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A C Jasper

Publications and source records attributed to A C Jasper.

11 recordsLinked to original sources
PubMed1988

Relationship between oxygen uptake and oxygen delivery in patients with pulmonary hypertension.

Dependency of oxygen consumption (VO2) on oxygen delivery (DO2) in patients with adult respiratory distress syndrome and with congestive heart failure has been reported previously. We evaluated this relationship in 11 patients with pulmonary hypertension, 8 with primary pulmonary hypertension (PPH), and 3 with pulmonary hypertension secondary to chronic obstructive lung disease (SPH) at baseline and during treatment with vasodilating calcium channel antagonists. The mean baseline DO2 and VO2 were 11.0 +/- 4.2 and 3.9 +/- 1.1 ml/min/kg, respectively. After increasing cardiac output via vasodilators, we obtained an average of 3 additional data points per patient. We found a significant relationship between changes in VO2 and changes in DO2 (delta VO2 = -0.19 +/- 0.27 x delta DO2; r = 0.88, n = 37). In 4 patients, VO2 was determined both by respired gas analysis and by calculation from thermodilution cardiac output and measured arteriovenous oxygen gradient; results by the 2 methods were virtually identical. There was no significant relationship between cardiac output and mixed venous oxygen content or mixed venous oxygen tension (r = 0.20 and 0.47, respectively). Mean baseline oxygen extraction ratio was 36.7 +/- 6.4% and did not increase significantly after vasodilator therapy. We conclude that in patients with pulmonary hypertension, changes in oxygen consumption appear to be dependent on changes in oxygen delivery. This may represent evidence of tissue hypoxemia, which is otherwise not apparent. This dependency may support the use of vasodilators in these patients.

Biological Availability↗
PubMed1988

Physiologic assessment of lung function in patients undergoing laser photoresection of tracheobronchial tumors.

We performed YAG laser photoresection in 11 patients with tracheal or mainstem bronchial obstruction due to malignant or benign disorders. We used maximal inspiratory-expiratory flow-volume loops and expiratory volume-time plots to assess air flow limitation. Forced vital capacity (FVC), forced expiratory volume in one second (FEV1), peak expiratory flow (PEF) and iso-volume maximal flows at 50 percent of forced inspiratory and expiratory volume were calculated. Spirograms and flow-volume loops were repeated within 12 to 72 hours of laser resection. All patients had flattened expiratory limbs on their flow-volume loops. All spirometric parameters increased significantly following laser photoresection. In particular, peak flow improved in all patients, and FEV1 improved in nine of 11 patients, even though four patients had moderate to severe obstructive ventilatory defects which persisted after resection and were probably due to longstanding chronic obstructive pulmonary disease. We conclude that flow-volume loops and spirometry are helpful in assessing the site and nature of malignant large airway obstructive processes and, moreover, provide reliable information for evaluating the efficacy of laser photoresection. Serial physiologic studies indicate changes in the caliber of the upper airways and can be used as a simple means of following these patients.

Adult↗
PubMed1987

Zone 2 and zone 3 pulmonary blood flow.

In the West model of zonal distribution of pulmonary blood flow, increases in flow down zone 2 are attributed to an increase in driving pressure and a decrease in resistance resulting from recruitment and distension. The increase in flow down zone 3 is attributed to a decrease in resistance only. Recent studies indicate that, besides the pressure required to maintain flow through a vessel, there is an added pressure cost that must be overcome in order to initiate flow. These additional pressure costs are designated critical pressures (Pcrit). Because Pcrit exceed alveolar pressure, the distinction between zones in the West model becomes less secure, and the explanation for the increase in flow even in West zone 3 requires reexamination. We used two methods to test the hypothesis that the Pcrit is the pertinent backpressure to flow even in zone 3, when the pulmonary venous pressure (Ppv) exceeds alveolar pressure (PA) but is less than Pcrit in the isolated canine left caudal lobe. First, PA was maintained at 5 cmH2O, and pressure flow (P-Q) characteristics were obtained in zone 2 and zone 3. Next, with PA still at 5 cmH2O, we maintained a constant flow and measured the change in pulmonary arterial pressure as Ppv was varied. Both techniques indicated that the pertinent backpressure to flow was the greater of either Pcrit or Ppv and that PA was never the pertinent backpressure to flow. Also, our results indicate no significant change in the geometry of the flow channels between zone 2 and zone 3. These findings refine the zonal model of the pulmonary circulation.

Animals↗
PubMed1987

Cost-benefit comparison of aerosol bronchodilator delivery methods in hospitalized patients.

We compared two modes of aerosol bronchodilator delivery in 34 patients hospitalized with obstructive airways diseases. The standard mode, therapist-administered up-draft nebulization (UDN), is labor-intensive and therefore relatively costly. The alternative mode, self-administration by a metered dose inhaler (MDI), is less costly, but its efficacy over an entire hospitalization has heretofore not been established. Patients were enrolled after transfer to the pulmonary ward from the emergency room or intensive care units (ICU). We then randomized them to receive metaproterenol q4h either via MDI or UDN. Daily spirometry revealed that MDI and UDN were associated with equivalent bronchodilation initially and equivalent improvement at discharge. The duration of hospitalization for the two groups was also the same. Thus, the two delivery methods were equally effective. We could not attribute this equivalence to pretreatment intergroup differences or to differences in concomitant therapy with steroids, theophylline, other bronchodilators, or antibiotics. Routine use of MDI rather than UDN in all non-ICU adult patients would save $253,487 per year at our institution alone.

