Subjects Breathing Research Articles

Measuring lung mechanics of expiratory tidal breathing with non-invasive breath occlusion

Background and objectiveLung mechanics measurements provide clinically useful information about disease progression and lung health. Currently, there are no commonly practiced methods to non-invasively measure both resistive and elastic lung mechanics during tidal breathing, preventing the important information provided by lung mechanics from being utilised. This study presents a novel method to easily assess lung mechanics of spontaneously breathing subjects using a dynamic elastance, single-compartment lung model.MethodsA spirometer with a built-in shutter was used to occlude expiration during tidal breathing, creating exponentially decaying flow when the shutter re-opened. The lung mechanics measured were respiratory system elastance and resistance, separated from the exponentially decaying flow, and interrupter resistance calculated at shutter closure. Progressively increasing resistance was added to the spirometer mouthpiece to simulate upper airway obstruction. The lung mechanics of 17 healthy subjects were successfully measured through spirometry.ResultsN = 17 (8 female, 9 male) healthy subjects were recruited. Measured decay rates ranged from 5 to 42/s, subjects with large variation of decay rates showed higher muscular breathing effort. Lung elastance measurements ranged from 3.9 to 21.2 cmH_2O/L, with no clear trend between change in elastance and added resistance. Resistance calculated from decay rate and elastance ranged from 0.15 to 1.95 cmH_2Os/L. These very small resistance values are due to the airflow measured originating from low-resistance areas in the centre of airways. Occlusion resistance measurements were as expected for healthy subjects, and increased as expected as resistance was added.ConclusionsThis test was able to identify reasonable dynamic lung elastance and occlusion resistance values, providing new insight into expiratory breathing effort. Clinically, this lung function test could impact current practice. It does not require high levels of cooperation from the subject, allowing a wider cohort of patients to be assessed more easily. Additionally, this test can be simply implemented in a small standalone device, or with standard lung function testing equipment.

Oxygen deficit is a sensitive measure of mild gas exchange impairment at inspired O2 between 12.5% and 21.

The oxygen deficit (OD) is the difference between the end-tidal alveolar Po2 and the calculated Po2 of arterial blood based on measured oxygen saturation that acts as a proxy for the alveolar-arterial Po2 difference. Previous work has shown that the alveolar gas meter (AGM100) can measure pulmonary gas exchange, via the OD, in patients with a history of lung disease and in normal subjects breathing 12.5% O2. The present study measured how the OD varied at different values of inspired O2. Healthy subjects were split by age (young 22-31; n = 23; older 42-90; n = 13). Across all inspired O2 levels (12.5, 15, 17.5, and 21%), the OD was higher in the older cohort 10.6 ± 1.0 mmHg compared with the young -0.4 ± 0.6 mmHg (P < 0.0001, using repeated measures ANOVA), the difference being significant at all O2 levels (all P < 0.0001). The OD difference between age groups and its variance was greater at higher O2 values (age × O2 interaction; P = 0.002). The decrease in OD with lower values of inspired O2 in both cohorts is consistent with the increased accuracy of the calculated arterial Po2 based on the O2-Hb dissociation curve and with the expected decrease in the alveolar-arterial Po2 difference due to a lower arterial saturation. The persisting higher OD seen in older subjects, irrespective of the inspired O2, shows that the measurement of OD remains sensitive to mild gas exchange impairment, even when breathing 21% O2.

Printed, Soft, Nanostructured Strain Sensors for Monitoring of Structural Health and Human Physiology.

Soft strain sensors that are mechanically flexible or stretchable are of significant interest in the fields of structural health monitoring, human physiology, and human-machine interfaces. However, existing deformable strain sensors still suffer from complex fabrication processes, poor reusability, limited adhesion strength, or structural rigidity. In this work, we introduce a versatile, high-throughput fabrication method of nanostructured, soft material-enabled, miniaturized strain sensors for both structural health monitoring and human physiology detection. Aerosol jet printing of polyimide and silver nanowires enables multifunctional strain sensors with tunable resistance and gauge factor. Experimental study of soft material compositions and multilayered structures of the strain sensor demonstrates the capabilities of strong adhesion and conformal lamination on different surfaces without the use of conventional fixtures and/or tapes. A two-axis, printed strain gauge enables the detection of force-induced strain changes on a curved stem valve for structural health management while offering reusability over 10 times without losing the sensing performance. Direct comparison with a commercial film sensor captures the advantages of the printed soft sensor in enhanced gauge factor and sensitivity. Another type of a stretchable strain sensor in skin-wearable applications demonstrates a highly sensitive monitoring of a subject's motion, pulse, and breathing, validated by comparing it with a clinical-grade system. Overall, the presented comprehensive study of materials, mechanics, printing-based fabrication, and interfacial adhesion shows a great potential of the printed soft strain sensor for applications in continuous structural health monitoring, human health detection, machine-interfacing systems, and environmental condition monitoring.

