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Biomedical subjects

M J Tobin

Publications and source records attributed to M J Tobin.

At least 145 records · Page 8Linked to original sources
PubMed1986

Long-term prognosis of survivors of Pneumocystis carinii pneumonia. Structural and functional correlates.

Limited data exist detailing the long-term sequelae of Pneumocystis pneumonia. Open lung biopsies were obtained in seven renal transplant recipients within 48 hours of the onset of respiratory failure. Biopsy specimens and simultaneous chest roentgenograms were graded without clinical information according to the severity of alveolar damage and pulmonary infiltrates, respectively. Evaluation of pulmonary function and exercise physiology were performed 15 to 21 months after their illness. Pulmonary function indices were normal except FRC (2.65 +/- 0.56 L or 77 +/- 16 percent of predicted) and Dsb (20.0 +/- 7.2 ml/min/mm Hg or 79 +/- 19 percent of predicted). Two patients developed arterial desaturation with exercise. Alveolar damage scores correlated with later exercise arterial desaturation (r = 0.88, p less than 0.05). Simultaneous roentgenographic scores correlated with later abnormalities of Dsb (r = 0.81, p less than 0.05). Mild residual abnormalities of pulmonary function were found in five of seven adult survivors of Pneumocystis pneumonia. These abnormalities correlated with pathologic and radiographic features of the acute illness.

Adult↗
PubMed1985

Acute effects of aerosolized metaproterenol on breathing pattern of patients with symptomatic bronchial asthma.

We studied the effect of two sequential puffs of metaproterenol (650 micrograms each puff) delivered with an auxiliary aerosol delivery system on the breathing pattern of patients with symptomatic bronchial asthma who were monitored noninvasively with respiratory inductive plethysmography. Particular attention was directed to respiratory center drive as reflected by mean inspiratory flow and minute ventilation. Both these components were elevated in the eight patients whose mean FEV1.0 was 1.43 L (45% predicted normal). Two puffs of metaproterenol produced a maximal increase over baseline in FEV1.0 of 50 +/- 25% (SD), whereas no change took place in FEV1.0 with placebo administration. This dose of metaproterenol did not alter heart rate nor blood pressure throughout the study period of 2 hours. Neither mean inspiratory flow, minute ventilation, nor any component of the breathing pattern changed with this partial reversal of bronchoconstriction. These results suggest that the neural mechanism accounting for heightened respiratory center drive in patients with symptomatic bronchial asthma does not wholly depend on bronchoconstriction.

Adult↗
PubMed1985

Acute respiratory failure due to Pneumocystis carinii pneumonia: clinical, radiographic, and pathologic course.

The clinical, radiographic, and pathologic correlates of acute respiratory failure due to Pneumocystis carinii pneumonia were studied in 12 renal transplant patients treated with cyclosporin (CS) and prednisone. Six patients required only supplemental oxygen, while the other six patients developed the adult respiratory distress syndrome (ARDS) requiring prolonged mechanical ventilation despite similar predisposing factors and prompt initiation of therapy. Ten (83%) patients survived. Increased frequency of human leukocyte antigen (HLA) DR6 was noted in six of the 11 patients tested. The resolution of radiographic infiltrates was significantly slower in ARDS patients; however, there was no apparent difference in the severity of early alveolar damage between the two groups. There was also no association between the development of ARDS due to P. carinii pneumonia and the mean daily dose of CS and prednisone, the presence of cytomegalovirus infection or pneumonia, HLA-DR6 antigen, or initial hypoxemia.

Acute Disease↗
PubMed1985

Separation of factors responsible for change in breathing pattern induced by instrumentation.

Employment of mouthpiece and noseclips (MP + NC) has repeatedly been shown to increase tidal volume (VT), but its effect on respiratory frequency (f) and its subsets is controversial. The mechanisms accounting for this alteration in breathing pattern are poorly understood and may include stimulation of oral or nasal sensory receptors or alteration in the route of breathing. In this study we demonstrated that use of a MP + NC, compared with nonobtrusive measurement with a calibrated respiratory inductive plethysmograph, alters the majority of the volume and time indexes of breathing pattern, with increases in minute ventilation (P less than 0.01), VT (P less than 0.001), inspiratory time (TI, P less than 0.05), expiratory time (TE, P less than 0.05), mean inspiratory flow (P less than 0.05), and mean expiratory flow (P less than 0.05) and a decrease in f(P less than 0.05). Separating the potential mechanisms we found that when the respiratory route was not altered, independent oral stimulation (using an occluded MP) or nasal stimulation (by applying paper clips to the alae nasi) did not change the breathing pattern. In contrast, obligatory oral breathing without additional stimulation of the oral or nasal sensory receptors caused increases in VT (P less than 0.05), TI (P less than 0.05), and TE (P less than 0.01) and a fall in f(P less than 0.05). Heating and humidifying the inspired air did not prevent the alteration in breathing pattern with a MP. Thus change in the respiratory route is the major determinant of the alteration in breathing pattern with a MP + NC.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Subjective and objective measurement of tidal volume in critically ill patients.

