The test-retest reliability of gas exchange kinetics in humans using a pseudo random binary sequence exercise test.

Patients with cystic fibrosis (CF) have been shown to exhibit impaired oxygen uptake (VO2) kinetics independent of their physical fitness. This study investigated whether oxygen supplementation improves VO2 kinetics in CF as determined by cycle ergometry at submaximal exercise intensities using a pseudo-random binary sequence exercise test i.e. a simultaneous application of different frequencies of sinusoidal work. The subjects were 9 CF patients and 13 healthy controls (HC) and they exercised while breathing humidified and heated air with a fractional concentration of oxygen in inspired air (F(I)O2) of either 0.21 or 0.40. With a F(I)O2 of 0.21 the respiratory exchange ratio (R) was higher in CF than in HC both at rest (0.91 vs 0.81) and during exercise (0.97 vs 0.89). Oxygen saturation (SO2) was slightly lower in CF. but remained above 90% during exercise (92.7% vs 95.2%). Spectrum analysis revealed that in CF, the amplitude ratio (AR) between V02 and exercise intensity was lower over a wide frequency range (P < 0.05). In addition, CF showed a larger negative phase shift (PS) at lower frequencies (P < 0.005). With a F(I)O2 of 0.40, SO2 increased to about 97% in both groups; while R remained higher in CF (0.92) compared to HC (0.81). In the control group, the O2 supplement raised AR but the VO, kinetics of the CF patients were not significantly affected. In HC the enhanced AR during oxygen supplementation would suggest a cardiopulmonary limitation of VO2 at the onset of submaximal exercise. In CF patients low AR and PS would indicate an attenuated VO2 response attributable to an impaired oxygen utilization in the muscles because the oxygen supplement normalised SO2 but failed to improve R and VO2 kinetics.

The dynamics of ventilation (VE), oxygen uptake (VO2), carbon dioxide output (VCO2), and heart rate (fc) were studied in 12 healthy young men during upright and supine exercise. Responses to maximal and to two different types of submaximal exercise tests were contrasted. During incremental exercise to exhaustion, the maximal work rate, VO2max, VEmax, fc,max, and ventilatory threshold were all significantly reduced in supine compared to upright exercise (P less than 0.01-0.001). Following step increases or decreases in work rate between 25 W and 105 W, both VO2 and VCO2 responded more slowly in supine than upright exercise. Dynamics were also studied in two different pseudorandom binary-sequence (PRBS) exercise tests, with the work rate varying between 25 W and 105 W with either 5-s or 30-s durations of each PRBS unit. In both of these tests, there were no differences caused by body position in the amplitude or phase shifts obtained from Fourier analysis for any observed variable. These data show that the body position alters the dynamic response to the more traditional step increase in work rate, but not during PRBS exercise. It is speculated that the elevation of cardiac output observed with supine exercise in combination with the continuously varying work-rate pattern of the PRBS exercise allowed adequate, perhaps near steady-state, perfusion of the working muscles in these tests, whereas at the onset of a step increase in work rate, greater demands were placed on the mechanisms of blood flow redistribution.