Low-cost, easy-to-build noninvasive pressure support ventilator for under-resourced regions: open source hardware description, performance and feasibility testing.

AimCurrent pricing of commercial mechanical ventilators in low-/middle-income countries (LMICs) markedly restricts their availability, and consequently a considerable number of patients with acute/chronic respiratory failure cannot be adequately treated. Our aim was to design and test an affordable and easy-to-build noninvasive bilevel pressure ventilator to allow a reduction in the serious shortage of ventilators in LMICs.MethodsThe ventilator was built using off-the-shelf materials available via e-commerce and was based on a high-pressure blower, two pressure transducers and an Arduino Nano controller with a digital display (total retail cost <75 USD), with construction details provided open source for free replication. The ventilator was evaluated, and compared with a commercially available device (Lumis 150 ventilator; Resmed, San Diego, CA, USA): 1) in the bench setting using an actively breathing patient simulator mimicking a range of obstructive/restrictive diseases; and b) in 12 healthy volunteers wearing high airway resistance and thoracic/abdominal bands to mimic obstructive/restrictive patients.ResultsThe designed ventilator provided inspiratory/expiratory pressures up to 20/10 cmH2O, respectively, with no faulty triggering or cycling; both in the bench test and in volunteers. The breathing difficulty score rated (1–10 scale) by the loaded breathing subjects was significantly (p<0.005) decreased from 5.45±1.68 without support to 2.83±1.66 when using the prototype ventilator, which showed no difference with the commercial device (2.80±1.48; p=1.000).ConclusionThe low-cost, easy-to-build noninvasive ventilator performs similarly to a high-quality commercial device, with its open-source hardware description, which will allow for free replication and use in LMICs, facilitating application of this life-saving therapy to patients who otherwise could not be treated.

Physiologic Effects of High-Flow Nasal Cannula in Healthy Subjects.

High-flow nasal cannula (HFNC) is increasingly used in the management of acute and chronic respiratory failure. Little is known about the optimal settings for HFNC. This study was designed to assess the dose effect of HFNC on respiratory effort indexes and respiratory patterns in spontaneously breathing adults. A randomized controlled crossover study was conducted in 10 healthy subjects. Five experimental conditions were evaluated: baseline with no therapy; 5 L/min with conventional nasal prongs; and HFNC at 20, 40, and 60 L/min. The primary outcomes were the indexes of respiratory effort (ie, esophageal pressure swing [ΔPes], esophageal pressure-time product, and work of breathing). Secondary outcomes included breathing pattern parameters and blood gases. Dead-space ventilation and washout were calculated based on minute ventilation, breathing frequency, and Radford equations. ΔPes increased from median (interquartile range [IQR] 3.2 (2.2-3.6) cm H2O at baseline to median (IQR) 5.7 (4.6-6.8) cm H2O at 60 L/min (P < .001). Neither esophageal pressure-time product nor work of breathing were modified during the tested conditions. The minute volume was significantly reduced at 40 and 60 L/min compared with baseline (P = .04), mostly driven by an important and dose-dependent reduction in breathing frequency, from median (IQR) 16 (15-18) breaths/min at baseline, to median (IQR) 8 (7-10) breaths/min at 60 L/min (P < .001). Capillary [Formula: see text] was stable in all the tested conditions. The calculated dead-space ventilation was reduced by half with HFNC. HFNC did not significantly modify work of breathing in healthy subjects. However, a significant reduction in the minute volume was achieved, capillary [Formula: see text] remaining constant, which suggests a reduction in dead-space ventilation with flows > 20 L/min. (ClinicalTrials.gov registration NCT02495675).

