Bronquiolite viral aguda é mundialmente a doença de vias aéreas inferiores mais comum entre lactentes e crianças jovens, sendo uma das principais causas de hospitalização na infância. Um grupo específico de crianças tem risco aumentado para desenvolver quadros mais graves sendo que os principais fatores de risco associados são: idade, sexo, co-morbidades (prematuridade, presença de displasia broncopulmonar e cardiopatia congênita, imunodeficiência), fatores ambientais e socioeconômicos e historia de atopia familiar. Os principais agentes etiológicos associados a bronquiolite são o vírus sincicial respiratório (VSR); influenza A e B; parainfluenza 1, 2 e 3 e adenovírus, picornavírus, coronavírus e metapneumovírus humano. O objetivo deste estudo foi avaliar a etiologia e o impacto clínico de infecções por vírus respiratórios em lactentes com idade entre 0 a 2 anos durante o primeiro episódio de sibilância, atendidas no Pronto Atendimento do Hospital Israelita Albert Einstein. Os vírus respiratórios foram investigados na amostra de lavado nasofaríngeo, exclusivamente por métodos de biologia molecular incluindo RT-PCR em tempo real (vírus sincicial respiratório, influenza, parainfluenza, rinovírus) RT-PCR convencional (coronavírus e metapneumovírus humano) e PCR convencional (adenovírus e bocavírus humano). Os desfechos avaliados foram impacto clínico imediato (hospitalização e admissão em unidade de terapia intensiva - UTI) e tardio (chiado recorrente), através do atendimento inicial e de entrevistas telefônicas aos 15 e 30 dias (impacto imediato) e posteriormente aos 3, 6 e 12 meses (impacto tardio). Chiado recorrente foi caracterizado pela ocorrência de três ou mais episódios de sibilância tratamento com medicação profilática para asma durante o seguimento. A verificação de associação entre as variáveis explicativas e os desfechos escolhidos foi feita através de modelo de regressão logística uni e multivariada, expressando os resultados em razão de chance (odds ratio, OR). O nível de significância adotado foi p< 0,05. Foram incluídos 77 lactentes, com mediana de idade de 6±4 meses. A identificação de pelo menos um vírus respiratório ocorreu em 72 (93%) das amostras. O vírus sincicial respiratório foi positivo em 49 amostras (64%), seguido por rinovírus (34%), enterovírus (21%), metapneumovírus humano (16%), bocavírus humano (12%), parainfluenza 3 (8%) e influenza A (2%), coronavírus (2%) e parainfluenza 1 (1%). Co-detecções foram observadas em 34 amostras (44%). Dos 77 lactentes incluídos no estudo, 32 (41%) necessitaram internação e 8 foram admitidos em UTI, sendo que estes eram mais jovens (p=0,02) e apresentaram maior tempo de internação (6,4 x 3,9 dias, p=0,012) em relação aos lactentes que internaram em apartamento. Quanto ao desfecho internação, idade mais jovem esteve associada a maior risco de internação (OR=0,83; p=0,026), enquanto atopia teve efeito protetor (OR=0,20; p=0,021). Identificação de enterovírus esteve associada a aumento do risco para internação (OR=6,03; p=0,027). Prematuridade foi a única variável associada a um significativo risco de admissão em UTI (OR=24,51; p=0,002). Após um ano de seguimento, 55% dos pacientes foram caracterizados como chiadores recorrentes, mas nenhum fator de risco ou etiologia viral estiveram associados a este desfecho. / Acute viral bronchiolitis is the most common disease of the lower respiratory tract in infants and young children throughout the world, being one of the main causes for hospitalization during infancy. A specific group of children has a greater risk for developing more servere cases, where the most important associated risk factors are: age, gender, co-morbidities (prematurity, presence of bronchopulmonary displasia and congenital heart diseases, deficiency in the immune system), environmental and social-economic factors, and a family history of allergies. The main etiological agents associated with bronchiolitis are the respiratory syncytial virus (RSV), influenza types A and B, parainfluenza types 1, 2 and 3 and adenovirus, picornavirus, coronavirus and human