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Bizzotto D, Paganini S, Stucchi L, Palmisano Avallone M, Ramirez EM, Pompilio PP, Ferrucci F, Lavoie JP, Dellaca RL. A portable fan-based device for evaluating lung function in horses by the forced oscillation technique. Physiol Meas 2022; 43. [PMID: 35120344 DOI: 10.1088/1361-6579/ac522e] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 02/04/2022] [Indexed: 11/12/2022]
Abstract
OBJECTIVE The assessment of lung mechanics in horses is nowadays based on invasive methods that may require sedation. The forced oscillation technique (FOT) allows the non-invasive assessment of respiratory mechanics during spontaneous breathing, but current devices are complex, cumbersome, expensive, and difficult to be applied in horses. APPROACH We developed a portable FOT device based on a novel approach in which the pressure waveforms are generated by a servo-controlled ducted fan. This new approach allows the design of devices that are more sturdy, compact, and portable compared to already existing approaches. The prototype includes 1) a small microcontroller-based electronic board for controlling the fan and measuring flow and pressure and 2) an optimized data processing algorithm. MAIN RESULTS This device provides a maximum error of 0.06 cmH2O∙s/L and 0.15 cmH2O∙s/L in measuring respiratory resistance and reactance during in-vitro validation. A pilot study was also performed on three healthy horses and three horses with severe equine asthma (SEA) and it demonstrated good tolerability and feasibility of the new device. Total respiratory system resistance (Rrs) and reactance (Xrs) significantly differed (p<0.05) between groups. At 5Hz, Rrs was 0.66±0.02 cmH2O∙s/L and 0.94±0.07 cmH2O∙s/L in healthy and in SEA, respectively. Xrs 0.38±0.02 cmH2O∙s/L and -0.27±0.05 cmH2O∙s/L. SIGNIFICANCE This novel approach for applying FOT allowed the development of a small, affordable and portable device for the non-invasive evaluation of respiratory mechanics in spontaneously breathing horses, providing a useful new tool for improving veterinary respiratory medicine. Moreover, our results provide supporting evidence of the value of this novel approach for developing portable FOT devices also for applications in humans.
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Affiliation(s)
- Davide Bizzotto
- DEIB, Politecnico di Milano Dipartimento di Elettronica Informazione e Bioingegneria, Via Giuseppe Colombo, 40, Milano, 20133, ITALY
| | - Stefano Paganini
- DEIB, Politecnico di Milano Dipartimento di Elettronica Informazione e Bioingegneria, Via Giuseppe Colombo, 40, Milano, Milano, 20133, ITALY
| | - Luca Stucchi
- Equine Sports Medicine Lab (ESM-Lab), Università degli Studi di Milano Dipartimento di Medicina Veterinaria, Via dell'Università, 6, 26900 Lodi LO, Lodi, Lombardia, 26900, ITALY
| | - Matteo Palmisano Avallone
- DEIB, Politecnico di Milano Dipartimento di Elettronica Informazione e Bioingegneria, Via Giuseppe Colombo, 40, Milano, Milano, 20133, ITALY
| | - Esther Millares Ramirez
- Equine Asthma Laboratory, Université de Montréal Faculté de médecine vétérinaire, 3200 Rue Sicotte, Saint-Hyacinthe, QC J2S 2M2, Canada, Saint Hyacinthe, Quebec, J2S 7C6, CANADA
| | - Pasquale P Pompilio
- Restech srl, Via Melchiorre Gioia, 61, 20124 Milano MI, Milano, 20124, ITALY
| | - Francesco Ferrucci
- Equine Sports Medicine Lab (ESM-Lab), Università degli Studi di Milano Dipartimento di Medicina Veterinaria, Via dell'Università, 6, 26900 Lodi LO, Lodi, Lombardia, 26900, ITALY
| | - Jean-Pierre Lavoie
- Equine Asthma Laboratory, Université de Montréal Faculté de médecine vétérinaire, 3200 Rue Sicotte, Saint-Hyacinthe, QC J2S 2M2, Canada, Saint Hyacinthe, Quebec, J2S 2M2, CANADA
| | - Raffaele L Dellaca
- DEIB, Politecnico di Milano Dipartimento di Elettronica e Informazione, Via Giuseppe Colombo, 40, Milano, Milano, Lombardia, 20133, ITALY
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2
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Alobaidi NY, Almeshari M, Stockley JA, Sapey E, Edgar RG. A Systematic Review of the Use of Physiological Tests Assessing the Acute Response to Treatment During Exacerbations of COPD (with a Focus on Small Airway Function). COPD 2020; 17:711-720. [PMID: 33183078 DOI: 10.1080/15412555.2020.1815183] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Exacerbations are prevalent in Chronic Obstructive Pulmonary Disease (COPD) patients and associated with poor clinical outcomes. Currently, there is a lack of sensitive and specific tools that can objectively identify exacerbations and assess their progress or treatment response. FEV1 is often reported as a study outcome, but it has significant limitations. Studies have suggested that small airways measures might provide physiological biomarkers during exacerbations. Therefore, this study was done to assess which physiological tests of small airways function have been used in the acute setting during exacerbations of COPD and the evidence to support their use. An electronic databases search was conducted in April 2019. A standard systematic review methodology was used. Eligible studies were those of ≥10 participants that compared at least one small airway test with FEV1 to assess response to treatment with baseline and a follow-up measurement ≤2 months after. Analyses were narrative. Of 1436 screened studies, seven studies were eligible. There was heterogeneity in which tests of small airways were used and three different small airways measures were reported. Studies were small (including 20 to 87 subjects). Six articles reported improvements in small airway measurements during the recovery from exacerbation which correlated with FEV1. Included studies varied in their timing and duration of the assessment. There is some evidence to support the use of small airway tests in acute exacerbations of COPD. However, studies have been small with different tests being utilized. Further studies to determine the usefulness of each test may be of interest.
