Involvement of hemostasis in pathophysiology of RAO in horses

Recurrent Airway Obstruction (RAO), also called severe asthma or heaves, is a chronic disease in adult horses caused by aeroallergens from straw or hay. Disturbances in hemostasis (intensified coagulation and depressed fibrinolysis) are considered one of the prominent reasons of inflammatory process, injury and dysfunction of the lungs. The aim of the study was to evaluate chosen parameters of hemostasis in horses with active form of RAO. Ten RAO-horses (group R) and ten healthy horses (group C) were exposed to straw and hay allergen challenge. The prothrombin time (PT), activated partial thromboplastin time (aPTT), thrombin time (TT), fibrinogen concentration (Fb), stabilized fibrin degradation product (d-dimer), antithrombin (AT), protein C and coagulation factors II through XII were assessed in plasma obtained from blood of all the horses. Exposure to aeroallergens resulted in prolongation of aPTT in both groups of animals; it was evident in the group R and moderate in the group C. There were no differences in PT and TT. Concentrations of fibrinogen and d-dimer and activity of protein C in both groups were increased but lay within or near to reference values. The activity of AT was depressed in RAO-horses. All exposed horses showed increased activity of coagulation factors II, VIII and X but they had no changes in activity of factor V. Factors VII and XII displayed a reduction in activity. The decrease in factor IX activity was noted in the group C only. Various changes were observed in activity of factor XI; in horses with RAO it was elevated but in healthy horses it was declined. The changes of the parameters tested in RAO-horses indicate the involvement of coagulation and fibrinolysis which apparently remained under control of efficient and active mechanisms of general hemostasis.

Liver and spleen elastography of dogs affected by brachycephalic obstructive airway syndrome and its correlation with clinical biomarkers

The purpose of this study is to determine whether the brachycephalic obstructive airway syndrome (BOAS) is correlated to alterations in liver and spleen elasticity. Forty-eight brachycephalic and 22 mesocephalic dogs were submitted to a BOAS functional assessment, laboratory tests, abdominal ultrasound and liver and spleen Acoustic Radiation Force Impulse (ARFI) elastography. Dogs clinically affected by BOAS had higher values of liver stiffness (p < 0.001) than healthy dogs: medial lobes (1.57 ± 0.37 m/s), left and right lateral lobes (1.54 ± 0.50 m/s, 1.23 ± 0.28 m/s, respectively) and caudate lobe (1.28 ± 0.42 m/s). Compared to the mesocephalic group, the brachycephalic group (BOAS clinically affected and unaffected dogs) had higher spleen (2.51 ± 0.45 m/s; p < 0.001) and liver stiffness (p < 0.001): medial lobes (1.53 ± 0.37 m/s), left and right lateral lobes (1.47 ± 0.47 m/s, 1.20 ± 0.30 m/s, respectively) and caudate lobe (1.23 ± 0.40 m/s). Principal component analysis explained 70% of the variances composed by liver stiffness increase, erythrocytes and alanine aminotransferase reduction. Brachycephalic dogs had higher spleen and liver stiffness and a subacute inflammatory state, which represent another BOAS systemic effect. Consequently, these dogs can be at higher risk of hepatic disorders compared with mesocephalic dogs, similarly to humans affected by sleep apnea syndrome.

Rescue ventilation through a small-bore transtracheal cannula in severe hypoxic pigs using expiratory ventilation assistance

BACKGROUND

Suction-generated expiratory ventilation assistance (EVA) has been proposed as a way to facilitate bidirectional ventilation through a small-bore transtracheal cannula (TC). In this study, we investigated the efficiency of ventilation with EVA for restoring oxygenation and ventilation in a pig model of acute hypoxia.

METHODS

Six pigs (61-76 kg) were anesthetized and ventilated (intermittent positive pressure ventilation) via a cuffed endotracheal tube (ETT). Monitoring lines were placed, and a 75-mm long, 2-mm inner diameter TC was inserted. After the baseline recordings, the ventilator was disconnected. After 2 minutes of apnea, reoxygenation with EVA was initiated through the TC and continued for 15 minutes with the ETT occluded. In the second part of the study, the experiment was repeated with the ETT either partially obstructed or left open. Airway pressures and hemodynamic data were recorded, and arterial blood gases were measured. Descriptive statistical analysis was performed.

RESULTS

With a completely or partially obstructed upper airway, ventilation with EVA restored oxygenation to baseline levels in all animals within 20 seconds. In a completely obstructed airway, PaCO2 remained stable for 15 minutes. At lesser degrees of airway obstruction, the time to reoxygenation was delayed. Efficacy probably was limited when the airway was completely unobstructed, with 2 of 6 animals having a PaO2 <85 mm Hg even after 15 minutes of ventilation with EVA and a mean PaCO2 increased up to 90 mm Hg.

CONCLUSIONS

In severe hypoxic pigs, ventilation with EVA restored oxygenation quickly in case of a completely or partially obstructed upper airway. Reoxygenation and ventilation were less efficient when the upper airway was completely unobstructed.

Clinical assessment and C-reactive protein (CRP), haptoglobin (Hp), and cardiac troponin I (cTnI) values of brachycephalic dogs with upper airway obstruction before and after surgery

Brachycephalic dogs have unique upper respiratory anatomy with abnormal breathing patterns that are similar to those in humans with obstructive sleep apnea syndrome (OSAS). The objectives of this multicenter prospective study were to assess the effects of surgical correction on clinical signs in dogs with brachycephalic airway obstructive syndrome (BAOS) and to evaluate the levels of several biomarkers [C-reactive protein (CRP); haptoglobin (Hp), and cardiac troponin I (cTnI)] used to determine systemic inflammation and myocardial damage. This study was conducted on 33 dogs with BAOS that were evaluated before and 1 to 2 mo after surgical correction. Palatoplasty was carried out by means of 2 different surgical techniques: carbon dioxide (CO2) laser (n = 12) and electrical scalpel (n = 21). Biomarker levels (CRP, Hp, and cTnI) were determined before and after surgery. There was a significant reduction in respiratory and gastrointestinal signs in dogs with BAOS after surgical treatment (P < 0.001). A greater reduction in respiratory signs (P < 0.002) was obtained using the CO2 laser. No statistical differences were found between CRP and cTnI levels, either before or after surgical correction. Haptoglobin concentration did increase significantly in the postsurgical period (P < 0.008). Surgical treatment in dogs with BAOS reduces clinical signs, regardless of the anatomical components present. Surgical treatment for BAOS is not useful to reduce CRP and Hp levels, probably because BAOS does not induce as obvious an inflammatory process in dogs as in human patients with OSAS. No reduction in cTnI levels was observed 1 mo after surgery in dogs with BAOS, which suggests that some degree of myocardial damage remains.

Cytokine expression by peripheral blood neutrophils from heaves-affected horses before and after allergen challenge

Heaves, also known as recurrent airway obstruction, is a common condition of horses characterised by pulmonary neutrophilia and reversible airway obstruction. This study evaluated the role of neutrophils in producing cytokines and chemokines that might be involved in the recruitment and activation of inflammatory cells in horses with heaves. Peripheral neutrophils were isolated from heaves-affected (n = 9) and control (n = 4) horses before and after 5 h of natural inhalation challenge. Expression of mRNA of two pro-inflammatory cytokines, tumour necrosis factor (TNF)-alpha and interleukin (IL)-1beta, along with two chemokines, IL-8 and macrophage inflammatory protein (MIP)-2, was evaluated. After exposure to mouldy hay, horses with heaves had significant airway obstruction and increased numbers of neutrophils in bronchoalveolar lavage samples, compared to control horses. However, there were no differences in the expression of mRNAs of TNF-alpha, IL-1beta, IL-8 and MIP-2 between the two groups, suggesting that the release of cytokines and chemokines by peripheral blood neutrophils is not necessary for the development of heaves.