metapneumovirus.The objective of this study was to evaluate the etiology and clinical impact of respiratory viruses in infants aged 0 to 2 years, during the first episode of wheezing, attended at the Emergency Unit of the Albert Einstein Israeli Hospital. Respiratory viruses were investigated in nasopharyngeal aspirates, using molecular biology methods, including real time RT-PCR (respiratory syncytial virus, influenza, parainfluenza, rinovirus) conventional RT-PCR (coronavirus and human metapneumovirus) and conventional PCR (adenovirus and human bocavirus). The evaluated outcomes were immediate clinical impact (hospitalization and admission in an intensive care unit ICU) and late impacts (recurrent wheezing), in the initial approach and telephone interviews at 15 and 30 days (immediate impact) and later at 3, 6 and 12 months (late impact). Recurrent wheezing was characterized by the occurrence of three or more wheezing episodes or treatment with prophylactic medicines for asthma during the follow-up. The verification of the association between the explanatory variables and the chosen outcomes was done using uni and multivariated logistic regression models, expressing the results in odds ratio (OR). The level of significance adopted was p<0.05. Seventy-seven infants were included, with a median age of 6 ± 4 months. The identification of ate least one respiratory virus occurred in 72 (93%) of the samples. Respiratory syncytial virus tested positive in 49 samples (64%), followed by rinovirus (34%), enterovirus (21%), human metapneumovirus (16%), human bocavirus (12%), parainfluenza type 3 (8%) and influenza tipe A (2%), coronavirus (2%) and parainfluenza type 1 (1%). Co-detections were observed in 34 samples (44%). Of the 77 infants included in this study, 32 (41%) needed hospitalization and 8 were admitted to ICU, the latter ones being younger (p=0.02) and were hospitalized for a longer period of time (6.4 x 3.9 days, p=0.012) in relation to the infants who were admitted in wards. Regarding the hospitalization outcome, younger patients had a greater risk of hospitalization (OR=0.83; p=0.026), while allergies had a protective effect (OR=0.20; p=0.021). The identification of enterovirus was associated with a greater risk of hospitalization (OR=0.83; p=0.027). Prematurity was the only variable associated with a significant risk of admission in ICU (OR=24.51; p=0.002). After a follow-up one year later, 55% of the patients were characterized as recurrent wheezers, but no risk factor or viral etiology were associated with this outcome.

Bronquiolite viral aguda é mundialmente a doença de vias aéreas inferiores mais comum entre lactentes e crianças jovens, sendo uma das principais causas de hospitalização na infância. Um grupo específico de crianças tem risco aumentado para desenvolver quadros mais graves sendo que os principais fatores de risco associados são: idade, sexo, co-morbidades (prematuridade, presença de displasia broncopulmonar e cardiopatia congênita, imunodeficiência), fatores ambientais e socioeconômicos e historia de atopia familiar. Os principais agentes etiológicos associados a bronquiolite são o vírus sincicial respiratório (VSR); influenza A e B; parainfluenza 1, 2 e 3 e adenovírus, picornavírus, coronavírus e metapneumovírus humano. O objetivo deste estudo foi avaliar a etiologia e o impacto clínico de infecções por vírus respiratórios em lactentes com idade entre 0 a 2 anos durante o primeiro episódio de sibilância, atendidas no Pronto Atendimento do Hospital Israelita Albert Einstein. Os vírus respiratórios foram investigados na amostra de lavado nasofaríngeo, exclusivamente por métodos de biologia molecular incluindo RT-PCR em tempo real (vírus sincicial respiratório, influenza, parainfluenza, rinovírus) RT-PCR convencional (coronavírus e metapneumovírus humano) e PCR convencional (adenovírus e bocavírus humano). Os desfechos avaliados foram impacto clínico imediato (hospitalização e admissão em unidade de terapia intensiva - UTI) e tardio (chiado recorrente), através do atendimento inicial e de entrevistas telefônicas aos 