The importance of the balloon reservoir volume of a CPAP system in reducing the work of breathing

We have previously reported, that the work of breathing in spontaneously breathing patients on CPAP could be significantly reduced by increasing the volume of the balloon reservoir in the circuit of a CPAP system from 3 to 23 l. We now report a study designed to determine the optimum balloon reservoir volume for the minimization of the work of breathing. Twenty intubated, spontaneously breathing patients were connected to a CPAP system with interchangeable balloon reservoirs. In each patient the work of breathing was measured for reservoir volumes of 3, 6, 12, 18, and 24 l attached in random order, while the positive airway pressure was held constant at 10 cm H₂O. The balloons were constructed of the same material and had similar compliance. Rebreathing was prevented with use of one-way valves. Significant (p<0.001) decreases in the work of breathing were found on increasing reservoir volumes from 3 to 6, 6 to 12, and 12 to 18 l. A less significant (p<0.01) decrease in the work of breathing was found between reservoirs of 18 and 24 l. Rebreathing did not occur with significantly (p<0.001) lower flow rates when large reservoirs were used. We conclude that a balloon reservoir of 18 l represents the best compromise between reduction in the work of breathing, utilization of low source flow, and convenience of clinical use.     

Noninvasive continuous positive airway pressure in elderly cardiogenic pulmonary edema patients

Objective To compare the physiological effects and the clinical efficacy of continuous positive airway pressure (CPAP) vs standard medical treatment in elderly patients (75 years) with acute hypoxemic respiratory failure related to cardiogenic pulmonary edema.Design A prospective, randomized, concealed, and unblinded study of 89 consecutive patients who were admitted to the emergency departments of one general, and three teaching, hospitals.Intervention Patients were randomly assigned to receive standard medical treatment alone (n=46) or standard medical treatment plus CPAP (n=43).Measurements Improvement in PaO₂/FIO₂ ratio, complications, length of hospital stay, early 48-h and overall mortality, compared between the CPAP and standard treatment groups.Results Study groups were comparable with regard to baseline physiological and clinical characteristics (age, sex ratio, autonomy, medical history, cause of pulmonary edema). Within 1 h, noninvasive continuous positive airway pressure led to decreased respiratory rate (respiratory rate, 27±7 vs 35±6 breaths/min; p=0.009), and improved oxygenation (PaO₂/F_IO₂, 306±104 vs 157±71; p=0.004) compared with baseline, whereas no differences were observed within the standard treatment group. Severe complications occurred in 17 patients in the standard treatment group, vs 4 patients in the noninvasive continuous positive airway pressure group (p=0.002). Early 48-h mortality was 7% in the noninvasive continuous positive airway pressure group, compared with 24% in the standard treatment group (p=0.017); however, no sustained benefits were observed during the overall hospital stay.Conclusion Noninvasive continuous positive airway pressure promotes early clinical improvement in elderly patients attending emergency departments for a severe pulmonary edema, but only reduces early 48-h mortality.     

Identification and Treatment of Sleep Apnea in Patients With Chronic Headache

This study investigates the relationship between nocturnal or morning headache and obstructive sleep apnea syndrome (sleep apnea). It is not known if headache of any type is more common in patients with sleep apnea than in other patients, but morning headache is a symptom of sleep apnea. A method is needed for identifying patients with chronic headache who might benefit from evaluation and treatment of sleep apnea. We performed a retrospective assessment of frequency of morning headache in patients grouped according to final diagnosis: sleep apnea (n=72), periodic leg movements of sleep (n=28), and psychophysiologic insomnia (n=42). Prospective overnight sleep studies were obtained in a different group of 19 patients who presented for evaluation of headache. We selected certain patient characteristics as possibly indicative of sleep apnea-related headache. The retrospective study showed that 24% of patients with sleep apnea had frequent morning headache, which was not different from the other groups. In the separate group of 19 patients with chronic headache and suspected sleep disorder, 17 had sleep apnea. Nasal continuous positive airway pressure was prescribed to 14 patients. Marked improvement in headache occurred and persisted in 4 patients and moderate improvement in 3. Responders to therapy were more likely to have vascular headaches than mixed or tension headaches, more severe sleep apnea, and a nocturnal or morning timing to their headaches. However, there was large overlap in severity of sleep apnea and likelihood of response. We conclude that morning headache is not more common in sleep apnea than in other sleep disorders. However, over 30% of patients with chronic headache and other symptoms of sleep apnea have significant improvement in headache after treatment of sleep apnea.     