Activities of daily living are characterized by continuous changes in exercise intensity and duration resulting in many abrupt changes in metabolic demand. The ability to readily meet these demands is described by the rate of adaptation in oxygen uptake measured at either the mouth (VO2p) or at the site of active muscle. Many studies have used a single step transition to assess this rate of adaptation. However, a continually changing exercise, such as a pseudorandom binary sequence (PRBS) protocol, provides more transition phases to analyze. We examined the VO2p and microvascular oxygenation responses using near infrared spectroscopy (NIRS) during PRBS exercise. Five healthy males (30 ± 6 yrs, 83.4 ± 20.9 kg, VO2pk, 38.9 ± 5.9 mL/kg/min; mean ± SD) completed a ramp exercise to fatigue for the determination of the lactate threshold (LT) and peak VO2p (VO2pk). Each bout of PRBS exercise transitioned from a baseline of 20 W to a WR corresponding to either 90% of LT (MOD, 100 ± 7 W)) or to a WR at 40% of the difference between LT and VO2pk (HVY, 173 ± 13 W). The PRBS exercise consisted of 30 units of 15 s that alternated between BSL and the higher WR in a pseudorandom pattern; the pattern was repeated 3 times. VO2p was measured breath-by-breath using a metabolic cart and interpolated to 1 s intervals. For each subject and WR, the 3 repetitions for each trial were ensembled averaged yielding a single 450 s response. Changes in hemoglobin oxygenation (deoxy-[Hb+Mb]) and total hemoglobin concentration ([THC]) were measured from the vastus lateralis (VL) using frequency-domain NIRS. Data were collected at 1 Hz and ensembled averaged to yield a single 450 s response. VO2p and deoxy-[Hb+Mb] responses were transformed into the frequency domain and analyzed using standard approaches and the mean-normalized gain (MNG). The harmonic amplitudes (Amph) for VO2p/WR were lower (p<0.05) during HVY at 0.0067 Hz (Mod, 56.9 ± 13.0 %; HVY, 49.3 ± 6.8 %), 0.011 Hz (Mod, 37.6 ± 17.0 %, HVY: 25.8 ± 5.7 %) and 0.013 Hz (Mod, 33.2 ± 12.8 %; HVY, 15.8 ± 10.2 %). The Amph for deoxy-[Hb+Mb]/WR were lower (p<0.05) for VO­2p/WR in HVY compared to MOD (Mod, 39.5 ± 6.0 %; HVY, 30.2 ± 3.9 %). MNG was also lower (p<0.05) for deoxy-[Hb+Mb]/WR in HVY compared to MOD (Mod, 77.4 ± 26.6 %; HVY, 47.3 ± 10.0 %). The VO2p and deoxy-[Hb+Mb] responses from a PRBS trial represent the responses to individual sinusoidal inputs at each frequency tested. The normalized Amph and MNG measured in the current study described the temporal dynamics of the variables of interest (i.e., VO2p and deoxy-[Hb+Mb]). The results of the current study showed a significant decrease in both normalized Amph and MNG for VO2p and deoxy-[Hb+Mb] suggesting that exercise performed above the LT results in a slowing of both the VO2p and microvascular deoxy-[Hb+Mb] responses. These findings are consistent with previous studies demonstrating a slowing of VO2p above the LT. Compared to studies using a single step protocol, responses to PRBS protocols include many transition periods to identify potential control mechanisms that are more discernable during non-steady state exercise.

Recent studies have demonstrated that on-transient oxygen uptake (VO2) kinetics are slowed when constant-load exercise is initiated from the upper compared to lower region of the moderate intensity domain (below the lactate threshold, LT). These studies, focusing exclusively on lower limb exercise, attributed this intensity-dependent slowing of VO2 kinetics during moderate-intensity exercise to different muscle fiber recruitment patterns or altered oxygen transport dynamics. PURPOSE: To determine if pulmonary VO2 and heart rate (HR) kinetics are slowed during constant-load arm exercise (arm-cranking) performed in the upper (90%LT) compared to lower (45%LT) regions of the moderate intensity domain. METHODS: Seven healthy male subjects (26 ± 3 yr) performed 4-8 repetitions of arm-cranking exercise involving: 1) a single, 6-min step transition from 9 W to 90% of the estimated LT (AC90%); two continuous, equal, 6-min step transitions from 9 W to 45% LT (AC45%), and then to 90% LT (AC45-90%); and 3) the AC90% protocol superimposed upon low-intensity leg-cycling (AC90%+LC), where baseline HR >100 beats·min-1 (range: 100-120 beats·min-1). RESULTS: The time constants (t) of the VO2 and HR responses were longer (P<0.05) during AC45-90% (tVO2: 70 ± 5 s; tHR: 59 ± 4 s) compared to AC45% (tVO2: 54 ± 6 s; tHR: 47 ± 5 s) and AC90% (tVO2: 53 ± 4 s; tHR: 46 ± 3 s). The gain (DVO2/DW) and blood lactate concentration were also significantly greater (P<0.05) for AC45-90% than AC45%. During arm-cranking superimposed upon leg-cycling (AC90%+LC), HR kinetics were significantly slowed when compared to AC90% (mean difference for tHR: 9 ± 4 s, P<0.05) and AC45% (mean difference for tHR: 9 ± 5 s, P<0.05). Similar comparisons between conditions for tVO2 yielded no significant differences. CONCLUSION: During arm exercise performed within the moderate intensity domain, VO2 and HR kinetics do not conform to a dynamically linear model. Since HR, but not VO2 kinetics were slowed during AC90%+LC, factors other than convective oxygen delivery (e.g. those intrinsic to the exercising muscle) may explain the slower VO2 response in the upper reaches of the moderate intensity domain for arm exercise.

