N. A. Saunders

Obstructive sleep apnea in family members.

Two sons and their father had severe hypersomnolence and obstructive sleep apnea. A third son, although asymptomatic, was shown to have upper-airway obstruction during sleep. Electromyographic recordings of genioglossus activity in the two symptomatic sons revealed loss of tonic activity in early stages of sleep at times when sleep apnea occurred. The asymptomatic son showed loss of tonic activity during rapid-eye-movement sleep, the sleep period when upper-airway obstruction occurred. Two sudden deaths occurred in this family. A 30-year-old brother died at home while asleep, and a child of the asymptomatic brother died at the age of four months from presumed sudden-infant-death syndrome. Obstructive sleep apnea may have a familial basis; the tongue may be involved in the genesis of upper-airway obstruction during sleep.

Nocturnal hypoxaemia and quality of sleep in patients with chronic obstructive lung disease.

Fifty patients with chronic obstructive lung disease were questioned about their sleep quality and their responses were compared with those of 40 similarly aged patients without symptomatic lung disease. Patients with chronic obstructive lung disease reported more difficulty in getting to sleep and staying asleep and more daytime sleepiness than the control group. More than twice as many patients (28%) as controls (10%) reported regular use of hypnotics. In a subgroup of 16 patients with chronic obstructive lung disease (mean FEV1 0.88 (SD 0.44) sleep, breathing, and oxygenation were measured to examine the relationship between night time hypoxaemia and sleep quality. Sleep architecture was disturbed in most patients, arousals occurring from three to 46 times an hour (mean 15 (SD 14)/h). Arterial hypoxaemia during sleep was common and frequently severe. The mean (SD) arterial oxygen saturation (SaO2) at the onset of sleep was 91% (7%). Nine patients spent at least 40% of cumulative sleeping time at an SaO2 of less than 90% and six of these patients spent 90% of sleeping time below this level. Only four of 15 patients did not develop arterial desaturation during sleep. The mean minimum SaO2 during episodes of desaturation was less in rapid eye movement (REM) sleep (72% (17%)) than in non-REM sleep (78% (10%), p less than 0.05). The predominant breathing abnormality associated with desaturation was hypoventilation; only one patient had obstructive sleep apnoea. Arousals were related to oxygenation during sleep such that the poorer a patients arterial oxygenation throughout the night the more disturbed his sleep (arousals/h v SaO2 at or below which 40% of the total sleep time was spent: r = 0.71, p less than 0.01). Hypoxaemia during sleep was related to waking values of SaO2 and PaCO2 but not to other daytime measures of lung function.

Evaluation of a new asthma questionnaire.

The new International Union Against Tuberculosis (IUAT) bronchial symptoms questionnaire was completed by 827 subjects participating in a prospective study of respiratory symptoms and lung function in aluminum smelter workers. A modified Medical Research Council (MRC) questionnaire was also administered. Bronchial reactivity (BR) was measured in 809 subjects by methacholine challenge using a rapid method. Factor analysis demonstrated sensible clustering of responses to items unique to the new questionnaire such as nocturnal, spontaneous, and postexertional dyspnea, dust-induced dyspnea and tightness, and breathing difficulty. Responses to IUAT questions concerning past asthma, wheeze, chest tightness, morning cough and sputum, and asthma medication agreed well with corresponding items from the MRC questionnaire. Questions concerning asthma, medication, dust-induced, nocturnal, and spontaneous dyspnea, chest tightness, wheeze, nocturnal cough, postexertional dyspnea and breathing difficulty also had high validity against the criterion of concurrently measured bronchial reactivity. It is concluded that the IUAT questionnaire is a valid asthma questionnaire.

Changes in canine left ventricular size and configuration with positive end-expiratory pressure.

