Biomedical subjects

Paul N Austin

Publications and source records attributed to Paul N Austin.

5 recordsLinked to original sources

PubMed2006

Pollution of ambient air by volatile anesthetics: a comparison of 4 anesthetic management techniques.

Long-term exposure to waste anesthetic gas (WAG) may lead to health problems. The purpose of this study was to compare WAG concentrations resulting from 4 combinations of fresh gas flow (FGF) and vaporizer settings during a simulated intravenous induction in which the anesthetic is deepened using a volatile anesthetic delivered via mask ventilation before intubation. By using a lung model, WAG was sampled 3 times each using 4 combinations and 3 volatile anesthetics: 3% sevoflurane, 2% isoflurane, and 6% desflurane. The combinations were FGF off/vaporizer on, FGF on/vaporizer off, both on, and both off. WAG was measured using a MIRAN Ambient Air Analyzer placed at a level approximating the anesthetist's head. One-way analysis of variance with a Student-Newman-Keuls post hoc test was used to compare the concentration of WAG among the combinations of FGF/vaporizer settings for each agent. Regardless of the agent, only the FGF on/vaporizer on combination at 60 seconds resulted in a statistically greater WAG level (P < .005). The results support using 3 of the 4 combinations examined when mask ventilation with a volatile agent accompanies intravenous induction. Future studies should examine other methods of controlling WAG levels and use time-weighted averages to help address clinical significance.

Adult↗

PubMed2005

Comparison of oxygen reservoir tube length and imposed work of breathing with the universal portable anesthesia complete.

The Universal Portable Anesthesia Complete is supplied with a 12-inch oxygen reservoir. Previous work suggested that using a longer (greater-volume) reservoir results in a greater inspired oxygen concentration. This study assessed the work of breathing imposed by lengths of reservoir tubing (18, 30, and 48 inches) during simulated spontaneous breathing of an adult anesthetized with isoflurane. Peak negative pressure (PNP) was used as a surrogate of imposed work. There were no clinically significant differences between the PNP with the supplied reservoir tubing and the three lengths of 22-mm corrugated tubing. The PNP ranged between -1.5 and -1.7 cm H2O for the anesthetized condition and between -4.3 and -4.7 cm H2O for the condition modeling emergence from general anesthesia. The morphologic features of the pressure-volume curves corroborated these findings and revealed that little imposed work was attributable to the length of reservoir tubing. These findings should help future investigators seeking to modify the Universal Portable Anesthesia Complete.

Anesthesia, General↗

PubMed2002

Transport ventilators.

Today there are a number of automatic resuscitators and simple and complex transport ventilators on the market. The user must consider the purpose of the device, the patient population to be ventilated and the capabilities of the individual devices before purchasing a transport ventilator.

Critical Illness↗

PubMed2002

Imposed work of breathing during ventilator failure.

INTRODUCTION: Ventilators possess an anti-asphyxia valve that allows spontaneous breathing of ambient air during ventilator failure. This study examined the imposed work of breathing and pressure-time product of 8 critical care and 9 portable ventilators, using a laboratory simulation of spontaneous breathing during ventilator failure. METHODS: A test lung was modified to simulate spontaneous breathing with a tidal volume of 0.5 L and peak inspiratory flow of 60 L/min. A pneumotachograph and pressure tap were placed at the proximal airway between the breathing circuit and endotracheal tube. Flow was derived from the pressure drop across the pneumotachograph. Signals were amplified, integrated, and saved to a spreadsheet program, and imposed work of breathing and pressure-time product were calculated. Also measured were the inspiratory pressure required to open the anti-asphyxia valve (cracking pressure), time to cracking pressure, maximum negative inspiratory pressure, and time to maximum negative inspiratory pressure. RESULTS: For the critical care ventilators the mean +/- SD imposed work of breathing ranged from 213.07 +/- 3.53 to 890.63 +/- 0.88 mJ/L and the pressure-time product ranged from 2.67 +/- 0.01 to 13.37 +/- 0.01 cm H(2)O x s/L. For the portable ventilators the mean +/- SD imposed work of breathing ranged from 361.37 +/- 1.22 to 969.60 +/- 22.70 mJ/L and the pressure-time product ranged from 4.52 +/- 0.01 to 16.70 +/- 0.37 cm H(2)O x s/L. CONCLUSIONS: Spontaneous breathing during ventilator failure may impose work approximating the physiologic work of breathing. This imposed work may prevent effective breathing through the anti-asphyxia valve during mechanical ventilator failure due to electrical failure. These results reinforce the need to properly monitor mechanically ventilated patients and to have in place sufficient back-up power supplies and a method of manual ventilation.

Equipment Design↗

PubMed2002

Battery duration of portable ventilators: effects of control variable, positive end-expiratory pressure, and inspired oxygen concentration.

INTRODUCTION: Portable ventilators require battery power during transport or when alternating current is unavailable. Manufacturers report battery duration at nominal ventilator settings. METHODS: We studied the effects of control variable (pressure control vs volume control), positive end-expiratory pressure (PEEP), and fraction of inspired oxygen (F(IO)(2)) on the battery duration of 8 portable ventilators: Achieva, HT50, iVent201, LTV1000, TBird Advanced Ventilator System (AVS), Avian, Uni-Vent 750, and Uni-Vent 754. Each ventilator was set to ventilate a test lung at a rate of 10 breaths/min, tidal volume of 750 mL, and inspiratory time of 1.5 s, with volume-controlled ventilation and then pressure-controlled ventilation (PCV), if available. F(IO)(2) was set at 0.21 and then 1.0. PEEP was set at 0, 10, and then 20 cm H(2)O. Test lung compliance and resistance were set at 20 mL/cm H(2)O and 5 cm H(2)O/L/s, respectively. Five trials were performed with each portable ventilator, with each combination of settings. Time to low-battery alarm, battery-empty alarm, and failure to ventilate the test lung were recorded. Portable ventilator performance during the trials was determined by continuous recording of tidal volume. RESULTS: The battery duration of pneumatically driven portable ventilators is longer than that of electrically driven portable ventilators. The battery duration of pneumatically driven portable ventilators is minimally affected by ventilator settings. The battery duration of electrically driven portable ventilators is shortened by use of PCV, increasing PEEP, and increasing F(IO)(2). Compared to zero PEEP, PEEP of 20 cm H(2)O reduced battery duration with HT50 (40%), LTV1000 (37%), TBird AVS (34%), and Achieva (15%). Compared to volume-controlled ventilation, PCV reduced battery duration with the LTV1000 (48%) and TBird AVS (18%). Compared to F(IO)(2) of 1.0, F(IO)(2) of 0.21 reduced battery duration with the Uni-Vent 754 (37%). Compared to F(IO)(2) of 0.21, F(IO)(2) of 1.0 reduced battery duration with the LTV1000 (17%) and TBird AVS (15%). The iVent201 was unable to deliver the set tidal volume with PCV and 20 cm H(2)O PEEP. Low-battery alarms functioned properly on all the ventilators. CONCLUSIONS: Battery duration differs greatly among the portable ventilators tested. Clinicians must be aware that portable ventilator battery duration is affected by control settings, lung impedance characteristics, and portable ventilator characteristics. Battery duration may be shorter than that reported in the operator's manual for each portable ventilator tested.

Electric Power Supplies↗