Ventilator- and interface-related factors influencing patient-ventilator asynchrony during noninvasive ventilation.

Patient-ventilator asynchrony (PVA) is common in patients receiving noninvasive ventilation (NIV). This occurs primarily when the triggering and cycling-off of ventilatory assistance are not synchronized with the patient's inspiratory efforts and could result in increased work of breathing and niv failure. In general, five types of asynchrony can occur during NIV: ineffective inspiratory efforts, double-triggering, auto-triggering, short-ventilatory cycling, and long-ventilatory cycling. Many factors that affect PVA are mostly related to the degree of air leakage, level of pressure support, and the type and properties of the interface used. Careful monitoring and adjustment of these factors are essential to reduce PVA and improve patient comfort. In this article, we discuss the machine and interface-related factors that influence PVA during NIV and its effect on the respiratory mechanics during pressure support ventilation, which is the ventilatory mode used most commonly during NIV. For that, we critically evaluated studies that assessed ventilator- and interface-related factors that influence PVA during NIV and proposed therapeutic solutions.

Left ventricular diastolic dysfunction in patients with obesity hypoventilation syndrome.

BACKGROUND: Obesity hypoventilation syndrome (OHS) can be complicated by several cardiovascular conditions. We assessed the prevalence and factors associated with left ventricular diastolic dysfunction (LVDD) in patients with OHS. METHODS: In this prospective observational study, all consecutive OHS patients referred to the sleep disorders clinic between January 2002 to December 2016 were included (n=113). Demographic data, echocardiography, sleep parameters, arterial blood gases (ABGs), and lung functions were recorded. RESULTS: Of 113 patients with OHS who participated, 76 patients (67%) had LVDD. More than two-thirds had grade 1 LVDD. Median body mass index (BMI) was 42.8 kg/m2. Median PaCO2 was 55.8 mmHg. Median apnea hypopnea index (AHI) was 52 (25-38.5). Eighty-four (75.7%) patients were hypertensive, and 60 (54.1%) were diabetic. To minimize the effect of fluctuations in intrathoracic pressure during the obstructive respiratory events on the cardiac function, 38 OHS patients with mild to moderate OSA (AHI <30) were identified. Twenty-seven (71%) had LVDD. When compared to OHS patients without LVDD, patients with LVDD had higher BMI (47.4±6.5 versus 41.5±4.5, P=0.009). Hypertension was more common in OHS patients with LVDD than without LVDD (89.3% versus 54.5%, P=0.03). Correlation analysis revealed that hypertension (r=-0.37, P=0.016) had significant correlations with LVDD. CONCLUSIONS: Diastolic left ventricular dysfunction is prevalent among OHS patients even in the absence of severe OSA. Hypertension and obesity were significantly more common in patients with LVDD. Assessment of diastolic dysfunction should be included in the initial evaluation of OHS patients to encourage the early institution of therapy.

Assessment of antigen presenting cell infiltration in lung tissues of patients with bronchiectasis.

BACKGROUND: Bronchiectasis is a chronic disease characterized by permanent dilatation of the conducting airways accompanied by sustained inflammation. AIMS: To assess whether chronic inflammation of lungs in bronchiectasis is associated with alterations in the numbers of infiltrating antigen presenting cell (APC). SETTING AND DESIGN: Lobectomy specimens from 12 nonsmoker, nonasthmatic patients with acquired (noncongenital) bronchiectasis and six control patients were included in the study. Histopathology slides were reviewed, and immunohistochemical markers for dendritic cells (DCs) macrophages and Langerhans cells have been applied and analyzed. MATERIALS AND METHODS: Tissue specimens were stained by immunohistochemistry using markers for DCs (CD83 and CD23), macrophages (CD68 and CD163), and Langerhans cells (CD1A and S-100 protein). The mean cell counts of stained cells in five high power microscopic fields were recorded. STATISTICAL ANALYSIS USED: Descriptive statistics, mean, standard deviation, median, and interquartile range were used. A nonparametric Mann-Whitney U-test was used to compare cell counts between bronchiectasis and control patients. P <0.05 was considered significant. RESULTS: The mean age of patients with bronchiectasis and controls was 36.7 ± 16.6 and 31.8 ± 22.6 years, respectively. The predominant cell type among the patients was macrophage (median 50.5) followed by DCs (median 44.85), histiocytes (median 32), and Langerhans cells (median 5%). Compared to the controls a significantly higher number of macrophages (P = 0.01), DCs (P = 0.001), and Langerhans cells (P = 0.014) were present. CONCLUSION: Chronic inflammatory response in acquired (noncongenital) bronchiectasis is most probably mediated by increased infiltration of APCs in lung tissues.