The effect of adenotonsillectomy on oxygen saturation in children with sleep breathing disorders

OBJECTIVE

To evaluate the effect of adenotonsillectomy on the oxygen saturation measures by nocturnal pulse oximetry in children with sleep breathing disorders (SBD).

METHODS

A non-controlled clinical trial was performed. Thirty-one children with suspected SBD and a clinical indication for adenotonsillectomy were recruited. All of them underwent overnight oxygen saturation monitoring before and after surgery.

RESULTS

Twenty-seven patients completed the study. The mean age was 5.2+/-1.8 years. Eighteen (66.7%) were male. The most prevalent symptoms were: snoring (100%), respiratory pauses (96.8%), nocturnal mouth breathing (96.8%), restless sleep (80%) and drooling (74.1%). Twenty-three children (85.2%) presented grade 3 or 4 tonsillar hyperplasia. There was a significant improvement in the postoperative oxygen desaturation index (ODI) (0.65; 0.5-1.3) compared with the preoperative index (1.63; 1.1-2.4) (p<0.001).

CONCLUSION

Adenotonsillectomy improved the oxygen saturation measures by nocturnal pulse oximetry in children with sleep breathing disorders.

Possible mechanism of pesticide toxicity-related oxidative stress leading to airway narrowing

The study was conducted to assess the magnitude of oxidative stress and lung function abnormalities in 34 male pesticide sprayers on exposure to pesticides in mango plantations. Biochemical studies on blood antioxidant enzymes revealed an unchanged glutathione level and increased level of malondialdehyde (P < 0.001), which indicates that pesticide sprayers may have suffered from oxidative stress. Decreased acetyl-cholinesterase levels (P < 0.001) in sprayers compared to the controls suggest inhibition of cholinesterase activity. The present study shows that pesticide toxicity might lead to oxidative stress and airway narrowing resulting in decreased peak expiratory flow rate.

Serum carotenoids, vitamins A and E, and 8 year lung function decline in a general population

BACKGROUND

Oxidative stress is thought to have a major role in the pathogenesis of airway obstruction. A study was undertaken to determine whether subjects with low levels of antioxidants (serum beta-carotene, alpha-carotene, vitamins A and E) would be at a higher risk of accelerated decline in forced expiratory volume in 1 second (FEV1) as their lungs would be less protected against oxidative stress.

METHODS

1194 French subjects aged 20-44 years were examined in 1992 as part of the European Community Respiratory Health Survey (ECRHS); 864 were followed up in 2000 and 535 (50% men, 40% lifelong non-smokers) had complete data for analysis.

RESULTS

During the 8 year study period the mean annual decrease in FEV1 (adjusted for sex, centre, baseline FEV1, age, smoking, body mass index and low density lipoprotein cholesterol) was 29.8 ml/year. The rate of decrease was lower for the subjects in tertile I of beta-carotene at baseline than for those in the two other tertiles (-36.5 v -27.6 ml/year; p = 0.004). An increase in beta-carotene between the two surveys was associated with a slower decline in FEV1. No association was observed between alpha-carotene, vitamin A, or vitamin E and FEV(1) decline. However, being a heavy smoker (> or =20 cigarettes/day) in combination with a low level of beta-carotene or vitamin E was associated with the steepest decline in FEV1 (-52.5 ml/year, p = 0.0002 and -50.1 ml/year, p = 0.010, respectively).

CONCLUSIONS

These results strongly suggest that beta-carotene protects against the decline in FEV1 over an 8 year period in the general population, and that beta-carotene and vitamin E are protective in heavy smokers.

Blood gas analysis and chest x-ray findings in infants and preschool children with acute airway obstruction

BACKGROUND

The importance of SaO2 in the assessment of respiratory distress in bronchial asthma has been reported.

OBJECTIVES

To evaluate the correlation between blood gas analysis and chest X-ray lung opacities in young children presenting with acute respiratory symptoms.

METHODS

Eighty patients (43 males and 37 females aged 0.5-24 months; mean+/-SD 9.1+/-7.2 months), either with acute wheezing respiratory symptoms and/or with crackles were enrolled in our study. In all children, blood gas analysis and chest X-rays were performed within 12 h following admission to the emergency department.

RESULTS

In 55 children (68.75%) chest X-rays demonstrated lung opacities. Subjects with normal X-rays had paO2 and SaO2 higher than subjects with lung opacities (p<0.0001 and p=0.0001, respectively). Children with lung opacities almost always presented paO2<80 mm Hg. Sensitivity and specificity for the presence of lung opacities of paO2<80 mm Hg were 81 and 90%, respectively, while sensitivity and specificity of SaO2<95% were 92 and 40%, respectively. paO2<80 mm Hg in association with SaO2<95% had a positive predictive value for the diagnosis of pneumonia of 90.9%.

CONCLUSIONS

Our study suggests that blood gas analysis, particularly paO2, may help in predicting the presence of lung opacities in patients aged less than 2 years. However, chest X-rays may still be needed to define the actual extension of opacities as well as the possible concomitant presence of complications.

Cytokine profiles of peripheral blood and airway CD4 and CD8 T lymphocytes in horses with recurrent airway obstruction

Equine recurrent airway obstruction (RAO) is thought to result from an aberrant immune response to inhaled antigens, modulated by T lymphocytes via the secretion of pro-inflammatory cytokines. However data relating to the phenotypes of the T lymphocytes present in peripheral blood and bronchoalveolar lavage fluid of RAO horses and their cytokine profiles are contradictory. The aim of this study was to further investigate the cytokine (IL-4, IL-5, IL-13 and INF-gamma) mRNA expression profile in peripheral blood lymphocytes and bronchoalveolar lavage lymphocytes from RAO and control horses, before and at 48 h after horses were exposed to hay/straw. In contrast to previous studies, cytokine expression was quantified in populations of CD4 and CD8 T lymphocytes which were purified using magnetic bead antibody cell separation. Hay/straw exposure induced clinical airway obstruction, airway neutrophilia and airway lymphocytosis in RAO horses, and, induced a mild, but significant, airway neutrophilia in controls. However, hay/straw exposure had no significant effect on peripheral blood lymphocyte or bronchoalveolar lavage lymphocyte cytokine expression in either group. In conclusion, RAO was not associated with alterations in lymphocyte cytokine expression that are consistent with Th1 or Th2 responses, but rather with a general down-regulation in expression of the measured cytokines in peripheral blood lymphocytes and bronchoalveolar lavage lymphocytes.

Application of the comet assay for investigation of oxidative DNA damage in equine peripheral blood mononuclear cells

Oxidative stress occurs when antioxidant defense mechanisms are overwhelmed by free radicals and may lead to DNA damage, which has been implicated in processes such as aging and diseases such as cancer. The two main techniques presently used to quantify DNA damage are measurement of 8-hydroxydeoxyguanosine and the Comet assay (also known as single-cell gel electrophoresis). The aim of this study was to apply the comet assay to equine peripheral blood mononuclear cells (PBMCs) and identify two conditions in which we hypothesized that oxidative DNA damage would be increased in PBMCs: aging and equine recurrent airway obstruction (RAO, a condition similar to human asthma). The images obtained were similar to those previously published for humans, cats, and dogs. The optimum concentration of H(2)O(2) to estimate susceptibility to exogenous damage was 50 microM. Mean intraassay coefficients of variation were 4.7 and 9.7% for endogenous and exogenous tail-DNA quantities, respectively, and 7.3 and 8.3%, respectively, for interassay coefficients. There was no significant difference in either endogenous or exogenous percentages of tail DNA for samples collected from six ponies on three consecutive days. There was no significant difference in endogenous, exogenous, or exogenous (corrected for endogenous) oxidative DNA damage between mature and aged ponies. However, young pony foals had significantly less endogenous DNA damage than mature or aged ponies (P < 0.05). RAO-affected horses without airway inflammation (i.e., in clinical remission) had significantly greater endogenous damage compared with non-RAO-affected control animals (P = 0.009). There was a significant correlation between endogenous percentage of tail DNA in PBMCs and red blood cell hemolysate glutathione concentration (r = 0.720; P < 0.001). In conclusion, the comet assay appears to be suitable for investigating DNA damage in equine PBMCs.