预见性护理在OSAHS患者CPAP治疗中的应用价值分析

目的分析预见性护理在阻塞性睡眠呼吸暂停低通气综合征(OSAHS)患者持续气道正压通气(CPAP)治疗中的应用价值。方法将90例行CPAP治疗的OSAHS患者随机分为观察组和对照组各45例。观察组采用预见性护理,对照组采用常规护理。出院后1周随访,对比两组患者的治疗依从性及护理满意度。结果观察组的治疗依从性为84.44%,明显高于对照组的62.22%(P<0.05)。观察组的护理满意度为97.78%,明显高于对照组的84.44%(P<0.05)。结论在OSAHS患者CPAP治疗中实施预见性护理可明显提升患者的治疗依从性和护理满意度,值得临床推广。     

Cognitive effects of treating obstructive sleep apnea in Alzheimer's disease: a randomized controlled study

OBJECTIVES: To examine whether treatment of obstructive sleep apnea (OSA) with continuous positive airway pressure (CPAP) in patients with Alzheimer's disease (AD) results in better cognitive function. DESIGN: Randomized double‐blind placebo‐controlled trial. Participants were randomized to therapeutic CPAP for 6 weeks or placebo CPAP for 3 weeks followed by therapeutic CPAP for 3 weeks. SETTING: General clinical research center. PARTICIPANTS: Fifty‐two men and women with mild to moderate AD and OSA. INTERVENTION: CPAP. MEASUREMENTS: A complete neuropsychological test battery was administered before treatment and at 3 and at 6 weeks. RESULTS: A comparison of subjects randomized to 3 weeks of therapeutic versus placebo CPAP suggested no significant improvements in cognition. A comparison of pre‐ and posttreatment neuropsychological test scores after 3 weeks of therapeutic CPAP in both groups showed a significant improvement in cognition. The study was underpowered to make definitive statements about improvements within specific cognitive constructs, although exploratory post hoc examination of change scores for individual tests suggested improvements in episodic verbal learning and memory and some aspects of executive functioning such as cognitive flexibility and mental processing speed. CONCLUSION: OSA may aggravate cognitive dysfunction in dementia and thus may be a reversible cause of cognitive loss in patients with AD. OSA treatment seems to improve some cognitive functioning. Clinicians who care for patients with AD should consider implementing CPAP treatment when OSA is present.     

High flow nasal oxygen generates positive airway pressure in adult volunteers

INTRODUCTION: The use of non-invasive ventilation (NIV) as an alternative to intubation in respiratory failure is associated with better outcomes in certain conditions. NIV is often poorly tolerated by patients hence precipitating the need for invasive ventilation. High flow nasal (HFN) oxygen delivery is a potential alternative to NIV as it delivers air and oxygen via a humidified circuit at flows greater than those traditionally used with a nasal interface. BODY: Studies of paediatric patient using high flow nasal oxygen therapy have been shown to have similar efficacy as nasal continuous positive airway pressure (CPAP). Although the degree of positive pressure and the effect of different flow rates on positive pressure generation have not been well defined or studied in the adult intensive care population. St. Vincent's Health Human Research and Ethics Committee granted approval to this study and also awarded a $3000 grant. Volunteers were fitted with the Fisher & Paykel high flow nasal interface (RT034) and pharyngeal pressures were recorded with flows from 0 to 60L/min. Expiratory pressures with the mouth closed were higher than those with the mouth open and this was statistically significant (<0.001). Expiratory pressures were higher with the mouth closed and were statistically different (p<0.001). EPPs were higher amongst female subjects compared to male subjects and were statistically different between genders for both open (p<0.05) and closed (p<0.001) measurements. CONCLUSION: This study has demonstrated that high flow nasal therapy is associated with the generation of significant positive airway pressure in volunteers. In conclusion there is a degree of CPAP generated with the HFN therapy, which is flow dependent and also dependent on whether the person is breathing with mouth open or closed.     

