Continuous positive airway pressure (CPAP) induces early nasal inflammation

A sleep clinician's guide to runny noses: evaluation and management of chronic rhinosinusitis to improve sleep apnea care in adults

STUDY OBJECTIVES

The treatment of obstructive sleep apnea is often impeded by intolerance of positive airway pressure therapy, which is frequently attributed to the inability to breathe through the nose. Providers caring for patients with sleep apnea need a working knowledge of nasal passage disease and available treatments to better manage this common comorbidity.

METHODS

This review examines the literature connecting rhinosinusitis to adverse sleep and sleep apnea outcomes. It explores the different types of nasal and sinus diseases a sleep apnea provider might encounter, focusing on the medications used to treat them and indications for referral to otolaryngology.

RESULTS

Chronic rhinosinusitis can be either allergic or nonallergic. Both types can interfere with sleep and sleep apnea therapy. The successful management of chronic rhinosinusitis can improve positive airway pressure tolerance and adherence. A wide range of over-the-counter and prescription pharmacotherapy is available, with data supporting intranasal over oral treatment. Surgical treatment for chronic rhinosinusitis in obstructive sleep apnea addresses nasal obstruction, often with inferior turbinate reduction and septoplasty.

CONCLUSIONS

Sleep specialists should have a working knowledge of the available options to treat chronic rhinosinusitis. These options are often safe, effective, and readily accessible. Otolaryngologists and allergists/immunologists provide additional treatment options for more complicated patients. Providing treatment for chronic rhinosinusitis should be included as part of comprehensive sleep apnea care.

CITATION

Ali MM, Ellison M, Iweala OI, Spector AR. A sleep clinician's guide to runny noses: evaluation and management of chronic rhinosinusitis to improve sleep apnea care in adults. J Clin Sleep Med. 2023;19(8):1545-1552.

Nasal function and CPAP use in patients with obstructive sleep apnoea: a systematic review

PURPOSE

This systematic review was conducted to answer the following 3 questions: 'Does nasal pathology affect CPAP use?', 'What is the effect of CPAP on the nose?' and 'Does treatment of nasal pathology affect CPAP use?'.

METHODS

Pubmed and Scopus databases were searched for articles relevant to the study questions up to October 2020.

RESULTS

Sixty-three articles were selected, of which a majority were observational studies. Most studies identified a correlation between larger nasal cross-sectional area or lower nasal resistance and higher CPAP compliance or lower CPAP pressures; however, nasal symptoms at baseline did not appear to affect CPAP use. The effect of CPAP on the nose remains uncertain: while most studies suggested increased mucosal inflammation with CPAP, those investigating symptoms presented contradictory results, with some reporting an increase and others an improvement in nasal symptoms. Evidence is clearer for nasal surgery leading to an increase in CPAP compliance and a decrease in CPAP pressures, whereas there is little evidence available for the use of topical nasal steroids.

CONCLUSION

There appears to be a link between nasal volumes or nasal resistance and CPAP compliance, an increase in nasal inflammation caused by CPAP and a beneficial effect of nasal surgery on CPAP usage, but no significant effect of CPAP on nasal patency or effect of topical steroids on CPAP compliance. Results are more mitigated with regard to the effect of nasal symptoms on CPAP use and vice versa, and further research in this area would help identify patients who may benefit from additional support or treatment alongside CPAP.

Olfactory function in patients with obstructive sleep apnea and the effect of positive airway pressure treatment: a systematic review and meta-analysis

OBJECTIVES

To investigate olfactory function (OF) in patients with obstructive sleep apnea (OSA) and evaluate whether or not the use of positive airway pressure (PAP) treatment has an impact on olfactory performance.

METHODS

All studies published in English that gave satisfactory data regarding the assessment of OF in patients with OSA were included in this review. First, a baseline assessment of OF in patients with OSA who had not received any treatment was examined. Second, the effect of PAP therapy on OF was assessed to be able to make before and after comparisons. The primary outcome of this study was the threshold-discrimination identification (TDI) scores, obtained from the Sniffin' Sticks test.

RESULTS

The database search identified 552 articles. According to the exclusion criteria, 11 studies involving 557 patients diagnosed with OSA were included in this meta-analysis. The general rate of olfactory dysfunction was 73% (95% CI: 56.481-87.057) among the patients with OSA. The patients with OSA had lower TDI scores compared to the control group and the difference was statistically significant (p < 0.001). PAP treatment significantly improved the TDI scores in patients with OSA (p < 0.001). There was a significant negative correlation between the severity of apnea-hypopnea index and TDI scores (p = 0.001, z = -3.377, r = -0.438) and between age and TDI scores (p = 0.007, z = -2.695, r = -0.236).

