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The study investigated the role of alpha2-adrenergic receptors of the caudal raphe region in the sympathetic and cardiovascular responses to the acute intermittent hypercapnia (AIHc). Urethane-anesthetized, vagotomized, mechanically ventilated Sprague-Dawley rats (n=38) were exposed to the AIHc protocol (5×3 min, 15 % CO2+50 % O2) in hyperoxic background (50 % O2). alpha2-adrenergic receptor antagonist-yohimbine was applied intravenously (1 mg/kg, n=9) or microinjected into the caudal raphe region (2 mM, n=12) prior to exposure to AIHc. Control groups of animals received saline intravenously (n=7) or into the caudal raphe region (n=10) prior to exposure to AIHc. Renal sympathetic nerve activity (RSNA), mean arterial pressure (MAP) and heart rate (HR) were monitored before exposure to the AIHc protocol (T0), during five hypercapnic episodes (THc1-5) and at 15 min following the end of the last hypercapnic episode (T15). Following intravenous administration of yohimbine, RSNA was significantly greater during THc1-5 and at T15 than in the control group (P0.05). When yohimbine was microinjected into the caudal raphe region, AIHc elicited greater increases in RSNA during THc1-5 when compared to the controls (THc1: 138.0+/-4.0 % vs. 123.7+/-4.8 %, P=0.032; THc2: 137.1+/-5.0 % vs. 124.1+/-4.5 %, P=0.071; THc3: 143.1+/-6.4 % vs. 122.0±4.8 %, P=0.020; THc4: 146.1+/-6.2 % vs. 120.7+/-5.7 %, P=0.007 and THc5: 143.2+/-7.7 % vs. 119.2+/-7.2 %, P=0.038). During THc1-5, significant decreases in HR from T0 were observed in all groups, while changes in MAP were observed in the group that received yohimbine intravenously. These findings suggest that blockade of the alpha2-adrenegic receptors in the caudal raphe region might have an important role in sympathetic responses to AIHc.

Objectives/Introduction Our group previously reported that excluding item assessing tiredness (T) might improve the overall predictive value of STOP-Bang in one population. The current research is aimed to investigate the role of the aforementioned item T of the STOP-Bang questionnaire among populations in different European geographic regions, while considering the possible moderating role of age and gender. Methods A study has been conducted in 3 European Sleep medicine centers - in Split, Croatia ; Thessaloniki, Greece ; and Izmir, Turkey. A total of 9154 respondents were included, of whom 2364 in Greece, 3638 in Turkey and 3152 in Croatia. Among them, 6345 respondents (69.4%) were men. 1351 respondents were younger than 40 years, with 6684 respondents aged 40 to 69 years, and 1014 respondents were older than 70 years of age. All patients in Greece were assessed with the use of polygraphy, all patients in Turkey were assessed with full-night polysomnography, and Croatian patients were assessed with polysomnography (n=1043) or polygraphy (n=2109). Results Specifically, among Greek patients, the exclusion of item T resulted in a decrease of STOP-Bang sensitivity from 97.6% to 94.2%, and an increase in specificity from 20.6% to 34.7%. Among patients in Turkey, the exclusion of the item T resulted in decreased sensitivity from 98.2% to 93.4%, while increasing specificity from 12.9% to 32.3%. In Croatian respondents, the exclusion of item T resulted in decreased sensitivity from 92.4% to 86.7% and increased specificity from 46.6% to 63.7%. Change in sensitivity and specificity was recognized in respondents below 40 years of age, 40 to 69 years of age and in groups of respondents older than 70 years. In all three investigated populations, a larger decrease in the sensitivity of the STOP-Bang questionnaire was recognized among female respondents when item T was excluded from the final sum, whereas the specificity increased. Conclusions The exclusion of item T in the final sum of the STOP-Bang questionnaire decreased the sensitivity of questionnaire in the recognition of OSA in all three investigated populations, but enabled an overall larger increase in the specificity. The change in sensitivity was more pronounced in female respondents.

