Paolo Paredi

Raised levels of exhaled carbon monoxide are associated with an increased expression of heme oxygenase-1 in airway macrophages in asthma: a new marker of oxidative stress

BACKGROUND Chronic inflammatory diseases are associated with an increased production of oxidants. Induction of a stress protein, heme oxygenase (HO) HO-1, is a cytoprotective mechanism against oxidative cellular injury. HO-1 catabolises heme to bilirubin, free iron, and carbon monoxide (CO). METHODS Exhaled CO and sputum bilirubin levels were measured and HO-1 protein expression in airway macrophages was determined by Western blotting in asthmatic patients as levels of oxidants are raised in asthma and may induce HO-1. RESULTS Exhaled CO was significantly increased in 37 non-steroid treated asthmatic patients compared with 37 healthy subjects (5.8 (95% CI 5.20 to 6.39) ppm vs 2.9 (2.51 to 3.28) ppm; p<0.0001) but was similar to normal in 25 patients who received corticosteroids (3.3 (95% CI 2.92 to 3.67) ppm; p>0.05). In non-treated asthmatic patients more HO-1 protein was expressed in airway macrophages than in normal subjects. Bilirubin levels in induced sputum were also higher than in normal subjects. Inhalation of hemin, a substrate for HO, significantly increased exhaled CO from 3.8 (95% CI 2.80 to 4.87) ppm to 6.7 (95% CI 4.95 to 8.38 CI) ppm (p<0.05) with a concomitant decrease in exhaled nitric oxide levels, suggesting an interaction between the two systems. CONCLUSIONS Increased exhaled CO levels and HO-1 expression may reflect induction of HO-1 which may be inhibited by steroids. Measurement of exhaled CO, an index of HO activity in non-smoking subjects, may therefore be clinically useful in the detection and management of asthma and possibly other chronic inflammatory lung disorders.

Increased carbon monoxide in exhaled air of patients with cystic fibrosis

BACKGROUND Inflammation, oxidative stress, and recurrent pulmonary infections are major aggravating factors in cystic fibrosis. Nitric oxide (NO), a marker of inflammation, is not increased, however, probably because it is metabolised to peroxynitrite. Exhaled carbon monoxide (CO), a product of heme degradation by heme oxygenase 1 (HO-1) which is induced by inflammatory cytokines and oxidants, was therefore tested as a non-invasive marker of airway inflammation and oxidative stress. METHODS Exhaled CO and NO concentrations were measured in 29 patients (15 men) with cystic fibrosis of mean (SD) age 25 (1) years, forced expiratory volume in one second (FEV1) 43 (6)%, 14 of whom were receiving steroid treatment. RESULTS The concentration of exhaled CO was higher in patients with cystic fibrosis (6.7 (0.6) ppm) than in 15 healthy subjects (eight men) aged 31 (3) years (2.4 (0.4) ppm, mean difference 4.3 (95% CI 2.3 to 6.1), p<0.001). Patients not receiving steroid treatment had higher CO levels (8.4 (1.0) ppm) than treated patients (5.1 (0.5) ppm, mean difference 3.3 (95% CI –5.7 to -0.9), p<0.01). Normal subjects had higher NO levels (6.8 (0.4) ppb) than patients with cystic fibrosis (3.2 (0.2) ppb, mean difference 3.8 (95% CI 2.6 to 4.9), p<0.05) and were not influenced by steroid treatment (3.8 (0.4) ppb and 2.7 (0.3) ppb for treated and untreated patients, respectively, mean difference 0.8 (95% CI –0.6 to 2.3), p>0.05). Patients homozygous for the ΔF508 CFTR mutation had higher CO and NO concentrations than heterozygous patients (CO: 7.7 (1.8) ppm and 4.0 (0.6) ppm, respectively, mean difference 3.7 (95% CI –7.1 to –0.3), p<0.05; NO: 4.1 (0.5) ppb and 1.9 (0.7) ppb, respectively, mean difference 2.2 (95% CI –3.7 to –0.6), p<0.05). CONCLUSIONS High exhaled CO concentrations in patients with cystic fibrosis may reflect induction of HO-1. Measurement of exhaled CO concentrations may be clinically useful in the management and monitoring of oxidation and inflammatory mediated lung injury.