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Affiliation(s)
- Nowaf Y Alobaidi
- Institute of Inflammation and Ageing University of Birmingham, Edgbaston, Birmingham, UK.,Respiratory Therapy Department, College of Applied Medical Sciences, King Saud Bin Abdul-Aziz University for Health Sciences, Al Ahsa, Saudi Arabia
| | - Mohammed Almeshari
- Institute of Inflammation and Ageing University of Birmingham, Edgbaston, Birmingham, UK.,Rehabilitation Health Sciences Department, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
| | - James A Stockley
- Department of Lung Function and Sleep, University Hospitals Birmingham NHS Foundation Trust, Edgbaston, Birmingham, UK
| | - Elizabeth Sapey
- Institute of Inflammation and Ageing University of Birmingham, Edgbaston, Birmingham, UK
| | - Ross G Edgar
- Institute of Applied Health Research, University of Birmingham, Edgbaston, UK.,Therapy Services, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK
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3
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Turnbull CD, Manuel AR, Stradling JR. Does either obesity or OSA severity influence the response of autotitrating CPAP machines in very obese subjects? Sleep Breath 2015; 20:647-52. [DOI: 10.1007/s11325-015-1267-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 08/12/2015] [Accepted: 09/21/2015] [Indexed: 11/29/2022]
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4
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Bates JHT, Irvin CG, Farré R, Hantos Z. Oscillation mechanics of the respiratory system. Compr Physiol 2013; 1:1233-72. [PMID: 23733641 DOI: 10.1002/cphy.c100058] [Citation(s) in RCA: 118] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The mechanical impedance of the respiratory system defines the pressure profile required to drive a unit of oscillatory flow into the lungs. Impedance is a function of oscillation frequency, and is measured using the forced oscillation technique. Digital signal processing methods, most notably the Fourier transform, are used to calculate impedance from measured oscillatory pressures and flows. Impedance is a complex function of frequency, having both real and imaginary parts that vary with frequency in ways that can be used empirically to distinguish normal lung function from a variety of different pathologies. The most useful diagnostic information is gained when anatomically based mathematical models are fit to measurements of impedance. The simplest such model consists of a single flow-resistive conduit connecting to a single elastic compartment. Models of greater complexity may have two or more compartments, and provide more accurate fits to impedance measurements over a variety of different frequency ranges. The model that currently enjoys the widest application in studies of animal models of lung disease consists of a single airway serving an alveolar compartment comprising tissue with a constant-phase impedance. This model has been shown to fit very accurately to a wide range of impedance data, yet contains only four free parameters, and as such is highly parsimonious. The measurement of impedance in human patients is also now rapidly gaining acceptance, and promises to provide a more comprehensible assessment of lung function than parameters derived from conventional spirometry.
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Affiliation(s)
- Jason H T Bates
- Vermont Lung Center, University of Vermont College of Medicine, Burlington, Vermont, USA.
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5
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Kaczka DW, Dellacá RL. Oscillation mechanics of the respiratory system: applications to lung disease. Crit Rev Biomed Eng 2011; 39:337-59. [PMID: 22011237 DOI: 10.1615/critrevbiomedeng.v39.i4.60] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Since its introduction in the 1950s, the forced oscillation technique (FOT) and the measurement of respiratory impedance have evolved into powerful tools for the assessment of various mechanical phenomena in the mammalian lung during health and disease. In this review, we highlight the most recent developments in instrumentation, signal processing, and modeling relevant to FOT measurements. We demonstrate how FOT provides unparalleled information on the mechanical status of the respiratory system compared to more widely used pulmonary function tests. The concept of mechanical impedance is reviewed, as well as the various measurement techniques used to acquire such data. Emphasis is placed on the analysis of lower, physiologic frequency ranges (typically less than 10 Hz) that are most sensitive to normal physical processes as well as pathologic structural alterations. Various inverse modeling approaches used to interpret alterations in impedance are also discussed, specifically in the context of three common respiratory diseases: asthma, chronic obstructive pulmonary disease, and acute lung injury. Finally, we speculate on the potential role for FOT in the clinical arena.
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Affiliation(s)
- David W Kaczka
- Department of Anaesthesia, Harvard Medical School, Boston, Massachusetts, USA.
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6
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Campana LM, Owens RL, Suki B, Malhotra A. Measuring upper and lower airway resistance during sleep with the forced oscillation technique. Ann Biomed Eng 2011; 40:925-33. [PMID: 22127514 DOI: 10.1007/s10439-011-0470-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Accepted: 11/09/2011] [Indexed: 11/25/2022]
Abstract
The forced oscillation technique (FOT) is a non-invasive technique to monitor airway obstruction in those with asthma. The aim of this study was to design and validate a system to use FOT during sleep, both with and without bi-level positive airway pressure (BPAP), and to separate upper airway resistance from lower. 8 Hz pressure oscillations were supplied, over which the subject breathed, pressure and flow measurements were then used to calculate impedance. A phase-shift induced by the pressure transducer tubing was characterized, and FOT resistance was compared to steady flow resistance both with and without BPAP. A Millar catheter was used to measure pressure at the epiglottis, allowing the separation of upper from lower airway resistance. A phase shift of -0.010 s was calculated for the pressure transducer tubing, and the average error between FOT and steady flow resistance was -0.2 ± 0.2 cmH₂O/L/s without BPAP and 0.4 ± 0.2 cmH₂O/L/s with BPAP. The system was tested on three subjects, one healthy, one with obstructive sleep apnea, and one with asthma. The FOT was well tolerated and resistance was separated into upper and lower airway components. This setup is suitable for monitoring both upper and lower airway obstruction during sleep in those with and without asthma.
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7
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Farré R, Montserrat JM, Navajas D. Assessment of upper airway mechanics during sleep. Respir Physiol Neurobiol 2008; 163:74-81. [DOI: 10.1016/j.resp.2008.06.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2008] [Revised: 06/16/2008] [Accepted: 06/18/2008] [Indexed: 11/26/2022]
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8
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Ficker JH, Clarenbach CF, Neukirchner C, Fuchs FS, Wiest GH, Schahin SP, Harsch IA, Hahn EG. Auto-CPAP therapy based on the forced oscillation technique. BIOMED ENG-BIOMED TE 2003; 48:68-72. [PMID: 12701337 DOI: 10.1515/bmte.2003.48.3.68] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Autoadjusting CPAP devices (APAP) are designed to continuously adjust the positive pressure to the required levels, and thus increase treatment quality and patient compliance. The results of APAP treatment strongly depend on the control mechanism of the respective APAP device. In agreement with other working groups, we have recently shown that the forced oscillation technique (FOT) is capable of detecting incipient upper airway obstruction prior to physiological reactions such as the onset of increasing esophageal pressure swings or microarousals. Therefore we studied efficacy and acceptance of a novel APAP device controlled exclusively by FOT. 100 consecutive patients with OSAS confirmed by polysomnography (mean AHI 47.9 +/- 22.6) and daytime sleepiness (Epworth sleepiness scale, ESS 12.6 +/- 3.9) were randomized to either APAP treatment (n = 50) or conventional CPAP treatment (n = 50). Polysomnographies were performed at the second treatment night and subjective sleepiness (modified ESS) was established in the morning. The respiratory disturbance was largely normalized in both treatment groups in the second treatment night (AHI 4.7 +/- 5.3 vs. 3.7 +/- 3.4; n.s.). Both groups showed largely improved sleep profiles and had markedly reduced ESS-scores (6.6 +/- 3.6 vs. 7.0 +/- 3.4; n.s.). The mean treatment pressure during APAP was significantly lower than during CPAP treatment (6.0 +/- 2.0 vs. 9.0 +/- 1.8 mbar; p < 0.001). There were no significant differences between APAP and CPAP treatment in any parameter of efficacy or acceptance. APAP treatment with this device controlled exclusively by FOT is well accepted by the patients and permits an adequate treatment of OSAS without the need for invidiual CPAP titration.
