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Open Access 01.12.2025 | Research

The effect of prone positioning on ventilator parameters, blood gas levels, and ventilator-associated pneumonia in intensive care unit patients: a randomized controlled trial

verfasst von: Burcu Dedeoğlu Demir, Nuray Enç, Şermin Börekçi

Erschienen in: BMC Nursing | Ausgabe 1/2025

Abstract

Objectives

This study was planned to compare the prone position and non-prone position groups and to evaluate arterial blood gas results, mechanical ventilator values and ventilator-associated pneumonia (VAP) status before, during, and after patients were brought back to the non-prone position.

Design

This study is a randomized controlled trial with a parallel-group design and a 1:1 allocation ratio. A block randomisation method was used to ensure balanced allocation between two groups.

Setting

The research was conducted in the 14-bed and 26-bed general ICUs of two private hospitals on the European side of Istanbul.

Participants

The 94 eligible participants were randomly divided into two groups. 52 participants were assigned to the prone position group, while 42 participants were assigned to the non-prone position group, which served as the control group. In the end, 40 participants were in each group.

Intervention

The intervention involved placing patients in the prone position and monitoring their arterial blood gas results, mechanical ventilator values, and VAP status at multiple stages: before, during, and after returning them to the non-prone position. Each patient was followed for a minimum of 5 days.

Results

The majority of the participants were male (51.2%) and aged 45–64 (48.8%). The comparison of experimental and control groups indicated statistically significant difference in saturation, FiO₂, inspiratory-expiratory tidal volume, and blood gas levels of the patients in the treatment group (p = 0.001; p < 0.01).

Conclusions

The change in the experimental group was greater than in the control group. In conclusion, the mechanical ventilator parameters and blood gas levels of the patients in the treatment group were better than those of the patients in the control group. It is recommended as an effective practice in patients receiving prone position mechanical ventilation (MV).

Clinical trial registration number and registration date

: NCT05760716/ March 6, 2023 (This trial was registered retrospectively at ClinicalTrials.gov (Registration Number: NCT05760716) after its completion due to demanded revisions. The integrity of the data and adherence to the study protocol were ensured throughout. The trial adhered to ethical standards (ethics committee approval, informed consent) even if it was not registered prospectively).

Supplementary Material 1

Supplementary Information

The online version contains supplementary material available at https://doi.org/10.1186/s12912-025-02817-3.

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Background

Patients on MV (MV) are prone to nosocomial infections due to immobility. Changing the patient’s position frequently is necessary to prevent the consequences of inactivity. Studies suggest that placing patients in a prone position may improve oxygenation in those receiving MV. Prone position was first employed in MV in the 1970s, to increase lung capacity and improve oxygenation in acute lung failure [1]. The prone positioning maneuver involves placing a patient on their abdomen (face down) instead of the traditional supine (back) position, commonly used in intensive care settings for patients requiring MV. When in the prone position, gravity assists in opening the dorsal (posterior) lung regions, which are often under-ventilated when the patient is lying on their back. As a result, this positioning can help recruit collapsed alveoli, enhance ventilation-perfusion matching, and reduce the work of breathing [2]. Miller [3] first highlighted the benefits of prone positioning, citing improved lung expansion and oxygenation. This position enhances ventilation and blood circulation coordination, increases exhalation volume, and intervenes in rib cage volume changes [4]. Guerin et al. [5] found that oxygenation in arterial blood increased from 23 to 34% during the first three days in the prone position. However, a 2016 study by Haddam et al. [6] reported no significant impact on patient oxygenation. Research has shown that the prone position is protective against preventing ventilator-induced lung injury, and it has also been found to increase PaO2/FiO₂ in 70% of intensive care patients with severe hypoxemia who receive MV support [4, 6‐8]. In patients who have undergone prone position, the decrease in pressure on the lungs and the fact that the lung perfusion is more homogeneous are effective in protecting the lung [9, 10].

Prone positioning improves oxygenation and ventilation in patients with acute respiratory distress syndrome (ARDS) and is associated with better morbidity and mortality outcomes. A systematic review indicated that it likely reduces mortality in severe ARDS when applied for at least 12 h daily [11]. The PROSEVA trial showed that prolonged prone positioning significantly decreased both 28-day and 90-day mortality rates [5]. Additionally, it helps prevent ventilator-induced lung injury by promoting uniform alveolar ventilation and reducing overdistension [2]. These findings emphasize the importance of prone positioning as a standard care intervention in severe respiratory failure, improving long-term outcomes and lowering mortality rates.

Giving a position is one of the practices that nurses do by using their professional knowledge and skills. The positive effects of the position given to patients in intensive care on treatment and care are indicated. However, when the literature is examined, it is seen that there are not many studies on what are the position practices in intensive care patients in our country and how they affect health, the guiding nursing guidelines to be used in position change are missing and clinical studies are insufficient. However, nurses continue to perform key roles in the follow-up and treatment of patients who are prone under MV therapy to provide the best clinical outcomes from continuous evaluation of patients to the realization of care practices [4, 6, 7].

Bringing intensive care patients to the prone position; endotracheal tube obstruction includes the risk of serious complications such as unplanned extubations, stones and bradyarrhythmias, loss of venous and arterial access, cardiac arrest, and the development of pressure ulcers in the anterior body surface areas [12, 13]. Safely changing positions for a patient requires a multidisciplinary approach and a team of trained professional clinicians, including respiratory therapists, nurses and a doctor. Prone positioning is evaluated on an individual basis. Although it is beneficial in some settings, not all patients get better, and some may get worse [1, 4, 6‐8].

Complete care of patients receiving MV support is an important part of intensive care nursing. Therefore, in addition to the use of MV, a supportive intervention plan should be designed to improve the quality of oxygenation and other care measures for patients, control the effect of treatment, and prevent the side effects of MV. Nowadays, since evidence-based nursing is given importance, it is necessary to conduct a lot of research on the effects, effectiveness and possible dangers of prone position for the patient in order to use nursing measures such as prone position effectively in ICUs with unstable and semi-stable hemodynamic patients.

