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* From the Alexian Brothers Medical Center (Drs. Massie and Hart), Elk Grove Village, IL; Central DuPage Hospital (Ms. Peralez), Winfield, IL; and Respiratory Services (Dr. Richards), Green Lane Hospital, Auckland, New Zealand.
Correspondence to: Clifford A. Massie, PhD, Suburban Lung Associates, 810 Biesterfield Rd, Suite 404, Elk Grove Village, IL 60007; e-mail: CMassie{at}AOL.com
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Abstract |
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 TOP Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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Design: A randomized, crossover design was employed.
Setting: The study was conducted at two suburban community-based hospital sleep laboratories.
Patients: Data were collected on 38 obstructive sleep apnea patients (mean age, 44.1 years) in whom CPAP was a novel treatment.
Interventions: The interventions were heated humidity, cold passover humidity, and a washout period without humidity.
Measurements and results: Patients were titrated with
heated humidity or cold passover humidity in the laboratory and
subsequently initiated on humidity. Objective compliance, self-report
of factors affecting CPAP use, satisfaction with CPAP, feeling upon
awakening, and daytime sleepiness were assessed at the completion of
each 3-week treatment period and a 2-week washout period. Outcome
measures were assessed with one-way analysis of variance followed by
Scheffe post hoc comparisons. Significant main effects
were observed for compliance (F2,37 = 5.2; p = 0.008),
satisfaction with CPAP (F2,37 = 4.5; p = 0.01), and
feeling refreshed on awakening (F2,37 = 4.4; p = 0.02).
A significant decrease in daytime sleepiness was observed between
baseline and each of the conditions (F3,37 = 55.5;
p < 0.0001), but Epworth sleepiness scale scores did not differ
between conditions (all p values > 0.56). CPAP use with heated
humidity (5.52 ± 2.1 h/night) was greater than CPAP use without
humidity (4.93 ± 2.2 h/night; p = 0.008). Compliance differences
were not observed between CPAP use with cold passover humidity and CPAP
use without humidity. Patients were more satisfied with CPAP when it
was used with heated or cold passover humidity (p 
0.05). However,
only heated humidity resulted in feeling more refreshed on awakening
(p < 0.05). No significant differences were observed among the three
groups on the global adverse side effect score
(F2,37 = 2.5; p = 0.09). Specific side effects such as
dry mouth or throat and dry nose were reported less frequently when
CPAP was used with heated humidity compared to CPAP use without
humidity (p < 0.001).
Conclusions: Compliance with CPAP is enhanced when heated humidification is employed. This is likely due to a reduction in side effects associated with upper airway symptoms and a more refreshed feeling upon awakening. Compliance gains may be realized sooner if patients are started with heated humidity at CPAP initiation.
Key Words: compliance • continuous positive airway pressure • humidity • nasal symptoms • obstructive sleep apnea
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Introduction |
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TOPAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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As many as 65% of patients using CPAP report significant side effects such as nasal congestion, dry nose or throat, and discomfort associated with cold air.3 6 8 9 10 Epistaxis occurs less frequently, but can be severe.11 Chronic nasal congestion may compromise a patient's ability to successfully utilize CPAP.12 Upper airway symptoms are caused by mouth leaks that produce high unidirectional airflow over nasal and oral mucosa. Simulation of a mouth leak in persons breathing with CPAP while awake produces a subjective feeling of mouth and nose dryness, nasal congestion, and an increase in nasal resistance.13 Heated humidity, but not cold passover humidity, greatly attenuates the magnitude and duration of the increases in nasal airway resistance. Other investigators have reported increases in nasal mucosal blood flux in patients simulating a mouth leak while using CPAP.14 Heated humidity prevents the increase in mucosal blood flux, suggesting that the cooling or drying effect of the airflow is responsible for the change. These studies were conducted in normal subjects while awake, but it is reasonable to assume that a similar mechanism may operate in apneic patients while asleep.
