<p>ST2 Predicts Mortality In Patients With Acute Hypercapnic Respiratory Failure Treated With Noninvasive Positive Pressure Ventilation</p>

Background

Patients with Acute Hypercapnic Respiratory Failure (AHRF) are often treated with Noninvasive Positive Pressure Ventilation (NPPV). In this heterogeneous patient group, there is a lack of clinical tools for predicting mortality and outcome.

Aims

In order to facilitate the choice of treatment in patients with AHRF we evaluated the protein ST2, an established biomarker for cardiac stress, and its role in predicting mortality in patients with AHRF treated with NPPV. We also examined if ST2 baseline levels and changes during the first 12 hrs of treatment were predictive of treatment outcome.

Methods

The study population consisted of 46 patients treated with NPPV for AHRF. Background data and clinical parameters were obtained and blood samples taken at various time points during the treatment. During the follow-up period of 18 months, the prognostic value of ST2 with regards to mortality was evaluated using Cox proportional hazard model.

Results

Of the 46 patients, there were 3 subgroups in regards to primary diagnosis: Acute Exacerbation of COPD (n=34), Acute Heart Failure (n=8) and Acute Exacerbation in Obesity Hypoventilation Syndrome (n=4). We found that ST2 was an independent predictor of both short-term and long-term mortality during the follow-up period. The Hazard Ratio (HR) per 1-SD increment of ST2 for 28-day mortality was 11.00 (95% CI 1.8–67.2, p 0.009) and for 18-month mortality 2.11 (95% CI 1.4–3.2, p 0.001). The results seem to be driven by the largest subgroup of patients, with Acute Exacerbation of COPD, and deaths within the first 28 days. Furthermore, changes in ST2 values during the first 12 hrs of treatment were not predictive of treatment outcome.

Conclusion

Our results show that ST2 is a target to explore further as a predictor of short-term mortality in patients with AHRF treated with NPPV.

Late presentation of acute hypercapnic respiratory failure carries a high mortality risk in COPD patients treated with ward-based NIV

INTRODUCTION

Non-invasive ventilation (NIV) is recommended for treatment of acute hypercapnic respiratory failure (AHRF) refractory to medical management in patients with COPD. This study investigated the relationship between time from hospital presentation to diagnosis of AHRF and in-hospital mortality.

METHODS

Retrospective analysis of hospitalised COPD patients treated with a first episode of ward-based NIV for AHRF at a large UK teaching hospital between 2004 and 2017. Data collected prospectively as part of NIV service evaluation. Multivariable logistic regression performed to identify predictors of in-hospital mortality.

RESULTS

In total, 547 unique patients were studied comprising 245 males (44.8%), median age 70.6 years, median FEV1% predicted 34%. Overall in-hospital mortality was 19% (n = 104); median survival was 1.7 years. In univariate analysis, a longer time between hospital presentation to diagnosis of AHRF was associated with in-hospital mortality (median [IQR]: 8.7 [0.7-75.8] hours vs. 1.9 [0.3-13.6] hours, p < 0.0001). In multivariable logistic regression, significant predictors of in-hospital mortality were AHRF >24 h after hospital presentation (odds ratio [95% CI]: 2.29 [1.33-3.95], p = 0.003), pneumonia on admission (1.81 [1.07-3.08], p = 0.027), increased age (1.10 [1.07-1.14], p < 0.001) and NIV as ceiling of treatment (5.86 [2.87-11.94], p < 0.001).

CONCLUSIONS

Hospitalised COPD patients with late presentation of AHRF, requiring acute ward-based NIV, may have increased in-hospital mortality. These patients may benefit from closer monitoring and earlier specialist respiratory review.

High-intensity versus low-intensity noninvasive positive pressure ventilation in patients with acute exacerbation of chronic obstructive pulmonary disease (HAPPEN): study protocol for a multicenter randomized controlled trial

BACKGROUND

Despite the positive outcomes of the use of noninvasive positive pressure ventilation (NPPV) in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD), NPPV fails in approximately 15% of patients with AECOPD, possibly because the inspiratory pressure delivered by conventional low-intensity NPPV is insufficient to improve ventilatory status for these patients. High-intensity NPPV, a novel form that delivers high inspiratory pressure, is believed to more efficiently augment alveolar ventilation than low-intensity NPPV, and it has been shown to improve ventilatory status more than low-intensity NPPV in stable AECOPD patients. Whether the application of high-intensity NPPV has therapeutic advantages over low-intensity NPPV in patients with AECOPD remains to be determined. The high-intensity versus low-intensity NPPV in patients with AECOPD (HAPPEN) study will examine whether high-intensity NPPV is more effective for correcting hypercapnia than low-intensity NPPV, hence reducing the need for intubation and improving survival.

METHODS/DESIGN

The HAPPEN study is a multicenter, two-arm, single-blind, prospective, randomized controlled trial. In total, 600 AECOPD patients with low to moderate hypercapnic respiratory failure will be included and randomized to receive high-intensity or low-intensity NPPV, with randomization stratified by study center. The primary endpoint is NPPV failure rate, defined as the need for endotracheal intubation and invasive ventilation. Secondary endpoints include the decrement of arterial carbon dioxide tension from baseline to 2 h after randomization, in-hospital and 28-day mortality, and 90-day survival. Patients will be followed up for 90 days after randomization.

DISCUSSION

The HAPPEN study will be the first randomized controlled study to investigate whether high-intensity NPPV better corrects hypercapnia and reduces the need for intubation and mortality in AECOPD patients than low-intensity NPPV. The results will help critical care physicians decide the intensity of NPPV delivery to patients with AECOPD.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02985918 . Registered on 7 December 2016.

Partial pressure of arterial carbon dioxide and survival to hospital discharge among patients requiring acute mechanical ventilation: A cohort study

PURPOSE

To describe the prevalence of hypocapnia and hypercapnia during the earliest period of mechanical ventilation, and determine the association between PaCO2 and mortality.

MATERIALS AND METHODS

A cohort study using an emergency department registry of mechanically ventilated patients. PaCO2 was categorized: hypocapnia (<35mmHg), normocapnia (35-45mmHg), and hypercapnia (>45mmHg). The primary outcome was survival to hospital discharge.

RESULTS

A total of 1,491 patients were included. Hypocapnia occurred in 375 (25%) patients and hypercapnia in 569 (38%). Hypercapnia (85%) had higher survival rate compared to normocapnia (74%) and hypocapnia (66%), P<0.001. PaCO2 was an independent predictor of survival to hospital discharge [hypocapnia (aOR 0.65 (95% confidence interval [CI] 0.48-0.89), normocapnia (reference category), hypercapnia (aOR 1.83 (95% CI 1.32-2.54)]. Over ascending ranges of PaCO2, there was a linear trend of increasing survival up to a PaCO2 range of 66-75mmHg, which had the strongest survival association, aOR 3.18 (95% CI 1.35-7.50).

CONCLUSIONS

Hypocapnia and hypercapnia occurred frequently after initiation of mechanical ventilation. Higher PaCO2 levels were associated with increased survival. These data provide rationale for a trial examining the optimal PaCO2 in the critically ill.

Effects of Hypercapnia and Hypercapnic Acidosis on Hospital Mortality in Mechanically Ventilated Patients

OBJECTIVES

Lung-protective ventilation is used to prevent further lung injury in patients on invasive mechanical ventilation. However, lung-protective ventilation can cause hypercapnia and hypercapnic acidosis. There are no large clinical studies evaluating the effects of hypercapnia and hypercapnic acidosis in patients requiring mechanical ventilation.

DESIGN

Multicenter, binational, retrospective study aimed to assess the impact of compensated hypercapnia and hypercapnic acidosis in patients receiving mechanical ventilation.

SETTINGS

Data were extracted from the Australian and New Zealand Intensive Care Society Centre for Outcome and Resource Evaluation Adult Patient Database over a 14-year period where 171 ICUs contributed deidentified data.

PATIENTS

Patients were classified into three groups based on a combination of pH and carbon dioxide levels (normocapnia and normal pH, compensated hypercapnia [normal pH with elevated carbon dioxide], and hypercapnic acidosis) during the first 24 hours of ICU stay. Logistic regression analysis was used to identify the independent association of hypercapnia and hypercapnic acidosis with hospital mortality.

INTERVENTIONS

Nil.