Comparison of inspiratory and expiratory resistance and reactance in patients with asthma and chronic obstructive pulmonary disease

Background The usual analysis of forced oscillometry measures respiratory resistance (Rrs) and reactance (Xrs) averaged over several tidal breaths (whole-breath analysis). Recent within-breath analyses have separated Rrs and Xrs into their mean inspiratory and mean expiratory components (inspiratory–expiratory breath analysis) but these have not been used to compare patients with asthma and those with chronic obstructive pulmonary disease (COPD). Large inspiratory–expiratory variations in Xrs at 5 Hz (ΔX5) in an individual have been used as a surrogate marker of expiratory flow limitation. Methods Whole-breath and inspiratory–expiratory impulse oscillometry was assessed in 34 patients with asthma (49±3 years; 15 male, forced expiratory volume in 1 s (FEV1) 69±4% predicted), 48 patients with COPD (64±2 years; 32 male, FEV1 59±3% predicted) and 18 normal subjects (37±2 years; 8 male). Results Whole-breath analysis failed to discriminate between patients with asthma and patients with COPD either for all patients or for patients with FEV1 <60% predicted. Inspiratory–expiratory analysis in patients with FEV1 <60% predicted showed that in the COPD group mean expiratory X5 (−0.44±0.04 kPa/l/s) was greater than inspiratory X5 (−0.23±0.02 kPa/l/s, p<0.001) whereas patients with asthma did not show such changes (−0.36±0.07 kPa/l/s vs −0.26±0.03 kPa/l/s, p=0.23). Even though ΔX5 was larger in patients with COPD (0.21±0.03 kPa/l/s) than in patients with asthma (0.10±0.07 kPa/l/s), this was not significant (p=0.15). Conclusions Whole-breath impulse oscillation system analysis failed to discriminate between patients with asthma and those with COPD. Inspiratory–expiratory X5 analysis differentiated patients with asthma from those with COPD presumably reflecting enhanced dynamic airway narrowing on expiration in COPD. Further studies are needed to confirm these differences and investigate their cause.

Correlation of exhaled breath temperature with bronchial blood flow in asthma

In asthma elevated rates of exhaled breath temperature changes (Δe°T) and bronchial blood flow (Qaw) may be due to increased vascularity of the airway mucosa as a result of inflammation.We investigated the relationship of Δe°T with Qaw and airway inflammation as assessed by exhaled nitric oxide (NO). We also studied the anti-inflammatory and vasoactive effects of inhaled corticosteroid and β2-agonist.Δe°T was confirmed to be elevated (7.27 ± 0.6 Δ°C/s) in 19 asthmatic subjects (mean age ± SEM, 40 ± 6 yr; 6 male, FEV1 74 ± 6 % predicted) compared to 16 normal volunteers (4.23 ± 0.41 Δ°C/s, p < 0.01) (30 ± 2 yr) and was significantly increased after salbutamol inhalation in normal subjects (7.8 ± 0.6 Δ°C/ s, p < 0.05) but not in asthmatic patients. Qaw, measured using an acetylene dilution method was also elevated in patients with asthma compared to normal subjects (49.47 ± 2.06 and 31.56 ± 1.6 μl/ml/min p < 0.01) and correlated with exhaled NO (r = 0.57, p < 0.05) and Δe°T (r = 0.525, p < 0.05). In asthma patients, Qaw was reduced 30 minutes after the inhalation of budesonide 400 μg (21.0 ± 2.3 μl/ml/min, p < 0.05) but was not affected by salbutamol.Δe°T correlates with Qaw and exhaled NO in asthmatic patients and therefore may reflect airway inflammation, as confirmed by the rapid response to steroids.

Exhalation flow and pressure-controlled reservoir collection of exhaled nitric oxide for remote and delayed analysis