Humidity is employed to alleviate dryness and congestion in OSA patients. Two types of humidity are commonly employed: cold passover humidity and heated humidity. Little is known about the effects of these types of humidity on compliance with CPAP or nasal symptoms in sleep apnea patients. One study10 reported no differences in side effects between patients who used humidity compared to those who did not use humidity. However, no information was given regarding the type of humidity or the criteria used to determine which patients received humidity; therefore, definitive conclusions could not be made. This study evaluates the effects of heated and cold passover humidification on nasal symptoms and compliance with CPAP.
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Materials and Methods |
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TOPAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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10), and had not
received CPAP treatment previously. Comorbid medical or
psychological conditions were considered to be exclusion criteria only
if the condition interfered with the patient's ability to successfully
utilize CPAP. Exclusion criteria included wake resting pulse oximetric
saturation < 90%, evidence of upper airway tract infection or
flu-like symptoms at the time of titration, hospitalization 3 months
prior to study initiation, elective surgery scheduled before the
conclusion of the study, or prior surgical intervention for OSA.
Participants were not eligible if they required bilevel positive airway
pressure ventilation, a full face mask, or supplemental oxygen. At the time of the initial polysomnogram, patients gave consent. The participants agreed to use CPAP for the duration of the 8-week study and to provide feedback on nasal symptoms and satisfaction with the humidifier. The patients were not informed that the study was designed to assess compliance, but they were debriefed at the conclusion of the study regarding compliance monitoring. Institutional review board approval was obtained from both sites; the consent forms were identical.
Questionnaires
The patients completed a questionnaire assessing chronic nasal
symptoms prior to the start of polysomnography. The patients were asked
to indicate in the affirmative or negative whether they experienced the
following symptoms on a regular basis: dry nose, runny nose, postnasal
drip, nasal congestion, nose bleeds, reduced sense of smell, sinus
infections, dry throat, sore throat, hoarse voice, cough, or allergies.
The patients also completed the Epworth sleepiness scale (ESS).
Following the CPAP titration, a modified post-sleep questionnaire was
administered. The patients were asked about nasal symptoms they
experienced during the titration, and they were asked to indicate (as
not at all, somewhat, or a lot) whether they experienced congested
nose, dry nose, dry mouth or throat, air leaks from the mask, or skin
irritation.
At each assessment interval, the patients completed the ESS and the CPAP questionnaire. The patients were asked to rate adverse side effects in the following terms: (1) not a problem (a slight problem, but it did not interfere with using CPAP); (2) a moderate problem (sometimes I could not use CPAP); or (3) a major problem (I often could not use CPAP). Factors that were considered included the following: pressure from mask or straps; air leaks from the mask; machine noise; cold face or nose; claustrophobia; dry mouth or throat; congested nose; dry nose; nose bleeds; headache; difficulty breathing; chest discomfort; mask coming off the face; and skin irritation. At the end of each treatment period and washout period, the patients were asked to indicate on a 100-mm Likert scale how satisfied they were with CPAP during that time period and how refreshed they felt upon awakening.
Polysomnography
The sleep studies commenced at the patient's usual bedtime and
concluded after the patient's time in bed was approximately 7 h.
Standard polysomnography was performed at two suburban community
hospitals using commercially available equipment (Central DuPage
Hospital [CDH]; Sandman 2.4; Nellcor Puritan Bennett;
Pleasanton, CA; and Alexian Brothers Medical Center [ABMC]; model
4412P; Nihon-Kohden; Tokyo, Japan or model 4100 Somnostar;
SensorMedics; Yorba Linda, CA). Similar montages were used at both
CDH and ABMC: left and right electro-oculography, surface EEG
(electrode locations C4-A1, FZ-A2 [CDH only], and O2-A1), submental
electromyography, ECG, anterior tibial electromyography, sonogram,
nasal/oral airflow via thermistor, thoracic effort, and abdominal
effort. Oxyhemoglobin saturation was recorded via pulse oximetry
(model 504; Criticare; Waukesha, WI [for CDH]; and Biox
3740; Ohmeda; Louisville, CO [for ABMC]). Desaturations were defined
as a drop in oxyhemoglobin saturation of 4%.