MEASUREMENTS AND MAIN RESULTS

A total of 252,812 patients (normocapnia and normal pH, 110,104; compensated hypercapnia, 20,463; and hypercapnic acidosis, 122,245) were included in analysis. Patients with compensated hypercapnia and hypercapnic acidosis had higher Acute Physiology and Chronic Health Evaluation III scores (49.2 vs 53.2 vs 68.6; p < 0.01). The mortality was higher in hypercapnic acidosis patients when compared with other groups, with the lowest mortality in patients with normocapnia and normal pH. After adjusting for severity of illness, the adjusted odds ratio for hospital mortality was higher in hypercapnic acidosis patients (odds ratio, 1.74; 95% CI, 1.62-1.88) and compensated hypercapnia (odds ratio, 1.18; 95% CI, 1.10-1.26) when compared with patients with normocapnia and normal pH (p < 0.001). In patients with hypercapnic acidosis, the mortality increased with increasing PCO2 until 65 mm Hg after which the mortality plateaued.

CONCLUSIONS

Hypercapnic acidosis during the first 24 hours of intensive care admission is more strongly associated with increased hospital mortality than compensated hypercapnia or normocapnia.

Permissive hypercapnia for severe acute respiratory distress syndrome in immunocompromised children: A single center experience

BACKGROUND

Controlled hypoventilation while accepting hypercapnia has been advocated to reduce ventilator-induced lung injury. The aim of the study was to analyze outcomes of a cohort of immunocompromised children with acute respiratory distress syndrome (ARDS) ventilated with a strategy of stepwise increasing PCO2 targets up to 140 mm Hg.

METHODS

Retrospective analysis of outcomes of a cohort of children with oncologic disease or after stem cell transplantation and severe respiratory failure in comparison with a historical control cohort.

RESULTS

Out of 150 episodes of admission to the PICU 88 children underwent invasive mechanical ventilation for >24h (overall survival 75%). In a subgroup of 38 children with high ventilator requirements the PCO2 target ranges were increased stepwise. Fifteen children survived and were discharged from the PICU. Severe pulmonary hypertension was seen in two patients and no case of cerebral edema was observed. Long term outcome was available in 15 patients and 10 of these patients survived without adverse neurological sequelae. With introduction of this strategy survival of immunocompromised children undergoing mechanical ventilation for >24h increased to 48% compared to 32% prior to introduction (historical cohort).

CONCLUSIONS

A ventilation strategy incorporating very high carbon dioxide levels to allow for low tidal volumes and limited inspiratory pressures is feasible in children. Even severe hypercapnia may be well tolerated. No severe side effects associated with hypercapnia were observed. This strategy could potentially increase survival in immunocompromised children with severe ARDS.

Early use of noninvasive techniques for clearing respiratory secretions during noninvasive positive-pressure ventilation in patients with acute exacerbation of chronic obstructive pulmonary disease and hypercapnic encephalopathy: A prospective cohort study

Noninvasive positive-pressure ventilation (NPPV) might be superior to conventional mechanical ventilation (CMV) in patients with acute exacerbations of chronic obstructive pulmonary disease (AECOPDs). Inefficient clearance of respiratory secretions provokes NPPV failure in patients with hypercapnic encephalopathy (HE). This study compared CMV and NPPV combined with a noninvasive strategy for clearing secretions in HE and AECOPD patients.The present study is a prospective cohort study of AECOPD and HE patients enrolled between October 2013 and August 2015 in a critical care unit of a major university teaching hospital in China.A total of 74 patients received NPPV and 90 patients received CMV. Inclusion criteria included the following: physician-diagnosed AECOPD, spontaneous airway clearance of excessive secretions, arterial blood gas analysis requiring intensive care, moderate-to-severe dyspnea, and a Kelly-Matthay scale score of 3 to 5. Exclusion criteria included the following: preexisting psychiatric/neurological disorders unrelated to HE, upper gastrointestinal bleeding, upper airway obstruction, acute coronary syndromes, preadmission tracheostomy or endotracheal intubation, and urgent endotracheal intubation for cardiovascular, psychomotor agitation, or severe hemodynamic conditions.Intensive care unit participants were managed by NPPV. Participants received standard treatment consisting of controlled oxygen therapy during NPPV-free periods; antibiotics, intravenous doxofylline, corticosteroids (e.g., salbutamol and ambroxol), and subcutaneous low-molecular-weight heparin; and therapy for comorbidities if necessary. Nasogastric tubes were inserted only in participants who developed gastric distension. No pharmacological sedation was administered.The primary and secondary outcome measures included comparative complication rates, durations of ventilation and hospitalization, number of invasive devices/patient, and in-hospital and 1-year mortality rates.Arterial blood gases and sensorium levels improved significantly within 2 hours in the NPPV group with lower hospital mortality, fewer complications and invasive devices/patient, and superior weaning off mechanical ventilation. Mechanical ventilation duration, hospital stay, or 1-year mortality was similar between groups.NPPV combined with a noninvasive strategy to clear secretions during the first 2 hours may offer advantages over CMV in treating AECOPD patients complicated by HE.

Early failure of noninvasive ventilation in chronic obstructive pulmonary disease with acute hypercapnic respiratory failure

Noninvasive ventilation (NIV) in the management of chronic obstructive pulmonary disease (COPD) patients with acute hypercapnic respiratory failure is considered a first-line therapy. However, patients who fail NIV and then require invasive mechanical ventilation have been found to have higher mortality than patients initially treated with invasive mechanical ventilation. We tried to find parameters associated with early NIV failure (need for intubation or death <24 h of starting NIV) in patients presenting to the ED with acute exacerbation of COPD. A retrospective analysis was conducted of the medical records of 218 patients with acute exacerbation of COPD visiting Asan Medical Center and managed with NIV during their stay in the ED from January 2007 to December 2013. NIV was successful in 200 (91.7%) and 18 (8.3%) had early NIV failure. Of the variables obtained before NIV treatment, heart rate (≥120/min: OR 2.5, 95% CI 1.2-7.0) and pH (7.25-7.29: OR 2.1, 95% CI 1.0-8.8; <7.25: OR 11.7, 95% CI 3.5-38.6) were significant factors associated with early NIV failure. Of the variables obtained after 1 h of NIV treatment, heart rate (≥120/min: OR 7.5, 95% CI 2.3-24.3) and pH (7.25-7.29: OR 4.7, 95% CI 1.5-15.1; <7.25: OR 20.9, 95% CI 5.4-61.2) were still significant. The presence of tachycardia and severe acidosis before NIV treatment and persistence of tachycardia and severe acidosis after 1 h of NIV treatment were associated with early NIV failure.

Persistent hypercarbia after resuscitation is associated with increased mortality in congenital diaphragmatic hernia patients

BACKGROUND

Within congenital diaphragmatic hernia (CDH) care, there have been attempts to identify clinical parameters associated with patient survival, including markers of postnatal pulmonary gas exchange. This study aimed to identify whether postnatal pulmonary gas exchange parameters correlated with CDH patient survival.

METHODS

A retrospective review was performed of isolated CDH neonates treated at a single institution from 1/2007 to 12/2013. Patient demographics, prenatal imaging, and postnatal clinical parameters, including arterial blood gas values within the first 24hours of life, were collected.

RESULTS

Seventy-four patients with isolated CDH were identified. Fifty-seven had fetal MRI. Overall, 30-day patient survival was 85%. Sixteen infants (22%) required ECMO within 24hours. Mean initial PaCO2 in nonsurvivors was higher, and infants who remained hypercarbic postresuscitation (72±19mmHg) had a worse prognosis than those who resuscitated to a normal PaCO2 (39±1.6mmHg) (p<0.001). Prenatal fetal lung volumes measured by MRI were not strongly correlated with PaCO2 levels.

CONCLUSION

CDH nonsurvivors are unable to maintain sufficient pulmonary gas exchange during the first 24hours of resuscitation. Furthermore, prenatal fetal lung volumes are weakly correlated with actual pulmonary gas exchange. These data may be useful for patient counseling during the resuscitative phase of CDH care.

Noninvasive ventilation for hypercapnic exacerbation of chronic obstructive pulmonary disease: factors related to noninvasive ventilation failure

INTRODUCTION

Noninvasive ventilation (NIV) has changed the prognosis of patients with chronic obstructive pulmonary disease (COPD) suffering from hypercapnic exacerbations.

OBJECTIVES

The aim of the study was to evaluate the mortality rate and need for intubation of patients with during hypercapnic COPD exacerbation treated with NIV and to estimate factors related to either success or failure of NIV in a real-life setting.

