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Biomedical subjects

A S Rebuck

Publications and source records attributed to A S Rebuck.

At least 109 records · Page 6Linked to original sources
PubMed1982

Effect of breathing pattern on oxygen concentration received from standard face masks.

Standard face masks are widely used for patients who require high oxygen concentrations. A mechanical model was designed to reproduce various respiratory manoeuvres while oxygen was delivered through a standard variable-performance face mask. Over a range of tidal volumes from 300 to 1200 ml and of frequencies from 10 to 30 breaths/min, the received oxygen concentration was lower than the delivered concentration. The disparity between delivered and received oxygen increased with increasing rate and depth of simulated breathing but could be reduced by increasing the flow rate up to 60 l/min. When a turbulent environment was created, the difference between delivered and received oxygen concentrations was exaggerated. Disparities between delivered and received concentrations can be lessened by increasing the flow rate.

Humans↗
PubMed1982

Proportional analysis of respiratory cells obtained by bronchoalveolar lavage.

Bronchoalveolar lavage was performed during fibreoptic bronchoscopy in 17 patients with biopsy-proven interstitial lung disease and in 12 control subjects who had focal lesions in the lung. The volume of fluid recovered was unrelated to disease activity or diagnosis. In the control subjects alveolar macrophages represented over 95% of the lavaged cells. The proportion of lymphocytes in the lavaged cells enabled a natural division of the diffuse interstitial lung diseases into two categories: active sarcoidosis, indicated by a large proportion of lymphocytes but a normal proportion of polymorphonuclear leukocytes; and idiopathic pulmonary fibrosis and asbestosis, indicated by a normal proportion of lymphocytes but a variable proportion of polymorphonuclear leukocytes. Bronchoalveolar lavage is a safe and well tolerated method for evaluating the role of alveolitis in diffuse interstitial lung disease through the sampling of respiratory alveolar cells.

Adult↗
PubMed1982

Arterial PCO2 as an index of activity in fibrosing alveolitis.

Alveolar hyperventilation is a characteristic feature of the interstitial lung diseases, yet its pathogenesis remains unknown. We examined the relationship between inflammatory alveolar acinar cell counts and the steady state, resting arterial PCO2 in patients with fibrosing alveolitis. To eliminate the influence of overwhelming mechanical lung restriction or resting hypoxemia, we studied 20 patients who, despite having clinicopathologically confirmed fibrosing alveolitis, had vital capacities exceeding 50 percent of predicted, and arterial O2 saturations above 90 percent. There was a significant inverse relationship between the proportion of polymorphonuclear leukocytes (PMNs) in the recovered BAL fluid and the arterial PCO2 (r = -0.67; p less than 0.01). When PCO2 was above 35 mm Hg, the BAL PMN count was 8 percent or less (mean = 3.4; SD = 2.5), while the mean BAL PMN count among those patients whose PCO2 was less than 35 mm Hg was significantly higher (mean = 11.7; SD = 3.7; p less than 0.01). PCO2 levels were unrelated to arterial O2 saturation or PaO2. No relationship was found between the PCO2 and BAL lymphocyte counts. The findings suggest that in fibrosing alveolitis, the arterial PCO2 may be used as an indicator of the state of the inflammatory component of the alveolitis.

Carbon Dioxide↗
PubMed1982

Pulmonary disposition of cortisol.

High-dose corticosteroid therapy is used in various lung diseases, yet it is not known if the drug enters the alveolar acinus. Cortisol levels, expressed as a function of albumin concentration, were measured in serum and bronchoalveolar lavage fluid in 12 patients with lung disease. There was a linear relation of cortisol concentration between blood level and bronchoalveolar lavage fluid level when expressed in relation to the albumin concentration (r = 0.93, p less than 0.001). Incremental doses of intravenous hydrocortisone reach alveolar structures in a concentration directly related to the circulating blood levels.

Adult↗
PubMed1982

Pulmonary disposition of gallium-67 in humans: concise communication.

Pulmonary gallium-67 imaging for inflammatory and neoplastic diseases has become an important diagnostic tool in respiratory medicine. However, the extent to which Ga-67 is delivered to normal lungs has not been fully evaluated. Accordingly, we measured the disposition of Ga-67 using scintiscanning, bronchoalveolar lavage (BAL), and blood analysis in healthy subjects. Following an intravenous dose of 6 mCi Ga-67 citrate, the gallium scan showed no pulmonary uptake at 48 hr. In all subjects, radioactivity was detected in both blood and recovered BAL fluid at 72 hr, being predominantly in the cellular component of the BAL washings. We conclude that despite negative pulmonary imaging, Ga-67 accumulates in the cells that line the alveolar acini of normal nonsmoking individuals.

Adult↗
PubMed1982

Intramuscular and intravenous albuterol in the treatment of asthma.

The efficacy and side effects of intravenous and intramuscular albuterol were determined in 13 adult asthmatic patients whose airway responsiveness had previously been evaluated with inhaled albuterol. In each patient, a single dose of intramuscular or intravenous albuterol was given at the same time on separate days. There was no significant difference in bronchodilator effect between the two routes of administration; both were effective. By 15 minutes after injection, both had produced an increase in FEV1 (mean, 0.32 liter), but both were associated with transient increases in heart rate (mean, 8 beats/min, P less than 0.01). It is concluded that minimal cardiovascular side effects can be achieved with either parenteral form of albuterol.

Adult↗
PubMed1981

Transcutaneous carbon dioxide monitoring.