CONCLUSION

This meta-analysis demonstrates that OSA impairs OF, while PAP treatment can reverse the olfactory performance of patients with OSA.

A 3D-printed microfluidic platform for simulating the effects of CPAP on the nasal epithelium

Obstructive sleep apnoea (OSA) is a chronic disorder that involves a decrease or complete cessation of airflow during sleep. It occurs when the muscles supporting the soft tissues in the throat relax during sleep, causing narrowing or closure of the upper airway. Sleep apnoea is a serious medical condition with an increased risk of cardiovascular complications and impaired quality of life. Continuous positive airway pressure (CPAP) is the most effective treatment for moderate to severe cases of OSA and is effective in mild sleep apnoea. However, CPAP therapy is associated with the development of several nasal side effects and is inconvenient for the user, leading to low compliance rates. The effects of CPAP treatment on the upper respiratory system, as well as the pathogenesis of side effects, are incompletely understood and not adequately researched. To better understand the effects of CPAP treatment on the upper respiratory system, we developed an in vitro 3D-printed microfluidic platform. A nasal epithelial cell line, RPMI 2650, was then exposed to certain conditions to mimic the in-vivo environment. To create these conditions, the microfluidic device was utilized to expose nasal epithelial cells grown and differentiated at the air-liquid interface. The airflow was similar to what is experienced with CPAP, with pressure ranging between 0-20 cm of H20. Cells exposed to pressure showed decreased barrier integrity, change in cellular shape, and increased cell death (lactate dehydrogenase release into media) compared to unstressed cells. Stressed cells also showed increased secretions of inflammatory markers IL-6 and IL-8 and had increased production of ATP. Our results suggest that stress induced by airflow leads to structural, metabolic, and inflammatory changes in the nasal epithelium, which may be responsible for developing nasal side-effects following CPAP treatment.

Effect of humidified versus nonhumidified CPAP on inflammatory response and nasopharyngeal symptoms in healthy participants

Introduction

Continuous positive airway pressure (CPAP) may induce nasal inflammation because of mucosal compression or dryness. This study examined the impact of humidified versus nonhumidified CPAP on nasal inflammation and upper airway symptoms.

Methods

Seventeen healthy male subjects with no previous or current history of nasal symptoms were recruited. All subjects underwent 3 hours of nonhumidified CPAP at 12.5 cmH₂O via nasal mask. Among the 17 studied subjects, seven returned to receive a humidified CPAP at 12.5 cmH₂O via nasal mask. The nasal wash leukocyte count was assessed at baseline and after each CPAP setting. The white blood cell (WBC) count and levels of WBCs that are mononuclear cells (including lymphocytes and monocytes) were monitored. A six-point nasal score was also assessed before and after the CPAP intervention.

Results

The nasal wash WBC count (10³/µL) and mononuclear cell level (10³/µL) at baseline, on 12.5 cmH₂O humidified CPAP, and on 12.5 cmH₂O nonhumidified CPAP were significantly different (p = 0.016; p = 0.003). Changes in nasopharyngeal symptoms occurred in 12 of 17 subjects (70.5%) in the nonhumidified group. Participants experienced at least one nasal symptom after application of nonhumidified CPAP at 12.5 cmH₂O.

Conclusion

The present investigation suggests that humidified CPAP was not associated with early nasal inflammation and there were fewer nasopharyngeal symptoms. Further study is required to confirm the results and evaluate the impact of adding heat to the humidified CPAP system.

How to manage continuous positive airway pressure (CPAP) failure -hybrid surgery and integrated treatment