15 e 30 dias (impacto imediato) e posteriormente aos 3, 6 e 12 meses (impacto tardio). Chiado recorrente foi caracterizado pela ocorrência de três ou mais episódios de sibilância tratamento com medicação profilática para asma durante o seguimento. A verificação de associação entre as variáveis explicativas e os desfechos escolhidos foi feita através de modelo de regressão logística uni e multivariada, expressando os resultados em razão de chance (odds ratio, OR). O nível de significância adotado foi p< 0,05. Foram incluídos 77 lactentes, com mediana de idade de 6±4 meses. A identificação de pelo menos um vírus respiratório ocorreu em 72 (93%) das amostras. O vírus sincicial respiratório foi positivo em 49 amostras (64%), seguido por rinovírus (34%), enterovírus (21%), metapneumovírus humano (16%), bocavírus humano (12%), parainfluenza 3 (8%) e influenza A (2%), coronavírus (2%) e parainfluenza 1 (1%). Co-detecções foram observadas em 34 amostras (44%). Dos 77 lactentes incluídos no estudo, 32 (41%) necessitaram internação e 8 foram admitidos em UTI, sendo que estes eram mais jovens (p=0,02) e apresentaram maior tempo de internação (6,4 x 3,9 dias, p=0,012) em relação aos lactentes que internaram em apartamento. Quanto ao desfecho internação, idade mais jovem esteve associada a maior risco de internação (OR=0,83; p=0,026), enquanto atopia teve efeito protetor (OR=0,20; p=0,021). Identificação de enterovírus esteve associada a aumento do risco para internação (OR=6,03; p=0,027). Prematuridade foi a única variável associada a um significativo risco de admissão em UTI (OR=24,51; p=0,002). Após um ano de seguimento, 55% dos pacientes foram caracterizados como chiadores recorrentes, mas nenhum fator de risco ou etiologia viral estiveram associados a este desfecho. / Acute viral bronchiolitis is the most common disease of the lower respiratory tract in infants and young children throughout the world, being one of the main causes for hospitalization during infancy. A specific group of children has a greater risk for developing more servere cases, where the most important associated risk factors are: age, gender, co-morbidities (prematurity, presence of bronchopulmonary displasia and congenital heart diseases, deficiency in the immune system), environmental and social-economic factors, and a family history of allergies. The main etiological agents associated with bronchiolitis are the respiratory syncytial virus (RSV), influenza types A and B, parainfluenza types 1, 2 and 3 and adenovirus, picornavirus, coronavirus and human metapneumovirus.The objective of this study was to evaluate the etiology and clinical impact of respiratory viruses in infants aged 0 to 2 years, during the first episode of wheezing, attended at the Emergency Unit of the Albert Einstein Israeli Hospital. Respiratory viruses were investigated in nasopharyngeal aspirates, using molecular biology methods, including real time RT-PCR (respiratory syncytial virus, influenza, parainfluenza, rinovirus) conventional RT-PCR (coronavirus and human metapneumovirus) and conventional PCR (adenovirus and human bocavirus). The evaluated outcomes were immediate clinical impact (hospitalization and admission in an intensive care unit ICU) and late impacts (recurrent wheezing), in the initial approach and telephone interviews at 15 and 30 days (immediate impact) and later at 3, 6 and 12 months (late impact). Recurrent wheezing was characterized by the occurrence of three or more wheezing episodes or treatment with prophylactic medicines for asthma during the follow-up. The verification of the association between the explanatory variables and the chosen outcomes was done using uni and multivariated logistic regression models, expressing the results in odds ratio (OR). The level of significance adopted was p<0.05. Seventy-seven infants were included, with a median age of 6 ± 4 months. The identification of ate least one respiratory virus occurred in 72 (93%) of the samples. Respiratory syncytial virus tested positive in 49 samples (64%), followed by rinovirus (34%), enterovirus (21%), human