Automated Quantitative Lung CT Improves Prognostication in Non-ICU COVID-19 Patients beyond Conventional Biomarkers of Disease

(1) Background: COVID-19 continues to represent a worrying pandemic. Despite the high percentage of non-severe illness, a wide clinical variability is often reported in real-world practice. Accurate predictors of disease aggressiveness, however, are still lacking. The purpose of our study was to evaluate the impact of quantitative analysis of lung computed tomography (CT) on non-intensive care unit (ICU) COVID-19 patients' prognostication; (2) Methods: Our historical prospective study included fifty-five COVID-19 patients consecutively submitted to unenhanced lung CT. Primary outcomes were recorded during hospitalization, including composite ICU admission for the need of mechanical ventilation and/or death occurrence. CT examinations were retrospectively evaluated to automatically calculate differently aerated lung tissues (i.e., overinflated, well-aerated, poorly aerated, and non-aerated tissue). Scores based on the percentage of lung weight and volume were also calculated; (3) Results: Patients who reported disease progression showed lower total lung volume. Inflammatory indices correlated with indices of respiratory failure and high-density areas. Moreover, non-aerated and poorly aerated lung tissue resulted significantly higher in patients with disease progression. Notably, non-aerated lung tissue was independently associated with disease progression (HR: 1.02; p-value: 0.046). When different predictive models including clinical, laboratoristic, and CT findings were analyzed, the best predictive validity was reached by the model that included non-aerated tissue (C-index: 0.97; p-value: 0.0001); (4) Conclusions: Quantitative lung CT offers wide advantages in COVID-19 disease stratification. Non-aerated lung tissue is more likely to occur with severe inflammation status, turning out to be a strong predictor for disease aggressiveness; therefore, it should be included in the predictive model of COVID-19 patients.

Factors influencing negative surgical outcomes in adult pectus excavatum patients undergoing Nuss procedure

BACKGROUND

This study aimed to examine the factors associated with the negative outcomes of Nuss procedure in adult pectus excavatum (PE) patients.

METHODS

Forty-seven adult PE patients were enrolled in this study. Mimics 21.0 software (Materialise) was used to reconstruct the preoperative and postoperative three-dimensional (3D) thoracic model. The preoperative and postoperative pulmonary volumes and function parameters were compared. The diaphragm positions were localized, and the anteroposterior diameter (APD) of the thoracic cavity was calculated using neoteric methods. Binary logistic regression was used to reveal the association between clinical factors and altered pulmonary parameters.

RESULTS

Postoperative lung volumes in adult PE patients decreased significantly (P<0.001). The mean preoperative lung volume was 4,592.82±946.54 cm³, which reduced to 3,976.26±867.35 cm³ postoperatively. The rate of postoperative lung volume reduction was approximately 12.1%. Physiologically, forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and peak expiratory flow (PEF) significantly decreased after Nuss procedure, and a near 10% reduction in FVC was observed. Diaphragm elevation was positively associated with decrease in lung volumes [odds ratio (OR) =40.51; P=0.011; 95% confidence interval (CI), 2.37-692.59]. The presence of reduced thoracic APDs was significantly associated with negative pulmonary function results (OR =1.21; P=0.008; 95% CI, 1.050-1.388).

CONCLUSIONS

This study reveals that thoracic APD reduction and diaphragm elevation are associated with decreased postoperative pulmonary volumes and function in adult PE patients. Nuss procedure for adult patients with PE must be considered cautiously by thoracic surgeons, especially in patients who expect to improve their cardiopulmonary function.

Validating the inspired sinewave technique to measure the volume of the 'baby lung' in a porcine lung-injury model

BACKGROUND

Bedside lung volume measurement could personalise ventilation and reduce driving pressure in patients with acute respiratory distress syndrome (ARDS). We investigated a modified gas-dilution method, the inspired sinewave technique (IST), to measure the effective lung volume (ELV) in pigs with uninjured lungs and in an ARDS model.

METHODS

Anaesthetised mechanically ventilated pigs were studied before and after surfactant depletion by saline lavage. Changes in PEEP were used to change ELV. Paired measurements of absolute ELV were taken with IST (ELV_IST) and compared with gold-standard measures (sulphur hexafluoride wash in/washout [ELV_SF6] and computed tomography (CT) [ELV_CT]). Measured volumes were used to calculate changes in ELV (ΔELV) between PEEP levels for each method (ΔELV_IST, ΔELV_SF6, and ΔELV_CT).

RESULTS

The coefficient of variation was <5% for repeated ELV_IST measurements (n=13 pigs). There was a strong linear relationship between ELV_IST and ELV_SF6 in uninjured lungs (r²=0.97), and with both ELV_SF6 and ELV_CT in the ARDS model (r²=0.87 and 0.92, respectively). ELV_IST had a mean bias of -12 to 13% (95% limits=±17 - 25%) compared with ELV_SF6 and ELV_CT. ΔELV_IST was concordant with ΔELV_SF6 and ΔELV_CT in 98-100% of measurements, and had a mean bias of -73 to -77 ml (95% limits=±128 - 186 ml) compared with ΔELV_SF6 and -1 ml (95% limits ±333 ml) compared with ΔELV_CT.

CONCLUSIONS

IST provides a repeatable measure of absolute ELV and shows minimal bias when tracking PEEP-induced changes in lung volume compared with CT in a saline-lavage model of ARDS.

