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Biomedical subjects

A Patessio

Publications and source records attributed to A Patessio.

At least 19 recordsLinked to original sources
PubMed2001

Diaphragm fatigue during exercise at high altitude: the role of hypoxia and workload.

The effect of high altitude (HA) on exercise-induced diaphragm fatigue in normal subjects was examined. Eight normal subjects completed an incremental exercise test at sea level (SL) and at 3,325 m. Before (baseline), during, and after exercise (recovery), maximal transdiaphragm pressure (Pdi,sniff), breathing pattern, and diaphragmatic effort (PTPdi) were measured. Arterialized blood lactate was measured at baseline and during recovery. At maximal exercise (WRmax) Pdi,sniff fell to 72% and 61% of baseline at SL and HA respectively, recovering to baseline in 60 min at SL, and >60 min at HA. At the 5th min of recovery, circulating lactate was six-fold and seven-fold baseline at SL and HA, respectively. The time course of circulating lactate recovery was as for Pdi,sniff. At WRmax PTPdi was 80.74+/-9.87 kPa.s(-1) at SL and 64.13+/-8.21 kPa.s(-1) at HA. HA WRmax compared to isowork rate, SL data showed a lower Pdi,sniff (8.90+/-0.68 versus 11.24+/-0.59 kPa) and higher minute ventilation (117+/-11 versus 91+/-13 L.min(-1)), PTPdi being equal. To conclude, in normal subjects hypoxia-related effects, and not an increase in diaphragm work, hastens exercise-induced diaphragm fatigue and delays its recovery at high altitude compared to sea level.

Adult↗
PubMed1999

Physiologic response of ventilator-dependent patients with chronic obstructive pulmonary disease to proportional assist ventilation and continuous positive airway pressure.

To investigate the physiologic effects of proportional assist ventilation (PAV) in difficult-to-wean, mechanically ventilated patients with advanced COPD, we measured in eight ICU patients the breathing pattern, neuromuscular drive (P0.1), lung mechanics, and inspiratory muscle effort (PTPdi and PTPpl) during both spontaneous breathing (SB) and ventilatory support with PAV, CPAP, and CPAP + PAV (in random sequence). PAV (volume assist [VA] and flow assist [FA]) was set as follows: dynamic lung elastance and inspiratory pulmonary resistance were measured during SB; then VA and FA were set to counterbalance the elastic and resistive loads exceeding the normal values, respectively, the inspiratory muscles bearing a normal elastic and resistive workload. CPAP was set close to dynamic intrinsic PEEP (8.3 +/- 3.4 cm H2O). We found significant reductions in P0.1 and PTPdi during both CPAP (-45 and -37%, respectively) and PAV (-50 and -48%, respectively). However, only the combination of PAV and CPAP brought P0.1 (1.69 +/- 0.97 cm H2O) and PTPdi (100 +/- 68 cm H2O. s) within normal values, and ameliorated the breathing pattern compared with SB (tidal volume: 0.69 +/- 0.33 versus 0.33 +/- 0.14 L; breathing frequency, 14.6 +/- 4.6 versus 21.0 +/- 6.5 breaths/min, respectively), without generating ineffective inspiratory efforts. We conclude that in difficult-to-wean COPD patients, (1) PAV improves ventilation and reduces both P0.1 and inspiratory muscle effort; (2) the combination of PAV and CPAP can unload the inspiratory muscles to values close to those found in normal subjects.

Aged↗
PubMed1998

Static intrinsic PEEP in COPD patients during spontaneous breathing.