Objectives/Introduction The search for factors predisposing to continuous positive airway pressure (CPAP) adherence remains inconsistent. Therefore, we aimed to investigate the role of oxygen desaturation severity expressed as the slope of the oxygen desaturation curve (Slope Index, SI) in short-term CPAP adherence prediction and possible cut-off values of SI in distinguishing good and poor CPAP adherers. Methods A retrospective study was performed on 70 CPAP-treated patients with severe obstructive sleep apnea (OSA). SI was calculated as the averaged quotient of difference between blood oxygen saturation level before and after the obstructive apnea and the event duration throughout the night. Apnea-Hypopnea Index (AHI) was defined as a sum of apneas and hypopneas per hour of sleep. Good short-term CPAP adherence was defined as CPAP usage for ≥4 hours/night on ≥70% of nights during first three months of therapy. Results Following logistic regression (R2=16.7% ; p=0.010), a lower SI was a predictor of good CPAP adherence during first three months of CPAP therapy (OR=0.004 ; p=0.019). As a predictor of good CPAP adherence during initial therapy, SI achieved AUC value of 0.650 (p=0.032) with the highest predictive value based on Youden index for 0.465 cut-off. The AUC value for AHI in the prediction of good CPAP adherence was not significant (p=0.228). Using the cut-off SI value of 0.465, patients were classified into the group with SI below (n=51) and above 0.465 (n=19). During first three months of CPAP therapy, average CPAP usage hours, percentage of nights with CPAP usage and nights with CPAP usage ≥4 hours were significantly higher in the group with SI below 0.465 (p

Slaven Lupi-Ferandin,1 Sandro Glumac,2 Nancy Poljak,3 Tea Galic,4,5 Natalija Ivkovic,6 Ognjen Brborovic,7 Renata Pecotic,5,6 Zoran Dogas5,6 1Department of Maxillofacial and Oral Surgery, University Hospital of Split, Split, Croatia; 2Department of Anesthesiology and Intensive Care, University Hospital of Split, Split, Croatia; 3Study of Dental Medicine, School of Medicine, University of Zagreb, Zagreb, Croatia; 4Study of Dental Medicine, School of Medicine, University of Split, Split, Croatia; 5Department of Neuroscience, School of Medicine, University of Split, Split, Croatia; 6Sleep Medicine Center, School of Medicine, University of Split, Split, Croatia; 7Department of Social Medicine and Organization of Health Care, Andrija Stampar School of Public Health, School of Medicine, University of Zagreb, Zagreb, CroatiaCorrespondence: Zoran DogasDepartment of Neuroscience, School of Medicine, University of Split, Soltanska 2, Split 21000, CroatiaTel +385 21557903Fax +385 21557895Email zdogas@gmail.comAim: To evaluate the health-related life quality of patients after surgically treated midface fractures.Patients andMethods: This retrospective cohort study compared the 36-Item Short Form Health Survey (SF-36) scores of 42 male patients following surgically treated maxillary or zygomatic fractures with the reported normative data of the SF-36 for the Croatian population.Results: The current study showed that the health-related life quality of surgically treated patients was comparable to similar age, gender, and regional demographics in the Croatian population norm. However, we revealed a significant deterioration of the “Emotional wellbeing” domain in younger patients (P = 0.03) and a severely affected domain of “Physical functioning” in older patients (P = 0.049).Conclusion: There was a significant negative psychological impact from facial trauma on younger patients. In contrast, older patients were more prone to physical impairment. Therefore, follow-up visits are an opportunity to screen and refer younger patients to mental health services in a timely manner to prevent severe psychological difficulties and an opportunity to identify older patients who require physical therapy.Keywords: quality of life, patient outcome assessment, maxillary fractures, zygomatic fractures, surgery, oral