Previous studies have shown that left atrial pressure increases when measured relative to pleura! pressure during positive end-expiratory pressure (PEEP). We studied the factors leading to this increase in anesthetized mechanically ventilated dogs. Cardiac output was maintained nearly constant before and during PEEP, and heart rate did not change. Left atrial pressure measured relative to pleura! pressure rose by 2.5 ± 0.5 mm Hg (mean ± SB) during PEEP. Pericardial pressure did not rise more during PEEP than did pleural pressure, indications that there was a true increase in transmural left atrial pressure. With PEEP there was no change in left ventricular diastolic volume as measured by cineangiography and cinefluorography of lead markers implanted in the subendocardium. Left ventricular contractile function, as measured by ejection fraction, also was unchanged. Analysis of the ventricular axes showed an increase in the ratio of septal-lateral to apex-base and anterior-posterior axes with PEEP, indicating a shape change in the left ventricle. Plots of left ventricular volume against left atrial transmural pressure confirmed that there was a shift in the left ventricular pressure-volume curve during PEEP. Thus, the rise in left atrial transmural pressure during PEEP appears to have been caused by a change in left ventricular diastolic pressure-volume properties. We suggest that these changes in the left ventricle may be related to the effects of PEEP on the right ventricle which, in turn, influence the left ventricle. Ore Re* 44: 67S-678, 1979

Bilateral diaphragmatic paralysis with hypercapnic respiratory failure: A physiologic assessment

Bilateral diaphragmatic paralysis was suspected in a patient presenting with hypercapnic respiratory failure who exhibited paradoxic (i.e., inward) abdominal movement on inspiration during tidal breathing in the supine posture; no paradoxic abdominal motion was observed at the bedside with the patient upright. Transdiaphragmatic pressure measurements established the diagnosis of diaphragmatic paralysis, although 20 cm H2O pressure developed across the diaphragm during the latter part of a forced expiration, presumably due to the development of passive tension in the diaphragm as it was stretched near residual volume. Analysis of the relative motion of the rib cage and abdomen during breathing by the use of magnetometers confirmed the presence of abdominal paradox throughout the breathing cycle when the patient was supine, and established that paradoxic motion of the abdomen also occurred when the patient was in the erect posture but only in the latter half of inspiration. Our findings confirm that the use of transdiaphragmatic pressure measurements and magnetometry will help to quantify diaphragmatic function, that passive tension develops in the paralyzed diaphragm near residual volume and should not be confused with active contraction, and that paradoxic motion of the abdomen may be masked from the clinician when the patient is erect.

Supplemental oxygen and quality of sleep in patients with chronic obstructive lung disease.

The hypothesis that supplemental oxygen could improve the quality of sleep was tested in 23 consecutive patients (14 male, nine female; age 42-74 years) with chronic obstructive lung disease (mean (SD) FEV1 0.81 (0.32) litre, FEV1/FVC 37% (12%). Patients breathed compressed air or supplemental oxygen via nasal cannulas on consecutive nights in a randomised, double blind, crossover trial. Quality of sleep was assessed by questionnaire and by electroencephalographic sleep staging. The study had a power of 80% to detect, at the 0.05 level, a 20% improvement in total sleep time. Seventeen patients slept for two nights in the laboratory. Oxygenation during sleep was improved by oxygen administration, but there was no improvement in quality of sleep. There was an acclimatisation effect with better sleep on the second night. Six patients spent an additional acclimatisation night in the laboratory as well as the two study nights. There was no difference in sleep quality between the second and third nights or between the compressed air and the oxygen nights in these patients. Subgroups of patients with an arterial carbon dioxide tension of over 43 mm Hg (5.7 kPa) (n = 12) and arterial oxygen saturation of less than 90% (n = 11) while awake did not show any improvement in quality of sleep on the oxygen night. It is concluded that supplemental oxygen improves nocturnal oxygenation but does not immediately improve the quality of sleep in the laboratory in patients with chronic obstructive lung disease.

Effects of breathing supplemental oxygen before progressive exercise in patients with chronic obstructive lung disease.

A study was carried out to determine whether supplemental oxygen before exercise would improve maximum exercise performance and relieve exertional dyspnoea in 20 patients with chronic obstructive lung disease (mean FEV1 0.79 l; forced vital capacity 2.30 l). Patients performed two progressive treadmill exercise tests to a symptom limited maximum, with at least 30 minutes rest between tests. They received compressed air or supplemental oxygen from nasal prongs for 10 minutes before exercise in a double blind randomised trial with a crossover design. Heart rate and breathlessness score on a visual analogue scale were compared between tests at 75% of the maximum distance walked in the compressed air test. The mean arterial oxygen saturation (SaO2) after oxygen (93%) was significantly higher than after compressed air (91%). There was no significant change, however, in maximum distance walked or maximum heart rate, or in the breathlessness score or heart rate at 75% of maximum distance walked. The study had a power of 93% for detecting an increase of 50 metres in maximum distance walked. There was an order effect, with better performance on the second test; but the magnitude of the difference was small. It is concluded that administration of supplemental oxygen sufficient to raise SaO2 above 90% for 10 minutes before exercise is unlikely to improve maximum exercise performance or breathlessness on exertion in patients with chronic obstructive lung disease.

