Nasal airflow in inspiration and expiration

AbstractInspiratory and expiratory airflow rates were measured in 30 subjects during quiet respiration (at a pressure gradient of 150 Pa) and at peak flow rates.For low flow rates airflow rate was greater for inspiration than for expiration. Conversely at peak flow rates flow was greatest during expiration. Thus there was a reversal in the phase relationship between inspiration and expiration as flow rate increased.It was also found that peak inspiratory flow rate correlated better with values for nasal resistance than did peak expiratory flow rate. Flow rate measured by rhinomanometry during quiet respiration was more sensitive to physiologically induced changes in nasal resistance than was peak flow rate.The findings are discussed with reference to previous work on the physiology of nasal airflow.

Download Full-text

V. FORCED FLOW RATES

PEDIATRICS ◽

10.1542/peds.35.1.200 ◽

1965 ◽

Vol 35 (1) ◽

pp. 200-210

Author(s):

George R. DeMuth ◽

William F. Howatt ◽

Bruce Hill

Keyword(s):

Flow Rate ◽

Vital Capacity ◽

Peak Flow ◽

Normal Subjects ◽

Forced Flow ◽

Forced Expiration ◽

Flow Rates ◽

Multiple Units ◽

Airway Conductance ◽

Peak Inspiratory Flow Rate

1. Data from normal subjects on the peak expiratory flow rate, the peak inspiratory flow rate, and the flow rate at the point where half the vital capacity has been expired (E50), have been obtained as part of a longitudinal study of the growth of lung function in school children. 2. The peak flow rates grow in a manner similar to that of the lung volumes. 3. The E50, in contradistinction, grows in a manner similar to airway conductance (the reciprocal of airway resistance). 4. Longitudinal studies of the peak flow rates indicate that individuals tend to maintain their positions in relation to the group. 5. A theoretical postulation of the forced flow-volume relationship has been suggested. According to this postulation the lungs of the normal subject empty as a unit or nearly so. The flow (after the initial acceleration) at any point in time is dependent on his vital capacity and an emptying factor. This emptying factor decreases somewhat with increasing body size. This is more evident in the girls. 6. In the patient with airway obstructive disease (as asthma) the lung can be thought of as composed of multiple units in parallel with varying amounts of reduction in their emptying factor. 7. The theoretical advantages of clinical tests based upon flow in the mid or later portions of the forced expiration have been given.

Download Full-text

Assessment of the Use of Humidified Nasal Cannulas for Oxygen Therapy in Patients with Epistaxis

ORL ◽

10.1159/000514460 ◽

2021 ◽

pp. 1-5

Author(s):

Jingjing Liu ◽

Tengfang Chen ◽

Zhenggang Lv ◽

Dezhong Wu

Keyword(s):

Flow Rate ◽

Oxygen Therapy ◽

Preliminary Investigation ◽

Nasal Cannula ◽

Low Flow ◽

Antiplatelet Drugs ◽

Flow Rates ◽

The Past ◽

Oxygen Inhalation ◽

Significant Difference

Introduction: In China, nasal cannula oxygen therapy is typically humidified. However, it is difficult to decide whether to suspend nasal cannula oxygen inhalation after the nosebleed has temporarily stopped. Therefore, we conducted a preliminary investigation on whether the use of humidified nasal cannulas in our hospital increases the incidence of epistaxis. Methods: We conducted a survey of 176,058 inpatients in our hospital and other city branches of our hospital over the past 3 years and obtained information concerning their use of humidified nasal cannulas for oxygen inhalation, nonhumidified nasal cannulas, anticoagulant and antiplatelet drugs, and oxygen inhalation flow rates. This information was compared with the data collected at consultation for epistaxis during these 3 years. Results: No significant difference was found between inpatients with humidified nasal cannulas and those without nasal cannula oxygen therapy in the incidence of consultations due to epistaxis (χ2 = 1.007, p > 0.05). The same trend was observed among hospitalized patients using anticoagulant and antiplatelet drugs (χ2 = 2.082, p > 0.05). Among the patients with an inhaled oxygen flow rate ≥5 L/min, the incidence of ear-nose-throat (ENT) consultations due to epistaxis was 0. No statistically significant difference was found between inpatients with a humidified oxygen inhalation flow rate <5 L/min and those without nasal cannula oxygen therapy in the incidence of ENT consultations due to epistaxis (χ2 = 0.838, p > 0.05). A statistically significant difference was observed in the incidence of ENT consultations due to epistaxis between the low-flow nonhumidified nasal cannula and nonnasal cannula oxygen inhalation groups (χ2 = 18.428, p < 0.001). The same trend was observed between the 2 groups of low-flow humidified and low-flow nonhumidified nasal cannula oxygen inhalation (χ2 = 26.194, p < 0.001). Discussion/Conclusion: Neither high-flow humidified nasal cannula oxygen inhalation nor low-flow humidified nasal cannula oxygen inhalation will increase the incidence of recurrent or serious epistaxis complications; the same trend was observed for patients who use anticoagulant and antiplatelet drugs. Humidification during low-flow nasal cannula oxygen inhalation can prevent severe and repeated epistaxis to a certain extent.