PATIENTS AND METHODS

In a multicenter prospective study conducted over a period of 10 years (2002-2012), we assessed 1809 patients with COPD with hypercapnic exacerbation on admission who were treated with NIV. The primary outcomes were the intubation rate and hospital mortality.

RESULTS

In all patients, NIV was conducted by experienced specialists. The intubation rate was 6.6% and the mortality rate was 5.3%. The severity of exacerbations, defined by pH and the Simplified Acute Physiology Score (SAPS II) on admission, worsened during the study period. The presence of comorbidities, SAPS II, pH, the ratio of oxygen arterial pressure to oxygen inspiratory fraction on admission, and, above all, no increase in pH after 1 hour of NIV were closely related to hospital mortality.

CONCLUSIONS

Team expertise in NIV and identification of the risk factors for NIV failure may allow to treat patients with more severe hypercapnic exacerbations of COPD during and improve treatment success rates.

Hypo- and hypercapnia predict mortality in oxygen-dependent chronic obstructive pulmonary disease: a population-based prospective study

BACKGROUND

The prognostic role of the arterial blood gas tension of carbon dioxide (PaCO2) in severe Chronic Obstructive Pulmonary Disease (COPD) remains unknown. The aim of this study was to estimate the association between PaCO2 and mortality in oxygen-dependent COPD.

METHODS

National prospective study of patients starting long-term oxygen therapy (LTOT) for COPD in Sweden between October 1, 2005 and June 30, 2009, with all-cause mortality as endpoint. The association between PaCO2 while breathing air, PaCO2 (air), and mortality was estimated using Cox regression adjusted for age, sex, arterial blood gas tension of oxygen (PaO2), World Health Organization performance status, body mass index, comorbidity, and medications.

RESULTS

Of 2,249 patients included, 1,129 (50%) died during a median 1.1 years (IQR 0.6-2.0 years) of observation. No patient was lost to follow-up. PaCO2 (air) independently predicted adjusted mortality (p < 0.001). The association with mortality was U-shaped, with the lowest mortality at approximately PaCO2 (air) 6.5 kPa and increased mortality at PaCO2 (air) below 5.0 kPa and above 7.0 kPa.

CONCLUSION

In oxygen-dependent COPD, PaCO2 (air) is an independent prognostic factor with a U-shaped association with mortality.

A novel extracorporeal CO(2) removal system: results of a pilot study of hypercapnic respiratory failure in patients with COPD

BACKGROUND

Hypercapnic respiratory failure in patients with COPD frequently requires mechanical ventilatory support. Extracorporeal CO2 removal (ECCO2R) techniques have not been systematically evaluated in these patients.

METHODS

This is a pilot study of a novel ECCO2R device that utilizes a single venous catheter with high CO2 removal rates at low blood flows. Twenty hypercapnic patients with COPD received ECCO2R. Group 1 (n = 7) consisted of patients receiving noninvasive ventilation with a high likelihood of requiring invasive ventilation, group 2 (n = 2) consisted of patients who could not be weaned from noninvasive ventilation, and group 3 (n = 11) consisted of patients on invasive ventilation who had failed attempts to wean.

RESULTS

The device was well tolerated, with complications and rates similar to those seen with central venous catheterization. Blood flow through the system was 430.5 ± 73.7 mL/min, and ECCO2R was 82.5 ± 15.6 mL/min and did not change significantly with time. Invasive ventilation was avoided in all patients in group 1 and both patients in group 2 were weaned; PaCO2 decreased significantly (P < .003) with application of the device from 78.9 ± 16.8 mm Hg to 65.9 ± 11.5 mm Hg. In group 3, three patients were weaned, while the level of invasive ventilatory support was reduced in three patients. One patient in group 3 died due to a retroperitoneal bleed following catheterization.

CONCLUSIONS

This single-catheter, low-flow ECCO2R system provided clinically useful levels of CO2 removal in these patients with COPD. The system appears to be a potentially valuable additional modality for the treatment of hypercapnic respiratory failure.

Comorbidities and mortality in hypercapnic obese under domiciliary noninvasive ventilation

Background

The higher mortality rate in untreated patients with obesity-associated hypoventilation is a strong rationale for long-term noninvasive ventilation (NIV). The impacts of comorbidities, medications and NIV compliance on survival of these patients remain largely unexplored.

Methods

Observational cohort of hypercapnic obese patients initiated on NIV between March 2003 and July 2008. Survival curves were estimated by the Kaplan–Meier method. Anthropometric measurements, pulmonary function, blood gases, nocturnal SpO₂ indices, comorbidities, medications, conditions of NIV initiation and NIV compliance were used as covariates. Univariate and multivariate Cox models allowed to assess predictive factors of mortality.

Results

One hundred and seven patients (56% women), in whom NIV was initiated in acute (36%) or chronic conditions, were followed during 43±14 months. The 1, 2, 3 years survival rates were 99%, 94%, and 89%, respectively. In univariate analysis, death was associated with older age (>61 years), low FEV1 (<66% predicted value), male gender, BMI×time, concomitant COPD, NIV initiation in acute condition, use of inhaled corticosteroids, ß-blockers, nonthiazide diuretics, angiotensin-converting enzyme inhibitors and combination of cardiovascular drugs (one diuretic and at least one other cardiovascular agent). In multivariate analysis, combination of cardiovascular agents was the only factor independently associated with higher risk of death (HR = 5.3; 95% CI 1.18; 23.9). Female gender was associated with lower risk of death.

Conclusion

Cardiovascular comorbidities represent the main factor predicting mortality in patient with obesity-associated hypoventilation treated by NIV. In this population, NIV should be associated with a combination of treatment modalities to reduce cardiovascular risk.

Predictors of weaning after acute respiratory failure

Although weaning predictors have been extensively explored in weaning research, their use is currently under debate. From all the stages of mechanical ventilation, the measurements of weaning predictors have been considered by some authors as imperative in order to progress weaning and initiate a weaning trial. However, this practice is rejected by other authors who considered that these tests are not necessary to perform a weaning trial, based in a meta-analysis study from the American College of Chest Physicians. Among all the weaning predictors, the frequency-to-tidal volume ratio (f/VT) remains the most important predictor of weaning. Other predictors have been defined, but their narrow predictive capacity or the requirement of specific technology, have limited their use. The variability of the results obtained by the efficacy of f/VT is probably explained because in most cases weaning is initiated late, when pre-test probability of weaning success is high. In order to reduce weaning duration, weaning strategies must be performed earlier, when a failed weaning trial probably is poor tolerated and the use of f/VT could have a role. New applications of weaning predictors must be clarified in future research, in order to progress in weaning in the context of new studies. Weaning is still a challenging period during mechanical ventilation.

Non-invasive ventilation in elderly patients with acute hypercapnic respiratory failure: a randomised controlled trial

OBJECTIVE

older patients usually receive less invasive and costly hospital care, even if they meet the criteria for Intensive Care Unit admission or have a 'do not intubate'(DNI) order. The aim of this randomised, controlled trial was to assess the effectiveness of non-invasive mechanical ventilation (NIV) versus the standard medical therapy (SMT) in reducing the need of intubation, improving survival and reducing respiratory distress in very old patients with acute hypercapnic respiratory failure (AHRF).

PARTICIPANTS AND DESIGN

eighty-two patients aged >75 years (mean age 81.3 ± 3.5 years) were randomised to receive NIV or SMT.

SETTINGS

three respiratory units.

MEASUREMENTS

the primary outcome was the rate of meeting the endotracheal intubation (ETI) criteria. Secondary outcomes were the mortality rate, the respiratory rate, dyspnoea score, arterial blood gases.

RESULTS

the rate of meeting the ETI criteria was lower in the NIV group compared with the SMT group (7.3 versus 63.4%, respectively; P < 0.001), as was the mortality rate [(odds ratios) OR = 0.40; 95% CI: 0.19-0.83; P = 0.014]. Twenty-two of 41 SMT patients with DNI orders received NIV as a rescue therapy. The mortality rate in this subgroup was comparable with the NIV group and significantly lower compared with patients receiving ETI (OR = 0.60, 95% CI: 0.18-1.92 versus 4.03, 95% CI: 2.35-6.94, respectively; P = 0.009). Arterial blood gases, respiratory rate and dyspnoea improved significantly faster with NIV than with SMT.

