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Biomedical subjects

C Roussos

Publications and source records attributed to C Roussos.

At least 19 recordsLinked to original sources
PubMed2006

Oxygen kinetics and debt during recovery from expiratory flow-limited exercise in healthy humans.

In healthy subjects expiratory flow limitation (EFL) during exercise can lower O(2) delivery to the working muscles. We hypothesized that if this affects exercise performance it should influence O(2) kinetics at the end of exercise when the O(2) debt is repaid. We performed an incremental exercise test on six healthy males with a Starling resistor in the expiratory line limiting expiratory flow to approximately 1 l s(-1) to determine maximal EFL exercise workload (W (max)). In two more square-wave exercise runs subjects exercised with and without EFL at W (max) for 6 min, while measuring arterial O(2) saturation (% SaO(2)), end-tidal pressure of CO(2) (P (ET)CO(2)) and breath-by-breath O(2) consumption VO2 taking into account changes in O(2) stored in the lungs. Over the last minute of EFL exercise, mean P (ET)CO(2) (54.7 +/- 9.9 mmHg) was significantly higher (P < 0.05) compared to control (41.4 +/- 3.9 mmHg). At the end of EFL exercise %SaO(2) fell significantly by 4 +/- 3%. When exercise stopped, EFL was removed, and we continued to measure VO2. During recovery, there was an immediate step increase in [Formula: see text] so that repayment of EFL O(2) debt started at a higher VO2 than control. Recovery VO2 kinetics after EFL exercise was best characterized by a double-exponential function with fundamental and slow time constants of 27 +/- 11 and 1,020 +/- 305 s, compared to control values of 41 +/- 10 and 1,358 +/- 320 s, respectively. EFL O(2) debt was 52 +/- 22% greater than control (2.19 +/- 0.58 vs. 1.49 +/- 0.38 l). We conclude that EFL exercise increases the O(2) debt and leads to hypoxemia in part due to hypercapnia.

Carbon Dioxide↗
PubMed2006

Effects of rehabilitation on chest wall volume regulation during exercise in COPD patients.

In order to investigate underlying mechanisms, the present authors studied the effect of pulmonary rehabilitation on the regulation of total chest wall and compartmental (ribcage, abdominal) volumes during exercise in patients with chronic obstructive pulmonary disease. In total, 20 patients (forced expiratory volume in one second, mean +/- SEM 39 +/- 3% predicted) undertook high-intensity exercise 3 days x week(-1) for 12 weeks. Before and after rehabilitation, the changes in chest wall (cw) volumes at the end of expiration (EEV) and inspiration (EIV) were computed by optoelectronic plethysmography during incremental exercise to the limit of tolerance (W(peak)). Rehabilitation significantly improved W(peak) (57+/-7 versus 47+/-5 W). In the post-rehabilitation period and at identical work rates, significant reductions were observed in minute ventilation (35.1+/-2.7 versus 38.4+/-2.7 L x min(-1)), breathing frequency (26+/-1 versus 29+/-1 breaths x min(-1)) and EEV(cw) and EIV(cw) (by 182+/-79 and 136+/-37 mL, respectively). Inspiratory reserve volume was significantly increased (by 148+/-70 mL). Volume reductions were attributed to significant changes in abdominal EEV and EIV (by 163+/-59 and 125+/-27 mL, respectively). The improvement in W(peak) was similar in patients who progressively hyperinflated during exercise and those who did not (24 and 26%, respectively). In conclusion, pulmonary rehabilitation lowers chest wall volumes during exercise by decreasing the abdominal volumes. The improvement in exercise capacity following rehabilitation is independent of the pattern of exercise-induced dynamic hyperinflation.

Aged↗
PubMed2006

Obstructive sleep apnoea and oral breathing in patients free of nasal obstruction.