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Affiliation(s)
- J H Ficker
- Medical Department 1, University of Erlangen-Nuremberg, Erlangen, Germany.
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9
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Abstract
Sleep studies have grown to encompass a broad range of technologies employed to study and diagnose a variety of sleep disorders. From their inception in neurophysiology laboratories interested in investigating primary disorders of sleep architecture from psychiatric illness, their remit has widened such that their most common role is currently to diagnose secondary sleep disruption from respiratory, cardiovascular or other systemic causes. This review outlines the pathophysiology of obstructive sleep apnoea in particular and how sleep studies have improved our understanding of the complex dynamic changes in blood gas tensions, cardiovascular control and cerebral arousal that occur with these repetitive events. We review the historical development of standard laboratory-based sleep studies and discuss their limitations in staging sleep, reflecting the episodes of increased upper airway resistance that underlie these disorders and their ability to predict individuals' symptoms or response to medical or surgical therapies. We then describe some alternative signals that have been employed to monitor the physiological changes in upper airway resistance and arousal with a discussion of some of the evidence that these 'limited' studies may provide diagnostic information that can guide clinical decision making and may predict the outcome without the need, in some cases, for more complex and costly laboratory-based studies.
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Affiliation(s)
- J C T Pepperell
- Oxford Centre for Respiratory Medicine, Churchill Hospital, Headington, UK.
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10
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Bohadana AB, Hannhart B, Teculescu DB. Nocturnal worsening of asthma and sleep-disordered breathing. J Asthma 2002; 39:85-100. [PMID: 11990234 DOI: 10.1081/jas-120002190] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Asthma has a tendency, to destabilize and get worse at night, probably due to a nocturnal increase in airiway inflammation and bronchial responsiveness. Nocturnal airway narrowing in asthma is often associated with sleep disorders, such as episodes of nocturnal and early morning awakening, difficulty in maintaining sleep, and day time sleepiness. On the other hand, an association has been documented between nocturnal sleep-disordered breathing and asthma. This review highlights the causes of nocturnal worsening of asthma and examines the evidence pointing toward a causal relationship between nocturnal asthma and sleep-disordered breathing.
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Affiliation(s)
- Abraham B Bohadana
- INSERM Unité 420, Epidémiologie, Santé, Travail, Faculté de Médecine, Vandoeuvre-lès-Nancy, France.
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11
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Pilz K, Thalhofer S, Meissner P, Dorow P. Improvement of CPAP Therapy by a Self-Adjusting System. Sleep Breath 2002; 4:169-172. [PMID: 11894203 DOI: 10.1007/s11325-000-0169-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The first generation of Auto CPAP devices caused respiratory arousal by apnoes, hypopnoeas, incomplete obstructions and pressurechanges. The new, second generation of CPAP devices which is based on forced oscillation technique will change the pressure with slower velocity and before the respiratory arousal reaction will occur (1, 9, 10). Fifty patients with severe sleep apnoea (AHI 66+/-26 /h) were treated with both, constant- CPAP (continous positive airway pressure) or Auto CPAP under polysomnographic control in a randomised order. The Auto CPAP based on forced oscillation technique reduced the number of apnoeas and hypopnoeas as did most of the other Auto CPAP systems to AHI 2.5+/-5.9 /h (p<0.05). In comparison to Auto CPAP of the first generation it also decreased the number of respiratory arousal reactions caused by apnoeas and hypopnoeas. However there is still a significant difference to number of arousal detected with constant CPAP (p<0.01). In conclusion although the new generation of Auto CPAP reduced the number of respiratory arousals compared to first generation, we did not find a therapeutical benefit for patients with severe SAS.
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Affiliation(s)
- Katrin Pilz
- DRK Hospital Mark Brandenburg, Department of Respiratory and Critical Care Medicine, Humboldt University of Berlin, Berlin, Germany
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12
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Abstract
This review summarizes current clinical use of the forced oscillation technique (FOT) for analysis of lung function. It presents an intuitive approach to FOT pattern recognition for interpretation of results in human subjects, and the view that FOT is now well established and, clinically, eminently useful in patients with airflow obstruction. The focus of this review is on findings that relate directly to clinical utility, with less emphasis on theoretical mechanisms. The major thrust for clinical application of FOT derives from a number of European clinical research centers. Farre and Navajas and their colleagues in Barcelona, Harf and the Lorinos and their coworkers in Paris, Peslin and Duvivier and their coworkers in Vandoeuvre-les-Nancy, Pride and coworkers in London, and Van de Woestijne, Clement, Demedts, Landser, Van Noord, and their colleagues in Leuven have essentially been responsible for clinical development of FOT over the past 25 years. Publishing space does not permit an exhaustive listing of the many contributions of these investigators, but it is intended that the present review will provide a useful infrastructure from which the reader may progress to other research citations as desired.
