Nasal continuous positive airway pressure devices do not maintain the set pressure dynamically when tested under simulated clinical conditions

Seasonal effects on the continuous positive airway pressure adherence of patients with obstructive sleep apnea

OBJECTIVE

This study examined seasonal differences in continuous positive airway pressure (CPAP) therapy adherence among patients with obstructive sleep apnea (OSA).

METHODS

Patients aged ≥20 years with OSA who had used CPAP devices on the automatic setting for >12 consecutive months (n = 141) were included in this retrospective study from December 2015-2016. The information of CPAP use (pressure, hours of actual use) was extracted from database downloaded from patients' CPAP devices. Patients were divided into adherent and non-adherent groups using the cutoff point of 70% CPAP use for ≥4 h daily over the 1-year study period. CPAP use data were averaged for each season.

RESULTS

Patients in the adherent group were significantly older than those in the non-adherent group (p < 0.001). In the adherent group, the rate of ≥4 h daily CPAP use was significantly lower, the daily duration of CPAP use was significantly shorter, and the residual apnea-hypopnea index (AHI; events/hour) was significantly higher in summer than in other seasons (all p < 0.001). In the non-adherent group, the duration of daily CPAP use and the AHI differed significantly between winter and summer (p = 0.008 and p < 0.001, respectively).

CONCLUSIONS

Seasonal changes were associated with the CPAP adherence of patients with OSA. The study findings suggest that there is possibility of increasing the duration of CPAP use by adjusting the bedroom environment in hot and humid seasons.

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.

Clinical factors affecting inspired gas humidification and oral dryness during noninvasive ventilation

PURPOSE

Oral dryness is a common complication during noninvasive ventilation (NIV). We measured the oral dryness of patients and performed a bench study to investigate factors related to humidification during NIV.

MATERIALS AND METHODS

Patients were randomly assigned into 2 groups: medium (Med group) and maximum (Max group) heated humidifier (HH) settings. Oral moistness was measured using an oral moisture-checking device, and the feeling of oral dryness was evaluated using a 0 to 10 numerical rating scale (NRS) at 0, 12, and 24 hours from the beginning of NIV and at 12 and 24 hours after NIV was discontinued. A bench study was performed to assess the effects of positive end-expiratory pressure (PEEP), the fraction of inspired oxygen (F(I)O(2)), and air leaks on absolute humidity. We evaluated 3 HH settings: no HH, HH at the medium setting, and HH at the maximum setting. The temperature in the outlet chamber was 31°C to 32°C for the medium HH setting and 38°C to 41°C for the maximum HH setting.

RESULTS

In the clinical study, 12 patients were assigned to the Med group and 11 to the Max group. In the Med group, oral moistness decreased and NRS increased at 12 and 24 hours compared with 0 hours (P < .05). In the Max group, neither the oral moistness nor the NRS changed throughout the study period, whereas in the bench study, high F(I)O(2), high PEEP, and air leak decreased the absolute humidity for both HH settings (P < .01). However, it is not clear to what extent these factors affected the patients' oral dryness because the ranges of F(I)O(2) and PEEP were narrow.

CONCLUSIONS

Oral dryness was a common problem in our patients. The HH setting significantly affected humidification and oral dryness during NIV.

Effect of tubing condensate on non-invasive positive pressure ventilators tested under simulated clinical conditions

RATIONALE

Water condensate in the humidifier tubing can affect bi-level ventilation by narrowing tube diameter and increasing airflow resistance. We investigated room temperature and tubing type as ways to reduce condensate and its effect on bi-level triggering and pressure delivery. In this bench study, the aim was to test the hypothesis that a relationship exists between room temperature and tubing condensate.

METHODS

Using a patient simulator, a Res-med bi-level device was set to 18/8 cm H(2)O and run for 6 h at room temperatures of 16°C, 18°C and 20°C. The built-in humidifier was set to a low, medium or high setting while using unheated or insulated tubing or replaced with a humidifier using heated tubing. Humidifier output, condensate, mask pressure and triggering delay of the bi-level were measured at 1 and 6 h using an infrared hygrometer, metric weights, Honeywell pressure transducer and TSI pneumotach.

