Effect Of Breathing Frequency Research Articles

Computational fluid dynamics simulation of full breathing cycle for aerosol deposition in trachea: Effect of breathing frequency

Abstract Aerosols have been widely used in the treatment of certain airway diseases. With different breathing conditions of patients, the flow pattern might not cause the aerosol to transport and deposit on the desired bronchial section. In this study, computational fluid dynamics simulations based on the Euler–Euler method were successfully used to evaluate the airflow behavior when an electrostatic charge was present. The three-dimensional domain was acquired and derived from the computed tomography scan of the patient. Three breathing frequencies were investigated. The instantaneous contour plot revealed that the particles migrated to the wall since charged particles will move from the high to the low potentials. It was found that the variation of the breathing frequency plays a significant role on designated particle deposition region. At a short flow time, the particles only traveled and deposited on the upper part of the airway, whereas as the time flow increased the particles tended to increasingly accumulate on the lower parts of the airway. The electrostatic charge model for aerosol deposition has shown that the further design of aerosol transport must take an average breathing frequency into consideration. The wall shear stress, oscillatory flow velocity index, granular temperature, granular pressure and skin friction coefficient were able to imply the amount of solid particles deposited within the system. All the purposed indices can be used as preliminary indicators for indicating a potential deposition location of the aerosol.

Advanced testing method to evaluate the performance of respirator filter media

ABSTRACTFilter media for respirator applications are typically exposed to the cyclic flow condition, which is different from the constant flow condition adopted in filter testing standards. To understand the real performance of respirator filter media in the field it is required to investigate the penetration of particles through respirator filters under cyclic flow conditions representing breathing flow patterns of human beings. This article reports a new testing method for studying the individual effect of breathing frequency (BF) and peak inhalation flow rate (PIFR) on the particle penetration through respirator filter media. The new method includes the use of DMA (Differential Mobility Analyzer)-classified particles having the most penetrating particle size, MPPS (at the constant flowrate of equivalent mean inhalation flow rate, MIFR) as test aerosol. Two condensation particle counters (CPCs) are applied to measure the particle concentrations at the upstream and downstream of test filter media at the same time. Given the 10 Hz sampling time of CPCs, close-to-instantaneous particle penetration could be measured. A pilot study was performed to demonstrate the new testing method. It is found that the effect of BF on the particle penetration of test respirator filter media is of importance at all the tested peak inhalation flow rates (PIFRs), which is different from those reported in the previous work.

Regional Ventilation and Aerosol Deposition with Helium-Oxygen in Bronchoconstricted Asthmatic Lungs.

Theoretical models suggest that He-O2 as carrier gas may lead to more homogeneous ventilation and aerosol deposition than air. However, these effects have not been clinically consistent and it is unclear why subjects may or may not respond to the therapy. Here we present 3D-imaging data of aerosol deposition and ventilation distributions from subjects with asthma inhaling He-O2 as carrier gas. The data are compared with those that we previously obtained from a similar group of subjects inhaling air. Subjects with mild-to-moderate asthma were bronchoconstricted with methacholine and imaged with PET-CT while inhaling aerosol carried with He-O2. Mean-normalized-values of lobar specific ventilation sV* and deposition sD* were derived and the factors affecting the distribution of sD* were evaluated along with the effects of breathing frequency (f) and regional expansion (FVOL). Lobar distributions of sD* and sV* with He-O2 were not statistically different from those previously measured with air. However, with He-O2 there was a larger number of lobes having sV* and sD* closer to unity and, in those subjects with uneven deposition distributions, the correlation of sD* with sV* was on average higher (p < 0.05) in He-O2 (0.84 ± 0.8) compared with air (0.55 ± 0.28). In contrast with air, where the frequency of breathing during nebulization was associated with the degree of sD*-sV* correlation, with He-O2 there was no association. Also, the modulation of f on the correlation between FVOL and sD*/sV* in air, was not observed in He-O2. There were no differences in the inter-lobar heterogeneity of sD* or sV* in this group of mild asthmatic subjects breathing He-O2 compared with patients previously breathing air. Future studies, using these personalized 3D data sets as input to CFD models, are needed to understand if, and for whom, breathing He-O2 during aerosol inhalation may be beneficial.

Effects of breathing frequency on the heart rate deceleration capacity and heart rate acceleration capacity.

