Quantitative tracheal bacteriologic and cytologic studies in patients with long-term tracheostomies

Microbiological profiles of tracheostomy patients: a single-center experience

Background

This study compared the prevalence of common microorganisms in obstructed and non-obstructed cases across the four quarters on the first post-tracheostomy year.

Methods

A retrospective chart review of the microbiological profiles of all adult patients who underwent a tracheostomy was conducted between June 2015 and September 2019 at our hospital. Based on the tracheostomy indications, patients were allocated to obstructed or non-obstructed group. Any patient with at least one positive sample was followed up quarterly for a year. The first culture result obtained was recorded at least one month following the last antibiotic dose in each quarter.

Results

Out of the 65 tracheal aspirate results obtained from 58 patients (mean age, 57.5±16.48 years), the most common procedure and indications were surgical tracheostomy (72.4%) and non-obstructed causes (74.1%), respectively. Moreover, 47.7% of the culture results indicated Pseudomonas aeruginosa, which showed significantly different proportions across the quarters (p=0.006). Among obstructed patients, P. aeruginosa was the most common (35%), followed by methicillin-resistant Staphylococcus aureus (MRSA; 23.5%).

Conclusions

The most common post-tracheostomy microorganism was P. aeruginosa. MRSA showed a strong association with tracheostomy for obstructive indications.

Risk factors for respiratory tract bacterial colonization in adults with neuromuscular or neurological disorders and chronic tracheostomy

The aim of this study was to describe the endotracheal respiratory flora in a population of adults suffering from neuromuscular or neurological disorders requiring a long-term tracheostomy and to identify risk factors for colonization. We conducted a prospective and single-center observational study among patients with chronic tracheostomy admitted for planned respiratory assessment between February 2015 and December 2016. Data were collected from patient interview and medical charts with a standardized questionnaire. A tracheal aspiration was performed for each patient. Humidifiers were analysed for bacteriological contamination. Overall 77 tracheal aspirates (TA) were obtained from patients included. Pathogenic bacteria were found in 90% of cases (69/77) with a majority of Pseudomonas aeruginosa (32/77, 41%), Staphylococcus aureus (34/77, 44%) and Serratia marcesens. (22/79, 38%) Amoxicillin + Clavulanic-acid and Cefotaxime were adapted for respectively in only 28% and 35% of the subjects due to the natural resistance of organisms. No pathogenic bacteria were isolated from humidifier samples. Risk factors significantly associated with P. aeruginosa colonization were residence in a medical-care home (p = 0.01, OR = 3.8 [1.1; 15.1]) and the presence of a cuff (p = 0.003, OR = 4.4 [1.1; 20.6]). Significant quantities of pathogenic bacteria are frequently isolated from TA of tracheostomised patients in the absence of infection. The frequent resistance of these pathogens to Amoxicillin + Clavulanic-acid precludes the use of this antibiotic in the empiric treatment of pneumonia in this population.

Tracheostomy in children: Epidemiology and clinical outcomes

BACKGROUND

Tracheotomy is performed in children for a variety of indications, but can place them at increased risk of lower airway infection with pathogenic organisms. While prior studies have identified Pseudomonas aeruginosa and Staphylococcus aureus as the most common lower airway pathogens in children with tracheostomies, little is known about the clinical implications of chronic growth of pathogens.

METHODS

The North Carolina Children's Airway Center database was utilized to identify all pediatric patients with tracheostomy from 2007 to 2012; these data were cross-referenced to a microbiology database of all tracheostomy cultures. Data on hospitalizations, intensive care unit admissions, and length-of-stay were abstracted from the medical record and analyzed using multivariate methods.

RESULTS

We identified 185 children with tracheostomy, of whom chronic bacterial growth status could be defined in 69. P aeruginosa was a common pathogen isolated from tracheostomy cultures, with 49% (91/185) of patients growing this organism at least once. P aeruginosa combined with other gram-negative rods were isolated in 63% (116/185) of subjects at least once. Those who chronically grew gram-negative rods had significantly more hospitalizations, longer total lengths-of-stay, and longer intensive care unit lengths-of-stay than those who did not. These differences remained significant when data were normalized to account for number of available cultures.