Nocturnal Arterial Oxygen Desaturation and Episodic Airway Obstruction After Ambulatory Surgery

Some patients experience disordered breathing during sleep and arterial oxygen desaturation after major inpatient surgery. We performed this study to determine whether similar events occur after ambulatory surgery. Forty-five ambulatory surgery patients received an unrestricted anesthetic. Continuous unattended nocturnal recordings of breathing pattern and oxygen saturation were made in the patients' homes before surgery and during the first and second postoperative nights. Nine patients had a respiratory disturbance index >10 and/or >1% of recording time with oxygen saturation <90% on at least one study night. These nine patients had a significantly older median age and a significantly larger median body mass index. Their median respiratory disturbance index and median percentage of time with oxygen saturation <90% were significantly higher on the first postoperative night than on the preoperative night.

Correlations between exhaled nitric oxide levels, blood eosinophilia, and airway obstruction reversibility in childhood asthma are detectable only in atopic individuals

The aim of this study was to compare in atopic and nonatopic asthmatic children correlations between two inflammation parameters, i.e., blood eosinophilia and exhaled nitric oxide (FE(NO)), and pulmonary function values, at baseline and after beta(2)-adrenergic bronchodilators. Ninety-two steroid-naive asthmatic children were evaluated: 26 were skin prick test- and RAST-negative (nonatopic subjects), whereas 66 were atopic, 15 being sensitized only to house dust mites (monosensitized) and 51 to mites and to at least one other class of allergens (polysensitized). Baseline spirometric values (FEV(1) and FEF(25-75%)) were similar in atopic and nonatopic groups (P > 0.1, each comparison). However, when compared to nonatopic subjects, atopic children showed a significantly higher degree of blood eosinophilia (3.0% and 6.7% white blood cell count, respectively; P = 0.0001) and higher FE(NO) levels (6.8 ppb and 16.0 ppb, respectively; P = 0.0001). While a positive correlation between FE(NO) levels and blood eosinophilia was observed in atopic children (r = 0.25, P = 0.041), no correlations between these two inflammation parameters and baseline pulmonary function values were demonstrated in any of the asthmatic groups. Inhalation of a beta(2)-agonist drug induced in the two asthmatic populations similar improvements in FEV(1) and FEF(25-75%) and no changes in FE(NO) levels or blood eosinophilia. However, only in atopic children positive correlations were found between percent variation in FEV(1) (delta%FEV(1)) and FE(NO) levels (r = 0.35, P = 0.006) or blood eosinophilia (r = 0.26, P = 0.04). Within the atopic group, no differences were found between mono- and polysensitized individuals in all parameters evaluated. Thus only in atopic children did parameters of inflammation correlate with airway obstruction reversibility.

The effects of tonsillectomy and adenoidectomy on serum IGF-I and IGFBP3 levels in children

OBJECTIVE

Obstructive adenoid and tonsillar hyperplasia may present with retardation of growth. Interruption of growth hormone-insulin-like growth factor I axis resulting from abnormal nocturnal growth hormone secretion is among the postulated causes. Growth hormone (GH) mediates its anabolic effects on tissues through insulin-like growth factor I (IGF-I). Most of the circulating IGF-I is bound to insulin-like growth factor binding protein 3 (IGFBP3). The objective of this study is to determine blood serum levels of IGF-I and IGFBP3 in patients with adenoid and tonsillar hypertrophy. Furthermore, we want to investigate the effect of tonsillectomy and adenoidectomy (T&A) on these levels.

STUDY DESIGN

The blood serum levels of IGF-I and its binding protein IGFBP3 were examined in 41 randomly selected children with a diagnosis of upper airway obstruction resulting from hypertrophic tonsils and adenoids.

METHODS

Blood samples were taken preoperatively and repeated at 3 to 6 months (mean, 4.3 mo) following T&A operation. Coated-tube immunoradiometric assay (IRMA) method was used to analyze IGF-I and IGFBP3 levels.

RESULTS

Thirty-two of 41 children were eligible for the analysis. When the preoperative and postoperative results were compared, it was found that there was a statistically significant increase in serum IGF-I and IGFBP3 levels in these 32 children (P <.001). In 7 of the 32 patients, the preoperative serum IGF-I levels were below normal. Postoperatively these levels increased within normal range. This was also statistically significant (P = .016).

CONCLUSION

These findings revealed that obstructive adenoid and tonsillar hypertrophy may cause decreased serum IGF-I levels by affecting the GH-IGF-I axis, and T&A is an effective therapeutic measure in these patients.

Management of acute hypoxemia during flexible bronchoscopy with insertion of a nasopharyngeal tube in lung transplant recipients

STUDY OBJECTIVES

To assess the utility of nasopharyngeal tube insertion in the management of hypoxemia during flexible bronchoscopy (FB) in lung transplant recipients, and to determine the incidence and risk factors of upper-airway obstruction (UAO) leading to significant hypoxemia during FB.

SETTING

Heart-lung transplant unit of a university hospital.

PATIENTS AND METHODS

Ninety-six lung transplant recipients (47 men and 49 women; mean +/- SD age, 41.4 +/- 13.1 years) underwent 714 FB procedures from January 1997 to May 2000.

INTERVENTION

A fall in oxygen saturation (< or = 90%) in patients receiving 6 L/min of oxygen via nasal prongs was treated with insertion of a nasopharyngeal tube, continued oxygen supplementation, and withdrawal of the bronchoscope to the trachea. If oxygen desaturation persisted at < 90% despite additional oxygen administration via a 7F catheter placed either just above the larynx or in the proximal trachea, the bronchoscope was withdrawn, reversal of sedation was administered, and bag and mask ventilation was instituted until satisfactory spontaneous ventilation was achieved.

RESULTS

Forty-six patients (47.9%) were treated with nasopharyngeal tube insertion on 102 occasions at a mean duration of 168 +/- 178 days after lung transplantation. In 90 of 102 procedures (88.2%), significant hypoxemia due to UAO was successfully treated with nasopharyngeal tube insertion. The mean oxygen saturation after nasopharyngeal tube insertion was 97 +/- 3%. Male gender, increase in body mass index after lung transplantation, and presence of obstructive sleep apnea were significant factors associated with the need for nasopharyngeal tube insertion during FB in lung transplant recipients.

CONCLUSIONS

Significant oxygen desaturation during FB in lung transplant recipients is mainly due to UAO. Insertion of a nasopharyngeal tube is a novel and a highly effective approach to the management of acute hypoxemia during FB.