Intrinsic positive end-expiratory pressure (PEEPi) is routinely determined under static conditions by occluding the airway at end-expiration (PEEPi,st). This procedure may be difficult in patients with chronic obstructive pulmonary disease (COPD) during spontaneous breathing, as both expiratory muscle activity and increased respiratory frequency often occur. To overcome these problems, we tested the hypothesis that the difference between maximum airway opening (MIP) and maximum esophageal (Ppl max) pressures, obtained with a Mueller maneuver from the end-expiratory lung volume (EELV), can accurately measure PEEPi,st. Using this method, we found that, in eight ventilator-dependent tracheostomized COPD patients (age 71+/-7 yr), PEEPi,st averaged 13.0+/-2.9 cm H2O. That measurement was validated by comparison with a reference static PEEPi (PEEPi,st-Ref) taken at the same EELV adopted by patients during spontaneous breathing, and measured on the passive quasi-static pressure-volume (P/V) curve of the respiratory system, obtained during mechanical ventilation. PEEPi,st-Ref averaged 13.1+/-3.0 cm H2O, i.e., a value essentially equal to PEEPi,st measured by means of our technique. We conclude that PEEPi,st can be accurately assessed in spontaneous breathing COPD patients by the difference between MIP and Ppl max during the Mueller maneuver.

Aged↗
PubMed1997

Comparison of invasive and noninvasive saturation monitoring in prescribing oxygen during exercise in COPD patients.

The aim of this study was to determine whether it is possible using ear-oximetry to prescribe the correct oxygen flow rates during exercise in chronic obstructive pulmonary disease (COPD) patients on long-term oxygen therapy (LTOT). Twenty COPD patients on LTOT, with exercise desaturation breathing oxygen at resting flow rates, performed a series of 6-min treadmill walking tests, with a progressive increase in oxygen flows until oxygen saturation measured by ear- or pulse-oximetry (Sp,O2) was above 90%. The exercise studies were repeated the next day, saturation being measured both noninvasively by ear-oximetry (Sp,O2) and invasively by CO-oximeter (Sa,O2). The exercise studies continued until both Sa,O2 and Sp,O2 were above 90%. Reproducibility and agreement of the results were analysed according to Bland and Altman. Sp,O2 was significantly lower than Sa,O2 by, on average, 0.7% (p < 0.004). Sp,O2 reproducibility between the two days was good. The invasive and noninvasive oxygen flow prescriptions agreed in only 10 subjects; in six subjects ear-oximetry over-estimated the oxygen supply (p < 0.0005), whilst in four subjects it underestimated (p < 0.01). Contingency table analysis with coded raw data for the values of the sixth minute (that of the deepest desaturation) showed poor agreement between CO- and pulse-oximetry (Chi-squared p < 0.003). However, theoretically, if the Sp,O2 target had been raised to 93%, there would have been hardly any underestimations of Sa,O2 p = NS). We concluded that noninvasive measurement of oxygen saturation is not adequate for estimating arterial saturation in chronic obstructive pulmonary disease. We suggest, as a working solution, that a new cut-off limit of 93% oxygen saturation measured by pulse oximetry should be used as the value below which exercise-induced desaturation should be corrected in order to allow oxygen to be properly prescribed during activities of daily life.

Exercise Test↗
PubMed1996

Partitioning of inspiratory muscle workload and pressure assistance in ventilator-dependent COPD patients.

To investigate the mechanisms underlying ventilator-dependence in patients with chronic obstructive pulmonary disease (COPD), and to assess the effects of the combination of positive end-expiratory pressure (PEEP) and pressure-support ventilation (PSV) on inspiratory muscle effort, we investigated respiratory mechanics in eight ventilator-dependent COPD patients. The patients' breathing pattern, lung mechanics, diaphragmatic effort (PTPdi), diaphragmatic tension-time index (TTdi), and arterial blood gases were measured during both spontaneous breathing (SB) and ventilatory assistance consisting of PSV alone (15, 20, and 25 cm H2O) and PSV combined with a PEEP of 5 cm H2O (reducing PSV to 10, 15, and 20 cm H2O, respectively, to maintain equivalent inspiratory pressure). The different levels of ventilatory support were delivered in a randomized sequence. Maximal inspiratory (MIP), esophageal (PpImax) and transdiaphragmatic (Pdi(max)) pressures and respiratory drive (P(0.1)) were measured at the beginning of the procedure during SB. We found a high P(0.1) (6.1 +/- 1.7 cm H2O), which seemed to rule out an impairment of respiratory-center output. Apparently, inspiratory muscle strength was compatible with successful weaning (38.5 +/- 8.8, 50.9 +/- 9.7, and 51.8 +/- 9.5 cm H2O for MIP, PPImax and Pdi(max), respectively). However, abnormal respiratory mechanics (particularly an intrinsic positive end-expiratory pressure (PEEPi) of 8.3 +/- 1.9 cm H2O and pulmonary resistance 24.7 +/- 9.5 cm H2O/L/s imposed an excessive load on the inspiratory muscles, as indicated by a high PTPdi (499 +/- 122 cm H2O x s). Increasing levels of PSV progressively and significantly unloaded the patients' inspiratory muscles, although at pressures above 20 cm H2O uncoupling occurred between patient and ventilator respiratory frequency. Application of PEEP during PSV improved ventilatory assistance by further reducing the inspiratory effort (by 17% on average) and by ameliorating patient-ventilator interaction. We conclude that the excessive mechanical load, and in particular the high PEEPi, is the major determinant of ventilator-dependence in COPD patients. Application of PEEP improves the efficiency of PSV in unloading these patients' inspiratory muscles, and can sometimes improve patient-ventilator interaction.

