Older individuals have increased oro-nasal breathing during sleep

Transcription

1 Eur Respir J ; : DOI: 1.113/ Prited i UK all rights reserved Copyright #ERS Jourals Ltd Europea Respiratory Joural ISSN Older idividuals have icreased oro-asal breathig durig sleep M.R. Madroio*, E. Di Somma*, R. Stavriou*, J.P. Kirkess*,#, E. Goldfich*, J.R. Wheatley*,#, T.C. Amis*,# Older idividuals have icreased oro-asal breathig durig sleep. M.R. Madroio, E. Di Somma, R. Stavriou, J.P. Kirkess, E. Goldfich, J.R. Wheatley, T.C. Amis. #ERS Jourals Ltd. ABSTRACT: Breathig route durig sleep has bee studied very little, however, it has potetial importace i the pathophysiology of sleep disordered breathig. Usig overight polysomography, with separate asal ad oral thermocouple probes, data were obtaied from 1 subjects (sorers ad osorers; 5 male ad 1 female; aged yrs). Awake, upright, ispiratory asal resistace (R) was measured usig posterior rhiomaometry. Each 3-s sleep epoch (ot affected by apoeas/hypopoeas) was scored for presece of asal ad/or oral breathig. Overight, seve subjects breathed asally, oe subject oro-asally ad the remaider switched betwee asal ad oro-asal breathig. Oral-oly breathig rarely occurred. Nasal breathig epochs were (9.7) per cet of total sleep epochs (%TSE; media (iterquartile rage)), a value ot sigificatly differet to that for oro-asal (TSE:.1 (.)%). Oro-asal breathig was ot related to sorig, sleep stage, posture, body mass idex, height, weight, R (.19 (1.77) cm H O?L -1?sec -1 ) or sex, but was positively associated with age. Subjects o yrs were approximately six times more likely tha youger subjects to sped w5% of sleep epochs utilisig oro-asal breathig. Ageig is associated with a icreasig occurrece of oro-asal breathig durig sleep. Eur Respir J ; : *Ludwig Egel Cetre for Respiratory Research, Dept of Respiratory Medicie, Westmead Hospital, ad # Uiversity of Sydey, New South Wales, Australia. Correspodece: T.C. Amis, Ludwig Egel Cetre for Respiratory Research, Westmead Hospital, Westmead, New South Wales, 15 Australia. Fax: terecea@westgate.wh.usyd.edu.au Keywords: Ageig breathig route sleep Received: Jauary 1 3 Accepted after revisio: Jauary The study was supported by the Natioal Health ad Medical Research Coucil of Australia Durig wakefuless, chages i breathig route (i.e. asal versus oral breathig) are most otably associated with oral augmetatio of breathig durig exercise. However, breathig via the ose or mouth, or a combiatio of both, is also ecoutered durig sleep [1]. Furthermore, the breathig route may be a cotributig factor i the occurrece of sleep disordered breathig (SDB). For example, it has bee reported that subjects with more mouth breathig durig sleep ted to experiece more episodes of apoea tha those with predomiatly asal breathig [1]. I additio, asal obstructio, which may predispose to mouth breathig, has also bee liked to SDB []. Theoretically, a high asal resistace should be associated with lower itralumial pressures durig ispiratio, thus favourig upper airway arrowig ad/or collapse. Switchig breathig route from asal to oral or oro-asal may help to ameliorate this effect sice, depedig o the degree the mouth is opeed, oral airway resistace ca be lowered to values well below that of the asal passages [3]. However, a switch to oral route breathig may, i itself, predispose the upper airway to collapse sice a umber of upper airway muscles have route-depedet respiratory-related activity [ ]. MEURICE et al. [7] have also reported that opeig the mouth durig sleep icreases upper airway collapsibility, while breathig through the mouth also has the potetial to dry the upper airway mucosa, ehacig collapsibility ad icreasig adhesive effects []. There have bee oly two previous quatitative studies of breathig route durig sleep, both usig a partitioed face mask ad peumotachographs. I a study of 1 subjects, GLEESON et al. [1] foud that, durig sleep, older males breathed a greater proportio of total vetilatio via the mouth tha females ad youger males. More recetly, FITZPATRICK et al. [9] studied 1 healthy subjects (all with ormal levels of awake asal resistace values) ad foud a ihaled vetilatio oral fractio of y% durig sleep. I the preset study, the authors aimed to documet breathig route usage durig sleep i a larger group of osorers ad sorers of both sexes ad to