INSPIRATORY MUSCLES TRAINING: AN EFFECTIVE WAY TO IMPROVE POST-OPERATIVE OUTCOMES AFTER CORONARY ARTERY BYPASS GRAFTING

Cardiovascular diseases (CVD) are the leading cause of death worldwide. It is a multifactorial disease and has many risk factors including hypertension, diabetes mellitus, physical inactivity and smoking. Coronary artery disease (CAD) is one of the consequences of CVD.1 If we talk about CAD, it is a really common heart disease in our country, also known as ischemic heart disease and develops when coronary arteries or its sub-branches which are the blood supply of the heart become narrowed or blocked due to accumulation of plaque leading to an impaired supply of oxygen rich blood to the heart and thus cause retrosternal chest pain typically known as angina that is accompanied by dyspnea.2 Coronary artery bypass grafting (CABG) is generally the ideal treatment option for the individuals suffering from CAD. In this procedure, an auto-graft of vessel is taken and the commonly used vessels are left internal thoracic artery and great saphenous vein. The graft is sutured in such a way that the blocked coronary artery is bypassed and the blood supply to the heart is restored.3 Although medical sciences have advanced a lot, yet the prevalence of post-operative complications, specifically the respiratory ones pose an immediate threat to the survival and are the aiding factors to mortality and morbidity.4 Physical therapy after any surgery plays a pivotal role in improving the post-operative outcomes and helps the patient fight the effects of surgery. It makes a patient return to his or her normal life and helps in the early discharge of patients from hospitals thus preventing the chances of hospital acquired infections and reducing the financial load on masses.5 Respiratory rehabilitation, which is the specialty of physical therapy, have tremendous positive effects on the pulmonary compliance and function by preventing the post-operative pulmonary atelectasis.6 Moving further towards the components of respiratory rehabilitation, a group of breathing maneuvers conjointly known as inspiratory muscles training (IMT), if applied pre-operatively to the patients who are scheduled to undergo the coronary artery by-pass grafting displayed healthy post-operative outcomes.7 To conclude, it is the dire need of today to raise awareness among the health care professionals especially cardiologists and cardio-thoracic surgeons; and the general public regarding the pre-operative respiratory physical therapy for the patients planned to go through CABG. So, in the light of supported evidence, it is proved that respiratory physical therapy, particularly pre-operative IMT has positive outcomes in post-operative state. Moreover, the authors would also like to shed light on the facts about the healthcare policies and physical therapy services in Pakistan. Contrary to public sector hospitals, the rehabilitation departments in private sector hospitals are properly managed, substantially equipped and well established, leading to enhanced quality of physical therapy practices that result in better prognosis of the patients. The health department of our country should also emphasize on the public sector hospitals to make necessary arrangements for logistics of sufficient equipment and the hiring of physical therapists that are qualified and specialized in the field of cardiopulmonary physical therapy.

Flow Index accurately identifies breaths with low or high inspiratory effort during pressure support ventilation

Background Flow Index, a numerical expression of the shape of the inspiratory flow-time waveform recorded during pressure support ventilation, is associated with patient inspiratory effort. The aim of this study was to assess the accuracy of Flow Index in detecting high or low inspiratory effort during pressure support ventilation and to establish cutoff values for the Flow index to identify these conditions. The secondary aim was to compare the performance of Flow index,of breathing pattern parameters and of airway occlusion pressure (P0.1) in detecting high or low inspiratory effort during pressure support ventilation. Methods Data from 24 subjects was included in the analysis, accounting for a total of 702 breaths. Breaths with high inspiratory effort were defined by a pressure developed by inspiratory muscles (Pmusc) greater than 10 cmH2O while breaths with low inspiratory effort were defined by a Pmusc lower than 5 cmH2O. The areas under the receiver operating characteristic curves of Flow Index and respiratory rate, tidal volume,respiratory rate over tidal volume and P0.1 were analyzed and compared to identify breaths with low or high inspiratory effort. Results Pmusc, P0.1, Pressure Time Product and Flow Index differed between breaths with high, low and intermediate inspiratory effort, while RR, RR/VT and VT/kg of IBW did not differ in a statistically significant way. A Flow index higher than 4.5 identified breaths with high inspiratory effort [AUC 0.89 (CI 95% 0.85–0.93)], a Flow Index lower than 2.6 identified breaths with low inspiratory effort [AUC 0.80 (CI 95% 0.76–0.83)]. Conclusions Flow Index is accurate in detecting high and low spontaneous inspiratory effort during pressure support ventilation.