Aerosols↗
PubMed1987

Dependence of oxygen consumption on oxygen delivery in patients with chronic congestive heart failure.

We previously have shown that in patients with adult respiratory distress syndrome (ARDS) oxygen consumption (VO2) is linearly related to oxygen delivery (DO2) below a threshold DO2 of 21 ml/min/kg. To evaluate this relationship in chronic congestive heart failure (CHF), we studied eight patients with chronic CHF at baseline and during treatment with nitroglycerin. The resting DO2 and VO2 were 10.7 +/- 2.3 ml/min/kg and 3.8 +/- 0.87 ml/min/kg, respectively. In our eight patients, we found a significant relationship between changes in VO2 and in DO2 (delta VO2 = 0.16 + 0.34 X delta DO2, r = 0.84, n = 29). There was no significant relationship between DO2 and mixed venous oxygen tension (PvO2, r = 0.16), nor was there a significant relationship between cardiac output (Qt) and PvO2 (r = 0.21). We conclude that in patients with chronic CHF, changes in VO2 appear to be dependent on changes in DO2. This may represent an adaptive tissue response to chronically reduced systemic oxygen transport.

Blood Gas Analysis↗
PubMed1987

Prostaglandin E1 as a screening vasodilator in primary pulmonary hypertension.

Pulmonary vasodilators are variably efficacious in primary pulmonary hypertension (PPH). None has consistently improved hemodynamics enough to obviate the need for complex and potentially hazardous testing of several vasodilators. Prostaglandin E1 (PGE1), a potent, short-acting pulmonary vasodilator, was administered to seven patients with PPH in order to determine whether PGE1 could accurately predict the hemodynamic and gas exchange effects of other commonly used vasodilators. Prostaglandin E1, nifedipine and hydralazine were administered to the patients while measuring pulmonary and systemic hemodynamics and arterial blood gases. Prostaglandin E1 was easily titrated but was inconsistent as a predictor of the effects of the other vasodilators with respect to pulmonary artery pressure, cardiac output and adverse effects on arterial oxygenation. This study suggests that patients with PPH must still receive carefully monitored trials of several vasodilators to determine whether there is a beneficial response and to select the appropriate treatment.

Adult↗
PubMed1986

Respiratory drive and timing during assisted ventilation in dogs.

In 8 anesthetized dogs, during isocapnic hyperoxia we studied the effect of assisted ventilation (AV) on ventilatory drive, inspiratory off-switch volume (Voff) and duration of inspiratory diaphragmatic activity (Tdi). Tidal volumes (Vt) during AV were double spontaneous Vt. Two electrodes were inserted in the diaphragm to obtain the electromyogram (EMG). The index of ventilatory drive was the EMG 0.3--i.e., the amplitude of the moving average EMG 300 ms after the onset of inspiratory activity. AV decreased EMG 0.3 but had no effect on Voff and Tdi. Vagotomy not only abolished the reduction in drive, but may have increased drive during AV.

Animals↗
PubMed1986

Relationship of arterial wedge pressure to closing pressure in the pulmonary circulation.

We studied the relationship between the pulmonary artery wedge pressure (Pw) and pulmonary venous pressure (Ppv) at 2 alveolar pressures (PA) in 7 isolated perfused dog lobes. If PA were the critical pressure in the pulmonary circulation, one would expect Pw to equal Ppv for all Ppv greater than PA. Relative to the hilum, the average critical pressure in these lobes was 15.07 +/- 0.40 cmH2O at PA = 5 cmH2O and increased significantly to 17.23 +/- 0.82 cmH2O at PA = 7 cmH2O. Because the critical pressure in fact exceeded PA, Pw was found to be relatively constant and independent of Ppv even when Ppv exceeded PA by 5 cmH2O or more. For example, at PA = 5.13 +/- 0.04 cmH2O and Ppv = 9.64 +/- 0.28, the mean value for Pw was 13.30 +/- 0.59 cmH2O. Pw is equal neither to the average critical pressure nor to PA, but instead lies between these two values. It is determined by the spectrum of closing pressures in the pulmonary circulation, and the time-constants for drainage of beds downstream from the occluded pulmonary arterial branch.

Animals↗
PubMed1984

Change in extra-alveolar perimicrovascular pressure with lung inflation.

In eight isolated dog lobes, we examined the change in extra-alveolar perimicrovascular hydrostatic pressure (Pis) due to lung inflation. The vasculature was filled with autologous plasma. Pulmonary arterial and venous lines were connected to a common plasma reservoir. Perimicrovascular volume change (delta Vis), compliance (Cis), and the microvascular filtration coefficient (Kf) were derived from the change in lobe mass over time following a step increase in vascular pressure (Piv). Initially, transpulmonary pressure (PL) was 5 cmH2O and Piv = 0 cmH2O. At constant Piv, two sequential 5-cmH2O increases in PL increased Vis; division of delta Vis by Cis yielded the change in Pis attributable to lung inflation. Cis was 0.035 +/- 0.018 g X cmH2O-1 X g dry mass-1 (mean +/- SD) at PL = 15 cmH2O. Kf was 0.019 +/- 0.023 g X min-1 X cmH2O-1 X g dry mass-1. With inflation from PL = 5 to PL = 10 cmH2O, Pis = -2.15 +/- 1.76 cmH2O; from PL = 10 to PL = 15 cmH2O, Pis = -2.25 +/- 1.50 cmH2O. This perimicrovascular pressure change is very close to the perihilar interstitial pressure change reported by others. Such near equality suggests that the stress of lung inflation is very uniformly applied to the interstitial continuum.

Animals↗
PubMed1979

Medspeak.

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