Subjects Breathing Research Articles

Influence of posture and gender on breathing pattern during quiet breathing in healthy subjects: a three-compartmental analysis

Influence of posture and gender on breathing pattern during quiet breathing in healthy subjects: a three-compartmental analysis

Correlated variability in the breathing pattern and end-expiratory lung volumes in conscious humans.

In order to characterize the variability and correlation properties of spontaneous breathing in humans, the breathing pattern of 16 seated healthy subjects was studied during 40 min of quiet breathing using opto-electronic plethysmography, a contactless technology that measures total and compartmental chest wall volumes without interfering with the subjects breathing. From these signals, tidal volume (VT), respiratory time (TTOT) and the other breathing pattern parameters were computed breath-by-breath together with the end-expiratory total and compartmental (pulmonary rib cage and abdomen) chest wall volume changes. The correlation properties of these variables were quantified by detrended fluctuation analysis, computing the scaling exponentα. VT, TTOT and the other breathing pattern variables showed α values between 0.60 (for minute ventilation) to 0.71 (for respiratory rate), all significantly lower than the ones obtained for end-expiratory volumes, that ranged between 1.05 (for rib cage) and 1.13 (for abdomen) with no significant differences between compartments. The much stronger long-range correlations of the end expiratory volumes were interpreted by a neuromechanical network model consisting of five neuron groups in the brain respiratory center coupled with the mechanical properties of the respiratory system modeled as a simple Kelvin body. The model-based α for VT is 0.57, similar to the experimental data. While the α for TTOT was slightly lower than the experimental values, the model correctly predicted α for end-expiratory lung volumes (1.045). In conclusion, we propose that the correlations in the timing and amplitude of the physiological variables originate from the brain with the exception of end-expiratory lung volume, which shows the strongest correlations largely due to the contribution of the viscoelastic properties of the tissues. This cycle-by-cycle variability may have a significant impact on the functioning of adherent cells in the respiratory system.

Deep breathing exercises with positive expiratory pressure in patients with multiple sclerosis - a randomized controlled trial.

Breathing exercises with positive expiratory pressure are often recommended to patients with advanced neurological deficits, but the potential benefit in multiple sclerosis (MS) patients with mild and moderate symptoms has not yet been investigated in randomized controlled trials. To study the effects of 2 months of home-based breathing exercises for patients with mild to moderate MS on respiratory muscle strength, lung function, and subjective breathing and health status outcomes. Forty-eight patients with MS according to the revised McDonald criteria were enrolled in a randomized controlled trial. Patients performing breathing exercises (n = 23) were compared with a control group (n = 25) performing no breathing exercises. The breathing exercises were performed with a positive expiratory pressure device (10-15 cmH2 O) and consisted of 30 slow deep breaths performed twice a day for 2 months. Respiratory muscle strength (maximal inspiratory and expiratory pressure at the mouth), spirometry, oxygenation, thoracic excursion, subjective perceptions of breathing and self-reported health status were evaluated before and after the intervention period. Following the intervention, there was a significant difference between the breathing group and the control group regarding the relative change in lung function, favoring the breathing group (vital capacity: P < 0.043; forced vital capacity: P < 0.025). There were no other significant differences between the groups. Breathing exercises may be beneficial in patients with mild to moderate stages of MS. However, the clinical significance needs to be clarified, and it remains to be seen whether a sustainable effect in delaying the development of respiratory dysfunction in MS can be obtained.

Correlation of Respirator Fit Measured on Human Subjects and a Static Advanced Headform

