The goal of this observational study is to compare two lung ultrasound protocols for assessing lung function in patients with acute respiratory insufficiency treated in intensive care units.

The main questions it aims to answer are:

1. Is there a statistically significant difference between the established Baciarello (name of author) ultrasound protocol (12-point examination) and a new, abbreviated local ultrasound protocol (6-point examination) for assessing lung function? 2. Do the scoring systems of both protocols correlate with each other and with treatment outcomes in critically ill patients? Researchers will compare the Baciarello protocol (assessing 12 fields-6 per side of the body to a new abbreviated local protocol (assessing 6 fields-3 per side of the body) to see if both protocols provide same diagnostic and prognostic information for evaluating lung pathology and patient outcomes.

Participants will:

Undergo lung ultrasound assessment using both protocols Have their ultrasound findings scored according to each protocol's point system (0-36 for Baciarello; 0-18 for the new abbreviated protocol) Have their arterial blood gas values recorded (pH, PaCO2, PaO2, oxygen saturation) Be monitored for clinical outcomes including mechanical ventilation requirements and hospital mortality

Lung ultrasound (LUS) has gained significant clinical importance in intensive care settings over the past two decades. Unlike other radiological examinations, LUS offers several advantages: it is cost-effective, does not utilize ionizing radiation, enables repeated examination without harmful consequences, and is portable for bedside assessment in real-time. LUS is superior to chest radiography in detecting pleural effusions smaller than 500 mL and demonstrates comparable sensitivity and specificity to computed tomography for diagnosing pathological changes such as pleural effusions, pneumothorax, pneumonia, and pulmonary edema. However, the main limitation of LUS is its operator-dependent nature. Skill and experience significantly influence examination quality, though this limitation can be overcome through practice and standardization. The Baciarello protocol, developed during the 2020 COVID-19 pandemic, divides each hemithorax into 6 fields: anterior (ventral to anterior axillary line), middle (between anterior and posterior axillary lines), and posterior (dorsal to posterior axillary line), with each region further divided horizontally through the xiphoid process. All 12 fields are scored 0-3 points based on ultrasound findings: 0 points (A-lines with pleural sliding or fewer than three B-lines), 1 point (three or more well-distributed B-lines with pleural sliding), 2 points (confluent B-lines or light beam phenomenon), 3 points (pulmonary consolidations including subpleural consolidations). Total scores range from 0-36. Studies showed that patients with total scores ≥12 demonstrated greater need for ICU admission and invasive mechanical ventilation, while scores ≥18 were associated with higher in-hospital mortality. The new abbreviated local protocol reduces examination points to 6 fields (3 per hemithorax) assessed at the level of the nipple or fourth intercostal space in the medioclavicular line, extending horizontally toward the dorsal aspect. Scoring criteria remain identical to the Baciarello protocol, but total scores range from 0-18. Preliminary thresholds suggest scores ≥6 indicate need for non-invasive or invasive mechanical ventilation, while scores ≥9 suggest high in-hospital mortality. Recent studies comparing different LUS protocols with varying numbers of examination points have demonstrated that abbreviated protocols reduce examination duration while maintaining diagnostic accuracy. Research comparing 6-, 8-, and 12-point protocols in COVID-19 patients emphasized examination time efficiency (3 minutes for 6-point protocols versus up to 10 minutes for 12-point protocols) while maintaining clinical utility in emergency settings. A 6-point protocol was found to enable efficient, rapid assessment of lung pathology. However, some studies note that the 8-point protocol's omission of dorsal lung regions-where lung pathology is most common-represents a potential limitation. The 12-point protocol is credited with highest specificity in lung pathology assessment but requires longer examination duration. This study was designed to determine whether the abbreviated 6-point local protocol provides equivalent statistical and clinical information to the established 12-point Baciarello protocol. This comparison is clinically significant given healthcare system strain, staff shortages, and the need for rapid bedside assessment in critically ill patients with acute respiratory insufficiency. If no statistically significant difference exists between protocols, the shorter examination could simplify clinical application of LUS as a diagnostic and prognostic tool in intensive care practice.

Inclusion Criteria:

• Adult patients aged ≥18 years
• Admitted to the Intensive Care Unit (ICU) Susak
• Diagnosed with acute respiratory insufficiency

Exclusion Criteria:

• Technical inability to perform a lung ultrasound due to patient positioning or other technical reasons
• Morbid obesity (BMI ≥40 kg/m²)
• Serious chest trauma that would compromise assessment
• Lung pathology that impairs ultrasound visualisation of the desired examination regions

Patients diagnosed with acute respiratory insufficiency requiring advanced respiratory support who are admitted to the Intensive Care Unit Susak will be enrolled in this prospective study.