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13
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Randerath WJ, David M, Feldmeyer F, Galetke W, Ruhle KH. Automatic CPAP Based on Impedance - Comparison of Constant CPAP with an Individual Pressure Range. Vergleich von konstantem CPAP und impedanzgesteuerter automatischer Positivdruck-Therapie mit individueller Druckspanne. SOMNOLOGIE 2001. [DOI: 10.1046/j.1439-054x.2001.01155.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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14
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Farré R, Mancini M, Rotger M, Ferrer M, Roca J, Navajas D. Oscillatory resistance measured during noninvasive proportional assist ventilation. Am J Respir Crit Care Med 2001; 164:790-4. [PMID: 11549534 DOI: 10.1164/ajrccm.164.5.2102049] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Setting proportional assist ventilation (PAV) requires the measurement of patient resistance and elastance. To avoid patient sedation/paralysis or the use of an esophageal balloon, noninvasive PAV is indirectly set by the "runaway" method or in accordance with patient comfort. The aim of this study was to ascertain whether the forced oscillation technique (FOT) applied by the ventilator during noninvasive PAV is useful in assessing patient respiratory resistance. Nasal PAV was applied to 14 patients with severe chronic obstructive pulmonary disease. During PAV a modified ventilator applied a 5-Hz pressure oscillation to noninvasively assess FOT resistance (Rrs). Lung resistance (RL) was measured in seven of the patients by using an esophageal balloon. Moreover, measurements were also performed in five of the patients when PAV was applied through the mouth. Rrs was close to RL both during nasal (Rrs = 8.9 +/- 3.1, RL = 9.0 +/- 2.6; cm H(2)O x s/L; n = 7, p > 0.05) and mouth (Rrs = 5.6 +/- 2.1, RL = 5.8 +/- 1.4; cm H(2)O x s/L; n = 5, p > 0.05) breathing. Rrs was slightly greater than the maximum value of flow assistance applied during the setting of PAV (FAmax): 11.1 +/- 5.4 and 9.5 +/- 2.9 cm H(2)O x s/L, respectively (n = 14, p > 0.05), both variables being significantly correlated (r = 0.72, p < 0.05). FOT applied by the PAV ventilator allowed the assessment of patient resistance. These results suggest that FOT could be useful in setting PAV flow assistance and in automatically and continuously updating this setting in accordance with patient resistance.
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Affiliation(s)
- R Farré
- Unitat de Biofísica i Bioenginyeria, Facultat de Medicina, Universitat de Barcelona, Barcelona, Spain.
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15
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Badia JR, Farré R, Rigau J, Uribe ME, Navajas D, Montserrat JM. Forced oscillation measurements do not affect upper airway muscle tone or sleep in clinical studies. Eur Respir J 2001; 18:335-9. [PMID: 11529293 DOI: 10.1183/09031936.01.00085001] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Upper airway obstruction in the sleep apnoea/hypopnoea syndrome (SAHS) can be easily assessed by measuring respiratory impedance with the forced oscillation technique (FOT). This methodology has been proposed as a useful clinical tool both for the diagnosis of sleep breathing disorders and for continuous positive airway pressure (CPAP) titration. However, previous studies suggest that the application of high-frequency pressure oscillation to the upper airway may induce changes in the electroencephalogram (EEG) or upper airway muscle function. The effect of FOT measurements on upper airway muscle tone and EEG in clinical sleep studies was examined. Seven patients with moderate SAHS were included (age: 54+/-11 yrs; apnoea/hypopnoea index: 43+/-21 events x h(-1); body mass index: 30+/-2 kg x m(-2)). Genioglossus surface electromyogram activity (EMGgg) and EEG signal were analysed with and without FOT application (frequency: 5 Hz and 30 Hz; peak-to-peak pressure oscillation: 1 cmH2O) during stable sleep. Measurements were carried out in two different situations. Step 1: applying FOT during episodes of obstructive events or flow limitation; and step 2: during prolonged periods of normal breathing at optimal CPAP. The root mean square of EMGgg activity and fast Fourier analysis (alpha and delta bands) of the EEG signal were performed. The application of FOT did not increase EMGgg activity in any of the situations studied. In addition, no evidence of the effects on EEG was found: alpha/delta relationship: awake:0.70, baseline sleep:0.13, FOT(5 Hz):0.18, FOT(30 Hz):0.11. The presented results suggest that the use of forced oscillation technique over the ranges of frequency and amplitude proposed for clinical sleep studies does not induce changes in upper airway muscle activity and neurological variables in patients with sleep apnoea/hypopnoea syndrome.
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Affiliation(s)
- J R Badia
- Servei de Pneumologia i Allèrgia Respiratòria, Hospital Clínic, Barcelona, Spain
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16
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Randerath WJ, Schraeder O, Galetke W, Feldmeyer F, Rühle KH. Autoadjusting CPAP therapy based on impedance efficacy, compliance and acceptance. Am J Respir Crit Care Med 2001; 163:652-7. [PMID: 11254519 DOI: 10.1164/ajrccm.163.3.2006168] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Constant continuous positive airway pressure (CPAP) is the treatment of choice for the obstructive sleep apnea syndrome (OSAS). To enable the pressure to be matched more accurately to actual requirements, and thus increase patient acceptance, an autoadjusting device based on the measurement of upper airway impedance was developed (APAP(FOT)). We investigated the efficacy and compliance in continuous use at home. Fifty-two patients were treated (randomized crossover) with CPAP and APAP(FOT) for 6 wk each. Respiratory disturbances, sleep profile, and arousals improved significantly with both modes (AHI: baseline, 35.1 +/- 26/h; APAP(FOT), 5.0 +/- 5.2; CPAP, 4.3 +/- 6.3; p < 0.001 baseline versus each mode). The mean pressure with APAP(FOT) was significantly reduced as compared with CPAP (CPAP, 7.8 +/- 1.5 cm H2O; APAP(FOT), 5.7 +/- 1.8 cm H2O; p < 0.001). Under APAP(FOT) the pressure was lower than that under CPAP for 81.5 +/- 21% of the time. Although overall use did not differ, 75% of the patients preferred APAP(FOT) for home treatment. We conclude that APAP(FOT) is as efficacious as constant CPAP in the treatment of OSAS. The treatment pressure can be reduced significantly, and sleep microstructure improved with APAP(FOT). These might be the reasons for patient preference of automatic therapy.
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Affiliation(s)
- W J Randerath
- Klinik Ambrock, Department of Pneumology, Allergology and Sleep Medicine, University Witten/Herdecke, Germany.