Obstructive sleep apnea (OSA) is a prevalent disease, which influences social relations and quality of life with major health impact. The etiology of OSA is multi-factorial involving both anatomical obstruction and physiological collapse of the upper airway during sleep with different proportion in individual patients. Continuous positive airway pressure (CPAP) is the gold standard and first-line treatment for OSA patients. The mechanism of CPAP is acting as air splint to avoid principal pharyngeal collapse during sleep. Consequently, extrapharyngeal collapse and significant pharyngeal obstructions can lower its compliance and lead to its failure. Adequate mask and pressure with thorough survey to eliminate side effects of CPAP from nasal, mask and flow-related problems are the prerequisite to improve CPAP compliance. For CPAP failure patients, multi-dimensional surgery is an alternative and salvage treatment that involves soft tissue surgery, skeletal surgery, and bariatric surgery. OSA patients with craniofacial anomaly are suggested to skeletal surgery. By contrast, OSA patients with pathological obesity are referred to bariatric surgery. Soft tissue surgery targets at the nose, soft palate, lateral pharyngeal wall, tongue and epiglottis that can be implemented by multi-level surgery with hybrid technique (mucosa-preservation, fat-ablation, muscle-suspension, tonsil-excision, cartilage-reconstruction) to maximize surgical outcomes and minimize complications. Some evolution in surgical concept and technique are noteworthy that include mini-invasive septoturbinoplasty, palatal suspension instead of excision, whole tongue treatment, and two-dimensional supraglottoplasty. Postoperative integrated treatment including myofunctional, positional therapy and body weight control reduces relapse of OSA and improves long-term treatment outcomes.

Clinical side effects of continuous positive airway pressure in patients with obstructive sleep apnoea

CPAP is considered the gold standard treatment in OSA and is highly efficacious in controlling OSA symptoms. However, treatment effectiveness is limited because of many factors including low adherence due to side effects. This review highlights the range of side effects associated with CPAP therapy in patients with OSA. This information is important for the initiation of patients onto CPAP as well as their continued care while on treatment, given the increase in non-medically supervised CPAP care models in use globally.

Increased age adversely affects the therapeutic effect of CPAP treatment for olfactory functions

PURPOSE

The aim of this study was to compare olfactory functions pre- and post-CPAP treatment in patients with moderate to severe OSA, and to evaluate the factors that cause changes in olfactory functions.

METHODS

Twenty-two patients who had completed regular usage of CPAP treatment for 2 months were included in this prospective study. Olfactory tests using Sniffin' Sticks were performed pre- and post-treatment.

RESULTS

The mean age of the subjects was 47.6 ± 9.5 years. We did not find a significant change in olfactory functions after 2 months of CPAP treatment in our study group. When the patients were divided into two groups-those whose olfactory functions showed improvement and those whose functions did not-it was found that the mean age of the patients whose olfactory functions did not improve was significantly higher statistically. A significant adverse correlation was found between age and post-treatment olfactory functions, specifically in odour threshold and odour identification scores.

CONCLUSIONS

Increased age adversely affects the therapeutic effect of CPAP treatment for olfactory functions.

Heated humidification did not improve compliance of positive airway pressure and subjective daytime sleepiness in obstructive sleep apnea syndrome: A meta-analysis

Introduction

We performed a meta-analysis on whether heated humidification during positive airway pressure (PAP) could improve compliance and subjective daytime sleepiness in obstructive sleep apnea syndrome (OSAS) patients.

Materials and methods

We searched PubMed, EMBASE, Medline, Cochrane Library, Clinical Trials, Web of Science and Scopus from inception to Oct 29, 2017. We made meta-analysis on the all available randomized controlled trials (RCTs) which assessed effects of heated humidification intervention on PAP compliance and subjective daytime sleepiness, by subgroups of automatic adjusting positive airway pressure/ continuous positive airway pressure (APAP/CPAP) usage and patients with/without upper airway symptoms prior to PAP therapy.

Results

A total of nine RCTs were evaluated finally in this meta-analysis. When all the studies were pooled, heated humidification did not improve PAP usage time [weighted mean difference(WMD) = 13.28, 95% confidence interval(CI): -5.85 to 32.41, P = 0.17] or Epworth sleepiness scale (ESS) score (WMD = -0.63, 95% CI: -1.32 to 0.07, P = 0.08). In terms of PAP usage time, heated humidification failed to enhance compliance in both APAP (WMD = 22.34, 95%CI: -21.08 to 65.77, P = 0.31) or CPAP subgroup (WMD = 11.09, 95%CI: -10.21 to 32.40, P = 0.31) and it was also ineffective among patients with upper airway symptoms prior to PAP therapy (WMD = 22.74, 95% CI: -7.77 to 53.24, P = 0.14) or without (WMD = 13.22, 95%CI: -35.84 to 62.29, P = 0.60). In terms of ESS score, heated humidification did not reduce ESS scores in both APAP (WMD = -1.59, 95% CI: -3.81 to 0.64, P = 0.16) or CPAP subgroup (WMD = -0.39, 95% CI: -1.16 to 0.37, P = 0.32) and it was also helpless among patients with upper airway symptoms prior to PAP therapy (WMD = -1.17, 95% CI: -3.10 to 0.75, P = 0.23) or without (WMD = -0.30, 95%CI: -2.25 to 1.66, P = 0.76).