Although there is an association between nasal obstruction, oral breathing and obstructive sleep apnoea syndrome (OSAS), it remains unknown whether increased oral breathing occurs in patients with OSAS who are free of nasal obstruction. The present study evaluated the relationship between breathing route and OSAS in patients without nasal obstruction. The breathing route of 41 snorers (25 male; aged 26-77 yrs) with normal nasal resistance was examined during overnight polysomnography using a nasal cannula/pressure transducer and an oral thermistor. In total, 28 patients had OSAS (apnoeics) and 13 patients were simple snorers. Apnoeics had a higher percentage of oral and oro-nasal breathing epochs. Oral and oro-nasal breathing epochs were positively related with apnoea/hypopnoea index (AHI) and duration of apnoeas/hypopnoeas and inversely related to oxygen saturation. Additionally, oro-nasal breathing epochs correlated with body mass index (BMI). In multiple linear regression analysis, oral breathing epochs were independently related only to AHI (r2 = 0.443), and oro-nasal breathing epochs were independently related to AHI (r2 = 0.736) and BMI (r2 = 0.036). In conclusion, apnoeics spent more time breathing orally and oro-nasally than simple snorers, and the apnoea/hypopnoea index is a major determinant of the time spent breathing orally and oro-nasally.

Body Mass Index↗
PubMed2006

Gender differences on polysomnographic findings in Greek subjects with obstructive sleep apnea syndrome.

BACKGROUND AND PURPOSE: Studies from North American clinics have reported that females with obstructive sleep apnea syndrome (OSAS) are about the same age as males but are heavier, have less severe apnea and make up a much smaller proportion of cases. We examined polysomnographic differences between Greek men and women with OSAS in order to study the influence of gender on clinical presentation and laboratory findings. PATIENTS AND METHODS: This retrospective study included a cohort of 1,010 Greek patients (844 males, 166 females) diagnosed with OSAS by overnight polysomnography (PSG), who were referred to the Sleep Disorders Center of Evangelismos Hospital, Athens Medical School, University of Athens. All patients were studied over a period of three consecutive years, during which time clinical and polysomnography (PSG) findings were compared. RESULTS: Body mass index (BMI) was similar in men and women with OSAS (BMI=31.6+/-5.5kg/m(2) in men versus BMI=32.5+/-8.1 (SD) kg/m(2) in women). Female patients were significantly older than male patients (56.9+/-10.6 versus 50.6+/-11.7 year, P=0.001). The mean apnea-hypopnea index (AHI) during total sleep time was higher in men than in women (42.4+/-28.2 versus 33.2+/-27.7 events/h, P<0.001). The AHI in non-rapid eye movement (NREM) sleep was higher in men than in women (42.9+/-28.9 versus 32.6+/-28.7 events/h, P<0.001), but in rapid eye movement (REM) sleep AHI was similar in men and women (36.0+/-23.3 versus 34.9+/-25.4 events/h). Forty percent of men had AHI-REM sleep >AHI-NREM compared to 62% of women, and the difference between REM and NREM-AHI was significantly less in men than in women (14.21+/-11.18 versus 19.76+/-13.43 events/h, P<0.001)). Several aspects of sleep were worse in women versus men: sleep efficiency index was lower (79.4+/-16.1% versus 85.1+/-12.5%, P<0.001); sleep onset latency (27.7+/-27.7 versus 17.9+/-18.1min, P<0.001), and REM onset latency (161.5+/-76.2 versus 145.7+/-71.4min, P<0.018) were longer; wake time after sleep onset (WASO) was also greater in women (42.6+/-46.5 versus 30.7+/-34.9min, P<0.003). CONCLUSIONS: In Greek subjects with OSAS, there was no difference in BMI, and female patients were significantly older than male patients. OSAS was diagnosed in men five times more often than in women. AHI was greater in men than in women, but women are more likely than men to have a higher AHI in REM than NREM. Sleep quality is worse in female than in male patients.

Adolescent↗
PubMed2006

Static pressure-volume curves and body posture in severe chronic bronchitis.