Interns’ performances with simulated patients at the beginning and the end of the intern year

Objective:To determine whether interns’ performances of technical, preventive, and communication aspects of patient care improve during the intern year.Design:A descriptive study. At the beginning and end of the intern year, interns’ consultations with three simulated (standardized) patients were videotaped and scored according to explicit criteria set by an expert panel. Problems simulated were urinary tract infection, bronchitis, and tension headache.Setting:The casualty outpatient department in a general teaching hospital in New South Wales, Australia.Participants:Twenty-eight interns rotated to the casualty department.Results:Little improvement over the intern year in technical competence or preventive care was observed, even though initial levels of compliance with criteria were quite low for some items. Greater improvement was apparent in the area of communication skills.Conclusions:The results suggest that the internship should be restructured to more adequately teach the skills required for primary care.

Identification of simulated patients by interns in a casualty setting

Summary. Fifty‐four interns agreed to a study in which their clinical performance in an outpatient unit with standardized patients was recorded on videotape. In order to examine whether they could distinguish standardized from real patients, the interns were asked to note any patients who they thought might be simulating their complaints and report these to the researchers at the end of each 2‐day period of study. Thirty‐two of the interns were assessed again at the end of their internship, using the same clinical problems presented by different simulators. The consultations took place in the casualty department of a large urban hospital. At the beginning of the year there were 152 consultations with standardized patients and 328 consultations with appropriate genuine patients. Standardized patients were identified definitely as ‘not genuine’ in only 12 of the 152 consultations (sensitivity 7.8%) whereas 320 of the 328 genuine consultations were accepted by the interns as genuine (specificity 97.8%). When the level of confidence required to distinguish the two groups was reduced from ‘definite’ to ‘probable’, the number of correctly identified simulator consultations increased to 36/152 (27%) but the rate of misclassification of genuine patients also increased from 8 to 37 out of 328 consultations (11%). At the end of the year there were 81 consultations with standardized patients and 149 consultations with genuine patients. Identification rates were only slightly changed. We conclude that simulator identification is not a problem in applying standardized patients to evaluate the quality of care provided in a hospital casualty.

Seasonal variation in non-specific bronchial reactivity: a study of wheat workers with a history of wheat associated asthma.

To investigate seasonal variation in non-specific bronchial reactivity in wheat workers, we carried out histamine inhalation tests in 29 workers (28 of them men) from a small farming community with symptoms of wheat associated asthma before, during and after the 1983-4 Australian wheat harvest season. Four were cigarette smokers, and the age range was 12-54 (mean (SD) 30 (10)) years. Twenty eight subjects were atopic (one positive skinprick test result in tests with 10 common antigens), 60% reacting to house dust mite and all to at least one of eight wheat antigens. Baseline spirometry gave normal results (mean FVC1 90% (SD 8%) predicted; FVC 91% (7%) predicted). Bronchial reactivity was tested by the method of Yan et al. The cumulative doses of histamine acid phosphate (up to 3.91 mumol) that caused a fall of 20% from baseline in FEV1 was determined (PD20) and expressed as the geometric mean. In the low exposure season, May 1983, nine subjects had a PD20 (mean 1.2, range 0.3-3.9 mumol). The number rose to 19 in the summer harvest season, December 1983 (mean 0.8, range 0.07-3.9 mumol) and returned to nine in the subsequent winter, July 1984 (mean 1.8, range 0.4-3.9 mumol). The change in the number of subjects with a PD20 was significant (p less than 0.01). Four additional subjects probably had increased bronchial reactivity in the harvest season: in two the post-saline FEV1 was too unstable to give them histamine challenge and in two the challenge was inadvertently discontinued prematurely. Baseline FEV1 and FVC fell by 8% between the first and second studies (p less than 0.001); values were intermediate in the third study (FEV1 3.74, 3.44, and 3.57; FVC 4.66, 4.28, and 4.41 litres respectively). Linear modelling analysis of log PD20, season, FEV1, FVC, age, seasonality of asthma symptoms and skin test data indicated that the harvest season was the only significant determinant of variation in log PD20. It is concluded that in these wheat workers there is a seasonal variation in bronchial reactivity that may reflect a response to allergens associated with grain.