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17
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Farré R, Rigau J, Montserrat JM, Ballester E, Navajas D. Evaluation of a simplified oscillation technique for assessing airway obstruction in sleep apnoea. Eur Respir J 2001; 17:456-61. [PMID: 11405525 DOI: 10.1183/09031936.01.17304560] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The forced oscillation technique (FOT) is a noninvasive method that is useful for assessing airway obstruction and for titrating continuous positive airway pressure (CPAP) in patients with sleep apnoea. The aim was to evaluate the routine applicability of a simplified FOT set-up based on recording pressure and flow at the level of the CPAP device, i.e. obviating the need for connecting the transducers to the nasal mask. A correction to account for the tubing and the exhaust port was applied. This simplified FOT was evaluated on nine patients with moderate or severe sleep apnoea during routine CPAP titration. Patient impedance measured by the simplified FOT ([Z]) was compared with actual patient impedance ([Zrs]) measured simultaneously with a reference FOT based on recording pressure and flow at the nasal mask. An excellent agreement was found between [Z] and [Zrs] over the wide range of airway obstruction explored (4.8-72.1 cmH2O x s x L(-1)): [Z] = [Zrs] x 0.86 + 1.3 cmH2O x s x L(-1) (r = 0.99). Moreover, the simplified and the conventional FOT settings detected the same respiratory events during sleep. These results demonstrate that this simplified FOT is applicable for measuring airway obstruction during routine sleep studies in patients with sleep apnoea.
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Affiliation(s)
- R Farré
- Unitat de Biofisica i Bioenginyeria, Facultat de Medicina, Universitat de Barcelona, Spain
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Randerath WJ, Galetke W, David M, Siebrecht H, Sanner B, Rühle KH. Prospective randomized comparison of impedance-controlled auto-continuous positive airway pressure (APAP(FOT)) with constant CPAP. Sleep Med 2001; 2:115-124. [PMID: 11226860 DOI: 10.1016/s1389-9457(00)00048-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Background: The measurement of impedance permits reliable detection of obstructive apneas, hypopneas and upper airways resistance syndrome.Objective: To establish whether impedance-controlled self-adjusting positive airway pressure therapy (APAP(FOT)) is equally as good as constant continuous positive airway pressure (CPAP) in the treatment of sleep apnea syndrome (OSAS).Methods: Twenty men and five women with OSAS (age 52.8+/-9.0 years, body mass index (BMI) 31.4+/-5.0 kg/m(2), AHI 32.2+/-18.1/h (mean+/-SD)) underwent baseline polysomnography, manual CPAP titration and two nights of treatment, one with APAP(FOT), one with constant CPAP.Results: With both modes, a significant reduction in respiratory disturbances was seen (apnea/hypopnea index (AHI) baseline 32.2+/-18.1/h, constant CPAP 6.6+/-8.7, APAP(FOT) 5.5+/-3.8/h, P<0.001 baseline vs. each treatment mode). Under APAP(FOT), the sleep profile was normalized (S3/4 baseline 16.3+/-13.9% total sleep time (TST), APAP(FOT) 21.6+/-10.9% TST, P<0.05, rapid eye movement (REM) 14.2+/-6.7% TST vs. 20.3+/-7.3% TST, P<0.01), while with constant CPAP, a tendency towards improvement was found. The mean treatment pressure with APAP(FOT) was significantly lower than the constant CPAP (5.7+/-2.1 vs. 8.3+/-1.6 mbar, P<0.001).Conclusion: We conclude that APAP(FOT) is at least as effective as constant CPAP in normalizing sleep and breathing in OSAS.
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Affiliation(s)
- W J. Randerath
- Department of Pneumology, Allergology and Sleep Medicine, Klinik Ambrock, University Witten/Herdecke, Ambrocker Weg 60, D-58091, Hagen, Germany
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Younes M, Kun J, Masiowski B, Webster K, Roberts D. A method for noninvasive determination of inspiratory resistance during proportional assist ventilation. Am J Respir Crit Care Med 2001; 163:829-39. [PMID: 11282753 DOI: 10.1164/ajrccm.163.4.2005063] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Currently available noninvasive methods for measuring inspiratory resistance (RI) are difficult to implement or interpret during assisted mechanical ventilation on account of the confounding effect of respiratory efforts (Pmus). We propose a simple method consisting of brief reductions in airway pressure (Paw) in the early part of the inflation phase (pulse). Paw, flow (V), and volume (V) are measured at the beginning of the pulse (T (0)), at the trough of the pulse (TI) and at a point 0.1 s before T(0) (T(-1)). Equations of motion of the form [Pmus + Paw = V. K(1) + V (2). K(2) +V. E] are generated for the data at the three time points (E = elastance, K(1) and K(2) are Rohrer's constants). These three equations can be solved for K(1) and K(2) if it is arranged that the pulse has appropriate configuration and timing, and if it is assumed that DeltaPmus/Deltat is constant over the brief pulse period. The method was tested in 67 patients ventilated with proportional assist ventilation (PAV). The results were compared with those obtained using the interrupter technique during a period of controlled mechanical ventilation (CMV). RI, expressed at a standard flow of 1 L. s(-)(1), was slightly higher during PAV (16.4 +/- 4.9 versus 15.5 +/- 4.5 cm H(2)O. L(-1). s, p < 0.001). The average difference was 0.9 +/- 2.0 cm H(2)O. L(-1). s, corresponding to 5.4 +/- 12.6% of the average of RCMV and RPAV. The correlation coefficient was 0.92 (p = 8E-28) with a slope (1.01) and intercept (0.8) not significantly different from 1.0 and 0, respectively. We conclude that brief negative pulses applied early during the inflation phase can be used to provide reliable estimates of inspiratory resistance during PAV.
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Affiliation(s)
- M Younes
- Sections of Respiratory and Clinical Care Medicine, University of Manitoba, Winnipeg, Manitoba, Canada.
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Ficker JH, Wiest GH, Asshoff G, Fuchs FS, Schmelzer AH, Harsch IA, Hahn EG. Sensitivity of a simplified forced oscillation technique for detection of upper airway obstruction. RESPIRATION PHYSIOLOGY 2001; 124:243-9. [PMID: 11173078 DOI: 10.1016/s0034-5687(00)00199-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The sensitivity of a simplified variant of forced oscillation technique (FOT) was studied for assessment of dynamic upper airway obstruction during nasal continuous positive airway pressure (nCPAP) therapy for obstructive sleep apnoea (OSA). The airway impedance P[FOT] was measured by FOT and the oesophageal pressure (P(oes)) was recorded during stable stage II sleep in 11 patients with OSA. The CPAP level was initially set high enough to completely abolish upper airway obstruction. To induce gradually increasing upper airway re-obstruction, the CPAP pressure was then lowered stepwise. Thirty six such manoeuvres were analysed, blind, to define the first inspiration at which upper airway re-obstruction was detectable by analysis of P[FOT](t(FOT)) and by P(oes)(t(oes)), respectively. On seven occasions t(FOT) and t(oes) occurred together, in the remaining 29 cases t(FOT) preceded t(oes) with a mean latency of 6.0+/-7.7 (0-32) breath cycles. In no case did t(oes) preceed t(FOT). FOT is a highly sensitive tool for the assessment of incipient upper airway obstruction during nCPAP therapy.
