Quality of life and smoking among industrial workers in Greece.

BACKGROUND: Smoking is a predictor of quality of life, while socio-economic factors influence the prevalence of smoking habits. Occupational medical research has been fairly late in coming to study quality of life aspects in working populations. OBJECTIVES: The aim of the study is the assessment of smoking prevalence among blue- and white-collar workers industrial workers in Greece and its impact on health-related quality of life. METHODS: In a cross-sectional study the Euro-Qol 5D questionnaire was been used in a random sample of 472 blue and white-collar heavy industry workers. RESULTS: 57% of the study population were current smokers. The difference in prevalence of smoking across all the examined socio-demographic variables (sex, age, education and occupation) was not statistically significant. Smoking had a significant impact on the health-related quality of life. Smokers recorded significant lower scores (74.9) in the overall Visual Analogue Scale in comparison with non-smokers (79.1), (p = 0.007). Further analysis revealed that age, smoking and education were significant predictors of VAS score. A non-significant contribution was found for occupation and sex. Smokers reported significantly higher rates of problems regarding mobility, self-care and anxiety/depression than non-smokers. Logistic regression analysis showed an independent impact of smoking on mobility, self-care and anxiety/depression level. CONCLUSIONS: Smoking is a significant hazard and a strong predictor of poor quality of life among the blue- and white-collar workers under study. Anti-smoking policies integrated into a broader context of occupational health and safety at work could reduce smoking rates and thus improve worker's quality of life.

Gastrointestinal hormones and short-term nutritional schedules in critically ill patients.

BACKGROUND/AIMS: The purpose of the study is to evaluate the gastrointestinal hormone response in critically ill patients under different nutritional schedule (enteral vs. total parenteral) of short duration. METHODOLOGY: Twenty-one sedated and mechanically ventilated patients were nourished with continuous nasogastric schedule (Group A, 11 patients), or with total parenteral nutrition (Group B, 10 patients). Serum concentrations of gastrin, cholecystokinin, vasoactive intestinal peptide, neurotensin, and bombesin, were measured on the 2nd, 3rd and the 5th day of patients' admission, with radioimmunoassay methods. RESULTS: Changes of hormones concentrations were not significant either between the three measurements in each group or between the two groups at the same hospitalization day. CONCLUSIONS: The short-term parenteral nutrition in critically ill patients does not exert a different influence on the serum concentrations of gastrin, cholecystokinin, vasoactive intestinal peptide, neurotensin, and bombesin, compared to enteral nutrition. This conclusion is of clinical interest since the short-term administration of total parenteral nutrition is very often necessary during hospitalization in the intensive care unit.

Non-linear evaluation of respiratory mechanics during laparoscopic cholecystectomy.

BACKGROUND/AIMS: Laparoscopic cholecystectomy is accompanied by significant increase of the respiratory system elastic and resistive properties. These changes are completely abolished after peritoneal deflation. In the present study we examine the volume and flow dependence of respiratory mechanics during four operation phases. METHODOLOGY: Airway pressure and flow were recorded from 17 patients undergoing laparoscopic cholecystectomy. Measurements were done at 4 distinct phases: 1) Before the induction of pneumoperitoneum. 2) Five minutes after pneumoperitoneum induction at Trendelenburg position. 3) Five minutes after positioning the patient at reverse. Trendelenburg. 4) Five minutes after the peritoneal deflation. Data of airway pressure, flow and volume were treated according to the non-linear regression model: Paw = E1.V + E2.V2 + k1.V' + k2.V'. |V'| + k3.V.V' + EEP. RESULTS: The induction of pneumoperitoneum results in: Significant increase of linear elastance and resistance and significant decrease of flow and volume dependence of resistance. No significant changes are noted in volume dependence of elastance and end-expiratory pressure. CONCLUSIONS: The pneumoperitoneum and not the body position causes the changes in respiratory mechanics and their dependencies during laparoscopic cholecystectomy, which, although important, do not predispose to major risks (lung overdistension, alveolar collapse) and they are reversed after peritoneal deflation.

Effects of PEEP on inspiratory and expiratory mechanics in adult respiratory distress syndrome.

