Lower Minute Ventilation Research Articles

Exploring immediate cardiorespiratory responses: low-intensity blood flow restricted cycling vs. moderate-intensity traditional exercise in a randomized crossover trial

PurposeBlood-flow restriction (BFR) endurance training may increase endurance performance and muscle strength similar to traditional endurance training while requiring a lower training intensity. We aimed to compare acute cardiorespiratory responses to low-intensity interval exercise under BFR with moderate-intensity traditional interval exercise (TRA).MethodsWe conducted a randomized crossover study. The protocol involved three cycling intervals interspersed with 1 min resting periods. With a 48-h washout period, individuals performed the protocol twice in random order: once as BFR-50 (i.e., 50% incremental peak power output [IPPO] and 50% limb occlusion pressure [LOP]) and once as TRA-65 (65% IPPO without occlusion). TRA-65 intervals lasted 2 min, and time-matched BFR-50 lasted 2 min and 18 s. Respiratory parameters were collected by breath-by-breath analysis. The ratings of perceived breathing and leg exertion (RPE, 0 to 10) were assessed. Linear mixed models were used for analysis.ResultsOut of the 28 participants initially enrolled in the study, 24 healthy individuals (18 males and 6 females) completed both measurements. Compared with TRA-65, BFR-50 elicited lower minute ventilation (VE, primary outcome) (-3.1 l/min [-4.4 to -1.7]), oxygen consumption (-0.22 l/min [-0.28 to -0.16]), carbon dioxide production (-0.25 l/min [-0.29 to -0.20]) and RPE breathing (-0.9 [-1.2 to -0.6]). RPE leg was significantly greater in the BFR-50 group (1.3 [1.0 to 1.7]).ConclusionBFR endurance exercise at 50% IPPO and 50% LOP resulted in lower cardiorespiratory work and perceived breathing effort compared to TRA at 65% IPPO. BFR-50 could be an attractive alternative for TRA-65, eliciting less respiratory work and perceived breathing effort while augmenting perceived leg muscle effort.Trial registrationNCT05163600; December 20, 2021.

Expiratory braking defines the breathing patterns of asphyxiated neonates during therapeutic hypothermia.

Although neonatal breathing patterns vary after perinatal asphyxia, whether they change during therapeutic hypothermia (TH) remains unclear. We characterized breathing patterns in infants during TH for hypoxic-ischemic encephalopathy (HIE) and normothermia after rewarming. In seventeen spontaneously breathing infants receiving TH for HIE and in three who did not receive TH, we analyzed respiratory flow and esophageal pressure tracings for respiratory timing variables, pulmonary mechanics and respiratory effort. Breaths were classified as braked (inspiratory:expiratory ratio ≥1.5) and unbraked (<1.5). According to the expiratory flow shape braked breaths were chategorized into early peak expiratory flow, late peak expiratory flow, slow flow, and post-inspiratory hold flow (PiHF). The most braked breaths had lower rates, larger tidal volume but lower minute ventilation, inspiratory airway resistance and respiratory effort, except for the PiHF, which had higher resistance and respiratory effort. The braked pattern predominated during TH, but not during normothermia or in the uncooled infants. We speculate that during TH for HIE low respiratory rates favor neonatal braked breathing to preserve lung volume. Given the generally low respiratory effort, it seems reasonable to leave spontaneous breathing unassisted. However, if the PiHF pattern predominates, ventilatory support may be required.

Postoperative esketamine improves ventilation after video-assisted thoracoscopic lung resection: A double-blinded randomized controlled trial

BackgroundPain management after lung resection plays a crucial role in reducing postoperative pulmonary complications (PPCs). This study aimed to examine the effect of postoperative esketamine infusion as an adjunct to opioid analgesia on ventilation and pulmonary complications in patients underwent lung resection. MethodsPatients undergoing video-assisted thoracoscopic lung resection were randomly assigned to either the esketamine group or the control group. The esketamine group received a 24-h infusion of 1.5 mcg/ml sufentanil combined with 0.75 mcg/ml esketamine after surgery, while the control group received 1.5 mcg/ml sufentanil alone. The primary outcome measure was low minute ventilation, and the secondary outcome measures were hypoxemia, PaO2/FiO2 levels, postoperative pulmonary complications, hospital stay duration, ambulation time, Visual Analogue Scale (VAS) score, depression and anxiety levels, sleep quality, and analgesia satisfaction. Results80 patients were randomly divided into two groups: the esketamine group (n = 40) and the control group (n = 40). The esketamine group exhibited notably reduced incidence of low minute ventilation (P = 0.014), lower occurrence of postoperative pulmonary complications (PPCs) compared to the control group (P = 0.039), and decreased incidence of hypoxemia (P = 0.003). Furthermore, the esketamine group showed improved outcomes with lower VAS scores on the second postoperative day and enhanced sleep quality (P < 0.001) after the surgery. ConclusionsPostoperative esketamine infusion with opioids improved ventilation and reduced PPCs after lung resection, warranting further clinical studies. Trial registrationThis study was registered on ClinicalTrials.gov (Trial ID: NCT05458453, https://clinicaltrials.gov/ct2/show/NCT05458453).

