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Biomedical subjects

H M Marsh

Publications and source records attributed to H M Marsh.

51 records · Page 3Linked to original sources
PubMed1981

The effect on heart rate of neuromuscular blockade reversal by pyridostigmine.

Pyridostigmine without atropine, pyridostigmine with atropine or neostigmine with atropine were used to antagonise neuro-muscular blockade induced by d-tubocurarine in forty otherwise healthy, female patients recovering from gynaecological surgery. Pulse rates fell significantly (P less than 0.01, control heart rate 72 +/- 18 beats/min (M +/- SD) to 55 +/- 13 beats/min) at ten minutes after pyridostigmine (10 mg/70 kg), necessitating administration of atropine (1.25 mg/70 kg) by fifteen minutes after pyridostigmine. After an initial rise in rate, pulse rates also fell significantly (P less than 0.01, control heart rate 70 +/- 12 beats/min to 44 +/- 11 beats/min) at fifteen minutes after injection of neostigmine (2.5 mg/70 kg) with atropine (1.25 mg/70 kg). By contrast when pyridostigmine and atropine were used together, pulse rates rose and then fell, but mean values never fell below control during a twenty-minute observation period. It was concluded that pyridostigmine should not be given alone, but requires the use of atropine to prevent bradycardia. This combination may, however, provide a more stable heart rate than that seen with neostigmine and atropine in usual doses, when these drugs are used to antagonise d-tubocurarine.

Adolescent↗
PubMed1979

Electrophrenic respiration: report of six cases.

The development of electrophrenic respiration has permitted freedom from mechanical ventilation for patients who have irreversible respiratory failure in association with high-cervical spinal cord or brainstem lesions. There are three basic criteria for successful diaphragm pacing: (1) the need for long-term mechanical ventilatory assistance, (2) a functionally intact phrenic nerve-diaphragm axis, and (3) chest wall stability. Inability to achieve satisfactory pacing can be due to malfunction of equipment, instability of the chest wall, or inadequate neuromuscular responsiveness. These features of diaphragm pacing are exemplified in a series of six patients. Three achieved independence from mechanical ventilatory assistance with full-time phrenic pacing. In one patient, only limited electrophrenic respiration was achieved, and in another the method was entirely unsuccessful. Although functioning well, pacing systems were removed from the sixth patient because of infection. Diaphragm pacing can be a valuable form of respiratory support for carefully selected patients.

Adolescent↗
PubMed1979

Measurement of ventilatory reserve as an indicator for early extubation after cardiac operation.

The decision to perform tracheal extubation in 44 patients who underwent cardiac operation was based on an assessment of mental alertness, recovery of muscle strength, hemodynamic stability, and adequacy of pulmonary gas exchange. No patients required reintubation. Concomitant measurements of vital capacity (VC) and maximal inspiratory pressure (PImax) were made before a trial of spontaneous ventilation was commenced, after 45 minutes of spontaneous ventilation, and after tracheal extubation. By generally accepted criteria, these measurements suggested the need for continuing mechanical ventilation in 14 patients at the time mechanical ventilatory support was removed and in eight patients at the time of tracheal extubation. In this study, consideration of measurements of VC and PImax would have led to longer trachael intubation, especially in those patients who were extubated within 10 hours of the completion of anesthesia.

Anesthesia, General↗
PubMed1978

Closing capacity in awake and anesthetized-paralyzed man.

Functional residual capacity (FRC), closing capacity (CC), and (FRC--CC) were determined in 61 supine patients using the 133Xe bolus test. In 28 of the 61 patients measurements were made both while the patients were awake and during anesthesia-paralysis. Both FRC and CC decreased significantly after induction of anesthesia-paralysis. The magnitude of the reduction in CC, but not of FRC, was dependent on the relationship between FRC and CC in the awake state. Patients whose FRC was larger than their CC while awake (group I) showed less decrease in CC than FRC, i.e., (FRC--CC) decreased. By contrast, those patients whose CC was larger than their FRC while awake (group II) showed a greater decrease in CC than in FRC, i.e., (FRC--CC) became less negative. The reduction in CC after induction of anesthesia-paralysis may result from an increased elastic recoil of the lung. The larger reduction in CC in group II patients may have been due to a larger increase in elastic recoil, possibly due to the development of atelactasis.

Adult↗
PubMed1977

Airway closure.

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Adolescent↗
PubMed1977

The effects of anesthetic drugs and disease on the chemical regulation of ventilation.