Based on prior data, the current authors hypothesised that beneficial pronation effects on gas exchange and respiratory mechanics might be maximised in severely hyperinflated chronic bronchitis patients. The current authors also sought to elucidate underlying mechanisms and to determine whether pronation effects are reflected by postural changes in inspiratory pressure-volume (P-V) curve characteristics. A total of 16 mechanically ventilated patients (for 16-36 h) with chronic bronchitis exacerbation were studied in pre-prone semirecumbent (SREC), prone and post-prone SREC postures. Static respiratory system intrinsic positive end-expiratory pressure (PEEPi,rs) was >12 cmH2O. Haemodynamics, partitioned respiratory mechanics, gas exchange, and lung volumes were determined at zero external positive end-expiratory pressure. P-V curves were constructed from functional residual capacity. End-expiratory lung volume exceeded opening volume. Prone position versus pre-prone SREC resulted in 20% reduced pressure at the lower inflection point (LIP) and 17% increased volume at the upper inflection point of the lung P-V curve, improved lung mechanics and volumes, oxygenation, and carbon dioxide arterial tension (Pa,CO2). In multiple linear regression, postural decreases in PEEPi,rs and additional lung resistance independently predicted postural decreases in lung LIP pressure and Pa,CO2), respectively. In conclusion, in severely hyperinflated patients, pronation reduces lung lower inflection point pressure and increases lung upper inflection point volume. Pronation effects on ventilation homogeneity and carbon dioxide arterial tension are maximised, implying that pronation can be useful during early controlled ventilation.

Aged↗
PubMed2005

Patterns of dynamic hyperinflation during exercise and recovery in patients with severe chronic obstructive pulmonary disease.

BACKGROUND: Not all patients with severe chronic obstructive pulmonary disease (COPD) progressively hyperinflate during symptom limited exercise. The pattern of change in chest wall volumes (Vcw) was investigated in patients with severe COPD who progressively hyperinflate during exercise and those who do not. METHODS: Twenty patients with forced expiratory volume in 1 second (FEV(1)) 35 (2)% predicted were studied during a ramp incremental cycling test to the limit of tolerance (Wpeak). Changes in Vcw at the end of expiration (EEVcw), end of inspiration (EIVcw), and at total lung capacity (TLCVcw) were computed by optoelectronic plethysmography (OEP) during exercise and recovery. RESULTS: Two significantly different patterns of change in EEVcw were observed during exercise. Twelve patients had a progressive significant increase in EEVcw during exercise (early hyperinflators, EH) amounting to 750 (90) ml at Wpeak. In contrast, in all eight remaining patients EEVcw remained unchanged up to 66% Wpeak but increased significantly by 210 (80) ml at Wpeak (late hyperinflators, LH). Although at the limit of tolerance the increase in EEVcw was significantly greater in EH, both groups reached similar Wpeak and breathed with a tidal EIVcw that closely approached TLCVcw (EIVcw/TLCVcw 93 (1)% and 93 (3)%, respectively). EEVcw was increased by 254 (130) ml above baseline 3 minutes after exercise only in EH. CONCLUSIONS: Patients with severe COPD exhibit two patterns during exercise: early and late hyperinflation. In those who hyperinflate early, it may take several minutes before the hyperinflation is fully reversed after termination of exercise.

Exercise↗
PubMed2005

Respiratory muscle performance with stretch-shortening cycle manoeuvres: maximal inspiratory pressure-flow curves.

AIM: To test the hypothesis that the maximal inspiratory muscle (IM) performance, as assessed by the maximal IM pressure-flow relationship, is enhanced with the stretch-shortening cycle (SSC). METHODS: Maximal inspiratory flow-pressure curves were measured in 12 healthy volunteers (35 +/- 6 years) during maximal single efforts through a range of graded resistors (4-, 6-, and 8-mm diameter orifices), against an occluded airway, and with a minimal load (wide-open resistor). Maximal inspiratory efforts were initiated at a volume near residual lung volume (RV). The subjects exhaled to RV using slow (S) or fast (F) manoeuvres. With the S manoeuvre, they exhaled slowly to RV and held the breath at RV for about 4 s prior to maximal inspiration. With the F manoeuvre, they exhaled rapidly to RV and immediately inhaled maximally without a post-expiratory hold; a strategy designed to enhance inspiratory pressure via the SSC. RESULTS: The maximal inspiratory pressure-flow relationship was linear with the S and F manoeuvres (r2 = 0.88 for S and r2 = 0.88 for F manoeuvre, P < 0.0005 in all subjects). With the F manoeuvre, the pressure-flow relationship shifted to the right in a parallel fashion and the calculated maximal power increased by approximately 10% (P < 0.05) over that calculated with the S manoeuvre. CONCLUSION: The maximal inspiratory pressure-flow capacity can be enhanced with SSC manoeuvres in a manner analogous to increases in the force-velocity relationship with SSC reported for skeletal muscles.