Linda Lusic Kalcina, Ivana Pavlinac Dodig, Renata Pecotic, Maja Valic, Zoran Dogas Department of Neuroscience, Split Sleep Medicine Center, University of Split School of Medicine, Split, CroatiaCorrespondence: Zoran DogasDepartment of Neuroscience, Split Sleep Medicine Center, University of Split School of Medicine, Soltanska 2, Split 21000, CroatiaTel +38521557905Fax +38521557955Email zdogas@mefst.hrPurpose: Determinants of obstructive sleep apnea (OSA) are hypoxemia and hypercapnia, as well as (micro) arousals from sleep, resulting in chronic sleep fragmentation, sleep deprivation, and excessive daytime sleepiness (EDS). All of the above-mentioned factors might contribute to psychomotor impairment seen in OSA patients. Additionally, this study aimed to assess the contribution of BMI, age, EDS assessed with Epworth sleepiness scale (ESS), and severity of OSA assessed with apnea-hypopnea index (AHI) to the reaction time on chronometric tests in OSA patients and controls. It is hypothesized that moderate and severe OSA have adverse effects on reaction time of perception to visual stimulus, of solving simple arithmetic operations, and of psychomotor limbs coordination assessed by chronometric psychodiagnostic test battery.Patients and Methods: This study was conducted on 206 male participants; 103 of them had moderate or severe OSA diagnosed by whole-night polysomnography/polygraphy. Control participants (N=103), matched to patients with OSA by age and BMI, had no reported OSA in their medical history, no increased risk for OSA, nor EDS. All participants were assessed with three chronometric psychodiagnostic tests, measuring thereaction time of perception to visual stimulus, of solving simple arithmetic operations, and of psychomotor limbs coordination.Results: Participants from theOSA group achieved impaired results compared to control participants in minimum single task solving time in speed of solving simple arithmetic operations (3± 0.9 and 2.6± 0.6, P< 0.001), and in minimum solving time of a single task in complex psychomotor limbs coordination (0.69± 0.2 and 0.61± 0.1, P=0.007). Regression analysis revealed no significant contribution of daytime sleepiness to the results achieved in each of the tests.Conclusion: It is concluded that severe OSA impaired speed of perception, convergent, and operative thinking. Moreover, it is suggested that EDS did not contribute to poor psychomotor outcome in patients with OSA in thisstudy, when age was controlled for.Keywords: obstructive sleep apnea syndrome, overnight polysomnography, psychomotor performance, psychodiagnostic test, daytime sleepiness

According to PG/PSG, 474 participants had no OSA and 2658 had mild to severe OSA. The sensitivity of the STOP was 86, 5% with the specificity of 45, 3%, whereas for the STOP-BANG there was a 92, 4% sensitivity with specificity of 45, 8%. In conclusion, our findings have indicated STOP bang screening performance as extremely low in subjects older than 60 years of age, reporting very low specificity for STOP and extremely low specificity for STOP BANG questionnaire.

Objectives/Introduction: Numerous epidemiological studies have shown the varying prevalence of obstructive sleep apnea (OSA) among different age groups of the general population, with an in- creased prevalence in the elderly. Considering the expensive and time-consuming OSA diagnostic procedures, appropriate assess-ment of the OSA risk with reliable screening tools is essential. However, age-related effects on the risk for OSA and one of its hall-mark features, excessive daytime sleepiness, remain controversial. Therefore, the aim of this study was to assess the risk for OSA and daytime sleepiness in a large population sample, with regard to age and gender. Methods: A large population sample included 14606 respondents (45.32% men) from Western Herzegovina, with the median age of 32 (IQR 21–53). The respondents completed STOP questionnaire for OSA risk assessment and Epworth sleepiness scale for daytime sleepiness evaluation. Results: A total of 4273 (29%) respondents had increased risk for OSA. The risk for OSA increased with age (χ2=78 . 3 5 , p < 0.001). Male respondents had a higher risk for OSA compared to female respond-ents in younger age groups (up to 70 years) (χ2 = 11.940, p = 0.018), whereas no difference was found in advanced age group (>70 years). The proportion of respondents with excessive daytime sleepiness was significantly higher in participants with increased OSA risk com-pared to those not at risk, in all age groups (χ2 = 998.36, p < 0.001). Furthermore, a positive correlation was found between age and day-time sleepiness in the male respondents (r = 0.042, p < 0.001), but not in female respondents. Conclusions: This study performed on a large population sample demonstrated that the risk for OSA increases with advanced age. Male respondents had a significantly greater risk than females in all ages, until the age of 70. Daytime sleepiness was a prominent symp-tom among subjects with increased OSA risk in all age groups, but less pronounced in females, emphasizing the influence of gender on OSA risk and symptomatology.

The aim of this study was to investigate the relationships between SI and AHI with daytime sleepiness, sleep efficiency and comorbidity presence in severe OSA patients. A total of 111 patients who underwent whole-night polysomnography (PSG) at the Split Sleep Medicine Centre with severe OSA (AHI≥30) were included. Among PSG parameters AHI and sleep efficiency were analyzed. Daytime sleepiness was assessed by Epworth Sleepiness Scale (ESS). Arterial hypertension, diabetes mellitus type 2 (DM2) and depression were self-reported. The SI was calculated as the averaged quotient of the difference between the blood oxygen saturation before and after the obstructive apnea episode and the duration of the episode throughout the night. Both indices, SI and AHI, predicted daytime sleepiness in severe OSA patients without comorbidities. SI better predicted sleep efficiency in severe OSA patients with hypertension, as well as in the patients without depression. The slope of the oxygen desaturation curve index, as a novel OSA severity index, could help in understanding the impact of hypoxia in different OSA phenotypes.

