Search PubMed⌕ Search

Biomedical subjects

B E Pennock

Publications and source records attributed to B E Pennock.

At least 19 recordsLinked to original sources
PubMed1996

Noninvasive ventilation for postoperative support and facilitation of weaning.

Noninvasive ventilation includes continuous positive airway pressure with mask, positive pressure ventilation with mask, and negative pressure body ventilation. Noninvasive ventilation is a ventilatory support mode intermediate in both effectiveness and potential complications between oxygen administration and intubation with mechanical ventilation. The advantages, disadvantages, and experimental results of the use of noninvasive ventilation in patients who have been extubated following recovery from surgery and subsequently experience respiratory difficulties are discussed. In general, noninvasive ventilation seems to provide useful ventilatory support in about three of four patients in whom it is tried. In addition, the use of noninvasive ventilation as an aid to weaning of patients from mechanical ventilation is discussed. This use of noninvasive ventilation has not yet been extensively reported, although it appears to be potentially useful.

Acute Disease↗
PubMed1994

Noninvasive nasal mask ventilation for acute respiratory failure. Institution of a new therapeutic technology for routine use.

OBJECTIVE: We successfully implemented the delivery of noninvasive mechanical ventilation for patients with acute respiratory failure, a previously controversial use of this technique, using a simplified ventilator (BiPAP) with nasal mask. Pilot work showed this mode of support to be effective when administered by the members of a research team, and in the current study we were able to transfer this responsibility to usual care providers. SETTING: Almost 90 percent of the patients in this study were in either the 16-bed medical or 31-bed surgical intensive care units at our hospital. SUBJECTS: One hundred ten hemodynamically stable patients with acute respiratory failure being considered for intubation and mechanical ventilation participated in this study. Eighty percent were surgical patients, most of whom had hypercapnic failure. INTERVENTION: Patients were administered noninvasive ventilatory support using a ventilatory support system (BiPAP) applied with a nasal mask. This intervention was administered by a research team in the initial 31 patients (special care, phase 1). The administration was transferred to usual care personnel in the next 45 patients (transition, phase 2). Usual care personnel almost exclusively administered care in the final 34 patients (usual care, phase 3). RESULTS: Withdrawal of ventilatory support for greater than 48 h (successful outcome) was about the same during usual care (phase 3, 80 percent) as it was during special care (phase 1, 76 percent).

Acute Disease↗
PubMed1994

Experimental studies on heterotopic lung transplantation during temporary pulmonary insufficiency.

Survival from reversible forms of severe pulmonary insufficiency remains dismal despite the development of artificial oxygenators. We hypothesized that an intraabdominal heterotopic lung could help maintain adequate oxygenation during acute pulmonary insufficiency. Five mongrel dogs underwent an acute heterotopic lung transplant (HLT). The left atrial cuff was anastomosed to the inferior vena cava, and the left pulmonary artery was anastomosed to the abdominal aorta. The trachea was exteriorized, intubated, and ventilated with a volume-controlled ventilator. Ventilation to the native lungs was discontinued. The heterotopic lung was then ventilated at a rate of 20/min, tidal volume of 15 ml/kg, and inspired concentration (FIO2) of 50 percent. Partial pressure of oxygen (PO2) and mixed venous oxygen saturation (SvO2) were maintained at 53 +/- 5.2 mm Hg and 71 +/- 12 percent, respectively. Flow through the HLT was approximately 20 percent of the systemic cardiac output and did not vary with changes in FIO2, respiratory rate, or positive end-expiratory pressure (PEEP). Four separate animals underwent HLT and were studied 2 to 3 days later. The FIO2 was reduced in the native lungs to 10 percent until SaO2 was less than 90 percent. The HLT was then ventilated at a tidal volume of 300 ml, an FIO2 of 50 percent, and a respiratory rate of 10. Arterial PO2 increased from 62 +/- 4 mm Hg to 75 +/- 2 mm Hg, and SvO2 increased from 75 +/- 2 percent to 82 +/- 3 percent (p < 0.05). Flow through the HLT increased slightly to 27 percent of the systemic cardiac output. We conclude that a HLT can augment oxygenation after induction of moderate hypoxemia, but cannot serve as the sole source for gas exchange because flow through the HLT is limited to less than 30 percent of the cardiac output.

Abdomen↗
PubMed1993

Indirect calorimetry with a hood: flow requirements, accuracy, and minute ventilation measurement.

Flow-dilution-based hood systems for indirect calorimetry eliminate the conventional mouthpiece or mask of sealed-circuit systems allow measurements with improved patient comfort. This feature is particularly relevant when measurements are made over long periods of time or are repeated often. The flow of air pulled through the hood into the calorimeter in these systems is necessary to clear CO2 from inside the hood. The errors in these systems are greater than those in the sealed-circuit systems and are proportional to the flow. We show that the CO2 concentration within the hood at steady state does not depend on hood size. We describe the accuracy in determination of O2 consumption (VO2), CO2 production, and respiratory exchange ratio with a hood system as a function of the accuracy of the O2 and CO2 analyzers and the water vapor in collected gas. For example, we show that if there is a 1% error in O2 concentration, the percent error in VO2 changes from 5% in a sealed circuit to 51% when a cleansing flow of 50 l/min is introduced. The error in VO2 caused by a 5% error in CO2 determination is 10.6% at this cleansing flow. Removal of 90% of the water vapor (instead of 100%) before analysis of the expired gas introduces a 15.8% error in VO2. By use of the equations described, the accuracy of any measurement system can be determined. In addition, we demonstrate that the measurement of ventilation, usually lost in a hood system, can be preserved using dual pneumotachographs and a sealed hood.

Air Movements↗
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↗