PubMed Health⌕ Search

Biomedical subjects

F J Colgan

Publications and source records attributed to F J Colgan.

At least 19 recordsLinked to original sources
PubMed1983

Ventilation requirements during high frequency ventilation.

This study was undertaken to investigate ventilatory requirements during high frequency ventilation (HFV). Six anesthetized dogs were ventilated with bird M-2 or Emerson 2-V ventilators at respiratory rates (RRs) ranging from 13-1300 breath/min. PaCO2 was maintained within normal range at all rates by tidal volume (VT) adjustment. Required minute volume (VE) increased linearly with rate while VT decreased exponentially and approached a plateau at rates above 200. Airway pressure was inversely proportional to rate at rates below 80 but increased with rate thereafter. A method is provided to estimate required ventilatory volume during HFV based on the results of this study. It was concluded that gas exchange during HFV can be explained by conventional concepts of ventilation and with an unvented nonrebreathing system no benefit accrues from respiratory rates above 200 inasmuch as neither airway pressure nor VT can be reduced in the face of increasing VE requirements.

Animals↗
PubMed1983

Protective effects of beta blockade on pulmonary function when intracranial pressure is elevated.

Intracranial pressure (ICP) was increased by hyperosmolar intracerebral infusion in dogs and the cardiopulmonary and catecholamine (CA) responses followed for 4 h. Increased ICP evoked persistent increases in endogenous CAs, pulmonary vascular pressures, pulmonary blood volume, and venous admixture. Other dogs similarly monitored were treated with a beta-blocking dose of propranolol 25 min after the onset of increased ICP. Although catecholamines were increased, elevated pulmonary pressures and venous admixture returned to control levels. CO and heart rate (HR) were reduced after beta blockade but systemic vascular resistance increased. It was concluded that increased ICP induces sustained increases in CAs which adversely affect pulmonary pressures and shunting. Selective beta blockade reverses these effects and may be useful in patients with evidence of sympathetic overactivity and progressive hypoxemia after head injury.

Animals↗
PubMed1979

PEEP and CPAP following open-heart surgery in infants and children.

The cardiorespiratory effects of 5 cm H2O end-expiratory pressure were studied in 22 infants and children an hour after open-heart surgery during mechanical ventilation with positive end-expiratory pressure (PEEP) and prior to endotracheal extubation approximately 15 hours later during spontaneous breathing (CPAP). Thermodilution cardiac output determinations and respiratory airflow, volume and pressure recordings were made to assess the effects of airway pressure changes on the respiratory waveform and oxygen delivery. Neither PEEP nor CPAP had a significant effect on cardiac output, intrapulmonary shunting, oxygen consumption, or oxygen utilization. Patients who had had pulmonary hypertension preoperatively did not behave differently from those without pulmonary hypertension when removed from ventilatory supprot. Expiratory airflow was significantly prolonged when positive end-expiratory pressure existed during both controlled and spontaneous respiration. During CPAP, this "expiratory braking" was associated with an increase in tidal volume and decreases in respiratory rate and minute volume. Because of the lack of improvement in cardiopulmonary function in this group of patients, and the possibility of untoward effects from sustained end-expiratory pressure, PEEP and CPAP might properly be reserved as temporary supportive techniques should respiratory function be compromised.

Cardiac Output↗
PubMedDate not supplied

An assessment of cardiac output by thermodilution in infants and children following cardiac surgery.

A 4 F thermodilution catheter for measuring cardiac output was evaluated for accuracy and linearity in the laboratory and by comparison with the dye dilution method in infants and children following cardiac surgery. When 2 ml of 0 degrees C injectate were used, the correlation of computer determined flows to calibrated pump flows, over a range encountered clinically, was r = 0.998. The means of triplicate determinations by both the thermal and dye methods were compared in 8 of 25 patients and the comparison found to be favorable (r = 0.976). The complications of thermodilution catheter placement are described and related to the need for post-surgical chest x-ray and thermodilution recordings. The simplicity of the thermodilution technique and other advantages over the dye method in children, such as repeatability, and ease of calibration are discussed in relation to the increased flexibility in management which accrues.

Cardiac Catheterization↗
PubMedDate not supplied

Nonivasive assessment by capacitance respirometry of respiration before and after extubation.

Respiration before and after extubation was studied in postoperative patients following weaning from respirator support. Changes in tidal and minute volume and respiratory flow rates were determined by capacitance respirometry, a noninvasive method of monitoring respiration. The presence of an endotracheal tube of 7.5 to 8.5 mm ID had no significant effect on ventilation, respiratory flow rates, or intrapulmonary shunting. Laboratory and clinical evidence showed that in postoperative patients, an endotracheal tube of 8 mm ID substitutes a relatively low, predictable resistance for a potentially excessive and variable upper airway resistance.

Cardiac Surgical Procedures↗