Flow Resistance in Tracheotomy Tubes

1973 ◽  
Vol 82 (6) ◽  
pp. 827-830 ◽  
Author(s):  
John Cavo ◽  
Joseph H. Ogura ◽  
Donald G. Sessions ◽  
J. Roger Nelson
Keyword(s):  
Laminar Flow ◽  
Respiratory System ◽  
Flow Resistance ◽  
Airway Resistance ◽  
Upper Airway ◽  
Plastic Tube ◽  
Flow Rates ◽  
Pressure Drops ◽  
Adult Human

The role of the upper airway (the breathing passage above the trachea) in maintaining the normal junction of the respiratory system has been suggested by previous investigators. During a tracheotomy the upper airway is by-passed by a prosthetic metal or plastic tube which is placed into the trachea through the neck. In order to determine which, among the most commonly used tracheotomy tubes, most closely simulate the flow resistance of the adult human upper airway, a series of varying flow rates were passed through different sized tubes. Pressure drops were recorded and resistance values were thereby determined. Our data was compared with previously determined values for flow resistance of the adult human upper airway. Resistance related to turbulent and laminar flow was considered. On the basis of our data we have suggested that large caliber tracheotomy tubes be used in adult patients in whom the prolonged need for a tracheotomy is anticipated.

scholarly journals Flow resistance along the rat renal tubule

2018 ◽  
Vol 315 (5) ◽  
pp. F1398-F1405 ◽  
Author(s):  
Gabrielle G. Gilmer ◽  
Venkatesh G. Deshpande ◽  
Chung-Lin Chou ◽  
Mark Knepper
Keyword(s):  
Pressure Drop ◽  
Laminar Flow ◽  
Flow Resistance ◽  
Renal Tubule ◽  
Collecting Duct ◽  
Maximum Pressure ◽  
Luminal Diameter ◽  
Flow Rates ◽  
Axial Pressure Gradient ◽  
Collecting Ducts

The Reynolds number in the renal tubule is extremely low, consistent with laminar flow. Consequently, luminal flow can be described by the Hagen-Poiseuille laminar flow equation. This equation calculates the volumetric flow rate from the axial pressure gradient and flow resistance, which is dependent on the length and diameter of each renal tubule segment. Our goal was to calculate the pressure drop along each segment of the renal tubule and to determine the points of highest resistance. When the Hagen-Poiseuille equation was used for rat superficial nephrons based on known tubule flow rates, lengths, and diameters, it was found that the maximum pressure drop occurred in two segments: the thin descending limbs of Henle and the inner medullary collecting ducts. The high resistance in the thin descending limbs is due to their small diameters. The steep pressure drop observed in the inner medullary collecting ducts is due to the convergent structure of the tubules, which channels flow into fewer and fewer tubules toward the papillary tip. For short-looped nephrons, the calculated glomerular capsular pressure matched measured values, even with the high collecting duct flow rates seen in water diuresis, provided that tubule compliance was taken into account. In long-looped nephrons, the greater length of thin limb segments is likely compensated for by a larger luminal diameter. Simulation of the effect of proximal diuretics, namely acetazolamide or type 2 sodium-glucose transporter inhibitors, predicts a substantial back pressure in Bowman’s capsule, which may contribute to observed decreases in glomerular filtration rate.

Extrathoracic airway resistance in man

1961 ◽  
Vol 16 (2) ◽  
pp. 326-330 ◽  
Author(s):  
Robert E. Hyatt ◽  
Roger E. Wilcox
Keyword(s):  
Flow Resistance ◽  
Airway Resistance ◽  
Human Subjects ◽  
Upper Airway ◽  
Normal Subjects ◽  
Mouth Breathing ◽  
Human Beings ◽  
Lung Inflation ◽  
Upper Airway Resistance ◽  
Extrathoracic Airway