Sleep staging was determined according to Rechtschaffen and
Kales.15
An obstructive apnea was defined as cessation of
airflow (airflow tracing between 0% and 20% of baseline) for 10
s, accompanied by an arousal or desaturation. A hypopnea was defined as
above, except that airflow tracing was between 20% and 75% of
baseline. In both cases, evidence of continued thoracic and/or
abdominal effort was required. Arousals were defined as a 3-s change in
EEG, as represented by a frequency shift. Spontaneous arousals
were defined by exclusion; they were not associated with a respiratory
event or linked to a leg movement, position change, or other gross body
movement.
Study Design
A randomized, crossover design was employed. The patients were
assigned to either heated humidity or cold passover humidity for the
laboratory titration. The patients assigned to heated humidity were
titrated with an appropriate humidifier (HC100; Fisher & Paykel
Healthcare; Auckland, New Zealand). The patients assigned to cold
passover humidity were titrated with an appropriate humidifier (Oasis;
Respironics; Murrysville, PA). Each patient underwent either an
all-night CPAP titration following a full night of diagnostic study or
a split-night study protocol. CPAP was initiated during a
split-night study if the RDI was > 30 and oxyhemoglobin desaturation
4% occurred consistently in association with the sleep breathing
events. Titration protocols were identical at both sites. Pressure
increases were performed manually: 2 cm for obstructive apneas, and 1
cm for obstructive hypopneas, snores, desaturations, and arousals. All
patients were titrated using a nasal mask (Sullivan Mirage;
ResMed; San Diego, CA). Effective pressure was attained when evidence
of apneas, hypopneas, snoring, hypoxemia, and arousals were
ameliorated. CPAP was prescribed after the polysomnogram was reviewed.
All patients were set up with a CPAP machine (Sullivan V Elite Real Time Clock; ResMed) and a Sullivan Mirage nasal mask. The patients were given detailed instructions on the use and care of the CPAP machine, mask, humidifier, and related equipment. For the duration of the study, patients were instructed to maintain a constant temperature in their bedrooms during sleep. When possible, the patients were instructed to maintain a constant humidity in the bedroom; for example, if a room or home humidifier was normally used, the patients were instructed to continue its use. The addition of this type of humidity during the study was discouraged. When the patients were given the heated humidified air, the dial was set at 4. The patients were told not to change this setting if they felt comfortable. If water droplets formed in the mask, patients were instructed to decrease the setting by 0.5 U until the condensation no longer appeared. These are the same instructions used by the health-care company (Health Management; Barrington, IL) for all patients set up on CPAP with heated humidity. Specific to this study, information about side effects was not given, and the patients were not told that the humidifier could be operated without heat. For the first 3 weeks, the participants used the same humidity as in the titration study. This was followed by a 2-week washout period in which no humidity was used. The participants then switched to the alternate humidity for the final 3 weeks. There were three office visits, one at the end of each active treatment period, and one at the end of the washout period. At each office visit, the ESS and CPAP questionnaires were completed.
At each visit, the patients were told that a pressure check was required as part of the study protocol. While the patients completed the questionnaires, compliance data were downloaded from the CPAP machine using compliance software (SCAN 2.01; ResMed). The actual use per 24-h period was recorded; a pressure transducer recorded use only when the patient was breathing with the mask in place. At the first follow-up office visit, the humidifier was taken from the patient and he or she was instructed to use CPAP without humidity. At the second office visit, the alternate humidifier was given to the patient with detailed instructions for its use. At the final office visit, the patient was asked which type of humidifier he or she preferred, and the patient was maintained on this type of humidity.