We present an integrable solution for the detection of defective sensor elements using sigma-delta-(/spl Sigma//spl Delta/)-modulation and a matched filter. The sensor element is stimulated using a pseudo random binary sequence (PRBS). The sensor signal is read out and the analog output is digitized using a /spl Sigma//spl Delta/-modulator. The binary pulse density stream of the /spl Sigma//spl Delta/-modulator is the output of the sensor system and thus should ideally contain the PRBS. A matched filter has the task of detecting the pseudo random sequence in the pulse density stream and its sampled output is compared to a threshold thus making it possible to judge the functionality of the sensor element. By evaluating the magnitude of the matched filter output it is also possible to measure the sensor sensitivity. We present a discrete solution of this method, but an integrated chip using a standard 1.2 /spl mu/m CMOS process has been designed and is being fabricated.

The tolerance profile for very‐heavy intensity exercise is well described by a hyperbola with two parameters: a curvature constant (W′) and a power asymptote (CP). During cycle ergometry, where work efficiency is similar between subjects, the tolerable duration (tlim) is highly dependent on the rate at which oxidative ATP synthesis rises to meet the demand. We were therefore interested in the relationship between pulmonary oxygen uptake (VO2) kinetics and the power‐duration hyperbola. We hypothesized that CP (the upper limit for steady‐state VO2) would relate to the fundamental VO2 time‐constant (τ), and W′ to the slow component magnitude (ΔVO2sc). Eight males performed repeats of constant work‐rate (WR) cycle ergometry to tlim: 1) over a range of WRs to estimate CP and W′ and 2) with WR normalized to induce intolerance in 6 min (WR6; for τ and ΔVO2sc). VO2 was measured breath‐by‐breath using a turbine and mass spectrometer. Tolerance at WR6 averaged 365 ± 17 s. CP (range 181–289 W) was inversely correlated (R2 = 0.37) with τ (21.3‐30.5 s); and W′ (12.8‐27.3 kJ) was strongly and directly correlated (R2 = 0.97) with ΔVO2sc (370–940 ml/min). Therefore, a fast τVO2 was associated with a high CP thereby maximizing the WR for a given O2 deficit, whilst a high rate of anaerobiosis ‐ reflected in W′ ‐ resulted in a large ΔVO2sc. Together, this suggests that VO2 kinetics are a major determinant of tolerance during very‐heavy intensity exercise.