CONCLUSION

These data suggest that clinical outcomes may be worse in children with tracheostomies who chronically grow gram-negative rods. Our findings may help guide clinicians in managing children with tracheostomies, though further studies are needed to establish best practice guidelines in these patients.

Microbiology of Tracheal Secretions: What to Expect with Children and Adolescents with Tracheostomies

Introduction  People with tracheostomies exhibit a higher risk of colonization of the lower respiratory tract, acute tracheitis and pneumonia. Despite this, the culture of tracheal secretions is not a routine in most hospitals, and sometimes empiric therapy is based on personal experience, which is not an ideal situation.

Objective  To recognize the pathogens present in the tracheal secretions collected from people up to 18 years old with tracheostomies.

Methods  Prospective evaluation of patients under the age of 18 of a tertiary care hospital. A standardized questionnaire was completed, and tracheal secretion aspirates were sent for microbiological cultures and antibiograms.

Results  Twenty patients under 18 years of age were evaluated, 65% of whom were male. The microbiological culture was positive in 90% of the patients, and the most common microorganisms found were Pseudomonas aeruginosa (55.5%) and Staphylococcus aureus (27.7%).

Discussion  Tracheostomized children and adolescents have respiratory tracts colonized by pathogens, the most common of which is Pseudomonas aeruginosa . These patients must undergo tracheal secretion cultures, whether they present symptoms or not, to determine if there is a correlation between the colonization and the infections. This finding could guide the adequate treatment, avoiding the inappropriate use of antibiotics and indicating the better therapy in cases of laryngeal reconstruction.

Conclusion  In this sample, the culture of tracheal secretions was mainly positive, and the most common agent was P. aeruginosa . We suggest the routine access to Brazilian children and adolescents tracheal secretion cultures, which could help to make a profile of these children and guide the use of antibiotics.

Surveillance tracheal aspirate cultures do not reliably predict bacteria cultured at the time of an acute respiratory infection in children with tracheostomy tubes

BACKGROUND

The aim of this study was to characterize the practice of routinely obtaining tracheal aspirate cultures in children with tracheostomy tubes and to analyze the appropriateness of using this information to guide antibiotic selection for treatment of subsequent lower respiratory infections.

METHODS

Pediatric otolaryngologists and pulmonologists were surveyed regarding surveillance culture practices. Records of children with tracheostomy tubes from January 1, 2003, through December 31, 2007, were reviewed. Consecutive cultures were compared for similarity of bacteria and antibiotic sensitivity when a clinic culture preceded a culture from when the child was ill and received antibiotics and when a hospital culture preceded a hospital culture from a separate hospitalization.

RESULTS

Seventy-nine of 146 pulmonologists and five of 33 otolaryngologists obtained routine surveillance tracheal aspirate cultures (P < .001); 97% of pulmonologists used these cultures to guide subsequent empiric therapy. There were 36 of 170 children with one or more eligible pairs of cultures. Nearly all children had a change in flora in their tracheal cultures. Limiting empiric antibiotic choices to those that would cover microbes isolated in the previous culture likely would not have been effective in covering one or more microbes isolated in the second culture in 56% of pairs with the first culture from hospitalization vs 30% with the first culture from an outpatient setting (P = .15).

CONCLUSIONS

This study demonstrated that there are significant changes in bacteria or antibiotic sensitivity between consecutive tracheal cultures in children with tracheostomy tubes. Use of prior tracheal cultures from these children was of limited value for choosing empiric antibiotic therapy in treating acute lower respiratory exacerbations. Surveillance cultures, thus, are an unnecessary burden and expense of care.