Time course of diaphragm injury and calpain activity during resistive loading

The purpose of this study was to determine the time course of arterial blood gas (ABG) deterioration, increased calpain activity, and diaphragm injury during 4 d of resistive loading. Adult Sprague- Dawley rats were divided into control (C) animals and groups that were tracheally banded (TB) for 1 d (TB1), 2 d (TB2), 3 d (TB3), and 4 d (TB4). In TB rats, the carotid artery was cannulated and the trachea was banded during anesthesia. TB groups (TB1, TB2, TB3, and TB4) had a 67% smaller internal cross-sectional area of the trachea than did C animals. ABG samples from awake rats showed a decreased arterial oxygen tension (Pa(O(2))) and a respiratory acidosis in the TB1, TB2, and TB3 groups. Calpain activity was higher in the diaphragm of TB than of C rats; calpainlike activities in soluble fractions of diaphragm tissue were greater in all TB groups than in C rats, whereas those in bound fractions were greater in the TB2 and TB3 groups. Point counting of hematoxylin and eosin-stained cross-sections showed that the area fraction (A(A)) of normal diaphragm was lower and the A(A) of abnormal muscle and connective tissue was higher in TB3 than in C rats. Increased resistive loading induced by tracheal banding was associated with hypercapnic ventilatory failure, increased calpain activity, and diaphragm injury. Ventilatory failure in response to resistive loading may be due to diaphragm injury and/or to decreased minute ventilation.

Serum ECP and MPO are increased during exacerbations of chronic bronchitis with airway obstruction

Many studies have demonstrated that, in asthma, serum levels of eosinophil cationic protein (ECP) are related to the activity and severity of the disease and can be used to evaluate the response to steroid treatment. During exacerbations of chronic bronchitis, airway inflammation shows some features of asthmatic inflammatory processes, with recruitment of eosinophils and recovery of significant amounts of ECP in bronchial lavage fluid (BAL). Involvement of neutrophils, with high levels of myeloperoxidase (MPO), is, on the contrary, typical of this latter disease, and not shared with asthma. In spite of the information collected with BAL and bronchial biopsy studies, few data still exist on serum levels of these proteins in chronic bronchitis. The objective of this study was to assess if serum levels of ECP and MPO are specifically increased in exacerbations of chronic bronchitis, as compared to other non-asthmatic acute respiratory disturbances. Serum ECP, MPO and immunoglobulin E (IgE) levels were measured in 17 non-atopic patients with exacerbation of chronic bronchitis with airway obstruction (COPD) and in 11 control subjects seeking emergency medical treatment for unrelated acute respiratory problems. Spirometry was performed in patients able to give the necessary collaboration. All the subjects of this study were recruited from the emergency department. Both ECP and MPO were significantly increased in serum from patients with exacerbated COPD (22.2 +/- 4.1 vs 9.5 +/- 1.4 mcg/L and 853 +/- 168 vs 375 +/- 41 mcg/L) and a strong correlation existed between these two variables (r = 0.782). A further control group was made of 11 patients with stable COPD. These subjects had levels of both ECP (13.1 +/- 2.7 mcg/L) and MPO (469 +/- 71) significantly lower than patients with exacerbated disease and higher than those without COPD. We conclude that serum ECP and MPO are increased during the exacerbations of COPD. These observations can give a basis for further studies aimed to evaluate the utility of these two proteins as markers of activity and severity of COPD.

Pharmacologic actions of the second generation leukotriene B4 receptor antagonist LY29311: in vivo pulmonary studies

We examined the in vivo actions of LY293111 sodium (2-[2-propyl-3-[3-[2-ethyl-4-(4-fluorophenyl)-5-hydroxyphenoxy]pro poxy]phenoxy] benzoic acid sodium salt). Guinea pigs were used to evaluate the effect of this agent on (1) acute airway obstruction produced by intravenous leukotriene B4, (2) pulmonary granulocyte infiltration and delayed onset airway obstruction resulting from a 4-h leukotriene B4 inhalation and (3) lung inflammation after aerosol challenge with the divalent cationic ionophore A23187 (6S-[6alpha(2S*,3S*),8beta(R*),9beta,11alpha]-5- (methylamino)-2-[[3,9,11-trimethyl-8-[1-methyl-2-oxo-2-(1H-pyrrol-2-yl)e thyl]-1,7-dioxaspiro[5.5]undec-2-yl]methyl]-4-benzoxazole carboxylic acid). Airway obstruction was quantitated using pulmonary gas trapping measurements and lung inflammation was evaluated by bronchoalveolar lavage (BAL) and histology. LY293111 sodium produced a dose-related inhibition of acute leukotriene B4-induced airway obstruction when administered i.v. (ED50=14 microg/kg) or p.o. (ED50=0.4 mg/kg). In contrast, LY293111 sodium did not inhibit the pulmonary gas trapping caused by aerosols of histamine, leukotriene D4, or the thromboxane mimetic U46619 (15 [(S)-hydroxy11a,9a-(epoxymethano)prosta-5Z,13E-dienoic acid]). Oral LY293111 sodium inhibited leukotriene B4-induced bronchoalveolar lavage granulocyte infiltration and delayed onset airway obstruction at doses as low as 0.3 mg/kg. In A23187-challenged animals, pulmonary inflammation was markedly inhibited at 1 h, but not 2 h and 4 h post-exposure. We conclude that LY293 11 sodium is a selective leukotriene B4 receptor antagonist with potent pulmonary anti-inflammatory activity.

Exploring intermittent transcutaneous CO2 monitoring

OBJECTIVE

To explore the accuracy of a continuous transcutaneous CO2 (T(CCO2)) monitor, used in an intermittent rather than a continuous fashion, to obtain quick (<5 mins) CO2 readings.

DESIGN

Prospective study.

SETTING

An urban pediatric intensive care unit in a university teaching hospital.

PATIENTS

A convenience sample of pediatric patients with indwelling arterial catheters.

INTERVENTION

Transcutaneous monitoring was done simultaneous with arterial blood gas monitoring.

MEASUREMENTS AND MAIN RESULTS

There were 49 simultaneous-readings on 19 patients, age 5 days to 16 years, with 13 different diagnoses. The T(CCO2) was related to the PCO2 by a Pearson product coefficient of 0.79 (p<.0005), with a mean difference of 1.94 (T(CCO2)>P(CO2) and 95% confidence interval of -0.12 to 4.07. The scatterplot produces a regression line characterized by the following equation: PCO2 = (T(CCO2)x1.05)-4.08.

CONCLUSIONS

Further study to evaluate intermittent TCCO2 as a practical clinical variable is warranted. This study should encourage refinement of the technology to be more accurate for this use.

Does eosinophil cationic protein in sputum and blood reflect bronchial inflammation and obstruction in allergic asthmatics?

In the assessment of asthma severity and monitoring of asthma drug therapy, eosinophils and eosinophil cationic protein (ECP) have been identified in blood but rarely in sputum. The aim of our study was to determine if ECP concentrations in blood and sputum reflect bronchial inflammation and obstruction in allergic asthmatics and if inhaled steroids influence this relationship. We carried out a descriptive, cross-sectional study of 42 allergic asthmatic outpatients from a respiratory medicine department, of whom 22 were on beta 2-adrenergic agonists only and 20 were treated with low doses of inhaled steroids. Spirometry and methacholine challenge were performed and eosinophils and ECP values in induced sputum and blood were determined. The age and FEV1 were similar in both groups. It was found that in patients receiving inhaled steroids, the methacholine PD20 was higher than in patients on beta 2-adrenergic agonists only. However, there were no significant differences in serum and sputum ECP between the groups (median 14.5 micrograms/l vs. 17.2 micrograms/l and 235 micrograms/l vs. 301 micrograms/l, respectively). In patients not receiving steroids, sputum ECP correlated positively with eosinophils in sputum (r = 0.61, p < 0.01) and inversely with FEV1 (r = -0.43, p < 0.05). Serum ECP correlated with blood eosinophils and methacholine PD20. In patients treated with inhaled steroids most correlations were no longer significant. We concluded that ECP in sputum, rather than in blood, seems to reflect both eosinophilic inflammation and bronchial obstruction in asthmatics not receiving inhaled steroids. Asthmatics on low doses of inhaled steroids had increased ECP levels in sputum and serum, indicating persistent eosinophilic inflammation of the airways.

