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J J Pretto

Publications and source records attributed to J J Pretto.

9 recordsLinked to original sources
PubMed2001

Using baseline respiratory function data to optimize cycle exercise test duration.

BACKGROUND: It is often difficult to select an appropriate workload increment for progressive cycle exercise tests in order to achieve optimal test duration (8-12 min). We hypothesize that baseline respiratory function can be systematically used to select appropriate workload increment to optimize test duration in patients referred to the clinical laboratory. METHODOLOGY: One hundred and eighty consecutive exercise tests (with increments of 15 W/min) were retrospectively assessed. Using regression analysis, an equation was generated that predicts the work rate increment that would provide exercise duration of 8-12 min. The validity of this equation was tested prospectively in 231 consecutive tests performed with the calculated workload increment rounded to the nearest 5 watts (W). RESULTS: The best regression equation was: workload increment (W/min)=1.94 x FEV1 (L) + 0.63 x TLCO (mmol/min per kPa) - 0.07 x age + 1.94 x gender (male=1, female=0) + 4.12 (r=0.85, P < 0.0001). Using this equation allowed selection of the most appropriate workload increment in 79% of tests and reduced the number of tests of non-optimal duration from 72% (for a fixed increment of 15 W/min) to 38%. CONCLUSIONS: Utilization of this regression equation allows standardization in the selection of workload increment, and reduces the number of cycle exercise tests of inadequate duration.

Algorithms↗
PubMed1997

Resolution of gas exchange abnormalities and intrapulmonary shunting following liver transplantation.

This prospective study evaluated pulmonary gas exchange in patients with severe liver disease, its relationship to intrapulmonary shunting, and its response to liver transplantation. Detailed clinical examinations, chest radiographs, and arterial blood gas estimations were performed on 74 consecutive patients before and after liver transplantation. Fifty percent of the 74 patients had a widened alveolar-arterial (A-a) oxygen gradient (> 15 mm Hg) and 45% a reduced PaCO2 (< 35 mm Hg). Twenty-two percent were hypoxemic (PaO2 < 80 mm Hg). Following transplantation mean PaO2 increased (pre-89 +/- 14 vs. post-94 +/- 8 mm Hg; P = .014) and A-a oxygen gradient decreased (pre-16 +/- 14 vs. post-8 +/- 9 mm Hg; P < .001), despite an increase in PaCO2 (pre-36 +/- 5 vs. post-39 +/- 4; P < .001). To examine this improvement in oxygen exchange further, a subgroup of 26 consecutive patients, with no obvious cardiorespiratory cause for abnormal gas exchange underwent, pre- and post-operative spirometry, measurement of carbon monoxide diffusion capacity (DLCO), intrapulmonary shunt estimations (100% oxygen technique), and echocardiography. In this subgroup, 23% were hypoxemic, 54% had a widened A-a oxygen gradient, and 85% had increased intrapulmonary shunting (> 5%) before transplantation. There was a significant correlation between the degree of pre-transplantation intrapulmonary shunting and A-a oxygen gradient (P < .01). Nineteen of the 22 patients with increased shunting improved following transplantation and improved A-a oxygen gradient correlated well with the reduction in shunting (P < .005). DLCO was reduced in 69% of these patients with a mean value of 73% of predicted. However, the post-transplantation mean DLCO did not increase despite the improvement in oxygen exchange. In conclusion, gas exchange abnormalities are common in patients with severe liver disease but these usually resolve post-transplantation. Intrapulmonary shunting is a major determinant of abnormal oxygen uptake in transplant candidates without evidence of cardiorespiratory disease. Finally, the mechanism for the reduced DLCO is unclear but appears different to that responsible for intrapulmonary shunting and abnormal oxygen exchange.

Adult↗
PubMed1995

Is normobaric simulation of hypobaric hypoxia accurate in chronic airflow limitation?

Hypobaric hypoxemia is experienced by passengers during commercial aircraft flight. In order to assess the extent of hypoxemia and to test whether hypobaric hypoxia can be accurately estimated at sea level, the results of the normobaric hypoxia altitude simulation test (N-HAST) were compared with those of the hypobaric hypoxia altitude simulation test (H-HAST) in six normal control subjects and nine patients with chronic airflow limitation (CAL) at simulated cabin altitudes of 6,000 ft (1,829 m) and both at rest and during exercise at 8,000 ft (2,438 m). Serial arterial blood samples were drawn during the breathing of 15.1 and 16.3% inspired oxygen at sea level (N-HAST) at rest and during light exercise, and during the breathing of room air at simulated cabin altitudes (H-HAST) of 609 mm Hg (6,000 ft) and 565 mm Hg (8,000 ft) at rest and during light exercise. As measured with the H-HAST technique, the mean (+/- SD) PaO2 of the normal group fell from 96.2 +/- 6.2 mm Hg (sea level) to 70.1 +/- 6.0 mm Hg (6,000 ft), and to 61.7 +/- 1.6 mm Hg (8,000 ft at rest) and 54.8 +/- 7.1 mm Hg (8,000 ft during exercise) (p < 0.005 by analysis of variance [ANOVA]). In the CAL group, the mean (+/- SD) PaO2 fell from 75.8 +/- 8.2 mm Hg (sea level) to 57.0 +/- 6.3 mm Hg (6,000 ft), and 49.5 +/- 6.1 mm Hg (8,000 ft at rest), and 38.6 +/- 7.5 mm Hg (8,000 ft during exercise) (p < 0.005 by ANOVA).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Effects of sample storage time, temperature and syringe type on blood gas tensions in samples with high oxygen partial pressures.

