Pulmonary pathophysiology and lung mechanics in anesthesiology: a case-based overview

Respiratory pattern complexity in newly-diagnosed asthmatic patients

BACKGROUND

The intensity of respiratory symptoms and expiratory airflow limitations in asthma fluctuate over time. Some studies have reported variable complexity of the respiratory patterns in asthmatic patients. Thus, we conducted a novel study to assess the correlation between asthma severity and breathing pattern dynamics in newly-diagnosed asthmatic patients.

METHODS

A total of 20 newly-diagnosed asthmatic patients (7 male, 13 female) and 20 healthy cases (11 male, 9 female) were included. The respiratory patterns of all participants and the asthma severity for asthmatic patients were measured using a spirometer (before and after a bronchodilator exposure) and airflow recorder, respectively. The peak-to-peak intervals and the amplitude of peaks were considered as the inter-breath interval (IBI) and lung volume (LV) series. The Detrended Fluctuation Analysis (DFA), Sample Entropy (SampEn), Multi-scale Entropy (MSE), short-term (SD1) and long-term (SD2) variability, and IBI and LV Cross-Sample Entropy of the respiratory pattern dynamics were calculated using MATLAB (Mathwork, USA).

RESULTS

Asthma patients showed notable increase in the average of sample entropy in both IBI and LV parameters (p = 0.025 and p = 0.018, respectively) and also decreased synchronization between IBI and LV (p = 0.042). The multi-scale sample entropy of both IBI and LV was significantly higher in asthmatic patients (p < 0.05). Furthermore, SD1 and SD2 were higher in the patients with asthma (p < 0.05). Significant correlations were detected between spirometric (forced expiratory flow (FEF) change, pre FEF, pre forced expiratory volume in one second (FEV1) / forced vital capacity (FVC), FVC change) and respiratory pattern (mean-IBI, mean-LV, mean-respiratory rate (RR), coefficient of variation (CV)-IBI, CV-LV, cross-sample entropy) parameters (p < 0.05). Furthermore, we identified a negative correlation between CV of IBI and asthma severity (r = -0.52, p = 0.021).

CONCLUSION

Here, we took a novel approach and observed increased irregularity (more complexity) in the breathing pattern of patients newly-diagnosed with asthma. Remarkable correlations were detected between breathing complexity markers and spirometric indices along with disease severity in asthmatic patients. Thus, our data suggests respiratory pattern indices could be utilized as an indicator of asthma and its severity. However, more clinical data are required to support this conclusion.

Assessment of lung ultrasound for early detection of respiratory complications in thoracic surgery

BACKGROUND AND OBJECTIVES

To assess lung ultrasound for the diagnosis and monitoring of respiratory complications in thoracic surgery.

METHODS

Prospective observational study in a University hospital, single institution. Adult patients scheduled for pulmonary resection surgery excluding pneumonectomy. An ultrasound follow-up was performed from the day before the surgery to the third day after surgery with calculation of B-line and lung score (reaeration and loss of aeration scores). Respiratory complications were collected throughout the hospitalization period.

RESULTS

Fifty-six patients were included. Eighteen patients presented a respiratory complication (32%), and they presented significantly higher BMI and ASA scores. Patients operated by videothoracoscopy were less at risk of complications. At day 3, a reaeration score ≤ 2 on the ventilated side or ≤ -2 on the operated side, and a B-line score>6 on the operated side were in favor of a complication.

CONCLUSION

Lung ultrasound can help in the diagnosis of respiratory complications following pulmonary resection surgery.

Neostigmine Versus Sugammadex for Reversal of Neuromuscular Blockade and Effects on Reintubation for Respiratory Failure or Newly Initiated Noninvasive Ventilation: An Interrupted Time Series Design

BACKGROUND

Pulmonary complications related to residual neuromuscular blockade lead to morbidity and mortality. Using an interrupted time series design, we tested whether proportions of reintubation for respiratory failure or new noninvasive ventilation were changed after a system-wide transition of the standard reversal agent from neostigmine to sugammadex.

METHODS

Adult patients undergoing a procedure with general anesthesia that included pharmacologic reversal of neuromuscular blockade and admission ≥1 night were eligible. Groups were determined by date of surgery: August 15, 2015 to May 10, 2016 (presugammadex), and August 15, 2016 to May 11, 2017 (postsugammadex). The period from May 11, 2016 to August 14, 2016 marked the institutional transition (washout/wash-in) from neostigmine to sugammadex. The primary outcome was defined as a composite of reintubation for respiratory failure or new noninvasive ventilation. Event proportions were parsed into 10-day intervals in each cohort, and trend lines were fitted. Segmented logistic regression models appropriate for an interrupted time series design and adjusting for potential confounders were utilized to evaluate the immediate effect of the implementation of sugammadex and on the difference between preintervention and postintervention slopes of the outcomes. Models containing all parameters (full) and only significant parameters (parsimonious) were fitted and are reported.

