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At least 19 recordsLinked to original sources
PubMed1989

Inspiratory work of breathing on flow-by and demand-flow continuous positive airway pressure.

Continuous positive airway pressure (CPAP) breathing can be delivered using the demand-flow (DF) or continuous-flow (CF) system. A modified CF system, the flow-by (FB) system, operates with preset base-flow (BF) values between 5 and 20 L/min. The DF depends on changes in pressure for opening the pneumatic valve of the system (pressure sensitivity). In contrast, the FB depends on changes in flow (flow sensitivity). In six healthy male subjects, we determined the mechanical inspiratory work of breathing (WI, J/L) and the inspiratory work rate (J/min) on the DF and the FB systems at a BF of 5 and 20 L/min, at CPAP levels of 0, 5, and 10 cm H2O. In comparison to DF, on the FB system both WI and inspiratory work rate were significantly less at a CPAP of 10 cm H2O (p less than .01). This was most likely due to the smaller drop in airway pressure at the onset of inspiration with the FB system. Varying the BF values in the FB system had no effect on WI or inspiratory work rate.

Adult↗
PubMed1987

Central sleep apnea reversed by continuous positive airway pressure.

Continuous positive airway pressure (CPAP) is an accepted and highly effective method used in the treatment of obstructive sleep apnea (OSA). We have explored the potential utility of CPAP in a patient with sleep apnea without a major contribution of airway obstruction as measured by the usual criteria. The patient showed dramatic clinical and laboratory improvement in central apnea when treated with CPAP. A low level of CPAP (7.5 cm H2O) resulted in the reduction of central apneas from 281 to 32 per night with no significant change in obstructive apneas, which increased from 43 to 59 per night. On a separate night, a higher level of CPAP (12.5 cm H2O) resulted in virtually complete removal of all apneas. Measurement of pharyngeal properties revealed pharyngeal cross-sectional area in the low normal range, but increased pharyngeal compliance. This case illustrates that pharyngeal abnormalities may be present in patients with central sleep apnea, and CPAP may be beneficial in the treatment of this disorder. Although the exact mechanism of action of CPAP in this disorder is unclear, we propose several possibilities that may account for the beneficial effect of CPAP in this patient.

Adult↗
PubMed2006

Pressure-relief continuous positive airway pressure vs constant continuous positive airway pressure: a comparison of efficacy and compliance.

OBJECTIVES: To compare polysomnographic data and compliance in sleep apnea patients receiving continuous positive airway pressure (CPAP) and pressure-relief CPAP (PRCPAP) [C-flex; Respironics; Murrysville, PA] as first treatment in the sleep laboratory and subsequently at home. DESIGN: A prospective, randomized, crossover design was used in the sleep laboratory, and a prospective randomized design was used at home. PATIENTS: Data were collected from 52 sleep apnea patients for whom CPAP was used for the first time. INTERVENTIONS: Treatment with constant CPAP and PRCPAP. MEASUREMENTS AND RESULTS: Patients with a first-time diagnosis of obstructive sleep apnea syndrome (OSAS) underwent conventional CPAP titration. Thereafter, polysomnography was performed at the titrated pressure using both the fixed CPAP pressure mode and the PRCPAP mode in a randomized crossover approach. The patients were then discharged home for 7 weeks of treatment with the last-applied treatment mode, and compliance data were established at the end of that time. The average apnea-hypopnea index was 53.3/h in the "diagnostic night," 5.8/h with CPAP, and 7.0/h with PRCPAP. The native arousal index was 35.2/h, 12.6/h with CPAP, and 12.9/h with PRCPAP (not significant [NS]). The central apnea index was 0.7/h with CPAP and 1.2/h with PRCPAP (p < 0.05). Compliance after 7 weeks was, on average, 9.4 min longer with PRCPAP than with CPAP (NS). Evaluation of a 13-item questionnaire showed scores of 16.4 for PRCPAP and 18.1 for constant CPAP (NS) [the fewer the complaints, the lower the score]. With regard to oral dryness, the score with PRCPAP (1.4) was significantly lower than with constant CPAP (1.9) [p < 0.05]. This difference was no longer detectable after 7 weeks. CONCLUSION: In terms of the effectiveness in treating obstructive sleep apnea, PRCPAP and constant CPAP are comparable. During the first night of treatment, patients receiving PRCPAP had less dryness of mouth; over a period of 7 weeks, this difference disappeared. Nightly use of the device was comparable in both groups. PRCPAP is therefore a new ventilation mode that enables effective treatment of OSAS patients. Further studies should be done to investigate the effects of expiratory pressure lowering in low-compliance patients and patients requiring CPAP > 9 cm H(2)O or experiencing dry mouth with CPAP.