The deceleration capacity (DC) and acceleration capacity (AC) of heart rate as well as the respiratory rate predict outcome after acute myocardial infarction. We evaluated the relation between breathing frequency and both DC and AC, as well as the difference between them. We studied fourteen healthy young adults who breathed spontaneously and controlled their breathing to rates of 0.1, 0.2, 0.3, and 0.4Hz in a supine position. A 5-min R-R interval time series without movement artifacts or ectopic beats was obtained from each studied period and scanned to identify the anchor points that were characterized by a value longer or shorter than the preceding value. Averaged changes of R-R intervals surrounding the deceleration and acceleration anchors were calculated as DC and AC, respectively. The magnitudes of DC and AC increased progressively as breathing frequency decreased (Both p<0.001 by one-way repeated-measures analysis of variance). The magnitude of DC was larger than the magnitude of AC during 0.1-Hz breathing (95% confidence interval of their difference: 1.7-9.7ms), while the difference between them reduced to near zero at higher frequencies. Slow breathing enhances the magnitudes of DC and AC simultaneously under the conditions used in this study. The increase in the magnitude of DC is significantly greater than that of AC.

Effects of breathing frequency and flow rate on the total inward leakage of an elastomeric half-mask donned on an advanced manikin headform.

The objective of this study was to investigate the effects of breathing frequency and flow rate on the total inward leakage (TIL) of an elastomeric half-mask donned on an advanced manikin headform and challenged with combustion aerosols. An elastomeric half-mask respirator equipped with P100 filters was donned on an advanced manikin headform covered with life-like soft skin and challenged with aerosols originated by burning three materials: wood, paper, and plastic (polyethylene). TIL was determined as the ratio of aerosol concentrations inside (C in) and outside (C out) of the respirator (C in/C out) measured with a nanoparticle spectrometer operating in the particle size range of 20-200nm. The testing was performed under three cyclic breathing flows [mean inspiratory flow (MIF) of 30, 55, and 85 l/min] and five breathing frequencies (10, 15, 20, 25, and 30 breaths/min). A completely randomized factorial study design was chosen with four replicates for each combination of breathing flow rate and frequency. Particle size, MIF, and combustion material had significant (P < 0.001) effects on TIL regardless of breathing frequency. Increasing breathing flow decreased TIL. Testing with plastic aerosol produced higher mean TIL values than wood and paper aerosols. The effect of the breathing frequency was complex. When analyzed using all combustion aerosols and MIFs (pooled data), breathing frequency did not significantly (P = 0.08) affect TIL. However, once the data were stratified according to combustion aerosol and MIF, the effect of breathing frequency became significant (P < 0.05) for all MIFs challenged with wood and paper combustion aerosols, and for MIF = 30 l/min only when challenged with plastic combustion aerosol. The effect of breathing frequency on TIL is less significant than the effects of combustion aerosol and breathing flow rate for the tested elastomeric half-mask respirator. The greatest TIL occurred when challenged with plastic aerosol at 30 l/min and at a breathing frequency of 30 breaths/min.

Effect of Particle Size on the Performance of an N95 Filtering Facepiece Respirator and a Surgical Mask at Various Breathing Conditions.

The effect of aerosol particle size on the performance of an N95 filtering facepiece respirator (FFR) and a surgical mask (SM) was evaluated under different breathing conditions, including breathing frequency and mean inspiratory flow (MIF) rate. The FFR and SM were sealed on a manikin headform and challenged with charge-equilibrated NaCl aerosol. Filter penetration (Pfilter) was determined as the ratio of aerosol concentrations inside and outside the FFR/SM size-selectively (28 channels) within a range of 20 to 500 nm. In addition, the same models of the FFR and SM were donned, but not sealed, on an advanced manikin headform covered with skin-like material. Total inward leakage (TIL), which represents the total particle penetration, was measured under conditions identical to the filter penetration experiment. Testing was conducted at four mean MIFs (15, 30, 55 and 85 L/min) combined with five breathing frequencies (10, 15, 20, 25 and 30 breaths/min). The results show that SM produced much higher Pfilter and TIL values, and thus provide little protection against aerosols in the size range tested. Pfilter was significantly affected by particle size and breathing flow rate (p <0.05) for the tested FFR and SM. Surprisingly, for both devices, Pfilter as a function of the particle size exhibited more than one peak under all tested breathing conditions. The effect of breathing frequency on Pfilter was generally less pronounced, especially for lower MIFs. For the FFR and SM, TIL increased with increasing particle size up to about 50 nm; for particles above 50 nm, the total penetration was not significantly affected by particle size and breathing frequency; however, the effect of MIF remained significant.