RESULTS

Of 13,031 screened patients, 7316 patients were included. The composite respiratory outcome occurred in 6.1% of the presugammadex group and 4.2% of the postsugammadex group. Adjusted odds ratio (OR) and 95% confidence intervals (CIs) for the composite respiratory outcome were 0.795 (95% CI, 0.523-1.208) for the immediate effect of intervention, 0.986 (95% CI, 0.959-1.013) for the difference between preintervention and postintervention slopes in the full model, and 0.667 (95% CI, 0.536-0.830) for the immediate effect of the intervention in the parsimonious model.

CONCLUSIONS

The system-wide transition of the standard pharmacologic reversal agent from neostigmine to sugammadex was associated with a reduction in the odds of the composite respiratory outcome. This observation is supported by nonsignificant within-group time trends and a significant reduction in intercept/level from presugammadex to postsugammadex in a parsimonious logistic regression model adjusting for covariates.

Transcatheter Aortic Valve Implantation Versus Surgical Aortic Valve Replacement in Lower-Surgical-Risk Patients With Chronic Obstructive Pulmonary Disease

Respiratory complications are a major factor contributing to postoperative morbidity and mortality, especially in patients with chronic obstructive pulmonary disease (COPD). Our objective was to compare the rate of respiratory complications in patients with COPD with severe aortic stenosis who underwent transcatheter aortic valve implantation (TAVI) versus surgical aortic valve replacement (SAVR). Low-to-intermediate surgical-risk patients with moderate or severe COPD who underwent TAVI or SAVR at 2 tertiary centers were included in this study. COPD was defined by the Global Initiative for Chronic Lung Disease classification. The primary end point was the 30-day composite of respiratory mortality, prolonged ventilation (>24 hours), the need for reintubation for respiratory causes, tracheostomy, acute respiratory distress syndrome, pneumonia, or pneumothorax. The inverse probability of treatment weighting was determined to reduce baseline imbalance between the 2 groups. A total of 321 patients (mean age 72.4 ± 9.3 years old, 74.5% male, mean Society of Thoracic Surgeons predicted risk of mortality 3.8 ± 1.9%, mean forced expiratory volume 1: 59 ± 13%) were included in the analysis. TAVI was performed in 122 patients, whereas 199 underwent SAVR. There were no differences between the 2 groups regarding the composite respiratory primary end point (SAVR 10.6%, TAVR 7.4%, adjusted odds ratio 0.57, 95% confidence interval 0.20 to 1.65, p = 0.30). Transfemoral TAVI without general anesthesia (28 patients) was associated with the lowest rate of respiratory complications (3.6%). Among patients with moderate or severe COPD at low-to-intermediate surgical risk, TAVI patients had a similar rate of 30-day major pulmonary complications compared with SAVR patients despite a higher baseline risk profile. Future studies should further investigate whether TAVI is associated with reduced respiratory complications, comparing transfemoral TAVI recipients treated with local anesthesia with their SAVR counterparts.

Discrepancy between in vivo and in vitro comparisons of forced oscillation devices

The forced oscillation technique (FOT) is an emerging clinical lung function test, with commercial devices becoming increasingly available. However comparability across existing devices has not been established. We evaluated in vivo and in vitro measurements made using three commercial devices against a custom-built device (WIMR): Resmon Pro Diary (Restech srl, Italy), tremoFlo C-100 (Thorasys Medical Systems, Canada), Jaeger Masterscope CT IOS (CareFusion, Hoechberg, Germany). Respiratory system resistance Rrs and reactance Xrs at 5 Hz were examined in twelve healthy subjects (mean age 33 ± 11 years, 7 males), and in two test standards of known resistance and reactance. Subjects performed three measurements during tidal breathing on the four devices in random order. Total, inspiratory and expiratory Rrs and Xrs were calculated and compared using one-way repeated measures ANOVA and Bonferroni post-hoc tests. Rrs did not differ between devices, with <10% deviation from predicted, except for the IOS device. With Xrs, similar values were seen between the WIMR and Resmon devices and between the tremoFlo and IOS devices. No differences were observed using test standards; deviation from theoretical value was <2% for resistance and <5% for reactance. The WIMR, tremoFlo and Resmon Pro but not IOS devices measure similar Rrs, whereas there was more disparity across devices in the estimation of Xrs parameters. The discrepancy between in vivo and in vitro measurements suggest that FOT validation procedures need to take into account the breathing pattern, either using biological controls or a breathing model.

Pulmonary Protection Strategies in Cardiac Surgery: Are We Making Any Progress?

Pulmonary dysfunction is a common complication of cardiac surgery. The mechanisms involved in the development of pulmonary dysfunction are multifactorial and can be related to the activation of inflammatory and oxidative stress pathways. Clinical manifestation varies from mild atelectasis to severe respiratory failure. Managing pulmonary dysfunction postcardiac surgery is a multistep process that starts before surgery and continues during both the operative and postoperative phases. Different pulmonary protection strategies have evolved over the years; however, the wide acceptance and clinical application of such techniques remain hindered by the poor level of evidence or the sample size of the studies. A better understanding of available modalities and/or combinations can result in the development of customised strategies for the different cohorts of patients with the potential to hence maximise patients and institutes benefits.