Biomedical subjects

G F Dolan

Publications and source records attributed to G F Dolan.

10 recordsLinked to original sources

PubMed1989

Oxygen transport and oxygen consumption during supplemental oxygen administration in patients with chronic obstructive pulmonary disease.

PURPOSE: Oxygen consumption (VO2) is independent of oxygen delivery (DO2) above a critical level of DO2. VO2 may become dependent on DO2 when oxygen demand exceeds oxygen supply. We studied DO2 VO2, and exercise capacity in 12 stable, ambulatory patients with chronic obstructive pulmonary disease (COPD) receiving ambient air and 26% oxygen to ascertain whether VO2 is dependent on DO2 in this patient sample. PATIENTS AND METHODS: An exercise protocol consisting of a symptom-limited, low-level treadmill test with progressive increments in workload was performed twice, once with patients breathing ambient air and once with patients breathing 26% oxygen. Expired gas, arterial and mixed venous blood values, and recordings of systemic and pulmonary artery pressures were obtained after a 10-minute period of rest (while standing) and during the last minute of each three-minute exercise level. RESULTS: Five patients had an increase in exercise capacity, defined as an increase in the maximal VO2 greater than 25%, using supplemental oxygen. In these patients, oxygen delivery increased from 10.9 +/- 3.4 to 13.8 +/- 4.7 mL/minute/kg (p = 0.008) at rest and from 16.2 +/- 5.0 to 24.7 +/- 2.7 mL/minute/kg (p = 0.046) during exercise with supplemental oxygen administration. VO2 increased from 0.329 +/- 0.065 to 0.436 +/- 0.109 L/minute (p = 0.029) at rest and from 0.776 +/- 0.275 to 1.119 +/- 0.482 L/minute (p = 0.048) during exercise. Three of these five patients had an arterial oxygen pressure greater than 55 mm Hg at rest. Seven patients had little or no increase in exercise capacity with supplemental oxygen. This patient group had no increase in VO2 at rest. The DO2 failed to increase at rest despite an increase in arterial oxygen content because of a reduction in cardiac output. CONCLUSION: These data demonstrate that DO2 may fail to increase in some patients with COPD and resting or exertional hypoxemia when supplemental oxygen is administered because of a reduction in cardiac output; that patients who fail to increase their DO2 are less likely to increase exercise capacity; and that some stable, ambulatory patients with COPD who do not qualify for supplemental oxygen at rest by current standards may have inadequate DO2 to meet physiologic needs.

Aged↗

PubMed1989

Exercise capacity following pulmonary rehabilitation in the elderly.

Pulmonary rehabilitation has proven beneficial for patients with chronic airway obstruction. In this study, the authors evaluate the effect of rehabilitation in elderly patients. Results show that the change in exercise capacity was not related to the patients' age, and suggest that age alone should not be an exclusionary criterion.

Adult↗

PubMed1985

Relationship of ventricular ectopy to oxyhemoglobin desaturation in patients with obstructive sleep apnea.

Patients with obstructive sleep apnea are considered to be at increased risk of sudden, presumably arrhythmia-related death during sleep. The present study was undertaken to determine the relationship between ventricular ectopy and the severity of oxyhemoglobin desaturation in these patients. Thirty-one male patients with obstructive sleep apnea (mean age, 55 +/- 11 years) underwent overnight polysomnography. Arterial oxyhemoglobin saturation (SaO2) was monitored by ear oximetry, and premature ventricular complexes (PVC) were detected using electrocardiographic leads CC5 and CM5. The data were recorded on electromagnetic tape for subsequent computer-assisted analysis to obtain PVC frequency as a function of decile levels of SaO2. Total sleep time averaged 333 +/- 75 minutes, the apnea index was 44 +/- 26 per hour, and the hypopnea index was 18 +/- 24 per hour. Premature ventricular complexes were observed in 23 (74 percent) of the subjects. By analysis of variance, no significant relationship was found between PVC frequency and decile levels of SaO2 for saturations greater than 60 percent; however, in the 16 subjects with SaO2 below 60 percent, a significant increase in PVC frequency was detected with decreasing SaO2 (p less than 0.01). Ventricular bigeminy was observed with SaO2 below 60 percent in three of these 16 subjects. From these results, we conclude that patients with obstructive sleep apnea are at relatively low risk of developing ventricular arrhythmias provided SaO2 remains greater than 60 percent, while those with SaO2 below 60 percent are at increased risk and should be managed accordingly.