Tracheobronchitis in the Intensive Care Unit

Tracheobronchitis can be broadly defined as inflammation of the airways between the larynx and the bronchioles. Clinically, this syndrome is recognized by an increase in the volume and purulence of the lower respiratory tract secretions and is frequently associated with signs of variable airflow obstruction. In the intensive care unit (ICU), tracheobronchitis is a relatively common problem with an incidence as high as 10.6% [1]. Although tracheobronchitis is associated with a significantly longer length of ICU stay and a prolonged need for mechanical ventilation, it has not been shown to increase mortality. These outcomes can be improved through the use of antimicrobial agents [1].

Tracheitis in Pediatric Patients

Despite the advances that have been achieved in supportive pediatric intensive care, tracheitis remains a significant cause of reversible upper-airway obstruction in pediatric patients. This discussion highlights the epidemiology and clinical presentation of tracheitis in the twenty-first century and reviews diagnostic and therapeutic modalities. The gold standard for therapy remains supportive airway management in conjunction with appropriate antibiotic therapy. Finally, the unique challenges of diagnosis and treatment of tracheitis in the technology dependent child with an existing artificial airway (endotracheal tube or tracheostomy) are addressed.

Lower respiratory tract infections in chronic obstructive pulmonary disease outpatients with tracheostomy and persistent colonization by P. aeruginosa

Outpatients with tracheostomy can be managed with a low risk for severe airways infections despite colonization with pathogenic bacteria. No studies have been focused on chronic obstructive pulmonary disease (COPD), a condition known for recurrent exacerbations. The aim of our study was to verify whether at follow-up in tracheostomized COPD versus other disease outpatients, persistent P. aeruginosa colonization may influence the rate and treatment of lower respiratory tract infections (LRTI) or hospital admissions. Thirty-nine outpatients were considered: 24 were affected by COPD (age 66, 54-78 years, mean, range), 15 by restrictive lung disease (RLD) (57, 41-72 years). During an 18-month follow-up the number of LRTIs were recorded. Bacterial identifications were assessed at baseline and every month for 6 months in bronchial aspirates. The number of LRTI per patient was not significantly different between COPD [37, 1(0-6)] and RLD [18, 1(0-5)], [total, median (range)]. Persistent P. aeruginosa colonized 18 COPD (75%), 12 RLD patients (86%) and was not associated with an increased number of LRTI: 1(0-6) and 1(0-2), respectively. There were no differences in the number of hospital admissions: COPD 0(0-2), RLD 1(0-1), with a significant decrease versus before tracheostomy (P < 0.001). In conclusion, the rate of LRTI and hospital admissions in COPD outpatients with chronic tracheostomy was low, similar to non-COPD patients and independent of P. aeruginosa colonization.

Elevated Tissue Kallikrein Activity in Airway Secretions from Patients with Tracheobronchitis Associated with Prolonged Mechanical Ventilation

The clinical course of patients undergoing prolonged mechanical ventilation is often complicated by the development of purulent tracheobronchitis. The purpose of this study was to assess whether ventilator-associated hypersecretion is associated with elevated levels of tissue kallikrein (TK) activity. TK can induce marked bronchial inflammation in animal models and TK activity is increased in the airway secretions of symptomatic asthmatics. It has not been studied in conditions with predominantly neutrophilic bronchial secretions, although animal data indicate that neutrophil elastase may stimulate TK activity. We measured TK activity in airway secretions of patients undergoing mechanical ventilation for more than 4 weeks (PMV group) and in two comparator groups: patients with cystic fibrosis, who were colonized with Pseudomonas aeruginosa (CF group) and patients undergoing mechanical ventilation for less than one week who did not have clinical evidence of purulent airway secretions (acute mechanical ventilation, AMV group). We also compared the level of neutrophil elastase (NE) activity, an index of neutrophil activation, in the three patient groups. TK and NE activity in the sol phase were measured by the degradation of chromogenic substrates (DL Val-Leu-Arg pNA and N-Methoxy Succinyl Ala-Ala-Pro-Val pNA, respectively). Intergroup differences in cell counts were not significant. However, TK activity was significantly less in the AMV group than in the PMV and cystic fibrosis patients (Kruskal-Wallis ANOVA, p < 0.05). Elastase activity was significantly greater in the CF group (p < 0.05) than in the other two groups. Compared to patients undergoing short-term mechanical ventilation (AMV group), TK activity was elevated in patients with purulent tracheobronchitis associated with prolonged mechanical ventilation (PMV group). The elevation in TK activity in these patients is comparable to levels in sputum from patients with cystic fibrosis (CF group), although the latter had a significantly higher level of NE activity. The observation of increased TK activity in patients with neutrophilic airway inflammation suggests that TK may play a role in modulating inflammation in ventilator-associated tracheobronchitis and may be worthy of further study to determine its source and significance.