CONCLUSIONS

compared with SMT, NIV decreased the rate of meeting the ETI criteria and the mortality rate of very old patients with AHRF. NIV should be offered as an alternative to patients considered poor candidates for intubation and those with a DNI order.

The effect of carbon dioxide on growth of juvenile Atlantic cod Gadus morhua L

A trial was undertaken to investigate how exposure to graded hypercapnia affected the growth performance of juvenile (15-80 g) Atlantic cod. Juveniles were grown at 20‰ salinity and 10°C for 55 days under three hypercapnic regimes: low (2±0.9 mg L(-1) CO(2), 0.6mm Hg, 1000 μatm), medium (8±0.5 mg L(-1) CO(2), 2.8mm Hg, 3800 μatm) and high CO(2) exposure (18±0.2 mg L(-1) CO(2), 6.3mm Hg, 8500 μatm). All water quality parameters were within the range of what might normally be considered acceptable for good growth, including the CO(2) levels tested. Weight gain, growth rate and condition factor were substantially reduced with increasing CO(2) dosage. The size-specific growth trajectories of fish reared under the medium and high CO(2) treatments were approximately 2.5 and 7.5 times lower (respectively) than that of fish in the low treatment. Size variance and mortality rate was not significantly different amongst treatments, indicating that there was no differential size mortality due the effects of hypercapnia, and the CO(2) levels tested were within the adaptive capacity of the fish. In addition, an analysis was carried out of the test CO(2) concentrations reported in three other long-term hypercapnia experiments using marine fish species. The test concentrations were recalculated from the reported carbonate chemistry conditions, and indicated that the CO(2) concentration effect threshold may have been overestimated in two of these studies. Our study suggests that juvenile Atlantic cod are more susceptible to the chronic effects of environmental hypercapnia than other marine fish examined to date.

Associated factors with non-invasive mechanical ventilation failure in acute hypercapnic respiratory failure

Our aim was to determine associated factors with non-invasive mechanical ventilation (NIMV) failure in acute hypercapnic respiratory failure ninety live patients treated with NIMV for acute hypercapnic respiratory failure were evaluated. While success of NIMV was defined as absence of need of intubation with the patient's discharge from hospital, failure of NIMV was defined as death or need of intubation. The pretreatment pH level was 7.30 in success and 7.28 in failure group (p> 0.05), PaCO(2) was 71.45 mmHg in success and 72.17 mmHg in failure group (p> 0.05). After 1h of NIMV, pH was 7.33 in success and 7.26 in failure group (p= 0.01), PaCO(2) was 65.50 mmHg in success and 73.47 mmHg in failure group (p= 0.02). After 1h of treatment, in success group there was significant increase of pH and decrease of PaCO(2) in contrast to baseline levels, while there was no significant change in failure group. The pretreatment Acute Physiology Assessment and Chronic Health Evaluation (APACHE) II score, serum C-reactive protein level and frequency of associated complication on admission were significantly higher and Glasgow Coma Score was lower in failure group. In conclusion, high APACHE II and C-reactive protein level, low Glasgow Coma Score, associated complication on admission and inadequate response in pH and PaCO(2) after first hour of NIMV are associated factors with NIMV failure.

Predictors of long-term survival in patients with restrictive thoracic disorders and chronic respiratory failure undergoing non-invasive home ventilation

BACKGROUND AND OBJECTIVES

Non-invasive positive pressure ventilation (NPPV) is an established treatment in restrictive thoracic disorders (RTD) with chronic hypercapnic respiratory failure. The aim of this study was to identify predictors of long-term survival for patients on NPPV therapy.

METHODS

In a 10-year retrospective cohort of patients with RTD and chronic hypercapnic respiratory failure, survival and the predictive value of nocturnal and daytime blood gases, lung function and laboratory data measured before initiation of NPPV were assessed. The impact of ventilator settings and daily use of NPPV on survival were also evaluated. Patients were re-admitted every 6 months for follow-up assessment.

RESULTS

The study recruited 77 patients; 18 died during the study period and three ceased NPPV. Respiratory failure caused eight of the nine respiratory deaths (88.9%). One-, 2- and 5-year survival rates were 92.5%, 81.0% and 59.0%, respectively. In univariate analyses, higher night-time PaCO(2), base excess (night- and daytime) and lower Hb at baseline were associated with significantly worse survival (P < 0.05). Multivariate Cox regression analysis revealed night-time PaCO(2) as an independent predictor of survival (P = 0.042). The small differences in daily duration of use of NPPV and ventilator settings were not significantly related to survival. At follow up, significant improvements were observed for blood gases, lung and respiratory muscle function, as well as a decrease in Hb level (P < 0.01 each).

CONCLUSIONS

Base excess, Hb and particularly nocturnal PaCO(2) are relevant prognostic factors for survival in RTD and should be considered in assessing patients receiving NPPV.

Impact of noninvasive home ventilation on long-term survival in chronic hypercapnic COPD: a prospective observational study

AIMS

The long-term benefit from noninvasive ventilation (NIV) in chronic hypercapnic chronic obstructive pulmonary disease (COPD) remains uncertain.

METHODS

Within a prospective observational design, we compared the long-term survival of 140 patients with severe persistent hypercapnic COPD (FEV(1) 28.7 +/- 8.7% predicted; PaCO(2) 60.1 +/- 9.2 mmHg) with (n = 99) or without (n = 41) NIV. End-point was all-cause mortality, determined up to 4 years by Kaplan-Meier analysis. Additionally, Cox's proportional hazards regression and stratification by risk factors was performed. Patients were characterised by anthropometric and functional parameters, comorbidities and medical therapy.

RESULTS

Adherence in patients with NIV was high (88.9%), daily ventilator use being 6.4 +/- 2.6 h/day and inspiratory pressures 21.0 +/- 4.0 cmH(2)O. One- and 2-year survival rates were 87.7% and 71.8%, respectively, in patients with NIV vs. 56.7% and 42.0% in patients without NIV. Survival rates were significantly higher in patients with NIV compared to those without this therapy (p = 0.001; hazard ratio 0.380; 95% confidence interval 0.138-0.606). The difference between groups was still significant after adjustment for differences in baseline characteristics. Moreover, stratification by risk factors revealed beneficial effects, particularly in patients with high base excess (BE; > 8.9 mmol/l), low pH (< 7.41), FEV(1) (< 27.5%) haemoglobin (< 13.8 g/dl) or large hyperinflation (residual volume-to-total lung capacity > 189% predicted) upon inclusion (p < 0.05 each).

CONCLUSION

In patients with severe chronic hypercapnic COPD receiving NIV at high inspiratory pressure levels and showing high adherence to this therapy, long-term survival was significantly higher than in non-ventilated patients. Patients displaying more severe disease according to known risk factors seemed to benefit most from long-term NIV.

Evolution of Patients With Chronic Obstructive Pulmonary Disease, Obesity Hypoventilation Syndrome, or Congestive Heart Failure Undergoing Noninvasive Ventilation in a Respiratory Monitoring Unit

OBJECTIVE

We compared the use of noninvasive ventilation (NIV) for hypercapnic acidosis with hypoxemia in patients with chronic obstructive pulmonary disease (COPD), obesity hypoventilation syndrome (OHS), or congestive heart failure (CHF) in a respiratory medicine monitoring unit. The objective was to evaluate each diagnostic groups response to therapy in terms of clinical course and evolution of blood gases.

PATIENTS AND METHODS

Prospective, 12-month study of 53 patients with hypercapnic acidosis with hypoxemia. Twenty-seven patients had COPD, 17 OHS, and 9 CHF. Severity was assessed based on initial arterial blood gas analysis. Clinical course was studied by blood gas analysis after conventional treatment and after NIV (1-3 hours and 12-24 hours). Mortality was recorded. All patients received bilevel positive airway pressure support in assist-control mode.

RESULTS

No significant differences were observed between mean (SD) initial pH findings in the 3 diagnostic groups: COPD, 7.28 (0.1); OHS, 7.29 (0.09); and CHF, 7.24 (0.07). (nonsignificant differences). After initial conventional treatment, PaCO2 worsened for COPD patients (P = .026) and PaO2 improved for CHF patients (P = .028). After 1 to 3 hours of NIV, pH (P = .002) and PaO2 (P = .041) improved for COPD patients, and pH (P = .03) and PaCO2 (P = .045) improved in OHS patients; no significant changes were observed in CHF patients. After 12 to 24 hours of NIV, the mean pH was 7.36 (0.04) for COPD patients, 7.36 (0.05) for OHS patients, and 7.25 (0.1) for CHF patients (not significant). The mortality rate was 11.1% for COPD, 0% for OHS, and 33.3% for CHS (not significant, P = .076).