Changes of arterial oxygen saturation (SpO2) following push-back operation

This study showed the influence of the push-back operation on the occurrence of sleep-related apnea in cleft-palate patients with an analysis of arterial oxygen saturation (SpO2) during sleep, polygraphic analysis of nasal air flow, and chest wall movements. The postoperative SpO2 was lower than that of the presurgical period in all cases, requiring from five to nine days to recover to presurgical levels. According to polygraphic analysis this depression of SpO2 was caused by peripheral obstructive apnea, while, in spite of the cessation of nasal airflow, chest wall movement continued.

Efficacy of cumulative doses of salbutamol administered via Turbuhaler or Diskhaler in patients with reversible airway obstruction

The study aimed to estimate the relative dose potency of salbutamol inhaled via Turbuhaler and Diskhaler. The 24 adult patients participating had chronic reversible airway obstruction. The study was of a double-blind, double-dummy, crossover, randomized design. Five doses of salbutamol Turbuhaler, 50, 50, 100, 200, and 400 microg, were given on one study day at intervals of 30 min. On another study day, five doses of salbutamol Diskhaler, 200, 200, 400, 800, and 1600 microg, were given with the same interval. The treatment days were separated by a washout period of at least 24 h. The inhalation technique was standardized and supervised. Efficacy variables were recorded before and after each study dose. The primary efficacy variable was forced expiratory volume in 1 s (FEV1). When parallel and linear cumulative dose-response curves were statistically compared on a logarithmic scale, the dose potency of salbutamol Turbuhaler vs salbutamol Diskhaler was 1.99 (95% confidence interval 1.52-2.54). This study indicates that only half the dose of salbutamol is required via Turbuhaler as via Diskhaler for the same bronchodilating effect.

Time course and pattern of pulmonary flow distribution following unilateral airway occlusion in sheep

1. Unilateral bronchial occlusion causes ipsilateral hypoxic pulmonary vasoconstriction, which shifts blood flow towards the other lung. We studied the time course of flow diversion following acute bronchial occlusion, and the temporal effect of the latter on blood gases and vertical distribution of blood flow within the two lungs. 2. Serial infusion of radioactive or fluorescent microspheres were given to each of seven adult standing sheep before, during occlusion of the left mainstem bronchus for up to 6 min, and after release of occlusion. Pulmonary and systemic arterial pressures were recorded continuously and arterial and mixed venous blood gases were determined intermittently. Post-mortem, the lungs were inflated, dried and cut into slices. Relative blood flow at the time of infusion was expressed as the weight-normalized intensity of each tracer in each slice or lung divided by the weight-normalized intensity in the two lungs. 3. Within 30 s, 1 min and 2 min after onset of occlusion, flow in the occluded lung had decreased to 68-84% (range), 51-78% and 43-79% respectively, of the initial value. In the contralateral lung, flow increased by 10-24%, 14-37% and 23-39% respectively. The distribution of flow along the gravitational axis within each lung varied widely between animals, both before and during occlusion. The during-occlusion profiles in the occluded lung differed from those in the non-occluded lung. In either lung, during-occlusion profiles could not be predicted with certainty from the pre-occlusion profiles. Two minutes post-occlusion, inter- and intra-lung flow distribution were nearly the same as before occlusion. Arterial oxygen tension fell in the first minute of occlusion, but never below 7.5 kPa, and increased slowly thereafter. Arterial carbon dioxide tension increased slightly throughout the occlusion period. No appreciable changes in systemic or pulmonary artery pressure were observed. Post-occlusion, arterial oxygen tension was still sub-normal, while carbon dioxide tension continued to increase. 4. We conclude that acute unilateral bronchial occlusion diverts blood flow within 30 s towards the contralateral lung. This rapidly occurring flow diversion prevents the development of severe arterial hypoxaemia. The variable and largely unpredictable distribution of blood flow in the hyperfused non-occluded lung might explain some of the gas-exchange abnormalities observed in physiologically hyperfused lungs and in patients with one hyperfused lung.

Clinical and serological responses to an inactivated influenza vaccine in adults with HIV infection, diabetes, obstructive airways disease, elderly adults and healthy volunteers

To investigate the clinical and serological responses to an inactivated influenza vaccine (split-virion A/Singapore/6/86-like strains H1N1 (15 ug HA), A/Beijing/353/89-like H3N2 (15 ug HA) and B/Yamagata/16/88-like strain (15 ug HA): MFV-JECT, Merieux, UK) in persons with HIV infection, diabetes, obstructive lung diseases, elderly adults and healthy volunteers. Forty-nine HIV-infected persons received 2 doses of the vaccine at one-month intervals; 34 healthy volunteers, 30 elderly persons, 29 with insulin and non-insulin diabetes and 14 with obstructive airways diseases were vaccinated with one single dose between October 1992 to January 1993. Serological testing of antibody responses was done using haemagglutination assay. Beta2-microglobulin in HIV-infected persons was measured using radioimmunodiffusion between 1st and 2nd dose. Fructosamine levels in diabetic persons were assessed for diabetic control and peak expiratory flow rate (PEFR) was self monitored in persons with lung diseases. All groups apart from the elderly filled in a symptom score chart for the first 5 days following vaccination. A 4-fold rise in titre equal to or more than 1:64 to all the 3 antigens occurred in 20 (58.8%) of healthy volunteers compared with 13 (44.8%) diabetics, 5 (35.7%) with lung diseases, 10 (33.3%) elderly and 13 (26.5%) with HIV infection. A significant correlation of serological response to number of CD4 count in persons with HIV infection was noted (H1N1 P=0.0013, H3N2 P=0.025, BYAM P=0.0018). Mean beta2-microglobulin levels did not change significantly post 1st and 2nd vaccination. Mean fructosamine level did not change significantly. There was no significant change in PEFR. The vaccine was well tolerated. Persons with HIV infection and low CD4 count do not serologically respond well to influenza vaccine even with 2 doses compared to the other 4 groups. The other 4 groups had adequate protective serologic responses. The vaccine was well tolerated in all groups.

Circulating endothelin-1 in obstructive sleep apnea

Endothelin (ET)-1 is a potent vasoconstrictive and mitogenic peptide produced by endothelial cells and degraded predominantly in pulmonary vasculature. We measured ET-1 in 9-normotensive and 14 hypertensive men with obstructive sleep apnea. The ET-1 levels were higher in both normotensive (mean +/- SD, 6.3 +/- 2.8 pg/ml) and hypertensive (7.8 +/- 3.0 pg/ml) groups than in 66 healthy controls (2.9 +/- 1.2 pg/ml). Ten patients were restudied after three months of nCPAP treatment. No decrease in ET-1 was observed.

Pulmonary function measurements during repeated environmental challenge of horses with recurrent airway obstruction (heaves)

OBJECTIVES

To evaluate the degree of reproducibility in clinical variables, blood gas measurements, and lung function variables, and the changes in these variables caused by exposure to moldy hay in naturally sensitized and control horses.

PROCEDURE

The magnitude of variation in arterial blood gas and pulmonary function measurements were evaluated in a model of naturally acquired heaves. Horses with heaves and similarly aged control horses were studied prior to moldy hay challenge and again after the horses with heaves manifested clinical signs of airway obstruction. This cycle of testing was repeated 3 times to determine the variation of the before and after challenge measurements. Variables evaluated for repeatability included: clinical score; arterial O2 and CO2 tensions; pulmonary function variables, such as breathing rate (f), tidal volumes, and flow rates; lung resistance (RL); dynamic compliance; and work of breathing (Wb).