Oxygen Deficit Is a Sensitive Measure of Mild Gas Exchange Impairment at Inspired O2 between 12.5%–21%

The oxygen deficit (OD) is the difference between the end‐tidal alveolar PO2 and the estimated PO2 of arterial blood derived from the SpO2 that has the potential to be used clinically as a proxy for the alveolar‐arterial PO2 difference. Previous work has shown that a recently developed technology, the Alveolar Gas Meter, is accurate in measuring the efficiency of pulmonary gas exchange, via the OD, in patients with a history of lung disease as well as in normal subjects breathing a hypoxic mixture of 12.5% O2. This study sought to determine how the OD varied as the percent of inspired O2 changed from 21% to 12.5% in 36 healthy subjects split by age (young 22–31, n=23; old 42–90, n=13) to assess the possibility of use in a clinical setting. The PO2 and PCO2 were continually measured as the subject breathed through a mouthpiece using rapidly responding electrochemical cells, and the end‐tidal PO2 and PCO2 were calculated and averaged over 5 steady‐state breaths, while a fingertip pulse oximeter measured the SpO2. After correcting for any change in P50 resulting from the PCO2 differing from 40 mmHg, the arterial PO2 was calculated from the SpO2 by inverting the Hill‐equation. Subjects breathed 12.5, 15, 17.5 and 21% oxygen mixtures (balanced order) and their OD was measured in triplicate. Across all inspired O2 levels, the OD was higher in the older cohort than the young (p &lt;0.0001, repeated measures ANOVA, Table 1). The older cohort had a larger OD at all four oxygen levels (all p&lt;0.0001), with that difference and its variance being greater at higher inspired O2 values (age × O2 interaction p=0.002). The OD at an inspired O2 of 12.5% was significantly less than at 21% for both age cohorts. This is consistent with the known increase in ventilation‐perfusion mismatching that occurs in healthy aging. The decrease in OD magnitude as the inspired oxygen was reduced in both cohorts is consistent with the increased accuracy of the estimated arterial PO2 when based on saturation values on the steep part of the O2‐Hb dissociation curve. Further, as arterial saturation decreases there is an expected decrease in the alveolar‐arterial PO2 difference. The persisting higher OD seen in older subjects, irrespective of inspired O2, suggests that the measurement of oxygen deficit remains sensitive to mild gas exchange impairment, even when breathing air (21% O2).Support or Funding InformationFinancial support from UCSD Measured Oxygen Deficit by Age Young Old p‐value All Inspired O2 (mean±SE) −0.4±0.6 10.6±1.0 &lt;0.0001 Inspired O2 by Age Interaction 0.002 12.5% −1.4±0.7 5.7±0.6 ‐ 15% −2.7±1.0 5.2±1.8 15% vs 12.5%: NS 17.5% −2.7±1.0 9.4±1.8 17.5% vs 12.5%: NS 21% 5.1±1.3 21.9±2.1 21% vs 12.5%: &lt;0.0001

Non-invasive prediction of lung cancer histological types through exhaled breath analysis by UV-irradiated electronic nose and GC/QTOF/MS

Lung cancer (LC) is one of the most lethal diseases from the last decades. Accurate diagnosis of LC histology could lead to the prescription of personalized medical treatment to the affected subjects, which could reduce the mortality rate. We present here an experimental study performed in the pulmonology units of three hospitals from Morocco to non-invasively detect LC and predict LC histology via the analysis of the volatile organic compounds (VOCs) emitted through breathing. Gas chromatography coupled to a quadrupole time-of-flight mass spectrometer (GC/QTOF/MS) employed to detect the breath VOCs, revealed 30 discriminative VOCs in the breath of healthy subjects and LC patients; among them, 4 unique breath VOCs were found for the first time in the breath of LC patients, and could be used as new biomarkers for future LC diagnosis. Besides, an electronic nose (e-nose) system using a novel sensing technique in breath analysis, based on UV-irradiation of the gas sensors, was employed to characterize the overall composition of the collected breath samples, providing a satisfactory discrimination between the breath patterns of LC patients and healthy subjects. Importantly, the e-nose could further discriminate with high accuracy between the two types of LC (non-small cell LC and small cell LC), as well as between two of the major subtypes of non-small cell LC, namely squamous cell carcinoma (SCC) and adenocarcinoma (ADC). The reported results prove that breath analysis with chemical gas sensors and analytical techniques can provided an accurate mean for the non-invasive diagnosis of LC and LC histology.