examie the relatioship betwee breathig route durig sleep ad a rage of athropometric ad sleep-related parameters. Study subjects Materials ad methods Breathig route durig sleep was moitored i 3 adult subjects who voluteered for polysomographic studies of breathig ad/or sorig durig sleep. I the course of the study, two subjects were diagosed with obstructive sleep apoea ad were excluded, leavig 1 subjects for aalysis. Sevetee of these subjects reported a history of habitual sorig. Athropometric data, icludig age, height, weight, body mass idex (BMI), ethic origi ad sex were obtaied for all subjects. The study was approved by the Wester Sydey Area Health Service Huma Ethics Committee. Study desig Breathig route data durig sleep were obtaied for each subject from a sigle overight polysomographic study

2 7 M.R. MADRONIO ET AL. performed i a sleep laboratory (refer to Polysomography sectio). Ispiratory asal airflow resistace (R:. L?sec -1 ) i the upright seated posture was also measured durig wakefuless i each subject withi h of the sleep study (refer to Nasal resistace sectio). Relatioships betwee the occurrece of asal, oral or oro-asal breathig durig sleep ad athropometric factors, R ad polysomographic variables were the examied usig statistical modellig techiques (refer to Data aalysis sectio). Polysomography Routie sleep variables were recorded usig stadard polysomography. Data recorded icluded: electro-ecephalogram; electrocardiogram; electrooculogram; submetal ad diaphragmatical electromyograms; arterial oxyge saturatio; impedace plethysmography (P/N 7-9-; Compumedics, Abbotsford, Australia); body positio; ad asal pressure (1 Nasal Caula; Salter Labs Ic., Arvi, CA, USA). The tip of the asal caula was modified for each study by clippig 3 mm from the tip to icrease the crosssectioal area for detectio of asal pressure. The asal caula was iserted i the opeig of the ostrils. Breathig route was recorded usig a dual-chael asal/ oral thermocouple (F-ONTA; Grass, West Warwick RI, USA). The thermocouple was placed o top of the asal caula ad both were taped to the sides of the face to miimise movemet durig sleep. Sorig was recorded usig either a microphoe (NL-5 Type ; RION Co., Ltd, Tokyo, Japa) suspeded cm directly above the subject9s mouth or a exteral tracheal microphoe (P/N ; Compumedics) attached directly to the right side of the subject9s eck. All moitored parameters were recorded directly o a computer usig proprietary software (W Series, V; Compumedics). There was o cross-cotamiatio betwee the oral ad asal thermocouple sigals, as cofirmed by havig each subject perform short periods (five breaths) of exclusive asal ad exclusive oral breathig i the supie ad right lateral postures immediately prior to lights out. Nasal resistace For each subject, R was measured durig wakefuless i the upright, seated posture usig stadard posterior rhiomaometry [1] withi h of polysomography. Data aalysis Each sleep study was sleep staged for 3-s epochs usig RECHSHTAFFEN ad KALES [11] criteria. Respiratory evets (respiratory disturbace idex (RDI): umber of apoeas plus the umber of hypopoeas per hour of sleep) were idetified usig America Academy of Sleep Medicie criteria [1]. Epochs cotaiig such evets, as well as arousals, movemets or sigal artefacts were excluded from aalysis ( 1% of total epochs for idividuals). Route of breathig was assessed by usig the asal ad oral thermocouple sigals to classify each 3-s epoch as either a asal, oral or oro-asal breathig epoch. Nasal breathig epochs were defied as epochs cotaiig o3 cosecutive phasic sigals o the asal thermocouple chael oly. Oral breathig epochs were defied as epochs cotaiig o3 cosecutive phasic sigals o the oral thermocouple chael oly. Oro-asal breathig epochs cotaied o3 cosecutive phase liked sigals o both the asal ad oral thermocouple chaels. Each epoch was also classified as either a osorig epoch or a sorig epoch. Sorig epochs were defied as epochs cotaiig o3 cosecutive soud peaks i phase with ispiratio (determied usig the P-asal sigal) ad with a peak amplitude of o5 db above the backgroud soud level (y39 5 db for idividual study ights). The occurrece of asal breathig, oral breathig, oroasal breathig ad sorig epochs was expressed as a percetage of the total sleep epochs (TSE) aalysed. Similar data were geerated for sleep stage ad body positio. Data for left ad right lateral decubitus were combied. Miimal data were obtaied for the proe posture, cosequetly, this body positio was ot icluded i the aalysis. Frequecy histograms were developed for each measured parameter. Data were also expressed as a media ad iterquartile rage (IR). Very little oral-oly breathig (.