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Affiliation(s)
- J H Ficker
- Medical Department I, Division of Respiratory Medicine, University of Erlangen-Nuremberg, Krankenhausstr. 12, 91054 Erlangen, Germany.
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21
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Navajas D, Farré R. Forced oscillation assessment of respiratory mechanics in ventilated patients. Crit Care 2001; 5:3-9. [PMID: 11178220 PMCID: PMC137264 DOI: 10.1186/cc972] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2000] [Revised: 10/24/2000] [Accepted: 10/28/2000] [Indexed: 11/23/2022] Open
Abstract
The forced oscillation technique (FOT) is a method for non-invasively assessing respiratory mechanics that is applicable both in paralysed and non-paralysed patients. As the FOT requires a minimal modification of the conventional ventilation setting and does not interfere with the ventilation protocol, the technique is potentially useful to monitor patient mechanics during invasive and noninvasive ventilation. FOT allows the assessment of the respiratory system linearity by measuring resistance and reactance at different lung volumes or end-expiratory pressures. Moreover, FOT allows the physician to track the changes in patient mechanics along the ventilation cycle. Applying FOT at different frequencies may allow the physician to interpret patient mechanics in terms of models with pathophysiological interest. The current methodological and technical experience make possible the implementation of portable and compact computerised FOT systems specifically addressed to its application in the mechanical ventilation setting.
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Affiliation(s)
- D Navajas
- Unitat de Biofisica i Bioenginyeria, Facultat de Medicina, Institut d'Investigacions Biomèdiques August Pi Sunyer, Universitat de Barcelona, Spain.
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22
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Randerath W, Parys K, Lehmann D, Sanner B, Feldmeyer F, Rühle KH. Self-adjusting continuous positive airway pressure therapy based on the measurement of impedance. A comparison of free pressure variation and individually fixed higher minimum pressure. Respiration 2000; 67:272-9. [PMID: 10867595 DOI: 10.1159/000029510] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Measurement of impedance using forced oscillation technique is a sensitive means of detecting airway obstructions, including the obstructive sleep apnea syndrome (OSAS). OBJECTIVE The present study was conducted to determine whether treatment with an automated impedance-controlled continuous positive airway pressure (CPAP) device (APAP(FOT)) is possible in patients with OSAS, and which is the best range of pressure variation in automatical CPAP treatment. We investigated two modes of APAP(FOT) with different pressure ranges: (1) the widest technically possible pressure range and (2) a range with individually defined minimum pressure. METHODS Ten patients [9 men, age 56.6+/-10.5 years, BMI 32.0+/-4.5 kg/m(2), apnea/hypopnea index (AHI) 18.2+/-13.3 /h] had a diagnostic polysomnography (baseline). After manual titration of positive airway pressure they were submitted, in randomized order, to two modes of the APAP(FOT) device, namely pressure range of 4.0- 15.5 mbar (mode 1 free range) and an individually fixed higher minimum pressure with a maximum pressure of 15.5 mbar (mode 2). RESULTS While the manually titrated pressure was 8.0+/-1.3 mbar, in mode 1 it was 5.6+/-2.1 mbar (p<0.01); in mode 2 7.3+/-1.6 mbar (p< 0.05). Both of these modes suppressed abnormal respiratory events (baseline AHI 18.2+/-13.3/h; mode 1: 2.5+/-1.9; mode 2: 1.8 +/-0.7, p<0.01 in each case), and increased slow wave sleep (baseline: 10.6+/-8.0%, mode 1: 20.2+/-10.4%, p<0.05; mode 2: 22.3+/-9.3%, p<0.01). In mode 1, the pressure was lower than that titrated manually in 73.2% of total sleep time, in mode 2 in 48.6%, while pressures higher than those derived manually were observed in 13.0% in mode 1 and in 19.1% in mode 2. CONCLUSIONS The data indicate that impedance-controlled CPAP (APAP(FOT)) allows adequate treatment of OSAS patients at significantly lower pressures as compared with manually titrated pressure. Differences between the two modes are only minor.
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Affiliation(s)
- W Randerath
- Klinik Ambrock/Hagen, Clinic for Pneumology, Allergology and Sleep Medicine, Witten/Herdecke University, Hagen, Germany
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MELO PEDROLOPESDE, WERNECK MARCELOMARTINS, GIANNELLA-NETO ANTONIO. Avaliação de mecânica ventilatória por oscilações forçadas: fundamentos e aplicações clínicas. ACTA ACUST UNITED AC 2000. [DOI: 10.1590/s0102-35862000000400007] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Requerendo apenas cooperação passiva e fornecendo novos parâmetros para análise da mecânica ventilatória, a técnica de oscilações forçadas (TOF) apresenta características complementares aos métodos clássicos de avaliação pulmonar. Neste trabalho, inicialmente é apresentada uma revisão dos princípios da técnica juntamente com uma discussão sobre suas vantagens e atuais limitações. A performance da técnica é comparada com a dos métodos clássicos na detecção de afecções respiratórias. As principais aplicações clínicas reportadas anteriormente na literatura, incluindo a avaliação da mecânica ventilatória infantil, estudos em neonatos, monitorização de pacientes sob ventilação mecânica, medicina ocupacional e avaliação de distúrbios no sono, são revisadas e discutidas. Com base na revisão efetuada e nos resultados obtidos em estudos efetuados em laboratório, os autores concluem que a TOF pode contribuir para um exame mais detalhado, assim como para facilitar a realização de testes de função pulmonar em condições nas quais as técnicas tradicionais não são adequadas.