Simultaneous extrathoracic and intrathoracic flow resistance was measured in 19 unanesthetized subjects during mouth breathing. Lateral intratracheal pressure was recorded from a needle introduced 2 cm below the larynx. The intratracheal-oral pressure gradient was recorded during various respiratory maneuvers. The pressure drop from esophagus to trachea was also recorded. The extrathoracic pressure-flow relationships were alinear. Large inter- and intrasubject variability in upper airway resistance was encountered. Some factors contributing to this variability were defined. The upper airway accounted for approximately 45% of the total airway resistance in nine normal and 20% in 10 emphysematous human subjects. Upper airway resistance decreased with increasing lung inflation in four normal subjects. The magnitude and potential variability of the upper airway resistance must be considered in evaluating maneuvers designed to alter intrathoracic flow resistance, especially in normal human beings. It appears that during mouth breathing the major component of the upper airway resistance is located in the larynx. Submitted on September 14, 1960

Partitioning of respiratory flow resistance in man

1964 ◽  
Vol 19 (4) ◽  
pp. 653-658 ◽  
Author(s):  
B. G. Ferris ◽  
J. Mead ◽  
L. H. Opie
Keyword(s):  
Chest Wall ◽  
Flow Resistance ◽  
Airway Resistance ◽  
Upper Airway ◽  
Mouth Breathing ◽  
Lower Airway ◽  
Nasal Breathing ◽  
Pulmonary Tissue ◽  
Tissue Resistance ◽  
Highly Nonlinear

Measurements of flow resistance of various components of the respiratory system were measured in adult male subjects in the sitting position. Nasal resistance is the largest single component being nearly one-half the total and two-thirds of the airway resistance during nose breathing. It is highly nonlinear, and shows much variability. During mouth breathing upper airway resistance (mouth, pharynx, glottis, larynx and upper trachea) is also markedly nonlinear, and accounts for one-third the total airway resistance. Lower airway resistance is approximately linear up to flows of 2 liters/sec. Pulmonary tissue resistance is low as reported in this study. Chest wall resistance is nearly linear up to flow rates of 2 liters/sec and accounts for slightly less than half the total respiratory resistance during mouth breathing and 10–19% during nasal breathing. larynx; airways; chest wall; nose Submitted on December 16, 1963

The vulnerable small airway

PEDIATRICS ◽  
1977 ◽  
Vol 59 (5) ◽  
pp. 783-785
Author(s):  
V. Chernick
Keyword(s):  
Flow Resistance ◽  
Gas Flow ◽  
Airway Resistance ◽  
Clear Understanding ◽  
Small Airways ◽  
Peripheral Airways ◽  
Pulmonary Flow ◽  
Peripheral Airway ◽  
First Time

Fundamental physiological work in the late 1960s provided for the first time a clear understanding of (1) the role of the small airways (< 2 mm in diameter) in determining overall airway resistance to gas flow and (2) the relationship between central and peripheral airway resistance and lung growth.1,2 Involvement of the small airways early in the course of cystic fibrosis has been previously commented upon and documented in Pediatrics.3-5 After the age of about 5 years, the flow resistance of peripheral airways constitutes only about 10% to 20% of total pulmonary flow resistance,2 a fraction so small that conventional measurement of total resistance cannot detect small changes in the peripheral component.

Head position modifies upper airway resistance in men

1988 ◽  
Vol 64 (3) ◽  
pp. 1285-1288 ◽  
Author(s):  
G. Liistro ◽  
D. Stanescu ◽  
G. Dooms ◽  
D. Rodenstein ◽  
C. Veriter
Keyword(s):  
Magnetic Resonance ◽  
Respiratory System ◽  
Airway Resistance ◽  
Upper Airway ◽  
Magnetic Resonance Images ◽  
Head Position ◽  
Upper Airways ◽  
Total Head ◽  
Head Flexion ◽  
Head Positions

We measured in healthy volunteers airway resistance (R(aw)), resistance of the respiratory system (Rrs), and supralaryngeal resistance (Rsl) in the following head positions: neutral, extended, and partially and fully flexed. Sagittal magnetic resonance images of the upper airways were recorded in neutral and flexed head positions. We observed significant increases in Raw (P less than 0.01), Rrs (P less than 0.001), and Rsl (P less than 0.001) in the flexed position, with respect to the neutral one, and corresponding decreases of specific airway and specific respiratory conductances. Resistances decreased (although not significantly) when the subjects' heads were extended. A decrease in both diameter and surface area of the hypopharyngeal airways (as shown by magnetic resonance images) with total head flexion was accompanied by significant increases in all measured resistances. Changes in the caliber of hypopharynx appear to be responsible for the increase in resistance during head flexion.