Background. Obstructive sleep apnea (OSA) is common sleep-disordered breathing characterized by recurrent episodes of upper airway collapse during sleep with associated airflow obstruction, intermittent hypoxemia, sympathetic excitation and sleep fragmentation. Intermittent hypoxemia and sleep fragmentation may contribute to impaired cognitive and psychomotor performance. Aims. The aim of this study was to determine the effect of the custommade adjustable mandibular advancement device (MAD) on cognitive and psychomotor performance in patients with mild to moderate OSA. Methods. A total of 15 patients with mild to moderate OSA were treated with custom-made adjustable MAD and they were followed-up after 1 year of therapy. Sleep studies were performed with and without the MAD. The patients were tested on three different tests of cognitive and psychomotor performance using computer-based system Complex Reactionmeter Drenovac (CRD series) at baseline and at the time of follow-up. Results. The mean apnea-hypopnea index (AHI) decreased significantly from 22.9±5.9 at baseline, to 9.7±4.5 after 1 year of therapy (p

Obstructive sleep apnea (OSA) is the most prevalent sleep-disordered breathing caused by repetitive partial or complete interruptions of breathing during sleep, resulting in intermittent hypoxemia, sympathetic excitation and sleep fragmentation. OSA is usually thought to be worse in rapid eye movement (REM) sleep than non-REM (NREM) sleep and is considered as a REM- predominant phenomenon. There is still lack of evidence whether REM-related OSA is a specific clinical entity and how it is related to gender differences. The aim of this study was to determine if there were any differences in polysomnographic data and sleep quality between male and female patients with REM-related OSA. From the pool of 289 patients in the Split Sleep Medicine Center, a total of 62 patients with newly diagnosed REM-related OSA were prospectively recruited to the study and divided into two groups according to gender. REM-related OSA was defined as follows: apnea/hypopnea index (AHI)≥5, AHI(REM)/AHI(NREM)≥2, and REM>30 min. All patients attended a full-night, in-laboratory polysomnography using the Alice 5LE device (Philips Respironics, Eindhoven, Netherlands) and completed sleep questionnaires. Out of 62 patients with REM-related OSA there were 44 male and 18 female patients. There were no statistical differences in respiratory parameters between male and female patients. REM duration was longer in female patients (77.8±39.7 vs. 70.6±33.5 min, P

Increased psychological pressure and academic demands can lead to impaired quality and duration of sleep. Numerous studies have shown that students with more regular sleep-wake patterns report higher grade point average (GPA), whereas students with lower grades report increased daytime sleepiness as a consequence of decreased sleep duration. Among different student populations, medical students received particular attention in sleep research because of high academic demands and increased workload. Similarly, doctor of dental medicine (D.M.D.) curriculum is demanding due to both declarative and procedural learning tasks, which are impaired by sleep deprivation. The purpose of this study was to evaluate sleep habits of dental students and the relationship between sleep habits and academic performance. A self-administered questionnaire on sleep habits, academic performance and lifestyle, was administered. The final version of the questionnaire consisted of 58 questions. The participants were 447 dental students from Split University Dental Medicine School and Zagreb University Dental Medicine School of the six academic years. The subjects were classified in two groups based on academic success, as high (highest quintile, GPA > 4.3) or low academic performance (lowest quintile, GPA < 3.5) group. Our study indicated a clear association of sleep habits with self-reported academic performance of dental students. Students with high academic performance had earlier bedtimes on weekdays and weekends, earlier wake time on weekends, and shorter sleep latency, compared to students with low academic performance. Circadian rhythm with earlier bedtime and wake time sleep period appears to be of more importance than total sleep time, in respect to academic performance.