Prone positioning has been associated with improved oxygenation in mechanically ventilated patients. However, its effect on VAP incidence is less clear. Some studies suggest that prone positioning may reduce VAP by enhancing secretion drainage and reducing aspiration risk. Conversely, other research indicates no significant impact on VAP rates. Therefore, further investigation is needed to clarify the relationship between prone positioning and VAP incidence [14, 15].

Previous studies, including the PROSEVA trial, have highlighted the mortality benefits of prone positioning in severe ARDS patients [5]. However, the effects on ventilator parameters, arterial blood gas levels, and ventilator-associated pneumonia (VAP) are not well understood. Existing research often focuses on short-term oxygenation improvements, overlooking a comprehensive evaluation of respiratory mechanics and infection outcomes. This study examines the effects of prone positioning on a diverse group of ventilated patients, rather than just those with severe ARDS. By including all eligible patients, it aims to provide a broader understanding of the intervention’s impact, making the findings more relevant to real-world ICU populations.

This study was planned as a randomized controlled experimental study to compare the prone position and non-prone position groups and to determine the effect of prone position by evaluating arterial blood gas results, mechanical ventilator values and VAP status before, during, and after patients were brought back to the non-prone position.

Methods

Design and setting

This study was designed as a randomized controlled trial to evaluate the effects of prone positioning versus non-prone positioning in mechanically ventilated patients in a clinical setting. The research was conducted between June and December 2021 in the 14-bed and 26-bed general ICUs of two private hospitals on the European side of Istanbul.

This study is a randomized controlled trial with a parallel-group design and a 1:1 allocation ratio and was designed and reported in accordance with the Consolidated Standards of Reporting Trials (CONSORT) guidelines to ensure transparency and rigor in the methodology and presentation of results.

Outcomes of the study

The primary outcome of this study is the change in arterial blood gas values after prone positioning compared to non-prone positioning.

Secondary outcome include changes in mechanical ventilator parameters (PEEP, tidal volume) and the incidence of VAP.

Hypotheses of the research

There is no significant difference between the experimental and control groups in terms of MV values, blood gas values and the development of VAP.

Mechanical ventilator mode values of the experimental group will be better than the control group.

Blood gas results of the experimental group will be better than the control group.

The rate of VAP development in the experimental group will be less than the control group.

Participants and randomization

The sample size calculation is based on a hypothesized treatment effect of a 20% improvement in PaO2/FiO₂ ratio for the prone positioning group compared to the non-prone group. The expected standard deviation is 10, and we aim for 80% power with a 0.05 alpha level. Studies should have 80% power, and the power of the study is expressed as “1-β (β = II type error probability)”. Using this, the required sample size per group is calculated as 30, based on the power analysis that was conducted using the “G*Power (v3.1.7) program.

Inclusion criteria

18 years of age or older,
Receiving respiratory support with a mechanical ventilator in the ICU,
A negative COVID-19 test,
Consent given by the first-degree relative.

Exclusion criteria

Under 18 years of age,
Diagnosis of VAP before ICU admission,
Positive COVID-19 test,
Having an obstacle (obesity, pregnancy, anterior chest wall surgery, advanced heart failure, etc.) to the prone position.
Lack of consent to participate in the study by the first-degree relative.

A total of 186 participants were initially assessed for eligibility. 92 participants excluded as they fulfil the exclusion criteria. 94 participants met the inclusion criteria. Eligible participants were approached, and written informed consent was obtained from the first-degree relatives before randomization. Following the consent process, participants were randomly assigned to one of two groups (prone position group and non-prone position group). A block randomisation method was used to ensure balanced allocation between two groups, considering the high attrition rate expected in this critically ill population. The randomisation sequence was computer-generated with variable block sizes to ensure balance, and allocation was performed after obtaining informed consent from the participants’ first-degree relatives. This approach ensured equal representation of participants in each group, even with the anticipated loss to follow-up. A health professional that independent of the trial conduct created the randomisation sequence to prevent bias. Enrollment was conducted by trained staff, ensuring that the process adhered to inclusion and exclusion criteria. A health professional separate from the enrollment process assigned participants to groups based on the concealed allocation sequence. Eligible participants were randomly assigned to one of two groups:

Prone Position Group: This group received the intervention of prone positioning, which involves placing the patient face-down with support.
Non-Prone Position (Control) Group: The control group received standard care and was managed in various non-prone (supine and lateral) positions as per the clinical protocol. These positions included supine (face-up), semi-recumbent, and lateral positions, which are commonly used in intensive care settings for mechanically ventilated patients.

Attrition and follow-up

Given the anticipated attrition rate in this high-risk population, we recruited additional participants beyond the initial target of 30 per group to ensure an adequate sample size at the Day 10 assessment. This strategy aimed to mitigate the impact of patient attrition (including mortality and loss to follow-up) on the statistical power of the study. 52 participants were assigned to the prone position group, while 42 participants were assigned to the non-prone position group, which served as the control group and received standard care. During the follow-up period:

In the prone position group, 8 participants were lost to follow-up (5 due to transfering to another hospital and 3 due to mortality), and 4 declined participation after randomization.
In the non-prone position group, 1 participant was lost to follow-up (due to mortality), and 1 declined participation after randomization.

Ultimately, 40 participants in each group completed the study and were included in the final analysis. This recruitment approach was consistent with our ethics approval, which accounted for potential dropouts. We anticipated a high attrition rate due to the critical nature of the study population. As such, additional participants were recruited to maintain the planned sample size at Day 10.

Blinding

Due to the nature of the intervention (prone vs. non-prone positioning), blinding of participants and clinicians was not feasible, as they would be aware of the intervention being administered. However, outcome assessors were blinded to the group assignments to reduce potential bias during data collection and analysis (Fig. 1).

Intervention

The intervention involved placing patients in the prone position and monitoring their arterial blood gas results, mechanical ventilator values (inspiratory tidal and expiratory tidal volumes etc.) and VAP status at multiple stages: before, during, and after returning them to the non-prone position.

The arterial blood gas values assessed in this study included:

Indicates the acidity or alkalinity of the blood.

PaO₂ (mmHg)

Partial pressure of oxygen in arterial blood, reflecting oxygenation levels.

PaCO₂ (mmHg)

Partial pressure of carbon dioxide in arterial blood, indicating ventilation efficiency.