Influence of clinical history on airways bacterial colonization in subjects with chronic tracheostomy

Patients with chronic tracheostomy are subject to significant bacterial colonization of the airways, a risk factor for respiratory infections. The aim of our study was to verify whether bacterial colonization and humoral immune response in the airways can be influenced by the disease which led to chronic respiratory failure and tracheostomy. Thirty-nine clinically stable outpatients with chronic tracheostomy were considered: 24 were affected by chronic obstructive pulmonary disease (COPD) (mean age 66 years, range 54-78, M/F 19/3; months since tracheostomy 23, range 3-62), 15 by restrictive lung disease (RLD) (12 thoracic wall deformities, three neuromuscular disease; age 57 years, range 41-72; M/F 3/12, months since tracheostomy 22, range 2-68). Recent antibiotic or corticosteroid treatments (< 1 month) were among exclusion criteria. Bacterial counts were assessed in tracheobronchial secretions with the method of serial dilutions. Identification of bacterial strains was performed by routine methods. Albumin, IgG, A, and M were measured in airways secretions with an immunoturbidimetric method. No significant differences were found between the two groups as regards either the quantitative bacterial cultures (RLD 81.4, 2.6-4200 x 10(4); COPD 75.9, 1.0-1530 x 10(4) colony forming units (cfu)/ml, geometric mean, range) or the prevalence of the main bacterial strains, (Pseudomonas species: 38 and 37%, Serratia marcescens: 31 and 23%, Staphylococcus aureus: 14 and 6%, Proteus species: 3 and 8%, for RLD and COPD respectively) as a percentage of total strains isolated (RLD = 26, COPD = 48). Immunoglobulin levels did not show significant differences, apart from being higher in underweight subjects. We conclude that in our series of stable outpatients with chronic tracheostomy, bacteria-host interaction in the airways was not influenced by the clinical history.

Bacterial colonization of central airways after stenting

Airway stenting (AS) is increasingly used in the management of obstructive lesions of the central airways. Although retention of secretions and infection have been reported as complications of AS, the microbiological consequences of AS have not yet been evaluated. In this study, we prospectively performed protected specimen brush (PSB) sampling of the airways, before and 3 to 4 wk after AS, in 14 consecutive patients (65 +/- 17 yr), suffering from bronchial (5), extensive esophageal (2), thyroid (1), and adenocystic (1) carcinoma, stenotic tracheal burn lesions (2), postintubation stenosis (2), and Wegener's granulomatosis (1). A cutoff value of >/= 10(2) colony-forming units (cfu). ml(-)(1) was considered diagnostic for airway colonization (AC). PSB results were related to the presence and degree of secretion retention (SR) at the level of the stent. In five of the 14 patients, AC was present prior to AS; in three of these, potentially pathogenic microorganisms (PPM) were identified. After AS, AC was found in 11 (including seven patients without prior AC) of the 14 patients. In six of these patients, one or more PPM were present (Pseudomonas aeruginosa [4], Staphylococcus aureus [3], Streptococcus pneumoniae [1], Klebsiella spp. [1]). Although AC tended to be associated with the presence of SR (PSB >/= 10(2) cfu. ml(-)(1) in 10 of 12 SR-positive and in zero SR-negative cases; PSB < 10(2) cfu. ml(-)(1) in two SR-positive and in two SR-negative cases), statistical significance was not reached (Fisher exact test, p = 0.06). We conclude that AS is frequently followed by AC, the majority of which occurs in patients without AC prior to AS, and is caused by PPM. In no case, however, AC was associated with clinical signs of infection. AC tended to be associated with SR in the stent.