Sustained augmentation of phrenic nerve activity evoked by acute intermittent hypoxia (AIH) represents form of central nervous system plasticity, known as phrenic long term facilitation (pLTF). Previous studies have shown that pLTF is serotonin (5-HT) dependent, and systemic application of selective and non- selective 5-HT receptor antagonists could impair induction and preservation of pLTF. Microinjections of non-selective 5-HT receptor antagonist methysergide into the raphe nuclei prevented identification of specific 5-HT receptor subtype involved in modulation of pLTF at supraspinal level. Therefore, present study was preformed to determine whether blockade of 5-HT1A receptors in caudal raphe region influences induction of pLTF. Our hypothesis was that microinjections of selective 5-HT1A receptor antagonist WAY- 100635 into the caudal raphe nucleus could prevent induction of phrenic LTF after exposure to AIH. Adult, male, urethane- anesthetized, vagotomized, paralyzed and mechanically ventilated Sprague-Dawley rats were exposed to AIH protocol. Experimental group of animals (n=7) received microinjection of WAY- 100635 (1mM, 20±5 nl) into the caudal raphe nucleus, whereas control group (n=7) received microinjection of 0.9% saline (20±5 nl) into the same site. Peak phrenic nerve activity (pPNA), burst frequency (f), and respiratory rhythm parameters were analyzed during five hypoxic episodes (TH1-5), as well as at 15 (T15), 30 (T30), and 60 (T60) minutes after the end of the last hypoxic episode. In the control group, pPNA was elevated from baseline (to 172.9±17.5%, P=0.008) at 60 minutes after episodic hypoxia, indicating pLTF. Microinjections of WAY-100635 into the raphe nuclei prior to hypoxic stimulation attenuated pLTF. There was no significant decrease of pPNA from baseline (-15.4±16.9%) at T60. Microinjections of selective 5-HT1A receptor antagonist WAY-100635 into the raphe nuclei prior to episodic hypoxia exposure prevented induction of pLTF, indicating that 5-HT1A receptor activation at supraspinal level is important for induction of pLTF.

Stimulation of breathing with acute intermittent hypoxia (AIH) elicits increases in respiratory and sympathetic outflow. Previous studies have shown that AIH produces increases in respiratory and sympathetic nerve activity that last long after hypoxic stimulation have ceased. Variability of heart rate (HR) from ECG recordings has been used as a non-invasive measure of cardiac autonomic modulation. This study was performed to investigate the HR variability in urethane-anesthetized, mechanically ventilated Sprague-Dawley rats exposed to five 3 minutes hypoxias. Blood pressure and ECG was monitored throughout the experiment and analyzed in the period during hypoxic exposures, 15, 30 and 60 minutes after the last hypoxic episode. Mean RR interval was 156.25 ms during baseline and did not significantly change throughout the experiment (151.72 ; 160.43 ; 161.91 and 157.77 ms, P=0.17). Low frequency (LF) component increased from 0.65 nu prior to hypoxia to 1.06 nu during the first hypoxic exposure and to 3.62 ; 9.46 and 1.79 nu at 15, 30 and 60 minutes after the last hypoxic episode, respectively (P=0.043). LF/HF ratio increased from 0.5 to 2.64 during the first hypoxic exposure and to 2.72 ; 6.15 and 6.9 nu at 15, 30 and 60 minutes after the last hypoxic episode, respectively (P=0.043). In time control experiments no change in HR variability was noted during the same time period observed. Conclusion: Heart rate variability shows significant changes during and after AIH protocol indicating the increase in sympathetic modulation of cardiac function during hypoxia and at the time after hypoxic exposures.

Department of Neuroscience from University of Split School of Medicine has put together a series of workshops for pre school children introducing them to basic knowledge of human brain and senses (sight, smell, hearing, touch and taste) through the games and funny activities. The workshops were aimed at age group 3 to 7, and organized into two 45 min periods. Children made their own brain models using a Play-Dough and a string to make a brain curves. This was followed with a presentation of the scientist look. They were dressed to be a scientist. Short introductory game was performed to “break the ice”. Children were given 5 pieces of paper with one picture of eye, nose, ear, hand and tongue on each paper. We were playing the game: when I said “red” they had to raise the right picture in the air (eye) ; if I said “music” they had to raise ear. Children learned that the “sense” travels from our body to the brain which is responsible for the interpretation of what we see, hear or taste. “Magic box” game was performed introducing them to touch and smell senses. Different games were played with younger children. They used band-aid and syringes to treat their sick teddy bears, played hide and seek in the tent we have provided for them. Finally, all children had the opportunity to draw an object (their choice was to draw a house) with their left and right hand on the same piece of paper. They were able to compare their drawings and learn about brain hemisphere controlling their dominant hand. We have organized similar activities during the Brain Awareness Week (BAW) for the last 8 years, and thus it became tradition in our Department. These workshops are a simple way of providing fun public engagement opportunities to children but also to students and staff at the University of Split School of Medicine.