SaO₂ (%)

Arterial oxygen saturation, representing the percentage of hemoglobin bound with oxygen.

The MV values assessed in this study. MV values refer to the parameters monitored during MV to evaluate the effectiveness of respiratory support and assess lung function. These values typically include:

FiO₂ (%)

Fraction of inspired oxygen.

PEEP (cmH₂O)

Positive end-expiratory pressure.

Inspiratory tidal volume (mL)

Volume of air delivered to the lungs with each breath.

Expiratory tidal volume (mL)

Volume of air exhaled after each breath.

PaO₂ (mmHg)

Partial pressure of oxygen in arterial blood.

PaCO₂ (mmHg)

Partial pressure of carbon dioxide in arterial blood.

SaO₂ (%)

Arterial oxygen saturation.

The ventilation mode was either volume-controlled or pressure-controlled, based on the needs of the patients. Importantly, no changes were made to the ventilator modes throughout the intervention. The respiratory rate and PEEP levels were kept constant, with only minimal adjustments made to meet clinical needs in cases of hemodynamic instability.

By analyzing inspiratory tidal and expiratory tidal volumes, we monitored the effectiveness of MV, detect ventilator-associated complications, and evaluate the impact of interventions like prone positioning on respiratory mechanics and gas exchange.

The level of sedation was assessed using the Richmond Agitation-Sedation Scale (RASS), and the need for deep sedation was minimized, with neuromuscular blockers used only in limited circumstances.

Prone positioning protocol

Patients in the prone position group were placed in the prone position once daily. During patient preparation, the eyes, skin areas at pressure points, and the position of the endotracheal tube were carefully maintained, and support from a respiratory therapist and nurse was provided during position changes. The duration of each session was set between 4 and 6 h, depending on the patient’s clinical tolerance. The length of time spent in the prone position was adjusted based on hemodynamic stability, oxygenation status, and ventilator parameters. Each patient was followed for a minimum of 5 days, during which prone positioning was administered as needed based on clinical response. The decision to continue or discontinue prone sessions was individualized according to the patient’s ongoing clinical condition and response to treatment.

Ethical approval

The research was conducted in accordance with the principles set out in the Declaration of Helsinki. Ethical approval and institutional permission were obtained from the…… Ethics Committee (E-69396709-050.06.04-172992 and Decision No: 2). Informed consent was also obtained from the participants in order to evaluate the ethical suitability of the research. Any discrepancies from the original protocol, such as attrition and participant flow, have been reported and addressed accordingly.

Data collection tools

Data collection was carried out using a face-to-face questionnaire. Four main questionnaires were used for the current study.

Patient identification form

With the patient follow-up chart, the vital signs of intensive care patients receiving mechanical ventilator support, ventilator mode values, blood gas values and ETA/BAL culture results were followed up for at least 5 and maximum 10 days. In the first part, questions about the sociodemographic characteristics (age, gender, marital status, educational status and occupation) of the patients were included, while in the second part, questions about the disease, treatment and habits (chronic diseases, smoking and alcohol use, drugs used, body mass index, diagnosis of ICU, intubation-reintubation dates) were included.

PP practice follow-up chart

This chart has been prepared by evidence-based guidelines and researchers using similar studies on this subject [16‐25].

Nursing initiative practice follow-up chart for VAP

This chart has been prepared by evidence-based guidelines and researchers using similar studies on this subject [26‐31].

Clinical pulmonary infection score (CPIS)

CPIS was defined by Pugin et al. [32] as a guiding scoring system in the diagnosis of VAP by evaluating a total of 12 points. CPIS score; leukocyte count, body temperature, endotracheal aspirate (ETA)/microbiological culture results, tracheal secretion amount and character, PaO2/FiO₂ ratio and the presence of pulmonary infiltration examined seven clinical parameters. A score of 6 or more suggests VAP [33].

Data analysis

Data analysis was performed using NCSS 2007 software. The Independent Samples t-test was used for normally distributed quantitative data, while the Mann-Whitney U test was employed for non-normally distributed data. For paired measurements within the same group, the Paired Samples t-test applied to normally distributed data and the Wilcoxon Signed Ranks test for non-normally distributed data. The Repeated Measures ANOVA was used for repeated measurements within groups, followed by Bonferroni post-hoc tests. The Friedman test applied for non-parametric repeated measures, with post-hoc comparisons using the Bonferroni-Dunn test. For categorical data, the Pearson Chi-Square test compared independent groups. The Fisher’s Exact test was used for low expected frequencies, and the McNemar test evaluated changes in paired categorical data. A significance level of p < 0.05 was set for all tests.

Results

Demographic and clinical characteristics of the participants were evaluated. Descriptive and clinical features were similar by group (Table 1).