We studied changes in transcutaneous PCO2 in healthy volunteers and patients to establish the accuracy and practicability of a new cutaneous capnometer (HP47201A). In 9 healthy volunteers, as many as 4 experiments each were performed during each laboratory session. After cutaneous electrode stabilization, a gas mixture of CO2 in O2 was rebreathed under "open-loop" conditions allowing a rapid progressive increase in alveolar PCO2. The electrode stabilized on the skin with a time constant of 2.87 +/- 0.72 min. During rebreathing, alveolar PCO2 increased 4.25 +/- 0.63mm Hg/min. The simultaneous rate of increase in transcutaneous PCO2 was 2.91 +/- 0.59 mm Hg of CO2/min. Electrode response was also studied during steady-state conditions after a step increase in alveolar PCO2 of 10 mm Hg more than the resting end-tidal PCO2. The time constant of the skin electrode's response under these conditions was 3.2 +/- 1.9 min. We compared the arterial PCO2 of 25 blood samples with simultaneous transcutaneous PCO2 measurements in hemodynamically and metabolically stable patients. The range of arterial PCO2 values varied between 24 and 98 mm Hg, and the electrode remained stable during each 12-h study. Observed values closely approximated arterial PCO2 measurements, with transcutaneous readings 4 mm Hg more than measured arterial values (r = 0.98). We conclude that the cutaneous capnometer accurately and consistently reflects arterial PCO2 and has delay and response characteristics that may allow its use in clinical monitoring of patients.

Adult↗
PubMed1981

A simplified breath-holding method for measuring oxygenated mixed venous carbon dioxide pressure.

We have attempted to simplify the breath-holding method for measuring mixed venous PCO2 by the use of a single breath of 100% O2. This method is based on analysis of partial pressures of CO2 in three samples of alveolar gas obtained at 5, 10, and 15 sec of breath-holding after inspiration of 100% oxygen. Assuming exponential build-up of CO2 in alveolar gas, oxygenated mixed venous PCO2 can then be determined. Results in 35 subjects were compared with those of the previously reported breath-holding method for estimating oxygenated mixed venous PCO2 based on inspiring two gas mixtures; correlation coefficient was found to be 0.92. In 17 patients, samples of blood were obtained from the pulmonary artery by percutaneous catheterization; measured values in blood correlated well with the oxygenated non-invasively determined values (r = 0.83).

Blood Gas Analysis↗
PubMed1980

The effect of posture on the ventilatory response to hypoxia.

The ventilatory response to carbon dioxide is known to be uninfluenced by changes in posture. To obtain similar data on the ventilatory response to hypoxia we studied seven subjects in each of two postures, lying and sitting, at a constant PCO2 midway between end-tidal and mixed venous. Minute ventilation was higher in the seated position than supine (p < 0.01) at this isocapnic level, attributable mainly to an increase in tidal volume (p < 0.05). However, there were no statistically significant differences in the ventilatory response, the tidal volume response, or the frequency response to hypoxia between the two postures.

Adult↗
PubMed1980

Determination of cardiac output based on breath-holding.

A breath-holding method for determination of cardiac output is described. It is based on the indirect Fick principle applied to carbon dioxide. Mixed venous PCO2 (PvCO2) is measured noninvasively using a CO2 breath-holding technique and PaCO2 is obtained by arterial puncture. Partial pressures are converted into contents using each patient's CO2 dissociation curve, taking into account temperature, hemoglobin, arterial and venous pH. The authors have applied this method to the determination of cardiac output in 20 patients, in whom cardiac output was also measured invasively using either direct Fick or thermodilution method. Mean cardiac output determined using the breath-holding method was 5.48 +/- 2.95 (SD) L/min, compared to 5.54 +/- 2.88 L/min as determined by the direct Fick or thermodilution method. Good correlation was found between the invasive and breath-holding method (r = 0.97, p < 0.001). The authors conclude that cardiac output at rest may be estimated with considerable accuracy from the measurements of PaCO2, CO2 production and the breath-holding mixed venous PCO2 without right-sided cardiac catheterization.

Arteries↗
PubMed1980

The hypoxic ventilatory response in patients with high-affinity hemoglobin.

In an attempt to determine whether PO2 or O2 saturation is stimulus for the hypoxic ventilatory drive, we studied 2 brothers with the high O2 affinity hemoglobin Ranier (P50 approximately equal to 12 mm Hg). The ventilatory response to PO2 was normal. The O2 saturation did decrease slightly, and the ventilatory response to the decrease in O2 saturation was greatly exaggerated. We conclude that these findings are consistent with either of 2 possibilities: (1) that PO2 provides the stimulus to the hypoxic ventilatory response, or (2) that patients with high-affinity hemoglobin have increased sensitivity to arterial O2 desaturation.

Adult↗
PubMed1980

Human lung transplantation.

The 38th attempt at allotransplantation of a human lung is described in a patient with injury due to smoke inhalation. The innovative features in the procedure included prolonged support with an extracorporeal membrane oxygenator during and for four days following transplantation, pharmacologic control of platelet function with sulfinpyrazone, continuous monitoring with a fiberoptic ear oximeter, and pretreatment of the transplanted lung with cytotoxic durgs. The patient survived until the 18th postoperative day, with no evidence of tissue rejection, but he died following ischemic disruption of the bronchial anastomosis. We conclude that the major determinant in the future of human lung transplantation is related to the establishment of a bronchial arterial supply to the transplanted bronchus.

Adolescent↗