Prolonged recovery of cardiac output after maximal exercise in patients with chronic heart failure

With the increasing reliance on technology, it has become crucial to secure every aspect of online information where pseudo random binary sequences (PRBS) can play an important role in today’s world of Internet. PRBS work in the fundamental mathematics behind the security of different protocols and cryptographic applications. This paper proposes a new PRBS namely MK (Mamun, Kumu) sequence for security applications. Proposed sequence is generated by primitive polynomial, cyclic difference set in elements of the field and binarized by quadratic residue (QR) and quadratic nonresidue (QNR). Introduction of cyclic difference set makes a special contribution to randomness of proposed sequence while QR/QNR-based binarization ensures uniformity of zeros and ones in sequence. Besides, proposed sequence has maximum cycle length and high linear complexity which are required properties for sequences to be used in security applications. Several experiments are conducted to verify randomness and results are presented in support of robustness of the proposed MK sequence. The randomness of proposed sequence is evaluated by popular statistical test suite, i.e., NIST STS 800-22 package. The test results confirmed that the proposed sequence is not affected by approximations of any kind and successfully passed all statistical tests defined in NIST STS 800-22 suite. Finally, the efficiency of proposed MK sequence is verified by comparing with some popular sequences in terms of uniformity in bit pattern distribution and linear complexity for sequences of different length. The experimental results validate that the proposed sequence has superior cryptographic properties than existing ones.

Non-intrusive estimation of oxygen uptake (V̇O2) is possible with wearable sensor technology and artificial intelligence. V̇O2 kinetics have been accurately predicted during moderate exercise using easy-to-obtain sensor inputs. However, V̇O2 prediction algorithms for higher intensity exercise with inherent nonlinearities are still being refined. The purpose of this investigation was to test if a machine learning model can accurately predict dynamic V̇O2 across exercise intensities, including slower V̇O2 kinetics normally observed during heavy- compared to moderate-intensity exercise. Fifteen young healthy adults (7 females; peak V̇O2: 42±5 mL·min-1·kg-1) performed three different pseudorandom binary sequence (PRBS) exercise tests ranging in intensity from low-to-moderate, low-to-heavy, and ventilatory threshold-to-heavy work rates. A temporal convolutional network was trained to predict instantaneous V̇O2, with model inputs including heart rate, percent heart rate reserve, estimated minute ventilation, breathing frequency, and work rate. Frequency domain analyses between V̇O2 and work rate were used to evaluate measured and predicted V̇O2 kinetics. Predicted V̇O2 had low bias (-0.017 L·min-1, 95% limits of agreement: [-0.289, 0.254]), and was very strongly correlated (rrm=0.974, p<0.001) with the measured V̇O2. The extracted indicator of kinetics, mean normalized gain (MNG), was not different between predicted and measured V̇O2 responses (main effect: p=0.374, ηp2=0.01), and decreased with increasing exercise intensity (main effect: p<0.001, ηp2=0.64). Predicted and measured V̇O2 kinetics indicators were moderately correlated across repeated measurements (MNG: rrm=0.680, p<0.001). Therefore, the temporal convolutional network accurately predicted slower V̇O2 kinetics with increasing exercise intensity, enabling non-intrusive monitoring of cardiorespiratory dynamics across moderate- and heavy-exercise intensities.

Slowed kinetics of the primary phase (tau-p), and/or increased slow component (SC), of oxygen uptake (VO2) during heavy exercise, are associated with early fatigue. Previous reports suggest that infusion of N-acetylcysteine (NAC; a nonspecific antioxidant) reduces specific muscle fatigue, but effects of NAC on time-to-fatigue (TTF) during whole body exercise are equivocal. If NAC delays muscle fatigue during whole body exercise, this might be associated with improved VO2 kinetics (faster tau-p, reduced SC) during heavy exercise. PURPOSE: To determine the effect of an acute oral dose of NAC on VO2 kinetics during heavy cycling exercise. METHODS: Eight healthy men (22+/−2 yrs; VO2peak: 43+/−5 ml/kg/min) initially completed an incremental cycle VO2peak test. Subjects then performed a randomized, double blind crossover study where subjects were given either placebo (PLA) or NAC (1800 mg) 45 min prior to a constant load (~85% VO2peak) cycle exercise test to volitional fatigue. Tests were separated by one week. VO2 kinetics were described using a standard 3-exponential function. RESULTS: There was no effect of NAC to extend time to fatigue (PLA: 1263 +/− 334 s; NAC: 1047 +/− 136 s, P>0.05). Neither tau-p (PLA: 43.9 +/− 17.3 s; NAC: 35.4 +/− 14.7 s) nor amplitude of SC (PLA: 0.43 +/− 0.17 L/min; NAC: 0.52 +/− 0.19 L/min) were significantly affected by NAC (P>0.05 for both). However, the change in tau-p with NAC was inversely related to the change in the SC (r= −0.78, P=0.025) and positively related to the change in amplitude of the primary component (r=0.73, P=0.025). CONCLUSIONS: These results suggest that an acute dose of NAC had no effect on time to fatigue during heavy exercise. However, in some subjects NAC altered both the primary and SC of VO2 kinetics in a complex, interrelated manner.