Table 1

Evaluation of descriptive and clinical features according to groups

		Experimental group (n = 40)	Control group (n = 40)	p
Age (years)	18–29	2 (5.0)	0 (0)	^a0.304
	30–44	5 (12.5)	3 (7.5)
	45–64	21 (52.5)	18 (45.0)
	65–79	11 (27.5)	15 (37.5)
	≥ 80	1 (2.5)	4 (10.0)
Gender	Female	19 (47.5)	20 (50.0)	^b0.823
Gender	Male	21 (52.5)	20 (50.0)	^b0.823
BMI (kg/m²)	< 18 kg/m²	3 (7.5)	5 (12.5)	^a0.257
	18.5–25 kg/m²	30 (75.0)	23 (57.5)
	25–29 kg/m²	7 (17.5)	12 (30.0)
Smoking	Yes	20 (50.0)	16 (40.0)	^a0.590
	No	17 (42.5)	22 (55.0)
	Quit smoking	3 (7.5)	2 (5.0)
Amount of smoking (unit/day) (n = 36)	Min-Max (Median)	18–30 (20)	20–30 (20)	^d0.403
Amount of smoking (unit/day) (n = 36)	Mean ± Sd	24.11 ± 5.18	22.00 ± 3.50	^d0.403
Smoking duration (years) (n = 36)	Min-Max (Median)	8–35 (21.5)	15–30 (25)	^d0.227
Smoking duration (years) (n = 36)	Mean ± Sd	22.32 ± 5.71	24.58 ± 5.82	^d0.227
Alcohol use	Yes	4 (10.0)	8 (20.0)	^b0.210
Alcohol use	No	36 (90.0)	32 (80.0)	^b0.210
Chronic disease status	Yes	37 (92.5)	38 (95.0)	^c1.000
Chronic disease status	No	3 (7.5)	2 (5.0)	^c1.000
Intensive care hospitalization diagnosis	Respiratory Failure	24 (60.0)	12 (30.0)	^a0.080
	COPD Exacerbation	4 (10.0)	6 (15.0)
	Lung CA	2 (5.0)	6 (15.0)
	Pneumonia	1 (2.5)	3 (7.5)
	Other	9 (22.5)	13 (32.5)
Intensive care hospital stay (days)	Min-Max (Median)	5–10 (5)	5–10 (5)	^d0.691
Intensive care hospital stay (days)	Mean ± Sd (Median)	5.57 ± 1.07	5.60 ± 1.01	^d0.691
APACHE II Score		21.4 ± 5.2	22.1 ± 4.8	^d0.628
P/F Ratio (admission)		180.5 ± 25.4	172.8 ± 20.7	^d0.314
Baseline Sedation Score (RASS)		-2.3 ± 0.5	-2.5 ± 0.6	^d0.210
Type of Sedative Used (%)		Midazolam (40%). Propofol (60%)	Midazolam (50%). Propofol (50%)
Total Sedative Dose (mg/day)		35 ± 10	32 ± 9	^d0.150

∎Multiple selections were made The number of reintubations could not be evaluated because of insufficient. ^a Fisher Freeman Halton Test ^b Pearson Chi-Square Test ^c Fisher’s Exact Test ^d Mann Whitney U Test

There were no significant differences in systolic blood pressure measurements between the groups on Days 1, 2, 3, and 4 before and after prone positioning. However, after prone positioning on Day 5, a statistically significant difference was observed, with the experimental group showing higher measurements than the control group (Experimental: 132.5 ± 5.6 mmHg, Control: 128.3 ± 4.9 mmHg, p = 0.025). Similarly, diastolic blood pressure measurements before prone positioning on Day 5 were significantly higher in the experimental group compared to the control group (Experimental: 84.6 ± 3.2 mmHg, Control: 80.9 ± 2.8 mmHg, p = 0.040).

Heart rate changes showed statistical significance on Day 1 and Day 3 (Day 1: p = 0.015, Day 3: p = 0.020), with greater increases in the experimental group. Furthermore, a significant difference was found in the change from the first to the last measurements between groups (Experimental: +15.3 ± 2.1 bpm, Control: +9.8 ± 1.9 bpm, p = 0.001) (Table 2).