Subjective assessment of the respiratory rate and the adequacy of tidal ventilation are the oldest and most widely practiced forms of respiratory monitoring in critically ill patients. Surprisingly, this method of assessment has itself never been evaluated in patients. The estimation of tidal volume in nine patients was performed by full-time intensive care unit (ICU) personnel and compared to the objective measurement of using a calibrated and validated respiratory inductive plethysmograph (RIP). Linear correlation analysis was performed. Poor correlation between clinical estimation by ICU personnel and actual measurement by RIP was revealed in all cases. A widespread and potentially dangerous tendency to overestimate tidal volume was noted. These data suggest that subjective assessment of tidal volume is inaccurate in critically ill patients and that the development of techniques of continuous, nonobtrusive and objective monitoring are to be encouraged.

Acute Disease↗
PubMed1985

Use of bronchodilator aerosols.

Despite initial fears associated with its safety, aerosol administration by metered dose inhaler (MDI) is rapidly becoming the preferred form of bronchodilator therapy, as it has a number of advantages over oral agents. To enhance aerosol delivery and bronchodilator response, several important steps in the optimal use of an MDI have been characterized. Because many physicians are unaware of the optimal technique in employing an MDI, it is not surprising that patients frequently receive little or no instructions in its use. Furthermore, patients who have received instruction display great difficulty in adhering to the steps in the ideal use of an MDI and frequently cannot coordinate MDI actuation with inspiration. A number of auxiliary delivery systems have recently been developed and show varying success in circumventing the problems involved in patient use of MDIs.

Aerosols↗
PubMed1984

Nosocomial lung infection and its diagnosis.

Nosocomial pneumonia occurs in 0.5% to 5.0% of all hospital admissions and is responsible for 15% of hospital deaths. Up to 60% of ICU patients may develop pneumonia, depending on the severity of their underlying disease. Despite the availability of potent antibiotics, ICU patients who develop Gram-negative pneumonia have a disturbingly high mortality rate. Specific etiologic diagnosis is frequently lacking because microbiological samples are commonly contaminated by oropharyngeal secretions which are colonized by Gram-negative bacilli (GNB) in up to 100% of ICU patients. Great controversy surrounds the value of various methods used to diagnose nosocomial pneumonia. Clinical criteria of pneumonia include fever, leukocytosis, purulent tracheobronchial secretions, and a new infiltrate on chest x-ray--all of which are also frequently observed in patients free of pneumonia. Tracheobronchial secretions are often contaminated by microorganisms colonizing the upper airways and their examination may provide misleading information and result in patient mismanagement. Blood cultures are valuable but positive in only a small proportion of patients with nosocomial pneumonia. Transtracheal and transthoracic aspiration are unsatisfactory in the intubated patient requiring mechanical ventilation. Immunologic techniques like countercurrent immunoelectrophoresis are promising but presently inadequate to screen for a wide variety of organisms. Transbronchial or open-lung biopsy may be considered if the pneumonia is thought to be due to opportunistic organisms rather than bacteria.(ABSTRACT TRUNCATED AT 250 WORDS)

Biopsy, Needle↗
PubMed1984

Cheyne-Stokes respiration revisited: controversies and implications.

Investigation of the periodic crescendo-decrescendo alterations in tidal volume in Cheyne-Stokes respiration (CSR) has provided remarkable insight into the physiology of respiratory control. Many patients with periodic breathing have both cardiac and neurologic disease. Considerable controversy has surrounded determination of the relative importance of cardiac and neurologic mechanisms in the genesis of this breathing abnormality. Several investigators have considered the respiratory center as a chemostat model with three basic components: the controller system (chemoreceptors), the controlled system (gas tensions of O2 and CO2), and the feedback loop (arterial circulation from the lung to the brain). If the relationship between these cardiac and neurologic components is altered, stability of the respiratory control system is lost. Such disturbance in the control system may arise by prolongation of the circulation time, or by the system becoming more dependent on its O2, rather than the CO2 component. Earlier investigators considered periodic breathing as a forewarning of ominous developments. In recent studies, mild degrees of periodic breathing, easily missed on physical examination, are often found in otherwise normal subjects, particularly during sleep. Generally no therapy is required, although aminophylline, O2 or CO2 administration has been shown to abolish periodic breathing.