CPAP治疗新生儿急性呼吸衰竭38例体会及建议

目的：通过使用CPAP治疗38例急性呼吸衰竭的新生儿,观察临床的疗效并提出合理建议,从而提高患儿的抢救成功率。方法：对38例确诊患有呼吸衰竭的新生儿应用CPAP治疗后,观察PaO2、PaCO2、SaO2及CPAP参数的变化及治疗效果。结果：31例呼吸衰竭的新生儿应用CPAP治疗后,监测PaO2、PaCO2、SaO2的值在正常范围,差异有统计学意义（P〈0.01）。结论：CPAP治疗新生儿急性呼吸衰竭疗效显著,值得在临床上推广应用。     

nCPAP治疗重度OSAS合并高血压患者血浆尾加压素Ⅱ的研究

目的探讨经鼻持续气道正压通气（nCPAP）治疗重度阻塞性睡眠呼吸暂停综合征（OSAS）合并高血压病患者尾加压素（U—II）在其过程中病理生理的作用及临床意义。方法采用放射免疫法分析30例患者经nCPAP治疗前后U—II的水平;采用夜间多导睡眠（PSG）监测患者治疗前后SaO2及夜间7h血压水平。结果治疗前、后患者血浆U—II的水平及Sa02分别为（9．01±1．0）pg／ml、（7．2±0．8）pg/ml,（51．2±3．64）％、（85．3±3．6）％,均有统计学意义（P〈0．005）;治疗前、后夜间7h平均收缩压及舒张压分别为（156．67±9．56）mmHg、（137．57±15．309）mmHg、（105．50±4．89）mmHg、（83．45±14．9）mmHg,均有统计学意义（P〈0．001）。结论U—II的增高可能是重度阻塞性睡眠呼吸暂停综合征合并高血压病患者疾病发生、发展的重要因素,通过nCPAP治疗后可使患者血浆中血浆U—II的水平明显降低,氧饱和度改善,具有明显的临床疗效。     

The Time of Day Sleepiness Scale to assess differential levels of sleepiness across the day

Objective

The study evaluated the Time of Day Sleepiness Scale (ToDSS) to determine subjective estimates of sleepiness in the morning, afternoon, and evening. Scores on the ToDSS were compared to the Epworth Sleepiness Scale (ESS). The ToDSS was evaluated on three cohorts of patients at a sleep medicine clinic.

Method

The items of the ToDSS are modified from the ESS to enable subjective assessment in the morning (before noon), afternoon (noon to 1800 h), and evening (after 1800 h). The scale takes about 5 min to complete. For each item, patients provide an estimate of their level of sleepiness in three separate columns, each indicating the time of day (morning, afternoon, and evening).

Results

Each ToDSS score evidenced a one factor structure. The ToDSS enabled the assessment of differential levels of sleepiness across the day among several cohorts, with scores increasing in the afternoon and evening. The ESS and each score of the ToDSS demonstrated high correlations. Lower subjective estimates of sleepiness were documented after treatment with continuous positive airway pressure.

Conclusions

The ToDSS was shown to have comparable psychometric features to the ESS and provided perceived sleepiness levels across the day in an efficient and cost-effective manner. It also enabled characterization of treatment response among a cohort of patients with obstructive sleep apnea.