Oxygen Conservation Methods With Automated Titration.

Oxygen titration is recommended to avoid hyperoxemia and hypoxemia. Automated titration, as well as the [Formula: see text] target, may have an impact on oxygen utilization, with potential logistical effects in emergency and military transportation. We sought to assess the oxygen flow required for different [Formula: see text] targets in spontaneously breathing subjects, and to evaluate individualized automated oxygen titration to maintain stable oxygenation in subjects with COPD and healthy subjects with induced hypoxemia. In the first part of the study, oxygen flow was evaluated in hospitalized subjects for different [Formula: see text] targets from 90% to 98%. Oxygen requirements to reach these targets were determined using a device that automatically adjusts oxygen flow every second on the basis of the [Formula: see text] target. In the second part of the study, the same automated oxygen titration method was used to correct hypoxemia in subjects with COPD and in healthy subjects with induced hypoxemia while the subjects wore a gas mask. Oxygen flow, [Formula: see text], and heart rate were continuously recorded. Thirty-six spontaneously breathing hospitalized subjects were included in the first part of the study. Oxygen flow was reduced more than 6-fold when the [Formula: see text] target was decreased from 98% to 90%. The second part of the study included 15 healthy and 9 subjects with stable COPD. In healthy subjects, heterogeneous oxygen flows were required to correct induced hypoxemia (0.2-2.5 L/min). In subjects with COPD, oxygen flow varied from 0 L/min (in 9 of 18 tested conditions) to 2.9 L/min. Significant reductions in the amount of oxygen delivered could be obtained with optimized [Formula: see text] targets. Oxygen delivery through a gas mask to correct hypoxemia is feasible, and automated oxygen titration may help individualize oxygen administration and reduce oxygen utilization. (ClinicalTrials.gov registration: NCT02782936, NCT02809807.).

New mHealth application software based on myofunctional therapy applied to sleep-disordered breathing in non-compliant subjects

BackgroundMyofunctional therapy (MT) is a therapeutic option with demonstrated efficacy for treating sleep-disordered breathing. We assessed the clinical application of a newly developed m-Health App, which aimed to allow patients with OSAHS (obstructive sleep apnea/hypopnea syndrome) to perform oropharyngeal exercises only by interacting with their smartphone without no other devices.MethodsWe offered to treat the OSAHS of 20 patients with the App for 90 sessions. Inclusion criteria were adult patients diagnosed with OSAHS who rejected, or could not tolerate or afford treatment for their OSAHS with other modalities. The App was used by 15 patients, while 5 were noncompliant and then were used as a control group. Polygraphy was performed at the beginning of the study, and after 90 sessions in the App group or after 3 months in the control group. Data for adherence to treatment, sex, body mass index (BMI), age, O2MIN (oxygen minimal saturation) and apnea–hypopnea index (AHI) were collected for both groups.Results15 (75%) patients showed adherence to the treatment as measured as performing the exercises daily 5 days a week. In patients who performed the exercises, AHI decreased from 25.78 ± 12.6 to 14.1 ± 7,7 (p = 0.002), Epworth changed from 18,2 ± 1,98 to 14,2 ± 7,7(p = 0,002) and (O2MIN) changed from 84,87 ± 7.02 to 89,27 ± 3,77 (p = 0.0189). In the control group, there was no significant change.ConclusionsTo our knowledge, this is the first study reported where a mHealth App based on MT could be by itself a therapeutic option in selected patients with OSAHS.

Sequential analysis of heart rate variability, blood pressure variability and baroreflex sensitivity in healthy pregnancy.