A number of studies have illustrated that blood flow restricted (BFR) resistance training increasing muscle function even when low-intensity training is utilized. Recently BFR has also applied to aerobic training; however less is known about the effect of aerobic training with BFR on the oxygen uptake (VO2) kinetic responses during exercise with or without BFR. PURPOSE: To elucidate the effects of 8-weeks cycle training with BFR on VO2 kinetics at the onset of constant-load cycle exercise with or without BFR. METHODS: Eighteen healthy subjects were randomly assigned to BFR (n = 9; 22±5 yrs) or no BFR group serving as the control (CON; n = 9; 21±2 yrs). Both groups trained for 30 minutes, 3 days/week for 8 weeks. BFR was performed for 5 minutes every 10 minutes by applying cuffs to the upper thighs. Breath-by-breath VO2 was measured during the performance of 5-min moderate intensity (below the lactate threshold) or 6-min heavy intensity exercise (above the lactate threshold) without BFR at Pre-, 4 weeks after (Mid-), and Post-training. At Post, we also measured VO2 kinetics during exercise with BFR (Post+BFR). Two-way repeated ANOVAs were used (BFR vs CON and Pre vs Mid vs Post vs Post+BFR) with significance accepted as p<0.05; and Tukey’s post hoc tests utilized as needed. RESULTS: Although time constant (τ) of VO2 kinetics at the fast component during moderate exercise fitted the exponential model was significantly faster in Mid and Post than that of Pre (26.8 to 16.3 and 15.5 s and 27.5 to 22.1 and 18.5 s in BFR and CON, p<0.05, respectively), significant group-by-time interaction was not detected. The amplitude of the VO2 slow component during heavy exercise significantly decreased in Mid and Post than that of Pre (281 to 103 and 128 mL/min and 300 to 154 and 160 mL/min in BFR and CON, p<0.05, respectively), while a significant group-by-time interaction was not detected. Both τ of VO2 kinetics during moderate exercise and the amplitude of the VO2 slow component during heavy exercise significantly increased from Post to Post+BFR (19.1 and 28.0 s, and 266 and 256 mL/min in BFR and CON, p<0.05, respectively); however significant group-by-time interactions were not detected either. CONCLUSION: Appling the BFR to eight-weeks cycle training showed no further change in VO2 kinetics at the onset of exercise. Supported by KAKENHI (23700788)

Battery energy storage is becoming a vital part of green energy systems. Prediction of the state of health of energy storage systems is difficult as it relies on a number of parameters. Pseudo Random Binary Sequence (PRBS) excitation of energy storage batteries has been shown to be a valid method of battery parameter identification for lead acid batteries [1]. The purpose of this work is to validate PRBS test data from a 3Ah LiFePO4 cell forming part of an EV battery-pack cell against Electrochemical Impedance Spectroscopy (EIS) data obtained from an industry-standard potentiostat (Solartron 1480). PRBS results are obtained in under 200 seconds on easily reproducible equipment which can be built into a green energy battery management system, while the EIS process takes over two hours on prohibitively expensive laboratory equipment. This work validates PRBS as a fast and portable method of obtaining the impedance spectrum of Lithium Ion cells, which can then be used to obtain information about SoH of the BESS.