Adult↗
PubMed1999

Effect of continuous positive airway pressure vs placebo continuous positive airway pressure on sleep quality in obstructive sleep apnea.

STUDY OBJECTIVES: Continuous positive airway pressure (CPAP) therapy has become the treatment of choice for obstructive sleep apnea (OSA). However, the efficacy of CPAP therapy has not been evaluated against a suitable control. We investigated the effectiveness of CPAP therapy in improving sleep quality in patients with OSA. We hypothesized that CPAP improves sleep quality. PATIENTS: Forty-eight CPAP-naive OSA patients were evaluated. None were receiving antihypertensive medications, and none had major medical illnesses. DESIGN: Patients were randomized to receive either CPAP or placebo CPAP (CPAP at an ineffective pressure) for 7 days in a double-blind fashion. Forty-one patients completed the protocol. Sleep quality variables, arousals, sleep arterial oxygen saturation (SaO(2)), and respiratory disturbance index (RDI) were assessed at baseline, after 1 day of treatment, and after 7 days of treatment. Repeated measures analysis of variance was used to evaluate the effects of treatment, time, and the interaction of the two. RESULTS: As expected, CPAP lowered RDI and number of arousals, and increased SaO(2) over time (p = 0.001). Contrary to expectations, both CPAP and placebo CPAP had comparable effects on sleep quality as assessed by sleep architecture, sleep efficiency, total sleep time, and wake after sleep onset time. CONCLUSIONS: This study confirms the effectiveness of CPAP in lowering the number of arousals and the RDI, and in raising SaO(2). However, our data suggest that short-term CPAP is no different than placebo in improving sleep architecture. Further evaluation of the effectiveness of CPAP using a suitable placebo CPAP in prospective randomized studies is needed

Adult↗
PubMed2004

Arbitrary-pressure continuous positive airway pressure for obstructive sleep apnea syndrome.

Current resources are inadequate to meet the demand for polysomnography, resulting in long waiting lists. This study aimed to evaluate the role of arbitrary-pressure continuous positive airway pressure (CPAP) as a method to reduce delays in commencing treatment. The study was of an open, randomized, parallel design. Ninety-one subjects with obstructive sleep apnea syndrome were randomized to either arbitrary-pressure CPAP based on body mass index before treatment polysomnography or to CPAP at settings determined by polysomnography. Both interventions resulted in similar improvements in clinical outcomes as determined by Epworth Sleepiness Score, Short Form-36 Quality of Life questionnaire, objective compliance, and subjective attitudes to treatment. There was higher sleep efficiency at treatment polysomnography in the group commenced at arbitrary pressure (81.8 +/- 10.1% [mean +/- SD] compared with 72.2 +/- 18.0%, p = 0.01). Subjects unable to tolerate CPAP were identified by the use of arbitrary pressure, leading to a reduction in the proportion of "wasted" treatment polysomnograms (studies performed in subjects not persisting with treatment) relative to commencing therapy after treatment polysomnography (3 of 39 compared with 12 of 35, p = 0.01). This approach to initiating treatment with CPAP appears feasible when there are long waiting lists for polysomnography.

Continuous Positive Airway Pressure↗
PubMed1985

Inspiratory work and airway pressure with continuous positive airway pressure delivery systems.

To determine work-of breathing with continuous positive airway pressure (CPAP) delivery systems, we used a lung model to simulate spontaneous breathing. "Additional work" during tidal breathing was derived by comparing change in airway pressure with change in tidal volume. Seven demand-flow CPAP delivery systems were compared with one continuous-flow, 5-L reservoir-bag system (flow of 60 L/min to maintain positive airway pressure). It was concluded that demand-flow CPAP delivery systems vary widely in the amount of additional work required of a patient. When a lung model is used, some demand-flow systems perform as well as, or better than, a continuous-flow reservoir-bag system.

