scholarly journals Evaluation of a Humidified Nasal High-Flow Oxygen System, Using Oxygraphy, Capnography and Measurement of Upper Airway Pressures

2011 ◽  
Vol 39 (6) ◽  
pp. 1103-1110 ◽  
Author(s):  
J. E. Ritchie ◽  
A. B. Williams ◽  
C. Gerard ◽  
H. Hockey
Keyword(s):  
Healthy Volunteers ◽  
Airway Pressure ◽  
Gas Flow ◽  
Air Entrainment ◽  
High Flow ◽  
Positive Pressure ◽  
Mean Airway Pressure ◽  
Flow Rates ◽  
Oxygen Fraction ◽  
Airway Pressures

In this study, we evaluated the performance of a humidified nasal high-flow system (Optiflow™, Fisher and Paykel Healthcare) by measuring delivered FiO2 and airway pressures. Oxygraphy, capnography and measurement of airway pressures were performed through a hypopharyngeal catheter in healthy volunteers receiving Optiflow™ humidified nasal high flow therapy at rest and with exercise. The study was conducted in a non-clinical experimental setting. Ten healthy volunteers completed the study after giving informed written consent. Participants received a delivered oxygen fraction of 0.60 with gas flow rates of 10, 20, 30, 40 and 50 l/minute in random order. FiO2, FEO2, FECO2 and airway pressures were measured. Calculation of FiO2 from FEO2 and FECO2 was later performed. Calculated FiO2 approached 0.60 as gas flow rates increased above 30 l/minute during nose breathing at rest. High peak inspiratory flow rates with exercise were associated with increased air entrainment. Hypopharyngeal pressure increased with increasing delivered gas flow rate. At 50 l/minute the system delivered a mean airway pressure of up to 7.1 cmH2O. We believe that the high gas flow rates delivered by this system enable an accurate inspired oxygen fraction to be delivered. The positive mean airway pressure created by the high flow increases the efficacy of this system and may serve as a bridge to formal positive pressure systems.

Indomethacin compromises hemodynamics during positive-pressure ventilation, independently of prostanoids

1993 ◽  
Vol 74 (4) ◽  
pp. 1672-1678 ◽  
Author(s):  
D. D. Malcolm ◽  
J. L. Segar ◽  
J. E. Robillard ◽  
S. Chemtob
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Cerebral Blood Flow ◽  
Airway Pressure ◽  
Regional Blood Flow ◽  
Blood Gases ◽  
Positive Pressure ◽  
Organ Blood Flow ◽  
Mean Airway Pressure ◽  
Airway Pressures

We examined whether prostanoids contribute to the impaired cardiac function and decrease in regional blood flow induced by increasing mean airway pressure. Using microspheres, we measured cardiac output and major organ blood flow and assayed prostaglandin E2, 6-ketoprostaglandin F1 alpha, and thromboxane B2 in blood at mean airway pressures of 5–25 cmH2O in mechanically ventilated newborn piglets treated with ibuprofen (40 mg/kg, n = 6), indomethacin (0.3 mg/kg, n = 6), or vehicle (n = 6). Blood gases and pH were stable throughout the experiments. Prostanoid levels remained constant with increasing mean airway pressure in vehicle-treated pigs and were unchanged by indomethacin. However, ibuprofen decreased the prostanoid levels at all mean airway pressures studied (P < 0.01). As ventilatory pressure was progressively increased, cardiac output decreased gradually and similarly by 42–45% (P < 0.05) in all groups. At the highest mean airway pressure, blood flow decreased to the kidneys by 37–57%, to the ileum by 58–74%, and to the colon by 53–71% (P < 0.05) in all groups. Cerebral blood flow remained constant at all ventilatory pressures regardless of the treatment. There was no difference in cardiac output and regional hemodynamics between ibuprofen- and vehicle-treated animals. However, after indomethacin, ileal blood flow at the higher ventilatory pressures was 41–46% lower and cerebral blood flow at all mean airway pressures was 14–25% lower than after the other treatments (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Patterns of gas flow in the upper bronchial tree

1959 ◽  
Vol 14 (5) ◽  
pp. 753-759 ◽  
Author(s):  
J. B. West ◽  
P. Hugh-Jones
Keyword(s):  
Gas Flow ◽  
Lower Lobe ◽  
Bronchial Tree ◽  
High Flow ◽  
Human Beings ◽  
Lobe Bronchus ◽  
Flow Rates ◽  
Expiratory Flow ◽  
Different Gases ◽  
Expiratory Flow Rates

