[Dynamic analysis of airway temperature in dogs breathing cold air].

Exercise in cold, dry air induces bronchoconstriction. However, the time course of airway cooling during the breathing of cold air has not been investigated. In this study in dogs, the temperatures of tracheal gas and the tracheal wall were measured continuously while the animal was breathing cold air at approximately 4.5 degrees C. The temperature of the tracheal gas decreased during the inspiratory phase, increase slightly early in the expiratory phase, and then decreased to the level at end-expiration. The lowest temperature of the tracheal gas decreased significantly, from 29.7 +/- 2.4 degrees C (mean +/- SD) to 25.7 +/- 2.8 degrees C. The highest temperature also changed significantly, but the decrease was less than 1 degree C. The lowest temperature of the tracheal wall decreased from 31.1 +/- 2.6 degrees C to 30.5 +/- 2.5 degrees C during cold-air breathing, but the difference was not significant. When a dog inspired deeply during a cough, the temperature of tracheal gas did not decrease linearly with the progression of inspiration. However, the decrease in the tracheal wall temperature was almost directly proportional to inspiratory volume. We concluded that both the tracheal gas and the tracheal wall temperatures were resistant to cooling with cold-air breathing. It remains uncertain whether rapid, deep breathing during exercise decreased the tracheal wall temperature.

[Early replacement of intravenous aminophylline administration with oral theophylline in treating acute exacerbation of asthma].

Intravenous (i.v.) administration of aminophylline has been used to relieve acute exacerbation of bronchial asthma for almost a century. Despite confidence in its effectiveness, controversy has arisen about its efficacy. We currently use aminophylline in the routine treatment of asthma since the drug is essentially useful. Continuous aminophylline infusion tends to be used rather haphazardly in hospital wards, and the criteria for termination of an infusion have not been clarified. We therefore attempted to determine: 1) whether continuous aminophylline infusion is actually beneficial, 2) whether the TDM (treatment drug monitoring) system can be used to establish a protocol for prescribed dosing after an early switch from i.v. to oral administration, and 3) whether adherence to the protocol would contribute to decreases in the duration of hospitalization and in medical expenses. Seventeen patients with acutely exacerbated asthma were enrolled in this study. Nine patients were prescribed oral theophylline on the second hospital day (p.o. group), while eight received continuous i.v. aminophylline (i.v. group). The serum theophylline concentrations were maintained in the therapeutic range in both groups. Peak flow, symptom scores, and QOL scores showed significant improvements in the p.o. group on the third hospital day. It might therefore be possible, by using the TDM system, to set the dosage of theophylline so that hospitalization is shortened.

Applicability of Hyland's Living with Asthma Questionnaire for Japanese asthmatic patients.

OBJECTIVE: To assess the applicability of Hyland's Living with Asthma Questionnaire (LWAQ, 1991), one of the international health-related quality of life scales, for Japanese asthmatic patients with reference to its reproducibility and validity. SUBJECTS AND METHODS: The LWAQ was given to randomly selected asthmatic patients on two occasions separated by a 12-week interval. RESULTS: The mean scale score in the first study (n=304) was 1.83 (range, 1.14-2.77) and logarithmic values of the scores approached normal distribution. The scale scores in the first and second (n=158) studies were well correlated (r=0.81), however, the mean score decreased (0.08) significantly. The questions were further separated into 11 domains. The sex-domain was notable for a low response rate (68%), and scale scores in the sleep-, colds- and sex-domains in the first study varied considerably from those of the other domains. Frequency distributions of scores in the five constructs (Hyland 1996) were not normal and, with the exception of the colds construct, the relations among the remaining four constructs were similar to those previously reported (Hyland 1996). CONCLUSION: Analysis using the mean scale score, domain and construct in the LWAQ is applicable to Japanese asthmatic patients.

[Crescent moon-type tracheobronchial malacia alleviated by placement of stents in trachea and main bronchi].

