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Biomedical subjects

R R Kirby

Publications and source records attributed to R R Kirby.

At least 37 records · Page 2Linked to original sources
PubMed1991

High-volume, low-pressure cuffs. Are they always low pressure?

Ischemic tracheal complications due to the ETT cuff occur in approximately 10 percent of mechanically ventilated critically ill patients despite the use of high-volume, low-pressure ETT cuffs. Using a laboratory model, we studied the effects of airway pressure on three different ETT cuff designs, including two "low pressure" designs. Positive airway pressure acted on the "low pressure" cuffs to create a "self-sealing" effect that maintained tracheal occlusion despite airway pressures that exceeded cuff inflation pressure. Increases in airway pressure caused by decreased lung compliance resulted in higher cuff inflation pressures in all three groups, with the smallest increase occurring in the design that had the longest tracheal contact length. We conclude that the current high-volume, low-pressure ETT cuff design currently used does not guarantee low cuff pressure when high airway pressures occur, and an alternative design should be developed.

Airway Resistance↗
PubMed1989

Airway pressure release ventilation in a patient with acute pulmonary injury.

Airway pressure release ventilation is a recently described method of ventilatory support. It allows spontaneous ventilation with CPAP but differs from conventional ventilatory modes because, with APRV, peak inflation pressure never exceeds the level of CPAP, and airway pressure decreases, rather than increases, when tidal volume is delivered. The risk of pulmonary barotrauma and adverse hemodynamic effects associated with conventional modes of positive-pressure mechanical ventilation may be decreased because of lower peak inflation and mean airway pressures. We describe a patient in whom several risk factors for these complications were present who was treated successfully with APRV.

Adult↗
PubMed1988

Effects of expiratory flow resistance on inspiratory work of breathing.

To minimize work of breathing, airway pressure should not fluctuate during spontaneous breathing with continuous positive airway pressure (CPAP). However, flow resistance in the inspiratory limb of the breathing circuit and an inadequate continuous gas flow rate result in airway pressure fluctuation and increased work of breathing. Flow resistance of the expiratory pressure/exhalation valve also directly affects the level of airway pressure during spontaneous inhalation with CPAP (the greater the resistance of the valve, the greater the decrease in airway pressure and work of breathing). We compared this effect with three types of expiratory pressure valves: a threshold resistor with low resistance to flow, an inflatable balloon (mushroom) valve with moderate resistance to flow, and a variable-orifice flow resistor with a high resistance to flow. Work increased up to threefold with the balloon valve and more than tenfold with the flow resistor compared with the threshold resistor. To apply CPAP, expiratory pressure valves with low resistance to flow should be used to minimize fluctuations in airway pressure and, thus, in the work of spontaneous breathing.

Humans↗
PubMed1987

Is 50% oxygen harmful?

Pulmonary gas exchange after tracheal extubation was evaluated in 25 patients to determine the effect of 50% oxygen administered during mechanical ventilation following aortocoronary bypass grafting. Twenty-five patients received postoperative mechanical ventilation for 16 to 24 h, 13 with an inspired oxygen fraction (FIO2) of no more than 0.30 and 12 with an FIO2 of 0.50. After tracheal extubation, all patients spontaneously breathed room air (FIO2 0.21). Postextubation the calculated venous admixture of patients who had received 50% oxygen (0.20 +/- 0.03 [SD]) was significantly (p less than .01) greater than that calculated for patients who received lower oxygen concentrations (0.13 +/- 0.04). Consequently, the PaO2 of patients who had received 50% oxygen (60 +/- 5 torr) was significantly (p less than .03) lower than the PaO2 of patients who had received no more than 30% oxygen (66 +/- 7 torr). Thus, administration of 50% oxygen, supposedly nontoxic, to mechanically ventilated patients may cause impairment of pulmonary gas exchange after tracheal extubation. Although high concentrations of supplemental oxygen are sometimes required, unnecessary elevation of FIO2 is not likely to significantly increase oxygen delivery and may contribute to postextubation pulmonary dysfunction.

Adult↗
PubMed1987

Modification of a critical care ventilator for anesthesia use.

Some critically ill patients require ventilatory support during surgery that exceeds the capabilities of most anesthesia ventilators. We modified an Emerson 3MV ventilator for anesthesia use and measured delivered concentrations of isoflurane during simulated ventilation of a test lung with oxygen flow rates ranging from 5 to 45 L/min. Each measurement was made at atmospheric pressure and incremental levels of 5, 10, 15, and 20 cm H2O PEEP. The delivered anesthetic concentrations were stable at oxygen flow rates of 12.5 to 20 L/min and were unaffected by PEEP changes.

Anesthesia, Inhalation↗
PubMed1985

Narcotics control in anesthesia training.

Recent studies document that substance abuse is a significant problem among anesthesia personnel. We have developed a system to better control the accountability of narcotics and other potentially addictive drugs. The system consists of a three-phase approach: (1) an individual anesthesia cart/narcotics box; (2) computer analysis of drug usage; and (3) an anesthesia drug audit. A standard stock issue of drugs is maintained by each resident. Drugs are issued daily to those residents administering anesthesia. Each drug transaction is recorded by the resident according to the patient's name, hospital number, type and length of the surgical procedure, type and amount of drug used, and the amount of each drug discarded. A weekly computer-generated report shows individual usage trends for each drug and a summary of "high" users for that period. The computer does not "flag" an individual as a drug abuser, but monitors trends in controlled substance usage. Those residents having a significant alteration in their drug usage pattern that is not explained legitimately are comprehensively audited.

Anesthesia Department, Hospital↗
PubMed1981

Methylmethacrylate seeks an appeal.

We measured hemodynamic and respiratory parameters before and after applying methylmethacrylate (MMC) to acetabular and femoral sites during neuroleptanesthesia and prosthetic hip surgery. No significant major changes were documented. Previously reported adverse effects probably have been due to medullary emboli, humoral responses, or a negative action of MMC on the cardiovascular system when used in conjunction with a potent inhalation anesthetic agent.

Adult↗