Lung tissue injury and hemodynamic effects of ventilations synchronized or unsynchronized to continuous chest compressions in a porcine cardiac arrest model

AimCompare lung injury and hemodynamic effects in synchronized ventilations (between two chest compressions) vs. unsynchronized ventilations during cardiopulmonary resuscitation (CPR) in a porcine model of cardiac arrest. MethodsTwenty pigs were randomized to either synchronized or unsynchronized group. Ventricular fibrillation was induced electrically and left for 1.5 minutes. Four minutes of basic chest compression:ventilation (30:2) CPR was followed by eight minutes of either synchronized or unsynchronized ventilations (10/min) during continuous compressions before defibrillation was attempted. Aortic, right atrial and intracerebral pressures, carotid and cerebral blood flow and cardiac output were measured. Airway monitoring included capnography and respiratory function monitor. Macro- and microscopic lung injuries were assessed post-mortem. ResultsThere were no significant differences between groups in any of the measured hemodynamic variables or inspiration time (0.4 vs. 1.0 s, p = 0.05). The synchronized ventilation group had lower median peak inspiratory airway pressure (57 vs. 94 cm H2O, p < 0.001), lower minute ventilation (3.7 vs. 9.4 l min−1, p < 0.001), lower pH (7.31 vs. 7.53, p < 0.001), higher pCO2 (5.2 vs. 2.5 kPa, p < 0.001) and lower pO2 (31.6 vs. 54.7 kPa, p < 0.001) compared to the unsynchronized group after 12 minutes of CPR. There was significant lung injury after CPR in both synchronized and unsynchronized groups. ConclusionSynchronized and unsynchronized ventilations resulted in similar hemodynamics and lung injury during continuous mechanical compressions of pigs in cardiac arrest. Animals that received unsynchronized ventilations with one second inspiration time at a rate of ten ventilations per minute were hyperventilated and hyperoxygenated.Institutional protocol number: FOTS, id 6948.

Breathing irregularities in spontaneously hypertensive neonate rats

An excessive sympathetic drive is commonly observed in hypertensive patients and critically contributes to increasing arterial pressure levels. The quality of postnatal life can impact sympathetic control in adulthood. Spontaneously hypertensive (SH) rats, an experimental model of neurogenic hypertension, exhibit breathing irregularities in adult life. In this study, we investigated whether SH rats display breathing abnormalities after birth, which could be a risk factor for developing sympathetic overactivity. Using head-out plethysmography, we found that the neonate (P0-2, male and female) SH rats (n=9) exhibited lower minute ventilation than age-matched normotensive rats (NT, n=14; 816±177 vs 1261±189 ml/min/kg, P&lt;0.05) under resting conditions, mainly due to reductions in respiratory frequency (93±15 vs 132±13 cpm, P&lt;0.05). The reduced baseline ventilation in the SH group was accompanied by a greater prevalence of periods of apneas and respiratory irregularities (P&lt;0.05). Under hypoxia conditions (10% O2, 10 min), SH and NT rats (n=9/each) mounted similar transient increases in minute ventilation during the initial period of exposure due to increments in tidal volume. In contrast, the respiratory frequency in the SH rats decreased progressively below baseline levels during hypoxia exposure (42% reduction, P&lt;0.05), while it remained similar to pre-hypoxia values in the control group. In rhythmic in vitro preparations from neonate SH rats (n=2), we identified ectopic bursts in the hypoglossal activity and prolonged inspiratory-related bursts in the preBötzinger complex compared to preparations from NT rats (n=2). Our findings indicate that breathing irregularities in SH rats are present from birth and could be linked to dysfunctions in the inspiratory rhythm-generating network. Financial support: FAPESP, CNPq. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Prediction of survival time after terminal extubation: the balance between critical care unit utilization and hospice medicine in the COVID-19 pandemic era

BackgroundWe established 1-h and 1-day survival models after terminal extubation to optimize ventilator use and achieve a balance between critical care for COVID-19 and hospice medicine.MethodsData were obtained from patients with end-of-life status at terminal extubation from 2015 to 2020. The associations between APACHE II scores and parameters with survival time were analyzed. Parameters with a p-value ≤ 0.2 in univariate analysis were included in multivariate models. Cox proportional hazards regression analysis was used for the multivariate analysis of survival time at 1 h and 1 day.ResultsOf the 140 enrolled patients, 76 (54.3%) died within 1 h and 35 (25%) survived beyond 24 h. No spontaneous breathing trial (SBT) within the past 24 h, minute ventilation (MV) ≥ 12 L/min, and APACHE II score ≥ 25 were associated with shorter survival in the 1 h regression model. Lower MV, SpO2 ≥ 96% and SBT were related to longer survival in the 1-day model. Hospice medications did not influence survival time.ConclusionAn APACHE II score of ≥ 25 at 1 h and SpO2 ≥ 96% at 1 day were strong predictors of disposition of patients to intensivists. These factors can help to objectively tailor pathways for post-extubation transition and rapidly allocate intensive care unit resources without sacrificing the quality of palliative care in the era of COVID-19.Trial registration They study was retrospectively registered. IRB No.: 202101929B0.