[Diagnostic characteristics of acquired pneumonia in patients under mechanical respiration]

Ventilator-associated pneumonias (VAP) are the most frequent nosocomial lung infections. Histological diagnosis is the standard for reference. A diagnosis of VAP can be considered in presence of fever or hypothermia, hyperleucocytosis or leucopenia, worsening of blood gases, and new radiological infiltrate. Their diagnostical value is dependent on the number of included manifestations. A clinical pulmonary infection score (CPIS) has been produced and compared with histological data. Bacteriological data are essential for an adapted antibiotherapy. The blind non-protected specimen brush is inexpensive and reliable at levels of 10(4) and 10(6) CFU.mL-1, the sensitivity and specificity reach 60%. The double-protected catheter is a sensitive and specific test at the level of 10(3) CFU.mL-1. At present its accuracy has only been compared with bronchial brushing. The culture of a 20 mL mini-broncho-alveolar lavage (same material) is specific (50%) but not sensitive enough (< 70%) at the level of 10(3) CFU.mL-1. The culture of the protected telescopic brush is the most expensive test. It does not carry a risk of contamination, but does not detect a significant amount of VAP even at a level below 10(3) CFU.mL-1. Due to its high specificity it is used as the reference test in numerous studies. The endoscopic broncho-alveolar lavage provides a rapid diagnosis. Although not protected, it carries a low risk of false positives. It also allows the diagnosis of non-bacterial or atypical bacterial lung infections. The diagnosis can also be obtained with lung biopsy which however carries a risk in case of mechanical ventilation, whatever the technique. Except for the protected double catheter, a direct examination has been advocated, for the differentiation between infection and colonization and the improvement of the performances of the simple culture of the broncho-alveolar lavage (search for intra-cellular bacteria).

Suspected respiratory tract infection in the tracheostomized child: the pediatric pulmonologist's approach

STUDY OBJECTIVES

It is difficult to determine, in the child with a long-term tracheostomy, when bacterial airway colonization has progressed to a respiratory infection requiring antibiotic treatment. Our aim was to investigate whether there is a consensus regarding this and related chronic care issues among clinicians treating these patients.

DESIGN AND SETTING

A questionnaire asking about practices regarding use of tracheal aspirate cultures and antibiotics was distributed to 47 pediatric pulmonary centers.

PARTICIPANTS

Individuals representing 34 centers (72%), caring for 10 to 400 patients, responded.

INTERVENTIONS

None.

RESULTS

At 65% of centers, management is variable, dependent on the patient's underlying condition. The most common indications to obtain a culture were change in secretions (91%) or fever without an obvious source (21 centers). Indications to treat with antibiotics included many leukocytes in secretions (21 centers) or a respiratory illness (18 centers). When treating, 97% prescribe antibiotics empirically, most often enterally; nine centers use inhaled antibiotics. In most centers (79%), management is often done by telephone.

CONCLUSIONS

Although pediatric pulmonologists tend to have similar approaches to assessment and management of suspected respiratory tract infections in tracheostomized children, no clear consensus exists, and much of current practice is empirical. To optimize care of these patients, studies should be conducted to develop criteria to objectively differentiate bacterial airway "colonization" from "infection."

Impact of tracheotomy on colonization and infection of lower airways in children requiring long-term ventilation: a prospective observational cohort study

STUDY OBJECTIVES

Determination of the following: (1) colonization and infection rates in children requiring long-term ventilation initially via a transtracheal tube and subsequently via a tracheotomy; (2) the number of infection episodes per 1,000 ventilation days, during both types of artificial airways; and (3) routes of colonization/infection of the lower airways, ie, whether the pathogenesis was endogenous (via the oropharynx) or exogenous (via the transtracheal tube or tracheotomy).

DESIGN

Observational, cohort, prospective study over 2 1/2 years.

SETTING

Pediatric ICU (PICU), Royal Liverpool Children's National Health Service Trust of Alder Hey, a tertiary referral center.