%TSE for idividuals; refer to Results sectio) was detected, cosequetly, these data were ot icluded i ay further aalyses. Data were compared usig the Wilcoxo siged rak test. Aalysis of the relatioship betwee breathig route ad other measured parameters was expressed i terms of their associatio with the occurrece of oro-asal breathig epochs (%TSE). Because of the relative absece of oral-oly breathig, results for asal-oly breathig were the reverse of those for oro-asal breathig. Statistical modellig was performed i a three-stage procedure. First, correlative aalyses (Pearso9s correlatio coefficiet, r) were performed to search for sigificat uivariate relatioships. Stepwise multivariate regressio aalysis was the used to test for idepedet relatioships. Logistic regressio aalysis was also used to examie the extet to which age o yrs predicted the occurrece of oroasal breathig epochs durig sleep. A p-value of v.5 was cosidered sigificat. Athropometric data Results Figure 1a d summarises the athropometric characteristics of the study cohort that cotaied 35 persos of White ethic origi, six persos of Asia ethic origi, 5 males ad 1 females. Nasal resistace For the group (=39), awake ispiratory R was. (1.) cm H O?L -1?sec -1 with values ragig.. cm H O?L -1?sec -1 (fig. 1e). Polysomographic variables Frequecy distributio histograms for polysomographic variables versus umber of subjects are show i figure 1f l. Most subjects slept reasoably well, with total sleep time ragig mi. For the group,.9 (.) %TSE was spet i orepetative eye movemet (NREM) Stage I sleep; 57.9 (1.) %TSE i NREM Stage II; 1. (7.) %TSE i NREM Stage III;. (13.) %TSE i NREM Stage IV; ad 15.3 (1.5) %TSE i repetitive eye movemet sleep. Sleep time was equally divided betwee the supie (5.9 (5.3) %TSE) ad lateral body positios (1. (.) %TSE; p=.51). Sorig souds were detected i 7 subjects (fig. 1l). All subjects had a RDI v1?h -1.

3 ROUTE OF BREATHING DURING SLEEP 73 a) 1 b) 1 c) 7 Subjects d) Age yrs 1 1 Weight kg e) 1 15 f) Height cm Subjects g) BMI kg m R cmh O L -1 s -1 h) 1 1 NREM Stage 1 %TSE i) Subjects j) 1 NREM Stage %TSE 1 k) 1 NREM Stage 3 %TSE 1 1 NREM Stage %TSE l) 5 1 Subjects REM %TSE 1 Supie posture %TSE 1 Sorig %TSE Fig. 1. Frequecy distributio histograms i 1 subjects for a d) athropometric factors, e) asal resistace, f j) sleep architecture, k) supie sleep posture ad l) occurrece of sorig epochs. Note the frequecy distributio histogram for lateral posture is the exact reverse of that for the supie posture ad is ot show. TSE: total sleep epochs; R: asal resistace at. L?s -1 ; BMI: body mass idex; REM: rapid eye movemet sleep; NREM: orapid eye movemet sleep. Breathig route durig sleep Figure shows the raw data demostratig asal ad oroasal breathig sigals durig differet periods of NREM sleep i oe subject. Figure 3a c summarises the occurrece of asal, oral ad oro-asal breathig epochs for the group. Durig sleep, 11 subjects breathed exclusively or almost exclusively via the asal route throughout the ight, while six subjects breathed exclusively or almost exclusively oro-asally all ight. The remaiig subjects switched their breathig route betwee asal-oly breathig ad oro-asal breathig throughout the ight. There was o fixed patter associated

4 7 M.R. MADRONIO ET AL. EOG (L) uv a) b) EOG (R) uv EEG (C 3, A ) uv EEG (O, A 1 ) uv EMG sm uv Sa,O % 1 75 V uv Vo uv Soud db ABD mvmt mv 3 RC mvmt mv Positio F B L R 17.5 s 17.5 s Fig.. Raw data recorded durig orapid eye movemet sleep i the supie posture i oe subject durig a) asal-oly breathig ad durig b) oro-asal breathig. Note that sorig occurs durig both asal-oly breathig ad oro-asal breathig. EOG: electrooculogram; L: left; R: right; EEG: electroecephalogram; EMG sm: submetal electromyogram; Sa,O : arterial oxyge saturatio; V: asal airflow; Vo: oral airflow (thermocouple); Soud: microphoe; ABD mvmt: abdomial movemet (impedace plethysmography); RC mvmt: chest movemet (impedace plethysmography); Positio: body positio; F: frot; B: back. Ispiratio is