Aged↗
PubMed1994

Physiologic effects of positive end-expiratory pressure and mask pressure support during exacerbations of chronic obstructive pulmonary disease.

To assess physiologic effects of continuous positive airway pressure (CPAP) and positive end-expiratory pressure (PEEP) during noninvasive pressure support ventilation (PSV) in patients with acute exacerbation of chronic obstructive pulmonary disease (COPD), we measured in seven patients the breathing pattern, lung mechanics, diaphragmatic effort (PTPdi), and arterial blood gases under four conditions: (1) spontaneous breathing (SB); (2) CPAP; (3) PSV of 10 cm H2O; and (4) PSV plus PEEP (PEEP + PSV). CPAP and PEEP were set between 80 and 90% of dynamic intrinsic PEEP (PEEPidyn) measured during SB and PSV, respectively. PEEPidyn was obtained (1) from the decrease in pleural pressure (delta Ppl) preceding inspiration, and (2) subtracting the fall in gastric pressure (delta Pga) caused by relaxation of the abdominal muscles from the delta Ppl decrease. Abdominal muscle activity made PEEPidyn overestimated in almost all instances (p < 0.0001). PSV increased minute ventilation, improved gas exchange, and decreased PTPdi. PEEP added to PSV, likewise CPAP compared with SB, further significantly decreased the diaphragmatic effort (PTPdi went from 322 +/- 111 to 203 +/- 63 cm H2O.s) by counterbalancing PEEPidyn, which went from 5.4 +/- 4.0 to 3.1 +/- 2.3 cm H2O. These data support the use of low levels of PEEP (80 to 90% of PEEPidyn) to treat acute exacerbation of COPD by means of mask PSV.

Acute Disease↗
PubMed1994

Intermediate respiratory care unit: admission criteria.

Intensive care unit (ICU) management of patients on partial ventilatory support is very costly. We opened an intermediate respiratory care unit (RCU), with the aim of providing cost beneficial in-hospital and home care for patients who require mechanical ventilation for at least 8 h.day-1. Prior to admission to an intermediate RCU, it is mandatory to take into consideration not only the patient's overall health status but also his or her prognosis, and rehabilitation chances and environmental factors have to be evaluated.

Humans↗
PubMed1994

Selection criteria for exercise training in patients with COPD.

The physical performance of patients with chronic obstructive pulmonary disease (COPD) is limited mainly by pathophysiological derangements of the ventilatory system. Thus, the exercise performance can be ameliorated by increasing the level of ventilation that they can sustain, or by reducing the ventilatory requirement for a given level of activity. Almost all studies have yielded negative results in COPD patients, in terms of exercise training having the ability to improve VEmax. The only way to reduce the ventilatory requirement is to reduce CO2 output. Lower levels of lactate result in less non-metabolic CO2 produced by bicarbonate buffering. This is the likely mechanism responsible for a lower ventilatory requirement for work rates above the pre-training anaerobic threshold. We specifically wished to determine, whether a program of intensity, frequency and duration known capable of producing a physiologic training effect in healthy subjects, would do so in COPD patients. Further, we sought to determine, whether exercise training at a work rate associated with lactic acidosis is more effective in inducing a training effect in COPD patients than a work rate not associated with lactic acidosis. Nineteen COPD patients were selected and performed an incremental test as well as two square wave tests at a low and a high work rate. Identical tests were performed after an 8-week program of cycle ergometer training either for 45 min/day at a high work rate or for a proportionally longer time at a low work rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗
PubMed1994

Cardiopulmonary exercise testing in interstitial lung disease.