RESULTS

Before challenge, significant differences observed between control horses and horses with heaves included clinical score, expiratory flow rate at near-end expiration, RL, and Wb. After exposure to moldy hay, variables measured in control horses were largely unchanged. However, in the afflicted horses, significant changes were observed for clinical score, arterial O2 and CO2 tensions, breathing rate, peak tidal inspiratory and expiratory flow rates, dynamic compliance, RL, and Wb, compared with prechallenge values and with control horses' postchallenge values. Analysis of the data revealed few statistically significant differences between repeats of challenges.

CONCLUSION

Horses afflicted with heaves manifest airway obstruction that can be measured in repeatable fashion.

Cardiac arrhythmias as a result of intravenous infusions of theophylline in patients with airway obstruction

The effect of intravenous theophylline upon the activity of creatinine kinase (CK) and its cardiac specific isoenzyme (CK-MB) and the frequency of cardiac arrhythmias were evaluated in 12 patients with bronchial asthma and spastic bronchitis. Measurements of the peak expiratory flow (PEF) were obtained prior to theophylline administration, immediately after the infusion and at 1, 3 and 6 hours, while serum theophylline levels were determined at the same time by enzyme immunoassay. Continuous 24-hour Holter monitoring of the electrocardiogram before the study and at the first day of the investigations was performed. CK-MB elevation was observed relating to the theophylline infusion. The CK-MB activity prior to theophylline administration was 10.87 +/- 5.2 units and 24.9 +/- 13.4 units at 5 minutes after termination of the infusion. The elevation lasted until the end of the observation period, being 29.4 +/- 17 units at 1 hour, 27.95 +/- 12.1 units at 3 hours and 34.9 +/- 13.9 at 6 hours. No statistically significant differences in CK activity were found. In most patients the heart rate was accelerated during the theophylline infusion and 4 patients developed clinically silent ventricular arrhythmias obviously related to the infusion. In one patient a 5-hour long bout of atrial fibrillation, which resolved spontaneously, was observed. No changes were found in the ST-T segment.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of nasal occlusion on the initiation of oral breathing in preterm infants

The ability to switch from nasal to oral breathing in response to nasal obstruction is crucial for survival, and has been suggested to be an important mechanism in preventing sudden infant death syndrome (SIDS). To know whether the ability to switch from nasal to oral breathing is uniformly present during the early neonatal period, we examined the effects of slow and fast nasal occlusions on the establishment of oral breathing in preterm infants. Slow occlusions were used to mimic more closely occlusions occurring spontaneously. We studied 17 healthy preterm infants [birth weight, 1830 +/- 27 g (mean +/- SE); study weight, 1800 +/- 109 g; gestational age, 32 +/- 1 weeks; postnatal age, 12 +/- 2 days]. We used a nosepiece with a nasal occluder and a flow-through system to measure ventilation. A CO2 sampling catheter at the mouth was used to detect oral breathing. Of 58 occlusions, 29 were slow [resistance increasing slowly from 0 to infinite (occlusion)], and 29 were fast (infinite elastance applied in < 1 sec). Oral breathing was always established following slow and fast occlusions. In 44% of the slow occlusions, oral breathing started before complete occlusion. Arousal was observed in 12/58 (17%) of all occlusions, occurring primarily after initiation of oral breathing. Oxygen saturation and respiratory rate decreased significantly following occlusions, from 96 +/- 0.6 to 87 +/- 1.2% and 49 +/- 2.8 to 38 +/- 2 breaths/min, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Obstructive sleep apnea and the hyoid: a revised surgical procedure

Obstructive sleep apnea syndrome results from a loss of muscular activity of pharyngeal dilators and airway collapse at the hypopharynx-base of tongue or the oropharynx-soft palate. The hyoid arch and its muscle attachments strongly affect hypopharyngeal airway patency and resistance. On the basis of these concepts and previous experience, a modified hyoid suspension procedure is presented. Fifteen consecutively treated surgical patients underwent an isolated modified hyoid suspension procedure to correct hypopharyngeal obstruction. Oropharyngeal-palatal obstruction had previously been corrected or was thought not to be a component of the obstruction. Treatment outcomes were based on objective polysomnographic data and subjective clinical correction of excessive daytime sleepiness. The polysomnographic data included analysis of the respiratory disturbance index and lowest oxyhemoglobin desaturation. On the basis of these criteria, 12 of 15 patients (75%) had correction of their excessive daytime sleepiness and marked improvement in their sleep disorder breathing. The mean preoperative respiratory disturbance index was 44.7 +/- 22.6, and the lowest oxyhemoglobin desaturation was 82% +/- 6%. The postoperative respiratory disturbance index and lowest oxyhemoglobin desaturation were 12.8 +/- 6.9 and 86% +/- 5%, respectively. The modified hyoid suspension procedure appears to offer significant adjunctive treatment for hypopharyngeal obstruction in obstructive sleep apnea syndrome.

Ability of new lung function tests to assess methacholine-induced airway obstruction in infants

We assessed the ability of innovative lung function tests to detect bronchial obstruction induced by methacholine bronchial challenge. Fifty-five recurrently wheezy infants (mean age 16 +/- 5.2 months) free of respiratory symptoms underwent baseline lung function tests. Forty-two completed the methacholine challenge. Maximal flow at functional residual capacity (VmaxFRC) was obtained using the squeeze technique; compliance and resistance of the respiratory system (Crs, Rrs) was measured with the passive expiatory flow volume technique; tidal volume breathing patterns were analyzed from recordings of respiratory rate (RR), tidal volume (VT), and inspiratory time divided by total cycle of duration (Ti/Ttot). Expiratory tidal flow volume (V/VT) curves were described with multiple indices such as the ratio of expiratory time necessary to reach peak tidal expiratory flow (Fpet) to expiratory time (Tme/Te). Transcutaneous oxygen tension (PtCO2) was measured as an indicator of response to methacholine challenge. Of 42 infants 41 responded to methacholine by a change > or = 2 standard deviations from baseline values. The mean SD unit changes were 9.8 in PtCO2, 3.7 for VmaxFRC, 2.8 for Crs, 2.09 for Rrs, 3.1 for RR, 1.6 for Ti/Ttot, 2.2 for Tme/Te 3.9 for PFVt. We conclude that these noninvasive lung function tests, especially VmaxFRC and Fpet, can be used to detect minor or moderate airway obstruction. Further studies are needed to determine the value of the tests in assessing bronchial disease and effects of its treatment.

Accuracy of nine commercially available pulse oximeters in monitoring patients with chronic respiratory insufficiency

9 pulse oximeters (BIOX-III, Nellcor 250, Jaeger CNS, Micro2), Pulsox-8, Oxycount, PulsOXImeter, PalcoLabs and Pulsox-7) were studied in 90 COPD patients. The transcutaneus oxygen saturation (SaO2%) was compared with arterial oxygen saturation calculated simultaneously with drawn blood samples (AVL-995). The measurement of error distribution and the cumulative distribution function (CDF) of measurement errors allows ranking of the pulse oximeters, which can be divided in 3 groups. We conclude that the accuracy of the tested nine pulse oximeter does not enable precise absolute measurements, specially at lower oxygen saturation ranges.