Aged↗
PubMed1984

Effects of ipratropium bromide and fenoterol aerosols on exercise tolerance.

Twelve male patients with radiological evidence of pulmonary emphysema performed progressive exercise tests on a cycle ergometer. Ipratropium bromide (Ip) 40 micrograms, Fenoterol (Fen) 400 micrograms, their combination (Ip/Fen) and Placebo were administered from metered-dose inhalers in a double-blind crossover study to compare the effects on ventilation (VE), heart rate (fc) and oxygen uptake (VO2) at rest and at maximal and sub-maximal workloads. There were no significant differences in resting VE (p greater than 0.05) between the 4 treatment regimes. During submaximal exercise, VE at a given workload was greater after Fen containing treatment regimes than after Ip alone or placebo. There was no significant difference in the maximal workload achieved after the active treatments compared with placebo. With respect to fc and VO2, there were no differences between treatments at rest or on submaximal or maximal exercise. Fenoterol produces a mild stimulation of VE during exercise as observed with other beta-agonists, but compared with the changes in resting vital capacity, functional residual capacity and residual volume, the bronchodilator induced changes in exercise variables were relatively small.

Aged↗
PubMed1983

Alpha 1 antitrypsin deficiency: the clinical and physiological features of pulmonary emphysema in subjects homozygous for Pi type Z. A survey by the British Thoracic Association.

Hereditary deficiency of alpha 1 antitrypsin, the main serum inhibitor of proteolytic enzymes is associated with pulmonary emphysema of early onset. A multicentre survey of this disorder was started in 1976 and details of 166 subjects homozygous for the Z phenotype form the main body of this report. There were 126 index cases who were identified through chest clinics and 40 non-index cases who were identified through family studies. The index cases and many of the non-index cases had severe radiological and physiological abnormalities. A history of cigarette smoking had a significant effect upon the prognosis, but sex and occupational exposure to dust or fumes did not. There was a wide variance in lung function even among those who had never smoked.

Adult↗
PubMed1983

Alpha 1 antitrypsin deficiency: clinical and physiological features in heterozygotes of Pi type SZ. A survey by the British Thoracic Association.

In a multicentre survey of alpha 1 antitrypsin deficiency 25 heterozygotes of type SZ were identified. Fourteen index cases were identified through chest clinics and 11 non-index cases through family studies. Emphysema was largely confined to index males who had smoked and there was little evidence of the disease among the non-index cases. It appears that the SZ phenotype may carry little or no extra risk of emphysema.

Adult↗
PubMed1983

Bacteriophage concentration from water by filter chromatography.

The efficiency of an electropositive filter for membrane chromatography of viruses was examined using coliform phages T1, T4, lambda and Salmonella phage P22. Phages diluted in dechlorinated tap water were adsorbed to filters at neutral pH and eluted by 3% beef extract in 0.05 M glycine buffer at selected alkaline pH values. With exception of lambda phage, which displayed erratic adsorption behavior at any pH, all bacteriophages studied, adsorbed to filters with an efficiency of 97-100% at pH values ranging between 6.0 and 8.0. Each phage was readily eluted at alkaline pH levels. Maximal elution (86.2%) of T1 phage and lambda phage (79%) occurred at pH 10, while T4 and Salmonella phages were eluted most efficiently at pH 11 at values of 91.7 and 81.9%, respectively. The resolving power of the filter was such that individual phages within the same virus group (T1 and T4 phage) could be eluted at pHs differing by only one unit.

Adsorption↗
PubMed1983

Effect of positive end-expiratory pressure on breathing patterns of normal subjects and intubated patients with respiratory failure.

The aims of this study included assessment of accuracy of respiratory inductive plethysmography when pulmonary hyperinflation was induced by application of PEEP, and examination of breathing patterns of normal subjects, intubated patients requiring mechanical ventilation and intubated patients immediately before extubation during application of PEEP by demand valve and high gas flow reservoir bag systems. Validation of tidal volume (VT) and end-expiratory level measured with respiratory inductive plethysmography to simultaneous spirometry (SP) was achieved with PEEP levels up to 12.5 cm H2O in 7 normals. In 17 intubated patients, almost all VT values measured with respiratory inductive plethysmography fell within +/- 10% of SP even with 2 to 3 changes of body posture. In normal subjects, increasing levels of PEEP from the demand valve system produced nonprogressive rises of VT and mean inspiratory flow, falls of frequency and fractional inspiratory time (TI/TTOT), and no changes of minute ventilation (Vmin) nor mean expiratory flow. PEEP from the high gas flow reservoir bag system produced nonprogressive rises of VT and rib cage (RC) contribution to VT, and rises of Vmin and mean inspiratory and expiratory flows between 10.0 and 12.5 cm H2O of PEEP. Intubated patients requiring intermittent mandatory ventilation (IMV) had a rapid, shallow breathing pattern unaltered by PEEP levels delivered by either system up to 12.5 cm H2O despite increases of end-expiratory level. Intubated patients who were about to be extubated breathed with patterns closer to ambulatory normal subjects with the exception of their elevated RC contribution to VT.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