Forced Expiratory Flow Rates↗
PubMed2001

Heart rate variability and hemodynamic alterations in canines with normal cardiac function during exposure to pressure support, continuous positive airway pressure, and a combination of pressure support and continuous positive airway pressure.

Variations in intrathoracic pressure generated by different ventilator weaning modes may significantly affect intrathoracic hemodynamics and cardiovascular stability. Although several investigators have attributed cardiovascular alterations during ventilator weaning to augmented sympathetic tone, there is limited investigation of changes in autonomic tone during ventilator weaning. Heart rate variability (HRV), the analysis of beat-to-beat changes in heart rate, is a noninvasive indicator of autonomic tone that might be useful in the identification of patients who are at risk for weaning difficulty due to underlying cardiac dysfunction. The authors describe HRV and hemodynamics in response to 3 ventilatory conditions: pressure support (PS) 10 cmH2O, continuous positive airway pressure (CPAP) 10 cmH2O, and a combination of PS 10 cmH2O and CPAP 10 cmH2O (PS + CPAP) in a group of canines with normal ventricular function. Six canines were studied in the laboratory. Continuous 3-lead electrocardiographic data were collected during baseline (controlled mechanical ventilation) and following transition to each of the ventilatory conditions (PS, CPAP, PS + CPAP) for analysis of HRV. HRV was evaluated using power spectral analysis to define the power under the curve in a very low frequency range (0.0033 to < 0.04 Hz, sympathetic tone), a low frequency range (0.04 to < 0.15 Hz, primarily sympathetic tone), and a high frequency range (0.15 to < 0.40 Hz, parasympathetic tone). A thermodilution pulmonary artery catheter measured cardiac output and right ventricular end-diastolic volume to describe global hemodynamics. There were significant increases in very low frequency power (sympathetic tone) with a concomitant significant reduction in high-frequency power (parasympathetic tone) with exposure to PS + CPAP. These alterations in HRV were associated with significantly increased heart rate and reduced right ventricular end-diastolic volume. Although there was a small but significant increase in cardiac output with exposure to PS, HRV was unchanged. These data indicate that there was a relative shift in autonomic balance to increased sympathetic and decreased parasympathetic tone with exposure to PS + CPAP. The increase in intrathoracic pressure reduced right ventricular end-diastolic volume (preload). This hemodynamic alteration generated a change in autonomic tone, so that cardiac output could be maintained. Individuals with autonomic and/or cardiovascular dysfunction may not be capable of this type of response and may fail to successfully wean from mechanical ventilation.

Analysis of Variance↗
PubMed1998

Failure of CPAP therapy in obstructive sleep apnoea syndrome: predictive factors and treatment with bilevel-positive airway pressure.

Continuous positive airway pressure (CPAP) is the most widely used therapy for obstructive sleep apnoea (OSA). Despite its general efficacy, oxygen desaturation due to hypoventilation persists in some patients. The present study analysed the factors which are associated with this primary failure and, moreover, examined the effect of a bilevel positive airway pressure (BiPAP) trial. In a 15-month period, 13 patients with OSA (Group A) failed to respond to initial CPAP therapy defined by a remaining apnoea/hypopnoea index (AHI) of > or = 5 or a mean nocturnal SaO2 < 90%. These patients were compared to an age- and AHI-matched control group (Group B) successfully treated by CPAP. A logistic regression analysis was performed to identify factors which are associated with initial failure to CPAP. Patients of the CPAP-failure group were treated with nasal BiPAP in the control mode. These patients were significantly more obese than patients of the control group (mean body mass index 44.2 +/- 7.7 vs 31.2 +/- 6.3 kg m-2; P < 0.001). PaO2 at rest (P < 0.001) and at exercise (P < 0.005) was significantly lower in Group A patients. PaCO2 at rest (P < 0.001) was significantly higher in Group A patients and changed for the worse during exercise, whereas it improved in the control group. Group A patients spent significantly (P < 0.0001) more time with oxygen saturation < 90%. The percentage of time spent at < 90% of SaO2 was the only factor which was independently associated with the initial failure of CPAP (OR 1.13; 95% CI 1.0-1.2). After 3 months of treatment with BiPAP, the patients' blood gas values while awake improved significantly (P < 0.05) for PaO2 as well as for PaCO2. In conclusion, patients with OSA resistant to initial CPAP are morbidly obese with impaired awake blood gas values. The percentage of time spent at < 90% of nocturnal SaO2 is independently associated with initial failure of CPAP. BiPAP in the control mode is adequate for nocturnal ventilation, and improves awake blood gas values.