This study assessed the correlation of N95 filtering facepiece respirator (FFR) fit between a Static Advanced Headform (StAH) and 10 human test subjects. Quantitative fit evaluations were performed on test subjects who made three visits to the laboratory. On each visit, one fit evaluation was performed on eight different FFRs of various model/size variations. Additionally, subject breathing patterns were recorded. Each fit evaluation comprised three two-minute exercises: “Normal Breathing,” “Deep Breathing,” and again “Normal Breathing.” The overall test fit factors (FF) for human tests were recorded. The same respirator samples were later mounted on the StAH and the overall test manikin fit factors (MFF) were assessed utilizing the recorded human breathing patterns. Linear regression was performed on the mean log10-transformed FF and MFF values to assess the relationship between the values obtained from humans and the StAH.This is the first study to report a positive correlation of respirator fit between a headform and test subjects. The linear regression by respirator resulted in R2 = 0.95, indicating a strong linear correlation between FF and MFF. For all respirators the geometric mean (GM) FF values were consistently higher than those of the GM MFF. For 50% of respirators, GM FF and GM MFF values were significantly different between humans and the StAH. For data grouped by subject/respirator combinations, the linear regression resulted in R2 = 0.49. A weaker correlation (R2 = 0.11) was found using only data paired by subject/respirator combination where both the test subject and StAH had passed a real-time leak check before performing the fit evaluation. For six respirators, the difference in passing rates between the StAH and humans was < 20%, while two respirators showed a difference of 29% and 43%. For data by test subject, GM FF and GM MFF values were significantly different for 40% of the subjects. Overall, the advanced headform system has potential for assessing fit for some N95 FFR model/sizes.

Improved oxygenation during standing performance of deep breathing exercises with positive expiratory pressure after cardiac surgery: A randomized controlled trial.

Breathing exercises after cardiac surgery are often performed in a sitting position. It is unknown whether oxygenation would be better in the standing position. The aim of this study was to evaluate oxygenation and subjective breathing ability during sitting vs standing performance of deep breathing exercises on the second day after cardiac surgery. Patients undergoing coronary artery bypass grafting (n = 189) were randomized to sitting (controls) or standing. Both groups performed 3 × 10 deep breaths with a positive expiratory pressure device. Peripheral oxygen saturation was measured before, directly after, and 15 min after the intervention. Subjective breathing ability, blood pressure, heart rate, and pain were assessed. Oxygenation improved significantly in the standing group compared with controls directly after the breathing exercises (p < 0.001) and after 15 min rest (p = 0.027). The standing group reported better deep breathing ability compared with controls (p = 0.004). A slightly increased heart rate was found in the standing group (p = 0.047). After cardiac surgery, breathing exercises with positive expiratory pressure, performed in a standing position, significantly improved oxygenation and subjective breathing ability compared with sitting performance. Performance of breathing exercises in the standing position is feasible and could be a valuable treatment for patients with postoperative hypoxaemia.

“Ambient Fail” exception messages during breath testing of suspected impaired drivers using the Intoxilyzer® 5000C: a 10-year retrospective analysis

A retrospective analysis of the incidence of the “Ambient Failed” exception message (AFM) generated by the Intoxilyzer® 5000C was conducted during breath testing of suspected impaired drivers over a 10-year period. The incidence of an AFM occurred in only 2.5% (n = 531) of the 21,016 drivers that were tested. Breath tests containing two AFMs (n = 21; approx. 0.1%) were even less frequent. There was no main effect in the incidence of AFMs attributable either to year (p = 0.83), location of testing (p = 0.72), or to use of different instruments (p = 0.59). Additionally, there was no evidence of alcohol, or other interfering substances, in the ambient conditions that may have falsely elevated either the calibration checks or the subject breath test results. The occurrence of an AFM was associated with elevated blood alcohol concentrations (BACs) compared with BACs from test records that did not contain an AFM. The mean (± standard deviation) BAC from breath test records that contained at least one AFM and from those that did not was 208 mg/100 mL (± 68) and 150 mg/100 mL (± 54), respectively. Ambient conditions needed to generate an AFM during breath testing are transient in nature and the triggering of an AFM is more likely to occur in subjects with elevated BACs.

Effects of diaphragmatic contraction on lower limb venous return and central hemodynamic parameters contrasting healthy subjects versus heart failure patients at rest and during exercise.