Hypoventilation in the PACU is associated with hypoventilation in the surgical ward: Post-hoc analysis of a randomized clinical trial

ObjectiveTo evaluate the association between early postoperative hypoventilation in the last hour of the post-anesthesia care unit (PACU) stay and hypoventilation during the rest of the first 48 postoperative hours in the surgical ward. DesignSub-analysis of a clinical trial. SettingPACU and surgical wards of a single medical center. PatientsAdults having abdominal surgery under general anesthesia. InterventionsMonitoring with a respiratory volume monitor from admission to PACU until the earlier of 48 h after surgery or discharge. MeasurementsThe exposure was having at least one low minute-ventilation (MV) event during the last hour of PACU stay, defined as MV lower than 40% the predicted value lasting at least 1 min. The primary outcome was low MV events lasting at least 2 min during the rest of the first 48 postoperative hours, while in the surgical ward. The secondary outcome was the rate of low MV events per monitored hour. Main resultsData of 292 patients were analyzed, of which 20 (6.8%) patients had a low MV event in PACU. Low MV events in the surgical ward were found in 81 (28%) patients. All patients who had low MV events in PACU had events again in the ward, while 61/272 (22%) had an event in the ward but not in PACU. The incidence rate of low MV events per hour was 24 (95% CI: 13, 46) among patients having an event in the PACU, and 2 (1, 4) among those who did not. ConclusionsIn adults recovering from abdominal surgery, events of hypoventilation during the first postoperative hour are associated with similar events during the rest of the first 48 postoperative hours, with positive predictive value approaching 100%. Sixty-one patients had ward hypoventilation that was not preceded by hypoventilation in PACU.

Exertional dyspnoea in patients with mild‐to‐severe chronic obstructive pulmonary disease: neuromechanical mechanisms

In patients with chronic obstructive pulmonary disease (COPD), exertional dyspnoea generally arises when there is imbalance between ventilatory demand and capacity, but the neurophysiological mechanisms are unclear. We therefore determined if disparity between elevated inspiratory neural drive (IND) and tidal volume (VT ) responses (neuromechanical dissociation) impacted dyspnoea intensity and quality during exercise, across the COPD severity spectrum. In this two-centre, cross-sectional observational study, 89 participants with COPD divided into tertiles of FEV1 %predicted (Tertile 1=FEV1 = 87±9%, Tertile 2=60±9%, Tertile 3=32±8%) and 18 non-smoking controls, completed a symptom-limited cardiopulmonary exercise test (CPET) with measurement of IND by diaphragm electromyography (EMGdi (%max)). The association between increasing dyspnoea intensity and EMGdi (%max) during CPET was strong (r=0.730, P<0.001) and not different between the four groups who showed marked heterogeneity in pulmonary gas exchange and mechanical abnormalities. Significant inspiratory constraints (tidal volume/inspiratory capacity (VT /IC)≥70%) and onset of neuromechanical dissociation (EMGdi (%max):VT /IC>0.75) occurred at progressively lower minute ventilation ( ) from Control to Tertile 3. Lower resting IC meant earlier onset of neuromechanical dissociation, heightened dyspnoea intensity and greater propensity (93% in Tertile 3) to select qualitative descriptors of 'unsatisfied inspiration'. We concluded that, regardless of marked variation in mechanical and pulmonary gas exchange abnormalities in our study sample, exertional dyspnoea intensity was linked to the magnitude of EMGdi (%max). Moreover, onset of critical inspiratory constraints and attendant neuromechanical dissociation amplified dyspnoea intensity at higher exercise intensities. Simple measurements of IC and breathing pattern during CPET provide useful insights into mechanisms of dyspnoea and exercise intolerance in individuals with COPD. KEY POINTS: Dyspnoea during exercise is a common and troublesome symptom reported by patients with chronic obstructive pulmonary disease (COPD) and is linked to an elevated inspiratory neural drive (IND). The precise mechanisms of elevated IND and dyspnoea across the continuum of airflow obstruction severity in COPD remains unclear. The present study sought to determine the mechanisms of elevated IND (by diaphragm EMG, EMGdi (%max)) and dyspnoea during cardiopulmonary exercise testing (CPET) across the continuum of COPD severity. There was a strong association between increasing dyspnoea intensity and EMGdi (%max) during CPET across the COPD continuum despite significant heterogeneity in underlying pulmonary gas exchange and respiratory mechanical impairments. Critical inspiratory constraints occurred at progressively lower ventilation during exercise with worsening severity of COPD. This was associated with the progressively lower resting inspiratory capacity with worsening disease severity. Earlier critical inspiratory constraint was associated with earlier neuromechanical dissociation and greater likelihood of reporting the sensation of 'unsatisfied inspiration'.

