Chest
Laboratory and Animal InvestigationsNasal Continuous Positive Airway Pressure Devices Do Not Maintain the Set Pressure Dynamically When Tested Under Simulated Clinical Conditions
Section snippets
Materials and Methods
Testing was performed in the Pulmonary Laboratory at LDSHospital in Salt Lake City, UT. The average ambient barometric pressureat the altitude of 1,400 m is 647 mm Hg, average temperature was22°C, and average relative humidity was 37%.
A schematic of the experimental design is shown in Figure 1. A pulmonary waveform generator (PWG) was used to simulate tidalbreathing of a patient (PWG System S/N 714; MH Custom Design &Manufacturing; Midvale, UT). The PWG is precise and reproducible andhas been
Steady Flow Conditions
All four devices performed equivalently under steady flowconditions (ie, without simulated respiration). There was nosignificant pressure drop due to increasing resistance with any systemconfiguration during steady flow. The mean pressure decrease from thedevice to the mask was 0.36 cm H2O.
Dynamic Flow Conditions
Pressure measured at the mask was found to vary substantially inparallel with the respiratory cycle, with minimal phase delay and withvery little difference between machines. For example, in the
Discussion
The major conclusion from this study is that some currently usedCPAP machines do not maintain a constant continuous set mask pressurewhen tested using simulated ordinary clinical conditions. Differencesamong the four machines used in this study were not clinicallyimportant with either steady-state or dynamic tests; with all devices,the main deviation from the set pressure was a decrease during earlyinspiration. Various alterations of the apparatus and especially theaccumulation of water
References (23)
- et al.
Performance evaluation of contemporary spirometers
Chest
(1990) Breathing in sleep
- et al.
Long-term compliance with nasal continuous positive airway pressure therapy of obstructive sleep apnea
Chest
(1990) - et al.
Acceptance of CPAP therapy for sleep apnea
Chest
(1991) - et al.
Self-reported use of CPAP and benefits of CPAP therapy: a patient survey
Chest
(1996) - et al.
Predictive factors of long-term compliance with nasal continuous positive airway pressure treatment in sleep apnea syndrome
Chest
(1994) - et al.
Group education sessions and compliance with nasal CPAP therapy
Chest
(1997) - et al.
Effects of humidification on nasal symptoms and compliance in sleep apnea patients using continuous positive airway pressure (CPAP)
Chest
(1999) - et al.
The occurrence of sleep-disordered breathing among middle-aged adults
N Engl J Med
(1993) - et al.
Snoring and sleep apnea: a population study in Australian men
Am J Respir Crit Care Med
(1995)
A community study of snoring and sleep-disordered breathing: prevalence
Am J Respir Crit Care Med
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Financial support was provided by the Deseret Foundation, LDS Hospital,Salt Lake City, UT.
Equipment was provided by the Devilbiss Corporation and IntermountainHome Health Care.
Study data were presented at the American Thoracic Society Annualmeeting, San Diego, CA, April 23–28, 1999.