The purpose of the present study was to assess the mechanical behavior of the respiratory system separately during inspiration and expiration in adult respiratory distress syndrome (ARDS) and the influence of PEEP on any phasic variations ofthe mechanical respiratory parameters. Airways pressure (P), flow (V), and volume (V) signals were recorded in nine patients with ARDS and 10 patients without known respiratory disorder (control group). All patients were artificially ventilated at three levels of positive end-expiratory pressure (PEEP): 0, 5, and 10 hPa. Data were analyzed separately for inspiratory and expiratory records using multiple linear regression analysis (MLRA) according to the equation: P=Ers V+Rrs V'+P0, where Ers and Rrs represent, respectively, the intubated respiratory system elastance and resistance, and P0 the end-expiratory pressure. In the ARDS group expiratory Ers (ErsEXP=45.58 +/- 4.24 hPa/L) was substantially higher (p<0.01) than inspiratory Ers (ErsINSP=36.76 +/- 2.55) with a marked effect of applied PEEP in diminishing the difference between ErsEXP and ErsINSP (p<0.01). For the ARDS group inspiratory Rrs (RrsINSP) decreased significantly with increasing PEEP (PEEP=0: RrsINSP=16.43, PEEP=10: RrsINSP=13.28, p<0.01). The found differences between ErsEXP and ErsINSP could be attributable to an influence of mechanical ventilation by positive airway pressure on pulmonary edemaand interstitial fluid during the inspiratory phase of the respiratory cycle.

Evaluation of the end-expiratory pressure by multiple linear regression and Fourier analysis in humans.

This study was designed to compare the end-expiratory pressure (EEP) during mechanical ventilation (MV) measured dynamically (EEPdyn), by multiple linear regression (MLR) of the airway pressure (Pao) vs volume (V) and flow (V') and after Fourier analysis (FA) of the Pao and V'. Pao and V' were recorded from 32 ICU patients (II without respiratory disease, 10 COPD, II ARDS) under MV, at three levels of PEEPe (0, 5 and 10 hPa). Volume was calculated by numerical integration of V'. Data were analysed by MLR and FA, while the actual value of EEPdyn was recognised on the Pao signal at zero V' and V. EEPdyn, EEPMLR and EEPFA were compared for all patients, for each group of patients and for every level of applied PEEPe. Despite the different evaluation of respiratory mechanics between MLR and FA, the EEP values were always not significantly different between the three applied methods (P > 0.05). A high degree of correlation was found between them, taken two at a time (r > 0.99, P < 0.001). Two non-invasive analytical methods for the evaluation of respiratory mechanics during MV, MLR and FA offer a reliable and clinically useful estimation of EEP during MV.

Linear and nonlinear analysis of pressure and flow during mechanical ventilation.

OBJECTIVE: Linear modeling as a method of exploring respiratory mechanics during mechanical ventilation, was compared to nonlinear modeling for flow dependence of resistance in three distinct groups of patients, those with: (a) normal respiratory function (NRF), (b) chronic obstructive pulmonary disease (COPD), or (c) adult respiratory distress syndrome (ARDS). DESIGN AND PATIENTS: Airways opening pressure (Pao), flow (V'), and volume (V) signals were recorded in 32 ICU mechanically ventilated patients, under sedation and muscle relaxation (10 NRF, 11 COPD, 11 ARDS). All patients were ventilated with controlled mandatory ventilation mode at three levels of end-expiratory pressure (PEEPe): 0, 5, and 10 hPa. Data were analyzed according to: (a) Pao = PE + Ers V + Rrs V' and (b) Pao = PE + Ers V + k1V' + k2¿V'¿V'; where Ers and Rrs represent the intubated respiratory system (RS) elastance and resistance, k1 and k2 the linear and the nonlinear RS resistive coefficients, and PE the end-expiratory pressure. The model's goodness of fit to the data was evaluated by the root mean square difference of predicted minus measured Pao values. RESULTS: NRF data fit both models well at all PEEPe levels. ARDS and particularly COPD data fit the nonlinear model better. Values of k2 were often negative in COPD and ARDS groups, and they increased in parallel with PEEPe. A gradual increase in PEEPe resulted in better fit of ARDS and COPD data to both models. CONCLUSIONS: The model of V' dependence of resistance is more suitable for the ARDS and particularly the COPD groups. PEEP tends to diminish the V' dependence of respiratory resistance during the respiratory cycle, particularly in the COPD group, probably through an indirect effect of the increased lung volume.

The immediate effect of a Boston brace on lung volumes and pulmonary compliance in mild adolescent idiopathic scoliosis.

Idiopathic scoliosis (IS) is known to result in lung volume and pulmonary compliance reduction. Boston brace treatment of IS is an additional factor causing restrictive respiratory syndrome due to external chest wall compression. Nevertheless, the immediate effect of Boston bracing on the pulmonary compliance of scoliotic patients has not been studied systematically. Spirometric and plethysmographic lung volumes, static lung compliance (C(ST)(L)) and specific lung compliance (C(ST)(L)/functional residual capacity) of 15 scoliotic adolescents (14 females and 1 male, of mean age 14.1+/-1.67 years, with mean Cobb angle 24.1 degrees+/-7.88 degrees) were recorded twice, in a random sequence: once without the Boston brace (nBB) and once immediately after wearing the brace (BB). Our findings showed that bracing reduced vital capacity, residual volume, functional residual capacity (FRC), total lung capacity, and forced expiratory volume in 1s in a proportional and significant way (P < 0.001). C(ST)(L) was also significantly reduced (P < 0.001), but C(ST)(L)/FRC remained unaltered. All BB and nBB indices were highly correlated. We concluded that Boston bracing in IS patients results in an immediate, predictable, and uniform reduction of lung volumes and pulmonary compliance. The reduction of C(ST)(L) under bracing conditions was related to the decrease of lung volume; the C(ST)(L)/FRC remained unaltered.