Effect of Six-Minute Walk Test and Incremental Exercise on Inspiratory Capacity, Ventilatory Constraints, Breathlessness and Exercise Performance in Sedentary Male Smokers without Airway Obstruction.

We investigated physiological responses and exercise capacity in sedentary young smokers during sub-maximal and maximal test and its impact on dyspnea and exercise intolerance. Fifty sedentary male smokers and non-smokers (age: 24 ± 1 years., weight: 71 ± 9 kg, height: 177.3 ± 4.8 cm, body mass index: 22.6 ± 2.5 kg/m2) underwent two visits with pulmonary function tests, breathing pattern, and inspiratory capacity measurement at rest and during sub-maximal and maximal exercise. Smokers show reduced exercise capacity during six minutes walk test (6-MWT) with decreased walked distance (p < 0.001) and inspiratory capacity (p < 0.05). During cardiopulmonary exercise test (CPET), smokers had higher minute ventilation VE for a given submaximal intensity (p < 0.05) and lower minute ventilation at maximal exercise (p < 0.001). End expiratory lung volume was significantly lower in sedentary smokers at rest (p < 0.05), at ventilatory threshold during exercise (p < 0.05), but not during peak exercise. End inspiratory lung volume was significantly lower in smokers at rest (p < 0.05) and ventilatory threshold (p < 0.05). Cigarette smoking alters lung function during submaximal and maximal exercise. This alteration is manifested by the development of dynamic hyperinflation contributing to exercise capacity limitation.

Knockdown of phosphoinositide-dependent kinase 1 (PDK1) inhibits fibrosis and inflammation in lipopolysaccharide-induced acute lung injury rat model by attenuating NF-κB/p65 pathway activation.

BackgroundAcute lung injury (ALI) is a common inflammatory disease of the lung. This study aimed to investigate the effect of 3-phosphoinositide-dependent kinase 1 (PDK1) interference on the levels of fibrosis and proinflammatory factors in lipopolysaccharide (LPS)-induced ALI and discuss the relevant mechanism.MethodsAn ALI model was established by intravenous injection of LPS treatment. A total of 24 Sprague-Dawley (SD) rats were randomly divided into 4 groups: sham group; ALI group; ALI + shRNA-NC group; and ALI + PDK1-shRNA group. Lung injury score, minute ventilation, lung volume, and airway resistance were used to evaluate lung function injury. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect PDK1 messenger RNA (mRNA) level. Western blot was performed to detect expression levels of PDK1, transforming growth factor-β (TGF-β), α-smooth muscle actin (α-SMA), toll-like receptor 4 (TLR4), p65, and myeloid differentiation primary response gene 88 (MyD88). The contents of interleukin-6 (IL-6), inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNF-α), and monocyte chemoattractant protein-1 (MCP-1) were detected by enzyme-linked immunosorbent assay (ELISA). The pathological changes and fibrosis of lung tissues were estimated by hematoxylin and eosin (H&E) and Masson staining.ResultsThe results revealed that high lung injury score, low minute ventilation, low lung volume, and small airway resistance were present in the ALI group. Likewise, severe histopathological damage and fibrosis were apparent in the ALI group. Otherwise, contents of TNF-α, iNOS, IL-6, MCP-1, and levels of α-SMA, TGF-β, TLR4, phosphorylated (p)-p65, and MyD88 were enhanced in the ALI group. Interestingly, pathological changes and fibrosis were improved significantly in the ALI + PDK1-shRNA group. Besides, knockdown of PDK1 reduced lung injury score and enhanced minute ventilation, lung volume, and airway resistance. Moreover, knockdown of PDK1 decreased the contents of TNF-α, iNOS, IL-6, MCP-1, and levels of TGF-β, α-SMA, TLR4, p-p65, and MyD88.ConclusionsKnockdown of PDK1 protects LPS-induced ALI via attenuating activation of the nuclear factor-κB (NF-κB)/p65 pathway.

Left ventricular diastolic dysfunction in non-severe chronic obstructive pulmonary disease as a step forward in cardiovascular comorbidome

Abstract Background Chronic obstructive pulmonary disease (COPD) augments the likelihood of having left ventricular diastolic dysfunction (LVDD) – precursor of heart failure with preserved ejection fraction (HFpEF). LVDD shares overlapping symptomatology (cough and dyspnea) with COPD. Purpose Our aim was to evaluate the predictive value of inflammatory, oxidative stress, cardio-pulmonary and echocardiographic parameters at rest for the diagnosis of stress LVDD in non-severe COPD patients, who complain of exertional dyspnea and are free of overt cardiovascular diseases. Methods A total of 104 COPD patients underwent echocardiography before cardio-pulmonary exercise testing (CPET) and 1–2 minutes after peak exercise. Patients were divided into two groups based on peak E/e': patients with stress induced left ventricular diastolic dysfunction (LVDD) - E/e' &amp;gt;15 (HFpEF) and patients LVDD (without HFpEF). CPET and echocardiographic parameters at rest were measured and their predictive value for stress E/e' was analysed. Markers for inflammation (resistin, prostaglandine E2) and oxidative stress (8-isoprostanes) were also determined. Results Stress induced LVDD occurred in 67/104 patients (64%). Those patients had lower work load, lower VO2 consumption, lower minute ventilation and higher VE/VCO2 slope in comparison to patients without. Except for prostglandine E2, none of the inflammatory, oxidative stress markers correlated to stress E/e'. The best independent predictors for HFpEF were RAVI, right ventricular parasternal diameter and RV E/A &amp;gt;0.75. Their combination predicted HFpEF with the accuracy of 91.2%. Conclusion There is a high prevalence of HFpEF in non-severe COPD with exertional dyspnea, free of overt cardiovascular disease. RAVI, right ventricular parasternal diameter and RV E/A &amp;gt;0.75 were the only independent clinical predictors of HFpEF. Funding Acknowledgement Type of funding sources: None.

