyphoscoliosis.

Eleven subjects with non-paralytic and 10 with paralytic kyphoscoliosis and nine normal control subjects were studied during sleep. The Cobb angle of those with kyphoscoliosis varied from 60 degrees to 140 degrees (median 100 degrees) and the vital capacity varied from 17% to 56% (median 28%) of the value predicted on the basis of span. Recordings made during sleep included expired carbon dioxide tension at the nose, gas flow at the mouth, arterial oxygen saturation, chest wall movement, and the electroencephalogram, electro-oculogram, and electrocardiogram. In three subjects transcutaneous carbon dioxide tension was measured simultaneously. Patients with kyphoscoliosis hypoventilated during sleep, particularly in rapid eye movement sleep, resulting in a rise in end tidal and transcutaneous carbon dioxide tension, and a reduction in oxygen saturation to a degree not observed in normal subjects. Reduced chest wall movement was the major cause of these episodes, which were more frequent and occupied a greater proportion of sleep time in those with kyphoscoliosis than in normal subjects. Serious cardiac arrhythmias were rarely associated. It is concluded that disturbances of respiration during sleep occur in patients with kyphoscoliosis and that these may be important in the pathogenesis of cardiorespiratory failure.

Control of nocturnal hypoventilation by nasal intermittent positive pressure ventilation.

Ten patients with respiratory failure and nocturnal hypoventilation were treated for three to nine months by nasal intermittent positive pressure ventilation. Four patients had chronic obstructive lung disease (median FEV1 19% predicted) and six restrictive chest wall disorders (median FVC 25% predicted); eight of the patients also had cardiac failure. The median daytime arterial oxygen tension, measured before and after at least three months' treatment, increased from 6.2 (range 5.4-9.6) to 9.1 (7.1-9.8) kPa in those with restrictive disease (p less than 0.05), and from 6.0 (5.7-6.5) to 7.1 (6.3-7.7) kPa in the four with airflow limitation (NS). Median values for arterial carbon dioxide tension over the same time fell from 8.2 (range 6.7-9.8) to 6.5 (6.0-6.9) kPa in the group with restrictive disease (p less than 0.05) and from 8.2 (7.0-9.2) to 7.1 (4.9-7.7) kPa in those with airflow limitation (p less than 0.02). Total sleep time while patients were using nasal positive pressure ventilation varied from 155 to 379 (median 341) minutes, and included 4-26% rapid eye movement sleep (median 14%). The percentage of monitored time during the night in which the arterial oxygen saturation was less than 80% fell from a median (range) of 96 (3-100) to 4 (0-9) in the six patients with restrictive disease and from 100 (98-100) to 40 (2-51) in those with airflow limitation. There were no changes in spirometric values but exercise tolerance improved in all patients. The technique may prove an acceptable alternative to long term domiciliary oxygen therapy in selected patients.

Non-invasive measurement of cardiac output during anaesthesia. An evaluation of the soluble gas uptake method.

A technique for measuring cardiac output which depends on the uptake of an inert soluble gas from the lungs has been evaluated during anesthesia. A respiratory mass spectrometer has been used to follow the concentrations of argon and freon-22 during passive rebreathing in anaesthetized patients before cardiopulmonary bypass. Values for cardiac output obtained with this technique are reproducible, but lower than those recorded using the direct Fick technique before and after the rebreathing manoeuvre. A reduction in cardiac output caused by vigorous rebreathing is the most likely explanation for the discrepancy and, although serial measurements of oxygen consumption may permit application of a correction factor, a method of measurement which causes significant haemodynamic disturbance cannot be recommended for widespread use.