PATIENTS

Twenty-two children requiring long-term mechanical ventilation initially transtracheally and subsequently via a tracheotomy.

INTERVENTION

Nil.

RESULTS

The lower airways were colonized in 71% of children during transtracheal ventilation; posttracheotomy, this was 95% (p=0.03). Children developed significantly fewer infections following colonization with a microorganism posttracheotomy (8/15 pretracheotomy vs 6/21 posttracheotomy; p=0.013). Throughout the study, there were a total of 17 episodes of infection, all of which were preceded by colonization. Haemophilus influenzae, Staphylococcus aureus, Acinetobacter baumannii, and Pseudomonas aeruginosa were the same four causative pathogens during mechanical ventilation both transtracheally and via tracheotomy. Forty-nine episodes of colonization were observed, 15 pretracheotomy and 34 posttracheotomy; of these, 12 (80%) and 19 episodes (56%), respectively, were primary endogenous, ie, present in the oropharynx on hospital admission and subsequently at tracheotomy. Only one colonization episode (7%) of exogenous pathogenesis was observed during transtracheal intubation, while 12 (35%) (p=0.02) occurred after tracheotomy. An equal number of secondary endogenous colonization episodes (two and three, ie, acquired in the oropharynx after PICU admission and after tracheotomy, respectively, were recorded.

CONCLUSIONS

(1) Despite a high level of hygiene, exogenous colonization without subsequent infection was common. (2) Although all patients were colonized, the infection rate was lower after tracheotomy. This may be due to enhanced immunity (medically stable) and improved tracheobronchial toilet. (3) Microorganisms in children with tracheotomy differ from those in adults.

Tracheal aspirates in long-term mechanically ventilated patients. A human model of gram-negative infection and airway inflammation

It is well known that patients requiring long-term mechanical ventilation and tracheostomy have nearly universal airway colonization with Gram-negative organisms. However, useful parameters to objectively describe the airway inflammation associated with airway instrumentation and colonization have not been well define. In our respiratory care unit, patients who are medically stable except for ventilator dependence are readily available for longitudinal assessment of airway secretions and therefore provide a unique population for studying airway inflammation and infection. To quantitate production of respiratory secretions, we instituted a uniform protocol of suctioning over a 6-h period. Further, we devised a method of dilution and homogenization of tracheal aspirates that permits reproducible intrasample total cell counts (coefficient of variation, 4.6%). With these techniques, patients were then studied serially over a 4- to 7-week period. Total cell count, inflammatory cell differential, and two indices of airway inflammation, human neutrophil elastase (HLE) and soluble-intercellular adhesion molecule-1 (sICAM-1) studied in the sol phase of secretions were monitored. The mean total cell count was 42.2 x 10(6) cells per gram of secretions when patients were clinically stable and not receiving antibiotics. The average differential was neutrophils 69.9%, macrophages 26.9%, and lymphocytes 2.8%. Mean active HLE was 35.6 micrograms/mL and mean sICAM-1 was 83 ng/mL. Six patients during the period of observation received intravenous oral or aerosolized antibiotics for tracheobronchitis. A threefold drop in volume of secretions was measured (p < 0.018). The total cell count and percent neutrophils decreased from 76.4 x 10(6)/g of sputum to 54.9 x 10(6) and 72.2 to 54.9%, respectively. While these changes were not statistically significant, the absolute number of airway neutrophils over the 6 h decreased sevenfold (p < 0.014). Similarly sICAM-1 burden (micrograms per 6-h period) also decreased significantly (p < 0.034). These patients provide a unique human model for future studies specifically designed to assess the effect of novel modalities of anti-inflammatory and antimicrobial agents on respiratory secretions.