Influence of grade of obesity on the achievement of VO2max using an incremental treadmill test in youths

ABSTRACT The purpose of this study was to analyze the influence of grade of obesity on the probability of achieving a VO2 plateau and threshold secondary criteria for verifying VO2max during a treadmill walk test in youths with obesity. Therefore, 72 youths with obesity (aged 8-16) performed an incremental treadmill walk test to exhaustion during which oxygen uptake (VO2), minute ventilation (VE), heart rate (HR) and rating of perceived exertion were continuously measured. HR corresponding to a “hard” level of perceived exertion was reported and expressed as a percentage of the predicted HRmax. The rate of achievement of criteria for validation VO2max (VO2 plateau; HR>95% theoretical HRmax; RER>1.0; rating of perceived exertion ≥ “hard”) was compared between participants with grade I and grade II obesity. 37% of the participants achieved a VO2 plateau and 23% achieved both an HR>95% and RER >1.0. Youths with grade II obesity had lower minute ventilation (p<0.01) tended to be more likely to reach an HR>95% (OR = 0.33; P=0.06) and a “hard” rating of perceived exertion than grade I (OR = 4.5; P=0.07). However, there was no influence of grade of obesity on the achievement of VO2 plateau, and RER>1.0.

COVID-19 versus Non-COVID-19 Acute Respiratory Distress Syndrome: Comparison of Demographics, Physiologic Parameters, Inflammatory Biomarkers, and Clinical Outcomes.

Rationale: There is an urgent need for improved understanding of the mechanisms and clinical characteristics of acute respiratory distress syndrome (ARDS) due to coronavirus disease (COVID-19). Objectives: To compare key demographic and physiologic parameters, biomarkers, and clinical outcomes of COVID-19 ARDS and ARDS secondary to direct lung injury from other etiologies of pneumonia. Methods: We enrolled 27 patients with COVID-19 ARDS in a prospective, observational cohort study and compared them with a historical, pre–COVID-19 cohort of patients with viral ARDS (n = 14), bacterial ARDS (n = 21), and ARDS due to culture-negative pneumonia (n = 30). We recorded clinical demographics; measured respiratory mechanical parameters; collected serial peripheral blood specimens for measurement of plasma interleukin (IL)-6, IL-8, and IL-10; and followed patients prospectively for patient-centered outcomes. We conducted between-group comparisons with nonparametric tests and analyzed time-to-event outcomes with Kaplan-Meier and Cox proportional hazards models. Results: Patients with COVID-19 ARDS had higher body mass index and were more likely to be Black, or residents of skilled nursing facilities, compared with those with non–COVID-19 ARDS (P < 0.05). Patients with COVID-19 had lower delivered minute ventilation compared with bacterial and culture-negative ARDS (post hoc P < 0.01) but not compared with viral ARDS. We found no differences in static compliance, hypoxemic indices, or carbon dioxide clearance between groups. Patients with COVID-19 had lower IL-6 levels compared with bacterial and culture-negative ARDS at early time points after intubation but no differences in IL-6 levels compared with viral ARDS. Patients with COVID-19 had longer duration of mechanical ventilation but similar 60-day mortality in both unadjusted and adjusted analyses. Conclusions: COVID-19 ARDS bears several similarities to viral ARDS but demonstrates lower minute ventilation and lower systemic levels of IL-6 compared with bacterial and culture-negative ARDS. COVID-19 ARDS was associated with longer dependence on mechanical ventilation compared with non–COVID-19 ARDS. Such detectable differences of COVID-19 do not merit deviation from evidence-based management of ARDS but suggest priorities for clinical research to better characterize and treat this new clinical entity.

Comparative evaluation of one-handed versus two-handed mask holding techniques in children during inhalational induction of anesthesia: A randomized crossover study.