Adult↗
PubMed2005

Does soluble triggering receptor expressed on myeloid cells-1 play any role in the pathogenesis of septic shock?

In order to define the significance of soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) upon progression from sepsis or severe sepsis to septic shock a prospective study was designed with 90 enrolled patients with septic syndrome due to ventilator-associated pneumonia. Blood was sampled on seven consecutive days upon initiation of symptoms and concentrations of tumour necrosis factor-alpha (TNFalpha), interleukin-6 (IL-6), IL-8 and sTREM-1 were estimated in serum by an enzymeimmunoassay. No differences in concentrations of TNFalpha, IL-6 and IL-8 were found between patients with sepsis, severe sepsis and septic shock on the first day of presentation of symptoms. Patients presenting with septic shock had concentrations of sTREM-1 significantly higher than both patients with sepsis and severe sepsis on the first day; no difference was found between patients with sepsis and severe sepsis. A positive correlation was detected between sTREM-1 and the white blood cell count. Serum levels of sTREM-1 were significantly lower in patients where VAP resolved compared to those where VAP did not resolve; similar findings were noted between patients who eventually survived and those who died. IL-6 followed the kinetics of sTREM-1 in correlation to patients's prognosis; levels of TNFalpha and IL-8 were unrelated to prognosis. It is concluded that sTREM-1 is particularly increased upon evolution from sepsis or severe sepsis to septic shock. Its sustained increase is an indication of poor outcome. The underlined pathophysiological role of sTREM-1 for the transition from sepsis or severe sepsis to septic shock might constitute a novel target for immunomodulatory therapy.

Aged↗
PubMed2005

The participation of health professionals in a smoking-cessation programme positively influences the smoking cessation advice given to patients.

This study assessed the degree of smoking cessation advice given by health professionals, before and after their participation in a smoking cessation study using bupropion-sustained release (bupropion SR, Zyban). A total of 690 physicians and nurses who had smoked an average of 10 cigarettes/day over the previous year and were motivated to quit smoking, were randomised in a double-blind manner to receive bupropion SR (days 1-3, 150 mg/day; days 4-49, 150 mg twice daily) or placebo for 7 weeks, with follow-up to week 52. All subjects received regular follow-up and brief motivational support throughout the study. Questions regarding their smoking cessation advice formed part of the study, with the aim of determining whether study participants became more proactive with their smoking cessation advice. A positive shift from baseline to end of study was observed with respect to the advice and support they gave to their smoking patients. These changes were not related to study treatment or current smoking status. An increase in advising patients to quit smoking and in offering cessation counselling was observed. Participation in a smoking-cessation study by physicians and nurses who smoke has a positive effect, regardless of study medication, in smoking cessation advice and counselling given to their patients.

Bupropion↗
PubMed2005

Prone position improves expiratory airway mechanics in severe chronic bronchitis.

Based on lung parenchyma-airways' interdependence, the present authors hypothesised that prone positioning may reduce airway resistance in severe chronic bronchitis. A total of 10 anaesthetised/mechanically ventilated patients were enrolled. Partitioned respiratory system (RS) mechanics during iso-flow experiments (flow = 0.91 L x s(-1), tidal volume (VT) varied within 0.2-1.2 L), haemodynamics, gas-exchange, expiratory airway resistance (Raw,exp), functional residual capacity (FRC), change in FRC (DeltaFRC), end-expiratory lung volume (EELV), expiratory airway resistance at EELV (Raw,exp,EELV), intrinsic positive end-expiratory pressure (PEEPi), and mean end-expiratory flow were determined in baseline semirecumbent (SRBAS), prone, and post-prone semirecumbent (SRPP) postures. Pronation versus SRBAS resulted in significantly reduced Raw,exp (at VT > or =0.8 L), Raw,exp,EELV (18.3+/-1.4 versus 31.6+/-2.6 cm H2O x L(-1) x s(-1)), inspiratory airway resistance (at VT > or =1.0 L), static lung elastance (at VT < or =0.6 L), "additional" RS/lung resistance (at a range of VTs), DeltaFRC (0.35+/-0.03 versus 0.47+/-0.03 L), EELV (4.92+/-0.49 versus 5.65+/-0.65 L), RS/lung PEEPi (6.7+/-1.1/5.4+/-0.6 versus 8.9+/-1.7/7.8+/-1.1 cm H2O), mean end-expiratory flow (63.9+/-4.2 versus 47.9+/-4.0 mL x s(-1)), and shunt fraction (0.16+/-0.03 versus 0.21+/-0.03); benefits were reversed in SRPP. In severe chronic bronchitis, prone positioning reduces airway resistance and dynamic hyperinflation.