Bronchoscopic diagnosis of pneumonia

Lower respiratory tract infections are characterized by significant morbidity and mortality but also by a relative inability to establish a specific etiologic agent on clinical grounds alone. With the recognized shortcomings of expectorated or aspirated secretions toward establishing an etiologic diagnosis, clinicians have increasingly used bronchoscopy to obtain diagnostic samples. A variety of specimen types may be obtained, including bronchial washes or brushes, protected specimen brushings, bronchoalveolar lavage, and transbronchial biopsies. Bronchoscopy has been applied in three primary clinical settings, including the immunocompromised host, especially human immunodeficiency virus-infected and organ transplant patients; ventilator-associated pneumonia; and severe, nonresolving community- or hospital-acquired pneumonia in nonventilated patients. In each clinical setting, and for each specimen type, specific laboratory protocols are required to provide maximal information. These protocols should provide for the use of a variety of rapid microscopic and quantitative culture techniques and the use of a variety of specific stains and selective culture to detect unusual organism groups.

Potential hazards of tracheobronchial suctioning

Tracheobronchial suctioning is a routine practice frequently carried out in intensive care units (ICUs). It is required when the normal coughing mechanism is inadequate or disrupted; for example, where there is underlying respiratory or neurological disease, or where the cough is deliberately suppressed by sedative, muscle relaxants or anaesthetic agents while a patient is undergoing intermittent positive pressure ventilation. The procedure is carried out via a nasotracheal, orotracheal or tracheostomy tube. During the performance of this intervention, the skilled nurse is aware of the risks to which the patient is exposed and endeavours to prevent or minimise possible complications. In the following account of complications that may occur during or as a result of the procedure these have been classified as immediate, intermediate and later complications, as shown in Table 2. The purpose is to stimulate greater awareness of the hazards involved in this common everyday practice in intensive care units.

Preventing nosocomial pneumonia: state of the art and perspectives for the 1990s

In the 1980s, nosocomial pneumonia became the second most common nosocomial infection in the United States. Gram-negative bacilli and Staphylococcus aureus were the most frequently isolated bacteria. Methods to improve the diagnostic sensitivity and specificity included transtracheal aspirates and bronchoscopy with protected specimen brush or bronchoalveolar lavage. Multivariate analysis was used to identify independent risk factors for pneumonia and fatality in different subsets of high-risk patients. Gastric pH and colonization were evaluated as risk factors for pneumonia in mechanically ventilated patients. Colonized respiratory therapy equipment and contaminated tubing condensate and in-line medication nebulizers were suggested as possible sources of nosocomial pathogens. Staff education programs, the use of barrier precautions, and selective decontamination of the digestive tract were associated with reduced rates of lower respiratory tract infection. Despite a decade of progress in our understanding of nosocomial pneumonia, progress in the 1990s will undoubtedly include molecular epidemiologic techniques, appropriate application of risk factor data, and the use of new methods for the diagnosis of pneumonia. Prevention strategies should focus on more effective infection control techniques, improved invasive devices/equipment, and the judicious use of antibiotics for treatment and prophylaxis.

Prospective study of the complications of endoscopic laryngeal surgery

Patients undergoing 204 endoscopic laryngeal operations were studied prospectively to determine the incidence of complications. Twelve patients were considered to be at high risk of postoperative airway obstruction. Two of these patients had an elective tracheostomy. One required temporary reintubation in the recovery room. No case of respiratory obstruction occurred in a patient not considered to be in the high risk group. Mucosal haemorrhage or oedema was seen on postoperative indirect laryngoscopy in 31 per cent of patients. The commonest abnormality found was mucosal haemorrhage in the oropharynx.

Ventilatory muscle support in respiratory failure with nasal positive pressure ventilation