Download Full-text

Experimental Investigation of Pressure Fluctuations on Inner Wall of a Centrifugal Pump

International Journal of Turbo and Jet Engines ◽

10.1515/tjj-2016-0078 ◽

2019 ◽

Vol 36 (4) ◽

pp. 401-410 ◽

Cited By ~ 2

Author(s):

Xiao-Qi Jia ◽

Bao-Ling Cui ◽

Zu-Chao Zhu ◽

Yu-Liang Zhang

Keyword(s):

Centrifugal Pump ◽

Flow Rate ◽

Pressure Fluctuation ◽

Pressure Fluctuations ◽

High Flow ◽

Low Flow ◽

Centrifugal Pumps ◽

Flow Rates ◽

Pressure Distributions ◽

Blade Passing Frequency

Abstract Affected by rotor–stator interaction and unstable inner flow, asymmetric pressure distributions and pressure fluctuations cannot be avoided in centrifugal pumps. To study the pressure distributions on volute and front casing walls, dynamic pressure tests are carried out on a centrifugal pump. Frequency spectrum analysis of pressure fluctuation is presented based on Fast Fourier transform and steady pressure distribution is obtained based on time-average method. The results show that amplitudes of pressure fluctuation and blade-passing frequency are sensitive to the flow rate. At low flow rates, high-pressure region and large pressure gradients near the volute tongue are observed, and the main factors contributing to the pressure fluctuation are fluctuations in blade-passing frequency and high-frequency fluctuations. By contrast, at high flow rates, fluctuations of rotating-frequency and low frequencies are the main contributors to pressure fluctuation. Moreover, at low flow rates, pressure near volute tongue increases rapidly at first and thereafter increases slowly, whereas at high flow rates, pressure decreases sharply. Asymmetries are observed in the pressure distributions on both volute and front casing walls. With increasing of flow rate, both asymmetries in the pressure distributions and magnitude of the pressure decrease.

Download Full-text

Effects of short blades on performance and inner flow characteristics of a low-specific-speed centrifugal pump

Proceedings of the Institution of Mechanical Engineers Part A Journal of Power and Energy ◽

10.1177/0957650917695672 ◽

2017 ◽

Vol 231 (4) ◽

pp. 290-302 ◽

Cited By ~ 4

Author(s):

Can Kang ◽

Ning Mao ◽

Chen Pan ◽

Yang Zhu ◽

Bing Li

Keyword(s):

Centrifugal Pump ◽

Flow Rate ◽

Pressure Fluctuations ◽

Flow Characteristics ◽

Low Flow ◽

Back Surface ◽

Flow Rates ◽

Pump Operation ◽

Low Specific Speed ◽

Specific Speed

A low-specific-speed centrifugal pump equipped with long and short blades is studied. Emphasis is placed on the pump performance and inner flow characteristics at low flow rates. Each short blade is intentionally shifted towards the back surface of the neighboring long blade, and the outlet parts of the short blades are uniformly shortened. Unsteady numerical simulation is conducted to disclose inner flow patterns associated with the modified design. Thereby, a comparison is enabled between the two schemes featured by different short blades. Both practical operation data and numerical results support that the deviation and cutting of the short blades can eliminate the positive slope of pump head curve at low flow rates. Therefore, the modification of short blades improves the pump operation stability. Due to the shortening of the outlet parts of the short blades, velocity distributions between impeller outlet and radial diffuser inlet exhibit explicitly altered circumferential flow periodicity. Pressure fluctuations in the radial diffuser are complex in terms of diversified periodicity and amplitudes. Flow rate influences pressure fluctuations in the radial diffuser considerably. As flow rate decreases, the regularity of the orbit of hydraulic loads exerted upon the impeller collapses while hydraulic loads exerted upon the short blades remain circumferentially periodic.