The main objective was to assess the effects of abdominal breathing (AB) versus subject's own breathing on femoral venous blood flow (Qfv) and their repercussions on central hemodynamics at rest and during exercise contrasting healthy subjects versus heart failure (HF) patients. We measured esophageal and gastric pressure (PGA), Qfv and parameters of central hemodynamics in eight healthy subjects and nine HF patients, under four conditions: subject's own breathing and AB (∆PGA ≥ 6 cmH2O) at rest and during knee extension exercises (15% of 1 repetition maximum) until exhaustion. Qfv and parameters of central hemodynamics [stroke volume (SV), cardiac output (CO)] were measured using Doppler ultrasound and impedance cardiography, respectively. At rest, healthy subjects Qfv, SV, and CO were higher during AB than subject's breathing (0.11 ± 0.02 vs. 0.06 ± 0.00 L·min−1, 58.7 ± 3.4 vs. 50.1 ± 4.1 mL and 4.4 ± 0.2 vs. 3.8 ± 0.1 L·min−1, respectively, P ≤ 0.05). ∆SV correlated with ∆PGA during AB (r = 0.89, P ≤ 0.05). This same pattern of findings induced by AB was observed during exercise (SV: 71.1 ± 4.1 vs. 65.5 ± 4.1 mL and CO: 6.3 ± 0.4 vs. 5.2 ± 0.4 L·min−1; P ≤ 0.05); however, Qfv did not reach statistical significance. The HF group tended to increase their Qfv during AB (0.09 ± 0.01 vs. 0.07 ± 0.03 L·min−1, P = 0.09). On the other hand, unlike the healthy subjects, AB did not improve SV or CO neither at rest nor during exercise (P > 0.05). In healthy subjects, abdominal pump modulated venous return improved SV and CO at rest and during exercise. In HF patients, with elevated right atrial and vena caval system pressures, these findings were not observed.

Correlation study in respiration fluctuations during sleep stages.

Healthy sleep can be characterized by several stages: wake, light, SWS, and REM sleep. The clinical experts find that the breath of subjects is different in these sleep stages, but such observation is lacking data supporting, The statistical research about investigating breathing patterns during sleep process will be helpful for the sleep and breathing domain. The objective of the paper is to statistically analyze the respiratory characteristics during different sleep stages. Firstly, we calculated the mean value and standard deviation of respiratory rates of these stages, in which the respiratory rates were obtained by the autocorrelation method. Then the detrended fluctuation analysis (DFA) algorithm was applied to analyze long-range correlation of respiratory rates of sleep stages. The mean and standard deviation of respiratory rates are wake: 16.62 ± 2.43 cycles per minute (CPM), light: 15.15 ± 1.53 CPM, SWS: 15.06 ± 0.96 CPM and REM: 16.37 ± 2.03 CPM, respectively. The scaling exponent applied by detrended fluctuation analysis (DFA) algorithm reached about 0.7 for each stage. Results of the mean and standard deviation of respiratory rates show that different sleep stages lead to different autonomic regulations of breathing and exhibit different respiratory rates and fluctuations. And the DFA results demonstrate that respiratory rates are all long-range correlated in these stages although they lead to different fluctuation.

Sensitivity and specificity of hypopnoea detection using nasal pressure in the presence of a nasal expiratory resistive device (Provent®)

Nasal expiratory resistive valves (Provent®) have been proposed as novel therapy for obstructive sleep apnea. We compared pressure measurements from a standard nasal pressure catheter used to assess nasal airflow during sleep with those from nasal expiratory resistive device with attached proprietary nasal pressure cannula. Nasal pressure cannula or Provent® + proprietary nasal pressure cannula were attached to a bench model of human anterior nares and nasal passages, and pressure measured (P). Respiratory airflows generated by a subject breathing were applied to rear of model and airflow () measured via pneumotachograph. Airflow amplitude (Δ) was plotted against pressure amplitude (ΔP). Hypopnoea detection (<50% Δ) sensitivity and specificity was tested by expressing ΔP in terms of two reference breaths: reference breath 1, Δ 0.55 L s−1 = 100%; and reference breath 2, Δ 0.45 L s−1 = 100%. ΔP/Δ relationships were linear for Δ ≤ 0.55 L s−1; ΔP = 0.37ΔV + 0.16 (nasal pressure cannula), ΔP = 2.7ΔV + 0.12 (Provent® + proprietary nasal pressure cannula); both R2 > 0.65, p < 0.0001; p < 0.0001 for between slope difference). For nasal pressure cannula, specificity of hypopnoea detection differed between reference breaths one and two (80.2% and 40.0%, respectively), and Provent® + proprietary nasal pressure cannula (30.3% and 74.2%, respectively). Quantification of airflow obstruction in the presence of Provent® + proprietary nasal pressure cannula is greatly influenced by the reference breath chosen to determine a reduction in nasal airflow. Reported variability in therapeutic response to nasal expiratory resistive devices may relate to differences in measurement technique specificity used to quantify the severity of sleep disordered breathing.