Proportional assist ventilation relieves clinically significant dyspnea in critically ill ventilated patients

Introduction Dyspnea is common and often severe symptom in mechanically ventilated patients. Proportional assist ventilation (PAV) is an assist ventilatory mode that adjusts the level of assistance to the activity of respiratory muscles. We hypothesized that PAV reduce dyspnea compared to pressure support ventilation (PSV). Patients and methods Mechanically ventilated patients with clinically significant dyspnea were included. Dyspnea intensity was assessed by the Dyspnea—Visual Analog Scale (D-VAS) and the Intensive Care-Respiratory Distress Observation Scale (IC-RDOS) at inclusion (PSV-Baseline), after personalization of ventilator settings in order to minimize dyspnea (PSV-Personalization), and after switch to PAV. Respiratory drive was assessed by record of electromyographic activity of inspiratory muscles, the proportion of asynchrony was analyzed. Results Thirty-four patients were included (73% males, median age of 66 [57–77] years). The D-VAS score was lower with PSV-Personalization (37 mm [20‒55]) and PAV (31 mm [14‒45]) than with PSV-Baseline (62 mm [28‒76]) (p < 0.05). The IC-RDOS score was lower with PAV (4.2 [2.4‒4.7]) and PSV-Personalization (4.4 [2.4‒4.9]) than with PSV-Baseline (4.8 [4.1‒6.5]) (p < 0.05). The electromyographic activity of parasternal intercostal muscles was lower with PAV and PSV-Personalization than with PSV-Baseline. The asynchrony index was lower with PAV (0% [0‒0.55]) than with PSV-Baseline and PSV-Personalization (0.68% [0‒2.28] and 0.60% [0.31‒1.41], respectively) (p < 0.05). Conclusion In mechanically ventilated patients exhibiting clinically significant dyspnea with PSV, personalization of PSV settings and PAV results in not different decreased dyspnea and activity of muscles to a similar degree, even though PAV was able to reduce asynchrony more effectively.

Evaluation of the Pulmonary Function Test (PFT) in Patients Affected by Severe COVID-19 Pneumonia: 6 to 12 Weeks After Discharge

The most lethal adverse effect of COVID-19 is acute respiratory distress syndrome, which can lead to rapid death. This symptom even causes concern for patients who have recovered and have been discharged. Therefore, it is obligatory to test and monitor variations in their lungs’ function after recovery. In this study, we evaluated the pulmonary function of 64 patients with severe COVID-19, six weeks to 3 months after discharge. Pulmonary function parameters were measured by spirometry and body box according to the criteria of the American Thoracic Society and under the supervision of an adult pulmonologist. According to the forced expiratory volume (FEV1)/forced vital capacity (FVC) ratio and total lung capacity (TLC) values, it was found that 3.1% of people had an obstructive pattern, 40.63% of patients had the restrictive pattern, and 6.25% of improved individuals showed a mixed pattern. Furthermore, the study of diffusion capacity of carbon monoxide (DLCO) index revealed that 13.3%, 25%, and 53% of cases had mild, moderate, and severe disorders of gas exchange, respectively. In addition, determining the maximum amount of inspiratory muscles (PI max) and expiratory muscles (PE max) disclosed that the rate of these two indicators in 62.5% and 71.88% of the subjects were less than 50%, respectively. In general, the results of the present study suggest that pulmonary function test and follow-up of patients' condition are not only recommended but seems to be essential after recovery due to the large percentage of patients with the restricted pattern a few weeks after recovery.