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de Melo PL, Werneck MM, Giannella-Neto A. Effect of generator nonlinearities on the accuracy of respiratory impedance measurements by forced oscillation. Med Biol Eng Comput 2000; 38:102-8. [PMID: 10829399 DOI: 10.1007/bf02344697] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Measurements of respiratory impedance by means of the forced oscillation technique (FOT) are usually made using a loudspeaker as the excitation device. Its nonlinear nature can introduce artifacts that coincide with the frequencies applied to excite the respiratory system, limiting the accuracy of the impedance estimation. In this paper, this hypothesis is evaluated in the case of both a traditional estimator and the unbiased estimator proposed by Daróczy and Hantos (1982). A simulated study under apnoea conditions in the pressure range 0.5-3.0 cmH2O peak-to-peak reveals that loudspeaker nonlinearities introduce a characteristic pattern of dispersion in both the resistance and reactance curves that can be significantly decreased (p approximately equal to 0.03, signtest) by reducing the nonlinearities. A simulation of spontaneous breathing shows the same pattern, and is observed in the case of traditional as well as unbiased estimators. The dispersion is quantified by the mean absolute distance between the theoretical and simulated data and decreases with the reduction of nonlinearities when impedance is estimated with a traditional estimator (from 6.63 to 4.72% in real estimates and from 6.78 to 3.47% in imaginary estimates) as well as with an unbiased estimator (real estimates from 4.84 to 1.57% and 5.61 to 2.06% in imaginary estimates). Studies with normal subjects show the same dispersion pattern, which decreases if the generator nonlinearities are reduced. These results supply substantial evidence that reducing generator nonlinearities can contribute to the production of more reliable mechanical impedance FOT measurements.
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Affiliation(s)
- P L de Melo
- Metallurgical and Materials Engineering Program/COPPE, Federal University of Rio de Janeiro, Brazil
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25
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Badia JR, Farré RO, John Kimoff R, Ballester E, Hernández L, Rotger M, Navajas D, Montserrat JM. Clinical application of the forced oscillation technique for CPAP titration in the sleep apnea/hypopnea syndrome. Am J Respir Crit Care Med 1999; 160:1550-4. [PMID: 10556119 DOI: 10.1164/ajrccm.160.5.9902085] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
We have previously demonstrated that upper airway obstruction in sleep apnea/hypopnea syndrome (SAHS) can be accurately assessed in real-time by measuring respiratory impedance (|Z|) with the forced oscillation technique (FOT). The aims of the present study were: (1) to determine the feasibility of identifying the optimal continuous positive airway pressure (CPAP) for patients with SAHS based on analysis of the |Z| signal during conventional polysomnographic CPAP titration studies; and (2) to evaluate practical issues involved in the application of FOT during CPAP titration. We performed CPAP titration in 28 patients with SAHS during polysomnography (PSG) (14 nap and 14 full overnight studies) using a FOT system applied continuously to obtain an on-line measurement of |Z|. FOT was easily implemented and was well-tolerated by the patients. Optimal CPAP levels were determined both in the conventional manner from the standard PSG titration record and during a separate blinded analysis using the FOT signal alone. The mean conventional versus FOT-based optimal CPAP values were similar for both nap studies (10.6 +/- 0.6 [mean +/- SEM] versus 11.1 +/- 0.6 cm H(2)O, respectively, p = 0. 054) and overnight studies (9.9 +/- 0.7 versus 9.9 +/- 0.6 cm H(2)O, respectively, p = 1.00). Subsequent analysis of the PSG record with the FOT signal incorporated demonstrated that artefacts in the |Z| tracing occurred during mask leak, mouth breathing, and movement during arousal. Such abnormalities were readily identified from the flow tracing. These results indicate that, for adequate interpretation, the tracing and values of respiratory impedance obtained by FOT should be evaluated in conjunction with the flow signal. Continuous FOT-guided CPAP titration is feasible and may be a useful adjunct during manual titration. FOT could also potentially serve as the basis for automated CPAP in SAHS.
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Affiliation(s)
- J R Badia
- Servei de Pneumologia i Al.lèrgia Respiratòria, Departament de Medicina, Hospital Clínic, Laboratori de Biofísica i Bioenginyeria, Facultat de Medicina, Universitat de Barcelona, Barcelona, Spain
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26
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Randerath WJ, Parys K, Feldmeyer F, Sanner B, Rühle KH. Self-adjusting nasal continuous positive airway pressure therapy based on measurement of impedance: A comparison of two different maximum pressure levels. Chest 1999; 116:991-9. [PMID: 10531164 DOI: 10.1378/chest.116.4.991] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
STUDY OBJECTIVE Automatic titration using the forced oscillation technique (FOT) has recently been developed for the treatment of obstructive sleep apnea syndrome (OSAS). So far, it is not known if therapy with automatic nasal continuous positive airway pressure (nCPAP) using a preset upper pressure limitation or a free range (which might lead to higher mean pressure) is preferable with regard to obstructive events, sleep stages, and pressure characteristics. DESIGN After diagnostic polysomnography, patients were randomly assigned to two settings with the self-adjusting nCPAP (APAP) device based on the FOT. In mode 1, the pressure variation ranged from 4 to 15.5 cm H(2)O, and in mode 2, the pressure variation ranged from 4 cm H(2)O to an individual upper pressure limit. PATIENTS Eleven men, aged 53.0 +/- 6.8 years with a body mass index of 32.4 +/- 5.1 kg/m(2) and an apnea-hypopnea index (AHI) of 31.6 +/- 26.6/h. MEASUREMENTS AND RESULTS Manually titrated pressure was at 9.3 +/- 2.1 cm H(2)O, the mean pressure in mode 1 was 5.4 +/- 1.0 cm H(2)O (p < 0.01), and the mean pressure in mode 2 was 5.1 +/- 0.7 cm H(2)O (p < 0.01). A reduction of respiratory events (baseline AHI, 31.6 +/- 26.6/h; AHI in mode 1, 3.4 +/- 4.5; AHI in mode 2, 5.0 +/- 7.2; each with p < 0.001) and an increase in the "rapid eye movement" stage of sleep (baseline, 13.0 +/- 5.5%; mode 1, 22.0 +/- 7.7 [p < 0. 05]; mode 2, 23.0 +/- 7.9 [p < 0.01]) were achieved. In mode 1, the mean pressure was below the manual pressure 91.7 +/- 9.3% of the time, and in mode 2, the mean pressure was below the manual pressure 90.4 +/- 6.3% of the time. The manual pressure was exceeded by 5.5 +/- 7.4% (mode 1) and by 5.2 +/- 3.1% (mode 2). CONCLUSION We conclude that nCPAP therapy based on the FOT permits the adequate treatment of OSAS with significantly lower pressure than manually titrated nCPAP therapy does. A presetting of an upper pressure limit has no advantage compared to free range.