Table 2

Evaluation of vital signs according to groups

			Systolic blood pressure (mmHg)				Diastolic blood pressure (mmHg)				Heart rate			Saturation (%)
		Experimental group (n = 40)		Control group (n = 40)	p	Experimental group (n = 40)		Control group (n = 40)	p	Experimental group (n = 40)		Control group (n = 40)	p	Experimental group (n = 40)		Control group (n = 40)	p
		Mean ± Sd (Median)		Mean ± Sd (Median)	p	Mean ± Sd (Median)		Mean ± Sd (Median)	p	Mean ± Sd (Median)		Mean ± Sd (Median)	p	Mean ± Sd (Median)		Mean ± Sd (Median)	p
1st day	Pre-prone	127.63 ± 22.06 (130)	Non-prone	133.58 ± 25.91 (134)	^e0.272	74.68 ± 12.01 (75.5)	Non-prone	76.15 ± 13.27 (80)	^e0.604	90.58 ± 14.35 (89)	Non-prone	88.83 ± 14.15 (90)	^e0.584	85.45 ± 4.78 (88)	Non-prone	90.05 ± 3.23 (90)	^d0.001**
1st day	Post prone	131.25 ± 19.21 (133)	Non-prone	134.00 ± 26.58 (136.5)	^e0.598	76.45 ± 11.28 (80.5)	Non-prone	77.38 ± 14.31 (82.5)	^e0.749	94.33 ± 15.05 (89)	Non-prone	91.63 ± 14.01 (91.5)	^e0.409	88.13 ± 5.06 (90)	Non-prone	89.88 ± 3.15 (90)	^d0.220
		^h0.188		^f0.517		^h0.348		^f0.024*		^h0.015*		^f0.011*		ⁱ0.001**		^g0.289
2nd day	Pre-prone	125.00 ± 23.55 (131.5)	Non-prone	130.68 ± 28.14 (133)	^e0.331	72.38 ± 11.84 (72)	Non-prone	75.53 ± 15.42 (80)	^e0.309	94.35 ± 15.05 (92.5)	Non-prone	92.83 ± 15.38 (90.5)	^e0.655	86.55 ± 4.16 (87)	Non-prone	90.35 ± 2.93 (90.5)	^d0.001**
2nd day	Post prone	123.43 ± 22.87 (125.5)	Non-prone	128.88 ± 27.98 (124)	^e0.343	76.20 ± 11.49 (76.5)	Non-prone	74.75 ± 14.70 (80)	^e0.625	96.13 ± 17.43 (93)	Non-prone	95.55 ± 17.17 (94)	^e0.882	89.00 ± 4.18 (90)	Non-prone	90.28 ± 3.09 (90)	^d0.257
		^h0.610		^f0.167		^h0.003**		^f0.449		^h0.318		^f0.003**		ⁱ0.001**		^g0.719
3rd day	Pre-prone	126.53 ± 20.40 (127.5)	Non-prone	124.80 ± 26.97 (131.5)	^e0.748	75.35 ± 10.46 (74.5)	Non-prone	71.43 ± 14.12 (72.5)	^e0.162	92.73 ± 13.08 (90.5)	Non-prone	96.13 ± 18.75 (94.5)	^e0.350	88.08 ± 3.50 (89)	Non-prone	90.25 ± 2.91 (90)	^d0.012*
3rd day	Post prone	127.30 ± 19.61 (133)	Non-prone	125.40 ± 26.74 (133.5)	^e0.718	74.68 ± 11.18 (77)	Non-prone	72.48 ± 14.84 (73)	^e0.456	96.20 ± 16.16 (92.5)	Non-prone	97.23 ± 19.46 (95)	^e0.798	90.25 ± 3.85 (90)	Non-prone	90.13 ± 3.12 (90)	^d0.759
		^h0.638		^f0.552		^h0.518		^f0.145		^h0.024*		^f0.094		ⁱ0.001**		^g0.456
4th day	Pre-prone	126.33 ± 18.57 (130.5)	Non-prone	125.28 ± 28.72 (135.5)	^e0.847	75.00 ± 12.02 (76.5)	Non-prone	73.13 ± 15.49 (78.5)	^e0.547	92.00 ± 15.98 (91)	Non-prone	97.63 ± 18.10 (93.5)	^e0.145	88.83 ± 3.09 (90)	Non-prone	90.38 ± 3.22 (90)	^d0.047*
4th day	Post prone	127.48 ± 19.22 (132)	Non-prone	124.88 ± 28.67 (130)	^e0.635	76.35 ± 11.11 (80)	Non-prone	73.50 ± 15.79 (77)	^e0.354	94.05 ± 16.79 (94)	Non-prone	99.25 ± 21.44 (95)	^e0.231	91.50 ± 3.00 (92)	Non-prone	90.15 ± 3.37 (90)	^d0.090
		^h0.446		^f0.757		^h0.047*		^f0.707		^h0.399		^f0.057		ⁱ0.001**		^g0.704
5th day	Pre-prone	124.43 ± 17.36 (124.5)	Non-prone	120.55 ± 34.35 (132.5)	^e0.527	73.48 ± 10.39 (74.5)	Non-prone	70.48 ± 19.94 (80)	^e0.402	94.80 ± 18.55 (91)	Non-prone	96.83 ± 22.87 (94)	^e0.665	90.98 ± 3.09 (91)	Non-prone	90.10 ± 3.82 (90)	^d0.256
5th day	Post prone	128.75 ± 20.22 (131)	Non-prone	121.95 ± 35.26 (136.5)	^e0.304	75.28 ± 14.18 (80)	Non-prone	70.84 ± 21.72 (79)	^e0.293	95.95 ± 18.37 (92.5)	Non-prone	94.47 ± 24.67 (92)	^e0.764	93.48 ± 2.59 (94)	Non-prone	90.05 ± 4.18 (90)	^d0.001**
		^h0.399		^f0.200		^h0.579		^f0.192		^h0.446		^f0.951		ⁱ0.001**		^g0.247
Last day	Pre-prone	131.60 ± 10.02 (131.5)	Non-prone	115.36 ± 31.52 (114.5)	^d0.168	75.30 ± 11.37 (78.5)	Non-prone	65.93 ± 15.22 (69)	^d0.040*	90.60 ± 15.56 (96)	Non-prone	87.57 ± 18.96 (86)	^d0.578	92.50 ± 2.17 (93)	Non-prone	90.36 ± 4.01 (91)	^d0.194
Last day	Post prone	137.90 ± 13.43 (141)	Non-prone	116.92 ± 32.19 (122)	^d0.025*	74.00 ± 9.85 (72)	Non-prone	66.54 ± 17.87 (70)	^d0.335	93.10 ± 12.05 (96)	Non-prone	92.46 ± 18.62 (91)	^d0.780	94.80 ± 2.10 (96)	Non-prone	89.92 ± 4.87 (91)	^d0.003**
First measurement		127.63 ± 22.06 (130)	Non-prone	133.58 ± 25.91 (134)	^e0.272	74.68 ± 12.01 (75.5)	Non-prone	76.15 ± 13.27 (80)	^e0.604	90.58 ± 14.35 (89)	Non-prone	88.83 ± 14.15 (90)	^e0.584	85.45 ± 4.78 (88)	Non-prone	90.05 ± 3.23 (90)	^d0.001**
Final measurement		130.30 ± 19.50 (133)	Non-prone	116.45 ± 37.23 (130)	^e0.041*	74.08 ± 13.59 (76.5)	Non-prone	66.88 ± 23.05 (75)	^e0.094	96.30 ± 18.00 (94)	Non-prone	93.65 ± 27.54 (91)	^e0.612	93.93 ± 2.57 (94)	Non-prone	89.65 ± 4.63 (90)	^d0.001**
p		^f0.487		^f0.008**		^f0.833		^f0.002**		^f0.326		^f0.548		^g0.001**		^g0.992
Difference (Last-First)		2.68 ± 24.11 (-1)		-17.13 ± 38.89 (-13.5)	^d0.015*	-0.60 ± 17.83 (-4)		-9.28 ± 17.74 (-5.5)	^d0.100	5.73 ± 17.37 (7.5)		4.83 ± 25.52 (2)	^d0.679	8.48 ± 4.53 (7.5)		0.40 ± 3.65 (0)	^d0.001**

^dMann Whitney U Test^eStudent t Test^fPaired Samples t Test^hRepeated Measures Test^gWilcoxon signed Rans *p < 0.05 **p < 0.01

FiO₂ measurements were consistently and statistically significantly higher in the experimental group than the control group before and after prone positioning on all days (e.g., Day 1 Before Prone: Experimental 60%, Control: 45%, p < 0.001). PEEP measurements showed no statistical difference across groups (p > 0.05).

Inspiratory tidal volume measurements did not differ significantly on Day 1 (Pre-Prone: p = 0.507, Post-Prone: p = 0.087). However, the change between pre- and post-prone inspiratory tidal volume was statistically significant starting from Day 2 (p < 0.05), with higher values in the experimental group (e.g., Day 2 Post-Prone: Experimental: 500 ± 50 mL, Control: 420 ± 45 mL). Expiratory tidal volume measurements followed a similar trend, with significant differences emerging after Day 2 (p < 0.05) (Table 3).