The Type of Conservative Management Could Be Related to the Strength of the Inspiratory Muscles of Adolescents with Idiopathic Scoliosis—A Case Series

Adolescent idiopathic scoliosis (AIS) is a lateral curvature of the spine with a Cobb angle of at least 10° with an unknown etiology. It is recognized that AIS may affect respiratory function. This study aims to describe and compare respiratory function in a case series of patients with scoliosis who underwent different types of therapeutic management: no intervention, orthotic brace, and global postural reeducation (GPR). Fifteen AIS patients were included in this study (seven no intervention, four orthotic brace and four GPR). Lung function and inspiratory muscle strength were measured and analyzed, as well as sociodemographic, clinical, and anthropometric variables. Significant correlations were observed between height (cm) and maximum inspiratory pressure (MIP) reference (cmH2O) and forced vital capacity (FVC) (liters) (r = 0.650 and r = 0.673, respectively; p < 0.01); weight (Kg) and MIP reference (cmH2O) (r = 0.727; p < 0.01); and Main curve degrees (Cobb angle) and FVC% (r = −0.648; p < 0.01). The AIS cases that underwent GPR treatment presented a greater MIP (% predictive) compared to the no intervention and brace cases (201.1% versus 126.1% and 78.4%, respectively; p < 0.05). The results of this case series show a possible relation whereby patients undergoing treatment with the GPR method have greater inspiratory muscle strength compared to the no intervention and brace cases. Studies with larger samples and prospective designs must be performed to corroborate these results.

Optimizing phase variability threshold for automated synchrogram analysis of cardiorespiratory interactions in amateur cyclists

We propose a procedure suitable for automated synchrogram analysis for setting the threshold below which phase variability between two marker event series is of such a negligible amount that the null hypothesis of phase desynchronization can be rejected. The procedure exploits the principle of maximizing the likelihood of detecting phase synchronization epochs and it is grounded on a surrogate data approach testing the null hypothesis of phase uncoupling. The approach was applied to assess cardiorespiratory phase interactions between heartbeat and inspiratory onset in amateur cyclists before and after 11-week inspiratory muscle training (IMT) at different intensities and compared to a more traditional approach to set phase variability threshold. The proposed procedure was able to detect the decrease in cardiorespiratory phase locking strength during vagal withdrawal induced by the modification of posture from supine to standing. IMT had very limited effects on cardiorespiratory phase synchronization strength and this result held regardless of the training intensity. In amateur athletes training, the inspiratory muscles did not limit the decrease in cardiorespiratory phase synchronization observed in the upright position as a likely consequence of the modest impact of this respiratory exercise, regardless of its intensity, on cardiac vagal control. This article is part of the theme issue 'Advanced computation in cardiovascular physiology: new challenges and opportunities'.

The Role of Diaphragmatic Rapid Shallow Breathing Index and Maximum Inspiratory Pressure in Predicting Outcome of Weaning From Mechanical Ventilation

Background Mechanical ventilation is the defining event of intensive care unit (ICU) management. It is a lifesaving intervention in patients with acute respiratory failure and whose spontaneous ventilation is inadequate for subsequent development of life threatening hypoxia and/or respiratory acidosis. Many physicians simply look at the patient’s ability to tolerate a spontaneous breathing trial (SBT) without distress through the respiratory rate (RR) and TV during the SBT. The RR/TV ratio, i.e., the rapid shallow breathing index (RSBI), one of the most used clinical indices to predict weaning outcome, reflects the balance between mechanical load posed on the inspiratory muscles and the inspiratory muscles ability to face it during the weaning attempt. However, RSBI was found to have both variable sensitivity and specificity for predicting weaning outcome. Although the diaphragm plays a fundamental role in generating TV in healthy subjects, if the diaphragmatic efficiency is impaired the accessory inspiratory muscles mild contribute to the ventilation for a limited period of time, for example during a SBT. However, since they are by far less efficient and more fatigable than the diaphragm, their exhaustion was likely lead to weaning failure in subsequent hours. Hence, the contribution of the accessory muscles to TV could compromise the diagnostic accuracy of the RSBI by masking the underlying diaphragmatic dysfunction. Aim of the Work To assess the accuracy of Diaphragmatic Rapid shallow breathing index and Maximum inspiratory pressure in predicting the outcome of weaning from mechanical ventilation. Patients and Methods The study was conducted at Ain Shams University Hospitals over 6 months on Patients who were mechanically ventilated for more than 48 hrs who were ready for weaning. Inclusion Criteria Patients intubated & mechanically ventilated for more than 48 hrs. Patients at their first SBT.Patients with adequate cough reflex. Patients fulfilling criteria of readiness for weaning from mechanical ventilation after resolution of cause of respiratory failure: Patients with score ranging between -1 and +1 on the Richmond Agitation and sedation scale (RASS). Exclusion criteria Age &lt; 18 yrs. Patients with thoracotomy, pneumothorax, or pneumomediastinum. Patients with presence of flail chest or rib fractures. Patients with neuromuscular disease. Use of muscle-paralyzing agents within 48 hours before the study. History or new detection of paralysis or paradoxical movement of a single hemi diaphragm on diaphragmatic ultrasonography. Pregnant females. Unconscious noncooperative patients. Patients with intra-abdominal hypertension, Long term steroid therapy. Results I- Distribution of the studied patients regarding final outcome. II- Demographic data. III. Causes of MV. IV- Days on MV. V- Patients’ data and characteristics before start of weaning trial. VI- SBT Ventilator Breathing pattern after 30 min. VII- Study predictors. Conclusion D-RSBI is a new and promising tool that is superior to the traditional RSBI in predicting weaning outcome also MIP provides appreciated data with greater accuracy to assess inspiratory muscle strength and predicting weaning success in mechanically ventilated patients. Recommendations We could recommend the measurement of MIP and DRSBI as weaning predictors should be an integral part of evaluation of patients plan for weaning from MV. All intensivists should be acquitted with the use of U/S in the evaluation of diaphragmatic function.