The anesthesiologist uses a wide spectrum of drugs, including inhalational general anesthetics, barbiturates, benzodiazepines, narcotics analgesics and their antagonists, and neuromuscular blocking drugs. All of these drugs in sufficient dose impair the ventilatory response to chemical stimuli, and may cause inadequate gas exchange. The effect of depression of ventilatory control depends on the magnitude of depression and the coexistence of functional abnormalities in the respiratory system. The functional abnormalities are the result of preexistent pulmonary disease or other disease processes that impair respiratory function, the anticipated effects of major surgery (e.g., pulmonary resection), and the complications of anesthesia and surgery. From a functional viewpoint, the mechanisms of the effects of these disease processes on ventilatory control are: (1) interference with the neurophysiological control of automatic ventilation; (2) impairment of peripheral or central chemoreceptor function; (3) impairment of respiratory muscle function; (4) increase in the mechanical load to breathing as a result of increased resistance or decreased compliance of the respiratory system; and (5) increase in the ventilatory requirements as a result of ventilation/blood flow maldistribution, metabolic acidosis, or increased metabolic rate. As a result of current trends in the use of multiple drugs and controlled ventilation during anesthesia, the patient is at greatest risk during the early postoperative period in the recovery room. In addition to the functional abnormalities described above, the probability of impaired gas exchange and respiratory failure is increased as a result of impaired metabolism and elimination of drugs as a result of hepatic and renal insufficiency, and acute changes in acidbase status, which alter the ionization and distribution of drugs.

Anesthetics↗
PubMed1977

Improved oxygenation in patients with acute respiratory failure: the prone position.

To assess the potential benefits of the prone position for gas exchange in patients with acute respiratory failure, we turned 6 patients from supine to prone, supporting the upper thorax and pelvis and allowing the abdomen to protrude. Arterial PO2 increased by a mean of 69 mm Hg (range, 2 to 178 mm Hg) at the same tidal volume, same inspired oxygen concentration, and same level of positive end-expiratory pressure. The maneuver made it possible to reduce the inspired oxygen concentration in 4 of the 5 patients who required mechanical ventilation of the lungs and to defer intubation in the patient who was breathing spontaneously. After subsequent turns from supine to prone, arterial PO2 increased by a mean of 35 mm Hg (range, 4 to 110 mm Hg), permitting a decrease in inspired oxygen concentration or positive end-expiratory pressure when prone (4 patients); arterial PO2 decreased in 12 of 14 instances after the patient was turned from prone to supine. No significant change in mean arterial carbon dioxide tension, respiratory frequency, or effective compliance was observed.

Acute Disease↗
PubMed1977

New tests for the detection of obstructive pulmonary disease.

Abnormalities in small airways appear to be important in the evolution of chronic obstructive pulmonary disease. Patients with these pathologic lesions may have normal values for airway resistance and forced expiratory volume in one second. Two new tests, the closing volume (CV) and the dependence of maximal flow on density, are believed to be sensitive to abnormalities in the peripheral airways. The CV test detects an increased nonuniformity of changes in volume of pulmonary units. Reduced dependence of flow on density is believed to result from an increase in the peripheral component of the losses of driving pressure which determine maximal expiratory flow. Both tests differentiate smokers with normal conventional spirometric data from age-matched nonsmokers. Although this evidence suggests that these tests can be used to detect abnormalities in small airways, there is very little pathologic confirmation of this belief. The clinical significance of abnormalities in the results of either of these tests in an otherwise normal person has not yet been determined.

Airway Resistance↗
PubMed1975

General anesthesia and the lung.

In this review, an attempt has been made to select, evaluate, and interpret the pertinent literature relative to general anesthesia and the lung. Concepts of intrapulmonary gas exchange and respiratory system mechanics were synthesized, emphasizing the importance of changes in intrapulmonary gas distribution that are induced by general anesthesia and exploring the possible underlying mechanisms of these changes. The area of control mechanisms and the effects of anesthesia on respiratory regulation were not discussed, nor was the distribution of pulmonary blood flow examined. The following general conclusions can be reached: (1) impaired gas exchange occurs during general anesthesia, with both impaired oxygenation and CO2 elimination; (2) increased venous admixture and increased alveolar dead space impair gas exchange; (3) the distribution of ventilation is changed during general anesthesia, and this change is related to a decrease in FRC in the recumbent positions and to altered chest-wall mechanics. Numerous questions regarding the effect of anesthesia on the lung remain unanswered. The close relationship between advances in pulmonary physiology and the pulmonary effects of anesthetic actions is increasingly apparent, as is the importance of this knowledge in applying mechanical ventilation and end-expiratory pressure to patients with pulmonary disease.

Airway Resistance↗