Objectives: To investigate the effect of 5-HT1A receptor antagonist WAY-100635 on the phrenic long-term facilitation (pLTF) in rats. We hypothesized there would be a significant attenuation of pLTF in animals treated with WAY-100635 in comparison with control group of animals. Methods: Twenty one adult, male, urethane anesthetized, vagotomized, paralyzed, and mechanically ventilated Sprague-Dawley rats (7 per group), were exposed to the acute intermittent hypoxia (AIH) protocol. Protocol consisted of 5 hypoxic episodes (9%O2), each lasting for 3 minutes. Experimental groups of animals WAY0 and WAY60 received an intravenous injection of WAY-100635, before the onset of the first hypoxic stimulus, and 60 minutes after the end of last hypoxia, respectively. Peak phrenic nerve amplitude (PNA), burst frequency (f), and breathing rhythm parameters (Ti, Te, Ttot) were analyzed during the first hypoxia, as well as at 15 (T15), 30 (T30), and 60 minutes (T60) after the end of the last hypoxic episode, and compared to the baseline values. Results: In control and WAY60 group, significant increases of PNA (58.7 ± 3.3%, p

Introduction: Long term facilitation (LTF) is sustained augmentation of respiratory motor output elicited by acute intermittent hypoxia (AIH), and is considered as a form of the central nervous system plasticity. It has been demonstrated in urethane-anesthetized rats. Propofol is an intravenous anesthetic widely used in humans. So far, the influence of propofol anesthesia on LTF in the model of AIH has not been studied in rats. Our hypothesis is that, there will be a significant difference in LTF between urethane and propofol anesthesia. Materials and methods: The phrenic nerve activity (PNA) was recorded in 14 adult, male, Sprague-Dawley rats, bilaterally vagotomized, paralyzed and mechanically ventilated. The phrenic nerve recordings monitored central respiratory activity. Phrenic nerve was dissected using dorsal approach at the level of C5 nerve rootlet, mounted on bipolar silver wire electrodes. The rats were placed in a prone position in a stereotaxic instrument. The animals were divided in 2 groups ; group U (urethane-anesthetized, 1.2 g/kg i.p., n=7) and group P (propofol-anesthetized, iv bolus 11.9 mg/kg + infusion 1.3 mg/kg/min, n=7). Rats were exposed to five, 3-min hypoxic episodes (FiO2=0.09), separated by 3 minutes of hyperoxia (FiO2=0.5). Peak phrenic nerve amplitude (PNA), burst frequency (f), inspiratory time duration (Ti), expiratory time duration (Te) and total respiratory cycle duration (Ttot) were analyzed during the first hypoxia and 15, 30 and 60 minutes after the final hypoxic episode, and compared to the baseline values prior to the first hypoxic episode. Results: Isocapnia was successfully maintained throughout the protocol. There was a significant increase of peak phrenic nerve amplitude (66.7 ± 8.6%, p

Introduction: Long term facilitation (LTF) represents form of neural plasticity that persists long after exposures to episodic hypoxia have ceased. LTF stimulation protocol employs wide variety of hypoxic episodes at different O2 levels that could affect the elicitation, magnitude and duration of phrenic LTF in anesthetized rats. Therefore, the present study examined the effects of two different experimental protocols consisting of different hypoxic episode number and duration. Materials and methods: The phrenic nerve activity (PNA) was recorded in 10 adult, male, Sprague-Dawley rats, urethane anesthetized, bilaterally vagotomized, paralyzed and mechanically ventilated. Femoral arteries and veins were cannulated for blood pressure monitoring, obtaining blood samples, and intravenous drugs administrations and infusions. The phrenic nerve recordings monitored central respiratory activity. Phrenic nerve was dissected using dorsal approach at the level of C5 nerve rootlet, mounted on bipolar silver wire electrodes. The rats were placed in a prone position in a stereotaxic instrument. The animals were divided in 2 groups. One group (n=5) was exposed to five hypoxias that lasted for 3 minutes each (FiO2=0.09), separated by 3 minutes of hyperoxia (FiO2=0.5). Another group was exposed to three hypoxias that lasted for 5 minutes each (FiO2=0.09), separated by 5 minutes of hyperoxia (FiO2=0.5). Peak phrenic nerve amplitude (PNA), burst frequency (f), inspiratory time duration (Ti), expiratory time duration (Te) and total respiratory cycle duration (Ttot) were analyzed during the first hypoxia and 15, 30 and 60 minutes after the final hypoxic episode, and compared to the baseline values prior to the first hypoxic episode. Results: Isocapnia was successfully maintained throughout the protocol. There was a significant increase of peak phrenic nerve amplitude (66.7 ± 8.6%, p