Download Full-text

Cerebral Hyperperfusion Syndrome by the Numbers: Transient Focal Neurological Deficit, Imaging-Proven Focal Hyperperfusion, and High Graft Flow Rate Following Superficial Temporal Artery-Middle Cerebral Artery bypass in a Patient With Symptomatic Carotid Occlusion—Case Report

Operative Neurosurgery ◽

10.1093/ons/opy010 ◽

2018 ◽

Vol 15 (6) ◽

pp. E94-E99 ◽

Cited By ~ 3

Author(s):

Ralph Rahme ◽

Tejaswi D Sudhakar ◽

Marjan Alimi ◽

Timothy G White ◽

Rafael A Ortiz ◽

...

Keyword(s):

Middle Cerebral Artery ◽

Flow Rate ◽

Perfusion Imaging ◽

Superficial Temporal Artery ◽

Temporal Artery ◽

Low Flow ◽

Flow Rates ◽

Cerebral Hyperperfusion Syndrome ◽

Cerebral Hyperperfusion ◽

Graft Flow

Abstract BACKGROUND AND IMPORTANCE Cerebral hyperperfusion syndrome (CHS) is a well-known complication of superficial temporal artery (STA) to middle cerebral artery (MCA) bypass for ischemic cerebrovascular disease. While this argues against “low flow” in the bypass construct, flow rates in the graft have not been previously quantified in the setting of CHS. CLINICAL PRESENTATION A 58-yr-old man presented with recurrent left hemispheric ischemic strokes and fluctuating right hemiparesis and aphasia. Vascular imaging revealed left cervical internal carotid artery occlusion and perfusion imaging confirmed left hemispheric hypoperfusion. After failing to respond to maximal medical therapy, the patient underwent single-barrel STA-MCA bypass. Postoperatively, his symptoms resolved and blood pressure (BP) was strictly controlled within normal range. However, 2 d later, he developed severe expressive aphasia. CTA demonstrated a patent bypass graft and SPECT showed focal hyperperfusion in Broca's speech area. Seizure activity was ruled out. A high graft flow rate of 52 mL/min was documented by quantitative magnetic resonance angiography (MRA). Thus, the diagnosis of CHS was made and managed with strict BP control. The patient exhibited complete recovery of speech over a period of days and was discharged home. Repeat SPECT at 4 mo showed resolution of hyperperfusion and quantitative MRA demonstrated reduction of graft flow rate to 34 mL/min. CONCLUSION This is the first case of perfusion imaging-proven CHS after STA-MCA bypass, where high graft flow rates are objectively documented. Our observations constitute irrefutable evidence challenging the classic belief that the STA-MCA bypass is a low-flow construct.

Download Full-text

Direct metabolic effects of isoproterenol and propranolol in ischemic myocardium of the dog

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1980.239.4.h469 ◽

1980 ◽

Vol 239 (4) ◽

pp. H469-H469

Author(s):

Michael Goodlett ◽

Kyran Dowling ◽

Lynne J. Eddy ◽

James M. Downey

Keyword(s):

High Energy ◽

Ischemic Myocardium ◽

The Other ◽

Energy Utilization ◽

Metabolic Effects ◽

Low Flow ◽

High Energy Phosphate ◽

Drug Induced ◽

Flow Rates ◽

Induced Changes

The effect of either isoproterenol or propranolol on the metabolism of ischemic myocardium was examined. To ensure that all changes were due to changes in metabolism and not drug-induced changes in residual flow to the ischemic regions, we devised a preparation in which two coronary branches on the same heart were simultaneously perfused at a low flow rate. Microsphere measurements verified that the two ischemic regions were receiving identical blood flow rates. One branch received an infusion of 0.9% NaCl and the other received the drug. After 1 h both regions were biopsied and the high-energy phosphate levels in each region were determined. ATP and phosphocreatine each fell to about 50% of their starting values in the 0.9% NaCl-treated regions, and isoproterenol did not further depress the high-energy phosphate concentrations. Propranolol, on the other hand, significantly preserved the high-energy phosphate concentrations. We conclude that although isoproterenol seemed incapable of accelerating energy utilization in ischemic myocardium, propranolol is apparently capable of reducing it.