RESULTS

When humidity output exceeded 17.5 mg H(2)O/L, inspiratory pressure fell by 2-15 cm H(2)O and triggering was delayed by 0.2-0.9 s. Heating the tubing avoided any such ventilatory effect whereas warmer room temperatures or insulating the tubing were of marginal benefit.

CONCLUSIONS

Users of bi-level ventilators need to be aware of this problem and its solution. Bi-level humidifier tubing may need to be heated to ensure correct humidification, pressure delivery and triggering.

Pressure stability with CPAP devices: A bench evaluation

BACKGROUND

Continuous positive airway pressure (CPAP) maintains a constant pressure to reduce the patient's work of breathing (WOB). The aim of this study was to measure the additional WOB imposed by four current CPAP devices during simulation of a difficult but commonly encountered clinical situation.

METHOD

Flow contour, respiratory system compliance and total lung-airway resistance of a patient under CPAP were simulated. The devices were tested at a CPAP of 15cm H(2)O with a heated humidifier and a nasal pillow, which increased circuitry resistance and with and without a simulated unintentional leak.

RESULTS

With no leak, positive end-expiratory pressure (PEEP) at the interface varied across devices from 14.0 to 15.3cm H(2)O. With a leak of 1L/s, PEEP varied from 11.5 to 17.1cm H(2)O. Imposed inspiratory WOB ranged from less than 0.1J/min to 0.45J/min with no leak, and the range broadened with leaking. Findings were similar for the imposed expiratory WOB.

CONCLUSION

The performances of CPAP devices are variable. The device that calibrated for the pressure loss in the circuitry under dynamic conditions and made appropriate pressure adjustments outperformed the other devices.

Positive pressure therapy: a perspective on evidence-based outcomes and methods of application

The sleep medicine community has increasingly recognized the necessity that clinical care be based on high-quality levels of evidence. Although research supports a favorable influence of positive airway pressure (PAP) therapy on risk for significant adverse outcomes in patients with severe obstructive sleep apnea-hypopnea (OSAH), well-designed trials are still required to elucidate the effect of PAP on health, quality of life, and economic risks in patients with milder OSAH. Similarly, although there is strong evidence supporting various PAP titration strategies and PAP modalities in patients with severe OSAH without significant medical and psychiatric comorbidities, there is insufficient high-level evidence assessing and comparing the clinical efficacy and health care cost implications of various titration paradigms and various PAP modalities in individuals with milder OSAH and those with comorbid conditions. For ethical and other reasons, it may not be possible to apply a randomized controlled design to address all questions. However, whichever design is employed, it must be rigorously developed with attention to all potential confounders with adequate power to provide compelling, high-quality evidence.

Continuous positive airway pressure: new generations

Automatic positive airway pressure devices are the most technologically advanced positive airway pressure devices available for use in OSA. Although heterogeneous, they have in common the ability to detect and respond to changes in upper airway resistance. Data cannot necessarily be extrapolated from one device to another, and the field is rapidly advancing. Most studies of APAP have been performed in a supervised setting, or patients have been carefully selected to have a high likelihood of OSA uncomplicated by disorders such as alveolar hypoventilation or central apnea or technical problems such as mask leaks. Studies of APAP for the diagnosis of OSA have shown that APAP can diagnose severe OSA effectively, but the diagnosis of mild-moderate OSA is less reliable. APAP devices also can be effective therapy for selected patients with OSA, with overall similar results to conventional fixed CPAP in terms of respiratory disturbances, sleep quality, nocturnal oxygenation, and daytime sleepiness and performance, with less known or other long-term outcomes. In most studies, mean treatment pressures are lower, without change in side effect profile. Compliance and preference with APAP are similar to or somewhat better than CPAP in most studies. APAP also can be used in an attended setting to titrate an effective pressure for use in long-term conventional CPAP therapy, also with similar results to CPAP in many patients. APAP devices are more expensive than CPAP devices, but the cost may be outweighed if a group of patients who can be diagnosed, treated, or titrated safely in the unattended setting can be identified. Although diagnostic and therapeutic algorithms for APAP have been proposed, the best candidates for this modality must be defined better.