PreviousNext No AccessSEG Technical Program Expanded Abstracts 1992Porosity, permeability, and shear strength (P*2S) cross‐well tomography experiments of a noisy foundationAuthors: Tokuo YamamotoThomas NyeMurat KuruT. SakakiO. HashimotoI. OkumuraTokuo YamamotoUniv. of Miami, Thomas NyeUniv. of Miami, Murat KuruUniv. of Miami, T. SakakiKawasaki Steel Corp., Japan, O. HashimotoKawasaki Steel Corp., Japan, and I. OkumuraKawasaki Steel Corp., Japanhttps://doi.org/10.1190/1.1822095 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Permalink: https://doi.org/10.1190/1.1822095FiguresReferencesRelatedDetails SEG Technical Program Expanded Abstracts 1992ISSN (print):1052-3812 ISSN (online):1949-4645Copyright: 1992 Pages: 1410 publication data© 1992 Copyright © 1992 Society of Exploration GeophysicistsPublisher:Society of Exploration Geophysicists HistoryPublished: 10 Feb 2005 CITATION INFORMATION Tokuo Yamamoto, Thomas Nye, Murat Kuru, T. Sakaki, O. Hashimoto, and I. Okumura, (1992), "Porosity, permeability, and shear strength (P*2S) cross‐well tomography experiments of a noisy foundation," SEG Technical Program Expanded Abstracts : 378-381. https://doi.org/10.1190/1.1822095 Plain-Language Summary PDF DownloadLoading ...

The investigation of patients who are unable to fixate the pattern visual stimulus generally requires the use of diffuse flash stimulation to elicit the visual evoked response. However, by comparison with pattern, flash stimulation has proved relatively insensitive in identifying lesions of the visual pathway. We investigated a more complex method of flash stimulation. A pseudorandom binary sequence has been used to generate the diffuse visual evoked response stimulus. The pseudorandom binary sequence, rather than producing a single flash, switches in a pseudorandom fashion between two levels of illumination. The result is a diffuse visual stimulus approximating band-limited white noise. The series is periodic, enabling signal averaging to be performed. By applying the methods of random signal analysis, the impulse or transient response of the visual pathway can be determined. Our normal pseudo-random binary sequence visual evoked response impulse function, derived from 29 normal subjects, had the morphologic characteristics of the conventional flash visual evoked response and a major positive component (P100), whose latency mean and standard deviation closely matched that of our normative pattern visual evoked response. However, the P100 amplitude standard deviation was significantly greater than that produced by conventional pattern and flash stimulation. We investigated 140 patients by means of pattern, flash and pseudorandom binary sequence stimulation. The pseudorandom binary sequence visual evoked response proved to be almost 12 times more effective than flash visual evoked response in detecting lesions of the visual system.

The multifrequent pseudorandom binary sequence (PRBS) technique is a useful tool for studying oxygen uptake (VO2) kinetics within the aerobic range. However, the validity of this multifrequent test may be limited by nonlinearities generated by the circulatory and pulmonary system. To check for such nonlinear effects, we compared the frequency responses computed from two PRBS protocols with the results of pure sinusoidal frequencies varying in amplitude and mean values (periods between 50 s and 450 s). According to our results the VO2 frequency response does not seem to depend on the type of testing--PRBS or sine--or the changes within each test, i.e. mean power and power amplitude of the sine tests and the switching frequency of the PRBS. In the range of higher frequencies small differences between the test conditions may have been obscured by the greater scatter of dynamic responses. It was concluded that the VO2 frequency response was quasi-linear for periods down to the least 100 s. However, even in this range nonlinearities can be provoked by rest-exercise transitions, by a varying contribution of lactate or by an insufficient noise reduction.