upwards i V, Vo, ABD ad RC mvmt. EEG electrodes amed accordig to positio: C: cetral; O: occipital; A: auricular; eve umber: right side; odd umber: left side. with breathig route chages with cosiderable itra- ad iter-subject variability i the duratio (every few miutes to y -mi itervals) of asal or oro-asal breathig periods before a switch to the alterate patter was iitiated. Exclusive oral breathig was rare, occurrig i oly three subjects (.3. %TSE). Ideed, of the,9 epochs classified for breathig route, oly 7 of these were oral-oly breathig epochs. For the group, the occurrece of asal breathig (55. (9.) %TSE) was ot sigificatly differet to that for oro-asal breathig (.1 (.) %TSE; p=.1). Breathig route durig sorig Both asal ad oro-asal breathig occurred durig sorig epochs (fig. ), however, the relative occurrece rates varied widely for idividuals. For the group, 5.5 (.7) % of sorig epochs were also oro-asal breathig epochs. Uivariate aalysis Whe the data were examied for uivariate relatioships, the occurrece of oro-asal breathig epochs durig sleep (i.e. oro-asal breathig epochs %TSE) correlated positively with age (r=.; pv.1) ad BMI (r=.33; p=.3), teded to correlate positively with the occurrece of sorig epochs (r=.9; p=.), ad correlated egatively with the occurrece of osorig epochs (r=-.3; p=.3). Multivariate regressio aalysis Stepwise multivariate regressio aalysis revealed that the oly idepedet predictor for the occurrece of oro-asal breathig epochs durig sleep was age (oro-asal breathig epochs: %TSE=1.17 yrs -.71; adjusted r =.15; pv.1; fig. ). Logistic regressio aalysis Table 1 shows the occurrece of oro-asal breathig epochs wadv5 %TSE for subjects with age o yrs adv yrs. Logistic regressio aalysis cofirmed that a age of o yrs was a sigificat predictor for a occurrece ofw5 %TSE for oro-asal breathig epochs durig sleep (p=.1; odds ratio=5.; 95% CI: 1.5 ). Discussio The major fidig i this study was that sorers ad osorers utilised both asal ad oro-asal breathig durig sleep. Furthermore, most subjects used asal breathig throughout the ight, but added oral breathig itermittetly, such that, for the group, the occurrece of oro-asal breathig sleep epochs was ot sigificatly differet to that for asal-oly breathig. Pure oral breathig durig sleep occurred rarely. Sorig occurred with both asal ad oroasal breathig. Age was the oly idepedet predictor for

5 ROUTE OF BREATHING DURING SLEEP 75 a) 1 1 Subjects 1 Oro-asal breathig epochs %TSE b) Age yrs 3 Fig.. Relatioship betwee age ad occurrece of oro-asal breathig epochs durig sleep. : regressio lie; - - -: 95% CI limits for predictio equatio. Subjects c) Subjects breathig route durig sleep. Subjects o yrs of age were approximately six times more likely tha youger subjects to sped w5% of the ight utilisig oro-asal breathig. The authors moitored breathig routes usig a dual chael thermocouple device that sesed asal ad oral airflow separately. Such devices have bee used extesively for moitorig airflow durig sleep [13 15]. Potetial disadvatages associated with the use of these devices iclude failure to sample airflow adequately because of iappropriate positioig of sesors or dislodgmet durig sleep, crosscotamiatio from the alterate pathway, ad poor sesitivity to chages i airflow because of oliear respose characteristics [15]. I the preset study, the thermocouple leads were supported by hookig them behid the ears ad Breathig route %TSE Fig. 3. Frequecy distributio histograms for a) occurrece of asaloly, b) oral-oly ad c) oro-asal breathig epochs durig sleep i 1 subjects. TSE: total sleep epochs. 1 1 tapig them to the subject9s cheeks. The absece of crosscotamiatio was verified at the commecemet of each study by havig the subject volutarily breathe via the asal ad oral routes separately ad esurig that o sigal was detected for the opposite route. Chages i sesor positio durig the ight, however, remai a potetial complicatio. It is well established that thermocouple devices have limitatios for the detectio of airflow because of their oliear respose characteristics [1]. However, the pricipal problem here is poor sesitivity to chages i airflow at higher airflows [15]. I fact, these devices have high sesitivity for detectig the presece (or absece) of airflow [1]. Thermocouple sigals were used i the preset study oly for this latter purpose ad o attempt