Patterns of gas flow in the upper bronchial tree have been studied by observing the flow of dye and different gases through a lung cast, and by measurements made on open-chested dogs and on human beings at bronchoscopy. Flow is completely laminar throughout the bronchial tree at low expiratory flow rates (up to 10 l/min.) and completely turbulent, proximal to the segmental bronchi, at high flow rates (80 l/min.). Both at low and high expiratory flow rates, gas from segmental bronchi was not uniformly mixed in the lobar or main bronchi which they supplied. The composition of a catheter sample in these airways would therefore not be representative of the alveolar gas in the corresponding lobe or lung unless the alveolar gas in all areas distal to the sampling tube was homogeneous. Penetration of the left upper lobe bronchus by gas from the lower lobe was demonstrated in the model and a normal subject at bronchoscopy. Submitted on September 3, 1958

Gas pressure, Volume and Flow Measurement

2011 ◽  
Author(s):  
Patrick Magee ◽  
Mark Tooley
Keyword(s):  
Airway Pressure ◽  
Gas Flow ◽  
Intrathoracic Pressure ◽  
Wheatstone Bridge ◽  
External Pressure ◽  
Electrical Circuit ◽  
Gas Pressure ◽  
Positive Pressure ◽  
Electrical Analogy ◽  
Metal Bellows

The physics of pressure, flow and the gas laws have been discussed in Chapter 7 in relation to the behaviour of gas and vapour. This section will focus on the physical principles of the measurement of gas pressure, volume and flow. Unlike a liquid, a gas is compressible and the relationship between pressure, volume and flow depends on the resistance to gas flow (or impedance if there is a frequency dependence between pressure and flow in alternating flow, see Chapter 4 for the electrical analogy of this) in conduits (bronchi, anaesthetic tubing); it also depends on the compliance of structures being filled and emptied (alveoli, reservoir bags, tubing or bellows). Normal breathing occurs by muscular expansion of the thorax, thus lowering the intrathoracic pressure, allowing air or anaesthetic gas to flow towards the alveoli down a pressure gradient from atmospheric pressure. When positive pressure ventilation occurs, gas is ‘pushed’ under pressure into the alveoli. Depending on the exact relationship between the ventilator and the lungs, different relationships exist between airway pressure (rather than alveolar pressure, which cannot easily be measured) and gas flow and volume. Gas pressure measurement devices were traditionally in the form of an aneroid barometer, a hollow metal bellows calibrated for pressure and temperature, which contracts when the external pressure on it increases, and expands when it decreases. The movement is linked to a pointer and indicator dial. It is often more convenient to make the device in the shape of part of a circular section, but the principle is the same. This is what the Bourdon gauge, which commonly measures pressure in gas cylinders, looks like. The detection of movement of the diaphragm of an aneroid barometer can take several forms. The movement can either be linked via a direct mechanical linkage to a pointer, or diaphragm movement can be linked to a capacitative or inductive element in an electrical circuit, such as a Wheatstone bridge. Airway pressure during spontaneous breathing or artificial ventilation is low. The preferred units of measurement are cm H2O and the range of values is between −20 and +20 cmH2O. The aneroid barometer to measure this will therefore be of light construction, using thin copper for the bellows material.

scholarly journals Association between core body temperature and mean airway pressure with endotracheal cuff pressure in intubated patients of emergency department

2019 ◽  
Vol 35 (5) ◽  
Author(s):  
Zahra Parsian ◽  
Farzad Rahmani ◽  
Ata Mahmoodpoor ◽  
Mahboob Pouraghaei ◽  
Maryam Barzegar Jalali ◽  
...  
Keyword(s):  
Emergency Department ◽  
Body Temperature ◽  
Airway Pressure ◽  
Cuff Pressure ◽  
Core Body Temperature ◽  
Time Factors ◽  
Positive Pressure ◽  
Mean Airway Pressure ◽  
Creative Commons ◽  
Core Body