metapneumovirus (16%), human bocavirus (12%), parainfluenza type 3 (8%) and influenza tipe A (2%), coronavirus (2%) and parainfluenza type 1 (1%). Co-detections were observed in 34 samples (44%). Of the 77 infants included in this study, 32 (41%) needed hospitalization and 8 were admitted to ICU, the latter ones being younger (p=0.02) and were hospitalized for a longer period of time (6.4 x 3.9 days, p=0.012) in relation to the infants who were admitted in wards. Regarding the hospitalization outcome, younger patients had a greater risk of hospitalization (OR=0.83; p=0.026), while allergies had a protective effect (OR=0.20; p=0.021). The identification of enterovirus was associated with a greater risk of hospitalization (OR=0.83; p=0.027). Prematurity was the only variable associated with a significant risk of admission in ICU (OR=24.51; p=0.002). After a follow-up one year later, 55% of the patients were characterized as recurrent wheezers, but no risk factor or viral etiology were associated with this outcome.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2006. / Härtill 5 uppsatser.

Made available in DSpace on 2014-08-20T13:57:56Z (GMT). No. of bitstreams: 1 Dissertacao_Adriana_Muino_Garcia.pdf: 622784 bytes, checksum: d172556f6382623c1c270d2969f20698 (MD5) Previous issue date: 2006-12-18 / Wheezing patterns during childhood have important prognostic implications. The aim of this study was to measure the prevalence of wheezing patterns in a sub-sample of the 1993 Pelotas, Brazil, birth cohort, interviewed at birth , 6 and 12 month, 4 and 10-12 years of age. The wheezing patterns studied were: transient, persistent, late onset and recurrent. The total of the sub-sample was 897 children (20% systematic sample from the original cohort) with the prevalence and 95% confidence interval of wheezing patterns as follows: transient 44.7% (40.7-47.2); persistent 6.4% (4.8-8.0); late onset 3.3% (2.2-4.5); recurrent 4.1% (2.8-5.4). The independent variables associated with the wheezing patterns were: a) transient wheeze: low family income, shorter duration of breast-feeding, respiratory infections (6 and/or 12 months) and family history of asthma; b) persistent: male sex, asthma during pregnancy, respiratory infections in infancy and family history of asthma (4 and 10-12 years; c) late onset: family history of asthma (10-12 years old), medical diagnoses of rhinitis (10-12 years old) and as protective factors respiratory infections in infancy and a medical diagnosis of eczema (at adolescence); d) recurrent: smoking during pregnancy and having no asthma in the family. Identifying wheezing patterns and associated factors allow us to adopt preventive measures and to avoid lung function deterioration in adult life. / Os padrões de sibilância respiratória têm importantes implicações prognósticas. O objetivo deste estudo foi estudar estes padrões em uma sub-amostra da coorte de 1993 de Pelotas, Brasil, com vários acompanhamentos (nascimento, 6 e 12 meses, 4 e 10-12 anos de idade). Os padrões estudados foram: transitório, persistente, de início tardio e recorrente. A sub-amostra totalizou 897 crianças (sub-amostra sistemática de 20% da coorte original) com prevalências e IC 95% de: padrão transitório 44,7% (40,7-47,2); persistente 6,4% (4,8-8,0); início tardio 3,3% (2,2-4,5); recorrente 4,1% (2,8-5,4). As variáveis independentes associadas a estes padrões foram: a) para sibilância transitória: baixa renda, menor duração da amamentação, infecções respiratórias (6 e/ou 12 meses) e asma na família (quatro anos); b) para persistente: sexo masculino, asma na gravidez, infecções respiratórias na infância e histórico familiar de asma; c) de início tardio: histórico de asma, diagnóstico médico de rinite (10-12 anos) e diagnóstico médico de eczema (10-12 anos) e como fator protetor infecções respiratórias na infância; d) para recorrente: fumo na gestação e ausência de asma na família (quatro anos). A identificação destes padrões e de seus fatores associados permite a adoção de condutas terapêuticas para impedir déficit de função pulmonar posteriormente.

