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Biomedical subjects

B E Pennock

Publications and source records attributed to B E Pennock.

At least 19 recordsLinked to original sources
PubMed1992

Descriptive ventilatory mechanics from noninvasive analog display of ribcage and abdominal flow.

A rapidly responding analog display of ventilatory flow at the mouth, ribcage and abdomen allows interpretation of the relative activity of the diaphragm, accessory inspiratory muscles and abdominal expiratory muscles. These relative movements are exaggerated by having volunteers perform the ventilatory maneuvers of sniff, rapid exhalation and cough. Activity and regional lung flow can change in time periods in the tens of milliseconds. These rapid (within an inspiratory or expiratory time) relational changes in respiratory muscle activity and regional lung flow have not previously been demonstrated with a simple noninvasive measurement.

Abdomen↗
PubMed1991

Pressure support ventilation with a simplified ventilatory support system administered with a nasal mask in patients with respiratory failure.

Thirty-one consecutive patients with respiratory failure in whom treatment with intubation and mechanical ventilation was being strongly considered received alternative ventilatory support by means of a BiPAP ventilatory support system and nasal mask. Laboratory measurements and physical findings were documented before and 1 h after initiation of support. This support improved patient comfort, slowed respiratory rate, and improved oxygenation. Support lasted from 2 h to six days. Seventy-six percent (22/29) of patients recovered from this episode of respiratory failure, avoiding alternative mechanical ventilatory support. There were no complications associated with aspiration, gastric distention, or acute separation from support.

Aged↗
PubMed1990

Rib cage and abdominal piezoelectric film belts to measure ventilatory airflow.

Piezoelectric film-based respiratory belts are described and tested. To the extent that a two-degree of freedom model consisting of rib cage and abdominal motion is able to assist in quantifying ventilation, the piezoelectric belts can monitor flow in a manner analogous to the monitoring of volume with two magnetometer pairs or two respiratory inductive plethysmograph belts. The piezoelectric belts are shown to measure flow linearly when compared with a screen pneumotachometer to a flow of at least 2.6 L/s. There is no phase shift between the peak flow of belts and the pneumotachometer up to a frequency of at least 9.2 Hz. During normal ventilation, 68 and 95% of the peak flows measured with the belts fall within +/- 10 and 20%, respectively, of the flows measured with a screen pneumotachometer.

Abdomen↗
PubMed1989

Oxygen consumption of the respiratory muscles in normal and in malnourished patients with chronic obstructive pulmonary disease.

Patients with severe chronic obstructive pulmonary disease (COPD) commonly experience weight loss. An increased energy expenditure for respiration might explain the increased caloric requirements and weight loss seen in this patient population. We measured the oxygen cost of augmenting ventilation (O2 cost) using an open circuit technique with dead-space stimulation of ventilation in nine normally nourished (greater than 90% ideal body weight) and in 10 malnourished (less than 90% ideal body weight) patients with COPD as well as in seven normal control subjects. O2 cost was significantly elevated in the malnourished patients with COPD (4.28 +/- 0.98 ml O2/L ventilation) relative to the normally nourished group (2.61 +/- 1.07) and the normal control subjects (1.23 +/- 0.51) (p less than 0.001). The measured resting energy expenditure (REEmeas) was also increased compared with predicted values (REEpred) in the malnourished population (REEmeas/REEpred = 94.57 +/- 6.21% for control subjects, 105.5 +/- 19.66% for normally nourished patients with COPD, and 119.4 +/- 11.69% for malnourished patients with COPD) (p less than 0.005). The malnourished population was characterized by a greater degree of hyperinflation (RV/TLC = 0.55 +/- 0.09 for normally nourished versus 0.69 +/- 0.06 for malnourished patients) and inspiratory muscle weakness (PImax = 51 +/- 16.5 for the normally nourished and 34 +/- 12.2 for the malnourished population). We conclude that malnourished patients with COPD are characterized by a relative increase in resting energy requirements and, specifically, increased energy requirements for augmenting ventilation. This increase in energy requirements may result from the increased mechanical work load associated with severe COPD and/or a reduced ventilatory muscle efficiency.

