Human adenovirus infection of 53 children in Jilin Province of China: the clinical and bronchoscopic features

Abstract Background: Human adenoviruses (HAdV) has many kinds of serotypes, of which type 7 can cause severe respiratory disease, especially pneumonia. From Oct 1st to Jan 31st a little outbreak of this type occured in Jilin province of China and led to quite severe pneumonia, therefore we did this retrospective study to summarize the clinical and bronchoscopic features in order to help pediatric physicians get better view of the infection. Methods: Nasopharyngeal swabs or bronchoalveolar lavage fluid (BALF) were collected from pediatric patients who were diagnosed with pneumonia in our department of the First hospital of Jilin University from Oct 1st 2018 to Jan 31st 2019. Then use immunofluorescence method (detect the nasopharyngeal swabs) or the next-generation sequencing technology (detect the BALF) to clarify the pathogen. Results: 53 children were confirmed to be infected with the HAdV, the mean age of infected children was 39.5(39.5±25.09）months, 56.6% were less than 36 months. The ratio rate between male and female was 1.3:1. Co-infection was quite common (75%), and happened in older group(p=.018). Bronchoscope was performed on 37 children, 45.9%(n=17) had micro-sputum-bolt in the small distal airway or in the BALF. With the help of the next-generation sequence technology, 11 were confirmed infected with HAdV-7. We followed up the patients for 6 months, 12 by CT and 41 by telephone call. In the CT follow-up group, 8 had “Mosaic sign” on lung CT, and 4 shows mild uneven ventilation. In telephone follow-up group 31 recovered well and had no symptoms, 10 had cough and tachypnea after moderate level of daily activities. Conclusion: A) Compared with previous data in our hospital, in the winter this year, a little outbreak happened in Jilin province of China. B) We infer that HadV-7 may be the prevalent strain. C) Before we get accurate etiology diagnosis, combining with the clinical symptoms, accessory results, the micro-sputum-bolt seen in the BALF when doing the electronic bronchoscope can give us some hints of HAdV infection.

Effect of methacholine on low-frequency mechanics of canine airways and lung tissue

We measured tracheal flow, tracheal pressure, and alveolar capsule pressure in four anesthetized paralyzed tracheostomized open-chest dogs. Lung impedance between 0.12 and 4.88 Hz was measured with a forced volume oscillation technique before and after the intravenous administration of methacholine (MCh). Before MCh administration, lung impedance was well described by a model featuring a single airway leading to an alveolar region surrounded by tissue with a continuous distribution of viscoelastic time constants as used by Hantos et al. (J. Appl. Physiol. 68: 849–860, 1990). After MCh, however, this model gave a poor fit to the impedances. The impedances were well accounted for, however, when the model was enhanced to include an extra time constant term, which we suspect is required to account for the uneven ventilation distribution produced by MCh. Airway impedance before MCh administration was well described by a simple resistance-inertance model, but a model incorporating serial inhomogeneity of ventilation was again required after MCh. Our results support those of previous studies indicating that the impedance of the normal dog lung is well described by a homogeneously ventilated viscoelastic tissue model. In contrast, our results after MCh administration show strong evidence of marked regional ventilation inhomogeneity in addition to the rheological properties of the tissues.

Ventilation inhomogeneity during controlled ventilation. Which index should be used?

Six indexes for diagnosing uneven ventilation by tracer gas washout were studied. The indexes were lung clearance index, mixing ratio, Becklake index, multiple-breath alveolar mixing inefficiency, moment ratio, and pulmonary clearance delay, all of which increase with impaired pulmonary gas mixing. In model lung tests, indexes that compared the actual washout curve with a calculated ideal curve (mixing ratio, multiple-breath alveolar mixing inefficiency, and pulmonary clearance delay) were unaffected by changes in tidal volume and series dead space, whereas the others varied markedly. In both spontaneously breathing and mechanically ventilated patients all indexes showed a significant difference between smokers and nonsmokers (P less than 0.002), but the indexes were somewhat different in their assessment of different ventilatory patterns. However, the mean value for all indexes, with the exception of mixing ratio, was smallest with a fast insufflation followed by an end-inspiratory pause. Any of the indexes may be useful if its limitations are recognized, but mixing ratio, multiple-breath alveolar mixing inefficiency, and pulmonary clearance delay seem preferable, because they are not affected by changes in tidal volume and dead space fraction.

Cardiac output by rebreathing in patients with cardiopulmonary diseases

Noninvasive estimates of cardiac output by rebreathing soluble gases (Qc) can be unreliable in patients with cardiopulmonary diseases because of uneven distribution of ventilation to lung gas volume and pulmonary blood flow. To evaluate this source of error, we compared rebreathing Qc with invasive measurements of cardiac output performed by indicator-dilution methods (COID) in 39 patients with cardiac or pulmonary diseases. In 16 patients with normal lung volumes and 1-s forced expiratory volumes (FEV1), Qc measured with acetylene [Qc(C2H2)] overestimated COID insignificantly by 2 +/- 9% (SD). In subjects with mild to moderate obstructive lung disease, Qc(C2H2) slightly overestimated COID by 6 +/- 15% (P = 0.11). In patients with restrictive disease or combined obstructive and restrictive disease, Qc(C2H2) underestimated COID significantly by 9 +/- 14% (P less than 0.04). The magnitude of the discrepancy between Qc and COID correlated with size of the volume rebreathed and an index of uneven ventilation calculated from helium mixing during rebreathing that determined a dead space to inspired volume ratio (VRD/VI). Rebreathing volumes less than 40% of the predicted FEV or VRD/VI of 0.4 or greater identified all subjects with a discrepancy between Qc(C2H2) and COID of 20% or greater.

Uneven gas mixing during rebreathing assessed by simultaneously measuring dead space

To evaluate the rate of gas mixing in human lungs during rebreathing maneuvers used to measure pulmonary tissue volume (Vt) and pulmonary capillary blood flow (Qc), we devised a method to determine the dead space during rebreathing (VRD). Required measurements are initial concentration of a foreign inert insoluble gas in the rebreathing bag, first mixed expired concentration, equilibrated concentration, volume inspired, and volume of the first expired breath. In subjects breathing rapidly at 30 breaths/min with inspired volumes in excess of 2 liters, VRD had values three or more times greater than the predicted anatomical dead space (VD). Breath holding after the first inspiration progressively diminished VRD so that after 10–15 s, it approximately equaled predicted VD. VRD measured with helium was smaller than VRD measured with sulfur hexafluoride. The reported degree of uneven ventilation from gravitational forces in normal humans can account for only about one-third of the difference between VRD and VD. These findings support the concept that mixing by diffusion between peripheral parallel airways is incomplete at normal breathing rates in humans and can result in errors as high as 25% in Vt and Qc.