The aim of this study was to demonstrate the temporal profile of changes in heart rate variability (HRV), blood pressure variability (BPV), and cardiac baroreflex sensitivity (BRS) during the course of a healthy pregnancy. This was a longitudinal study during which autonomic variability parameters (HRV, BPV, BRS) were assessed in 66 pregnant women at 11-13, 20-22 and 30-32weeks of gestation. A lead II electrocardiogram tracing and beat-to-beat blood pressure were recorded with the subject breathing spontaneously in the supine position. Changes in the parameters were analyzed using repeated measures analysis of variance. Overall HRV (SDNN; standard deviation of all NN intervals) was found to decrease significantly over the course of pregnancy (p < 0.05). Similarly, indices which represent the parasympathetic component of these variables (SDSD [standard deviation of differences between adjacent NN intervals]; pNN50 [NN50 count {number of pairs of adjacent NN intervals differing by more than 50 ms} divided by the total number of all NN intervals]; high-frequency [HF] power) were also found to decrease significantly from the first to third trimester of pregnancy (p < 0.05). Low-frequency (LF) power increased over the course of pregnancy (p < 0.05). The LF/HF ratio increased significantly from first to third trimester of pregnancy (median: 0.66 [first trimester] vs.1.02 [second] vs. 0.91 [third]; p < 0.05) Overall BPV increased during the course of pregnancy, with a significant rise in the HF component of BPV and a significant fall in the LF component of BPV with advancing gestation (p < 0.05). BRS decreased over the course of pregnancy (median: 16.31, interquartile range [IQR] 11.04-23.13 [first trimester] vs. 11.42, IQR 8.54-19.52 [second] vs. 8.84, IQR 7.15-12.45 [third] ms/mmHg; p < 0.05). Pregnancy is associated with decreased vagal and increased sympathetic modulation of cardiac autonomic tone with advancing gestation, together with increased BPV. The reduction in cardiac BRS may play a role in increasing BPV and decreasing HRV over the course of pregnancy.

Feasibility study of surface motion tracking with millimeter wave technology during radiotherapy.

Continuous monitoring of patient movement is crucial to administering safe radiation therapy (RT). Conventional optical approaches often cannot be used when the patient's surface is blocked by immobilization devices. Millimeter waves (mmWaves) are capable of penetrating nonconductive objects. In this study, we investigated using mmWave technology to monitor patient surface displacements, as well as breathing and cardiac phases, through clothing and body fixtures. A mmWave device was mounted inside the bore of a ring-based radiotherapy linear accelerator and pointed at a reflective surface on top of the couch. Measurements were obtained at displacements of 10, 7.5, 5.0, 2.5, and 1.0mm at heights 100, 150, and 200 mm below isocenter. Submillimeter displacements were performed at a height of 200mm. Additionally, millimeter and submillimeter displacements were measured with and without a gown and body mold placed between the surface and the sensor. The device was programmed to transmit chirp signals at 77-81GHz. The subject's surface was detected by fast Fourier transform (FFT) of the reflected chirp signal within a rough range bin. Fine displacements within that range bin were calculated through phase extraction and phase demodulation. The displacement data were sent through two separate bandpass filters with passbands of 0.1-0.6 and 0.8-2.0Hz to obtain the subject's breathing and cardiac waveforms, respectively. The breathing and cardiac measurements were compared to those of a Vernier Respiration Monitor Belt and an electrocardiogram (EKG), respectively, to assess validity. The device was able to detect millimeter and submillimeter displacements as small as 0.1mm, as well as monitor displacement with an accuracy within 1mm in the presence of an obstructive object. The device's breathing and cardiac waveforms exhibited a strong phase correlation between the respiration monitor belt (ρ=0.9156) and EKG (ρ=0.7895), respectively. The mmWave device can monitor surface displacements with an accuracy better than 0.1mm without obstructions and better than 1mm with obstructions. It can also provide real-time monitoring of breathing and cardiac waveforms simultaneously with high correlation with traditional respiratory and cardiac monitoring devices. Overall, mmWave technology demonstrates potential for motion monitoring in the field of radiation oncology.