CONCLUSIONS

In this group of patients with similar initial arterial blood gas values, response to NIV was seen to be better in OHS and COPD than in CHF. That the start of NIV is usually preceded by a poor response to conventional COPD treatment suggests that delaying NIV should be reconsidered.

Predictors of hospital outcome and intubation in COPD patients admitted to the respiratory ICU for acute hypercapnic respiratory failure

BACKGROUND

Mortality rate, the possible factors affecting mortality and intubation in patients with acute exacerbation of chronic obstructive pulmonary diseases (COPD) and hypercapnic respiratory failure (RF) are yet unclear.

OBJECTIVE

To identify the possible factors affecting mortality and intubation in COPD patients.

DESIGN

A prospective study using data obtained over the first 24h of respiratory intensive care unit (RICU) admission. Consecutive admissions of 656 patients were monitored and 151 of them who had acute exacerbation of COPD and hypercapnic RF were enrolled.

SETTING

University hospital, Department of Chest Diseases, RICU.

RESULTS

Mean age was 65.1 years. The mean APACHE II score was 23.7. Eighty-seven patients (57.6%) received mechanical ventilation (MV) via an endotracheal tube for more than 24 h. Twenty-two patients received non-invasive ventilation (NIV). Fifty patients died (33.1%) in hospital during the study period. The mortality rate was 52.9% in patients in need of MV. In the multivariate analysis, the need for intubation, inadequate metabolic compensation for respiratory acidosis, and low (=bad) Glasgow Coma Score (GCS) were determined as independent factors associated with mortality. The low GCS (OR: 0.61; CI: 0.48-0.78) and high APACHE II score (OR: 1.24; CI: 1.11-1.38) were determined as factors associated with intubation.

CONCLUSION

The most important predictors related to hospital mortality were the need for invasive ventilation and complications to MV. Adequate metabolic compensation for respiratory acidosis at admittance is associated with better survival. A high APACHE II score and loss of consciousness (low GCS) were independent predictors of a need to intubate patients.

The use of noninvasive mechanical ventilation in COPD with severe hypercapnic acidosis

STUDY OBJECTIVES

To compare the effect of noninvasive mechanical ventilation (NIV) in severely acidotic with mildly acidotic patients with acute hypercapnic chronic obstructive lung disease (COPD).

DESIGN

Comparison of NIV in consecutively enrolled patients with acute hypercapnic COPD with mild (pH 7.25-7.35) or severe (pH<7.25) acidosis on time to normalise pH and improve PaCO(2), duration of NIV treatment, length of stay in hospital and survival. Results (meadian (IQR)): Twenty-nine patients had 36 episodes of acute hypercapnic respiratory failure: Seventeen with pH<7.25 and 19 with pH 7.25-7.34. Compared with the mildly acidotic group, the severely acidotic group took a similar length of time for pH to normalise and PaCO(2) improve (12 (6-34) vs 12 (4-28)h, respectively, P=0.42), with similar duration of NIV treatment (60 (35-96) vs 68 (36-48)h, respectively, P=0.25) and hospital length of stay (8 (7-18) vs 9 (5-17) days, respectively, P=0.61). Overall survival was 89%, with 95% in the mild and 82% in the severely acidotic groups.

CONCLUSIONS

Noninvasive ventilation is effective in the treatment of patients with severe acidosis due to acute hypercapnic COPD.

Hypercapnic acidosis and mortality in acute lung injury*

OBJECTIVE

We tested the hypothesis that hypercapnic acidosis is associated with reduced mortality rate in patients with acute lung injury independent of changes in mechanical ventilation.

DESIGN

Secondary analysis of randomized clinical trial data using hypothesis-driven multivariate logistic regression.

SETTING

Randomized, multiple-center trial (n = 861) comparing 12 mL/kg to 6 mL/kg predicted body weight tidal volumes previously published by the National Institutes of Health Acute Respiratory Distress Syndrome (ARDS) Network.

PATIENTS

Acute lung injury patients enrolled in a randomized, multiple-center trial (n = 861).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The adjusted odds ratio and 95% confidence intervals (CI) for 28-day mortality rate associated with hypercapnic acidosis defined as day 1 pH <7.35 and Pa(CO2) >45 mm Hg were 0.14 (95% CI 0.03-0.70, p = .016) in the 12 mL/kg predicted body weight tidal volume group and 1.18 (95% CI 0.59-2.35, p = .639) in the 6 mL/kg predicted body weight tidal volume group. Other definitions of hypercapnic acidosis spanning a range of magnitudes suggest a dose-response association between hypercapnic acidosis and 28-day mortality in the 12 mL/kg predicted body weight tidal volume group. None of our definitions of hypercapnic acidosis were associated with reduction in 28-day mortality in the 6 mL/kg predicted body weight tidal volume group.

CONCLUSIONS

Hypercapnic acidosis was associated with reduced 28-day mortality in the 12 mL/kg predicted body weight tidal volume group after controlling for comorbidities and severity of lung injury. These results are consistent with a protective effect of hypercapnic acidosis against ventilator-associated lung injury that was not found when the further ongoing injury was reduced by 6 mL/kg predicted body weight tidal volumes.

Effects of acute on chronic respiratory failure on hypercapnia and 3-month survival

BACKGROUND

There is a lack of information on respiratory function and mechanics after COPD exacerbations.

STUDY OBJECTIVES

To find their role in short-term survival and occurrence of chronic hypercapnia after these events.

PATIENTS AND INTERVENTIONS

Seventy-three COPD patients recovering from a recent severe exacerbation underwent evaluation of breathing pattern, breathing mechanics, lung function, and arterial blood gas levels at the time of discharge from a respiratory ICU (RICU).

RESULTS

The 3-month mortality rate after RICU discharge was 11%. The percent of ideal body weight (%IBW) [R = 6.04; p = 0.01] and occlusion pressure (R = 5.41; p = 0.02) provided significant distinction between deceased patients and survivors; the final discriminant equation showed that %IBW was able to predict patient death or survival with an accuracy of 90%. With decreasing order of power, the ratio of inspiratory time to total breathing cycle time (Ti/Ttot) [R = 8.87; p = 0.003], pressure-time product of the inspiratory muscles (R = 7.12; p = 0.009), maximal esophageal pressure (R = 6.00; p = 0.01), esophageal pressure (R = 5.50; p = 0.02), Pa(O2)/fraction of inspired oxygen (R = 4.72; p = 0.03), and pressure time index (PTI) [R = 4.57; p = 0.03] provided a significant distinction between hypercapnia and normocapnia at discharge. The discriminant equation, including Ti/Ttot and PTI, could correctly separate hypercapnic or normocapnic patients with an accuracy of 76%.

CONCLUSIONS

In COPD patients who are recovering from a severe exacerbation, hypercapnia is strongly related to inspiratory muscle work, strength, and breathing pattern; and only body weight predicts short-term survival.

Survival of chronic hypercapnic COPD patients is predicted by smoking habits, comorbidity, and hypoxemia

STUDY OBJECTIVES

Chronic hypercapnia in patients with COPD has been associated with a poor prognosis. We hypothesized that, within this group of chronic hypercapnic COPD patients, factors that could mediate this hypercapnia, such as decreased maximum inspiratory mouth pressure (P(I(max))), decreased maximum expiratory mouth pressure (P(E(max))), and low hypercapnic ventilatory response (HCVR), could be related to survival. Other parameters, such as arterial blood gas values, airway obstruction (FEV1), body mass index (BMI), current smoking status, and the presence of comorbidity were studied as well.

METHODS

A cohort of 47 chronic hypercapnic COPD patients recruited for short-term trials (1 to 3 weeks) in our institute was followed up for 3.8 years on average. Survival was analyzed using a Cox proportional hazards model. The risk factors considered were analyzed, optimally adjusted for age and gender.

RESULTS

At the time of analysis 18 patients (10 male) were deceased. After adjusting for age and gender, P(I(max)), P(E(max)), and HCVR were not correlated with survival within this hypercapnic group. Current smoking (hazard ratio [HR], 7.0; 95% confidence interval [CI], 1.4 to 35.3) and the presence of comorbidity (HR, 5.5; 95% CI, 1.7 to 18.7) were associated with increased mortality. A higher Pa(O2) affected survival positively (HR, 0.6 per 5 mm Hg; 95% CI, 0.4 to 1.0). Pa(CO2) tended to be lower in survivors, but this did not reach statistical significance (HR, 2.0 per 5 mm Hg; 95% CI, 0.9 to 4.3). FEV1 and BMI were not significantly related with survival in hypercapnic COPD patients.