Aged↗
PubMed2005

Prone position reduces lung stress and strain in severe acute respiratory distress syndrome.

The present authors hypothesised that in severe acute respiratory distress syndrome (ARDS), pronation may reduce ventilator-induced overall stress (i.e. transpulmonary pressure (P(L))) and strain of lung parenchyma (i.e. tidal volume (V(T))/end-expiratory lung volume (EELV) ratio), which constitute major ventilator-induced lung injury determinants. The authors sought to determine whether potential pronation benefits are maintained in post-prone semirecumbent (SR(PP)) posture under pressure-volume curve-dependent optimisation of positive end-expiratory pressure (PEEP). A total of 10 anesthetised/paralysed, mechanically ventilated (V(T) = 9.0+/-0.9 mL.kg(-1) predicted body weight; flow = 0.91+/-0.04 L.s(-1); PEEP = 9.4+/-1.3 cmH(2)O) patients with early/severe ARDS were studied in pre-prone semirecumbent (SR(BAS)), prone, and SR(PP) positions. Partitioned respiratory mechanics were determined during iso-flow (0.91 L.s(-1)) experiments (V(T) varied within 0.2-1.0 L), along with haemodynamics, gas exchange, and EELV. Compared with SR(BAS), pronation/SR(PP) resulted in reduced peak/plateau P(L) at V(T)s> or =0.6 L; static lung elastance and additional lung resistance decreased and chest wall elastance (in prone position) increased; EELV increased (23-33%); V(T)/EELV decreased (27-33%); arterial oxygen tension/inspiratory oxygen fraction and arterial carbon dioxide tension improved (21-43/10-14%, respectively), and shunt fraction/physiological dead space decreased (21-50/20-47%, respectively). In early/severe acute respiratory distress syndrome, pronation under positive end-expiratory pressure optimisation may reduce ventilator-induced lung injury risk. Pronation benefits may be maintained in post-prone semirecumbent position.

Adult↗
PubMed2004

Acute mediastinitis: spectrum of computed tomography findings.

The objective of this study was to describe CT findings and to determine the diagnostic value of CT in diagnosis of acute mediastinitis. CT findings were retrospectively studied in 40 patients with suspected acute mediastinitis, including 28 postoperative patients, five with acute descending necrotizing mediastinitis (ADNM), and seven with suspected post-traumatic perforation of the esophagus. Findings included increased attenuation of mediastinal fat (100%), localized mediastinal fluid collections (55%), free gas bubbles in the mediastinum (57.5%), mediastinal lymph nodes (35%), pericardial effusions (27.5%), pleural effusions (85%), lung infiltrates (35%), sternal dehiscence (40%), and pleuromediastinal fistula (2.5%). The sensitivity and specificity of CT in postoperative patients in the first 17 days was 100% and 33% respectively, and after day 17, 100% and 90%. In patients with ADNM sensitivity was 100% while in patients with suspected esophageal perforation sensitivity and specificity were 100%. CT is a highly sensitive technique for the detection of mediastinitis of various causes. For the postoperative patients there is clear time dependence for CT interpretation and accuracy. In patients with suspected ADNM, and traumatic esophageal perforation CT is highly specific early after clinical presentation.

Acute Disease↗
PubMed2004

Pulmonary endothelium in acute lung injury: from basic science to the critically ill.