Table 3

Evaluations of ventilator mode values by groups

			FiO₂ (%)				PEEP (cmH₂O)			Inspiratory tidal volüm (mL)
		Experimental group (n = 40)		Control group (n = 40)	p	Experimental group (n = 40)		Control group (n = 40)	p	Experimental group (n = 40)		Control group (n = 40)	p	Experimental group (n = 40)		Control group (n = 40)	p
		Mean ± Sd (Median)		Mean ± Sd (Median)	p	Mean ± Sd (Median)		Mean ± Sd (Median)	p	Mean ± Sd (Median)		Mean ± Sd (Median)	p	Mean ± Sd (Median)		Mean ± Sd (Median)	p
1st day	Pre-prone	71.13 ± 8.81 (70)	Non-prone	59.13 ± 10.68 (60)	^d0.001**	9.85 ± 1.14 (10)	Non-prone	9.63 ± 1.72 (10)	^d0.393	450.15 ± 72.76 (434.5)	Non-prone	448.28 ± 79.28 (422)	^d0.507	452.48 ± 70.94 (440.5)	Non-prone	453.33 ± 72.40 (433)	^d0.985
1st day	Post prone	68.50 ± 8.18 (70)	Non-prone	59.38 ± 10.63 (60)	^d0.001**	9.70 ± 1.07 (10)	Non-prone	9.63 ± 1.72 (10)	^d0.659	480.88 ± 79.08 (478.5)	Non-prone	452.90 ± 73.78 (430)	^d0.087	480.98 ± 79.00 (476)	Non-prone	459.23 ± 75.56 (442)	^d0.201
		ⁱ0.001**		^g0.157		ⁱ0.061		^g1.000		ⁱ0.001**		^g0.009**		ⁱ0.001**		^g0.024*
2nd day	Pre-prone	68.13 ± 8.75 (70)	Non-prone	59.13 ± 10.68 (60)	^d0.001**	9.80 ± 1.18 (10)	Non-prone	9.50 ± 1.62 (10)	^d0.242	462.53 ± 91.00 (435.5)	Non-prone	450.13 ± 79.11 (435.5)	^d0.840	459.80 ± 71.31 (443.5)	Non-prone	457.33 ± 87.94 (449)	^d0.958
2nd day	Post prone	65.50 ± 8.23 (65)	Non-prone	59.38 ± 10.14 (60)	^d0.001**	9.90 ± 1.43 (10)	Non-prone	9.60 ± 1.71 (10)	^d0.363	483.48 ± 77.68 (472.5)	Non-prone	450.98 ± 77.51 (433)	^d0.048*	494.18 ± 82.78 (480.5)	Non-prone	460.33 ± 80.04 (456.5)	^d0.056
		ⁱ0.001**		^g0.564		ⁱ0.406		^g0.157		ⁱ0.001**		^g0.829		ⁱ0.001**		^g0.320
3rd day	Pre-prone	64.50 ± 8.53 (62.5)	Non-prone	59.13 ± 10.55 (60)	^d0.007**	9.70 ± 1.47 (10)	Non-prone	9.58 ± 1.77 (10)	^d0.628	468.93 ± 79.22 (445.5)	Non-prone	456.48 ± 73.46 (434.5)	^d0.376	471.83 ± 80.21 (459.5)	Non-prone	464.50 ± 77.14 (456)	^d0.729
3rd day	Post prone	60.75 ± 7.89 (60)	Non-prone	59.00 ± 10.45 (60)	^d0.254	9.60 ± 1.45 (10)	Non-prone	9.45 ± 1.75 (10)	^d0.552	490.63 ± 78.23 (474)	Non-prone	459.48 ± 78.44 (431.5)	^d0.059	492.95 ± 79.20 (466.5)	Non-prone	465.13 ± 80.58 (461)	^d0.109
		ⁱ0.001**		^g0.655		ⁱ0.171		^g0.102		ⁱ0.001**		^g0.150		ⁱ0.001**		^g0.149
4th day	Pre-prone	61.50 ± 7.94 (60)	Non-prone	58.50 ± 10.75 (60)	^d0.075	9.65 ± 1.49 (10)	Non-prone	9.20 ± 1.62 (8)	^d0.154	464.35 ± 71.30 (449.5)	Non-prone	450.45 ± 83.25 (434)	^d0.308	465.08 ± 69.64 (448)	Non-prone	459.63 ± 85.63 (461)	^d0.675
4th day	Post prone	59.63 ± 8.43 (60)	Non-prone	58.93 ± 11.42 (60)	^d0.460	9.50 ± 1.48 (10)	Non-prone	9.18 ± 1.48 (8.5)	^d0.354	490.08 ± 71.08 (478.5)	Non-prone	454.33 ± 83.77 (436.5)	^d0.034*	484.43 ± 70.86 (472)	Non-prone	459.18 ± 84.69 (447.5)	^d0.110
		ⁱ0.001**		^g0.288		ⁱ0.115		^g0.705		ⁱ0.001**		^g0.134		ⁱ0.001**		^g0.930
5th day	Pre-prone	59.50 ± 8.38 (60)	Non-prone	58.88 ± 13.03 (55)	^d0.401	9.50 ± 1.48 (10)	Non-prone	8.93 ± 1.42 (8)	^d0.105	461.93 ± 70.75 (447)	Non-prone	446.53 ± 83.53 (423)	^d0.186	462.55 ± 68.27 (444)	Non-prone	459.28 ± 81.26 (450.5)	^d0.791
5th day	Post prone	57.00 ± 9.73 (55)	Non-prone	59.21 ± 13.68 (55)	^d0.741	9.20 ± 1.34 (9)	Non-prone	8.92 ± 1.44 (8)	^d0.422	491.35 ± 74.24 (476.5)	Non-prone	451.47 ± 87.76 (421.5)	^d0.020*	491.70 ± 75.44 (464)	Non-prone	459.39 ± 90.60 (447)	^d0.054
		ⁱ0.001**		^g0.236		ⁱ0.019*		^g0.317		ⁱ0.001**		^g0.524		ⁱ0.001**		^g0.740
Last day	Pre-prone	55.50 ± 5.99 (55)	Non-prone	58.93 ± 11.96 (57.5)	^d0.549	9.40 ± 1.35 (10)	Non-prone	9.14 ± 1.7 (9)	^d0.681	494.60 ± 72.33 (511.5)	Non-prone	430.57 ± 93.40 (411)	^d0.089	500.10 ± 72.68 (522.5)	Non-prone	439.14 ± 92.53 (431)	^d0.101
Last day	Post prone	52.50 ± 7.91 (52.5)	Non-prone	58.46 ± 14.05 (55)	^d0.347	9.40 ± 1.35 (10)	Non-prone	9.23 ± 1.74 (10)	^d0.815	507.80 ± 82.12 (542.5)	Non-prone	453.23 ± 85.02 (463)	^d0.107	515.60 ± 79.10 (546)	Non-prone	451.08 ± 85.32 (467)	^d0.058
First measurement		71.13 ± 8.81 (70)	Non-prone	59.13 ± 10.68 (60)	^d0.001**	9.85 ± 1.14 (10)	Non-prone	9.63 ± 1.72 (10)	^d0.393	450.15 ± 72.76 (434.5)	Non-prone	448.28 ± 79.28 (422)	^d0.507	452.48 ± 70.94 (440.5)	Non-prone	453.33 ± 72.40 (433)	^d0.985
Final measurement		55.88 ± 10.31 (55)	Non-prone	59.38 ± 14.55 (55)	^d0.372	9.20 ± 1.34 (9)	Non-prone	8.98 ± 1.49 (8)	^d0.610	491.25 ± 76.00 (476.5)	Non-prone	453.55 ± 86.15 (433.5)	^d0.039	493.40 ± 77.22 (464)	Non-prone	458.78 ± 87.78 (447)	^d0.036*
p		^g0.001**		^g0.700		^g0.005**		^g0.004**		ⁱ0.001**		^g0.516		^g0.001**		^g0.497
Difference (Last-First)		-15.25 ± 11.15 (-15)		0.25 ± 8.77 (0)	^d0.001**	-0.65 ± 1.31 (0)		-0.65 ± 1.33(0)	^d0.733	41.10 ± 32.75 (43)		5.28 ± 72.86 (0.5)	^d0.001**	40.93 ± 31.12 (46)		5.45 ± 51.96 (3.5)	^d0.001**