Airflow obstruction and monocyte TNF release in coal workers

Respiratory health of 102 retired coal miners was assessed by chest radiographs, lung function measurements, and questionnaires, and related to tumor necrosis factor-alpha (TNF-alpha) production by blood monocytes upon priming with different stimuli. The objective was to assess a possible relationship between airflow obstruction and TNF-alpha production in retired coal workers. No significant differences in lung function were observed between cases of coal workers' pneumoconiosis (CWP) (n = 27; > %) and references (n = 75; = > %), nor was the effect of cumulative exposure on flow volume or impedance parameters significant. TNF-alpha release upon stimulation of blood monocytes with coal mine dust was significantly increased in cases with International Labour Organisation (ILO) score 0/1 (doubtful cases) compared to references and cases with a higher ILO score. Airflow limitation defined either as a FEV1 < 80% (N = 10; 5 cases of CWP) or as a resonance frequency > 15 Hz accompanied by a negative frequency dependence of resistance (N = 9; 4 cases of CWP) was significantly related to high levels of TNF-alpha release upon stimulation with endotoxin and silica, with silica showing the strongest relation. These data suggest that in this group airflow limitation is associated with an increased expression of inflammatory mediators indifferent of the presence of pneumoconiosis.

Plasma acetylsalicylic acid and salicylic acid levels during aspirin provocation in aspirin-sensitive subjects

The ability of aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) to inhibit the cyclo-oxygenase which catalyzes formation of prostaglandins appears to be central to the mechanisms involved in aspirin sensitivity. We have investigated whether the plasma levels of acetylsalicylic acid (ASA) and its main metabolite salicylic acid (SA) at the time of intolerance reactions correspond with the concentrations required for enzyme inhibition in vitro. Twelve aspirin-sensitive and 15 aspirin-tolerant subjects were followed during provocation with aspirin. ASA and SA concentrations in plasma were determined by HPLC. After oral provocation (up to 460 mg cumulative dose), the levels of ASA and SA in plasma were equivalent in aspirin-sensitive and aspirin-tolerant subjects. For the aspirin-sensitive subjects, at the time of adverse reaction, the concentration range was 2.9-33.3 microM for ASA and 18.1-245 microM for SA. Oral provocation with sodium salicylate yielding 10-fold higher SA levels did not elicit intolerance reactions. Statistically significantly lower levels of ASA and SA (P < or = 0.01) evoked airway obstruction, as compared with merely extrapulmonary symptoms. Bronchial absorption of aspirin was found after inhalation of lysine-aspirin and was comparable in asthmatic and nonasthmatic subjects. In three aspirin-sensitive subjects who developed airway obstruction, the plasma levels for ASA and SA were 0.9-2.6 microM and 0.0-6.7 microM, respectively. In conclusion, the plasma levels of ASA reached at the time of a positive reaction are of the magnitude known to inhibit cyclo-oxygenases. Neither differences in bioavailability of ASA nor the formation of SA seems to contribute to the aspirin-elicited reactions.

Effects of repetitive airway obstruction on O2 saturation and systemic and pulmonary arterial pressure in anesthetized dogs

We examined the effects of multiple repetitive airway obstruction (RAO) on arterial oxygen saturation (SaO2) and pulmonary and systemic arterial pressure in eight anesthetized spontaneously breathing dogs. SaO2 was monitored at the tongue with a pulse oximeter. RAO created by an electrical valve that was attached to a tracheal cannula was alternated with seven consecutive spontaneous breaths until the nadir SaO2 (nSaO2) became constant or decreased to less than 35%. Tracheal occlusion durations of 15, 30, 45 and 60 s were chosen arbitrarily. In each animal nSaO2 decreased with every trial number in an exponential fashion, and the rate of nSaO2 fall was greater for the longer occlusion duration. In each animal the increases in pulmonary arterial pressure (PAP) and systemic arterial pressure (SAP) were inversely related to the nSaO2 values, and the relationship between nSaO2 and PAP or SAP was identical for all occlusion durations. Moreover, when the animals breathed pure oxygen and SaO2 did not decrease, there were no significant increases in the PAP and SAP at similar levels of pleural pressure (Ppl). In another six dogs, the effects of RAO on PAP and SAP were compared with those of intermittent hypoxic exposure without apnea, which was achieved by the inhalation of hypoxic gas (4 to 6% O2, 5% CO2 in N2) instead of RAO, to examine the effects of interruption of ventilation. The relationships between nSaO2 and both pressures did not differ significantly from those during RAO.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemoglobin desaturation during sleep and daytime in patients with cystic fibrosis and severe airway obstruction

Transcutaneous hemoglobin saturation by pulse oximetry was evaluated during sleep and for 2-3 h during the day in 31 patients with cystic fibrosis (median age 15.2 years; range 7.6-33.6 years) and severe airway obstruction. Pulse oximetry readings were analyzed as a cumulative percentage of time in which oxygen saturation was < 90% during both sleep and daytime. Each patient was also examined using clinical and radiological scores, spirometry and arterial blood-gas analysis. The agreement between arterial and transcutaneous saturation was evaluated in 29 patients. The difference between transcutaneous and arterial saturation was 2.4 +/- 2.0% and it increased as arterial saturation decreased. Clinical and radiological scores and spirometry parameters showed a poor correlation with both overnight and daytime desaturation. An arterial saturation < 94% may indicate a risk of consistent desaturation. This occurred for more than 50% of the time in 11 of 20 patients during sleep and in 5 of 20 patients during daytime hours.

Effect of hyperoxia on the arousal response to airway occlusion during sleep in normal subjects

The effect of hyperoxia on the arousal response to airway occlusion during non-rapid eye movement (NREM) sleep was studied in six normal male subjects with a mean age (+/- SD) of 23.5 +/- 8.7 yr by testing the response to the occlusion of a face mask covering the nose and mouth. Occlusion trials while the subjects breathed room air (room air condition) were alternated with trials in which subjects breathed a mixture of room air and oxygen adjusted to maintain a sleeping baseline arterial oxygen saturation of 98% (hyperoxic condition). The time to arousal (mean +/- SEM) was significantly longer during oxygen administration (4.1 +/- 4.5 versus 28.9 +/- 4.6 s; p < 0.002). The maximal deflections in airway pressure were measured at a supraglottic location during airway occlusion to reflect the degree of inspiratory effort. The maximal airway suction pressure preceding arousal did not differ between the room air (27.4 +/- 5.4 cm H2O) and hyperoxic conditions (26.6 +/- 5.9 cm H2O). Conversely, the rate of increase in inspiratory effort (maximal pressure) during occlusion was decreased by oxygen administration. We conclude that hyperoxia prolongs the time to arousal after airway occlusion by decreasing the rate of increase in the magnitude of inspiratory efforts, but it does not change the arousal threshold.

Translaryngeal jet ventilation and end-tidal PCO2 monitoring during varying degrees of upper airway obstruction

STUDY OBJECTIVES

To explore the ventilatory adequacy of translaryngeal jet ventilation (TLJV) during partial upper airway obstruction and the usefulness of monitoring end-tidal CO2 (PETCO2) during this condition.

DESIGN

Prospective, nonrandomized, sequential crossover design.

SETTING AND PARTICIPANTS

Apneic dog model (five dogs; mean weight, 23 kg).

INTERVENTIONS

Animals were intubated with a 9.0-mm endotracheal tube with the tip positioned above the cricothyroid membrane. Upper airway obstructions of 40%, 69%, and 80% were created. TLJV was performed through the cricothyroid membrane using a 13-gauge catheter with 100% oxygen, 45 psi, 15 breaths per minute, and 30% inspiratory time for 15 minutes at each upper airway obstruction. Data collected at baseline (no upper airway obstruction) and one-minute intervals included arterial blood pressures, continuous PaCO2 measurements, and PETCO2 at the TLJV catheter tip and above the level of obstruction. Arterial blood gases were obtained at 0 and 15 minutes. Data were analyzed using Pearson's correlation, analysis of variance, and Turkey's multiple comparisons (significance, P less than .05).