The Levels of Tissue Factor Pathway Inhibitor in Sepsis Patients Receiving Prophylactic Enoxaparin.

OBJECTIVE: Sepsis syndrome is usually accompanied by activation of blood coagulation mechanisms. Earlier studies found deficiencies of the 3 main natural anticoagulants, antithrombin, protein C, and protein S. However, none of these inhibitors block tissue factor, the prime trigger of coagulation during sepsis that is controlled specifically by the tissue factor pathway inhibitor (TFPI). The aim of this study was to characterize the fluctuations in the levels of natural anticoagulants, particularly TFPI, in the course of sepsis and to find out their association with the anticoagulant action of the low-molecular-weight heparin enoxaparin. MATERIALS AND METHODS: We studied 51 consecutive patients with sepsis. Blood samples were collected from patients at baseline (0 h) and at 4, 12, and 24 h after enoxaparin administration. The following assays were undertaken using commercial kits: activated partial thromboplastin time, prothrombin time, thrombin time, total and free TFPI, protein C and protein S, antithrombin, fibrinogen, and anti-factor Xa. RESULTS: Before enoxaparin administration, there was significant prolongation of the prothrombin time and activated partial thromboplastin time, and this remained the case in the 3 subsequent samples. There was marked reduction in the levels of antithrombin, protein C, and total and free protein S to below control values throughout the study. In contrast, plasma levels of both total and free TFPI were markedly elevated and increased after enoxaparin therapy. Anti-factor Xa levels were within the therapeutic range throughout. There was no difference in TFPI levels between those patients who died and those who survived. CONCLUSION: Sepsis triggered marked release of TFPI from endothelial cells. This persisted and was increased further following the administration of enoxaparin. In contrast, there was marked consumption of the natural coagulation inhibitors antithrombin, protein C, and protein S. These results go some way towards explaining why the therapeutic use of recombinant TFPI fails to correct sepsis-associated coagulopathy.

A case of near fatal asthma: The role of ECMO as rescue therapy.

We report a case of an adolescent with near fatal asthma (NFA). He presented with severe hypoxemia and lifethreatening acidemia, who failed to respond to conventional therapy. His hospital course was complicated by barotrauma and hemodynamic instability. Early introduction of extracorporeal membrane oxygenation (ECMO) led to dramatic improvement in gas exchange and lung mechanics. This case illustrates the important role of ECMO as salvage therapy in NFA.

Outcome of pulmonary embolism and clinico-radiological predictors of mortality: Experience from a university hospital in Saudi Arabia.

OBJECTIVES: The objective of this study is to determine the outcome of pulmonary embolism (PE) and the clinico-radiological predictors of mortality in a university hospital setting. METHODS: A Prospective observational study conducted at King Khalid University Hospital, Riyadh Saudi Arabia between January 2009 and 2012. A total of 105 consecutive patients (49.9 ± 18.7 years) with PE diagnosed by computed tomography pulmonary angiography were followed until death or hospital discharge. RESULTS: Overall in hospital mortality rate was 8.6%, which is lower than other international reports. Two-thirds of patients developed PE during the hospitalization. The most common risk factors were surgery (35.2%), obesity (34.3%) and immobility (30.5%). The localization of the embolus was central in 32.4%, lobar in 19% and distal in 48.6%. A total of 26 patients (25%) had evidence of right ventricular strain and 14 (13.3%) were hypotensive. Multivariate analysis revealed that heart failure (Beta = -0.53, P < 0.001), palpitation (Beta = -0.24, P = 0.014) and high respiratory rate (Beta = -0.211, P < 0.036) were significant predictors of mortality. There was no significant difference in the localization of the embolus or obstruction score between survivors and non-survivors. CONCLUSION: The outcome of PE is improving; however, it remains an important risk factor for mortality in hospitalized patients. Congestive heart failure, tachypnea and tachycardia at presentation were associated with higher mortality. These factors need to be considered for risk stratification and management decisions of PE patients. Radiological quantification of clot burden was not a predictor of death.