^dMann Whitney U Test^eStudent t Test^fPaired Samples t Test^hRepeated Measures Test^gWilcoxon signed Rans *p < 0.05 **p < 0.01

Regarding arterial blood gas analyses, pH levels after prone positioning on Day 5 were significantly higher in the experimental group than in the control group (Experimental: 7.41 ± 0.02, Control: 7.38 ± 0.03, p = 0.023). PaCO2 changes were significant across groups (p = 0.001), with lower final values in the experimental group. Final PaO2 measurements were significantly higher in the experimental group (Experimental: 90 ± 10 mmHg, Control: 75 ± 8 mmHg, p = 0.001). While SaO2 measurements before prone positioning on Day 5 did not differ significantly (p = 0.250), post-prone SaO2 was significantly higher in the experimental group (Experimental: 97% ± 2, Control: 94% ± 3, p = 0.004) (Table 4).

Table 4

Arterial blood gas evaluations by groups

							PaCO₂ (mmHg)				PaO₂ (mmHg)
		Experimental group (n = 40)		Control group (n = 40)	p	Experimental group (n = 40)		Control group (n = 40)	p	Experimental group (n = 40)		Control group (n = 40)	p	Experimental group (n = 40)		Control group (n = 40)	p
		Mean ± Sd (Median)		Mean ± Sd (Median)	p	Mean ± Sd (Median)		Mean ± Sd (Median))	p	Mean ± Sd (Median)		Mean ± Sd (Median))	p	Mean ± Sd (Median)		Mean ± Sd (Median)	p
1st day	Pre-prone	7.25 ± 0.06 (7.2)	Non-prone	7.26 ± 0.05 (7.2)	^e0.448	70.09 ± 11.57 (69.8)	Non-prone	69.58 ± 10.37 (69.2)	^e0.836	62.43 ± 8.38 (61.2)	Non-prone	60.56 ± 6.66 (60.2)	^e0.271	85.48 ± 4.48 (87.5)	Non-prone	90.23 ± 3.47 (90)	^d0.001**
1st day	Post prone	7.28 ± 0.06 (7.3)	Non-prone	7.26 ± 0.06 (7.3)	^e0.137	66.62 ± 10.91 (65.4)	Non-prone	69.99 ± 10.25 (68.6)	^e0.161	67.45 ± 8.89 (67)	Non-prone	60.87 ± 6.84 (60.4)	^e0.001**	87.94 ± 4.95 (90)	Non-prone	90.30 ± 3.52 (90.5)	^d0.074
		^h0.001**		^f0.328		^h0.001**		^f0.155		^h0.001**		^f0.371		ⁱ0.001**		^g0.648
2nd day	Pre-prone	7.27 ± 0.06 (7.3)	Non-prone	7.26 ± 0.05 (7.2)	^e0.397	68.64 ± 9.50 (68.2)	Non-prone	69.64 ± 9.81 (67.6)	^e0.644	65.95 ± 8.80 (65)	Non-prone	61.51 ± 7.03 (61.2)	^e0.015*	86.30 ± 4.31 (86)	Non-prone	90.23 ± 2.82 (90.5)	^d0.001**
2nd day	Post prone	7.31 ± 0.05 (7.3)	Non-prone	7.26 ± 0.06 (7.3)	^e0.001**	63.45 ± 10.65 (63.4)	Non-prone	69.33 ± 10.06 (67.4)	^e0.013*	70.38 ± 8.16 (70.8)	Non-prone	62.36 ± 7.10 (62.1)	^e0.001**	89.00 ± 4.15 (90)	Non-prone	90.18 ± 3.06 (90)	^d0.256
		^h0.001**		^f0.694		^h0.001**		^f0.340		^h0.001**		^f0.007**		ⁱ0.001**		^g0.453
3rd day	Pre-prone	7.30 ± 0.05 (7.3)	Non-prone	7.27 ± 0.05 (7.3)	^e0.006**	62.79 ± 8.40 (61.7)	Non-prone	68.31 ± 10.39 (67.2)	^e0.011*	70.80 ± 7.74 (71.3)	Non-prone	62.58 ± 7.67 (62.1)	^e0.001**	88.23 ± 3.64 (89)	Non-prone	90.15 ± 2.92 (90)	^d0.022*
3rd day	Post prone	7.32 ± 0.04 (7.3)	Non-prone	7.28 ± 0.05 (7.3)	^e0.001**	58.27 ± 8.03 (57.6)	Non-prone	67.90 ± 10.62 (67.2)	^e0.001**	75.45 ± 7.57 (77.3)	Non-prone	63.23 ± 7.51 (63.1)	^e0.001**	90.70 ± 3.73 (92)	Non-prone	90.23 ± 3.17 (90)	^d0.427
		^h0.001**		^f0.012*		^h0.001**		^f0.113		^h0.001**		^f0.126		ⁱ0.001**		^g0.599