The prevalence of respiratory symptoms indicative of asthma in children from Latin America has been largely ignored. As part of the International Study of Asthma and Allergies in Childhood (ISAAC), 17 centers in 9 different Latin American countries participated in the study, and data from 52,549 written questionnaires (WQ) in children aged 13-14 years and from 36,264 WQ in 6-7 year olds are described here. In children aged 13-14 years, the prevalence of asthma ever ranged from 5.5-28%, and the prevalence of wheezing in the last 12 months from 6.6-27%. In children aged 6-7 years, the prevalence of asthma ever ranged from 4.1-26.9%, and the prevalence of wheezing in the last 12 months ranged from 8.6-32.1%. The lower prevalence in centers with higher levels of atmospheric pollution suggests that chronic inhalation of polluted air in children does not contribute to asthma. Furthermore, the high figures for asthma in a region with a high level of gastrointestinal parasite infestation, and a high burden of acute respiratory infections occurring early in life, suggest that these factors, considered as protective in other regions, do not have the same effect in this region. The present study indicates that the prevalence of asthma and related symptoms in Latin America is as high and variable as described in industrialized or developed regions of the world. / Revisión por pares

Yip Lung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references. / Abstracts in English and Chinese. / Chapter 1 --- Introduction / Chapter 1.1 --- Heart and Lung Diseases --- p.1 / Chapter 1.1.1 --- Hong Kong --- p.1 / Chapter 1.1.2 --- China --- p.2 / Chapter 1.1.3 --- the United States of America (USA) --- p.3 / Chapter 1.2 --- Auscultation --- p.3 / Chapter 1.2.1 --- Introduction of Auscultation --- p.4 / Chapter 1.2.2 --- Comparison between Auscultation and Ultrasound --- p.6 / Chapter 1.3 --- Stethoscope --- p.7 / Chapter 1.3.1 --- History of Stethoscope --- p.7 / Chapter 1.3.2 --- New Electronic Stethoscope --- p.14 / Chapter 1.4 --- Main Purpose of the Study --- p.16 / Chapter 1.5 --- Organization of Thesis --- p.16 / References --- p.18 / Chapter 2 --- A New Electronic Stethoscope's Head / Chapter 2.1 --- Introduction --- p.20 / Chapter 2.2 --- Biopotential Electrode --- p.21 / Chapter 2.2.1 --- Flexible Electrode --- p.21 / Chapter 2.2.2 --- Laplacian Electrocardiogram --- p.22 / Chapter 2.3 --- Transducer --- p.25 / Chapter 2.4 --- Design of the Head of Stethoscope --- p.26 / Chapter 2.5 --- Experimental Results --- p.27 / Chapter 2.5.1 --- Bias Voltage of Condenser Microphone --- p.27 / Chapter 2.5.2 --- Frequency Response of New Stethoscope's Head --- p.29 / Chapter 2.6 --- Discussion --- p.30 / Chapter 2.7 --- Section Summary --- p.31 / References --- p.33 / Chapter 3 --- Signal Pre-processing Unit / Chapter 3.1 --- Introduction --- p.35 / Chapter 3.2 --- High Input Impedance IC Amplifier --- p.36 / Chapter 3.3 --- Voltage Control Voltage Source High Pass Filter Circuit --- p.37 / Chapter 3.4 --- Multiple Feed Back Low Pass Filter Circuit --- p.39 / Chapter 3.5 --- Overall Circuit --- p.41 / Chapter 3.6 --- Experimental Results --- p.43 / Chapter 3.7 --- Discussion --- p.46 / Chapter 3.8 --- Section Summary --- p.47 / References --- p.48 / Chapter 4 --- Central Platform / Chapter 4.1 --- Introduction --- p.49 / Chapter 4.2 --- Adaptive Filter --- p.49 / Chapter 4.2.1 --- Introduction to Adaptive Filtering --- p.49 / Chapter 4.2.2 --- Least-Mean-Square (LMS) Algorithm --- p.51 / Chapter 4.2.3 --- Applications --- p.52 / Chapter 4.3 --- Offline Processing --- p.54 / Chapter 4.3.1 --- WINDAQ and MATLAB --- p.55 / Chapter 4.3.2 --- Direct Reference Algorithm --- p.57 / Chapter 4.3.3 --- Determination of Parameters in DRA --- p.62 / Chapter 4.3.4 --- Experimental