BACKGROUND: Pulmonary endothelium is an active organ possessing numerous physiological, immunological, and metabolic functions. These functions may be altered early in acute lung injury (ALI) and further contribute to the development of acute respiratory distress syndrome (ARDS). Pulmonary endothelium is strategically located to filter the entire blood before it enters the systemic circulation; consequently its integrity is essential for the maintenance of adequate homeostasis in both the pulmonary and systemic circulations. Noxious agents that affect pulmonary endothelium induce alterations in hemodynamics and hemofluidity, promote interactions with circulating blood cells, and lead to increased vascular permeability and pulmonary edema formation. OBJECTIVE: We highlight pathogenic mechanisms of pulmonary endothelial injury and their clinical implications in ALI/ARDS patients.

Capillary Permeability↗
PubMed2004

A prospective study on lung toxicity in patients treated with gemcitabine and carboplatin: clinical, radiological and functional assessment.

BACKGROUND: Small series and retrospective studies have suggested that treatment with gemcitabine may be associated with pulmonary toxicity. However, a prospective evaluation of cancer patients treated with gemcitabine-based chemotherapy without neoplastic involvement of the thorax and without administration of radiotherapy has not been performed. PATIENTS AND METHODS: To investigate this issue, 41 consecutive patients receiving gemcitabine and carboplatin underwent prospective evaluation of lung function, which included pulmonary symptoms, pulmonary function tests, arterial blood gases and radiographic studies. Assessment was performed before and after completion of chemotherapy in all patients. Patients with a substantial decline in diffusion capacity for carbon monoxide (DLCO), defined as a drop of > or = 20%, were reassessed 2 months later. RESULTS: After chemotherapy, there were no significant changes in forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC ratio, alveolar volume or total lung capacity. In contrast, there was a significant decline in DLCO (73 +/- 22 versus 67 +/- 24% predicted; P = 0.017) and in carbon monoxide transfer coefficient (KCO) (89 +/- 24 versus 80 +/- 24% predicted; P = 0.004). Arterial blood gases did not change following treatment. Ten of the 41 patients (24%) exhibited a substantial decline in DLCO, which, however, recovered within 2 months (DLCO at baseline, immediately after therapy and at 2 months after completion of treatment, 84 +/- 14, 58 +/- 16 and 77 +/- 17% predicted, respectively; P < 0.001; baseline DLCO versus DLCO at 2 months, P > 0.05). Four of the 41 patients (10%) experienced dyspnea, which was self-limiting, with the exception of one patient who developed interstitial lung fibrosis. Among the various risk factors examined, older age, female gender and lower baseline DLCO were associated with more profound changes in DLCO post-treatment. CONCLUSIONS: This prospective analysis showed that the combination of gemcitabine and carboplatin induces a significant, but reversible, decrease in diffusion capacity, which is mostly asymptomatic. Thus, this regimen is safe as regards clinically significant lung toxicity.

Aged↗
PubMed2004

Expiratory flow limitation in morbidly obese postoperative mechanically ventilated patients.

Although obesity promotes tidal expiratory flow limitation (EFL), with concurrent dynamic hyperinflation (DH), intrinsic PEEP (PEEPi) and risk of low lung volume injury, the prevalence and magnitude of EFL, DH and PEEPi have not yet been studied in mechanically ventilated morbidly obese subjects. In 15 postoperative mechanically ventilated morbidly obese subjects, we assessed the prevalence of EFL [using the negative expiratory pressure (NEP) technique], PEEPi, DH, respiratory mechanics, arterial oxygenation and PEEPi inequality index as well as the levels of PEEP required to abolish EFL. In supine position at zero PEEP, 10 patients exhibited EFL with a significantly higher PEEPi and DH and a significantly lower PEEPi inequality index than found in the five non-EFL (NEFL) subjects. Impaired gas exchange was found in all cases without significant differences between the EFL and NEFL subjects. Application of 7.5 +/- 2.5 cm H2O of PEEP (range: 4-16) abolished EFL with a reduction of PEEPi and DH and an increase in FRC and the PEEPi inequality index but no significant effect on gas exchange. The present study indicates that: (a) on zero PEEP, EFL is present in most postoperative mechanically ventilated morbidly obese subjects; (b) EFL (and concurrent risk of low lung volume injury) is abolished with appropriate levels of PEEP; and (c) impaired gas exchange is common in these patients, probably mainly due to atelectasis.

Adult↗