MEASUREMENTS AND RESULTS

Baseline values for all variables did not significantly differ at the onset of each testing phase. Mean pH increased significantly from baseline during 69% upper airway obstruction (7.36 to 7.54, P less than .05) and 80% upper airway obstruction (7.39 to 7.61, P less than .01). Mean PaCO2 decreased significantly from baseline during all upper airway obstructions: 40% upper airway obstruction (39.9 to 33.6 mm Hg, P less than .01), 69% upper airway obstruction (38.3 to 25.6 mm Hg, P less than .001), and 80% upper airway obstruction (36.2 to 18.2 mm Hg, P less than .001). PaCO2, PETCO2, and pH differed significantly between each level of upper airway obstruction (P less than .01). PETCO2 was significantly correlated with PaCO2 (r = .84, P less than .001) and did not significantly differ from PaCO2. No signs of barotrauma were observed in any animal at any degree of upper airway obstruction.

CONCLUSION

TLJV during partial upper airway obstruction in our model provided safe and adequate-to-supranormal minute ventilation. In fact, marked hypocapnia and alkalemia occurred at levels of 69% and 80% upper airway obstruction, thus dispelling concepts that TLJV may cause hypercapnia during partial upper airway obstruction. PETCO2 correlates well with PaCO2 and may be valuable for monitoring ventilation when using TLJV in the nonobstructed or partially obstructed upper airway.

Sleep related upper airway obstruction in a cohort with Down's syndrome

The prevalence of sleep related upper airway obstruction (UAO) was studied in a cohort of 34 children with Down's syndrome from a geographically defined area. Thirty two (94%) of the children, ranging in age between 0.1 and 4.9 years (median 1.4), underwent full clinical assessment for UAO including parental questionnaires and overnight tape recordings of chest wall movements and arterial oxygen saturation (SaO2). Compared with controls, children with Down's syndrome had (a) an increased incidence of stridor and chest wall recession during sleep, (b) an increased frequency of a pattern on inspiration indicating increased upper airway resistance, (c) a reduced baseline oxygen saturation (having excluded recordings on four children with potential for right to left intracardiac shunting), and (d) an increased number of episodes with SaO2 less than or equal to 90% despite continued chest wall movements. At their initial assessment seven children (22%) had evidence of UAO. The 18 youngest children (less than or equal to 1.7 years) underwent repeated recordings and clinical assessment until they had all reached 2 years of age. A further three were found to have developed UAO. Sleep related UAO is a common problem in children with Down's syndrome, occurring in 10 of 32 (31%) of this population based sample.

[Increase in blood pressure due to continuous obstructive snoring]

Sleep-related breathing disorders can strain the cardiovascular system. Link-ups with arterial hypertension have been confirmed in obstructive or mixed sleep apnoea which is characterised by discontinuous nocturnal snoring. On the other hand, it is known that arterial hypertension is very frequently seen in snorers. The present study deals with short-term, breathing-related blood pressure patterns and blood pressure changes during the snoring phase. 18 obstructive snoring phases were identified in 4 male patients aged 50 years (42-65), Broca index 136 (119-171). Polysomnographic measurements were carried out in the sleep laboratory and the blood pressure was continuously recorded via the a. brachialis. The short-term breathing-dependent blood pressure changes were systolic 10.8 (10-30) mmHg at the beginning and 17.5 (10-30) mmHg at the end of the snoring phase (P less than 0.01). Diastolically there was a difference of 9.4 (5-15) mmHg versus 13.9 (5-25) mmHg (P less than 0.01). During the snoring phases the systolic blood pressure increased from 140.3 (120-190) mmHg to 170.0 (145-235) mmHg and the diastolic pressure from 69.7 (50-110) mmHg to 93.1 (70-120) mmHg. The study proves that blood pressure increases occur not only in apnoeic snoring but also in continuous obstructive snoring. It is suspected that these changes are responsible for the high frequency of arterial hypertension among continuous snorers.

Increased airways reactivity after smoke inhalation

13 fire victims who required treatment after smoke inhalation underwent lung function assessment within 3 days of injury and 3 months later. Initial airways hyperreactivity improved over this period, but FEV1 and airways specific conductance did not change significantly. There was a strong correlation between exposure carboxyhaemoglobin concentration (an indicator of smoke exposure) and initial airways specific conductance (r + 0.79; p = 0.006). Airways obstruction after smoke inhalation in house fires may be more common and more persistent than is generally recognised. Early lung function tests would allow the incidence of pulmonary complications after smoke inhalation and the potential benefits of early use of inhaled antiinflammatory drugs to be assessed.

High pressure percutaneous transtracheal ventilation: the use of large gauge intravenous-type catheters in the totally obstructed airway

Percutaneous transtracheal ventilation using a large gauge intravenous-type catheter can be used successfully in the setting of complete upper airway obstruction in animals. In this study, using a large animal model, satisfactory oxygenation and ventilation was achieved by inversely varying the catheter size and the inspiration to expiration ratio (I:E). Specifically, 30 to 63 kg ruminants with an obstructed upper airway were resuscitated for 30 minutes from a hypoxic, hypercarbic, and acidotic state using 12- and 14-gauge catheters connected to a 50 psi oxygen source via a two-way valve with an I:E of 1:4 and 1:9 seconds, respectively. Shorter expiratory time or increased inspiratory time with these intravenous catheters resulted in significant hemodynamic compromise, barotrauma, inadequate carbon dioxide elimination, acidemia, and frequent death.

Pulmonary gas exchange after multiple airway occlusion by beads in the dog

Patients with asthma frequently show a bimodal distribution of ventilation-perfusion (VA/Q) ratios. One mode is centered on a VA/Q ratio of near normal value, whereas the other has a very low VA/Q ratio. There is usually almost no perfusion of unventilated units. We have suggested that this bimodal pattern is caused by complete obstruction of some airways with ventilation of their distal alveoli through collateral channels. To test this hypothesis we occluded airways of anesthetized dogs with beads of 1.6, 2.4, and 4.8 mm in diameter, and measured VA/Q distributions using the multiple inert gas elimination technique. Beads were inserted via a bronchoscope until the Pao2 fell by 20 mm Hg, or its value was less than 70 mm Hg. Occlusion of small airways (1.6 mm diameter) resulted in a mild increase in dispersion of VA/Q ratios. With 2.4 mm beads, the dispersion increased further. By contrast, all dogs given 4.8 mm beads showed a bimodal distribution of VA/Q ratios. All animals developed some shunt. We interpret these results as showing that when 1.6 mm airways are occluded, collateral ventilation to distal units is so efficient that ventilation is only mildly impaired; however, as occlusion becomes more proximal, collateral ventilation is less effective until with 4.8 mm beads, the ventilation of distal units is so poor that a bimodal pattern develops. The results suggest that the bimodal distributions seen in asthma are compatible with complete obstruction of some airways, and that the levels of obstruction may affect the pattern of VA/Q distribution.

Increases in plasma concentrations of a prostaglandin metabolite in acute airway obstruction

Plasma concentrations of a stable prostaglandin F2 alpha metabolite were measured by radioimmunoassay during and after recovery from acute airway obstruction in 15 infants. Mean (SEM) metabolite concentrations (ng/l) in plasma obtained both before (1033 (418)) and after (1470 (413)) initial treatment for airway obstruction were significantly higher than those obtained from the same subjects after resolution of the obstruction--25.5 (6.6)--and those obtained from two comparison groups. Infants positive for respiratory syncytial virus (mean 1122 (227)) had significantly higher concentrations than those who were negative (207.6 (46)). Additionally, seven subjects with a history of recurrent wheezing after resolution of airway obstruction had a significantly higher mean level (3500 (1400)) during attacks of airway obstruction than those without (600 (100)). These data suggest that prostaglandin F2 alpha mediates respiratory inflammation in airway obstruction and that trials of specific anti-inflammatory agents for the treatment of airway obstruction may be warranted.