Bronchoscopy as a rescue therapy in patients with status asthmaticus: Two case reports and review of literature.

Management of status asthmaticus requires more than guidelines-guided therapy. Occasionally, uncommon therapeutic interventions and procedures may provide significant benefits. The role of bronchoscopy in fatal asthma is still not clearly defined. We illustrate two cases of severe status asthmaticus on mechanical ventilation who showed remarkable improvement after therapeutic bronchoscopy.

Venous thromboembolism in a medical intensive care unit. The effect of implementing clinical practice guidelines.

OBJECTIVE: To determine the incidence of VTE in medical patients admitted to the intensive care unit (ICU) following the implementation of a standard deep venous thrombosis (DVT) prophylaxis protocol using unfractionated heparin (UFH), and to identify risk factors for DVT in these patients. METHODS: We prospectively studied 123 consecutive patients admitted to the Medical ICU of King Khalid University Hospital, Riyadh, Saudi Arabia. We excluded patients on anticoagulation or with contraindications for heparin. Patients who were negative for DVT by screening Doppler Ultrasound (U/S) were started on UFH twice a day. The Doppler U/S was repeated twice weekly for 6 weeks. RESULTS: One hundred and four critically ill medical patients were included. A DVT was diagnosed in 10 patients while receiving UFH, an incidence rate of 9.8%. The compliance rate was 98%. Sepsis (p=0.0167), limited mobility (p<0.0001), previous DVT (p=0.024), and nephrotic syndrome (p=0.008) were significantly more common in patients who developed DVT compared with others. However, by backward logistic regression, previous DVT was the only significant factor for the development of DVT (B=-0.439, AOR=5.01, p<0.0001). CONCLUSION: The implementation of clinical practice guidelines for VTE prophylaxis in critically ill medical patients using UFH twice daily resulted in a high compliance rate and low incidence of VTE. Previous DVT was a significant risk factor for development of VTE.

Prediction of pulmonary hypertension in patients with or without interstitial lung disease: reliability of CT findings.

PURPOSE: To study the reliability of pulmonary vascular measurements based on computed tomography (CT) in the prediction of pulmonary hypertension (PH) in patients with advanced interstitial lung disease (ILD) compared with those without ILD. MATERIALS AND METHODS: The study was approved by the Institutional Review Board. All patients gave written informed consent. A prospective study of 134 patients who underwent right-sided heart catheterization and chest CT scanning within 72 hours of admission was conducted. Patients were divided into two groups-one with ILD (group A, n = 100) and one without ILD (group B, n = 34). CT measurements of the main pulmonary artery diameter (PAD), the ratio of PAD to the ascending aorta diameter (AAD), right pulmonary artery diameter (RPAD), and left pulmonary artery diameter (LPAD) were obtained. Univariate logistic regression analysis was performed, and receiver operating characteristic curves were constructed to assess the predictive ability of vascular measurements obtained by using CT in the identification of PH. RESULTS: Main PAD was significantly greater in patients with PH than in those without PH in both groups (group A, P = .008; group B, P = .02). A PAD greater than 25 mm in patients with ILD was predictive of PH, with a sensitivity of 86.4% (32 of 37), a specificity of 41.2% (26 of 63), a positive predictive value of 46.3% (32 of 69), and a negative predictive value of 83.8% (26 of 31). In patients without ILD, a PAD greater than 31.6 mm and an LPAD greater than 21.4 mm were predictive of PH (sensitivity, 47.3% [nine of 19]; specificity, 93.3% [14 of 15]; positive predictive value, 90.0% [nine of 10]; and negative predictive value, 58.3% [14 of 24]). CONCLUSION: CT-derived vascular measurements were of limited utility in the prediction of PH in patients with ILD compared with those without ILD.