Effect of posture on ventilation and breathing pattern during room air breathing at rest.

We measured minute ventilation (VE), tidal volume (VT), mean inspiratory flow (VT/TI), and occlusion pressure (P.1) in 10 resting subjects breathing room air, in sitting, supine, right and left lateral positions, and compared them with corresponding data on static lung compliance [Cst(l)], dynamic lung compliance [Cdyn(l)], and pulmonary flow resistance [R(l)]. Highest values for VT, VE, VT/TI, P.1, and effective inspiratory impedance [P.1/(VT/Ti)] were observed in the supine posture. Values for P.1 and P.1/(VT/TI in lateral decubitus were intermediate to those obtained when seated and supine. While the increases in P.1 and P.1/(VT/TI) in recumbent postures were qualitatively similar to the decrease in Cdyn(l) and increase in R(l), there was no significant correlation between them, probably reflecting the complex relationship between P.1/(VT/TI) and lung compliance and resistance, as the former, in addition to lung mechanics, also depends on the shape of the inspiratory driving pressure wave, the active inspiratory impedance, the mechanics of the chest wall, and the duration of inspiration.

Immediate response to resistive loading in anesthetized humans.

In eight spontaneously breathing anesthetized subjects (halothane: approximately 1 minimal alveolar concn; 70% N2O-30% O2), we determined 1) the inspiratory driving pressure by analysis of the pressure developed at the airway opening (Poao) during inspiratory efforts against airways occluded at end expiration; 2) the active inspiratory impedance; and 3) the immediate (first loaded breath) response to added inspiratory resistive loads (delta R). Based on these data we made model predictions of the immediate tidal volume response to delta R. Such predictions closely fitted the experimental results. The present investigation indicates that 1) in halothane-anesthetized humans the shape of the Poao wave differs from that in anesthetized animals, 2) the immediate response to delta R is not associated with appreciable changes in intensity, shape, and timing of inspiratory neural drive but depends mainly on intrinsic (nonneural) mechanisms; 3) the flow-dependent resistance of endotracheal tubes must be taken into account in studies dealing with increased neuromuscular drive in intubated subjects; and 4) in anesthetized humans Poao reflects the driving pressure available to produce the breathing movements.

Partitioning of respiratory mechanics in halothane-anesthetized humans.

In five spontaneously breathing anesthetized subjects [halothane approximately 1 minimal alveolar concentration (MAC), 70% N2O, 30% O2], flow, changes in lung volume, and esophageal and airway opening pressure were measured in order to partition the elastance (Ers) and flow resistance (Rrs) of the total respiratory system into the lung and chest wall components. Ers averaged (+/- SD) 23.0 +/- 4.9 cmH2O X l-1, while the corresponding values of pulmonary (EL) and chest wall (EW) elastance were 14.3 +/- 3.2 and 8.7 +/- 3.0 cmH2O X l-1, respectively. Intrinsic Rrs (upper airways excluded) averaged 2.3 +/- 0.2 cmH2O X l-1 X s, the corresponding values for pulmonary (RL) and chest wall (RW) flow resistance amounting to 0.8 +/- 0.4 and 1.5 +/- 0.5 cmH2O X l-1 X s, respectively. Ers increased relative to normal values in awake state, mainly reflecting increased EL. Rw was higher than previous estimates on awake seated subjects (approximately 1.0 cmH2O X l-1 X s). RL was relatively low, reflecting the fact that the subjects had received atropine (0.3-0.6 mg) and were breathing N2O. This is the first study in which both respiratory elastic and flow-resistive properties have been partitioned into lung and chest wall components in anesthetized humans.

Measurement of pleural pressure with esophageal balloon in anesthetized humans.

Simultaneous measurement of tracheal and esophageal pressures during occluded inspiratory efforts (occlusion test) was used to assess the validity of the esophageal balloon technique in anesthetized supine subjects. Ten ASA 1 patients undergoing general anesthesia (halothane 1 MAC, nitrous oxide 70%, and oxygen) for minor surgery were studied. Esophageal pressure (Pes) was measured using a 5-cm-long balloon and was plotted against tracheal pressure (Pt). Occlusion tests were performed at end expiration with the balloon top positioned 5, 10, 15, and 20 cm above the cardia. The results show that with the balloon positioned at the classical level of 10 cm above the cardia, the difference between delta Pes and delta Pt did not exceed 8% in seven of 10 subjects. In the remaining three, however, the difference between delta Pes and delta Pt ranged between +20% and -40%. By repositioning the balloon to 5 or 15 cm above the cardia, a locus was found in all subjects where the difference is less than 10%. We conclude that the esophageal balloon technique can be used in anesthetized supine subjects to give reliable measurements of changes in pleural pressure, provided that it is validated with the occlusion test.