Sleep Disturbances During Pregnancy and Adverse Maternal and Fetal Outcomes: A Systematic Review and Meta-Analysis

Background: Sleep disturbances are highly prevalent in pregnancy and are frequently overlooked as a potential cause of significant morbidity. The association between sleep disturbances and pregnancy outcomes remains largely controversial and needs to be clarified to guide management. We conducted a systematic review and meta-analyses to investigate the association between sleep disturbances and maternal and fetal adverse outcomes. Methods: We searched PubMed, Embase and Web of Science from inception to May 31, 2019, for observational English studies of pregnant women with and without sleep disturbances assessing the risk of obstetric complications in the antenatal, intrapartum or postnatal period, and neonatal complications. We used Newcastle-Ottawa Scales to assess the methodological quality of included studies. We quantified the risks of maternal and fetal complications by comparing pregnant women with and without sleep disturbances and undertook subgroup analyses and meta-regression stratified by several clinical and demographic characteristics. We pooled the associations as odds ratios (OR) and 95% confidence intervals (CI) using fixed-effect or random-effect models as appropriate based on the heterogeneity test. Findings: We included 114 studies with a total of 58,100,274 pregnant women in this meta-analysis. Sleep disturbances were assessed, including poor sleep quality, extreme sleep duration, insomnia, restless legs syndrome, subjective sleep-disordered breathing and diagnosed obstructive sleep apnea. Women with overall sleep disturbances versus those without had a significantly higher risk of pre-eclampsia (OR=2·81, 95% CI:2·38-3·32), gestational hypertension (1·74, 1·54-1·98), gestational diabetes mellitus (1·60, 1·45-1·77), cesarean section (1·50, 1·33-1·69), preterm birth (1·41, 1·27-1·56), large for gestational age (1·40, 1·11-1·77), and stillbirth (1·25, 1·08-1·45), but not low birth weight (1·27, 0·98-1·64), or small for gestational age (1·06, 0·92-1·21). Sleep disturbances were related to higher risks of morbidities in pregnant women who are 30 years or older and overweight before pregnancy. Interpretation: Significant associations exist between sleep disturbances in pregnancy and a variety of adverse maternal and fetal outcomes. Sleep disturbances are treatable and deserve more attention from health-care providers during counseling and should be a part of prenatal health care. Funding Statement: The National Key Research and Development Program of China (no. 2019YFA0706200), and the NSFC-CIHR Joint Health Research Program (no. 81761128036). Declaration of Interests: The authors declare they have no conflicts of interest. Ethics Approval Statement: The study protocol was registered with PROSPERO, number CRD42020148586.

Assessment of Nasal Breathing Using Lip Taping: A Simple and Effective Screening Tool

Objectives: Subjective assessment of nasal obstruction with patient-reported outcome measures such as visual analogue scale and NOSE score may be limited in chronic mouth breathing subjects who are not consciously aware of nasal breathing difficulties. This study investigates a simple objective screening tool to assess the capacity for comfortable nasal breathing that is based on sealing the lips and mouth with tape and assessing whether the subject can breathe comfortably through the nose for up to three minutes. Method: Cross-sectional, multi-center cohort study with 663 participants (ages: 3-83 years, 50.5% female). Lips were gently sealed using MicroPore paper tape; timer was used to assess how long the participants were able to breathe comfortably through the nose for up to 180 seconds. Other measures included subjective rating of perceived difficulty with nasal breathing (VAS, 0-100) as well as self-assessed reports of mouth breathing. Results: There were 9.3% of patients with subjective reports of moderate to severe nasal obstruction (VAS> 50) and 17.2% of patients with predominance of self-reported mouth breathing in this series. Overall, 93.4% of participants successfully passed the nasal breathing test. Among patients with habitual mouth breathing, 83.5% (91/109) were able to breathe comfortably through the nose when instructed to do so for the entire 3-minute duration tested. Similarly, there were 67% (40/59) patients with VAS score >50 who could breathe comfortably through the nose for >180 seconds despite subjective reports of moderate to severe nasal obstruction. Participants unable to breathe exclusively through the nose for 180 seconds had increased likelihood of mouth breathing while awake (OR 4.12, 95% confidence interval 2.14-7.89, p<.0001) as well as increased odds of mouth breathing while asleep (OR 3.05, 95% confidence interval 1.61-5.72, p=0.0003). Conclusion: Objectively testing whether a subject can breathe through the nose with the lips and mouth taped for three minutes can identify patients at risk of mouth breathing and is a simple and effecting screening tool to distinguish organic nasal obstruction from functional mouth breathing habit and or nasal resistance.