Adult↗
PubMed2004

The effects of tracheostomy cuff deflation during continuous positive airway pressure.

Continuous flow positive pressure devices bridge the gap between mechanical and unsupported ventilation in patients recovering from critical illness. At this point, patients are often fully awake, yet the inflated tracheostomy cuff prevents them from speaking or swallowing. The aim of this study was to investigate the effects of cuff deflation. After ethics committee approval and informed consent, we recorded airway pressures with catheters placed 3 cm beyond the distal tracheostomy tip, respiratory rate, heart rate and peripheral oxygen saturation with continuous positive airway pressures set at 5, 7.5 and 10 cmH(2)O with the cuff inflated and deflated. Sixteen patients completed the study. There were small falls in end expiratory pressure on cuff deflation. The median (interquartile range) pressure drop with set airway pressure of 5 cmH(2)O was 0.25 (0-1.4) mmHg, which increased to 1 (0-3) mmHg at 7.5 cmH(2)O and 1.5 (0-4) mmHg at 10 cmH(2)O. These changes were not clinically significant and cardiopulmonary parameters remained stable. All patients were able to vocalise following cuff deflation. Twelve patients passed a blue dye swallow screen within a day of tolerating cuff deflation. These results suggest that pressures fall slightly following cuff deflation but this is associated with respiratory stability and may allow patients to talk and swallow.

Aged↗
PubMed2004

Surfactant and physiologic responses of preterm lambs to continuous positive airway pressure.

Although continuous positive airway pressure (CPAP) is used frequently for preterm infants, the relationships between the amount of surfactant and lung physiologic and injury responses to CPAP are unknown. Therefore, saturated phosphatidylcholine (Sat PC) was measured to quantify the surfactant necessary for preterm lambs to breathe successfully on a CPAP of 5 cm H(2)O (CPAP 5). Five of 21 lambs delivered at 130-136 days gestation failed to keep PCO(2) below 100 mm Hg by 2 hours. The lambs that failed had less than 1.9 micromol/kg Sat PC in bronchoalveolar fluid (approximately 3% the pool size at term), less surfactant secretion, and less large aggregate surfactant. Physiologic responses of other 132-day preterm lambs after 2 or 6 hours of CPAP 5, 8 cm H(2)O CPAP (CPAP 8), or mechanical ventilation were then characterized. At 6 hours, oxygenation and lung gas volumes were higher with CPAP 8 relative to the other groups and VE was decreased with CPAP 8 relative to CPAP 5. Lung dry/wet ratios were greater for the CPAP groups than for the mechanical ventilation group. A small amount of endogenous Sat PC is required for preterm lambs to breathe successfully with CPAP. CPAP 8 improves early newborn respiratory transition relative to CPAP 5.

Age Factors↗
PubMed2003

Should flow-volume loop be monitored in sleep apnea patients treated with continuous positive airway pressure?