Effects of breathing frequency on baroreflex effectiveness index and spontaneous baroreflex sensitivity derived by sequence analysis

High-frequency paced breathing is required to avoid overestimation when measuring spectral baroreflex sensitivity (BRSLF) to predict outcomes in cardiovascular patients. We examined whether respiration should also be controlled when measuring the baroreflex effectiveness index (BEI) and baroreflex sensitivity (BRSseq), which are derived by sequence analysis. We studied 17 healthy young adults who breathed spontaneously and controlled their breathing to rates of 0.1, 0.2, 0.3 and 0.4 Hz in the supine position. We found respiratory influences on BEI and BRSseq depended on the lag used to pair the systolic arterial pressure and R-R interval in a sequence. Therefore, the two baroreflex measures were obtained by selecting the lag with a larger number of sequences for each section. BEI decreased progressively as the breathing frequency increased. BRSseq remained unchanged at rates of 0.1, 0.2 and 0.3 Hz, but was reduced during 0.4 Hz breathing. In contrast, BRSLF was constant during 0.2, 0.3, and 0.4 Hz breathing, but was greater at 0.1 Hz. Rates of spontaneous breathing range from 0.1 to 0.32 Hz with a mean value of 0.19 Hz. Baroreflex measures obtained for spontaneous breathing were found to be between the values for 0.1 and 0.3 Hz paced breathing. BEI and BRSseq do not remain constant at various breathing frequencies. Nonetheless, considering the pattern of change and the frequency range of spontaneous respiration, the authors suggest that high-frequency paced breathing is not necessary when measuring the BEI and BRSseq under the conditions used in this study.

Effect of breathing frequency and airflow on pulmonary function in high-intensity equine exercise.

It has been postulated that the hypoxaemia and hypercapnoea that characterize strenuous equine exercise are partly due to flow limitations imposed by high breathing frequencies (fb), and that gas exchange would be improved if fb could be lowered. To evaluate this possibility, 6 Thoroughbred horses underwent 4 incremental treadmill exercise tests at inclines of 0, 5, 10 and 25%, respectively. In the test, horses were given a warm-up for 2 min, then ran sequentially for 1 min each at 60, 100 and 115% VO2max. Oxygen consumption (VO2), blood gas tensions (PaO2, PaCO2), fb, tidal volume (VT), minute ventilation (Ve), transpulmonary pressure (Ptp), peak inspiratory and expiratory airflows (VI, VE) and work of breathing (Wrm) were determined during the last 15 s of exercise at each intensity. The only effect of fb on PaO2 was seen at 60% VO2max. Also, maximal transpulmonary pressure difference (delta Ptpmax), and peak VI, and VE on a 25% slope were lower than those recorded at the other 3 inclines at 60% VO2max. At 100 and 115% VO2max, the effect of fb was less clear. While fb still differed, the only effects of fb at 100% VO2max were on delta Ptpmax. At 115% VO2max, fb on a 25% incline was lower than that for 0 and 5% slopes. The only other difference noted at this intensity was in VT on 10% slope. However, there was no difference between VTS recorded at inclines of 0, 5 or 25% at 115% VO2max. There was no effect of fb or exercise intensity on Ve at 100 or 115% VO2max. There was no change in PaO2, fb, VT, delta Ptpmax or VI and VE as exercise intensity increased from 60-115% VO2max on slopes of 0, 5 or 10%. However, for exercise on the 25% incline (i.e. with lower fb), each of these parameters increased (or decreased for PaO2) from 60-100%, but not from 100-115% VO2max. Failure of peak airflow and VT to increase when intensity increased was associated with the development of hypoxaemia and hypercapnoea, regardless of slope or fb. It is concluded that while a low fb may have some beneficial effect on gas exchange during submaximal exercise at approximately 60% VO2max, this effect disappears as exercise intensity increases. There appear to be limits to the peak airflows that can be generated by horses during strenuous exercise, and these limits may be reached regardless of fb. Flow limitation per se may play a greater role in the development of exercise-induced hypoxaemia and hypercapnoea in horses than dose fb.

The Effect of Breathing Frequency on Inspiratory Muscle Endurance During Incremental Threshold Loading

We tested whether there were differences in measures of respiratory muscle endurance between tests with spontaneously chosen breathing patterns and tests with fixed breathing rates in normal volunteers. Measures of respiratory muscle endurance-maximum load tolerated, mean mouth pressure at maximum load and peak pressure at maximum load were reproducible over three tests with the spontaneously chosen breathing pattern. There was no difference in these measurements between the three tests with fixed breathing frequency. There was no difference in tidal volume, inspiratory time, and the ratio of inspiratory time to total breath duration between the tests in which breathing pattern was spontaneously chosen; there was a difference in these measurements between the tests with a fixed breathing frequency. We conclude that regulation of breathing frequency is unnecessary in the two-minute threshold loading test to obtain reproducible results for measures of respiratory muscle endurance.