Effect of negative expiratory pressure on respiratory system flow resistance in awake snorers and nonsnorers

1999 ◽  
Vol 87 (3) ◽  
pp. 969-976 ◽  
Author(s):  
Claudio Tantucci ◽  
Alexandre Duguet ◽  
Anna Ferretti ◽  
Selma Mehiri ◽  
Isabelle Arnulf ◽  
...  
Keyword(s):  
Respiratory System ◽  
Supine Position ◽  
Flow Resistance ◽  
Upper Airway ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Upper Airways ◽  
Flow Interruption ◽  
Expiratory Flow ◽  
Spontaneously Breathing

In spontaneously breathing subjects, intrathoracic expiratory flow limitation can be detected by applying a negative expiratory pressure (NEP) at the mouth during tidal expiration. To assess whether NEP might increase upper airway resistance per se, the interrupter resistance of the respiratory system (Rint,rs) was computed with and without NEP by using the flow interruption technique in 12 awake healthy subjects, 6 nonsnorers (NS), and 6 nonapneic snorers (S). Expiratory flow (V˙) and Rint,rs were measured under control conditions with V˙ increased voluntarily and during random application of brief (0.2-s) NEP pulses from −1 to −7 cmH2O, in both the seated and supine position. In NS, Rint,rs with spontaneous increase inV˙ and with NEP was similar [3.10 ± 0.19 and 3.30 ± 0.18 cmH2O ⋅ l−1 ⋅ s at spontaneous V˙ of 1.0 ± 0.01 l/s and atV˙ of 1.1 ± 0.07 l/s with NEP (−5 cmH2O), respectively]. In S, a marked increase in Rint,rs was found at all levels of NEP ( P < 0.05). Rint,rs was 3.50 ± 0.44 and 8.97 ± 3.16 cmH2O ⋅ l−1 ⋅ s at spontaneous V˙ of 0.81 ± 0.02 l/s and atV˙ of 0.80 ± 0.17 l/s with NEP (−5 cmH2O), respectively ( P < 0.05). With NEP, Rint,rs was markedly higher in S than in NS both seated ( F = 8.77; P < 0.01) and supine ( F = 9.43; P < 0.01). In S,V˙ increased much less with NEP than in NS and was sometimes lower than without NEP, especially in the supine position. This study indicates that during wakefulness nonapneic S have more collapsible upper airways than do NS, as reflected by the marked increase in Rint,rs with NEP. The latter leads occasionally to an actual decrease in V˙ such as to invalidate the NEP method for detection of intrathoracic expiratory flow limitation.

Upper airway afferents are sufficient to evoke the early components of respiratory-related cortical potentials in humans

2004 ◽  
Vol 97 (5) ◽  
pp. 1874-1879 ◽  
Author(s):  
Christine Donzel-Raynaud ◽  
Christian Straus ◽  
Michela Bezzi ◽  
Stefania Redolfi ◽  
Mathieu Raux ◽  
...  
Keyword(s):  
Evoked Potentials ◽  
Cognitive Processing ◽  
Respiratory System ◽  
Somatosensory Evoked Potentials ◽  
Upper Airway ◽  
Cortical Activity ◽  
Stimulus Detection ◽  
Evoked Cortical Potentials ◽  
Cortical Potentials