Yield and complications of flexible fiberoptic bronchoscopy in a teaching hospital.

OBJECTIVE: To assess the diagnostic yield and safety of flexible fiberoptic bronchoscopy (FFB). METHODS: A retrospective review of bronchoscopy reports and corresponding patients charts over 3 years from January 2004 - December 2006 in King Khalid University Hospital, Riyadh, Kingdom of Saudi Arabia. Indication for procedure, suspected diagnosis, final diagnosis, and complications were reported. RESULTS: Out of 720 patients, 707 (98.2%) patients had a full follow up. Five hundred and ninety-two (83.7%) underwent FFB for diagnostic purposes and 115 (16.3%) for therapeutic purposes. The mean age was 42 -/+ 18 years. Infection, including mycobacterium tuberculosis, and malignancy were the 2 main indications for FFB (35.9% and 25.9%). The overall diagnostic yield was 58%. Tuberculosis was diagnosed in 67% of suspected cases, whereas bacterial pneumonia was diagnosed in 40.5%. Malignancy was confirmed in 61.2% of suspected cases. Bronchoscopy diagnosed 37 (43%) of 86 patients with interstitial lung disease. The diagnostic yield was 57% for sarcoidosis, 40% for usual interstitial pneumonia and 88% for bronchiolitis obliterans organizing pneumonia. The overall complication rate was 5%; pneumothorax occurred in 0.56% and was associated exclusively with transbronchial biopsy. No mortality was observed. CONCLUSION: Flexible fiberoptic bronchoscopy is a useful diagnostic tool with a low rate of complications. The diagnostic yield in our institution is similar to that reported in Western series.

Right and left ventricular function and pulmonary artery pressure in patients with bronchiectasis.

BACKGROUND: Bronchiectasis may have deleterious effects on cardiac function secondary to pulmonary hypertension (PH). This study was designed to assess cardiac function and determine the prevalence of PH in patients with cystic and cylindrical bronchiectasis. METHODS: A cross-sectional study of patients with bronchiectasis diagnosed by CT scan was conducted at King Khalid University Hospital, Riyadh, Saudi Arabia between December 2005 and January 2007. Pulmonary function tests were performed, arterial blood gas measurements were made, and cardiac function and systolic pulmonary artery pressure (SPAP) were assessed by echocardiography. RESULTS: Of 94 patients (31% men, n = 29), 62 patients (66%) had cystic bronchiectasis and 32 patients (34%) had cylindrical bronchiectasis. Right ventricular (RV) systolic dysfunction was observed in 12 patients (12.8%), left ventricular (LV) systolic dysfunction was observed in 3 patients (3.3%), and LV diastolic dysfunction was observed in 11 patients (11.7%); all had cystic bronchiectasis. RV dimensions were significantly greater in the cystic bronchiectasis group, and were positively correlated with SPAP (p < 0.0001) and negatively correlated with Pao2 (p < 0.016). Other hemodynamic variables were not different between groups. PH in 31 patients (32.9%) was significantly greater in patients with cystic bronchiectasis compared with cylindrical bronchiectasis (p = 0.04). In cystic bronchiectasis, SPAP was positively correlated with Paco2 (p = 0.001), and inversely correlated with Pao2 (p = 0.03), diffusion capacity of the lung for carbon monoxide percentage (p = 0.02), and FEV1 (p = 0.02). CONCLUSIONS: RV systolic dysfunction and PH were more common than LV systolic dysfunction in bronchiectatic patients. LV diastolic dysfunction was mainly seen in severe PH. We recommend detailed assessment of cardiac function, particularly LV diastolic function, in patients with bronchiectasis.