Aged↗
PubMed1986

Nutritional intervention in malnourished patients with emphysema.

We have previously reported the association of significant malnutrition with pulmonary emphysema and noted that the degree of malnutrition correlated with some measures of pulmonary function. The purpose of this study was to examine the energy requirements of malnourished patients with emphysema and acute effects of nutritional repletion on indices of pulmonary function and nutrition. We studied 6 malnourished patients with emphysema during a 3-wk admission to a clinical research unit. Initially, patients were allowed access to standard food sources ad libitum. Subsequently, if caloric goals were not met, nutritional supplementation was given orally. All patients receiving the ad libitum diet ingested calories in excess of their maintenance energy requirements. All patients increased their body weight (p less than 0.001) and percent ideal body weight (p less than 0.001). Anthropometric nutritional parameters showed a small but significant improvement (p less than 0.05). Although there was no significant change in spirometric results, lung volumes or DLCO after 3 wk maximal inspiratory mouth and transdiaphragmatic pressures increased (p less than 0.005). Peripheral skeletal muscle strength as measured by handgrip also improved (p less than 0.001). We conclude that inability to ingest an adequate number of calories was not the cause of weight loss in these patients. We also found that when given sufficient calories in excess of their needs, patients gain weight. Weight gain and improvement in anthropometric measurements are accompanied by significant improvement in ventilatory and peripheral muscle strength.

Aged↗
PubMed1985

Prolonged expiratory phase in sleep apnea. A unifying hypothesis.

The mechanisms responsible for the various sleep apnea patterns have not been elucidated. In 5 hypersomnolent patients, we analyzed 613 events that would have been labeled mixed and central apneas had usual recording sensitivity been employed. Recording air flow at high sensitivity revealed that in most of these events expiratory flow was present throughout most of the prolonged period during which there was no inspiratory effort. In 378 events, resumption of inspiratory effort was unaccompanied by air flow (occluded events), whereas in 144 events resumption of inspiratory effort was accompanied by inspiratory air flow (not-occluded events). In another 91 events, expiratory air flow ceased during the interval between inspiratory efforts and then recommenced unaccompanied by expiratory effort suggesting airway closure and reopening. Because expiratory air flow is present during a substantial portion of the prolonged interval between inspiratory efforts seen in our sleeping patients, we conclude that "apneas" should be defined relative to absence of inspiratory air flow. In addition, it appears that the initial portion of "mixed," and at least some "central apneas," are associated with increased expiratory upper airway resistance.

Adult↗
PubMed1984

The diffusing capacity as a predictor of arterial oxygen desaturation during exercise in patients with chronic obstructive pulmonary disease.

We evaluated 48 patients with chronic obstructive pulmonary disease by means of pulmonary-function and exercise testing to determine whether any tests of pulmonary function could predict the development of arterial desaturation during exercise. We found that only two indexes--diffusing capacity and forced expiratory volume in one second (FEV1)--were predictive of desaturation. The diffusing capacity was more specific and sensitive than FEV1. A diffusing capacity above 55 per cent of predicted was 100 per cent specific in excluding desaturation, as compared with an 82 per cent specificity for an FEV1 above 55 per cent of predicted. With this cutoff point, the sensitivity of the diffusing capacity was 68 per cent, as compared with 46 per cent for the FEV1. Both the frequency and the magnitude of arterial desaturation increased substantially when the diffusing capacity was below 55 per cent of predicted. Testing the diffusing capacity should be useful in identifying which patients with chronic obstructive lung disease are likely to become desaturated during exercise and may therefore benefit from oxygen therapy.

Aged↗
PubMed1983

A simplified computer report. Towards an understandable pulmonary function test.

We have developed a graphic format for the display of pulmonary function test results. Patient test results appear as a series of horizontal bar graphs. Each bar length is proportional to the test result and is printed over the normal ranges. This format allows rapid recognition of individually abnormal values. We have also grouped bars to create distinctive patterns characteristic of obstructive or restrictive lung disease. A computer program generates a custom form for each patient, displaying the results and ranges only for the specific test performed on that individual. No preprinting of forms is required. Written in the BASIC computer language, this program was designed to be flexible. A change of program parameters requires only minor program modification. In addition, because of its simplicity, our program can be implemented on almost any computer printer.