Optimizing respiratory function assessments to elucidate the impact of obesity on respiratory health

There is an increasing prevalence of obesity worldwide and its impact on respiratory health is of significant concern. Obesity affects the respiratory system by several mechanisms, including by direct mechanical changes due to fat deposition in the chest wall, abdomen and upper airway, as well as via systemic inflammation. The increased mechanical load in obese individuals leads to reduced chest wall and lung compliance and increased work of breathing. While there is generally minimal effect on spirometric values, as body mass index increases, the expiratory reserve volume, and hence functional residual capacity, reduces, often approaching residual volume in more severe obesity. The majority of evidence however suggests that obese individuals free from lung disease have relatively normal gas exchange. The link between asthma and obesity, while initially unclear, is now recognized as being a distinct asthma phenotype. While studies investigating objective markers of asthma have shown that there is no association between obesity and airway hyper-responsiveness, a recent working group identified obesity as a major risk factor for the development of asthma in all demographic groups. Although the temptation may be to attribute obesity as the cause of dyspnoea in symptomatic obese patients, accurate respiratory assessment of these individuals is necessary. Lung function tests can confirm that any altered physiology are the known respiratory consequences of obesity. However, given that obesity causes minimal changes in lung function, significant abnormalities warrant further investigation. An important consideration is the knowledge that many of the respiratory physiology consequences of obesity are reversible by weight loss.

Evaluation of postoperative change in lung volume in adolescent idiopathic scoliosis: Measured by computed tomography

BACKGROUND

Change in total lung volume after surgical correction in adolescent idiopathic scoliosis (AIS), measured by computed tomography (CT), has not been studied previously. The primary objective of this study was to measure the change in lung volume between pre and postoperative AIS using low-dose CT and secondary objective was to investigate its relationship to postoperative pulmonary complications.

MATERIALS AND METHODS

55 AIS patients underwent surgery for correction and fusion using a posterior only approach and pedicle screws. Pre and postoperative lung volumes were measured using a 3-dimensional (3D) whole spine CT (low dose protocol: Tube current, 60 mA; tube voltage 120 kV). Postoperative low dose CT was undertaken at 4 weeks after operation to evaluate the acute changes of postoperative lung volumes and pulmonary complications. The software that was used recognizes the "air density shade" of the lung and the volume of every section of the lung. The software then automatically calculates total lung volume by summation of all section volumes. The relationships between postoperative pulmonary complications and changes in lung volume on low dose CT as well as preoperative forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) were calculated using logistic regression analysis.

RESULTS

There was a decrease of 12% ± 23.2% in total lung volume postoperatively on 3D low dose CT (P < 0.001). Thirteen patients had increased lung volume while 42 had decreased lung volume postoperatively. Pulmonary complications were treated without severe sequale. Lung volume increased by 19.65% ± 19.84% in 13 patients and decreased by 21.85% ± 13.32% in 42 patients (P = 0.647). Lung volume was increased in patients whose preoperative lung volume, FEV1 and FVC were lower than in patients whose values were higher (r = -0.273, -0.291 and - 0.348; P = 0.044, 0.045 and 0.015, respectively). Postoperative lung volume was also increased when intraoperative fluid administration was larger and operative time was longer (r = 0.354, 0.417 and P = 0.008, 0.002, respectively). There was a statistically significant negative correlation in the change of lung volume in female patients when compared with male patients (r = -0.294, P = 0.03).

CONCLUSION

Patients with AIS who have preoperative reduced lung volumes or lung functions can achieve further increased lung volume after surgical correction. Pulmonary complications during perioperative period were mostly treated with proper management without severe sequale. Therefore, although surgery for AIS is considered to be a high risk procedure, we can recommend to correct spine deformity in patients with severe AIS in order to improve lung function and long term prognosis.

Lung volume changes during cleaning of closed endotracheal suction catheters: a randomized crossover study using electrical impedance tomography

BACKGROUND

Airway suctioning in mechanically ventilated patients is required to maintain airway patency. Closed suction catheters (CSCs) minimize lung volume loss during suctioning but require cleaning post-suction. Despite their widespread use, there is no published evidence examining lung volumes during CSC cleaning. The study objectives were to quantify lung volume changes during CSC cleaning and to determine whether these changes were preventable using a CSC with a valve in situ between the airway and catheter cleaning chamber.

METHODS

This prospective randomized crossover study was conducted in a metropolitan tertiary ICU. Ten patients mechanically ventilated via volume-controlled synchronized intermittent mandatory ventilation (SIMV-VC) and requiring manual hyperinflation (MHI) were included in this study. CSC cleaning was performed using 2 different brands of CSC (one with a valve [Ballard Trach Care 72, Kimberly-Clark, Roswell, Georgia] and one without [Portex Steri-Cath DL, Smiths Medical, Dublin, Ohio]). The maneuvers were performed during both SIMV-VC and MHI. Lung volume change was measured via impedance change using electrical impedance tomography. A mixed model was used to compare the estimated means.

RESULTS

During cleaning of the valveless CSC, significant decreases in lung impedance occurred during MHI (-2563 impedance units, 95% CI 2213-2913, P < .001), and significant increases in lung impedance occurred during SIMV (762 impedance units, 95% CI 452-1072, P < .001). In contrast, cleaning of the CSC with a valve in situ resulted in non-significant lung volume changes and maintenance of normal ventilation during MHI and SIMV-VC, respectively (188 impedance units, 95% CI -136 to 511, P = .22; and 22 impedance units, 95% CI -342 to 299, P = .89).

CONCLUSIONS

When there is no valve between the airway and suction catheter, cleaning of the CSC results in significant derangements in lung volume. Therefore, the presence of such a valve should be considered essential in preserving lung volumes and uninterrupted ventilation in mechanically ventilated patients.