BACKGROUND Expiratory flow rate, soft palate closure, and dead space air may influence exhaled levels of nitric oxide (NO). These factors have not been evaluated in the reservoir collection of NO. METHODS Exhaled NO was collected into a reservoir during a single flow and pressure controlled exhalation. RESULTS NO collected in a reservoir containing silica gel was stable for 24 hours. Nasally delivered 4.8% argon measured by mass spectrometry did not contaminate exhaled argon levels (0.1 (0.02)%) in five volunteers during exhalation against a resistance (10 (0.5) cmH2O), hence proving an effective soft palate closure. Exhaled NO in the reservoir was 11 (0.2) ppb, 8.6 (0.1) ppb, 7.1 (0.6) ppb, and 6.6 (0.4) ppb in five normal subjects and 48.3 (18) ppb, 20.3 (12) ppb, 16.9 (0.3) ppb and 10.1 (0.4) ppb in 10 asthmatic subjects at four studied expiratory flows (5–6, 7–8, 10–11, and 12–13 l/min, respectively), with NO levels equal to direct measurement (7.3 (0.5) ppb and 17.4 (0.5) ppb for normal and asthmatic subjects respectively, p<0.05) at the flow rate 10–11 l/min. Elimination of dead space proved necessary to provide NO levels comparable to the direct measurement. Exhaled NO collected into the reservoir without dead space during flow controlled exhalation against mild resistance provided close agreement (mean (SD) difference –0.21 (0.68), coefficient of variation 4.58%) with direct measurement in 74 patients (NO range 1–69 ppb). CONCLUSIONS Flow and pressure controlled collection of exhaled NO into a reservoir with silica gel provides values identical to the direct measurement and may be used to monitor asthma at home and where analysers are not on site.

Real-time measurement of particulate matter deposition in the lung

Abstract Air pollution and cigarette smoke are recognized health risks. A method was developed for the measurement of the deposition fraction (DF) of polydisperse particulate matter (PM) in human airways. Ten normal volunteers [three females, age range 18–67 years, mean age (SD) 43.9 (14)] made single breath exhalations after inhalation to total lung capacity. The exhaled breath was diverted to a multichannel laser diffraction chamber where the particulate profiler measured 0.3–1.0-µm particles. DF was inversely related to expiration flow-rate, 0.69 (0.02) at 4 l min−1 and 0.5 (0.01) at 13 l min−1, respectively (p<0.05), and was influenced by the inhalation flow-rate [0.70 (0.02) at 3 l min−1 and 0.59 (0.02) at 13 l min−1, respectively (p<0.05)], while no differences were found between nasal and oral inhalation (0.68 (0.05) versus 0.67 (0.06), p>0.05). Higher breath holding times were associated with elevated DF [0.74 (0.02) at 20 s, and 0.62 (0.05) without breath holding (p<0.01)]. When the expiratory flow was controlled and the breath hold time standardized, DF was reproducible (CV = 4.85%). PM can be measured in the exhaled breath and its DF can be quantified using a portable device. These methods may be useful in studies investigating the health effects of air pollution and tobacco smoke.

Glottal Aperture and Buccal Airflow Leaks Critically Affect Forced Oscillometry Measurements.

BACKGROUND The forced oscillation technique (FOT) measures respiratory resistance and reactance; however, the upper airways may affect the results. We quantified the impact of glottal aperture and buccal air leaks. METHODS In the glottal aperture study (1) 10 healthy subjects (aged 34 ± 2 years) performed a total lung capacity maneuver followed by 10-s breath-hold with and without total glottal closure and (2) the effects of humming (incomplete glottal narrowing) on FOT measurements were studied in six healthy subjects. Glottal narrowing was confirmed by direct rhinolaryngoscopy. In the air leak study, holes of increasing diameter (3.5, 6.0, and 8.5 mm) were made to the breathing filters. Eleven healthy subjects (aged 33 ± 2 years) and five patients with COPD (aged 69 ± 3 years) performed baseline FOT measurements with the three modified filters. RESULTS Narrow glottal apertures and humming generated whole-breath resistance at 5 Hz (R5) peaks, increased R5 (1.49 ± 0.37 kPa/L/s vs 0.34 ± 0.01 kPa/L/s, P < .001), and decreased whole-breath reactance at 5 Hz (X5) values (-2.10 ± 0.51 kPa/L/s vs -0.09 ± 0.01 kPa/L/s, P < .001). The frequency dependency of resistance was increased. Holes in the breathing filters produced indentations on the breathing trace. Even the smaller holes reduced R5 in healthy subjects (0.33 ± 0.02 to 0.24 ± 0.02 kPa/L/s, P < .01) and patients with COPD (0.50 ± 0.04 to 0.41 ± 0.04 kPa/L/s, P < .05), whereas X5 became less negative (from -0.09 ± 0.01 to -0.05 ± 0.01 in healthy subjects, P < .01; from -0.22 ± 0.06 to -0.11 ± 0.03 kPa/L/s in patients with COPD, P < .05). CONCLUSIONS Visual inspection of the data is required to exclude glottal narrowing and buccal air leaks identified as R5 peaks and volume indentations, respectively, because these significantly affect FOT measurements.