Conclusion

Heated humidification during PAP therapy improves neither the compliance nor ESS scores in OSAS patients, no matter what types of PAP or whether the patients had upper airway symptoms prior to PAP therapy. But to the population with upper airway symptoms and the APAP users, the conclusions were limited because of small sample size and possible selection bias. More attentions should be paid to these potentially possible benefited subgroups.

Significant improvement of olfactory performance in sleep apnea patients after three months of nasal CPAP therapy - Observational study and randomized trial

OBJECTIVES

The olfactory function highly impacts quality of life (QoL). Continuous positive airway pressure is an effective treatment for obstructive sleep apnea (OSA) and is often applied by nasal masks (nCPAP). The influence of nCPAP on the olfactory performance of OSA patients is unknown. The aim of this study was to assess the sense of smell before initiation of nCPAP and after three months treatment, in moderate and severe OSA patients.

METHODS

The sense of smell was assessed in 35 patients suffering from daytime sleepiness and moderate to severe OSA (apnea/hypopnea index ≥ 15/h), with the aid of a validated test battery (Sniffin' Sticks) before initiation of nCPAP therapy and after three months of treatment. Additionally, adherent subjects were included in a double-blind randomized three weeks CPAP-withdrawal trial (sub-therapeutic CPAP pressure).

RESULTS

Twenty five of the 35 patients used the nCPAP therapy for more than four hours per night, and for more than 70% of nights (adherent group). The olfactory performance of these patients improved significantly (p = 0.007) after three months of nCPAP therapy. When considering the entire group of patients, olfaction also improved significantly (p = 0.001). In the randomized phase the sense of smell of six patients deteriorated under sub-therapeutic CPAP pressure (p = 0.046) whereas five patients in the maintenance CPAP group showed no significant difference (p = 0.501).

CONCLUSIONS

Olfactory performance improved significantly after three months of nCPAP therapy in patients suffering from moderate and severe OSA. It seems that this effect of nCPAP is reversible under sub-therapeutic CPAP pressure.

TRIAL REGISTRATION

ISRCTN11128866.

Role of the Allergist-Immunologist and Upper Airway Allergy in Sleep-Disordered Breathing

BACKGROUND

Sleep-disordered breathing in general and obstructive sleep apnea in particular are commonly encountered conditions in allergy practice. Physiologically, nasal (or nasopharyngeal) obstruction from rhinitis, nasal polyposis, or adenotonsillar hypertrophy are credible contributors to snoring and nocturnal respiratory obstructive events. Nevertheless, existing practice parameters largely relegate the role of the allergist to adjunctive treatment in cases of continuous positive airway pressure intolerance.

OBJECTIVES

To survey active American Academy of Allergy, Asthma & Immunology members regarding their perceptions and practices concerning sleep-disordered breathing in adult and pediatric patients with rhinitis, and to review the medical literature concerning this connection to identify therapeutic implications and research gaps.

METHODS

Members of the Work Group on Rhinitis and Sleep-disordered Breathing composed and distributed a Web-based clinically oriented survey to active American Academy of Allergy, Asthma & Immunology members in mid-2015. The group, in addition, conducted an English-language literature review using PubMed and other sources.

RESULTS

Survey results were returned by 339 of 4881 active members (7%). More than two-third of respondents routinely asked about sleep problems, believed that sleep-disordered breathing was a problem for at least a "substantial minority" (10%-30%) of their adult patients, and believed that medical therapy for upper airway inflammatory conditions could potentially help ameliorate sleep-related complaints. Literature review supported the connection between high-grade nasal congestion/adenotonsillar hypertrophy and obstructive sleep apnea, and at least in the case of pediatric patients, supported the use of anti-inflammatory medication in the initial management of obstructive sleep apnea of mild-to-moderate severity.

CONCLUSIONS

Clinical allergy practice and the medical literature support a proactive role for allergists in the diagnosis and management of sleep-disordered breathing.

Early effects of continuous positive airway pressure in a rodent model of allergic rhinitis

BACKGROUND

Continuous positive airway pressure (CPAP) is the most commonly used treatment in obstructive sleep apnea. In a previous rat model study, we demonstrated that nasal CPAP induces early rhinitis expressed by nasal neutrophil extravasation. Here we hypothesized that nasal CPAP would worsen nasal inflammation on a previously inflamed mucosa. The objective of this study was to evaluate the early nasal CPAP effects of allergic rhinitis (AR) in a rodent model.

