Mechanical ventilation in ICUs in Poland: A multi-center point-prevalence study

Background

Mechanical ventilation is the primary method of supporting organ function in patients treated in intensive care units (ICUs) and has become emblematic of the ICU because its use resulted in the creation of intensive care units and established intensive therapy as a separate medical field [1]. In recent years, a wide variety of ventilation strategies have become available because of new ventilators that offer complex modes and different parameters for ventilating and weaning patients from respirators. In the last decade it has become widely accepted that the lungs can be damaged by mechanical ventilation and that this can be avoided by using the correct ventilation modes [2]. As a result, the frequency and manner in which mechanical ventilation is used in the ICU has become an interesting epidemiological issue.

Epidemiological studies on the use of mechanical ventilation have used different research methodologies. A 1-day, point-prevalence study was first carried out in Spain [3] and then repeated in an international study involving centers in Spain, Portugal, and North and South America [4]. A similar project was done in Scandinavia [5]. Subsequent retrospective [6] and prospective observational studies were performed to obtain more precise information on the application of mechanical ventilation using more advanced epidemiological methodologies [7–11].

The main objective of our study was to describe the use of mechanical ventilation in the ICUs in Poland because there is no information available on the current patterns of use of mechanical ventilation for treating patients in our country. We decided to use the point-prevalence approach used in previous studies. Our study collected information in the form of completed questionnaires on the frequency and mode of mechanical ventilation in ICUs during a specific period of time (1 day) to make an overall assessment of mechanical ventilation strategies.

Material and Methods

STATISTICAL ANALYSIS:

The data distribution was not normal (the Shapiro-Wilk test) and results were presented as the median with the first and third quartile (25^th and 75^th percentiles) or proportions (%). Results from university hospitals were compared with data from regional, community, and other facilities with the Mann-Whitney U test. Differences in values were considered statistically significant when the value for p was less than 0.05. Statistical analysis was performed with Statistica 9.0 (StatSoft Inc. Tulsa, OK, USA).

Results

VARIABILITY OF THE RESULTS BASED ON HOSPITAL TYPE:

The comparative analysis of results based on the hospital type – university hospitals (Group 1) vs. regional, community and other hospital facilities (Group 2) – was performed. The median number of ICU beds was 12 (6, 13) in Group 1 and 6 (5, 8) in group 2 (p<0.05). Bed occupancy was 92% (58, 100) in Group 1 and 66% (56, 86) in Group 2. Acute respiratory failure was more frequently an indication for mechanical ventilation in Group 1 than in Group 2 (p<0.05). On the day of the study, acute respiratory distress syndrome was diagnosed only in patients treated at university hospitals.

Discussion

This multicenter study was designed to evaluate the policies and procedures of administering mechanical ventilation in Poland. In a similar international 1-day study published in 2000, there were 412 ICUs and 1638 ventilated patients [4], and in a 2002 Scandinavian study there were 27 ICUs and 108 ventilated patients [5]. The results of these 3 studies with the same methodology are compared in Table 4.

In the Polish study as many as 74% of patients admitted to the ICU required mechanical ventilation, in comparison to 39% in the international study and 47% in the study done in Scandinavia. This shows that the ICUs in Polish hospitals have high device utilization (DU) for mechanical ventilation, probably because of the small proportion of ICU beds in the hospital. The ventilated population of Polish ICU patients resembled other populations studied in terms of age and sex. In Polish hospitals, coma (usually after cardiac arrest) was more often (40%) the indication for mechanical ventilation than the international (15%) or the Scandinavian study (15%). This may be due to the limited availability of long-term mechanical ventilation facilities in the hospital other than the ICUs. In Poland, many patients had a tracheotomy (41%), which was higher than in the international (24%) and the Scandinavian study (32%).

The reason most often given for acute respiratory failure was postoperative respiratory insufficiency and pneumonia. The diagnosis of ARDS was reported only for 4% of ventilated patients in the Polish study, in comparison with 12% of cases in the international study and 5% of cases in the Scandinavian study. This low rate may be associated with a lack of experience in diagnosing this syndrome [12]. University hospitals were better equipped to diagnose ARDS in ventilated patients. The actual number of patients with ARDS was probably higher, but this study was not designed to analyze precisely the incidence of ALI or ARDS, similar to other prospective cohort studies [13–16].

The mode of ventilation varied in comparison to the Scandinavian study, probably due to the uniform availability of equipment in Scandinavian countries, which is not the case in Poland. The predominant modes of ventilation used on more than half the patients were those that took into account the patient’s own breathing effort, such as SIMV or PS. The mean breathing volume of 8 mL/kg was similar to that used in the international study (9 mL/kg) and the Scandinavian study (7 mL/kg). The tidal volumes used were higher than recommended for the treatment of ARDS, but only 4% of patients had been diagnosed with ARDS. A lung-protective strategy of ventilation should also be used in other types of acute respiratory failure [17]; therefore, the current model of ventilation in ICUs should be modified. The peak inspiratory pressure was similar among studies. The concentration of inhaled oxygen was the same as in the Scandinavian study (40%).

The PEEP value in the Polish study (5 cmH2O) was comparable to the international (5 cmH2O) and the Scandinavian (6 cmH2O). The frequency of using PEEP (81%) was higher than in the international study (69%), but lower than in the Scandinavian countries (99%).

A weakness of our study is the point-prevalence model. One-day cross-sectional studies have several shortcomings, one of the biggest being the lack of information on the medical outcome of ventilated patients, and their morbidity and mortality rates. A decidedly better research method is a prospective study design [7–9]. However, the results presented here, as the first epidemiological assessment of mechanical ventilation in Poland, allow for a preliminary analysis and serve as the first step of planned, prospective research on patients treated with mechanical ventilation. Prospective observational studies are needed to assess the clinical course and prognosis of mechanically ventilated patients.

Based on the results of our study, we established a program for continuous education on mechanical ventilation for intensivists. Over the past 3 years we have annually organized a “Winter School of Ventilation” with active hands-on training in a designated education centre. In 2015 we plan to do a new survey to see how the models and techniques of ventilation will have evolved in the subsequent 5 years.

Conclusions

We have shown that mechanical ventilation is the method most commonly used in ICUs in Poland. Almost half of the ventilated patients in the ICUs were ventilated for extrapulmonary indications (central nervous system and neuromuscular diseases). Patients were ventilated with low concentrations of oxygen, and PEEP was commonly used.