Interstitial lung disease (ILD) can determine severe lung function impairment both at rest and during exercise. Usually, resting measurements of lung and cardiac function give enough information on the degree of the disease. Thus, exercise testing should be reserved only for particular situations such as presence at the same time of cardiac and respiratory involvement, symptomatic patients with normal spirometry, and to check the response to therapy. A better understanding of the pathophysiology and cardiorespiratory consequences of ILD can give an important contribution in improving methods of exercise testing to assess disability. In this perspective, we analyze the factors limiting exercise performance: the progressive hypoxemia that appears or is worsened by exertion; the ventilatory abnormalities that lead to a rapid shallow breathing pattern with a VE that reach the MVV; and the cardiovascular limitation with low maximum heart rate, low cardiac output and high PVR and PAP.

Exercise Test↗
PubMed1993

Comparison of gas exchange, lactate, and lactic acidosis thresholds in patients with chronic obstructive pulmonary disease.

During an incremental exercise test, three consequences of the onset of anaerobic metabolism can be observed: rise in blood lactate (lactate threshold, LT); fall in standard bicarbonate (lactic acidosis threshold, LAT); nonlinear increase in CO2 output (V-slope gas exchange threshold, GET). We compared these thresholds in 31 patients with COPD. We found that the GET and LAT overestimated the LT. A better relationship was found between LAT and GET, even though GET was significantly higher than LAT (by 124 ml/min; p < 0.0001). However, since the bias is appreciably greater at lower LAT values (likely because VCO2 kinetics are slower than VO2 kinetics), we separated the studies into two groups: (A) tests where LAT occurred within the first 2 min of the increasing work rate period, and (B) tests where LAT occurred after 2 min. For Group A, there was a substantial bias between LAT and GET (323 ml/min, p < 0.0001), whereas the bias was much smaller (only 5.4%, though statistically significant) for Group B (57 ml/min, p < 0.01). We conclude that when lactic acidosis occurs after the first 2 min of incremental exercise, the GET closely approximates the point at which blood bicarbonate begins to fall.

Acidosis, Lactic↗
PubMed1993

Home mechanical ventilation in kyphoscoliosis.

The aim of the study was to determine whether intermittent positive pressure ventilation (IPPV), delivered either by nasal mask or by tracheostomy, is able to improve alveolar gas exchange in kyphoscoliotic patients with respiratory failure. We evaluated 17 patients, 10 females and 7 males, aged 52 +/- 12 (mean +/- SD) yrs. Eight had severe respiratory failure (arterial oxygen tension (PaO2) 53.2 +/- 9.3 mmHg (7.1 +/- 1.2 kPa); arterial carbon dioxide tension (PaCO2) 73.3 +/- 12.5 mmHg (9.7 +/- 1.6 kPa), breathing supplemental oxygen), and were put on IPPV via tracheostomy (TIPPV). The others (PaO2 54.5 +/- 5.5 mmHg (7.3 +/- 0.7 kPa); PaCO2 57.9 +/- 7 mmHg (7.7 +/- 0.9 kPa), breathing air), were put on IPPV via nasal mask (NIPPV). Home mechanical ventilation (HMV) was performed at night (7 +/- 1 h) by means of a volume-cycled pressure respirator in control mode. The frequency was adapted to the patient's spontaneous respiratory rate, and then eventually modified according to blood gases. A silicone mask was moulded onto the patient's nose. Supplemental oxygen (to maintain arterial oxygen saturation (SaO2) > 90%) was used only for tracheostomized patients, whereas NIPPV was performed with fractional inspiratory oxygen (FIO2) 21%. Arterial blood samples were obtained for all patients in steady-state condition, 8 +/- 1 h from the withdrawal, breathing air, after 1 and 6 months of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗
PubMed1992

Can long-term oxygen therapy improve exercise capacity and prognosis?