In general, the patients were able to use each humidifier for the duration of the treatment period. Daily logs were not maintained, but patients were queried about CPAP use during each treatment period. When patients did not use CPAP because of travel, these days were excluded from analysis. No more than 3 days during a treatment period had to be excluded in any patient. The patients who attempted to use CPAP each night, but had difficulties maintaining use throughout the night, were included in analyses, provided that the mean daily use was > 1 h for at least one of the treatment periods.
Statistical Analysis
Values are given as mean ± SD. Comparisons among the two
treatment conditions and the washout period were conducted using
one-way analysis of variance. Significant main effects were followed
with Scheffe post hoc comparisons. Unless otherwise
indicated, statistical significance required p 0.05 (two-tailed).
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Results |
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TOPAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Thirty-eight patients completed the 8-week pro-tocol. Seventeen
patients had full-night CPAP titrations, and 21 patients had
split-night studies. Twenty-two patients were randomized to heated
humidity, and the remaining 16 received cold passover humidity. There
were no differences between randomized groups in age, gender, study
type, body mass index (BMI), RDI or CPAP pressure (all p values
0.07). These data are presented in Table 1
. No differences were noted in age, gender, study type, BMI, RDI, or
CPAP pressure between the two sleep laboratories (all p values
0.37).
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Compliance
A significant main effect for compliance was observed
(F2,37 = 5.2; p = 0.008). Compliance was
higher for CPAP use with heated humidity (5.52 ± 2.1 h) compared to
CPAP use without humidity (4.93 ± 2.2 h; p = 0.008), but no
difference was observed between CPAP use with cold passover humidity
and CPAP without humidity, or between heated and cold passover humidity
(p values > 0.14). Duration of use ranged from 1.0 to 9.1 h/night on
heated humidity, 0.8 to 8.0 h/night on cold passover humidity, and 0.8
to 8.6 h/night during the washout period.
Symptom Improvement
The overall satisfaction with CPAP and feeling refreshed on
awakening were assessed with a 100-mm Likert scale. Significant main
effects were observed for overall satisfaction with CPAP
(F2,37 = 4.5; p = 0.01) and feeling refreshed
on awakening (F2,37 = 4.4; p = 0.02). Heated
humidity and cold passover humidity were associated with greater
satisfaction (p 0.05). Heated humidity, but not cold passover
humidity, was associated with feeling more refreshed on awakening
(p = 0.005). A significant decrease in daytime sleepiness was
observed between baseline and each of the conditions
(F3,37 = 55.5; p < 0.0001), but ESS scores
did not differ between conditions (all p values > 0.56).
Adverse Side Effects
At the conclusion of each treatment period and washout period,
adverse side effects were assessed and a global score was calculated.
No significant differences were observed among the three groups
(F2,37 = 2.5; p = 0.09). Item analysis
comparisons were conducted to determine which individual side effects
differed between CPAP use with heated humidity and CPAP use without
humidity, because this may account for the compliance difference. To
control for multiple pairwise comparisons, the p value was set at 0.01.
Patients reported that dry mouth or throat and dry nose interfered to a
greater degree when CPAP was used without humidity compared to CPAP use
with heated humidity (p < 0.001). These side effects were not
different between cold passover humidity and no humidity (p values
> 0.35). Differences in compliance, symptom improvement, and adverse
side effects between CPAP use with heated humidity, CPAP use with cold
passover humidity, and CPAP use without humidity are presented in Table 3
.
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Discussion |
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TOPAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Sixty percent of patients in this sample reported chronic nasal congestion prior to initiating CPAP therapy. Nasal symptoms are common in patients with OSA, and nasal obstruction is a risk factor for sleep apnea.16 Nasal congestion due to allergy promotes sleep-disordered breathing in normal subjects, and it is associated with an increased risk for moderate to severe OSA.16 17 Furthermore, chronic nasal symptoms predispose OSA patients to mouth breathing. This normally has few consequences, but the use of CPAP exacerbates mouth leaks, causing high unidirectional airflow across the nasal and oral mucosa. The flow of cold air through the nose dries the mucosa and increases nasal airway resistance.18 This also stimulates local nerves and leads to the release of inflammatory mediator cells.19 Mouth leaks in normal subjects reproduce symptoms experienced by patients using CPAP, leading to increased nasal airway resistance and nasal mucosal blood flow.13 14 The results of this study suggest that heated humidifiers can prevent these changes in OSA patients and that the humidity output of cold passover humidifiers is insufficient to prevent mucosal drying.