was made to quatitate the level of airflow preset. Thermal-based devices for the detectio of respiratory airflow sese chages i temperature associated with exposure to ihaled or exhaled gas. Therefore, should ispiratio ad expiratio take place via differet breathig routes the iterpretatio of a thermocouple sigal as represetig breathig via a sigle route may be cofouded. Thus, i the cotext of the preset study, breathig patters that ivolved, for example, ihalatio via the ose ad exhalatio via the mouth, would be classified as oro-asal breathig if a asal ad oral route sigal was preset or oral oly if there were oly a oral sigal. This latter possibility is ulikely sice oral-oly breathig was ecoutered rarely. The former patter, however, would have bee icluded i the preset occurrece rate for oro-asal breathig. Istrumetatio with asal caulae has bee show to icrease asal resistace i some idividuals, particularly those with a high baselie asal resistace [1]. Cosequetly, it is possible that the breathig route i the preset study was Table 1. Subject age ad occurrece of oro-asal breathig epochs durig sleep Oro-asal breathig epochs %TSE Number of subjects Age v yrs Age o yrs f5% 1 w5% 13 Total umber of subjects 19 %TSE: per cet total sleep epochs.

6 7 M.R. MADRONIO ET AL. iflueced by the presece of the asal pressure caulae ad thermocouple probes. However, this would seem ulikely i the curret study9s subject group sice baselie asal resistace did ot emerge as a sigificat predictor of breathig route durig sleep. The preset authors foud that most subjects used the asal route for breathig while asleep, either exclusively or i combiatio with oral breathig. These fidigs are i geeral agreemet with other studies o this topic [1, 9], usig a dual compartmet face mask with attached peumotachographs to moitor asal ad oral airflow durig sleep. While the authors have demostrated a y %TSE occurrece of oro-asal breathig durig sleep, fidigs reported by FITZPATRICK et al. [9] suggest that the magitude of the oral fractio of miute vetilatio associated with this patter of breathig may be relatively small (y %), i.e. although oroasal breathig occurs frequetly durig sleep most of the miute vetilatio remais via the asal route. I the study by GLEESON et al. [1] they foud that asal breathig always cotributed a miimum of oe third of the total vetilatio durig sleep but the cotributio of oral breathig varied. GLEESON et al. [1] did ot observe ay oral-oly breathig. Sice their subjects were ecumbered by a face mask the issue remais as to the extet to which this istrumetatio altered the breathig route. However, the preset study has ow demostrated a similar fidig based o the occurrece of asal ad oro-asal breathig epochs, ad achieved this without istrumetatio of the face, beyod the attachmet of sesors to the ski. The curret authors were iterested i examiig what factors might be associated with the oral augmetatio of asal breathig durig sleep ad, therefore, aalysed the curret data for sigificat associatios betwee both athropometrical ad polysomographical variables, ad the occurrece of oro-asal breathig epochs. Positive uivariate relatioships were foud betwee oro-asal breathig epochs durig sleep ad both age ad BMI, while a egative associatio with osorig epochs, ad a borderlie sigificat positive associatio with sorig epochs, were also demostrated. Weight ad height, each cosidered separately, ad ethic origi (White or Asia), together with sleep stage ad sleepig posture (back versus side) all showed o associatio with breathig route. Multivariate regressio aalysis demostrated that age was the oly idetified idepedet predictor of oro-asal breathig durig sleep. The uivariate associatios with BMI ad osorig reflected the tedecy for older idividuals i the curret study9s cohort to have higher levels of BMI ad for youger idividuals ot to sore. The associatio betwee age ad oro-asal breathig explaied oly y15% of the variace. Cosequetly, while there was a sigificat positive associatio betwee age ad oro-asal breathig durig sleep, the effect was relatively weak ad clearly there must be other iflueces that were ot measured i the preset study. Nevertheless, the relatioship demostrated i fig. predicts a icrease i the occurrece of oroasal breathig epochs durig sleep ofy1 %TSE for each age year. I the study by GLEESON et al. [1], a much