A Preprocess Method of External Disturbance Suppression for Carotid Wall Motion Estimation Using Local Phase and Orientation of B-Mode Ultrasound Sequences.

Estimating the motions of the common carotid artery wall plays a very important role in early diagnosis of the carotid atherosclerotic disease. However, the disturbances caused by either the instability of the probe operator or the breathing of subjects degrade the estimation accuracy of arterial wall motion when performing speckle tracking on the B-mode ultrasound images. In this paper, we propose a global registration method to suppress external disturbances before motion estimation. The local vector images, transformed from B-mode images, were used for registration. To take advantage of both the structural information from the local phase and the geometric information from the local orientation, we proposed a confidence coefficient to combine them two. Furthermore, we altered the speckle reducing anisotropic diffusion filter to improve the performance of disturbance suppression. We compared this method with schemes of extracting wall displacement directly from B-mode or phase images. The results show that this scheme can effectively suppress the disturbances and significantly improve the estimation accuracy.

Reference value for expiratory time constant calculated from the maximal expiratory flow-volume curve

BackgroundThe expiratory time constant (RCEXP), which is defined as the product of airway resistance and lung compliance, enable us to assess the mechanical properties of the respiratory system in mechanically ventilated patients. Although RCEXP could also be applied to spontaneously breathing patients, little is known about RCEXP calculated from the maximal expiratory flow-volume (MEFV) curve. The aim of our study was to determine the reference value for RCEXP, as well as to investigate the association between RCEXP and other respiratory function parameters, including the forced expiratory volume in 1 s (FEV1)/ forced vital capacity (FVC) ratio, maximal mid-expiratory flow rate (MMF), maximal expiratory flow at 50 and 25% of FVC (MEF50 and MEF25, respectively), ratio of MEF50 to MEF25 (MEF50/MEF25).MethodsSpirometric parameters were extracted from the records of patients aged 15 years or older who underwent pulmonary function testing as a routine preoperative examination before non-cardiac surgery at the University of Tokyo Hospital. RCEXP was calculated in each patient from the slope of the descending limb of the MEFV curve using two points corresponding to MEF50 and MEF25. Airway obstruction was defined as an FEV1/FVC and FEV1 below the statistically lower limit of normal.ResultsWe retrospectively analyzed 777 spirometry records, and 62 patients were deemed to have airway obstruction according to Japanese spirometric reference values. The cut-off value for RCEXP was 0.601 s with an area under the receiver operating characteristic curve of 0.934 (95% confidence interval = 0.898–0.970). RCEXP was strongly associated with FEV1/FVC, and was moderately associated with MMF and MEF50. However, RCEXP was less associated with MEF25 and MEF50/MEF25.ConclusionsOur findings suggest that an RCEXP of longer than approximately 0.6 s can be linked to the presence of airway obstruction. Application of the concept of RCEXP to spontaneously breathing subjects was feasible, using our simple calculation method.

Mapping regional strain in anesthetised healthy subjects during spontaneous ventilation

IntroductionBreathing produces a phenomenon of cyclic deformation throughout life. Biomechanically, deformation of the lung is measured as strain. Regional strain recently started to be recognised as a tool in the...

Time-based pulmonary features from electrical impedance tomography demonstrate ventilation heterogeneity in chronic obstructive pulmonary disease.

Pulmonary electrical impedance tomography (EIT) is a functional imaging technique that allows real-time monitoring of ventilation distribution. Ventilation heterogeneity (VH) is a characteristic feature of chronic obstructive pulmonary disease (COPD) and has previously been quantified using features derived from tidal variations in the amplitude of the EIT signal. However, VH may be better described by time-based metrics, the measurement of which is made possible by the high temporal resolution of EIT. We aimed 1) to quantify VH using novel time-based EIT metrics and 2) to determine the physiological relevance of these metrics by exploring their relationships with complex lung mechanics measured by the forced oscillation technique (FOT). We performed FOT, spirometry, and tidal-breathing EIT measurements in 11 healthy controls and 9 volunteers with COPD. Through offline signal processing, we derived 3 features from the impedance-time (Z-t) curve for each image pixel: 1) tE, mean expiratory time; 2) PHASE, mean time difference between pixel and global Z-t curves; and 3) AMP, mean amplitude of Z-t curve tidal variation. Distribution was quantified by the coefficient of variation (CV) and the heterogeneity index (HI). Both CV and HI of the tE and PHASE features were significantly increased in COPD compared with controls, and both related to spirometry and FOT resistance and reactance measurements. In contrast, distribution of the AMP feature showed no relationships with lung mechanics. These novel time-based EIT metrics of VH reflect complex lung mechanics in COPD and have the potential to allow real-time visualization of pulmonary physiology in spontaneously breathing subjects.NEW & NOTEWORTHY Pulmonary electrical impedance tomography (EIT) is a real-time imaging technique capable of monitoring ventilation with exquisite temporal resolution. We report novel, time-based EIT measurements that not only demonstrate ventilation heterogeneity in chronic obstructive pulmonary disease (COPD), but also reflect oscillatory lung mechanics. These EIT measurements are noninvasive, radiation-free, easy to obtain, and provide real-time visualization of the complex pathophysiology of COPD.