Adult↗

PubMed1979

Immersion vs pressure-breathing and diaphragmatic function in the upright position.

In seven anesthetized dogs, immersion in the upright position to mid-neck level (IM) was compared to pressure breathing (PB) under dry conditions during constant-stimulus diaphragmatic contraction (EPS). The comparison was in terms of EPS-induced changes in alveolar pressure under static condition (Pmus); EPS-induced tidal volume (VT); and the VT/Pmus ratio (C'). It was found that at iso-lung volume (V): (a) Pmus was greater in IM than in PB, the difference increased at higher V; (b) VT was greater in IM than in PB, but the VT difference (deltaVT) did not parallel that in Pmus; VT was maximum at a V equal to approximately 90% of FRC in air (FRCd) and decreased below and above this volume; (c) during both IM and PB, the VT-V relationship reflected a biphasic relationship of C' to V and appeared to be inherent to the upright position.

Animals↗

PubMed1979

Hypoxemia during exercise in patients with chronic obstructive pulmonary disease.

Arterial oxygenation at rest and during maximal treadmill exercise was studied in a group of 17 patients with chronic obstructive pulmonary disease. Patients who developed exertional hypoxemia (subgroup 1) were compared to others who did not (subgroup 2). There was no significant difference between the 2 subgroups at rest in terms of mixed venous PO2, cardiac output, or venous admixture. Subgroup 1 had more severe respiratory impairment than subgroup 2, but there was marked overlap of their respective lung volumes and flows. Both subgroups showed the same extent of desaturation of mixed venous blood during maximal treadmill exercise, so that exertional hypoxemia cannot be explained on the basis of low mixed venous O2. The marked difference between subgroup 1 and subgroup 2 was that the latter showed decreased venous admixture on exercise. Because of the relative constancy of mixed venous blood desaturation, arterial saturation was closely correlated with venous admixture both at rest (r = 0.931) and during exercise (r = 0.985).

Arteries↗

PubMed1978

Functional residual capacity and body position in the dog.

Resting lung volumes in the supine position (FRCs) were determined by N2 washout method in 67 dogs under pentobarbital anesthesia and computed in ml/kg body weight (BW). In 21 other dogs, FRCs and the change in FRC from the supine to upright positions (deltaFRC) were determined; these lung volumes were expressed in ml/kg BW and in percentage of TLC40 (lung volume at 40 cmH2O positive-pressure inflation). It was found that a) FRCs averaged 38.6 plus or minus 8.2 and 42 plus or minus 5.9 ml/kg BW in the two groups of dogs; b) deltaFRC averaged 23 plus or minus 4 ml/kg BW resulted in large data dispersion, a large coefficient of variation (CV) and a poor correlation (r) of lung volume to BW; D) on the contrary, marked uniformity of FRCs and FRCu (upright FRC) was obtained by expressing the resting lung volumes in %TLC40, allowing an accurate prediction of FRC from the inspiratory capacity (IC). Relationship of FRCu to TLC was comparable to human data reported in the literature. FRCs (%TLC40) was smaller than values previously reported for awake human subjects, probably due to the FRCs reduction in our dogs by anesthesia.

Animals↗

PubMed1977

Clinically suspected deep venous thrombosis of the lower extremities. A comparison of venography, impedance plethysmography, and radiolabeled fibrinogen.