CONCLUSION

In patients with chronic hypercapnia, only smoking status, the presence of comorbidity, and Pa(O2) level are significantly associated with survival. Airway obstruction, age, and BMI are known to be predictors of survival in COPD patients in general. However, these parameters do not seem to significantly affect survival once chronic hypercapnia has developed.

Readmission rates and life threatening events in COPD survivors treated with non-invasive ventilation for acute hypercapnic respiratory failure

BACKGROUND

Non-invasive ventilation (NIV) has been shown to reduce intubation and in-hospital mortality in patients with chronic obstructive pulmonary disease (COPD) and acute hypercapnic respiratory failure (AHRF). However, little information exists on the outcomes following discharge. A study was undertaken to examine the rates of readmission, recurrent AHRF, and death following discharge and the risk factors associated with them.

METHODS

A cohort of COPD patients with AHRF who survived after treatment with NIV in a respiratory high dependency unit was prospectively followed from July 2001 to October 2002. The times to readmission, first recurrent AHRF, and death were recorded and analysed against potential risk factors collected during the index admission.

RESULTS

One hundred and ten patients (87 men) of mean (SD) age 73.2 (7.6) years survived AHRF after NIV during the study period. One year after discharge 79.9% had been readmitted, 63.3% had another life threatening event, and 49.1% had died. Survivors spent a median of 12% of the subsequent year in hospital. The number of days in hospital in the previous year (p = 0.016) and a low Katz score (p = 0.018) predicted early readmission; home oxygen use (p = 0.002), APACHE II score (p = 0.006), and a lower body mass index (p = 0.041) predicted early recurrent AHRF or death; the MRC dyspnoea score (p<0.001) predicted early death.

CONCLUSIONS

COPD patients with AHRF who survive following treatment with NIV have a high risk of readmission and life threatening events. Further studies are urgently needed to devise strategies to reduce readmission and life threatening events in this group of patients.

Hypoplasia of the Small Pulmonary Arteries in Hypoplastic Left Heart Syndrome With Restrictive Atrial Septal Defect

BACKGROUND

Restrictive atrial septal defect (ASD) (including intact atrial septum [IAS]) has been reported to be a risk factor that negatively impacts survival in hypoplastic left heart syndrome (HLHS). Although lymphangiectasia and "arterialization" of the veins of the lung in HLHS with restrictive ASD have been reported, they cannot fully explain the high mortality. We have introduced a new method of evaluating the development of the pulmonary vasculature in histological sections and used it to assess patients' lungs. We tested the hypothesis that the small pulmonary arteries (SPA), which are pulmonary arteries in a histological section whose radii are approximately 25 microm to 250 microm, in HLHS with restrictive ASD are hypoplastic, but that the alveoli are not, to elucidate the mechanism underlying the poor outcome of these patients.

METHODS AND RESULTS

Fourteen HLHS patients between 1 day and 40 days of age were studied. In 8 cases, the ASD was restrictive [R(+) group], and in the other 6 cases it was not [R(-) group]. Specimens from 12 autopsies of cases with no congenital heart or pulmonary disease were examined as a control group (C group). As a novel histological parameter, we assessed the size of SPA in relation to the size of accompanying bronchioles to identify SPA underdevelopment. To evaluate the development of alveoli and interstitial tissue, radial alveolar counts (RAC), which reflect alveolar maturity and complexity, were also performed. Statistical comparisons between groups were made by analysis of covariance with age as a covariant factor. When the radius of the accompanying bronchiole was 100 microm, the radius of the SPA was 34.0+/-10.8 microm in the R(+) group, and significantly lower than the 46.6+/-8.5 microm in R(-) group (P=0.0022) and 70.5+/-8.4 microm in the C group (P<0.0001). The RAC was in 3.5+/-0.9 in the R(+) group, 3.4+/-0.6 in the R(-) group, and 3.7+/-0.9 in the C group (no significant differences between groups).

CONCLUSIONS

The SPA in HLHS with restrictive ASD were underdeveloped compared with the SPA in HLHS with nonrestrictive ASD and the controls, but their alveoli were not hypoplastic. Based on these results, it is speculated that SPA hypoplasia may be responsible for the poor outcome of HLHS with restrictive ASD.

Noninvasive ventilation in patients with acute hypercapnic exacerbation of chronic obstructive pulmonary disease who refused endotracheal intubation

OBJECTIVE

To determine the long-term outcome of noninvasive ventilation in chronic obstructive pulmonary disease patients who refused intubation for acute hypercapnic respiratory failure.

DESIGN

Prospective, observational study.

SETTING

Noninvasive ventilation unit in an acute regional hospital in Hong Kong.

METHODS

The study recruited 37 chronic obstructive pulmonary disease patients who had the do-not-intubate code and developed acute hypercapnic respiratory failure. They were offered noninvasive ventilation, and their long-term outcomes were followed. Survival and event-free survival (an event is death or recurrent acute hypercapnic respiratory failure) were analyzed by survival analysis. Their disease profile and outcome were compared with another 43 chronic obstructive pulmonary disease patients without the do-not-intubate codes, who had acute hypercapnic respiratory failure and received noninvasive ventilation during the study period (usual care group).

RESULTS

Patients in the do-not-intubate group were significantly older (p =.029), had worse dyspnea score (p <.001), worse Katz Activities of Daily Living score (p <.001), worse comorbidity score (p =.024), worse Acute Physiology and Chronic Health Evaluation II score (p =.032), lower hemoglobin (p =.001), and longer stay in the hospital during the past year (p =.001) than patients who received usual care. In the do-not-intubate group, the median survival was 179 days, and 1-yr actuarial survival was 29.7%; in the usual care group, the median survival was not reached during follow-up, and 1-yr actuarial survival was 65.1% (p <.0001). In the do-not-intubate group, the median event-free survival was 102 days, and 1-yr event-free survival was 16.2%; in the usual care group, median event-free survival was 292 days, and 1-yr event-free survival was 46.5% (p =.0004).

CONCLUSIONS

A 1-yr survival of about 30% was recorded in chronic obstructive pulmonary disease patients with the do-not-intubate code who developed acute hypercapnic respiratory failure requiring noninvasive ventilation. The majority of survivors developed another life-threatening event in the following year. Information generated from this study is important to physicians and chronic obstructive pulmonary disease patients when they are considering using noninvasive ventilation as a last resort.

Mortality after carotid body denervation in rats

Carotid body denervation (CBD) in neonatal goats and piglets results in minimal irregular breathing and no fatalities. Redundancy and/or plasticity of peripheral chemosensitivity and a relatively mature ventilatory control system at birth may contribute to the paucity of CBD effects in these species. In the present study, we tested the hypothesis that CBD mortality would be greater in neonates of a less mature species such as the rat. We found that the mortality in rats denervated at 2-3 and 7-8 days of age was significantly higher (P < 0.05) than in sham-CBD rats. In all surviving rats, pulmonary ventilation during hypoxia was lower in CBD than in sham operated rats 2 days after denervation. In surviving rats denervated during the 7th and 8th postnatal days, there was also reduced weight gain and pulmonary ventilation during eupnea, including apneas up to 20 s in duration. However, the effects of CBD were compensated within 3 wk after denervation. Local injections of NaCN indicated that aortic chemoreceptors might have been one of the sites of recovery of peripheral chemosensitivity. We concluded that CBD has higher mortality in newborn rats than in other mammals, possibly because of the relative immaturity of these animals at birth. Nonetheless, in survivors there was enough redundancy and plasticity in the control of breathing to eventually compensate for the consequences of CBD.

Hypercapnic respiratory failure in COPD patients: response to therapy

INTRODUCTION

The clinical course of patients with acute exacerbations of underlying COPD presenting with hypercapnic respiratory failure was reviewed.

METHODS

This was a retrospective review of 138 episodes of hypercapnic respiratory failure (PaCO(2) > or = 50 mm Hg and pH < or = 7.35). Patients were admitted to the West Los Angeles VAMC Medical Intensive Care Unit between 1990 and 1994.