METHODS

Twenty Sprague-Dawley rats were sensitized with intraperitoneal ovalbumin (OVA). Nasal inflammation was induced by the administration of intranasal OVA during consecutive days. The same procedure was performed in 20 control rats treated with saline solution. The allergic (AR) and non-allergic (NAR) rats were then randomized to nasal CPAP at 10 cm H₂O for five hours or to sham CPAP. The degree of nasal inflammation was assessed by evaluating the percentage of neutrophils, eosinophils, basophils, and lymphocytes in the nasal mucosa. An unpaired Mann-Whitney test was used to analyze differences between groups.

RESULTS

The greatest inflammation was observed in the group of AR without CPAP (1.24% ± 0.94%), followed by NAR with CPAP (0.64% ± 0.30%), AR with CPAP (0.64% ± 0.40%), and NAR without CPAP (0.21% ± 0.29%).

CONCLUSIONS

Administration of nasal CPAP or allergy sensitization can produce, individually, neutrophil extravasation on the nasal mucosa of a rat model. The application of both stimuli is not responsible for increased inflammation. Therefore, this study suggests that rhinitis is not a major limitation for CPAP administration.

When continuous positive airway pressure (CPAP) fails

Obstructive sleep apnoea (OSA) is increasingly prevalent, particularly in the context of the obesity epidemic, and is associated with a significant social, health and economic impact. The gold standard of treatment for moderate to severe OSA is continuous positive airway pressure (CPAP). However compliance rates can be low. Methodology to improve patient tolerance to CPAP alongside with alternative, non-surgical and surgical, management strategies are discussed. All patients that fail CPAP therapy would benefit from formal upper airway evaluation by the otolaryngologist to identify any obvious causes and consider site-specific surgical therapies. Patient selection is integral to ensuring successful outcomes. A multidisciplinary team is needed to manage these patients.

Effect of Nasal Continuous Positive Pressure on the Nostrils of Patients with Sleep Apnea Syndrome and no Previous Nasal Pathology. Predictive Factors for Compliance

OBJECTIVE

To evaluate the effect of continuous positive airway pressure (CPAP) on the nostrils of patients with sleep apnea-hypopnea syndrome and its impact on quality of life, and to identify predictive factors for compliance.

METHODS

Longitudinal prospective study. Thirty-six consecutive patients evaluated before and 2 months after CPAP using the following variables: clinical (eye, nose and throat [ENT] symptoms, Epworth test, anxiety/depression scales, general and rhinoconjunctivitis-specific quality of life); anatomical (ENT examination, computed tomography); functional (auditive and Eustachian tube function, nasal flow, mucociliary transport); biological (nasal cytology); and polisomnographics. The sample was divided into compliers (≥4h/d) and non-compliers (<4h/d).

RESULTS

A significant improvement was observed in daytime sleepiness (p=0.000), anxiety (P=.006), and depression (P=.023). Nasal dryness (P=.000), increased neutrophils in nasal cytology (P=.000), and deteriorating ciliary function were evidenced, particularly in compliers. No significant differences were observed in the other variables. Baseline sleepiness was the only factor predictive of compliance.

CONCLUSIONS

CPAP in patients without previous nasal pathology leads to an improvement in a series of clinical parameters and causes rhinitis and airway dryness. Some ENT variables worsened in compliers. Sleepiness was the only prognostic factor for poor tolerance.

Combined surgical treatment for severe sleep apnoea, to improve BiPAP compliance

Positive airway pressure (PAP) devices are used in the treatment of obstructive sleep apnoea syndrome (OSAS). In cases of PAP failure, many different surgical methods can be used for the treatment. The authors present an unusual case of a patient with Bi-level PAP (BiPAP)-intolerant severe OSAS who was treated with combined surgical methods. A 55-year-old man was treated with BiPAP due to OSAS; he was admitted to the clinic with nose stuffiness, respiratory distress and BiPAP adherence with tolerance and compliance problems. Septal deviation, concha hypertrophy, lateral pharyngeal band hypertrophy and Thornwaldt cyst were determined in the examination. Combined surgical methods were administered. The patient's apnoea hypopnoea index (AHI) was 72.8 in diagnostic polysomnography. Preoperative AHI was 7.3 and postoperative AHI was 2.3 while using BiPAP and, after the surgery, the BiPAP intolerance was eliminated. The authors suggest that a combination of different surgical methods would be an adjuvant treatment to increase BiPAP compliance.