Long-term intermittent mechanical ventilation results in improvements in ventilatory performance and clinical status between ventilation sessions in patients with chronic respiratory failure. The application of intermittent positive pressure ventilation through a nasal mask (NPPV) is a simple, noninvasive method for the provision of chronic intermittent ventilatory support. We investigated the effects of NPPV on inspiratory muscle activity in three normal subjects and nine patients with acute or chronic ventilatory failure due to restrictive (four subjects) or obstructive (five subjects) respiratory disorders. NPPV resulted in reductions of phasic diaphragm electromyogram amplitude to 6.7 +/- 0.7 percent (mean +/- SEM) of values obtained during spontaneous breathing in the normal subjects, 6.4 +/- 3.2 percent in the restrictive group, and 8.3 +/- 5.1 percent in the obstructive group. Simultaneous decreases in activity of accessory respiratory muscles were observed. The reductions in inspiratory muscle activity were confirmed by the finding of positive intrathoracic pressure swings on inspiration in all subjects. With NPPV, oxygen saturation and PCO2 remained stable or improved as compared with values obtained during spontaneous breathing. These results indicate that NPPV can noninvasively provide ventilatory support while reducing inspiratory muscle energy expenditure in acute and chronic respiratory failure of diverse etiology. Long-term assisted ventilation with NPPV may be useful in improving ventilatory performance by resting the inspiratory muscles.

Computerized colonization-surveillance based on antimicrobial susceptibility patterns

In order to estimate the occurrence of hospital-acquired colonizations, a specific program based on antimicrobial susceptibility tests was developed for the early recognition of clusters of colonized patients. This program allowed: (a) estimation of the endemic level of nosocomial colonization every three days within an intensive care unit; (b) detection of outbreak of hospital-acquired infections; (c) distinction between primary and secondary infections according to the dates of admission and collection; (d) provision of the latest profiles of susceptibility to antimicrobials for the 5 pathogens studied (Staphylococcus aureus, S. epidermidis, Serratia spp., Pseudomonas spp., Acinetobacter spp.). This study reported the experience of a two-year trial in colonization surveillance.

Assisting ventilation in respiratory failure by negative pressure ventilation and by rocking bed

The present study was undertaken to evaluate the effectiveness of acute ventilation by rocking bed (RB) and by negative-pressure ventilator (NPV) on arterial oxygenation and carbon dioxide tension in seven patients in whom respiratory failure (PaCO2 [+/- SD], 64 +/- 4 mm Hg; PaO2, 54 +/- 10 mm Hg) was consequent on nonobstructive ventilatory impairment. The increase in SaO2 (percent above baseline, 5 percent RB and 6 percent NPV) was similar for both methods, but a greater fall in PCO2 (percentage change in PCO2, 3 percent RB; 15 percent NPV; p less than 0.05) was observed during NPV. Diaphragmatic and accessory muscle electrical activity was markedly reduced during NPV but remained unchanged or increased on RB. Asynchronous breathing was frequently observed with RB but only rarely with NPV. These preliminary results suggest that effective mechanical ventilatory support could be achieved with either RB or NPV. However, their long-term effects as compared with those of positive-pressure ventilation remain to be explored.

Respiratory infection complicating long-term tracheostomy. The implication of persistent gram-negative tracheobronchial colonization

Colonization of the lower respiratory tract by enteric Gram-negative bacilli (EGNB) has been a frequent finding in patients with long-term tracheostomies; however, the association of hospitalization and certain features of serious illness with this phenomenon has not been clearly established. Because such factors can render the oropharynx more susceptible to EGNB colonization, we sought to discover whether they can also have this effect on the tracheobronchial tree and its microflora. Thus, we collected serial paired culture samples from these two mucosal sites in 15 subjects with long-term tracheostomies and examined patterns and rates of colonization and related these findings to clinical parameters. In 49 sets of cultures, we found that EGNB (especially Pseudomonas species) were present in significantly fewer upper-airway cultures (36.7 percent) than lower-airway cultures (75.5 percent) (p = 0.009). At the tracheobronchial site, seven subjects had persistent EGNB colonization, all with Pseudomonas species, while only one subject had this finding at the oropharyngeal site (p = 0.015). Patients with persistent tracheobronchial colonization were more ill than those without this finding. They were treated with higher doses of prednisone (p = 0.06), received antibiotics more often, and developed purulent tracheobronchitis more often (100 percent vs 25 percent) than patients without persistent colonization. In addition, in the month following the culture survey, four subjects developed pneumonia, and three of these had previous persistent tracheobronchial colonization.(ABSTRACT TRUNCATED AT 250 WORDS)