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Biomedical subjects

J L Benumof

Publications and source records attributed to J L Benumof.

At least 19 recordsLinked to original sources
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

General anesthesia and exhaled breath hydrogen peroxide.

To study the role of free radical formation on the impairment of pulmonary function seen with general anesthesia, we measured the hydrogen peroxide (H2O2) concentration in the exhaled breath condensate of 27 patients. Patients were divided into three study groups: a healthy patient group (group 1, n = 15) consisting of ASA physical status 1 and 2 patients undergoing elective noncardiothoracic surgery; a specific anesthetic event group (group 2, n = 6) composed of patients undergoing cardiopulmonary bypass (CPB); and a positive control group (group 3, n = 6) consisting of patients with the adult respiratory distress syndrome (ARDS). The exhaled breath condensate was collected by diverting exhaled breath through a glass condensation coil submerged in an ice/salt water bath. The exhaled breath condensate samples were then assayed using a spectrophotometric method. In group 1, samples were collected before and after the induction of general anesthesia with intravenous drugs, and before and after the administration of the inhalational anesthetics isoflurane (1.5%) (n = 7) or N2O (70%) (n = 8). In group 2, samples were collected pre- and post-CPB, and in group 3, when specific diagnostic criteria for ARDS were met. There was no significantly detectable H2O2 (not significantly different from zero) in any of the samples from the group 1 patients. Similarly, group 2 patients had exhaled breath H2O2 concentrations near zero except for one patient who was positive for the lupus anticoagulant. Group 3 patients had a mean (+/- SE) exhaled breath H2O2 concentration of 0.55 (+/- 0.08) microM, which was significantly greater than zero (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, General↗
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

Operative lung constant positive airway pressure with the Univent bronchial blocker tube.

Constant positive airway pressure (CPAP) to the operative lung during one-lung ventilation (1-LV) with a double-lumen tube increases PaO2; there have been no reports of application of CPAP to the operative lung during 1-LV with the Univent bronchial blocker (BB) tube. This study determined the method of administration and the effect on PaO2 of 10 cm H2O of CPAP to the operative lung during 1-LV (1-LV + 10 CPAP) produced by the Univent BB system. We designed our CPAP system for the Univent BB using an in vitro lung model so that low O2 flow rates (2-4 L/min) yielded clinically relevant levels of CPAP (5-20 cm H2O) over a wide range of lung compliance. The CPAP system simply consisted of placing a resistance to a variable oxygen flow distal to the operative lung. Seven consenting patients who required thoracotomy and 1-LV were anesthetized and their tracheas were intubated with the Univent BB tube; the BB was inserted into the appropriate mainstem bronchus until the proximal surface of the BB cuff was just distal to the tracheal carina. PaO2 was measured in the seven patients during 12 sequences of two-lung ventilation (2-LV), one-lung ventilation (1-LV), and 1-LV with 10 cm H2O CPAP (1-LV + 10 CPAP). 1-LV + 10 CPAP was always instituted on the deflation phase of a previous single tidal inhalation. We found in our patients with a lung compliance of 32 +/- 4 mL/cm H2O that 2.4 +/- 0.2 L/min of oxygen flow produced 1-LV + 10 CPAP.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
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↗
PubMed1992

Comparison of two techniques to inflate the bronchial cuff of the Univent tube.

The Univent tube is an endotracheal tube with a movable bronchial blocker. The blocker cuff reportedly exhibits high-pressure characteristics when inflated to seal any adult bronchus. This study was aimed at measuring the cuff volume that would seal the bronchus when two different techniques of cuff inflation were used. One technique is based on creating negative pressure and the other is based on creating positive pressure within the breathing system. In addition, we directly measured the compliance characteristics of the cuff. The study was performed in eight adult patients undergoing thoracotomy. The negative pressure technique of cuff inflation (NPT) was tested by applying -150 mm Hg of pressure to the blocker lumen, causing loss of volume in the breathing system as evidenced by deflation of the reservoir bag. The blocker cuff was then inflated until the bag ceased to deflate. In the positive pressure technique of cuff inflation (PPT), the blocker lumen was connected to a beaker of water while maintaining pressure of +30 mm Hg within the breathing system. The bronchial cuff was then inflated until air bubbles ceased to appear in the beaker. Direct measurement of compliance of the blocker cuff confirmed its high-pressure characteristics. Bronchial sealing volume ranged from 3 to 5 mL when measured with the NPT and from 4 to 6 mL when measured with the PPT.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Buccal pulse oximeter is more accurate than finger pulse oximeter in measuring oxygen saturation.