Nasal continuous positive airway pressure (nCPAP) has been widely established in the treatment of obstructive sleep apnea syndrome (OSAS). However, only few studies have evaluated long-term effects of this treatment on lung function. This study assesses the effect of nCPAP on lung function parameters and response to bronchodilators in 50 OSAS patients. Spirometry and arterial blood gas measurements were performed before starting nCPAP and after 16.8 +/- 8 months of treatment. Of the 50 study patients (55 +/- 12 years, with an apnea/hypopnea index of 47 +/- 34h(-1)), 15 had asthma, 13 had chronic obstructive pulmonary disease (COPD) and 22 had no obstructive airway disease (NOAD). In the entire population, significant decreases in FEF50 (from 69 +/- 38% to 61 +/- 30%, P < 0.005), FEF25 (from 53 +/- 34% to 46 +/- 28%, P < 0.05) and FEF25-75 (from 65 +/- 33% to 57 +/- 27%, P < 0.005) were observed after treatment. No impairment of lung function was found in COPD and asthmatic patients. In contrast, lung function was changed in the NOAD group where FEF50, FEF25 and FEF25-75 as well as FEV1 and FEV1/VC ratio were significantly reduced. Moreover, bronchial hyperresponsiveness occurred in five of 22 patients of this group. These results suggest that tolerance of nCPAP should be handled by long-term follow-up of flow-volume loops.

Adult↗
PubMed2000

[Effectiveness of nasal CPAP-treatment (continuous positive airway pressure)].

Nasal continuous positive airway pressure (n-CPAP) is an effective treatment for the obstructive sleep apnea syndrome (OSAS). It is currently regarded as the first line therapy for OSAS. The principal indication for n-CPAP treatment is daytime sleepiness. Nasal-CPAP improves daytime sleepiness dramatically in severe cases and the effect is objectively measurable with the multiple sleep latency test (MSLT). It is noteworthy that n-CPAP also improves symptoms, subjective daytime sleepiness, cognitive function, IQ, mood, quality of life and driving ability already in patients with mild sleep apnea with an apnea/hypopneaindex (AHI) between 5 and 15 per hour of sleep during overnight polysomnography. Although not yet 100% robust, there is clear evidence that patients with OSAS have an increased frequency of systemic hypertension. Some early and imperfect studies suggest that CPAP reduces cardiovascular and cerebrovascular outcomes; however unequivocal evidence that n-CPAP reduces mortality is still awaited. There is now good evidence that treatment with n-CPAP reduces the two- to sevenfold increased risk of road accidents of untreated patients with OSAS. In summary, there exists abundant evidence today that n-CPAP is an efficient therapy for symptomatic patients with the obstructive sleep apnea syndrome. A trial with n-CPAP is therefore justified in all symptomatic patients. Based on the large number of randomized controlled trials of n-CPAP a therapeutic trial is indicated even in only mildly symptomatic patients with OSAS. Nasal-CPAP use and outcomes of therapy can be improved by provision of an intensive CPAP-education and support program.

Accidents, Traffic↗
PubMed1998

Tolerance and intolerance to continuous positive airway pressure.

Nasal continuous positive airway pressure (CPAP) is the most effective and widely used therapy for obstructive sleep apnea. As with any chronic therapy, long-term compliance has a significant impact on its effectiveness. Only about half of patients use CPAP for more than half the night on five or more nights per week. Approximately 4 hours of CPAP therapy per night appears to significantly improve daytime alertness and performance. Four hours of therapy also seems to improve sleep-disordered breathing for the remainder of the night. Patient education and close follow-up and intervention appear to improve long-term tolerance. Autotitration CPAP or bilevel positive airway pressure systems are no more effective or better tolerated than conventional CPAP therapy. They may be useful options if patients have been unable to tolerate conventional CPAP therapy.

Female↗
PubMed2003

Can patients with obstructive sleep apnea titrate their own continuous positive airway pressure?

Manual continuous positive airway pressure (CPAP) titration in a sleep laboratory is costly and limits access for diagnostic studies. Many factors affect CPAP compliance, but education and support, rather than in-laboratory CPAP titration, appear to be pivotal. Self-adjustment of CPAP at home will provide equal or superior efficacy in the treatment of obstructive sleep apnea (OSA) as compared with in-laboratory titration. A randomized, single-blind, two-period crossover trial of CPAP treatment at the in-laboratory-determined optimal pressure versus at-home self-adjustment of CPAP (starting pressure based on prediction equation). Eighteen CPAP-naive patients (16 males, 50 +/- 15 years old, apnea hypopnea index 40 +/- 20) with a new diagnosis of OSA were tested. Testing was performed before and after CPAP treatment in each of two 5-week study limbs. CPAP, compliance with CPAP treatment, the Sleep Apnea Quality of Life Index, the Functional Outcomes of Sleep Questionnaire score, the Epworth sleepiness scale score, sleep architecture, sleep apnea severity, and maintenance of wakefulness tests were performed. Both modes of CPAP treatment significantly improved objective and subjective measures of OSA, but they did not differ in efficacy. Home self-titration of CPAP is as effective as in-laboratory manual titration in the management of patients with OSA.