Respiratory mechanics during halothane anesthesia and anesthesia-paralysis in humans.

In six spontaneously breathing anesthetized subjects [halothane approximately 1 maximum anesthetic concentration (MAC), 70% N2O-30% O2], we measured flow (V), volume (V), and tracheal pressure (Ptr). With airway occluded at end-inspiration tidal volume (VT), we measured Ptr when the subjects relaxed the respiratory muscles. Dividing relaxed Ptr by VT, total respiratory system elastance (Ers) was obtained. With the subject still relaxed, the occlusion was released to obtain the V-V relationship during the ensuing relaxed expiration. Under these conditions, the expiratory driving pressure is V X Ers, and thus the pressure-flow relationship of the system can be obtained. By subtracting the flow resistance of equipment, the intrinsic respiratory flow resistance (Rrs) is obtained. Similar measurements were repeated during anesthesia-paralysis (succinylcholine). Ers averaged 23.9 +/- 4 (+/- SD) during anesthesia and 21 +/- 1.8 cmH2O X 1(-1) during anesthesia-paralysis. The corresponding values of intrinsic Rrs were 1.6 +/- 0.7 and 1.9 +/- 0.9 cmH2O X 1(-1) X s, respectively. These results indicate that Ers increases substantially during anesthesia, whereas Rrs remains within the normal limits. Muscle paralysis has no significant effect on Ers and Rrs. We also provide the first measurements of inspiratory muscle activity and related negative work during spontaneous expiration in anesthetized humans. These show that 36-74% of the elastic energy stored during inspiration is wasted in terms of negative inspiratory muscle work.

Active inspiratory impedance in halothane-anesthetized humans.

We have used the method of Siafakas et al. (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 51: 109-121, 1981) to determine active elastance (E'rs) and flow resistance (R'rs) of the respiratory system in eight spontaneously breathing humans anesthetized with halothane. From measurements of flow (V) and volume (V) during unoccluded inspirations and of tracheal pressure (P0tr) during subsequent inspirations with the airways occluded at end expiration, we were able to compute E'rs and R'rs as slopes and intercepts of the following function: -P0tr/V = R'rs + E'rsV/V. These measurements were repeated during inspirations loaded with a series of linear flow resistances (delta R). Neither E'rs nor R'rs was significantly affected by delta R. On the average E'rs and R'rs were, respectively, 34.4 and 16.7% higher than the corresponding passive elastance and flow resistance of the respiratory system, indicating that during active breathing the internal impedance of the respiratory system increases. This provides an internal mechanism by which passive loads are compensated.

Lung mechanics in sitting and horizontal body positions.

We measured lung compliance, pulmonary flow-resistance, and expiratory reserve volume (ERV) in ten healthy young adults in sitting, supine, and lateral positions. Average lung compliance was 0.21 in sitting, 0.19 in lateral and 0.16 L.cm H2O-1 in supine positions. The change was significant (p less than 0.01) between sitting and supine position. Flow-resistance increased from 1.78 in sitting to 2.5 cm H2O.L-1.s (p less than 0.001) in lateral positions, and did not increase further in the supine posture in spite of a 35 percent decrease in ERV (p less than 0.001). Since it is known that lower airways resistance increases with decreasing lung volume, the lack of change in flow-resistance when shifting from lateral to supine posture suggests that upper airways flow-resistance (larynx and oropharynx) is greater in the lateral decubitus than in the supine positions. The decrease of lung compliance in horizontal postures probably reflects increased pulmonary blood volume and small airways closure.

A simple method for assessing the validity of the esophageal balloon technique.

The validity of the conventional esophageal balloon technique as a measure of pleural pressure was tested in 10 subjects in sitting, supine, and lateral positions by occluding the airways at end-expiration and measuring the ratio of changes in esophageal (delta Pes) and mouth pressure (delta Pm) during the ensuing spontaneous occluded inspiratory efforts. Similar measurements were also made during static Mueller maneuvers. In both tests, delta Pes/delta Pm values were close to unity in sitting and lateral positions, whereas in the supine position, substantial deviations from unity were found in some instances. However, by repositioning the balloon to different levels in the esophagus, even in these instances a locus could be found where the delta Pes/delta Pm ratio was close to unity. No appreciable phase difference between delta Pes and delta Pm was found. We conclude that by positioning the balloon according to the "occlusion test" procedure, valid measurements of pleural pressure can be obtained in all the tested body positions.