To define the utility of new diagnostic approaches in patients with clinically suspected deep venous thrombosis of the lower extremities, 42 legs of 33 patients were studied by fibrinogen labeled with radioactivie iodine (125I) impedance plethysmography (IPG), and contrast venography. The clinical diagnosis was confirmed in approximately two thirds of the legs and patients. In venogram-positive legs, fibrinogen 125I was positive in 70%, IPG in 61%, and one of the two in 78%. In venogram-negative legs, fibrinogen 125I was positive in four (21%) and IPG was negative in all. It was found that the size, age, and location of the thrombus, collateral vein development, heparin sodium therapy, and technical-interpretive choices can influence both IPG and fibrinogen 125I results. The data demonstrate that the fibrinogen 125I and IPG procedures can assist physicians in the diagnosis of clinically suspected deep venous thrombosis of the lower extremities.

False Negative Reactions↗

PubMed1977

Diaphragmatic function during immersion.

Diaphragmatic function during immersion to midneck level was studied in upright mongrel dogs, using constant electrophrenic stimulation. Effectiveness of diaphragmatic contraction was analyzed in terms of inspired volume (VT) (with airways open), and change in intrathoracic pressure (Pmus) (with the respiratory system occluded). Hydrostatic compression of the immersed body decreased functional residual capacity (FRC) to 55% base-line value (FRCO), resulting in a 2.8-fold increase in Pmus. In spite of this Pmus increase, VT often decreased during immersion, averaging only 83% VTO (base-line value in air). Hence, immersion was associated with a marked stiffening of the respiratory system. The Pmus increase during immersion persisted after restoration of FRC to FRCO, and was related to diaphragmatic length being greater in water than in air under condition of iso-lung volume. In all, there were three factors affecting diaphragmatic function during immersion: FRC reduction, change in thoracic configuration, and stiffening of the respiratory system.

Animals↗

PubMed1976

Effect of hyperinflation on inspiratory function of the diaphragm.

The inspiratory efficiency of the diaphragm during unilateral and bilateral phrenic stimulation (UEPS and BEPS) with constant stimulus was studied in seven dogs from FRC to 120% TLC. Alveolar pressures (PAl) were recorded during relaxation, BEPS and UEPS at each lung volume in the closed respiratory system. From the PAl-lung volume curves, tidal volume (VT), and pressure developed by the diaphragm (Pmus) were derived. Results are summarized below. a) Hyperinflation impaired the inspiratory efficiency of the diaphragm which behaved as an expiratory muscle beyond the lung volume of 103.7% TLC (Vinef). b) The diaphragm during UEPS became expiratory at the same Vinef as during (BEPS. C) The VT-lung volume relationship was linear during BEPS, allowing simple quantitation of VT loss with hyperinflation and prediction of Vinef. d) With only one phrenic nerve stimulated, the functional loss is less pronounced in VT than in Pmus, as compared to BEPS, indicating that the respiratory system was more compliant during UEPS than BEPS. This compliance difference from UEPS to BEPS diminished with severe hyperinflation.

Animals↗

PubMed1975

Stability in lobar ventilation distribution during change in thoracic configuration.

Stability in lobar ventilation was examined in dogs during bilateral electrophrenic respiration (BEPR) and positive pressure-assisted ventilation (PPAV). Bilateral prior ligation of the lower and middle lobe pulmonary arteries monitoring of upper lobe ventilation as alveolar minute ventilation (VA), middle and lower lobe ventilation as dead space (VD), and VD/VT ratio, both calculated by the Bohr equation. As documented by chest films, transverse and anteroposterior thoracic diameters during BEPR decreased below FRC values whereas thoracic cephalocaudal dimension greatly increased. During PPAV, all thoracic dimensions increased. Despite these dissimilar regional chest movements, VA, VD, and VD/VT ratio were comparable between PPAV and BEPR under conditions of matched tidal volume and respiratory frequency. Stability in upper lobe ventilation during BEPR was maintained by caudal displacement despite the compression of the rib cage, as documented by tantalum bronchography. Lobar-interdependence appears to be the mechanism transmitting negative pleural pressure developed by the diaphragm to the upper lobes via lower and middle lobe inflation.

Animals↗