Subjective improvement in mood and energy has been reported in CPAP users without nasal symptoms when compared to CPAP users with nasal symptoms.12 Although compliance data were not reported in the study by Redline et al,12 it is possible that the improvements in daytime functioning were the result of greater CPAP use by the group without nasal symptoms. In the present study, preexisting nasal symptoms did not predict humidity choice or influence compliance. However, a reduction in nasal symptoms associated with mucosal drying was observed with heated humidity. Although the attenuation of nasal symptoms did not result in lower ESS scores, it is possible that improvements in mood and energy may also have occurred. In the only other study to examine side effects and humidification, Pepin et al10 reported no difference in adverse side effects between patients who used humidity and those who did not use humidity. The type of humidifier was not reported in their study; patients using CPAP without humidity may have been compared to patients using CPAP with cold passover humidity.
Compliance with CPAP has been reported extensively in the literature and is well recognized to be less than optimal. Despite the recognition that CPAP compliance needs to be improved, few intervention studies have been undertaken. The support and education of CPAP users have been the only interventions reported in the literature. Chervin et al20 performed a randomized clinical trial assessing the effects of education on compliance. The two treatment groups received an additional phone call or printed literature, whereas the control group received only the standard information that was conveyed at the time of evaluation. The groups that received additional information, either verbally or in writing, showed greater compliance compared to the control group. In fact, compliance was greater by 1.3 h/night for the group that received verbal information via telephone, and compliance was increased by 2.7 h/night for the group that received additional written information. Increased compliance has also been demonstrated in a group setting.21 The patients who had been on CPAP for varying lengths of time had an average compliance of 5.2 h/night. Following attendance at one CPAP clinic that provided patient support, education, an equipment check, and symptom treatment, subsequent compliance increased to a mean of 6.3 h/night.
This is the first study to demonstrate that CPAP use can be increased by an intervention other than patient education and support. Compliance was improved by 0.59 h/night by the addition of heated humidification (a finding that is lower than the results of previous intervention studies, but still clinically relevant). The optimal amount of CPAP use has yet to be determined, and any increase in use is desirable. Humidification in this study was supplied to all eligible patients starting CPAP, and it was initiated during pressure titration. In clinical practice, humidification is usually reserved for patients who complain of persistent and severe side effects related to upper airway symptoms, and its introduction may be delayed for several weeks or months. Waiting for the development of upper airway symptoms may identify the patients most likely to benefit from humidification, but delaying its introduction may reduce potential benefits on compliance. Indeed, patients who become irregular CPAP users (defined as extreme variability in use averaging < 4 h/night) can be identified by the fourth day of treatment.22
In summary, this is the first study to systematically examine the effects of humidity on compliance and adverse side effects in OSA patients using CPAP. The results of this study demonstrate that heated humidity increases compliance with CPAP. The difference in compliance may be explained by a reduction in side effects associated with upper airway symptoms and awakening feeling more refreshed after using CPAP with heated humidity. Compliance gains may be realized sooner if patients are started with heated humidity at the initiation of CPAP.
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Acknowledgements |
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Footnotes |
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Abbreviations: ABMC = Alexian Brothers Medical Center; BMI = body mass index; CDH = Central DuPage Hospital; CPAP = continuous positive airway pressure; ESS = Epworth sleepiness scale; OSA = obstructive sleep apnea; RDI = respiratory disturbance index
Received for publication October 26, 1998. Accepted for publication March 2, 1999.
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