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Biomedical subjects

S D Gaughan

Publications and source records attributed to S D Gaughan.

5 recordsLinked to original sources
PubMed1993

Can an anesthesia machine flush valve provide for effective jet ventilation?

Transtracheal jet ventilation (TTJV) using a percutaneously inserted intravenous (IV) catheter for the patient who cannot be ventilated or tracheally intubated or, using a jet stylet for changing endotracheal tubes (ETT) in patients for whom subsequent ventilation and/or tracheal reintubation may be difficult, are extremely valuable therapeutic options. The jet ventilation system must have a sufficiently high pressure-oxygen source to drive oxygen through noncompliant tubing and through relatively small IV catheters and/or jet stylets in order to achieve adequate ventilation and oxygenation. There is no evidence that using the common gas outlet of an anesthesia machine by activating the flush valve can provide enough flow (V) and tidal volume (VT) for effective jet ventilation. This in vitro study utilized a mechanical lung model that had a varying lung compliance [Cset (10-100 mL/cm H2O)] to determine the VT (measured by integrating a pneumotachograph flow signal) and corresponding minute ventilation (VE) through 14-, 16-, and 18-gauge IV catheters and small, medium, and large jet stylets. The flow of O2 was generated by activating the flush valve of Dräger Narkomed 2 and 2A and Ohmeda Modulus II and II Plus anesthesia machines at an inspiratory:expiratory (I:E) ratio = 1:1 (unit of time = 1 s). We found that the largest VT and resultant VE were consistently obtained by activating the flush valve of the Ohmeda Modulus II and Dräger Narkomed 2 anesthesia machines. The smallest VT and VE were produced using the Ohmeda Modulus II Plus anesthesia machine.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗
PubMed1992

The relationship among bronchial blocker cuff inflation volume, proximal airway pressure, and seal of the bronchial blocker cuff.

The resting volume and diameter of the bronchial blocker cuff (defined as inflation of the cuff to just its natural shape) of the Univent (Fuji Systems Corp, Tokyo, Japan) tube are 2 mL and 5 mm. However, much larger inflation volumes may be required to seal an adult mainstem bronchus and the surface area of contact between the resultant spherical or ellipsoid-shaped cuff and the wall of the mainstem bronchus may be small and susceptible to leak with the application of high proximal airway pressures. This experiment determined the relationship among airway diameter, proximal airway pressure, inflation volume of the bronchial blocker cuff, and leakage of air around the bronchial blocker cuff in an in vitro model. The experimental model consisted of silicon tubing of 12.8-, 16.0-, and 19.2-mm ID as the mainstem bronchus. The main tracheal cuff sealed the Univent tube into the proximal end of the mainstem bronchus and the bronchial blocker cuff was inflated with various volumes near the distal end of the mainstem bronchus. The space between the tracheal cuff and the bronchial blocker cuff was then progressively pressurized in either a static or pulsed manner. The very distal end of the bronchus was functionally submerged under a beaker of water so that a bronchial blocker cuff leak would be indicated by bubbling. It was found that the Univent bronchial blocker cuff sealed the 12.8- and 16.0-mm ID mainstem bronchi against airway pressures as great as 100 cmH2O, with inflation volumes that were within the manufacturer's recommendation of 6 to 7 mL.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

A comparison in a lung model of low- and high-flow regulators for transtracheal jet ventilation.

There is widespread agreement that transtracheal jet ventilation (TTJV) using a percutaneously inserted intravenous (iv) catheter through the cricothyroid membrane is a simple, quick, relatively safe, and extremely effective treatment for the situation in which neither ventilation nor intubation can be achieved. No study has reported whether a low-flow pressure-reducing regulator (LFR) can provide enough driving pressure and flow under a variety of clinical circumstances for adequate TTJV. We determined, using a high-flow regulator (HFR) as our control, the tidal volume (VT) (measured by integrating a pneumotachograph signal) that a LFR could deliver via a Carden jet injector through 14- and 20-G iv catheters initially at an inspiratory:expiratory ratio (I:E) = 1:1 (unit of time = 1 s) in a mechanical model that had varying lung compliance (Cset, 10-100 ml/cmH2O) and airway diameters (proximal trachea 15.0, 4.5, or 3.0 mm ID and distal mainstem bronchi 9.0 or 4.5 mm ID). The lowest Cset (10 ml/cmH2O) and smallest airway diameter (tracheal diameter = 3.0 mm, bronchial diameter = 9.0 mm) resulted in the lowest VT (220 and 320 ml for the 20- and 14-G iv catheters, respectively, with the LFR), and the highest Cset (100 ml/cmH2O) and largest airway diameter (tracheal diameter = 15 mm, bronchial diameter = 9.0 mm) resulted in the highest VT (780 and 1040 ml for the 20- and 14-G iv catheters, respectively, with the LFR). The VT produced during TTJV was greatly dependent on air entrainment (measured by a second pneumotachograph), with the contribution to total VT ranging from 15 to 74%; the amount of air entrainment was independently confirmed by excellent agreement between measured and calculated alveolar oxygen concentrations. Decreasing Cset (with the largest airway diameter) and decreasing airway diameter (at Cset = 50 ml/cmH2O) over the full range studied resulted in approximately a 45-80% decrease in VT for all iv catheter/regulator combinations. Increasing Cset and narrowing airway diameter over the full range studied resulted in a progressive increase in end-expiratory volume (EEV) for all iv catheter/regulator combinations. The I:E ratio was also varied from 1:3 to 3:1 (unit of time = 1 s) using the 14-G catheter at Cset = 50 ml/cmH2O with both regulators at the extremes of the proximal tracheal diameters (15.0 and 3.0 mm ID), and we found that jet ventilation through a proximal tracheal diameter of 3.0 mm with the HFR at I:E ratios = 1:1 and 3:1, EEV exceeded the capacity of the mechanical lung (4,000 ml).(ABSTRACT TRUNCATED AT 400 WORDS)

Catheterization, Peripheral↗
PubMed1992

Quantification of the jet function of a jet stylet.

The concept and use of a jet stylet as an additional safety measure during tracheal extubation of patients in whom subsequent ventilation and/or reintubation of the trachea may be difficult has recently been described. If jet ventilation through a jet stylet could provide for effective gas exchange, it would allow additional time to assess the need for reintubation of the trachea. We determined the tidal volumes (measured by integrating a pneumotachograph flow signal) that 50-psi jet ventilation, at an inspiratory to expiratory time ratio of 1:1 (unit of time = 1 s), could deliver through small, medium, and large Sheridan tube exchangers into an in vitro lung model that had lung compliances of 50 and 30 mL/cm H2O (six experimental permutations). The tidal volume (VT) produced during jet ventilation was moderately dependent on air entrainment (measured by a volume spirometer), with the contribution to total VT ranging from 0% to 31%; the amount of air entrainment was confirmed by excellent correlation between the alveolar oxygen concentration (FAO2) measured by an oxygen analyzer and the FAO2 calculated from entrained and total VT. Decreased lung compliance caused decreased VT and end-expiratory volume for all six experimental conditions. The largest VT and minute ventilation (VE) generated were 1680 mL and 51.6 L/min (large tube exchanger, high lung compliance) and the lowest VT and VE were 440 mL and 13.2 L/min (small tube exchanger, low lung compliance), respectively. These findings validate the term "jet stylet" for all three tube exchangers as even the smallest tube exchanger, coupled with a low lung compliance, can provide a VE consistent with total ventilatory support for most clinical situations.

Evaluation Studies as Topic↗