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Affiliation(s)
- W J Randerath
- Clinic Ambrock, Clinic for Pneumology, Allergology and Sleep Medicine , Hagen, Germany
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27
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Randerath WJ, Büscher L, Gil G, Domanski U, Rühle KH. Automatische nCPAP-Therapie auf der Basis der forcierten Oszillationstechnik (APAPFOT). SOMNOLOGIE 1999. [DOI: 10.1007/s11818-999-0034-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Navajas D, Farré R, Rotger M, Badia R, Puig-de-Morales M, Montserrat JM. Assessment of airflow obstruction during CPAP by means of forced oscillation in patients with sleep apnea. Am J Respir Crit Care Med 1998; 157:1526-30. [PMID: 9603133 DOI: 10.1164/ajrccm.157.5.9710026] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The forced oscillation technique (FOT) is a noninvasive method to measure respiratory resistance (Rrs) potentially useful for monitoring upper airway obstruction in patients with obstructive sleep apnea/hypopnea syndrome (SAHS). The aim of this work was to test the clinical suitability of FOT in assessing dynamic changes in airflow obstruction in patients with SAHS during continuous positive airway pressure (CPAP) and to investigate the CPAP dependence of Rrs. Forced oscillation (5 Hz) was applied to six male patients with SAHS submitted to CPAP titration procedure. Esophageal pressure was measured with a balloon-tipped catheter. Mid-inspiratory resistance (Rrs,i), mid-expiratory resistance (Rrs,e), and esophageal pressure swings (deltaPes) were computed for the respiratory events recorded at each CPAP level. Rrs,i decreased markedly and significantly from 36.0 +/- 4.0 cm H2O x s/L (mean +/- SEM) at baseline CPAP (4 cm H2O) to 13.1 +/- 2.8 cm H2O x s/L at optimal CPAP (11.3 +/- 0.4 cm H2O). Rrs,e showed a faster decrease with increasing CPAP reaching normal values at approximately 8 cm H2O. Rrs,i was strongly correlated (r2 = 0.94) with deltaPes. Our results suggest that FOT can be used as an alternative to the esophageal balloon for assessing airflow obstruction in patients with SAHS and for CPAP titration. Moreover, FOT allows us to detect phasic changes in resistance within the breathing cycle.
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Affiliation(s)
- D Navajas
- Lab. Biofísica i Bioenginyeria, Facultat de Medicina, Universitat de Barcelona, Spain
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29
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de Melo PL, Werneck MM, Giannella-Neto A. Linear servo-controlled pressure generator for forced oscillation measurements. Med Biol Eng Comput 1998; 36:11-6. [PMID: 9614742 DOI: 10.1007/bf02522851] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In respiratory input impedance measurements, the low-frequency range contains important clinical and physiological information. However, the patient's spontaneous ventilation can contaminate the data in this range, leading to unreliable results. Unbiased estimators are a good alternative to overcome this problem, provided that the generator is considered linear. This condition is not fulfilled by most existing generators as they are based on loudspeakers, which have strong nonlinearities. The present work aims to contribute to the solution of this problem, and describes a pressure generator that minimises the nonlinearities by an optical sensor placed in a position feedback loop. The static evaluation shows a high linearity for the optical system. The well known frequency response of pressure transducers is used in the dynamic evaluation of the instrument. The analysis of the generator shows that the use of position feedback improved the frequency response. The total harmonic distortion (THD) measurement shows that closed loop resulted in an effective decrease in the nonlinearities. The reduction of THD achieved by the servo-controlled generator can contribute to the practical implementation of the unbiased estimators, increasing the reliability of the impedance data, especially in the low-frequency range. This system is compared with conventional generators and with another servo-controlled system.
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Affiliation(s)
- P L de Melo
- Metallurgical and Materials Engineering Program/COPPE, Federal University of Rio de Janeiro, Brazil
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30
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Farré R, Rotger M, Montserrat JM, Navajas D. Analog circuit for real-time computation of respiratory mechanical impedance in sleep studies. IEEE Trans Biomed Eng 1997; 44:1156-9. [PMID: 9353995 DOI: 10.1109/10.641343] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The aim of this work was to develop a low-cost circuit for real-time analog computation of the respiratory mechanical impedance in sleep studies. The practical performance of the circuit was tested in six patients with obstructive sleep apnea. The impedance signal provided by the analog circuit was compared with the impedance calculated simultaneously with a conventional computerized system. We concluded that the low-cost analog circuit developed could be a useful tool for facilitating the real-time assessment of airway obstruction in routine sleep studies.
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Affiliation(s)
- R Farré
- Laboratori Biofísica i Bioenginyeria, Facultat de Medicina, Barcelona, Spain.
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31
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Harrington MG, McGeorge AP, Ballantyne JP, Beastall G. A prospective survey for insulinomas in a neurology department. Sleep Breath 1983; 22:673-681. [PMID: 29197986 PMCID: PMC6133118 DOI: 10.1007/s11325-017-1599-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 11/07/2017] [Accepted: 11/23/2017] [Indexed: 12/28/2022]
Abstract
Purpose Obesity is associated with both obstructive sleep apnea (OSA) and obesity hypoventilation. Differences in adipose tissue distribution are thought to underlie the development of both OSA and hypoventilation. We explored the relationships between the distribution of upper airway, neck, chest, abdominal and muscle fat in very obese individuals. Methods We conducted a cross-sectional cohort study of individuals presenting to a tertiary sleep clinic or for assessment for bariatric surgery. Individuals underwent magnetic resonance (MR) imaging of their upper airway, neck, chest, abdomen and thighs; respiratory polygraphy; 1 week of autotitrating CPAP; and morning arterial blood gas to determine carbon dioxide partial pressure and base excess. Results Fifty-three individuals were included, with mean age of 51.6 ± 8.4 years and mean BMI of 44.3 ± 7.9 kg/m2; there were 27 males (51%). Soft palate, tongue and lateral wall volumes were significantly associated with the AHI in univariable analyses (p < 0.001). Gender was a significant confounder in these associations. No significant associations were found between MRI measures of adiposity and hypoventilation. Conclusions In very obese individuals, our results indicate that increased volumes of upper airway structures are associated with increased severity of OSA, as previously reported in less obese individuals. Increasingly large upper airway structures that reduce pharyngeal lumen size are likely to lead to OSA by increasing the collapsibility of the upper airway. However, we did not show any significant association between regional fat distribution and propensity for hypoventilation, in this population. Electronic supplementary material The online version of this article (10.1007/s11325-017-1599-x) contains supplementary material, which is available to authorized users.
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