Sleep-disordered breathing in cystic fibrosis pediatric subjects.

ObjectivesTo describe the frequency of sleep-disordered breathing (SDB) in pediatric cystic fibrosis (CF) and to study associations between polysomnographic respiratory parameters and available clinical information.MethodsThis was a retrospective, cross-sectional study. The sample data were obtained from information recorded on patient charts in 2015 and 2016. The study included all individuals with CF aged from 2 to 20 years for whom records were available for polysomnography performed within the previous two years. ResultsSixteen individuals with CF (mean age 11 ± 5.6 years old) were included. Polysomnographic respiratory parameter abnormalities were defined as an apnea-hypopnea index (AHI) exceeding one event per hour of sleep or an oxyhemoglobin saturation (SpO2) nadir below 90%; observed in 10 subjects (62.5%). Forced expiratory volume in first second (FEV1) was correlated (r=0.602, p=0.023) with mean sleep SpO2. FEV1 was also negatively correlated with sleep peak end-tidal carbon dioxide (EtpCO2) (r=-0.645, p=0.024). Additionally, chronic airway colonization by Pseudomonas aeruginosa was associated with mean EtpCO2 in non-REM sleep (p=0.024). DiscussionSDB was frequently observed in this sample of children with CF. There was an association between CF respiratory disease progression markers and sleep breathing parameters in children. Sleep studies appear to be an important tool for assessment of the respiratory status of these individuals with CF, although further studies are needed, especially with carbon dioxide sleep analysis.

Early medical therapy for acute laryngeal injury (ALgI) following endotracheal intubation: a protocol for a prospective single-centre randomised controlled trial

IntroductionRespiratory failure requiring endotracheal intubation accounts for a significant proportion of intensive care unit (ICU) admissions. Little attention has been paid to the laryngeal consequences of endotracheal intubation. Acute laryngeal...

GEP-based predictive modeling of breathing resistances of wearing respirators on human body via sEMG and RSP sensors

PurposeBreathing resistance is the main factor that influences the wearing comfort of respirators. This paper aims to demonstrate the feasibility of using the gene expression programming (GEP) for the purpose of predicting subjective perceptions of breathing resistances of wearing respirators via surface electromyography (sEMG) and respiratory signals (RSP) sensors.Design/methodology/approachThe authors developed a physiological signal monitoring system with a specific garment. The inputs included seven physical measures extracted from (RSP) and (sEMG) signals. The output was the subjective index of breathing resistances of wearing respirators derived from the category partitioning-100 scale with proven levels of reliability and validity. The prediction model was developed and validated using data collected from 30 subjects and 24 test combinations (12 respirator conditions × 2 motion conditions). The subjects evaluated 24 conditions of breathing resistances in repeated measures fashion.FindingsThe results show that the GEP model can provide good prediction performance (R2 = 0.71, RMSE = 0.11). This study demonstrates that subjective perceptions of breathing resistance of wearing respirators on the human body can be predicted using the GEP via sEMG and RSP in real-time, at little cost, non-invasively and automatically.Originality/valueThis is the first paper suggesting that subjective perceptions of subjective breathing resistances can be predicted from sEMG and RSP sensors using a GEP model, which will remain helpful to the scientific community to start further human-centered research work and product development using wearable biosensors and evolutionary algorithms.