The lack of studies as to whether the correction of desaturations during exercise can play a role in improving survival still leaves many problems usually met in the common practice open. (1) Why prescribe long-term oxygen therapy (LTOT) on exercise? Up to now, supplemental oxygen during exercise seems more an approach to the 'dyspnea symptom' than a pivotal component of a comprehensive strategy for long-term management of severe chronic airway obstruction. (2) Who needs LTOT on exercise? It seems reasonable to correct desaturations if this leads to a substantial improvement in exercise tolerance. As to the method of clinical assessment, pulse oximetry can be used for measuring desaturation between rest and exercise, although absolute values are not reliable. (3) How to prescribe LTOT on exercise? In practice, the O2 flow able to prevent desaturation on exercise, restoring an SaO2 greater than 90%, is the usual prescription criterion after an appropriate testing able to demonstrate a significant increase in exercise tolerance and conducted comparing the results breathing air with those on O2, the patient being unaware of the inhaled mixture. (4) How to administrate LTOT on exercise? A portable source is usually employed to allow the greatest possible independency. A reservoir nasal cannula can halve the oxygen wastage and is less expensive than a pulse demand valve. In patients needing 24-hour oxygen therapy the transtracheal catheter is being used more and more at present.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaerobic Threshold↗
PubMed1992

Ventilatory and metabolic changes as a result of exercise training in COPD patients.

Patients with COPD feel better and are able to sustain a given level of activity longer after a program of exercise training, but the underlying physiologic mechanisms have not been completely elucidated. Since the physical performance of patients with COPD is limited mainly by pathophysiologic derangements of the ventilatory system, the exercise performance can be ameliorated by increasing the level of ventilation that they can sustain or by reducing the ventilatory requirement for a given level of activity. Almost all studies have yielded negative results in patients with COPD in terms of exercise training having the ability to improve VEmax. The only way to reduce the ventilatory requirement is to reduce CO2 output. Lower levels of lactate result in less nonmetabolic CO2 produced by bicarbonate buffering and this is the likely mechanism responsible for a lower ventilatory requirement for work rates above the pretraining anaerobic threshold. We specifically wished to determine whether a program of intensity, frequency, and duration known capable of producing a physiologic training effect in healthy subjects would do so in patients with COPD. Further, we sought to determine whether exercise training at a work rate associated with lactic acidosis is more effective in inducing a training effect in patients with COPD than a work rate not associated with lactic acidosis. Nineteen patients with COPD were selected and performed an incremental test as well as 2 square wave tests at a low and a high work rate. Identical tests were performed after an 8-week program of cycle ergometer training either for 45 min/day at a high work rate or for a proportionally longer time at a low work rate. For the high work rate training group, identical work rates engendered less lactate (4.5 vs 7.2 mEq/L) and less VE (48 vs 55 L/min) after training; the low work rate training group had significantly less lactate and VE decrease (p less than 0.01). Further, in the first group, there was an increase in exercise tolerance averaging 71% in the high constant work rate test. There was a good correlation (r = 0.73, p less than 0.005) between the decrease in blood lactate and the decrease in ventilation. The major findings of this study are that patients with COPD who experience lactic acidosis during exercise can achieve physiologic training responses from a program of endurance training and that training work rates engendering high levels of blood lactate are more effective than work rates eliciting low lactate levels.

Acidosis, Lactic↗
PubMed1991

Reductions in exercise lactic acidosis and ventilation as a result of exercise training in patients with obstructive lung disease.