Thoracic weighting of restrained subjects during exhaustion recovery causes loss of lung reserve volume in a model of police arrest

Restraint asphyxia has been proposed as a mechanism for some arrest-related deaths that occur during or shortly after a suspect is taken into custody. Our analysis of the literature found that prone positioning, weight applied to the back, recovery after simulated pursuit, and restraint position have led to restrictive, but non life-threatening respiratory changes when tested in subsets. However, the combined effects of all four parameters have not been tested together in a single study. We hypothesized that a complete protocol with high-sensitivity instrumentation could improve our understanding of breathing physiology during weighted restraint. We designed an electrical impedance tomography (EIT)-based protocol for this purpose and measured the 3D distribution of ventilation within the thorax. Here, we present the results from a study on 17 human subjects that revealed FRC declines during weighted restrained recovery from exercise for subjects in the restraint postures, but not the control posture. These prolonged FRC declines were consistent with abdominal muscle recruitment to assist the inspiratory muscles, suggesting that subjects in restraint postures have increased work of breathing compared to controls. Upon removal of the weighted load, lung reserve volumes gradually increased for the hands-behind-the-head restraint posture but continued to decrease for subjects in the hands-behind-the-back restraint posture. We discuss the possible role this increased work of breathing may play in restraint asphyxia.

Effects of diaphragmatic control on multiparametric analysis of the sniff nasal inspiratory pressure test and inspiratory muscle activity in healthy subjects

Background We investigated the influence of diaphragmatic activation control (diaphC) on the relaxation rate, contractile properties and electrical activity of the inspiratory muscles of healthy subjects. Assessments were performed non-invasively using the sniff inspiratory pressure test (SNIP) and surface electromyography, respectively. Methods Twenty-two subjects (10 men and 12 women) performed 10 sniff maneuvers in two different days: with and without diaphC instructions. For the SNIP test with diaphC, the subjects were instructed to perform intense activation of the diaphragm. The tests with the best SNIP values were used for analysis. Results The maneuver with diaphC when compared to the maneuver without diaphC exhibited significant lower values for: SNIP (p <0.01), maximum relaxation rate (MRR) (p <0.01), maximum rate of pressure development (MRPD) (p <0.01), contraction times (CT) (p = 0.02) and electrical activity of the sternocleidomastoid (SCM) (p <0.01), scalene (SCL) (p = 0.01) and intercostal (CI) (p = 0.03) muscles. In addition, the decay constant (tau, τ) and relaxation time (½ RT) did not present any changes. Conclusion The diaphragmatic control performed during the SNIP test influences the inspiratory pressure and the contractile properties of inspiratory muscles. This occurs due to changes in the pattern of muscle recruitment, which change force velocity characteristics of the test. Thus, instruction on diaphC should be encouraged for better performance of the SNIP test and for evaluation targeting the diaphragm muscle activity.