RESULTS

Of the 138 hypercapnic episodes, 74 (54%) required intubation. Comparison was made with the 64 cases in which patients responded to medical therapy. Patients requiring intubation had a greater severity of illness, with a higher APACHE II (Acute Physiology and Chronic Health Evaluation II) score (18 +/- 5 vs 16 +/- 4; p < 0.01), higher WBC, higher serum BUN, and greater acidosis (pH, 7.26 +/- 0.07 vs 7.28 +/- 0.06; p = 0.08). Those with the most severe acidosis (pH < 7.20) had the highest intubation rate (70%) and shortest time to intubation (2 +/- 2 h), and they required the longest period of time to respond to medical therapy (69 +/- 60 h). With an initial pH of < 7.25, there was a consistently higher intubation rate. Conversely, those with an initial pH of 7.31 to 7. 35 were less likely to be intubated (45%), had a longer time to intubation (13 +/- 18 h), and had a more rapid response to medical therapy (30 +/- 18 h). Of those patients requiring intubation, most (78%) were intubated within 8 h of presentation, and the vast majority (93%) by 24 h. Of those patients responding to medical therapy, half (52%) recovered within 24 h and the vast majority (92%) recovered within 72 h.

CONCLUSIONS

This study provides a better characterization of the response to therapy of COPD patients with hypercapnic respiratory failure. This should be useful in limiting or omitting medical therapy in high-risk patients, thereby avoiding delays in intubation as well as providing a framework for continued therapy in those more likely to improve.

Complications and mortality associated with anesthesia in dogs and cats

The complications and mortality associated with anesthesia of dogs and cats in a university teaching hospital were determined. During one year, 2,556 dogs and 683 cats were anesthetized by the anesthesia service. Hypotension occurred in 179 (7%) dogs and 58 (8.5%) cats. Cardiac dysrhythmias occurred in 64 (2.5%) dogs and 12 (1.8%) cats. Transfusions were required in 31 (1.2%) dogs. Hypercapnea occurred in 33 (1.3%) dogs and one (less than 1%) cat. Hypoxemia occurred in 14 (0.5%) dogs. Anesthetic complications, as defined, occurred in 12.0% of dogs and 10.5% of cats, while deaths associated with the perianesthetic period occurred in 0.43% of dogs and 0.43% of cats.

Improvements in lung function, exercise, and quality of life in hypercapnic COPD patients after lung volume reduction surgery

STUDY OBJECTIVE

To determine the impact of preoperative resting hypercapnia on patient outcome after bilateral lung volume reduction surgery (LVRS).

METHODS

We prospectively examined morbidity, mortality, quality of life (QOL), and physiologic outcome, including spirometry, gas exchange, and exercise performance in 15 patients with severe emphysema and a resting PaCO2 of > 45 mm Hg (group 1), and compared the results with those from 31 patients with a PaCO2 of < 45 mm Hg (group 2).

RESULTS

All preoperative physiologic and QOL indices were more impaired in the hypercapnic patients than in the eucapnic patients. The hypercapnic patients exhibited a lower preoperative FEV1, a lower diffusing capacity of the lung for carbon monoxide, a lower ratio of PaO2 to the fraction of inspired oxygen, a lower 6-min walk distance, and higher oxygen requirements. However, after surgery both groups exhibited improvements in FVC (group 1, p < 0.01; group 2, p < 0.001), FEV1 (group 1, p=0.04; group 2, p < 0.001), total lung capacity (TLC; group 1, p=0.02; group 2, p < 0.001), residual volume (RV; group 1, p=0.002; group 2, p < 0.001), RV/TLC ratio (group 1, p=0.03; group 2, p < 0.001), PaCO2 (group 1, p=0.002; group 2, p=0.02), 6-min walk distance (group 1, p=0.005; group 2, p < 0.001), oxygen consumption at peak exercise (group 1, p=0.02; group 2, p=0.02), total exercise time (group 1, p=0.02; group 2, p=0.02), and the perceived overall QOL scores (group 1, p=0.001; group 2, p < 0.001). However, because the magnitude of improvement was similar in both groups, and the hypercapnic group was more impaired, the spirometry, lung volumes, and 6-min walk distance remained significantly lower post-LVRS in the hypercapnic patients. There was no difference in mortality between the groups (p=0.9).

CONCLUSIONS

Patients with moderate to severe resting hypercapnia exhibit significant improvements in spirometry, gas exchange, perceived QOL, and exercise performance after bilateral LVRS. The maximal achievable improvements in postoperative lung function are related to preoperative level of function; however, the magnitude of improvement can be expected to be similar to patients with lower resting PaCO2 levels. Patients should not be excluded from LVRS based solely on the presence of resting hypercapnia. The long-term benefit of LVRS in hypercapnic patient remains to be determined.

Extreme hypercapnia is not a long-term prognostic factor after near-fatal asthma: a 12-year follow-up study

QUESTION OF THE STUDY

Some patients experiencing near-fatal asthma present with extreme hypercapnia (PaCO2 > or = 100 mm Hg), whereas others do not. The influence of this factor on short- and long-term outcome and quality of life in these patients is still unknown.

PATIENTS AND METHODS

A series of 39 consecutive patients who had had an episode of near-fatal asthma between 1978 and 1992 were followed up. Long-term outcome and quality of life of the 12 patients who had experienced extreme hypercapnia were compared with those of the 27 patients who had not.

RESULTS

Four patients died, but only 1 from asthma. Three patients were lost to follow-up. The remaining 32 patients had a median observation period of 12.7 years. The hypercapnic patients did not significantly differ from the others in past asthma history, subsequent hospitalizations, medication needs, pulmonary function tests, quality of life and impairment/disability. In the event of subsequent near-fatal asthma attacks, they tended to present with hypercapnia levels similar to those observed during the first episode.

DISCUSSION

Extreme hypercapnia in near-fatal asthma tended to recur, but is not an aggravating long-term prognostic factor. Targeted surveillance of these high-risk patients should make it possible to reduce relapses and death rates from asthma.

[Epidemiology and diagnosis of intermittent self-ventilation]

The purpose of the lung is intrapulmonary gas exchange. The circulatory system delivers the respiratory gases to the tissue. The ventilatory pump however is responsible for the circulation of air between the lungs and the ambient atmosphere. Due to better diffusing capabilities, hypercapnia always is a result of pump failure and little dependent on the lung. Ventilatory failure, either compensated with an increased demand on the muscles or decompensated with an additional increase in pCO2, should be separated from lung failure where primarily oxygen exchange is involved. Decompensated hypercapnic ventilatory failure is then the indication for intermittent mechanical ventilation. The pCO2, either arterial or transcutaneously registered together with the noninvasive evaluation of the mouth occlusion pressures during tidal breathing and during a maximal inspiratory effort, define well the severity of ventilatory failure. In acute on chronic ventilatory failure, noninvasive mechanical ventilation in three randomised and controlled studies resulted in a better survival compared to intubation. To fulfil certain weaning criteria is no longer required in difficult to wean patients, as a transfer from invasive to noninvasive mechanical ventilation can be performed if only cooperativity is preserved together with a minimal capacity of spontaneous breathing. Weaning will thereafter occur by progressive relief from intermittent noninvasive ventilation. 2300 difficult to wean patients in Germany should profit from this approach. Chronic ventilatory failure as a result of neuromuscular disease or scoliosis of the thoracic spine are the classical indications. COPD and myasthenia gravis are under discussion as indications for intermittent mechanical ventilation with an increasing tendency to ventilate. Epidemiological data however can only be roughly estimated due to the heterogeneity of indication and selection of the patients.

Reversible hypercapnia in chronic obstructive pulmonary disease: a distinct pattern of respiratory failure with a favorable prognosis

PURPOSE

Hypercapnia is regarded as a poor prognostic indicator in chronic obstructive pulmonary disease (COPD), but many patients hospitalized with hypercapnia associated with an acute exacerbation of COPD revert to normocapnia during recovery. We wished to determine if this reversible hypercapnia represents a distinct pattern of respiratory failure in COPD, or simply a stage in the progression to chronic hypercapnia. We therefore compared the long-term clinical progression and survival of COPD patients with reversible hypercapnic respiratory failure (defined as type 2.1) to those with normocapnic (PaCO2 < 50 mm Hg; type 1) and also to those patients with chronic hypercapnic (PaCO2 > 50 mm Hg) respiratory failure (defined as type 2.2).