Though exercise training is part of most pulmonary rehabilitation programs, whether there is a physiologic basis for increased exercise tolerance is unclear. We sought to determine whether patients with chronic obstructive pulmonary disease (COPD) are capable of obtaining a physiologic training effect, as manifested by a reduction in blood lactate and ventilation (VE) at a given level of exercise. We also sought to determine whether training work rate determines the size of the training effect. Nineteen participants with COPD of predominantly moderate severity in an inpatient rehabilitation program performed two cycle ergometer exercise tests at a low and a high work rate for 15 min or to tolerance and also an incremental exercise test to tolerance. Arterial blood was sampled for blood gas and lactate analyses. Identical tests were performed before and after 5-day-per-week cycle ergometer training for 8 wk either for 45 min/day at a high work rate (average, 71 W) or for a proportionally longer time at a low work rate (average, 30 W). Average FEV1 was 56 +/- 12% predicted and did not change with training. Peak exercise lactate (average, 6.5 mEq/L) was not correlated with FEV1. For the high work rate training group, identical work rates engendered less lactate (4.5 versus 7.2 mEq/L) and less VE (48 versus 55 L/min) after training; the low work rate training group had significantly less lactate and VE decrease (p less than 0.01). Further, endurance time for the high constant work rate increased 73% in the high work rate training group but only 9% in the low work rate training group. At identical work rates, VE decrease average 2.5 L/min per mEq/L decrease in lactate (r = 0.75). We conclude that most COPD subjects studied increased blood lactate at low work rates. Many of these patients were able to achieve a physiologic training effect. Though total work was the same, training at a high work rate was more effective than was training at a low work rate. The lower VE requirement to perform exercise was in proportion to the lower lactate level, but the VE decrease for a given decrease in lactate was smaller than that seen in normal subjects (7.2 L/min/mEq/L), apparently because patients with COPD fall to hyperventilate in response to lactic acidosis (PaCO2 does not drop). These findings provide a physiologic rationale for exercise training of patients with COPD.

Acidosis, Lactic↗
PubMed1991

Protective effect and duration of action of formoterol aerosol on exercise-induced asthma.

The short-term protective effect on exercise-induced asthma (EIA) and the duration of action of formoterol, given by metered dose aerosol at a dose of 24 micrograms, were compared with salbutamol (200 micrograms) and placebo in twelve asthmatic EIA-positive patients in a double-blind, placebo-controlled, three period cross-over study. On each treatment day the patients were given one of the drugs or placebo and two exercise tests were performed at the second and at the eighth hour after dosing. Using a standard procedure, exercise was performed by treadmill in well-controlled environmental conditions. In the first test at 2 h a significant difference relative to placebo (p less than 0.001) at each incremental time after exercise (i.e. 5, 10, 15, 20, 30 min) was obtained with both formoterol and salbutamol, without any significant difference between formoterol and salbutamol. After the eighth hour test formoterol still protected against EIA in comparison to both salbutamol and placebo. The effect of salbutamol at this time was not different from placebo. No adverse effects were reported in any treatment group. Formoterol has a long duration of action in protecting against EIA that persisted for eight hours, removing the need to dose with beta 2-agonist before every exercise.

Adrenergic beta-Agonists↗
PubMed1991

[Indications and results of exercise rehabilitation in patients with chronic obstructive lung diseases].

The aim of physical exercise retraining in patients with chronic obstructive lung disease undergoing rehabilitation is to increase the anaerobic work capacity with a rise in VO2 max. Exercise programmes must take into account the duration, frequency and intensity of exercise. In these patients, numerous factors limit physical exercise, including (a) decreased ventilatory capacity and respiratory muscles fatigue; (b) decreased efficacy of the pulmonary gas exchanges; (c) altered pulmonary vascular bed with altered cardiovascular response. The most widely used training methods are walking (or running), practising on a conveyor belt and using an ergometric bicycle. The last named seems to be the best method to evaluate the physiological effects of exercise or for experimental studies. Patients who are fit to participate in a retraining programme must be in a stable period and have a stable pharmacological regimen; they must be subjected to a preliminary exercise test in order to evaluate the main physiological parameters and to obtain information on their tolerance to exercise, on the presence of lactic acidosis and on the degree of hypoxaemia and hypercapnia. In the absence of contra-indications, a training programme can be set up with 30 to 45 minutes of exercise per day at least 3 to 5 times a week during 5 to 8 weeks, with a load amounting to 50-60% of VO2 max. Two questions remain to be answered: (a) is oxygen therapy useful during retraining; (b) what effect has training on survival?

Acidosis, Lactic↗