We encountered a case of crescent-type tracheobronchomalacia in a 54-year-old male smoker. The patient experienced extreme obstructive pulmonary changes but his FVC and DLco findings were within the normal ranges. Plain chest X-ray films indicated tracheal narrowing, a diagnosis that was confirmed by fiberoptic bronchoscopy. Two Z-stents were implanted in the trachea but the patient's symptoms did not subside. Thoracic computed tomography (CT) elucidated stenosis of both main bronchi at end-expiration. The implantation of Z-stents in the main bronchi remarkably alleviated the symptoms and improved peak expiratory flow. Six months after implantation, the tracheal stents broke. A favorable course was obtained by inserting an ultraflex stent inside the broken Z-stents. DLco is important to the diagnosis of tracheobronchomalacia, whereas peak expiratory flow and thoracic CT findings are useful in evaluating the effectiveness of treatment. We concluded that ultraflex stents should be the first choice for treatment of tracheal stenosis, and that Z-stents are appropriate for the treatment of bronchial obstruction.

Effectiveness of the fold plication method in lung volume reduction surgery.

OBJECT: The fold plication method is a new operative procedure for lung volume reduction surgery whereby the target area is obliterated by plicating the folded tissue using a knifeless stapler, without the use of bovine pericardium. The effectiveness of this new method was evaluated in patients with advanced pulmonary emphysema. PATIENTS AND METHODS: Two weeks before and 6 months after surgery, pulmonary function, static lung compliance, maximal esophageal pressure, maximal inspiratory and expiratory mouth pressures, 6-min walking distance and the Borg scale were determined in twenty consecutive patients who underwent video-assisted thoracoscopic unilateral surgery. RESULTS: There was an increase in forced expiratory volume in one second (31%), forced vital capacity, peak expiratory flow rate and maximal voluntary ventilation, and a decrease in functional residual capacity (-16%) measured by plethysmograph. Static lung compliance decreased, and maximal esophageal pressure, and maximal inspiratory and expiratory mouth pressures increased. The 6-min walking distance increased (20%) and the Borg scale decreased (5.9 to 3.5). CONCLUSION: The results compare favorably with those obtained with other methods. Thus, the fold plication method could be considered an alternative procedure for lung volume reduction surgery.

Respiratory-related bronchial rhythmic constrictions in the dog with extracorporeal circulation.

Respiratory-related bronchial rhythmic contraction was quantitatively analyzed in eight paralyzed dogs. The caliber of the fifth-generation bronchus was continuously measured as the pressure (Pbr) of a balloon-tipped catheter under the condition of complete immobilization due to extracorporeal oxygenation. Pbr changed rhythmically in synchrony with phrenic nerve activity (PNA) bursts. Rhythmic bronchial constriction started at 1.4 +/- 0.49 (SD) s after onset of PNA, reached a maximum level at 2.8 +/- 1.6 s after termination of PNA, and then decreased exponentially with a time constant of 6.9 +/- 2.5 s. When the respiratory rate of dogs increased at hypercapnia, the various bronchial contractions fused to behave like a tonic contraction. The rhythmic component of this contraction was separated and quantitatively analyzed. Each rhythmic Pbr amplitude linearly increased with increases in PNA amplitude, whereas the end-expiratory Pbr level was not significantly changed. Bilateral efferent nerve transection did not decrease the end-expiratory Pbr level. In response to electric stimulation of efferent nerve fibers, the bronchus did not maintain tonic contraction. We concluded that vagally mediated commands contract bronchial smooth muscle only intermittently and that most of bronchial resting tension may thus be attributed to the summation of rhythmic contractions.

Role of cholinergic neural transmission on airway resistance in the dog.

The unique contractile profiles of bronchial smooth muscle (Kondo et al., 1995) and its neural control were investigated by comparing responses of the bronchus and trachea to acute hypercapnia, stimulation of vagus efferent fibers before and after intravenous atropine, and intravenous acetylcholine in decerebrated and paralyzed dogs. During acute hypercapnia, airway resistance represented by peak airway pressure (Pedley et al., 1970) significantly increased as well as tracheal tension (Ttr). During electric stimulation of the vagal efferent fibers, Ttr increased and was sustained throughout the simulation period while the peak airway pressure was not maintained at the peak level. The peak Ttr and the airway resistance (Raw) calculated from ventilatory flow and airway pressure increased with increases in intensity of electric stimulation. Ttr reached its maximal level at an intensity 16 times of the threshold (T), while Raw became maximal at 4T. Although both the Ttr-stimulus intensity and Raw-intensity curves were shifted to the right by administration of intravenous atropine, the Raw curve shifted more to the right than the Ttr curve with the same dose of atropine. When muscular muscarinic receptors were directly stimulated by intravenous acetylcholine, Ttr once increased and then decreased promptly while peak airway pressure remained at a high level for a few minutes. These findings suggested that the bronchus is more sensitive to vagal efferent stimulation and susceptible to competitive antagonist of actylcholine than the trachea. In conclusion, the contractile profiles of the fifth-order bronchus we have reported (Kondo et al., 1995) were reflected in airway resistance, and the neuromuscular junction may be the site of adaptation of bronchoconstrictor response to motor nerve adaptation.