Cyclic variation in heart rate score by holter electrocardiogram as screening for sleep-disordered breathing in subjects with heart failure.

Sleep-disordered breathing (SDB) is critically associated with cardiovascular mortality and morbidity, especially in patients with heart failure (HF). However, the majority of SDB patients remain undiagnosed. In contrast, abnormality in heart rate variability has been reported in patients with SDB. To explore an efficient electrocardiogram (ECG)-based screening tool for SDB, we examined the usefulness of cyclic variation in heart rate score (CVHRS) by Holter ECG in subjects with HF. In this study, 102 subjects with HF were enrolled. We simultaneously performed Holter ECG with overnight portable sleep monitoring, and we measured the respiratory disturbance index (RDI) and CVHRS. We determined the temporal position of the individual dips comprising the CVHRS using time-domain methods. CVHRS was measured as cyclic and autocorrelated dips in smoothed interbeat interval time series. There were 25 subjects with severe SDB (RDI ≥ 30 events/h) and 77 subjects with none-to-moderate SDB (0 ≤ RDI < 30 events/h). There was a significant positive correlation between CVHRS and RDI (r = 0.60, P < .001). In receiver operating characteristic analysis, CVHRS (cutoff of 30 events/h) identified severe SDB with a sensitivity of 82%, a specificity of 77%, and an area under the curve of 0.83. CVHRS determined by Holter ECG is a useful screening index for severe SDB in subjects with HF.

Nonlinear properties of cardiac rhythm and respiratory signal under paced breathing in young and middle-aged healthy subjects

We examined the effects of gender and age in young and middle-aged subjects on the level of cardio-respiratory interaction by analyzing properties of cardiac, respiratory and cardiac-respiratory regulatory mechanisms under paced breathing. In 56 healthy subjects, ECG (RR interval) and respiratory signal were simultaneously acquired in supine position at paced (0.1–0.45Hz, steps of 0.05Hz) and spontaneous breathing. The participants were divided into gender matched group of young adults (19–25 years old) and middle-aged adults (35–44 years old). Power spectral analysis was applied on RR interval time series and spectral components in very low frequency (VLF), low frequency (LF) and high frequency (HF) ranges were computed. We also calculated sample entropy of RR interval series (SampEnRR), respiratory series (SampEnResp), and their cross-sample entropy (cross-SampEn). Under paced breathing, reduction of all spectral powers with age (p<0.05) is not gender dependent but reduction of some entropy measures is; SampEnRR and SampEnResp were lower only in men (p<0.05). In the middle-aged subjects, effect of gender on spectral measures is significant; males had lower HF (p<0.05). Pattern of dependencies of SampEn and cross-SampEn on paced breathing frequency were significantly different in men (young vs. middle-aged, p=0.001 and p=0.037) and in middle-aged subjects (females vs. males, p=0.011 and p=0.008). In middle-aged males, lower entropy measures indicated reduced and less complex partial cardiac and respiratory control, and central cardio-respiratory control. In conclusion, in healthy middle-aged subjects changes in cardio-respiratory coupling are detectable only in males.