Although there have been several anecdotal reports of the use of buccal pulse oximeter monitoring (Spo2) when digital Spo2 monitoring cannot be used, there have been no objective evaluations of the accuracy of buccal Spo2 monitoring. The purpose of this study was to systematically compare buccal Spo2 monitoring to both digital Spo2 and arterial O2 saturation monitoring (Sao2) in both generally anesthetized patients in the operating room (n = 31) and critically ill patients in the intensive care unit (n = 23). Buccal Spo2 probes were prepared by taping a malleable metal bar securely over the back of a Nellcor Oxisensor D-25 probe and bending the metal bar and buccal probe firmly around the corner of the patient's mouth. All buccal and finger Spo2 and Sao2 measurements were made simultaneously during hemodynamic stability. We found that buccal Spo2 was higher than finger Spo2 and agreed more closely with Sao2 for both patient groups (98.1% +/- 2.6%, 96.8% +/- 3.5%, 98.5% +/- 2.5%, respectively [mean +/- SD]). The operating room patients had higher buccal and finger Spo2 and Sao2 (99.3% +/- 1.5%, 98.9% +/- 1.4%, 99.5% +/- 0.7%, respectively) than the intensive care unit patients (96.4% +/- 2.9%, 94.1% +/- 3.5%, 96.6% +/- 3.5%, respectively). Although buccal Spo2 monitoring has several disadvantages (i.e., the probe requires preparation, can be more difficult to place, may be less readily accepted in awake patients, and is often mechanically dislodged during airway maneuvers), we conclude that buccal Spo2 monitoring is a more than adequate oximetry alternative when digital Spo2 monitoring is not an option (digits are unavailable or available digits are mechanically interfered with).

Blood Gas Analysis↗
PubMed1991

Auscultation cannot distinguish esophageal from tracheal passage of tube.

We quantitatively compared the acoustic characteristics of passage of an endotracheal tube into the trachea with those of passage into the esophagus by analyzing the loudness and frequency (90% spectral edge frequency) of the sounds when auscultated at the suprasternal notch. We found that there was a significant difference (P less than 0.01) in maximum loudness between esophageal and tracheal intubations (0.15 +/- 0.05 and 0.25 +/- 0.06 V, respectively). However, there were no significant differences between the 90% spectral edge frequencies. We conclude that, without directly comparing the maximal acoustic amplitude of tracheal intubation with that of esophageal in each patient, one cannot distinguish between the two types of intubation by means of auscultation.

Auscultation↗
PubMed1991

IPPV plus low-flow intermittent oxygen insufflation (end-exhalation to beginning inhalation) does not improve CO2 elimination.

It has been previously reported that continuous insufflation of low-flow O2 (0.05 to 0.20 L/kg/min), both supracarinally and subcarinally, in addition to intermittent positive-pressure ventilation (IPPV) (IPPV + O2 at a specific flow rate) caused progressive hemodynamic deterioration in patients. As demonstrated in a subsequent mechanical lung model, the hemodynamic deterioration was most probably due to lung hyperexpansion. The purpose of this study was to test the hypothesis that the O2 retarded the outflow of gas from the lung during exhalation and that if the insufflation were limited to the period of time from the end of tidal exhalation (EE) to the beginning of the next IPPV tidal inspiration (BI), lung hyperexpansion would not occur. The use of intermittent O2 in addition to IPPV was studied in both a mechanical lung model and in patients under general anesthesia; the mechanical lung model permitted direct examination of lung volume, and the patient study allowed determination of gas exchange effects. In the mechanical lung model and in the patients, a wide range of EE-BI O2 flow rates were used; respectively, 1 to 40 L/min and 0.05 to 0.20 L/kg/min. In the mechanical lung model, lung pressure and volume at EE and end-inspiration did not increase as long as the O2 flow was kept at or below 10 L/min. In the patients, airway pressure and hemodynamics did not change appreciably, but there was also no increase in CO2 elimination.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Management of the difficult adult airway. With special emphasis on awake tracheal intubation.

Difficulty in managing the airway is the single most important cause of major anesthesia-related morbidity and mortality. Successful management of a difficult airway begins with recognizing the potential problem. All patients should be examined for their ability to open their mouth widely and for the structures visible upon mouth opening, the size of the mandibular space, and ability to assume the sniff position. If there is a good possibility that intubation and/or ventilation by mask will be difficult, then the airway should be secured while the patient is still awake. In order for an awake intubation to be successful, it is absolutely essential that the patient be properly prepared; otherwise, the anesthesiologist will simply fulfill a self-defeating prophecy. Once the patient is properly prepared, it is likely that any one of a number of intubation techniques will be successful. If the patient is already anesthetized and/or paralyzed and intubation is found to be difficult, many repeated attempts at intubation should be avoided because progressive development of laryngeal edema and hemorrhage will develop and the ability to ventilate the lungs via mask consequently may be lost. After several attempts at intubation, it may be best to awaken the patient, do a semielective tracheostomy, or proceed with the case using mask ventilation. In the event that the ability to ventilate via mask is lost and the patient's lungs still cannot be ventilated, TTJV should be instituted immediately. Tracheal extubation of a patient with a difficult airway over a jet stylet permits a controlled, gradual, and reversible (in that ventilation and reintubation is possible at any time) withdrawal from the airway. Significant advances in the management of the difficult airway have occurred in recent years. Eighty percent of the 127 references in this article were published after 1985. However, there is much more to learn with regard to recognition of the difficult airway, preparation of the patient for an awake intubation, new techniques of endotracheal intubation, and establishment of gas exchange in patients who cannot be intubated or ventilated by mask. As the anesthesiologist's ability to manage the difficult airway significantly improves, respiratory-related morbidity and mortality will decrease.

Airway Obstruction↗