Evaluation of the trachea and intrathoracic airways by the acoustic reflection method in children with cystic fibrosis

The Strain on Airway Smooth Muscle During a Deep Inspiration to Total Lung Capacity

The deep inspiration (DI) maneuver entices a great deal of interest because of its ability to temporarily ease the flow of air into the lungs. This salutary effect of a DI is proposed to be mediated, at least partially, by momentarily increasing the operating length of airway smooth muscle (ASM). Concerningly, this premise is largely derived from a growing body of in vitro studies investigating the effect of stretching ASM by different magnitudes on its contractility. The relevance of these in vitro findings remains uncertain, as the real range of strains ASM undergoes in vivo during a DI is somewhat elusive. In order to understand the regulation of ASM contractility by a DI and to infer on its putative contribution to the bronchodilator effect of a DI, it is imperative that in vitro studies incorporate levels of strains that are physiologically relevant. This review summarizes the methods that may be used in vivo in humans to estimate the strain experienced by ASM during a DI from functional residual capacity (FRC) to total lung capacity (TLC). The strengths and limitations of each method, as well as the potential confounders, are also discussed. A rough estimated range of ASM strains is provided for the purpose of guiding future in vitro studies that aim at quantifying the regulatory effect of DI on ASM contractility. However, it is emphasized that, owing to the many limitations and confounders, more studies will be needed to reach conclusive statements.

Endonasal measurements by acoustic rhinometry in children: A preliminary study

The acoustic reflection method (ARM) is a non-invasive technique which uses the reflection of acoustic waves to measure the cross sectional area of nasal cavities in adults and patency of endotracheal tubes. Characteristics and volume of normal nasal cavities in pre-school children has so far not been studied.

OBJECTIVE

The aim of this study was to determine the optimal ARM recording and the minimal cross-sectional area (MCA) and volume (NV) values in healthy children.

DESIGN

Prospective monocentric study using the ARM in pre-school children (<6 years of age).

RESULTS - DISCUSSION

Seventy children (age 2 to 5) were included in the study. Reliable measures were difficult to obtain in children younger than 2 years of age. The use of a standard nosepiece and a single-use surgical filter enabled reliable, serial recordings. Mean MCA values were 0.46, 0.53 and 0.58 cm² in the 24-35, 36-47 and 48-60 months-old age groups, respectively. Mean NV values were 2.14, 2.59, and 2.86 cm³ in the same age groups. The MCA and NV values were significantly correlated with height, age and weight. In conclusion, the ARM is feasible in children over the age of 2 and seems to be a promising non-invasive tool to study the nasal cavity patency, anatomy, and volume.

Tracheomalacia is associated with lower FEV1 and Pseudomonas acquisition in children with CF

BACKGROUND

Tracheomalacia (TM) occurs in approximately 1 in 2,100 children. Because the trachea develops abnormally in animal models of cystic fibrosis (CF), we hypothesized this may also occur in children with CF, increasing their risk of TM.

PURPOSE

To examine the prevalence and clinical consequences of TM in children with CF.

METHODS

We studied children with CF born between 1995 and 2012. TM was defined as dynamic collapse of the trachea, and the severity was recorded as described in the chart. The effect of TM on patient outcomes, including FEV1 , CT changes, and acquisition of CF pathogens, was assessed using a longitudinal patient dataset.

RESULTS

Eighty-nine percent of children with CF had at least one bronchoscopy (n = 97/109). Fifteen percent of these children had TM described in any bronchoscopy report (n = 15/97). Of the patients with TM, eight had meconium ileus (P = 0.003) and all were pancreatic insufficient. Pseudomonas aeruginosa infection occurred 1.3 years earlier among children with TM (P = 0.01). Starting FEV1 values by age 8 were diminished by over 18% of predicted for patients with TM. Life-threatening episodes of airway obstruction occurred in 3 of 15 patients with CF and TM, including one leading to death. Gender, prematurity, and hepatic disease were not associated with TM. No difference was observed in the frequency of bronchiectasis.

CONCLUSIONS

TM is significantly more common in infants and children with CF than in the general population and is associated with airway obstruction and earlier Pseudomonas acquisition.

The acoustic reflection method for the assessment of paediatric upper airways

The acoustic reflection method (ARM) is based on the analysis of the reflection of an acoustic wave in the airway, allowing the calculation of its longitudinal cross-sectional area profile and airway resistance. The ARM represents a simple, quick and totally non invasive tool for the investigation of the upper airways, requiring minimal cooperation, which makes this technique particularly suitable for children. Normal values of the minimal cross sectional area of the upper airways in children have been recently published. The ARM has shown its utility in the investigation of the nasal cavity in healthy and diseased children and of the upper airways in children with various diseases such as mucopolysaccharidosis and cystic fibrosis. This simple, rapid, and inexpensive technique seems promising for the non-invasive investigation of the whole upper airway during wakefulness in children, both in health and disease, and may constitute a complementary or alternative method to explore and follow children with anomalies of the upper airways.

Pregnancy is associated with a decrease in pharyngeal but not tracheal or laryngeal cross-sectional area: a pilot study using the acoustic reflection method

BACKGROUND

The risk of difficult upper airway access is increased during pregnancy, especially in labor. Changes in upper airway calibre have been poorly studied during pregnancy. The acoustic reflection method is a non-invasive technique that allows a longitudinal assessment of the cross-sectional area of the upper airway from the mouth to carina. We used this technique to evaluate upper airway calibre during normal pregnancy.

METHODS

We conducted a prospective, single centre, observational study with a clinical and upper airway acoustic reflection method evaluation of healthy women during the first, second and third trimesters of pregnancy, and up to two days and one month after delivery.

RESULTS

Fifty women participated to the study. The mean pharyngeal cross-sectional area decreased between the first and third trimesters (P < 0.001) with no significant change of the minimal and mean tracheal cross-sectional areas. The Mallampati score increased during pregnancy between the first and third trimesters (P< 0.001).

CONCLUSION

Using measurements with the acoustic reflection method, normal pregnancy is associated with a significant reduction in the cross-sectional area of the pharynx and a concomitant increase in the Mallampati score. No change was observed in the minimal and mean tracheal cross-sectional areas.