[Physiological role of respiratory-related bronchial constriction].

The respiration-related rhythmic constriction of the fifth-generation bronchi was analyzed in 11 tracheostomized dogs. During spontaneous breathing, the bronchial pressure (Pbr) estimated with a balloon-tipped catheter increased almost in parallel with the pleural pressure (Ppl) in the early inspiratory phase, but decreased in the late inspiratory phase. The parallel duration/inspiratory duration was 0.72 +/- 0.19 (mean +/- SD). This finding was more prominent in hypercapnia, but statistical significance was not obtained. When the efferent phrenic nerve fibers were electrically stimulated (pulse train, 0.1 ms, 30 Hz, 5 V, 2 s), Pbr changed almost in parallel with Ppl during the inspiratory phase, and expiration was completed significantly earlier than during spontaneous breathing (time constant 0.17 +/- 0.06 s vs 0.26 +/- 0.07 s). Bronchial constriction in early expiration may increase airway pressure and keep patency of the peripheral bronchi.

[Peak inspiratory flow during a diskhaler use in subjects unfamiliar with dry powder devices].

Dry power steroid was firstly introduced in Japan in 1998. We measured peak inspiratory flow (PIF) through a Diskhaler in the following groups: well-trained medical representative (EX group, n = 5), respiratory physicians (RP group, n = 19) and non-medical staffs (NM group, n = 31) who were not familiar with Diskhaler, and asthmatic patients who had been briefly trained by a video movie (TP group, n = 93). When PIF was less than 50 l/m dry powders were frequently remained in the brister. The mean PIF in the EX group was 96.1 +/- 12.6 l/m (mean +/- SD). Since the relationship between the PIF and airway pressure (Paw) during Diskhaler use was expressed as PIF = 16.3 square root of Paw-1.19 (r = 0.97), we calculated PIF from Paw measured by a handy barometer made by ourselves. The mean PIF in RP group was 77.0 +/- 30.1 l/m, and 36.8% of the subjects developed inappropriate PIF (i.e., above 100 l/m or below 50 l/m). In NM group the mean PIF was 53.5 +/- 20.4 l/m which was significantly higher than RP group. In this group 54.8% of the subjects yielded inappropriate PIF. The mean PIF in TP group was 64.9 +/- 24.5 l/m which was significantly lower than that in RP group. Those who developed inappropriate PIF occupied 43.2% of the RP subjects. We concluded that a quantitative presentation of PIF in mandatory to achieve an effective use of Diskhaler.

Contribution of airway resistance to airway pressure during mechanical ventilation: an experimental study.

Although airway resistance (R) is an important parameter of the pulmonary condition, its determination during mechanical ventilation is not easy. Most physicians estimate R from peak airway pressure during mechanical ventilation. We assessed the relationship between R and peak airway pressure by a computer simulation. The time course of airway pressure (Ptr) during mechanical ventilation was calculated from the airway pressure at end-inspiration and respiratory flow, allowing for the buffering effect of the dead space. The parameters for computer simulation were obtained from 5 paralyzed and mechanically ventilated dogs. The predicted Ptr curve was a function of airway resistance. Since R was not directly determined by the animal experiments, we determined R by using the Ptr curve most closely approximating the original Ptr curve as the true R. The R-peak tracheal pressure relationship predicted by computer simulation showed that the peak airway pressure increased almost linearly with increases in R. However, in computer simulation, when R was increased 10-fold from the value at airway relaxation, the peak airway pressure increased only 6-fold from the corresponding value. We conclude that peak airway pressure is a relatively insensitive parameter for the estimation of airway constriction during mechanical ventilation.