stroger positive correlatio (r=.3) betwee oral breathig durig sleep ad age i males oly was foud. While differeces i correlatio stregth betwee the two studies might reflect differeces i study size ad subject characteristics, i the preset study sex was ot associated with breathig route durig sleep. This discrepacy betwee the two studies may relate to the fact that the study by GLEESON et al. [1] cotaied oly seve males ad seve females ad had a wider rage of ages ad more idividualsw yrs of age i the male group tha i the female group. Sice multivariate aalysis was ot performed i the study by GLEESON et al. [1] this fidig may, i fact, reflect a age, rather tha a sex effect. The mechaisms likig age ad oro-asal breathig durig sleep are ot kow. GLEESON et al. [1] suggested that the effect may be related to a icreased R i males. However, i the preset study there was o associatio betwee awake R values ad breathig route durig sleep. The media value for ispiratory R i the preset study group was.19 cm H O?L -1?sec -1, a value withi the ormal rage for the curret authors9 laboratory. The lack of a relatioship betwee R ad breathig route would, however, ot be likely to apply at high R levels. I additio, R i the upright posture ad durig wakefuless was measured ad this value may ot be reflective of that occurrig i the supie posture ad durig sleep. However, for subjects with a relatively ormal R, breathig route durig sleep is ot predicted by awake upright R. Therefore, R does ot appear to explai the relatioship betwee breathig route ad age, ad other mechaisms must play a role. Such effects might iclude ageig effects o jaw ad upper airway muscle activity durig sleep ad/or loss of skeletal muscle stregth. It should be oted, however, that the relatioship is weak ad clearly there are other factors ivolved that are ot (at least ot tightly) related to age. Mouth opeig durig sleep has bee associated with icreased upper airway collapsibility eve i healthy subjects [7]. This effect is thought to be mediated via a combiatio of upper airway arrowig ad decreased efficiecy of upper airway dilator muscle actio [7]. I the preset study the occurrece of sorig epochs teded to correlate with the occurrece of oro-asal breathig epochs, while there was a egative relatioship betwee osorig epochs ad oroasal breathig (i.e. absece of sorig was associated with the absece of oro-asal breathig). However, both these relatioships were ot sigificat whe corrected for the effect of age ad, thus, probably reflect a tedecy for the sorers to be older tha the osorers. Mouth breathig ad sorig have bee previously liked temporally ad a associatio betwee the two postulated [1]. However, it has also bee recogised for some time that both asal ad oro-asal sores occur [17]. The preset study suggests that oro-asal breathig is ot a prerequisite for sorig ad that while the occurrece of oro-asal ad asal sorig varies widely betwee idividuals, o a group basis, asal ad oro-asal sorig occur with approximately equal frequecy. The presece of sorig i the curret study9s subjects suggests that some breaths may have bee characterised by ispiratory flow limitatio (IFL) ad icreased upper airway resistace (UAR). The extet to which this occurred was ot assessed i the preset study. However, the lack of a demostrated relatioship betwee sorig ad breathig route makes it ulikely that IFL or UAR iflueced breathig route i the study9s subjects sice the sorig epochs are more likely to be characterised by IFL ad icreased UAR. This study, alog with previous ivestigatios [9, 1], demostrates that the oral breathig route is utilised durig sleep i some subjects. Cosequetly, the use of asal breathig moitorig (e.g. P-asal) aloe to moitor sleep disordered breathig may be potetially cofouded by the occurrece of oral route breathig. To summarise, the authors demostrated that sorig ad osorig subjects utilise both asal ad oro-asal, but rarely oral-oly, breathig durig sleep. The occurrece of oro-asal breathig sleep epochs icreases with icreasig age ad is ot related to: sex; White or Asia ethic origi; height; weight; body mass idex; awake asal resistace (withi the ormal rage); sleep stage; sleepig positio or the occurrece of sorig. The authors coclude that ageig is associated with a icreased oro- asal breathig durig sleep.

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