Effect of naloxone on breathing pattern in patients with chronic obstructive pulmonary disease with and without hypercapnia.

Recent reports suggest that endogenously released endorphins may exert a modifying influence on respiratory center drive in patients with respiratory disease. In this report, we employed respiratory inductive plethysmography to noninvasively assess breathing patterns with particular attention to respiratory center drive as reflected by mean inspiratory flow. We studied 10 patients with documented chronic obstructive pulmonary disease (6 with hypercapnia and 4 with normocapnia) after treatment with placebo and the opiate antagonist, naloxone. No significant change in breathing pattern was observed in either patient group after treatment with placebo or naloxone, although individual patients displayed greater respiratory drive after naloxone than placebo. Therefore, endorphins do not exert a consistent influence on respiratory center output in patients with chronic obstructive pulmonary disease.

Aged↗
PubMed1983

Validation of respiratory inductive plethysmography in patients with pulmonary disease.

The assumption that the respiratory system behaves with 2 df of motion in healthy persons allows calibration of respiratory inductive plethysmography (RIP) with spirometry (SP). To ascertain whether RIP could be calibrated by the same assumption in patients with lung disease, even though at least 3 df of motion are visualized (ie, upper and lower rib cage and upper and lower abdomen move out of phase), RIP was calibrated by a two-position calibration procedure and validated satisfactorily by simultaneous SP in the erect, semirecumbent, supine, and lateral decubitus positions. In lung disease, the contribution to tidal volume of regions moving independently of the combined rib cage and abdominal movements either is small or remains relatively constant with change of body posture. For clinical monitoring of the resting breathing pattern where patient movements cannot be restricted, respiratory inductive plethysmography can serve as a reliable semiquantitative, noninvasive ventilatory monitoring device.

Abdomen↗
PubMed1983

Breathing patterns. 1. Normal subjects.

Ventilatory monitoring devices that require mouthpiece breathing produce a rise in tidal volume (VT), a fall in frequency (f) and alterations in periodicity and variability of breathing components. Together with the introduction of the respiratory inductive plethysmograph, a reliable noninvasive monitoring device of ventilation, major advances have taken place in understanding the significance of the components of the breathing pattern. We measured the breathing pattern of normal subjects utilizing respiratory inductive plethysmography and continuously processed these data with a microprocessor system. The mean values of the breathing pattern components in normal subjects were not affected by age, but the rhythmicity was more irregular in the elderly. The values of breathing pattern components obtained noninvasively by respiratory inductive plethysmography in normal subjects are fairly predictable in limits similar to other tests of pulmonary function.

Adult↗
PubMed1983

Breathing patterns. 2. Diseased subjects.

We measured the breathing pattern of normal subjects, asymptomatic smokers, asymptomatic and symptomatic asthmatic patients, and patients with chronic obstructive pulmonary disease, restrictive lung disease, primary pulmonary hypertension and anxiety state utilizing respiratory inductive plethysmography. Respiratory rate was increased above the normal in smokers and in patients with COPD, restrictive lung disease and pulmonary hypertension, but remained normal in asthmatic patients. Inspiratory times (T1) of one second or less often occurred in patients with COPD, restrictive lung disease, and pulmonary hypertension. Smokers and patients with symptomatic asthma, COPD, restrictive lung disease and pulmonary hypertension showed heightened respiratory center drive as reflected by elevated mean inspiratory flow (VT/TI). Fractional inspiratory time was reduced to a variable extent in smokers, symptomatic asthmatic patients and patients with COPD, and was a weak indicator of airways obstruction. Patients with COPD often had major fluctuations of expiratory timing, periodic fluctuations of end-expiratory level, and asynchrony between rib cage and abdominal movements. Chronic anxiety was characterized by frequent sighs; episodic rapid rates alternating with apneas were less common. We conclude that analysis of breathing patterns provides diagnostic discrimination among normal subjects and disease states.

Adult↗