Repeated inspiratory occlusions in humans elicit respiratory-related cortical potentials, the respiratory counterpart of somatosensory-evoked potentials. These potentials comprise early components (stimulus detection) and late components (cognitive processing). They are considered as the summation of several afferent activities from various part of the respiratory system. This study assesses the role of the upper airway as a determinant of the early and late components of the potentials, taking advantage of the presence of a tracheotomy in patients totally or partially deafferented. Eight patients who could breathe either through the mouth or through a tracheotomy orifice (whole upper airway bypassed) were studied (4 quadriplegic patients with phrenic pacing, 4 patients with various sources of inspiratory pump dysfunction). Respiratory-related evoked potentials were recorded in CZ-C3 and CZ-C4. They were consistently present after mouth occlusions, with a first positive P1 and a first negative N1 components of normal latencies (P1: 40.4 ± 6.1 ms in CZ-C3 and 47.6 ± 7.6 ms in CZ-C4; N1: 84.4 ± 27.1 ms in CZ-C3 and 90.2 ± 17.4 ms in CZ-C4) and amplitudes. Tracheal occlusions did not evoke any cortical activity. Therefore, in patients with inspiratory pump dysfunction, the activation of upper airway afferents is sufficient to produce the early components of the respiratory-related evoked cortical potentials. Per contra, in this setting, pulmonary afferents do not suffice to evoke these components.

Oxygen Transport in Salmon Spawning Gravels

1980 ◽  
Vol 37 (2) ◽  
pp. 155-162 ◽  
Author(s):  
R. A. Johnson
Keyword(s):  
Oxygen Transport ◽  
Flow Resistance ◽  
Head Loss ◽  
Flow Through Porous Media ◽  
Air Entrapment ◽  
Flow Rates ◽  
Pressure Drops ◽  
Salmon Eggs ◽  
Flow Through ◽  
Media Data

The importance of understanding transport characteristics of flow through gravel media is discussed from the viewpoint of salmonid enhancement programs. A summary of the important features of the incubation process with respect to mass transport is provided along with applicable theories describing flow through porous media. Data obtained from experiments described herein are used to assess the accuracy of existing correlations for predicting pressure drops across gravel substrates. It is found that available hydraulic relations can be used to predict flow velocity magnitudes in gravel media with an accuracy of ± 50% over a twofold range of flow rates, providing one measurement of head loss is available at one flow rate. An adaptation of the Carman–Kozeny equation is found to be suitable for calculating the influence of fines on permeability. The importance of air entrapment on flow resistance is confirmed experimentally and modeled using available correlations. Lastly, the applications of these results for calculating oxygen transport to incubating salmon eggs and minimum water flows in hatcheries are discussed.Key words: Salmon enhancement, oxygen transport, permeability, gravel, incubation, hatcheries

Control of nasal dilator muscle activities during exercise: role of nasopharyngeal afferents

1996 ◽  
Vol 80 (5) ◽  
pp. 1520-1527 ◽  
Author(s):  
J. Sullivan ◽  
D. Fuller ◽  
R. F. Fregosi
Keyword(s):  
Exercise Intensity ◽  
Airway Resistance ◽  
Upper Airway ◽  
Receptor Activity ◽  
Emg Activity ◽  
Nasal Airway ◽  
Bicycle Exercise ◽  
Dilator Muscle ◽  
Response To Exercise

Our primary aim was to determine whether reducing the activity of nasal airway receptors would influence drive to the nasal dilator muscles (NDMs) during exercise. We used lidocaine (2%) or nasal splints to diminish afferent airway receptor activity and measured the electromyogram (EMG) activity of the NDMs during incremental bicycle exercise in subjects who breathed nasally. NDM EMG activities increased as a function of exercise intensity but were not changed by lidocaine and were only slightly reduced by splinting. Similarly, neither intervention altered the normal decrease in NDM EMG activity associated with reductions in airway resistance evoked by He-O2 breathing. We also compared the NDM EMG response to exercise with that evoked by CO2 rebreathing at rest to determine whether the nature of the ventilatory stimulus influences drive to the NDMs; comparisons were made at constant levels of nasal inspired ventilation and, therefore, constant total ventilatory output. The increase in EMG activity was much higher during exercise compared with hyperoxic hypercapnia. In conclusion, 1) desensitizing the nasal airway does not alter NDM activity significantly during exercise and 2) exercise results in much greater increases in NDM activity compared with hypercapnia, indicating that different ventilatory stimuli can evoke more or less activation of upper airway motoneurons, even when comparisons are made at constant levels of total ventilatory output.

Sign in / Sign up

Export Citation Format

Share Document