PubMed · 7760286
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R T Williamson. 1995. Cast core precementation preparation.. https://doi.org/10.1016/s0022-3913(05)80214-8
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OBJECTIVE: With a high-frequency percussive ventilator and a mechanical lung model, to measure tidal volume (V(T)), pulsatile pressure amplitude (difference between peak and nadir pulsatile pressure [DeltaP];), and mean airway pressure (P (aw)) at various pulsatile frequencies, pulsatile inspiratory-expiratory ratios (I:E(p)), and pressures (measured at the interface between the pulse-generator and the endotracheal tube [P(vent)]). METHODS: With the endotracheal tube inside an artificial trachea, we manipulated the high-frequency percussive ventilation settings and adjuncts, including pulsatile frequency, I:E(p), and P(vent) by manipulating pulsatile flow. We also studied the effects of partially deflating the endotracheal tube cuff. We measured P (aw), pulsatile pressure amplitude at the carina (DeltaP(c)), and pulsatile V(T) at the carina. With the cuff partly deflated, we measured the fraction of inspired oxygen (F(IO(2))) in the gas efflux above and below the cuff. RESULTS: Increasing the pulsatile frequency from 300 cycles/min to 600 cycles/min and changing the I:E(p) from 1:3 to 1:1 significantly reduced V(T) (p < 0.001). P (aw) and DeltaP(c) were unaffected by the change in pulsatile frequency or I:E(p), except when we did not preserve the pulsatile flow. The measured V(T) range was from 19.1 mL (at 600 cycles/min) to 47.3 mL (at 300 cycles/min). Partial cuff deflation did not significantly reduce P (aw) or DeltaP(c), but it did significantly reduce V(T) and F(IO(2)). CONCLUSION: During high-frequency percussive ventilation, the pulsatile frequency is inversely related to V(T). Partial cuff deflation reduces the delivered F(IO(2)).
BACKGROUND: Long-term compliance is suboptimal in the treatment of the obstructive sleep apnea syndrome (OSAS). OBJECTIVES: We compared the efficacy of and the adherence to automatic continuous positive airway pressure (APAP) and constant continuous positive airway pressure (CPAP) based on a night-by-night analysis. METHODS: We performed a randomized, single-blind crossover study in 20 patients with moderate-to-severe OSAS. After diagnostic polysomnography and manual titration, patients were treated for 8 weeks with both constant CPAP and APAP in random order. Compliance and leakage were analyzed night by night using the software LOGSoft of the Magellan iPAP device. RESULTS: The reduction in the apnea/hypopnea index (baseline 32.9 +/- 19.1/h, CPAP 4.6 +/- 2.9/h, APAP 5.6 +/- 3.6/h; p < 0.001 compared to baseline) and the Epworth Sleepiness Scale (baseline 10.3 +/- 5.7, CPAP 6.6 +/- 4.8, APAP 4.9 +/- 4.6; p < 0.001 compared to baseline) did not significantly differ between the treatment modes. Leakage time and compliance per night were not statistically different (leakage CPAP 31 +/- 57 min, APAP 25 +/- 49 min; compliance CPAP 383 +/- 116 min, APAP 382 +/- 107 min). There was no correlation between leakage and compliance. Thirteen patients (65%) preferred APAP at the end of the study. CONCLUSIONS: Treatment efficacy and adherence are similar with CPAP and APAP. There is a trend towards lower leakage with APAP therapy. Patients prefer the automatic mode to fixed pressure.