Computers↗
PubMed1983

Pulmonary function in progressive systemic sclerosis. Comparison of CREST syndrome variant with diffuse scleroderma.

The pulmonary function and chest roentgenograms were evaluated in 88 patients with the CREST syndrome variant of progressive systemic sclerosis (PSS or scleroderma). Seventy-two percent of the patients had abnormal pulmonary function. An isolated decrease in diffusing capacity was the most common abnormality noted, followed by restrictive abnormalities and airway obstruction. Chest roentgenograms revealed interstitial infiltrates consistent with pulmonary fibrosis in 33 percent. When compared to a contemporaneous group of 77 patients with PSS and diffuse scleroderma, patients with the CREST syndrome had similar abnormalities on pulmonary function testing and chest roentgenogram. However, patients with the CREST syndrome had a lower mean diffusing capacity despite a higher mean vital capacity; this combination of findings suggests primary pulmonary vascular disease. Calcified granulomata were identified significantly more often in PSS-CREST patients, while superior rib notching occurred exclusively in patients with PSS and diffuse scleroderma. The CREST variant of PSS is associated with frequent roentgenographic and pulmonary function abnormalities similar to those seen in PSS with diffuse scleroderma.

Adult↗
PubMed1983

Pulmonary function testing. What is 'normal'?

For many years, confusion has existed concerning the normal range for pulmonary function test results. Using statistical guidelines that have been traditionally applied to the interpretation of measured forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1), we have redefined normal limits for the most common pulmonary function test values, including those for FVC, FEV1, mean forced expiratory flow during the middle half of the FVC, FEV1 as a proportion of FVC, residual volume, functional residual capacity, total lung capacity, diffusion capacity, maximum voluntary ventilation, and peak expiratory flow. Our goal is to provide a simple and consistent scheme for interpretation of pulmonary function test data. We consider the assumptions used to achieve this simplification to be reasonable, as long as their limitations are understood.

Humans↗
PubMed1981

Rapid conversion of pH to [H+].

Sir William Osler described the practice of medicine as "an art based on Science." The authors have artfully simplified a frequently needed clinical calculation, using sequential multiplication and obviating the need for logarithmic manipulation.

Acid-Base Equilibrium↗
PubMed1980

Respiratory hypersensitivity to Ascaris extract in guinea pigs sensitized by aerosol.

Guinea pigs exposed via the respiratory route to Ascaris suum extract in aerosol form became hypersensitive. The hypersensitivity was detectable by inhalational bronchial provocation testing using a noninvasive plethysmography, by chopped lung histamine release, and by passive cutaneous anaplylaxis. The antibody responsible for the hypersensitivity seems to be directly associated with pulmonary tissue. A locally produced cytotropic pulmonary antibody, probably IgG or IgE may be causal. Histopathology included only a moderate pulmonary eosinophilia. Individual variability in susceptibility to experimental allergic asthma may be controlled by both physiologic and immunologic reactivities.

Aerosols↗
PubMed1979

A noninvasive technique for measurement of changes in specific airway resistance.

A simple noninvasive technique for measuring specific airway resistance (airway resistance X thoracic gas volume) in unanesthetized guinea pigs is described. Specific airway resistances measured by this technique correlated well (r = 0.81) with the resistances obtained using a pleural catheter pressure measurement over a wide range of airway resistances. This range of resistances was generated by exposing the pigs to an aerosolized histamine bronchial challenge. The average specific airways resistance in unchallenged pigs was 1.24 +/- 3.47 cmH2O/s, somewhat lower than found by others, probably reflecting in part our larger pigs and in part some uncertainty in the absolute value of resistance inherent in our measurement technique. This technique is particularly useful in bronchial challenge experiments because of its sensitivity to acute changes in airway resistance.

Airway Resistance↗