PATIENTS AND METHODS

We prospectively followed for 5 years a cohort of 85 patients who had been admitted as emergencies during a 1-year period to the respiratory unit of a University teaching hospital with an exacerbation of COPD complicated by respiratory failure (PaO2 < 60 mm Hg). The main long-term outcome measures were survival and blood gas changes.

RESULTS

Sixty-eight (80%) patients survived the initial admission, and 17 (27%) survived 5 years. PaCO2 rose substantially more during exacerbations in type 2.1 patients (mean 15.8 mm Hg), compared with type 2.2 (mean 6.8 mm Hg) and type 1 patients (mean 1.5 mm Hg). We analyzed 149 subsequent admissions among the survivors over the following 5 years. Type 2.1 patients had a better 5-year survival (28%) than type 2.2 (11% survival; P < 0.05), and similar to type 1 patients (33% 5-year survival). Only 24% of reversible hypercapnic patients developed chronic hypercapnia during long-term followup.

CONCLUSIONS

The data support reversible hypercapnia being a distinct manifestation of respiratory failure in COPD, with a similar prognosis to that of normocapnic respiratory failure.

Treatment of severe exacerbation of chronic obstructive pulmonary disease with mask-applied continuous positive airway pressure

The efficacy of mask-applied continuous positive airway pressure (CPAP) in the treatment of patients with acute severe exacerbations of chronic obstructive pulmonary disease (COPD) was examined. Ten patients with severe exacerbation of COPD who had deteriorated during conventional therapy were treated with face-mask delivered CPAP (+5 cmH2O; Downs Vital signs Inc., New Jersey, USA) instead of tracheal intubation and mechanical ventilation. The patients that were selected required mental alertness, intact upper airway reflexes, the clinical signs of dynamic hyperinflation and a positive end-expiratory pressure auto-(PEEP) manifested as expiratory wheeze and grunting. Nine out of 10 patients responded promptly to mask-CPAP with less distress, better oxygenation, lower respiratory and pulse rates. There was no significant change in arterial carbon dioxide tension with mask-CPAP treatment. One patient deteriorated on mask-CPAP and required intubation and mechanical ventilation. Three patients died (none of these patients died during the acute period of exacerbation). It was concluded that Mask-CPAP may be an alternative to mechanical ventilation in the treatment of selected patients with severe hypercapnic exacerbations of COPD.

Modification of oxygen tolerance in rats by adaptation to combined hypoxia and hypercapnia

Tolerance to 100% O2 or to O2 with 60 torr PICO2 (O2-CO2) was determined at pressures of 1.0-4.0 atm abs in normal rats and in rats adapted to combined hypoxia and hypercapnia (HHA) before O2 or O2-CO2 exposure. Results were compared with previous studies of tolerance to O2 or O2-CO2 after adaptation to hypoxia or hypercapnia alone. Both the positive effect on pulmonary O2 tolerance and the negative effect on CNS O2 tolerance found in hypoxia-adapted rats were reduced or eliminated in HHA rats. The increased CNS tolerance to O2-CO2 found in hypercapnia-adapted rats was also reduced in HHA rats. The observation that some of the O2 tolerance modifications associated with adaptation to hypoxia or hypercapnia were reduced or eliminated by adaptation to both stresses concurrently may be because physiologic responses to chronic hypoxia and chronic hypercapnia are opposite in some ways. Results of the present and previous related studies indicate that physiologic adaptations to chronic alterations in the oxygen and acid-base environments have prominent influences on O2 tolerance over a range of useful pressures.

Nasal mechanical ventilation for hypercapnic respiratory failure in chronic obstructive pulmonary disease: determinants of success and failure

OBJECTIVES

To evaluate the efficacy of nasal mechanical ventilation in patients with chronic obstructive pulmonary disease and hypercapnic respiratory failure and to identify predictors of success or failure of nasal mechanical ventilation.

DESIGN

Prospective case series.

SETTING

Medical intensive care unit in Veterans Administration Medical Center.

PATIENTS

Twelve chronic obstructive pulmonary disease patients treated during 14 episodes of hypercapnic respiratory failure.

INTERVENTIONS

Nasal mechanical ventilation in addition to conventional therapy to treat hypercapnic respiratory failure. Patients underwent nasal mechanical ventilation for at least 30 mins, or longer if the therapy was tolerated. Responses to therapy and arterial blood gases were monitored.

MEASUREMENTS AND MAIN RESULTS

Half of the episodes were successfully treated with nasal mechanical ventilation. There were no differences in age, prior pulmonary function, baseline arterial blood gases, admission arterial blood gases, or respiratory rate between those patients successfully treated and those patients who failed nasal mechanical ventilation. Unsuccessfully treated patients appeared to have a greater severity of illness than successfully treated patients, as indicated by a higher Acute Physiology and Chronic Health Evaluation II score (mean 21 +/- 4 [SD] vs. 15 +/- 4; p = .02). Unsuccessfully treated patients were edentulous, had pneumonia or excess secretions, and had pursed-lip breathing, factors that prevented adequate mouth seal and contributed to greater mouth leaks than in successfully treated patients (the mean volume of the mouth leak was 314 +/- 107 vs. 100 +/- 70 mL; p < .01). Successfully treated patients were able to adapt more rapidly to the nasal mask and ventilator, with greater and more rapid reduction in PaCO2, correction of pH, and reduction in respiratory rate.

CONCLUSIONS

Patients who failed nasal mechanical ventilation appeared to have a greater severity of illness; they were unable to minimize the amount of mouth leak (because of lack of teeth, secretions, or breathing pattern) and were unable to coordinate with the ventilator. These features may allow identification of poor candidates for nasal mechanical ventilation, avoiding unnecessary delays in endotracheal intubation and mechanical ventilation.

Low volume ventilation with permissive hypercapnia in the Adult Respiratory Distress Syndrome

Many animal studies have demonstrated that mechanical ventilation with high peak inspiratory pressures (PIP) can result in a form of acute lung injury closely resembling ARDS, ie characterised by hyaline membranes, granulocyte infiltration, increased pulmonary and systemic vascular permeability, and eventually proliferation of fibroblasts and type II pneumocytes. These studies have led to a concern that, in some patients, orthodox ventilatory management in severe ARDS may result in additional lung injury and, possibly, remote organ dysfunction. Mortality may be increased as a consequence. In an attempt to avoid such ventilator-induced lung injury in severe ARDS, several modifications of ventilatory management have been evaluated. We have previously reported the technique of low volume pressure limited ventilation with permissive hypercapnia, using tidal volumes of 5-7 ml/kg and allowing the PaCO 2 to rise substantially (maximum PaCO 2 17.2 kPa [129 mmHg]), mean maximum 8.3 kPa [62 mmHg]). In an uncontrolled study the mortality was significantly lower than that predicted by Apache II (16% vs 39.6%, p less than 0.01). Acute hypercapnia can cause many physiological disturbances but most of these appear to be due to the resulting intracellular acidosis and should not occur in hypercapnia of gradual onset, allowing the intracellular pH to be normalised. The time scales for compensation of intracellular and extracellular acidosis are markedly different. However, even severe acute hypercapnia appears to be remarkably well tolerated. Several clinical studies suggest that the avoidance of high PIP may reduce mortality in ARDS, but a randomised trial will be required to establish whether pressure limitation and permissive hypercapnia do improve outcome.

[Experimental study of the antihypoxic properties of ibuprofen and other nonsteroidal anti-inflammatory preparations]

The antihypoxic properties of ibuprofen, diclofenac sodium, acetylsalicylic acid and phenylbutazone have been studied. Ibuprofen significantly increases survival of mice in the model of hypoxic hypoxia with hypercapnia. In addition, ibuprofen and diclofenac sodium possess antihypoxic protective activity in the models of circulatory and anoxic hypoxia in rats.

[Characteristics of the antihypoxic properties of 3-hydroxypyridine-class antioxidants]

It was found during experiments using three models of hypoxia (hypobaric, normobaric, hemic) in mice that derivatives of 3-hydroxypyridine possess an antihypoxic effect. They are as active as sodium hydroxybutyrate but less active than gutimine. A clear-cut dependence of the antihypoxic activity on the radical character in the 2nd position of 3 hydroxypyridine was revealed. The presence of a hydroxy group in the 3rd position of pyridine ring was shown to be very important for the antihypoxic properties. The data suggesting different degrees of involvement of GABA and benzodiazepine receptors in realization of the antihypoxic effect were obtained.