Adult↗
PubMed2004

Upper airway surgery benefits patients with obstructive sleep apnoea who cannot tolerate nasal continuous positive airway pressure.

Nasal continuous positive airway pressure (CPAP) is the mainstay of treatment for patients with moderate to severe obstructive sleep apnoea (OSA). However, tolerance and compliance are poor. An audit using the Christchurch Hospital ORL surgery database identified patients who underwent upper airway surgery for OSA. Tracheostomy and bimaxillary advancement patients were excluded. Adults with moderate to severe OSA (Desaturation Index (DI) >10 n.h(-1)), who had failed a trial of nasal CPAP, and had pre-operative and post-operative sleep study data were identified. Objective (DI) and Subjective (Epworth Sleepiness Score (ESS)) outcome measures were recorded. The database identified 69 patients who underwent surgery for snoring or OSA; of these, 25 patients formed the study group. Sixteen out of 25 improved (64 per cent) after surgery, seven out of 25 showed no change (28 per cent), two patients (eight per cent) showed deterioration in their DI. Forty-eight per cent of patients had >50 per cent post-operative improvement in DI. Fourteen out of 25 (56 per cent) had a post-operative DI <20 n.h(-1). Seven out of 25 (28 per cent) had a post-operative DI <10 n.h(-1). Upper airway surgery has a role in the management of selected patients with OSA who cannot tolerate nasal CPAP.

Adult↗
PubMed1994

Neonatal nasal deformities secondary to nasal continuous positive airway pressure.

Nasal continuous positive airway pressure (CPAP) is being used more frequently in neonatal intensive care units to avoid endotracheal intubation and its attendant complications. Nasal deformities secondary to the nares-occluding prongs employed to deliver the CPAP in former preterm infants have been recognized, and prevention and surgical treatment of these deformities are discussed. An awareness of the potential for these deformities is important to all pediatric otolaryngologists as nasal CPAP is gaining increasing favor as a primary treatment for respiratory disease of the newborn.

Child, Preschool↗
PubMed1990

Ventilatory effects of nasal continuous positive airway pressure.

Nasal continuous positive airway pressure (nCPAP) improved arterial oxygenation in patients with sleep apnoea as well as those with acute pulmonary processes such as Pneumocystis carinii pneumonia. Despite an expanding pool of clinical information, little if any attempt seems to have been made to see whether nCPAP alters ventilatory patterns. The effect of nCPAP was assessed by respiratory inductance plethysmography in 14 healthy males. nCPAP reduced respiratory rate (14.3 +/- 1.47 to 9.7 +/- 1.98, p less than 0.0001) but increased tidal volume (0.483 +/- 0.090 to 0.602 +/- 0.140 l, p = 0.01). Accordingly, minute ventilation decreased (6.91 +/- 1.20 to 5.64 +/- 0.93 l.min-1, p = 0.0002). Duty cycle (TI/TTOT) decreased from 0.43 +/- 0.04 to 0.35 +/- 0.05 s during nCPAP (p less than 0.0001). Mean inspiratory time and mean expiratory time increased with nCPAP (1.79 +/- 0.19 to 2.20 +/- 0.41 and 2.44 +/- 0.38 to 4.27 +/- 1.07 s, respectively, p less than 0.02), but there were no significant changes in mean inspiratory flow rate or partitioning of rib cage and abdominal/diaphragmatic contributions to tidal volume. We conclude that nCPAP effects ventilatory pattern in a manner similar to that described for expiratory threshold loading; that is, by decreasing respiratory frequency and minute ventilation. nCPAP does not appear to stimulate healthy subjects to increase their level of ventilation.

Adult↗