BACKGROUND: Although plastic arterial sampling syringes are now commonly used, the effects of sample storage time and temperature on blood gas tensions are poorly described for samples with a high oxygen partial pressure (PaO2) taken with these high density polypropylene syringes. METHODS: Two ml samples of tonometered whole blood (PaO2 86.7 kPa, PaCO2 4.27 kPa) were placed in glass syringes and in three brands of plastic blood gas syringes. The syringes were placed either at room temperature or in iced water and blood gas analysis was performed at baseline and after 5, 10, 20, 40, 60, 90, and 120 minutes. RESULTS: In the first 10 minutes measured PaO2 in plastic syringes at room temperature fell by an average of 1.21 kPa/min; placing the sample on ice reduced the rate of PaO2 decline to 0.19 kPa/min. The rate of fall of PaO2 in glass at room temperature was 0.49 kPa/min. The changes in PaCO2 were less dramatic and at room temperature averaged increases of 0.47 kPa for plastic syringes and 0.71 kPa for glass syringes over the entire two hour period. These changes in gas tension for plastic syringes would lead to an overestimation of pulmonary shunt measured by the 100% oxygen technique of 0.6% for each minute left at room temperature before analysis. CONCLUSIONS: Glass syringes are superior to plastic syringes in preserving samples with a high PaO2, and prompt and adequate cooling of such samples is essential for accurate blood gas analysis.

Blood Gas Analysis↗
PubMed1990

An evaluation of the Breath-Taker peak flow meter.

This study was designed to evaluate the Breath-Taker peak flow meter, recently released by the Asthma Foundation of Victoria. The performance characteristics of five Breath-Taker units were compared with those of five Wright and five mini-Wright peak flow meters. The between-unit reproducibility of each type of peak flow meter was measured using an explosive decompression device with a peak flow reproducibility of better than 1%. Each individual meter was used to measure the peak flow delivered by the decompression device three times for each of six flow rates (97-622 L/min). The coefficient of variation (CV) was lowest for the Wright meters (mean CV, 4.8%) and, similarly to the Breath-Taker units (mean CV, 8.4%), this decreased with increasing flow. The CV of the mini-Wright meters, however, increased as flow increased (mean CV, 7.5%). The Breath-Taker meter had less inter-unit variability than the mini-Wright meter at peak flows above 200 L/min. The accuracy of the three meter types was assessed by comparing measurements of peak expiratory flow rate (PEFR) made with each type and also with a computerized pneumotachograph system in 30 subjects with various degrees of irreversible airflow obstruction. Each subject performed at least three reproducible PEFR manoeuvres on the pneumotachograph and on each type of meter, in randomized order. The results showed that in comparison with the pneumotachograph system the Breath-Taker meter underestimated PEFRs by a mean of 27 L/min and the mini-Wright meter overestimated PEFRs by a mean of 45 L/min, whereas the Wright meter was not significantly different. Since the differences between the Breath-Taker meter and the pneumotachograph were independent of flow rate, a scale offset would suffice to "correct" the Breath-Taker readings.

Adolescent↗
PubMed1986

Lobar occlusion in the preoperative assessment of patients with lung cancer.

Bronchial occlusion during exercise was used to predict the functional effects of subsequent pulmonary resection in six high risk patients with lung cancer and severe airflow obstruction. Each patient underwent transnasal fibreoptic bronchoscopy whilst cycling in steady state at a load which had been selected as equivalent to walking at a brisk pace for that patient. The effects on minute ventilation and oxygen uptake were observed during occlusion of the bronchus to the diseased lobe. If the patient was able to continue cycling and maintain the same work load during occlusion this was regarded as indicating that he would withstand resection of the occluded lung tissue. In five of the patients, postoperative studies were performed. All were able to maintain the same level of steady state exercise postoperatively as that maintained during bronchial occlusion preoperatively. Resection resulted in a decrease in static lung volumes. Other routine whole lung function tests, walking capacity and incremental exercise indices, however, were largely unchanged.

Aged↗
PubMed1982

Measurement of gas viscosity with a Fleisch pneumotachograph.

A simple rapid method of measuring gas viscosity using a standard Fleisch pneumotachograph and a 3-liter hand-driven syringe is described. Comparison of pneumotachographic and predicted viscosity of five pure gases (CO2, N2, He, O2, and Ar), two binary mixtures (He-O2 and N2-O2), and one quaternary mixture (He-air) gave an overall coefficient of correlation of 0.987 and an accuracy of better than 1.7%. Our data show the well-known marked curvilinear relationship between viscosity and the concentration of helium in air and oxygen mixtures. These studies indicate that a Fleisch pneumotachograph can be used as a simple accurate gas viscometer to characterize gas mixtures in terms of viscosity.

Gases↗