Results of DRA --- p.67 / Chapter 4.3.5 --- Acoustic Waveform Based Algorithm --- p.72 / Chapter 4.3.6 --- Experimental Results of AWBA --- p.81 / Chapter 4.4 --- Online Processing --- p.85 / Chapter 4.4.1 --- LABVIEW --- p.85 / Chapter 4.4.2 --- Automated Gain Control --- p.88 / Chapter 4.4.3 --- Implementation of LMS adaptive filter --- p.89 / Chapter 4.4.4 --- Experimental Results of Online-AGC --- p.92 / Chapter 4.5 --- Discussion --- p.93 / Chapter 4.6 --- Section Summary --- p.97 / References --- p.98 / Chapter 5 --- Conclusion and Further Development / Chapter 5.1 --- Conclusion of the Main Contribution --- p.100 / Chapter 5.2 --- Future Works --- p.102 / Chapter 5.2.1 --- Modification of the Head of Stethoscope --- p.102 / Chapter 5.2.2 --- Validation of Abnormal Breath --- p.102 / Chapter 5.2.3 --- Low Frequency Analysis --- p.102 / Chapter 5.2.4 --- AGC-AWBA Approach --- p.102 / Chapter 5.2.5 --- Standalone Device --- p.103 / Chapter 5.2.6 --- Demand on Stethoscope --- p.109 / References --- p.110 / Appendix / Chapter A.1 --- Determination of parameters in VCVS High Pass Filter --- p.106 / Chapter A.2 --- Determination of parameters in MFB Low Pass Filter --- p.110 / Chapter A.3 --- Source code of DRA (MATLAB) --- p.114 / Chapter A.4 --- Source code of AWBA (MATLAB) --- p.129 / Chapter A.5 --- Source code of online AGC (LABVIEW) --- p.134

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado / Background: There are no internationally validated questionnaires to investigate the prevalence of infant wheezing. This study was undertaken to validate a questionnaire for the International Study on the Prevalence of Wheezing in Infants (Estudio Internacional de Sibilancias en Lactantes, EISL). Material and Methods: Construct and criterion validity were tested for the question 'Has your baby had wheezing or whistling in the chest during his/her first 12 months of life?'. Construct validity (i.e. the ability of parents and doctors to refer to the same symptoms with the same words) was tested in a sample of 50 wheezing and 50 non-wheezy infants 12-15 months of age in each of 10 centres from 6 different Spanish- or Portuguese-speaking countries. Criterion validity (i.e. the ability of parents to correctly detect the symptom in the general population) was evaluated in 2 samples (Santiago, Chile and Cartagena, Spain) of 50 wheezing and 50 non-wheezing infants (according to parents) of the same age, randomly selected from the general population, who were later blindly diagnosed by a paediatric pulmonologist. Results: Construct validity was very high (κ test: 0.98-1) in all centres. According to Youden's index, criterion validity was good both in Cartagena (75.5%) and in Santiago (67.0%). Adding questions about asthma medication did not improve diagnosis accuracy. Conclusions: The EISL questionnaire significantly distinguished wheezy infants from healthy ones. This questionnaire has a strong validity and can be employed in large international multicentre studies on wheezing during infancy. / Revisión por pares

O presente estudo tem como objetivo determinar se a gravidade da DPOC poderá ser estimada através da área do gráfico das intensidades sonoras dos sons respiratórios de pacientes com DPOC. O estudo realizado com 51 pacientes com DPOC leve, moderado, grave, muito grave e 7 indivíduos saudáveis não fumantes. Os sons respiratórios de cada participante, foram coletados através de estetoscópio adaptado com um mini microfone. O método compara as áreas das intensidades sonoras em função da frequência de pacientes de DPOC e indivíduos saudáveis. Neste contexto, para atender ao objetivo, um método foi proposto e testado baseado na combinação de técnicas de filtragem e TFTC, seguida de análise estatística, cálculo da média, desvio padrão e interpolação. Os