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Simulated flying altitude and performance of continuous positive airway pressure devices
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Anaesthesiology. Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation, Physiotherapy. Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.ORCID iD: 0000-0003-1523-1672
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Anaesthesiology.
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Anaesthesiology.
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Anaesthesiology.
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2014 (English)In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 85, no 11, 1092-1099 p.Article in journal (Refereed) Published
Abstract [en]

INTRODUCTION: Continuous positive airway pressure (CPAP) is used in air ambulances to treat patients with impaired oxygenation. Differences in mechanical principles between CPAP devices may affect their performance at different ambient air pressures as will occur in an air ambulance during flight. METHODS: Two different CPAP systems, a threshold resistor device and a flow resistor device, at settings 5 and 10 cm H2O were examined. Static pressure, static airflow and pressure during simulated breathing were measured at ground level and at three different altitudes (2400 m (8 kft), 3000 m (10 kft) and 10700 m (35 kft)). RESULTS: When altitude increased, the performance of the two CPAP systems differed during both static and simulated breathing pressure measurements. With the threshold resistor CPAP, measured pressure levels were close to the preset CPAP level. Static pressure decreased 0.71 ± 0.35 cm H2O, at CPAP 10 cm H2O, comparing ground level and 35 kft. With the flow resistor CPAP, as the altitude increased CPAP produced pressure levels increased. At 35 kft, the increase was 5.13 ± 0.33 cm H2O at CPAP 10 cm H2O. DISCUSSION: The velocity of airflow through the flow resistor CPAP device is strongly influenced by reduced ambient air pressure leading to a higher delivered CPAP effect than the preset CPAP level. Threshold resistor CPAP devices seem to have robust performance regardless of altitude. Thus, the threshold resistor CPAP device is probably more appropriate for CPAP treatment in an air ambulance cabin, where ambient pressure will vary during patient transport.

Place, publisher, year, edition, pages
Aerospace Medical Association , 2014. Vol. 85, no 11, 1092-1099 p.
Keyword [en]
continuous positive airway pressure, air ambulance, threshold resistor, flow resistor, bench study
National Category
Anesthesiology and Intensive Care
Identifiers
URN: urn:nbn:se:umu:diva-93675DOI: 10.3357/ASEM.4013.2014ISI: 000343642500004PubMedID: 25329941OAI: oai:DiVA.org:umu-93675DiVA: diva2:750788
Available from: 2014-09-30 Created: 2014-09-30 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Resistance breathing with PEP and CPAP: effects on respiratory parameters
Open this publication in new window or tab >>Resistance breathing with PEP and CPAP: effects on respiratory parameters
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: Positive expiratory pressure (PEP) and continuous positive airway pressure (CPAP) are two forms of resistance breathing used in spontaneously breathing patients. With a threshold resistor or a flow resistor, both PEP and CPAP provide a positive (elevated) pressure level during the expiratory phase. With PEP, inspiratory pressure is negative, i.e. lower than ambient air pressure, as during a normal inspiration, but with CPAP, the inspiratory pressure is positive, i.e. higher than ambient air pressure.

Methods: This thesis is based on four separate studies in which four different breathing devices, a PEP-bottle (threshold resistor device), a PEP-mask (flow resistor device), a threshold resistor CPAP and a flow resistor device were investigated. Paper I, II and III are based on studies in healthy volunteers. Paper IV is a bench study performed in a hypobaric chamber. Paper I examined differences between two PEP devices, the PEP-bottle and the PEP-mask. Paper II evaluated the performance of a flow resistor CPAP device, (Boussignac CPAP). Paper III investigated the effect of two PEP-devices, a PEP-bottle and a PEP-mask and two CPAP devices, a threshold resistor CPAP and a flow resistor CPAP, on inspiratory capacity (IC). In paper IV, the effect of changes in ambient pressure on preset CPAP levels in two different CPAP devices was compared.

Results: With the PEP bottle, both expiration and inspiration began with a zero-flow period during which airway pressure changed rapidly. With the PEP-mask, the zero-flow period was very short and the change in airway pressure almost non-existent (paper I). During normal breathing with the Boussignac CPAP, changes in airway pressure were never large enough to reduce airway pressure below zero. During forced breathing, as airflow increased, both the drop in inspiratory airway pressure and the increase in expiratory airway pressure were potentiated (paper II). IC decreased significantly with three of the breathing devices, the PEP-mask and the two CPAP devices (paper III). With the threshold resistor CPAP, measured pressure levels were close to the preset CPAP level. With the flow resistor CPAP, as the altitude increased CPAP produced pressure levels increased (paper IV).

Conclusion: The effect on airway pressure, airflow, IC and the effect of changes in ambient air pressure differ between different kinds of resistance breathing devices. These differences in device performance should be taken into consideration when choosing the optimal resistance breathing device for each patient.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2014. 72 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1674
Keyword
Chest physiotherapy, breathing exercises, PEP, CPAP, airway pressure, airflow, threshold resistor, flow resistor, inspiratory capacity, Borg CR10
National Category
Physiotherapy
Identifiers
urn:nbn:se:umu:diva-94650 (URN)978-91-7601-127-0 (ISBN)
Public defence
2014-11-07, Sal B, Unod T, 9tr, Norrlands Universitetssjukhus, Umeå, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2014-10-16 Created: 2014-10-14 Last updated: 2015-11-30Bibliographically approved

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