Effects of topical nasal steroids and diclofenac on the nasal mucosa during hyperbaric oxygen therapy: a double-blind experimental study

We aimed to evaluate nasal mucosal changes and efficiency of nasal steroids and diclofenac on nasal mucosa during hyperbaric oxygen (HBO) treatment. Forty adult Albino-Wistar rats were randomized into four groups. Group 1 (control group) (n = 10) not exposed to hyperbaric or enhanced oxygen concentrations; group 2 (HBO group) (n = 10) underwent only HBO treatment; group 3 (n = 10) received HBO and intranasal mometasone furoate (10 μl/day); group 4 (n = 10) treated with HBO and diclofenac sodium (10 mg/kg/day ip). Specimens of nasal mucosa were collected after sacrificing and dissection of animals. The specimens were processed for light microscopic evaluation, and then evaluated histopathologically for fibroblastic proliferation and inflammation. Regarding the scores of inflammation, the level of inflammation in the control group was significantly less severe than the other groups (p < 0.05). Evaluation of the fibrosis scores showed that the scores of both groups 2 and 4 were significantly increased (p < 0.05). There were no statistically significant differences between groups 2, 3, and 4 as for fibrosis and inflammation (p > 0.05). Chronic HBO treatment induced mild inflammation of the nasal mucosa. These effects cannot be prevented adequately by administration of nasal steroids and diclofenac.

Effects of heated humidification on nasal inflammation in a CPAP rat model

BACKGROUND

Rhinitis is a potential side effect of nasal continuous positive airway pressure (nCPAP). Heated Humidification (HH) is applied to treat rhinitic symptoms, but its usefulness is controversial. Confounding factors such as previous rhinitis or nasal obstruction make it difficult to draw definitive conclusions. Animal models could therefore be useful.

OBJECTIVES

To study the effects of HH as a mechanism that may reduce nasal inflammation during nCPAP application in the presence or absence of an oral leak (OL).

METHODS

Prospective controlled animal study. Setting I: Sixty Sprague-Dawley rats were distributed into noCPAP (naïve), sham-CPAP with HH, 5 and 10cm H(2)O nCPAP, and 10cm H(2)O nCPAP with HH for 5h. Setting II: Thirty-three rats were exposed to nCPAP, nCPAP with a controlled OL, and nCPAP with controlled OL and HH (n=11 each). The degree of nasal inflammation was assessed by directly evaluating the percentage of neutrophils in the nasal mucosa.

RESULTS

Percentage of neutrophils was higher after 5h of 10cm nCPAP compared to the control group (0.96+/-0.26% vs. 0.18+/-0.05%; p=0.001). When HH was applied, the percentage of neutrophils did not differ from that observed in the nCPAP group. The addition of a controlled OL, did not show significant differences in the neutrophils count compared to nCPAP alone (0.75+/-0.19% vs. 0.83+/-0.29%; p=0.70). Moreover, the application of HH to the rat with OL did not change the percentage of neutrophils.

CONCLUSIONS

HH applied to an acute rat model of nCPAP with and without a controlled OL does not seem to reduce nasal inflammation.

Morbidity due to obstructive sleep apnea: insights from animal models

PURPOSE OF REVIEW

Obstructive sleep apnea (OSA) is a prevalent disorder with clinically well known mid-term and long-term consequences. It is difficult, however, to investigate the mechanisms causing morbidity in OSA from human studies, owing to confounding factors in patients. Animal research is useful to analyze the various injurious stimuli--intermittent hypoxia/hypercapnia, mechanical stress and sleep disruption--that potentially cause OSA morbidity. This review is focused on the most recent advances in our understanding of the consequences of OSA, achieved as a result of animal models.

RECENT FINDINGS

Animal research has improved our knowledge of various aspects of the cardiovascular consequences of OSA: myocardial damage, left ventricular dysfunction, vasoconstriction, hypertension and atherosclerosis. The systemic and metabolic consequences of OSA--inflammation, insulin resistance, alterations in lipid metabolism and hepatic morbidity--have also been investigated with animal models. Our understanding of the mechanisms involved in the neurocognitive consequences of OSA--neuronal and brain alterations and cognitive dysfunctions--has also been improved through animal research. Moreover, animal models have recently been used to investigate the mechanisms of upper airway inflammation and dysfunction.

SUMMARY

The simple experimental models used to investigate OSA morbidity are useful for investigating isolated mechanisms. However, more complex and realistic models incorporating the various injurious challenges characterizing OSA are required to more precisely translate the results of animal research to patients and to design potentially preventive and therapeutic strategies.