The effect of body weight on distal airway function and airway inflammation

BACKGROUND/OBJECTIVES Obesity is a global health problem that adversely influences the respiratory system. We assessed the effects of body mass index (BMI) on distal airway function and airway inflammation. SUBJECTS/METHODS Impulse oscillometry (IOS) as a measure of distal airway function, together with spirometry, were assessed in adults with a range of different BMIs. Airway inflammation was assessed with the fraction of exhaled nitric oxide (FeNO) and participants exhaled at various exhalation flows to determine alveolar and bronchial NO. RESULTS In total 34 subjects were enrolled in the study; 19 subjects had a normal BMI (18.50-24.99), whilst 15 subjects were overweight (BMI 25.00-29.99), or obese (BMI ≥30). All subjects had normal spirometry. However, IOS measures of airway resistance (R) at 5Hz, 20Hz and frequency dependence (R5-20) were elevated in overweight/obese individuals, compared to subjects with a normal BMI (median (interquartile range)); 5Hz: 0.41 (0.37, 0.45) vs. 0.32 (0.30, 0.37)kPa/l/s; 20Hz: 0.34 (0.30, 0.37) vs. 0.30 (0.26, 0.33)kPa/l/s; R5-20: 0.06 (0.04, 0.11) vs. 0.03 (0.01, 0.05)kPa/l/s; p<0.05), whereas airway reactance at 20Hz was decreased in overweight/obese individuals (20Hz: 0.07 (0.03, 0.09) vs. 0.10 (0.07, 0.13)kPa/l/s, p=0.009; 5Hz: -0.12 (-0.15, -0.10) vs. -0.10 (-0.13, -0.09)kPa/l/s, p=0.07). In contrast, within-breath IOS measures (a sign of expiratory flow limitation) and FeNO inflammatory measures, did not differ between groups (p>0.05). CONCLUSIONS Being overweight has significant effects on distal and central airway function as determined by IOS, which is not detected by spirometry. Obesity does not influence airway inflammation as measured by FeNO. IOS is a reliable technique to identify airway abnormalities in the presence of normal spirometry in overweight people.

Exhaled carbon monoxide in lung disease

To the Editor: We read with interest the paper by Zetterquist et al. 1 in which the levels of exhaled nitric oxide (NO) and carbon monoxide (CO) were measured in a group of asthmatic and cystic fibrosis (CF) patients using two different methods. A new fast-response nondisperse infrared (NDIR) CO analyser was used alongside the old electrochemical method and the results obtained with the two methods were compared. Surprisingly, contrary to what has previously been shown by our own and other groups 2–6, as shown by both methods, the levels of exhaled CO were found to be similar in a group of asthmatic patients and patients with CF compared with normal subjects. The authors conclude that exhaled CO …

Carbon monoxide, cigarettes and family doctors

Aims and Background General practitioners could play a key role in preventive programs against tobacco-related diseases. However, they seldom take action in the office even with minimal advice counselling. Such behaviour might reflect the lack of academic teaching and the lack of practice with motivational and dependence questionnaires, considered basic tools to help smokers to quit successfully. The study was aimed to investigate the awareness of a sample of Italian family doctors as regards tobacco epidemiology and smoking cessation strategies. Methods A total of 428 family doctors were administered a questionnaire with a set of questions on their personal smoking habits and on personal initiatives in the office towards smokers. Another set of questions regarded their knowledge on tobacco issues, with special attention to carbon monoxide, which is widely perceived as a very dangerous poison and works as a motivational tool on smokers and adolescents. Carbon monoxide measurement was carried out on all participants to obtain objective data on smoking and to show the feasibility of the test. Results The percentage of self-reported current smokers among general practitioners was 24%, with a high prevalence of ex-smokers (46%), and 29% of never smokers. Family doctors were more keen to counsel adolescents than adults about tobacco, and they were very interested in continuing medical education on the issue. The doctors who took part in our study showed a surprising limited knowledge of all the issues associated with smoking cessation and prevention such as epidemiology, cigarette characteristics, success rate of smoking cessation programs, Fagerströms tolerance questionnaire, safety of nicotine replacement therapy and the knowledge of carbon monoxide as a product of cigarette smoke. Conclusions The scenario depicted by our survey underscores the necessity to improve the knowledge and performance of primary care physicians on tobacco-related issues in order to implement primary and secondary prevention in clinical practice.