resultados sugerem que a área do gráfico da variância da intensidade sonora em função da frequência diminui quando aumenta a gravidade da DPOC, exceto para os casos em que a bronquite crônica é predominante. / The present study aims to determine if the severity of COPD can be estimated through the chart area of the sound intensities of respiratory sounds in patients with COPD. The study included 51 patients with mild, moderate, severe, very severe COPD and 7 healthy non-smokers. The breathing sounds of each participant were collected through a stethoscope adapted with a mini microphone. The method compares the areas of intensity sonic densities as a function of the frequency of COPD patients and healthy individuals. In this context, to meet the objective, a method was proposed and tested based on the combination of filtering techniques and TFTC, followed by statistical analysis, calculation of the mean, standard deviation and interpolation. The results suggest that the area of the graph of frequency-frequency sound intensity variance decreases as the severity of COPD increases, except for cases where chronic bronchitis is predominant.

Tracheal respiratory sounds analysis has been investigated as a non-invasive method to estimate respiratory flow and upper airway obstruction. However, the flow-sound relationship is highly variable among subjects which makes it challenging to estimate flow in general applications. Therefore, a robust model for acoustical flow estimation in a large group of individuals did not exist before. On the other hand, a major application of acoustical flow estimation is to detect flow limitations in patients with obstructive sleep apnea (OSA) during sleep. However, previously the flow--sound relationship was only investigated during wakefulness among healthy individuals. Therefore, it was necessary to examine the flow-sound relationship during sleep in OSA patients. This thesis takes the above challenges and offers innovative solutions. First, a modified linear flow-sound model was proposed to estimate respiratory flow from tracheal sounds. To remove the individual based calibration process, the statistical correlation between the model parameters and anthropometric features of 93 healthy volunteers was investigated. The results show that gender, height and smoking are the most significant factors that affect the model parameters. Hence, a general acoustical flow estimation model was proposed for people with similar height and gender. Second, flow-sound relationship during sleep and wakefulness was studied among 13 OSA patients. The results show that during sleep and wakefulness, flow-sound relationship follows a power law, but with different parameters. Therefore, for acoustical flow estimation during sleep, the model parameters should be extracted from sleep data to have small errors. The results confirm reliability of the acoustical flow estimation for investigating flow variations during both sleep and wakefulness. Finally, a new method for sleep apnea detection and monitoring was developed, which only requires recording the tracheal sounds and the blood's oxygen saturation level (SaO2) data. It automatically classifies the sound segments into breath, snore and noise. A weighted average of features extracted from sound segments and SaO2 signal was used to detect apnea and hypopnea events. The performance of the proposed approach was evaluated on the data of 66 patients. The results show high correlation (0.96,p < 0.0001) between the outcomes of our system and those of the polysomnography. Also, sensitivity and specificity of the proposed method in differentiating simple snorers from OSA patients were found to be more than 91%. These results are superior or comparable with the existing commercialized sleep apnea portable monitors.