We aimed to evaluate if two-handed mask airway is superior to one-handed mask airway during inhalational induction of anesthesia in children. A randomized, two period, crossover study was performed on 60 children aged 1-8years, with obstructive sleep apnea due to adenotonsillar hypertrophy, scheduled for adenotonsillectomy. Children were assigned to two study sequences and one control sequence of 20 subjects each. A control sequence was added to evaluate the effect of anesthetic depth. Sequence 1: One-handed followed by two-handed airway, 30seconds each; Sequence 2: two-handed followed by one-handed airway, 30seconds each and Sequence 3: two-handed airway, for 60seconds. The work of breathing indices, phase angle, and labored breathing index were recorded using respiratory inductance plethysmography. Additional outcome measures were tidal volume, minute ventilation, and respiratory rate. A straight comparison and a crossover analysis was performed. The initial comparison revealed that one-handed airway had greater phase angle (mean diff. 17.4; 95% confidence interval [CI] 1.07-33.68; P=.034), greater labored breathing index (mean diff. 0.56; 95% CI 0.16-1.04; P=.004),lower minute ventilation (mean diff. -1567; 95% CI -2695 to -5.4; P=.004),and lower tidal volume (mean diff. -39; 95% CI -2.7 to -5.4; P=.02) than two-handed airway. On crossover analysis, within-subject difference in the phase angle was greater during one-handed than two-handed airway (34.3; 95% CI 8.46-60.14; P=.01) as was labored breathing index (mean diff. 1.2; 95% CI 0.39-2.00; P<.0046).Minute ventilation was lower during one-handed than two-handed airway (mean diff. -3359; 95% CI -4363 to -2355, P<0.0001) as was tidal volume(mean diff. -78; 95% CI -110.4 to -45.8; P<.0001). In children with obstructive sleep apnea due to adenotonsillar hypertrophy, two-handed airway provides superior airway patency that was not influenced by the anesthetic depth.

Inspiratory Muscle Training Potentiates the Beneficial Effects of Proportional Assisted Ventilation on Exertional Dyspnea and Exercise Tolerance in COPD: A Proof-of-Concept Randomized and Controlled Trial

During pulmonary rehabilitation, a subset of subjects with COPD requires adjunct therapy to achieve high-intensity training. Both noninvasive ventilation (NIV) and inspiratory muscle training (IMT) are available to assist these subjects. We aimed to prime the respiratory muscles before NIV with IMT, anticipating additive effects for maximal exercise tolerance (T lim) and dyspnea/leg fatigue relief throughout the exercise as primary outcomes. Changes in the respiratory pattern were secondary outcomes. COPD subjects performed a total of four identical constant work rate tests on a cycle ergometer at 75% of maximum work rate, under control ventilation (SHAM, 4 cm H2O) or proportional assisted ventilation (PAV, individually adjusted), before and after 10 sessions of high-intensity IMT (three times/week) during 30 days. Two-way RM ANOVA with appropriate corrections were performed. Final analysis in nine subjects showed improved T lim (Δ = 111 s) and lower minute-ventilation (Δ = 4 L.min−1) at exhaustion, when comparing the IMT effects within the PAV modality (p = 0.001 and p = 0.036, respectively) and improved T lim for PAV vs. SHAM (PAV main-effect, p = 0.001; IMT main-effect, p = 0.006; PAV vs. IMT interaction, p = 0.034). In addition, IMT + PAV association, compared to PAV alone, resulted in lower respiratory frequency (IMT main-effect, p = 0.009; time main-effect, p < 0.0001; IMT vs. time interaction, p = 0.242) and lower inspiratory time related to duty cycle (IMT main-effect, p = 0.018; time main-effect, p = 0.0001; IMT vs. time interaction, p = 0.004) throughout exercise. The addition of IMT prior to a PAV-supported aerobic bout potentiates exercise tolerance and dyspnea relief and induces favourable changes in ventilatory pattern in severe COPD during high-intensity training (Brazilian Registry of Clinical Trials, number RBR-6n3dzz).

Effects of relative low minute ventilation on cerebral haemodynamics in infants undergoing ventricular septal defect repair.