Pharyngeal airway volume and its relationship to the facial morphology in nasal breathing and mouth breathing subjects (A comparative computerized tomography study)

The value of lateral cephalometric radiographs to evaluate the pharyngeal airway is limited because it provided 2-dimensional (2D) images of complex 3-dimensional (3D) anatomic structures. Three dimensional analyses of the airway volumes are required to understand oral and pharyngeal adaptations in mouth breathing and nasal breathing subjects. The aim of this study was to measure the pharyngeal airway volume and the size of the face, then compare between pharyngeal airway volume in mouth breathing and nasal breathing subjects and find the gender difference in each group, also to study the relation between pharyngeal airway volume and the size of the face. Material and Methods: Fifty patients including 28 males and 22 females with an age ranged between 18-35 years suffered from clinical symptoms of nasal obstruction and mouth breathing was detected by otolaryngolog ist and sent to be imaged by Brilliance™ 64, Philips multi-detector computed tomography. Twenty normal subjects (10 males and 10 females) were selected as control. Angular and linear variables were measured in addition to the size of the face and the pharyngeal airway volume. Results: A statistically significant relationship between the pharyngeal airway volume and the mode of respiration and between pharyngeal airway volume and genders were detected. The pharyngeal airway volume was larger in nasal breathers than in mouth breathers and it was larger in males than in females. The size of the face was larger in males than females. Conclusion: CT volumetric images provide more reliable and accurate information for measurement of the pharyngeal airway volume, so the changes in the pharyngeal airway volume can be studied before and after surgery and this will aid in selection of the best treatment option in addition to control the relapse after orthodontic treatment with mouth breathing patients. Keyword: Pharyngeal airway volume, size of the face, mouth breathing, computerized tomography. (J Bagh Coll

Investigation of C3–C10 aldehydes in the exhaled breath of healthy subjects using selected ion flow tube-mass spectrometry (SIFT-MS)

Aldehydes have attracted great scientific and clinical interest as potential disease biomarkers. We have investigated selected ion flow tube-mass spectrometry (SIFT-MS) in detecting and quantifying C3 to C10 saturated aldehydes (propanal, butanal, pentanal, hexanal, heptanal, octanal, nonanal and decanal) from the exhaled breath of 26 healthy human volunteers. To assess the reliability of the Nalophan® bag sampling method employed, the water level in the breath sample was measured up to 4 h after collection and showed no significant degradation. Propanal was found to be the most abundant aldehyde in the exhaled breath of healthy volunteers. For the C4–C10 aldehydes, their median concentrations were all less than 3 ppbv, demonstrating only trace quantities are present in the exhaled breath of the 26 healthy volunteers.

Abraham Guz (1929-2014).

How do you describe a giant? As a person of abnormally great stature; above the usual size; or someone with much greater powers than the average person? Abraham Guz (‘Abe’) was not a tall man, but he was a scientific giant with an absolute desire to understand and find the scientific truth. This drive led him to make many original contributions in respiratory and cardiovascular physiology. Indeed, a simple literature search produces over 250 peer reviewed papers spanning some 50 years, the top 25 of which have been quoted over 2500 times. Moreover, most of his outstanding work was published in The Journal of Physiology, and we received it with gratitude because it was always insightful and ahead of its time. Many will argue that counting citations is a poor measure of scientific endeavour and I suspect Abe himself would certainly agree. However, this approach did provide us with a place to start when faced with the task of bringing together Abe's huge and varied scientific contributions.

A novel ultrasound technique to measure genioglossus movement in vivo.

Upper airway muscles are important in maintaining airway patency. Visualization of their dynamic motion should allow measurement, comparison, and further understanding of their roles in healthy subjects and those with upper airway disorders. Currently, there are few clinically feasible real-time imaging methods. Methods such as tagged magnetic resonance imaging have documented movement of genioglossus (GG), the largest upper airway dilator. Inspiratory movement was largest in the posterior region of GG. This study aimed to develop a novel ultrasound (US) method to measure GG movement in real time. We tested 20 healthy, awake subjects (21-38 yr) breathing quietly in the supine posture with the head in a neutral position. US images were collected using a transducer positioned submentally. Image correlation analysis measured regional displacement of GG within a grid of points in the midsagittal plane throughout the respiratory cycle. Typically, motion began before inspiratory flow in an anteroinferior direction and peaked in midinspiration. Average peak displacements of the anterior, posterior, superior, and inferior grid points were 0.44 ± 0.23 (mean ± SD), 0.57 ± 0.35, 0.38 ± 0.20, and 0.62 ± 0.41 mm, respectively. Largest displacements occurred in the most inferoposterior part (0.70 ± 0.48 mm). This method had good intrarater repeatability within the same testing session, as well as across sessions. We have devised a simple noninvasive US method, which should be a useful tool to assess GG movement in normal subjects and those with sleep-disordered breathing.

