Patients' estimates of their sleep times: reliability and impact on diagnosis of obstructive sleep apnoea.

BACKGROUND: Home polysomnography (PSG) is an alternative method for diagnosis of obstructive sleep apnoea (OSA). Some types 3 and 4 PSG do not monitor sleep and so rely on patients' estimation of total sleep time (TST). AIM: To compare patients' subjective sleep duration estimation with objective measures in patients who underwent type 2 PSG for probable OSA. METHODS: A prospective clinical audit of 536 consecutive patients of one of the authors between 2006 and 2013. A standard questionnaire was completed by the patients the morning after the home PSG to record the time of lights being turned off and estimated time of sleep onset and offset. PSG was scored based on the guidelines of the American Academy of Sleep Medicine. RESULTS: Median estimated sleep latency (SL) was 20 min compared with 10 min for measured SL (P < 0.0001). There was also a significant difference between the estimated and measured sleep offset time (median difference = -1 min, P = 0.01). Estimated TST was significantly shorter than the measured TST (median difference = -18.5 min, P = 0.002). No factors have been identified to affect patients' accuracy of sleep perception. Only 2% of patients had a change in their diagnosis of OSA based on calculated apnoea-hypopnoea index. CONCLUSIONS: Overall estimated TST in the patients with probable OSA was significantly shorter than measured with significant individual variability. Collectively, inaccurate sleep time estimation had not resulted in significant difference in the diagnosis of OSA.

Routine use of humidification with nasal continuous positive airway pressure.

BACKGROUND: Heated humidification can reduce nasal symptoms caused by continuous positive airway pressure (CPAP) treatment, but its routine use has not been studied over the medium term in a randomized controlled trial. The aim of this study is to determine if heated humidification would reduce nasal symptoms and improve adherence with CPAP treatment in all patients with sleep apnoea irrespective of whether they had nasal symptoms initially. METHODS: A randomized, parallel group design. Patients were treated for 3 months with a Fisher & Paykel HC201 pump with built-in heated humidification, or with the heater disabled and without water. Adherence was measured with a timer built into the pumps. Nasal symptoms were measured with a 10-cm visual analogue scale. RESULTS: There were 25 in the humidification group and 29 in the non-humidification group. After 12 weeks mean (standard deviation) adherence with CPAP was 4.7 (2.4) and 4.5 (2.2) hours per night respectively. Nasal symptoms that were reduced were nose blocked* 6 (12), 18 (26); sneezing* 4 (8), 15 (25); dry nose* 8 (12), 24 (33); stuffy nose* 7 (14), 22(31); dry mouth* 13 (18), 33(36); and runny nose* 6 (17), 14 (29). Parameters marked with an asterisk '*' had P < 0.05 with t-tests. CONCLUSION: The routine use of heated humidification with CPAP in all patients with sleep apnoea reduced nasal symptoms, but did not improve adherence.

Cardiac and respiratory activity at arousal from sleep under controlled ventilation conditions.

Arousal from sleep is associated with elevated cardiac and respiratory activity. It is unclear whether this occurs because of homeostatic mechanisms or a reflex activation response associated with arousal. Cardiorespiratory activity was measured during spontaneous arousals from sleep in subjects breathing passively on a ventilator. Under such conditions, homeostatic mechanisms are eliminated. Ventilation, end-tidal PCO2, mask pressure, diaphragmatic electromyograph, heart rate, and blood pressure were measured in four normal subjects under two conditions: assisted ventilation and a normal ventilation control condition. In the control condition, there was a normal, sleep-related fall in ventilation and rise in end-tidal PCO2. Subsequently, at an arousal, there was an increase in respiratory and cardiac activity. In the ventilator condition, a vigorous cardiorespiratory response to a spontaneous arousal from sleep remained. These results indicate that sleep-related respiratory stimuli are not necessary for the occurrence of elevated cardiorespiratory activity at an arousal from sleep and are consistent with the hypothesis that such activity is at least in part due to a reflex activation response.

Effect of age on sleep onset-related changes in respiratory pump and upper airway muscle function.

In normal young men, there is an abrupt fall in ventilation (VE), a rise in upper airway resistance (UAR), and falls in the activities of the diaphragm (Di), intercostals (IC), genioglossus (GG), and tensor palatini (TP) at sleep onset. On waking, there is an abrupt increase in VE and fall in UAR and an increase in the activities of Di, IC, GG, and TP. The aim of this study was to determine whether these changes are age dependent. Nine men aged 20 to 25 yr were compared with nine men aged 42 to 67 yr. Airflow, UAR, Di, and IC surface electromyograms (EMGs) and the intramuscular EMGs of GG and TP were recorded. It was found that the falls in IC, GG, and TP at the transition from alpha to theta electroencephalogram (EEG) activity were significantly greater in the older than in the younger men (P < 0.05) and that the fall in Di was also greater, although this was only marginally significant (P = 0.15). The rise in GG at theta-to-alpha transitions was also greater in the older than in the younger men, and there was a trend for TP to be higher.

Flow-volume curve changes in patients with obstructive sleep apnoea and brief upper airway dysfunction.