Ventilation-associated changes in blood carbon dioxide levels are associated with various physiological changes in infants undergoing surgery. Studies on the effects of mechanical ventilation on cerebral haemodynamics especially for infants with CHD are scarce. This study was done to compare the changes in regional cerebral oxygen saturation and cerebral blood flow velocity when the end-tidal carbon dioxide partial pressure changed during different minute ventilation settings in infants undergoing ventricular septal defect repair. A total of 67 patients less than 1 year old with ventricular septal defect were enrolled, and 65 patients (age: 6.7 ± 3.4 months, weight: 6.4 ± 1.5 kg) were studied. After anaesthesia induction and endotracheal intubation, the same mechanical ventilation mode (The fraction of inspired oxygen was 50%, and the inspiratory-to-expiratory ratio was 1:1.5.) was adopted. The end-tidal carbon dioxide partial pressure of 30 mmHg (T1), 35 mmHg (T2), 40 mmHg (T3), or 45 mmHg (T4) were obtained, respectively, by adjusting tidal volume and respiratory rate. Minute ventilation per kilogram was calculated by the formula: minute ventilation per kilogram = tidal volume * respiratory rate/kg. Regional cerebral oxygen saturation was monitored by real-time near-infrared spectroscopy. Cerebral blood flow velocity (systolic flow velocity, end-diastolic flow velocity, and mean flow velocity), pulsatility index, and resistance index were measured intermittently by transcranial Doppler. Systolic pressure, diastolic pressure, stroke volume index, and cardiac index were recorded using the pressure recording analytical method. As the end-tidal carbon dioxide partial pressure increased from 30 to 45 mmHg, regional cerebral oxygen saturation increased significantly from 69 ± 5% to 79 ± 4% (p < 0.001). Cerebral blood flow velocity (systolic flow velocity, end-diastolic flow velocity, and mean flow velocity) increased linearly, while pulsatility index and resistance index decreased linearly from T1 (systolic flow velocity, 84 ± 19 cm/second; end-diastolic flow velocity, 14 ± 4 cm/second; mean flow velocity, 36 ± 10 cm/second; pulsatility index, 2.13 ± 0.59; resistance index, 0.84 ± 0.12) to T4 (systolic flow velocity, 113 ± 22 cm/second; end-diastolic flow velocity, 31 ± 6 cm/second; mean flow velocity, 58 ± 11 cm/second; pulsatility index, 1.44 ± 0.34; resistance index, 0.72 ± 0.07) (p < 0.001). There were significant differences in changes of systolic flow velocity, end-diastolic flow velocity, mean flow velocity, pulsatility index, and resistance index as the end-tidal carbon dioxide partial pressure increased from 30 to 45 mmHg between subgroups of infants ≤6 and infants >6 months, while the changes of regional cerebral oxygen saturation between subgroups were not statistically different. Regional cerebral oxygen saturation and cerebral blood flow velocity (systolic flow velocity, end-diastolic flow velocity, and mean flow velocity) were negatively correlated with minute ventilation per kilogram (r = -0.538, r = -0.379, r = -0.504, r = -0.505, p < 0.001). Pulsatility index and resistance index were positively related to minute ventilation per kilogram (r = 0.464, r = 0.439, p < 0.001). The diastolic pressure was significantly reduced from T1 (41 ± 7 mmHg) to T4 (37 ± 6 mmHg) (p < 0.001). There were no significant differences in systolic pressure, stroke volume index, and cardiac index with the change of end-tidal carbon dioxide partial pressure from T1 to T4 (p = 0.063, p = 0.382, p = 0.165, p > 0.05). A relative low minute ventilation strategy increases regional cerebral oxygen saturation and cerebral blood flow, which may improve cerebral oxygenation and brain perfusion in infants undergoing ventricular septal defect repair.

The 'right way' to the left chamber in non-severe COPD: Echocardiographic predictors for stress-induced left ventricular diastolic dysfunction.

Dyspnea is a major complaint of both chronic obstructive pulmonary disease (COPD) and heart failure with preserved ejection fraction (HFpEF). It often remains underdiagnosed in COPD patients when only echocardiography at rest is performed. The aim of this study was to evaluate the predictive value of cardiopulmonary and echocardiographic parameters at rest for the diagnosis of HFpEF in non-severe COPD patients who complain of exertional dyspnea and have no overt cardiovascular disease. A total of 104 COPD patients underwent echocardiography before cardiopulmonary exercise testing (CPET) and 1-2 minutes after peak exercise. The patients were divided into 2 groups based on peak E/e' measurements: patients with masked HFpEF-stress and left ventricular diastolic dysfunction (LVDD; E/e'>15), and patients without masked HFpEF (without stress LVDD). CPET and echocardiographic parameters at rest were measured and the predictive value for stress E/e' was analyzed. Stress LVDD occurred in 67 of 104 patients (64%). These patients achieved a lower work load, lower 'VO2 consumption, lower minute ventilation, and higher 'VE/'VCO2 slope in comparison with patients without stress LVDD. None of the CPET values correlated with stress E/e'. The best independent predictors for stress LVDD were right atrium volume index (RAVI), right ventricle (RV) parasternal diameter, and RV E/A >0.75. The combination of these echocardiographic parameters predicted HFpEF with an accuracy of 91.2%. There is a high prevalence of stress LVDD in non-severe COPD patients with exertional dyspnea who remain free of overt cardiovascular disease. RAVI, RV parasternal diameter, and RV E/A >0.75 were the only independent predictors of stress LVDD.

Hypercapnia in Advanced Chronic Obstructive Pulmonary Disease: A Secondary Analysis of the National Emphysema Treatment Trial.