Download Full-text

Interaction between CO2 concentration and flow rate on peripheral airway resistance

Journal of Applied Physiology ◽

10.1152/jappl.1991.70.6.2514 ◽

1991 ◽

Vol 70 (6) ◽

pp. 2514-2521 ◽

Cited By ~ 3

Author(s):

A. Kaise ◽

A. N. Freed ◽

W. Mitzner

Keyword(s):

Flow Rate ◽

Airway Resistance ◽

Co2 Concentration ◽

Low Flow ◽

Flow Rates ◽

Peripheral Airway ◽

Residual Capacity ◽

Local Ventilation ◽

End Tidal ◽

The Relationship

In the present study, we investigated the interaction between CO2 concentration and rate of delivered flow on peripheral airway resistance (Rp) in the intact canine lung. Dogs were anesthetized, intubated, paralyzed, and mechanically ventilated with room air to maintain end-tidal CO2 between 4.8 and 5.2%. Using a wedged bronchoscope technique, we measured Rp at functional residual capacity. The relationship between CO2 concentration and Rp was measured at flow rates of 100 and 400 ml/min with 5, 3, 2, 1, and 0% CO2 in air. Measurements were made at the end of a 3-min exposure to each gas. At low flow rates (100 ml/min) responses to hypocapnia were small, whereas at high flow rates (400 ml/min) responses were large. The PC50 (defined as the CO2 concentration required to produce a 50% increase in Rp above baseline Rp established on 5% CO2) at 400 ml/min (1.73%) was significantly larger than that at 100 ml/min (0.38%). We also directly measured the relationship between Rp and flow rate with 5% CO2 (normocapnia) or 1% CO2 (hypocapnia) delivered into the wedged segment. Increases in normocapnic flow caused small but significant decreases in Rp. In contrast, increases in hypocapnic flow from 100 to 400 ml/min caused a 108% increase in Rp. Thus the response to hypocapnia is augmented by increasing flow rate. This interaction can be explained by a simple model that considers the effect of local ventilation-perfusion ratio and gas mixing on the local CO2 concentration at the site of peripheral airway contraction.

Download Full-text

Turbulence Measurements in a Centrifugal Pump With a Synchronously Orbiting Impeller

Volume 1: Turbomachinery ◽

10.1115/91-gt-070 ◽

1991 ◽

Author(s):

Ronald D. Flack ◽

Steven M. Miner ◽

Ronald J. Beaudoin

Keyword(s):

Centrifugal Pump ◽

Reynolds Stress ◽

Flow Rate ◽

Cross Product ◽

Design Flow ◽

Low Flow ◽

Rate Variation ◽

Flow Rates ◽

The Individual ◽

Design Flow Rate

Turbulence profiles were measured in a centrifugal pump with an impeller with backswept blades using a two directional laser velocimeter. Data presented includes radial, tangential, and cross product Reynolds stresses. Blade to blade profiles were measured at four circumferential positions and four radii within and one radius outside the four bladed impeller. The pump was tested in two configurations; with the impeller running centered within the volute, and with the impeller orbiting with a synchronous motion (ε/r2 = 0.016). Flow rates ranged from 40% to 106% of the design flow rate. Variation in profiles among the individual passages in the orbiting impeller were found. For several regions the turbulence was isotropic so that the cross product Reynolds stress was low. At low flow rates the highest cross product Reynolds stress was near the exit. At near design conditions the lowest cross product stress was near the exit, where uniform flow was also observed. Also, near the exit of the impeller the highest turbulence levels were seen near the tongue. For the design flow rate, inlet turbulence intensities were typically 9% and exit turbulence intensities were 6%. For 40% flow capacity the values increased to 18% and 19%, respectively. Large local turbulence intensities correlated with separated regions. The synchronous orbit did not increase the random turbulence, but did affect the turbulence in the individual channels in a systematic pattern.

Download Full-text

Suppression of Self-Excited Flow Instability in a Radial Diffuser Using Rough Surfaces

Volume 2: Fora ◽

10.1115/fedsm2006-98261 ◽

2006 ◽

Author(s):

Saad A. Ahemd ◽

Hayder Salem

Keyword(s):

Flow Rate ◽

Smooth Surface ◽

Flow Instability ◽

Rough Surfaces ◽

Flow Coefficient ◽

Flow Instabilities ◽

Low Flow ◽

Flow Rates ◽

Flow Limit ◽

Stable Operating

Flow instabilities in a compression system at low flow rates set the flow limit of the stable operating range. Experiments to investigate the feasibility of controlling the stall in the radial diffuser of a low speed centrifugal compressor were carried out. The technique was very simple and involved using rough surfaces (i.e., sand papers) attached to the diffuser shroud. The results showed that the flow instability in the diffuser (stall) was delayed to a lower flow coefficient (the mass flow rate could be reduced to 70% of its value with the smooth surface) when the rough surfaces were positioned on the diffuser shroud.

Download Full-text