Impact of lower body negative pressure induced hypovolemia on peripheral venous pressure waveform parameters in healthy volunteers

Lower body negative pressure (LBNP) creates a reversible hypovolemia by sequestrating blood volume in the lower extremities. This study sought to examine the impact of central hypovolemia on peripheral venous pressure (PVP) waveforms in spontaneously breathing subjects. With IRB approval, 11 healthy subjects underwent progressive LBNP (baseline, −30, −75, and −90 mmHg or until the subject became symptomatic). Each was monitored for heart rate (HR), finger arterial blood pressure (BP), a chest respiratory band and PVP waveforms which are generated from a transduced upper extremity intravenous site. The first subject was excluded from PVP analysis because of technical errors in collecting the venous pressure waveform. PVP waveforms were analyzed to determine venous pulse pressure, mean venous pressure, pulse width, maximum and minimum slope (time domain analysis) together with cardiac and respiratory modulations (frequency domain analysis). No changes of significance were found in the arterial BP values at −30 mmHg LBNP, while there were significant reductions in the PVP waveforms time domain parameters (except for 50% width of the respiration induced modulations) together with modulation of the PVP waveform at the cardiac frequency but not at the respiratory frequency. As the LBNP progressed, arterial systolic BP, mean BP and pulse pressure, PVP parameters and PVP cardiac modulation decreased significantly, while diastolic BP and HR increased significantly. Changes in hemodynamic and PVP waveform parameters reached a maximum during the symptomatic phase. During the recovery phase, there was a significant reduction in HR together with a significant increase in HR variability, mean PVP and PVP cardiac modulation. Thus, in response to mild hypovolemia induced by LBNP, changes in cardiac modulation and other PVP waveform parameters identified hypovolemia before detectable hemodynamic changes.

Application of Linear-Frequency-Modulated Continuous-Wave (LFMCW) Radars for Tracking of Vital Signs

This paper focuses on the exploitation of linear-frequency-modulated continuous-wave (LFMCW) radars for noncontact range tracking of vital signs, e.g., respiration. Such short-range system combines hardware simplicity and tracking precision, thus outperforming other remote-sensing approaches in the addressed biomedical scenario. A rigorous mathematical analysis of the operating principle of the LFMCW radar in the context of vital-sign monitoring, which includes the explanation of key aspects for the maintenance of coherence, is detailed. A precise phase-based range-tracking algorithm is also presented. Exhaustive simulations are carried out to confirm the suitability and robustness against clutter, noise, and multiple scatterers of the proposed radar architecture, which is subsequently implemented at the prototype level. Moreover, live data from real experiments associated to a metal plate and breathing subjects are obtained and studied.

MO‐G‐18C‐03: Evaluation of Deformable Image Registration for Lung Motion Estimation Using Hyperpolarized Gas Tagging MRI