Hypercapnia develops in one third of patients with advanced chronic obstructive pulmonary disease (COPD) and is associated with increased morbidity and mortality. Multiple factors in COPD are thought to contribute to the development of hypercapnia including increased carbon dioxide (CO2) production, increased dead space ventilation, and the complex interactions of deranged respiratory system mechanics, inspiratory muscle overload and the ventilatory control center in the brainstem. However, these factors have not previously been systematically analyzed in a large, well-characterized population of severe COPD patients. This is a secondary analysis of the clinical, physiologic and imaging data from the National Emphysema Treatment Trial (NETT). All patients with complete baseline data for the key predictor variables were included. An inclusive list of 32 potential predictor variables were selected a priori based on consensus of the investigators and literature review. Stepwise variable selection yielded 10 statistically significant associations in multivariate regression. A total of 1419 patients with severe COPD were included in the analysis; mean age 66.4 years (standard deviation 6.3), 38% females, and 422 (29.7%) had baseline hypercapnia. Key variables associated with hypercapnia were low resting partial pressure of oxygen in blood, low minute ventilation (Ve), high volume of exhaled carbon dioxide, low forced expiratory volume in 1 second, high residual volume, lower % emphysema on chest computed tomography, use of oxygen, low ventilatory reserve (high Ve/maximal voluntary ventilation), and not being at high altitude. Low diffusing capacity for carbon monoxide showed a positive association with hypercapnia in univariate analysis but a negative correlation in multivariate analysis. Measures of dyspnea and quality of life did not associate with degree of hypercapnia in multivariable analysis. Hypercapnia in a well-characterized cohort with severe COPD and emphysema is chiefly related to poor lung mechanics, high CO2 production, and a reduced ventilatory capability. Hypercapnia is less impacted by gas exchange abnormalities or the presence of emphysema.

Impact of Thoracic Cage Dimension and Geometry on Cardiopulmonary Function in Patients With Congenital Scoliosis: A Prospective Study.

A prospective study of cardiopulmonary function in patients with congenital scoliosis (CS). To investigate the relationship of thoracic cage deformity and exercise tolerance in CS patients. Congenital thoracic scoliosis and chest deformity lead to restrictive pulmonary dysfunction and in some severe cases cause cardiopulmonary failure. However, it is still unknown the relationship between thoracic deformity and exercise performance. Patients with congenital thoracic spinal deformity were included and had radiological assessment of thoracic cage, pulmonary function testing, and cardiopulmonary exercise testing. Thoracic dimension including height, width, and depth were measured and geometry parameters were calculated. Two-tailed Pearson and Spearman correlation test and linear regression analysis were performed to investigate correlation of radiographic parameters, pulmonary function, and physical capacity. Sixty patients (41 females and 19 males) were included, with an average age of 18.9 years. Patients with smaller thoracic height (P < 0.001) and width (P < 0.01) and larger depth (P < 0.05) had significantly worse static pulmonary function. In exercise testing, these patients showed significant tendency of ventilation insufficiency, including lower minute ventilation (P < 0.05), faster breathing frequency (P < 0.05), and smaller tidal volume (P < 0.01). Thoracic depth was negatively correlated to exercise capacity, reflected by work rate (P < 0.001), peak oxygen intake (P < 0.001), and heart rate (P = 0.043). Patients with abnormal thoracic geometry, especially a lower ratio of height to depth and a lower ratio of width to depth, have significantly worse static pulmonary function and exercise capacity (all P < 0.05). Decreasing thoracic height and width results in restrictive pulmonary dysfunction. Distortion and asymmetry of the thoracic cage are associated with abnormal breathing pattern and reduction of exercise capacity. 3.

Minute ventilation assessment in the PACU is useful to predict postoperative respiratory depression following discharge to the floor: A prospective cohort study

Study Objective.Reliably identifying patients at risk for postoperative respiratory depression (RD) remains an unmet need. We hypothesized that defined low minute ventilation events (LMVe) near the end of the post-anesthesia care unit (PACU) stay identifies patients at RD risk on the general hospital floor (GHF). DesignProspective observational study. SettingTertiary care, urban academic medical center. PACU and GHF during the first postoperative night. PatientsOne hundred-and-nineteen adult, ASA I – III patients undergoing elective surgery under general anesthesia completed the study. InterventionsData collection from a non-invasive respiratory volume monitor and the patients' medical record perioperatively through the first postoperative night. MeasurementsMinute ventilation (MV), tidal volume (TV) and respiratory rate (RR) were measured continuously in the PACU and on the GHF. MV was counted as the percent of individual predicted MV (MVPRED), and RD was defined as ≥1 LMVe/h on the GHF. Based on the number of LMVes within 30 min before PACU discharge, patients were grouped into A, ‘Not-At-Risk’: 0 LMVe and B, ‘At-Risk’: ≥1 LMVes. Unpaired t-test, Mann-Whitney U test, ANOVA, Kruskal-Wallis test, Fisher's exact test, sensitivity and specificity and ROC curve analyses were applied as appropriate. Main resultsOne hundred-and-six (89%) and 13 (11%) patients met Group A and B criteria respectively. The latter had more LMVe/h on the GHF (median 0.81 vs 0, p ≤ 0.001), and their MVPRED was significantly less. Following opioid administration, the LMVe likelihood was 43% in Group B and 5.6% in Group A. As a predictor for RD on the GHF, the number of LMVe in the last 30 min of PACU, had positive and negative predictive values of 61.5% and 90.6%, respectively. ConclusionMinute ventilation assessment in the PACU as described in this study can be useful to identify patients at risk for postoperative respiratory depression.