Effect of air leak on the performance of auto-PAP devices: a bench study.
ABSTRACT Automatic positive airway pressure (auto-PAP) devices, used in the treatment of patients with obstructive sleep apnea (OSA), may not function optimally in the presence of an air leak. We set out to determine the magnitude of air leak that prevents auto-PAP devices from responding to respiratory events of OSA in a bench model. We simulated apnea, flow limitation, obstructive hypopnea, nonobstructive hypopnea, and snoring events of OSA with an artificial airway and a loudspeaker in a bench model connected to a commercially available auto-PAP device. Four auto-PAP devices were tested, but two of the "older-generation" devices (Tranquility and Virtuoso) did not respond to events of OSA that involved changes in flow contour; hence, we studied the effects of air leak and humidifier in the two "newer-generation" auto-PAP devices only (GoodKnight 418P, Autoset-T). When the air leak was progressively increased from baseline levels recommended by the manufacturer to levels seen clinically--5 to 7, 10, and 30 l/min--the GoodKnight 418P decreased pressure response by 56% (5.6+/-1.8 cm H(2)O, p=0.04). The pressure response of the Autoset-T, however, did not change from baseline during similar levels of air leak. The GoodKnight performed appropriately when the air leak was within 20 l/min, but the corresponding value for the Autoset was higher at 50 l/min. For both devices combined, air leak caused the pressure to drop between the device and the airway: 2.8+/-0.3 cm H(2)O at 30 l/min of air leak (p<0.001). Air leaks cause auto-PAP devices to underestimate the pressure required to treat events of OSA and to overestimate the pressure delivered at the upper airway. Physicians should be aware of performance limitations of auto-PAP devices in the presence of an air leak.
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ABSTRACT: Noninvasive ventilation with pressure support (NIV-PS) therapy can augment ventilation; however, such therapy is fixed and may not adapt to varied patient needs. We tested the hypothesis that in patients with chronic respiratory insufficiency, a newer mode of ventilation [averaged volume assured pressure support (AVAPS)] and lateral decubitus position were associated with better sleep efficiency than NIV-PS and supine position. Our secondary aim was to assess the effect of mode of ventilation, body position, and sleep-wakefulness state on minute ventilation (V(E)) in the same patients. Single-blind, randomized, cross-over, prospective study. Academic institution. Twenty-eight patients. NIV-PS or AVAPS therapy. Three sleep studies were performed in each patient; prescription validation night, AVAPS or NIV-PS, and crossover to alternate mode. Sleep was not different between AVAPS and NIV-PS. Supine body position was associated with worse sleep efficiency than lateral decubitus position (77.9 +/- 22.9 and 85.2 +/- 10.5%; P = 0.04). V(E) was lower during stage 2 NREM and REM sleep than during wakefulness (P < 0.0001); was lower during NIV-PS than AVAPS (P = 0.029); tended to be lower with greater body mass index (P = 0.07), but was not influenced by body position. In patients with chronic respiratory insufficiency, supine position was associated with worse sleep efficiency than the lateral decubitus position. AVAPS was comparable to NIV-PS therapy with regard to sleep, but statistically greater V(E) during AVAPS than NIV-PS of unclear significance was observed. V(E) was determined by sleep-wakefulness state, body mass index, and mode of therapy.Intensive Care Medicine 09/2008; 35(2):306-13. DOI:10.1007/s00134-008-1276-4 · 7.21 Impact Factor
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ABSTRACT: Over the past few decades, continuous positive airway pressure (CPAP) therapy for obstructive sleep apnea has evolved into more and more sophisticated modes of therapy for various forms of sleep-disordered breathing. While the principles of splinting the airway and delivering assisted ventilation underpin the basics of this therapy, the introduction of newer technologies and miniaturization are revolutionizing the former conventions of the field. The purpose of this review is to improve our understanding of various forms of PAP therapy by providing the rationale for such modalities, gaining a basic working knowledge of device technology, and critically assessing the clinical research evidence while identifying barriers to implementation. Dissemination of such information is vital in order to prevent knowledge gaps in healthcare providers and systems.Respiratory care 09/2010; 55(9):1216-29. · 1.84 Impact Factor