Background & Objective: Endotracheal intubation is routinely performed in the critical situations. In order to prevent microaspiration and tracheal injury endotracheal cuff pressure is important to remain constant between 20 and 30 cmH2O. Positive pressure ventilation, duration of intubation, body temperature, and body movements can alter endotracheal cuff pressure. This survey was conducted to evaluate core body temperature and cuff pressure relation with airway pressure simultaneously. Methods: This was a descriptive analytic study conducted from March 2018 to July 2018 on 150 intubated patients in the emergency department. All were ventilated with SIMV mode and had Ramsi sedation level of 2‑3. Mean airway pressure was measured simultaneouly with core body temperature measurement from ventilator monitor. All these parameters were measured 10 times each hour and documented. Results: There was a statistically meaningful relation between airway pressure and cuff pressure in the primary evaluation (P=0.02, r=0.19), while none of the subsequent evaluations showed meaningful relation (P>0.05). No significant relation was found between cuff pressure and core body temperature in any of the measurements (P>0.05). Conclusion: The pressure of cuff should be checked repeatedly after intubation because of substantial variation over time. Factors other than core body temperature and airway pressure can influence cuff pressure. doi: https://doi.org/10.12669/pjms.35.5.886 How to cite this:Parsian Z, Rahmani F, Mahmoodpoor A, Pouraghaei M, Jalali MB, Esfanjani RM, et al. Association between core body temperature and mean airway pressure with endotracheal cuff pressure in intubated patients of emergency department. Pak J Med Sci. 2019;35(5):---------. doi: https://doi.org/10.12669/pjms.35.5.886 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Determinants of gas flow through a bronchopleural fistula

1989 ◽  
Vol 67 (4) ◽  
pp. 1591-1596 ◽  
Author(s):  
M. C. Walsh ◽  
W. A. Carlo
Keyword(s):  
Airway Pressure ◽  
Gas Flow ◽  
Bronchopleural Fistula ◽  
Peak Inspiratory Pressure ◽  
Intrathoracic Pressure ◽  
Transpulmonary Pressure ◽  
Inspiratory Pressure ◽  
Positive End Expiratory Pressure ◽  
Inspiratory Time ◽  
Mean Airway Pressure

To assess the determinants of bronchopleural fistula (BPF) flow, we used a surgically created BPF to study 15 anesthetized intubated mechanically ventilated New Zealand White rabbits. Mean airway pressure and intrathoracic pressure were evaluated independently. Mean airway pressure was varied (8, 10, or 12 cmH2O) by independent manipulations of either peak inspiratory pressure, positive end-expiratory pressure, or inspiratory time. Intrathoracic pressure was varied from 0 to -40 cmH2O. BPF flow varied directly with mean airway pressure (P less than 0.001). However, at constant mean airway pressure, BPF flow was not influenced independently by changes in peak inspiratory pressure, positive end-expiratory pressure, or inspiratory time. Resistance of the BPF increased as intrathoracic pressure became more negative. Despite increased resistance, BPF flow also increased. BPF resistance was constant over the range of mean airway (P less than 0.01) pressures investigated. Our data document the influence of mean airway pressure and intrathoracic pressure on BPF flow and suggest that manipulations which reduce transpulmonary pressure will decrease BPF flow.

scholarly journals 958 Different Gas Flow Rates and Effects on Tidal Volume and Mask Leak During Positive Pressure Ventilation

2010 ◽  
Vol 68 ◽  
pp. 478-478
Author(s):  
K Schilleman ◽  
G M Schmölzer ◽  
C O F Kamlin ◽  
A B Te Pas ◽  
C J Morley ◽  
...  
Keyword(s):  
Tidal Volume ◽  
Gas Flow ◽  
Positive Pressure Ventilation ◽  
Positive Pressure ◽  
Flow Rates

scholarly journals High-Flow Nasal Cannula versus Continuous Positive Airway Pressure in Critical Bronchiolitis: A Randomized Controlled Pilot

2020 ◽  
Vol 09 (04) ◽  
pp. 248-255
Author(s):  
Regina Grigolli Cesar ◽  
Bibiane Ramos Pinheiro Bispo ◽  
Priscilla Helena Costa Alves Felix ◽  
Maria Carolina Caparica Modolo ◽  
Andreia Aparecida Freitas Souza ◽  
...  
Keyword(s):  
Pilot Study ◽  
Continuous Positive Airway Pressure ◽  
Treatment Failure ◽  
Airway Pressure ◽  
Positive Airway Pressure ◽  
High Flow ◽  
Nasal Cannula ◽  
Positive Pressure ◽  
High Flow Nasal Cannula ◽  
Randomized Controlled

AbstractWe conducted a randomized controlled pilot study in infants with critical bronchiolitis (n = 63) comparing high-flow nasal cannula (HFNC, n = 35) to continuous positive airway pressure (CPAP, n = 28). The primary outcome was treatment failure, defined as the need for bilevel positive pressure ventilation or endotracheal intubation. Treatment failure occurred in 10 patients (35.7%) in the CPAP group and 13 patients (37.1%) in the HFNC group (p = 0.88). Pediatric intensive care unit length of stay was similar between the CPAP and HFNC groups (5 [4–7] days and 5 [4–8] days, p = 0.46, respectively). In this pilot study, treatment with HFNC resulted in a rate of treatment failure similar to CPAP.

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