OBJECTIVE: Patients with obstructive sleep apnoea (OSA) and those with brief upper airway dysfunction (BUAD) have been reported to have abnormalities of maximal flow-volume curves. This study was designed to assess the ability of flow-volume curves to predict the presence of OSA or BUAD. METHODOLOGY: Four maximal flow-volume manoeuvres performed by 33 OSA patients and 16 BUAD patients were compared with those of 36 normal subjects. Flow-volume indices, their variability, saw-toothing in the curve and an algorithm based on the flow ratios and shape of the curves were assessed. RESULTS: When the confounding factors, body mass index (BMI), age, gender and smoking status were taken into account, there was no significant difference in a variety of indices derived from the flow-volume curves between OSA and normal subjects. No BUAD patient had normal flow-volume curves as determined with the algorithm. After BMI, age, gender and smoking status were accounted for, decreased forced expiratory volume in 1 s (FEV1), and increased variability of peak expiratory flow (PEF)/peak inspiratory flow (PIF) and FEV1/PEF remained significantly associated with BUAD. CONCLUSIONS: These findings suggest that flow-volume curve indices have no value in predicting OSA. Some abnormalities are found in patients with BUAD; a normal flow-volume curve makes the diagnosis of BUAD unlikely.

Upper airway function and dysfunction in respiration.

1. The upper airway not only provides a passage for air to be breathed in and out of the lungs, but it also heats, humidifies and filters the air and is involved in cough, swallowing and speech. 2. The complex muscle structure of the upper airway that produces speech and swallowing in humans also modulates respiratory airflow throughout the respiratory cycle, but is vulnerable to functional problems that may compromise respiration. 3. Even in normals, there is some collapse of the upper airway and increased upper airway resistance during sleep. 4. A substantial proportion of people suffer from obstructive sleep apnoea, in which the collapse of the upper airway is so great that respiration is compromised to the extent that arousal from sleep is required to restore adequate ventilation; the resulting disturbed sleep and hypoxia produce daytime sleepiness and neuropsychological and cardiorespiratory morbidity. 5. Functional abnormalities of the larynx can also occur, including prolonged inspiratory laryngeal dysfunction, brief upper airway dysfunction and expiratory laryngeal dysfunction or factitious asthma.

Activity of respiratory pump and upper airway muscles during sleep onset.

Ventilation decreases at sleep onset. This change is initiated abruptly at alpha-theta electroencephalographic transitions. The aim of this study was to determine the contributions of reduced activity in respiratory pump muscles and upper airway dilator muscles to this change. Surface electromyograms over the diaphragm (Di) and intercostal muscles and fine-wire intramuscular electrodes in genioglossus (GG) and tensor palatini (TP) muscles were recorded in nine healthy young men. It was shown that phasic Di and both phasic and tonic TP activities were lower during theta than during alpha activity. Breath-by-breath analysis of the changes at alpha-theta transitions during the sleep-onset period showed a number of changes. At alpha-theta transitions, phasic activity of Di, intercostal, and GG muscles fell and rose again, and phasic and tonic activities of TP fell and remained at low levels during theta. With a state transition from theta to alpha, the phasic and tonic activities of the Di, GG, and TP increased dramatically. It is now clear that the fall in ventilation that occurs with sleep is related to a fall in activities of both upper airway dilator muscles and respiratory pump muscles.

The prevalence of obstructive sleep apnea in hypertensives.

This study was designed to measure the prevalence of obstructive sleep apnea in untreated and treated hypertensive patients by comparing them with normotensive subjects, taking into account the possible confounding variables body mass index, age, sex, and alcohol consumption. Subjects with no known sleep disorders were recruited, had full polysomnography, and had their blood pressure assessed with a 24-h ambulatory monitor. Subjects with a mean 24-h blood pressure greater than 140/90, and receiving no treatment for, or with no history of, hypertension were classified as untreated hypertensives; those receiving antihypertension medication were classified as treated hypertensives; those with a mean 24-h blood pressure less than 140/90 and no history of hypertension were classified as normotensives. Thirty-eight percent of the 34 untreated and 38% of the 34 treated hypertensives, and 4% of the 25 normotensives had apnea-hypopnea indexes greater than 5. Logistic regression analysis showed that body mass index (p = 0.001), age (p = 0.07), sex (p = 0.07), treated hypertension (p = 0.05), and untreated hypertension (p = 0.06) were associated with the presence of sleep apnea, but that alcohol consumption (p = 0.82) was not. It is concluded that there is a relationship between sleep apnea and hypertension that, although partially explained by the confounding variables body mass index, age, and sex, persists when these are allowed for.

Bronchogenic cyst: a cause of pulmonary artery obstruction and breathlessness.

A young woman presenting with breathlessness and a normal chest roentgenogram was found to have unilateral absent lung perfusion on an isotope scan. This was due to a bronchogenic cyst obstructing the right pulmonary artery. This is a rare cause of unilateral absence of lung perfusion and an unusual mode of presentation of a bronchogenic cyst.

Covert self poisoning with brodifacoum, a 'superwarfarin'.

The clinical course of a patient poisoned with the 'superwarfarin' brodifacoum and a method for estimation of plasma levels is described. It was characterised by prolonged depression of Vitamin K-dependent clotting factors poorly responsive to Vitamin K administration.