Purpose:Hyperpolarized gas (HP) tagging MRI is a novel imaging technique for direct measurement of lung motion during breathing. This study aims to quantitatively evaluate the accuracy of deformable image registration (DIR) in lung motion estimation using HP tagging MRI as references.Methods:Three healthy subjects were imaged using the HP MR tagging, as well as a high‐resolution 3D proton MR sequence (TrueFISP) at the end‐of‐inhalation (EOI) and the end‐of‐exhalation (EOE). Ground truth of lung motion and corresponding displacement vector field (tDVF) was derived from HP tagging MRI by manually tracking the displacement of tagging grids between EOI and EOE. Seven different DIR methods were applied to the high‐resolution TrueFISP MR images (EOI and EOE) to generate the DIR‐based DVFs (dDVF). The DIR methods include Velocity (VEL), MIM, Mirada, multi‐grid B‐spline from Elastix (MGB) and 3 other algorithms from DIRART toolbox (Double Force Demons (DFD), Improved Lucas‐Kanade (ILK), and Iterative Optical Flow (IOF)). All registrations were performed by independent experts. Target registration error (TRE) was calculated as tDVF – dDVF. Analysis was performed for the entire lungs, and separately for the upper and lower lungs.Results:Significant differences between tDVF and dDVF were observed. Besides the DFD and IOF algorithms, all other dDVFs showed similarity in deformation magnitude distribution but away from the ground truth. The average TRE for entire lung ranged 2.5−23.7mm (mean=8.8mm), depending on the DIR method and subject's breathing amplitude. Larger TRE (13.3–23.7mm) was found in subject with larger breathing amplitude of 45.6mm. TRE was greater in lower lung (2.5−33.9 mm, mean=12.4mm) than that in upper lung (2.5−11.9 mm, mean=5.8mm).Conclusion:Significant differences were observed in lung motion estimation between the HP gas tagging MRI method and the DIR methods, especially when lung motion is large. Large variation among different DIR methods was also observed.

Correlation of salivary alpha amylase level and adenotonsillar hypertrophy with sleep disordered breathing in pediatric subjects.

Obstructive sleep apnea syndrome (OSAS) and sleep disordered breathing (SDB) can affect the sympathetic adrenomedullary system (SAM). As a biomarker of SAM activity, salivary α-amylase (sAA) in pediatric subjects was evaluated whether it has any correlation with polysomnographic (PSG) parameters related to SDB. Sixty-seven children who attended our clinic during 1 year were enrolled prospectively and underwent clinical examinations and in-lab polysomnography. The sAA was measured at 2 points--at night before PSG and in the early morning after PSG. Subjects were divided into control (n = 26, apneahypopnea index [AHI] < 1) and OSAS (n = 41, AHI ≥ 1) groups. The OSAS group was subdivided according to AHI (mild-moderate, 1 ≤ AHI < 10; severe, AHI ≥ 10). The sAA subtraction and ratio (p = 0.014 and p < 0.001, respectively) were significantly higher in severe OSAS than in the mild-moderate and control groups. Although oxygen desaturation index (ODI) and AHI were significantly associated with sAA, sAA in the OSAS group was not related to lowest oxygen saturation or adenotonsillar hypertrophy. sAA was well related to polysomnographic (PSG) parameters related to SDB, such as AHI and ODI. Therefore, screening test for sAA in children suspected to have SBD may help to identify OSAS patients from control.

Evaluation of adherence to ambulatory liquid oxygen treatment: are commercialized dual-pressure transducers helpful?

Treatment adherence is widely recognized as a critical problem in long-term oxygen therapy, particularly in ambulatory liquid oxygen (LOX) systems. Adherence-monitoring strategies may be helpful in managing patients. We evaluated subjects' adherence to LOX using VisionOx and compared these results with the subjects' own adherence diaries and self-reported perceptions of use. Patients using LOX were recruited for a clinical interview; the number of days/week and the mean time of use according to subjects' perceptions were recorded. A 14-day diary was provided for every subject while VisionOx was attached to the LOX. VisionOx is a small device that uses pressure transducers to detect oxygen flow and the subject's breathing frequency. Information is stored and downloaded using dedicated software. Nineteen subjects were included (57.9% male with a median age of 63 years). When asked about the perception of LOX use, subjects self-reported using the device for a median of 100.0% of days (78.9% reported to have used it every day) for a median time of 180 min/day. According to data from VisionOx and subjects' diaries during the 14-day evaluation period, the median use was 92.8% of days for 210 min/day. No difference was found between the diaries and VisionOx data. Regarding subjects' perceptions of use, the declared use of LOX percent was significantly higher than reported in the diaries (P = .045) and VisionOx monitoring (P = .045) even though both underestimated the median use per day. Subjects overestimated adherence to LOX therapy (when measuring percent of days of use) compared to adherence diary and objective adherence monitoring. Because no significant difference was found comparing the diaries and VisionOx use, either may be helpful in clinical practice.