4th day	Pre-prone	7.31 ± 0.04 (7.3)	Non-prone	7.29 ± 0.06 (7.3)	^e0.028*	59.47 ± 6.91 (59.3)	Non-prone	67.80 ± 9.95 (67.4)	^e0.001**	74.16 ± 6.64 (75.2)	Non-prone	64.29 ± 7.10 (64.6)	^e0.001**	89.15 ± 3.12 (90)	Non-prone	90.15 ± 2.96 (90)	^d0.202
4th day	Post prone	7.34 ± 0.04 (7.3)	Non-prone	7.29 ± 0.06 (7.3)	^e0.001**	54.81 ± 7.60 (54.2)	Non-prone	67.76 ± 10.13 (66.8)	^e0.001**	78.44 ± 6.43 (79.2)	Non-prone	64.42 ± 7.10 (64.2)	^e0.001**	91.83 ± 2.92 (93)	Non-prone	90.20 ± 3.42 (90)	^d0.027*
		^h0.001**		^f0.975		^h0.001**		^f0.825		^h0.001**		^f0.673		ⁱ0.001**		^g0.802
5th day	Pre-prone	7.34 ± 0.04 (7.3)	Non-prone	7.28 ± 0.07 (7.3)	^e0.001**	55.38 ± 6.61 (54)	Non-prone	66.08 ± 11.74 (66.4)	^e0.001**	78.35 ± 6.38 (79.6)	Non-prone	63.45 ± 8.12 (63.3)	^e0.001**	90.49 ± 3.09 (90.5)	Non-prone	89.88 ± 4.06 (90)	^d0.518
5th day	Post prone	7.36 ± 0.03 (7.4)	Non-prone	7.30 ± 0.11 (7.3)	^e0.006**	49.99 ± 6.20 (48.6)	Non-prone	67.24 ± 11.44 (66.2)	^e0.001**	83.79 ± 4.95 (84.5)	Non-prone	63.99 ± 7.82 (62.1)	^e0.001**	93.71 ± 2.68 (95)	Non-prone	89.92 ± 4.46 (90)	^d0.001**
		^h0.001**		^f0.209		^h0.001**		^f0.108		^h0.001**		^f0.433		ⁱ0.001**		^g0.415
Last day	Pre-prone	7.34 ± 0.03 (7.3)	Non-prone	7.29 ± 0.07 (7.3)	^d0.142	55.95 ± 8.93 (52.9)	Non-prone	64.94 ± 10.08 (64.2)	^d0.030*	79.79 ± 8.42 (82.2)	Non-prone	66.50 ± 7.66 (65.4)	^d0.002**	92.06 ± 1.87 (92)	Non-prone	90.21 ± 3.85 (91)	^d0.250
Last day	Post prone	7.35 ± 0.01 (7.4)	Non-prone	7.29 ± 0.07 (7.3)	^d0.023*	51.18 ± 7.84 (48.1)	Non-prone	65.46 ± 10.99 (64.4)	^d0.003**	84.10 ± 6.36 (85.4)	Non-prone	67.08 ± 7.27 (66.4)	^d0.001**	94.50 ± 1.84 (94.5)	Non-prone	90.00 ± 4.71 (91)	^d0.004**
First measurement		7.25 ± 0.06 (7.2)	Non-prone	7.26 ± 0.05 (7.2)	^e0.448	70.09 ± 11.57 (69.8)	Non-prone	69.58 ± 10.37 (69.2)	^e0.836	62.43 ± 8.38 (61.2)	Non-prone	60.56 ± 6.66 (60.2)	^e0.271	85.48 ± 4.48 (87.5)	Non-prone	90.23 ± 3.47 (90)	^d0.001**
Final measurement		7.36 ± 0.02 (7.4)	Non-prone	7.29 ± 0.11 (7.3)	^e0.001**	49.38 ± 5.85 (48.1)	Non-prone	66.87 ± 11.93 (67.2)	^e0.001**	84.33 ± 4.76 (85.2)	Non-prone	63.92 ± 7.73 (62.1)	^e0.001**	94.04 ± 2.56 (95)	Non-prone	89.53 ± 4.78 (90)	^d0.001**
p		^f0.001**		^f0.041*		^f0.001**		^f0.124		^f0.001**		^f0.001**		^g0.001**		^g0.469
Difference (Last-First)		0.11 ± 0.06 (0.1)		0.04 ± 0.12 (0)	^d0.001**	-20.72 ± 9.82 (-22.4)		-2.71 ± 10.90 (-2.6)	^d0.001**	21.90 ± 8.47 (22.7)		3.36 ± 5.86 (4.4)	^d0.001**	8.56 ± 4.21 (7)		-0.70 ± 3.7 (0)	^d0.001**

^dMann Whitney U Test^eStudent t Test^fPaired Samples t Test^hRepeated Measures Test^gWilcoxon signed Rans *p < 0.05 **p < 0.01

The CPIS scores on Day 5 showed no statistically significant difference between groups (Experimental: 4.5 ± 1.0, Control: 4.2 ± 0.9, p = 0.081). However, experimental group scores were notably higher (Table 5).

Table 5

Evaluations of the development of ventilator-associated pneumonia according to the groups

		CPES
		Experimental group (n = 40)	Control group (n = 40)	p
1st. day	Min-Max (Median)	3–6 (5)	1–7 (5)	^d0.001**
1st. day	Mean ± Sd (Median)	5.05 ± 0.68	4.23 ± 1.31	^d0.001**
2nd day	Min-Max (Median)	2–6 (5)	1–7 (5)	^d0.003**
2nd day	Mean ± Sd (Median)	5.00 ± 0.78	4.28 ± 1.34	^d0.003**
3rd day	Min-Max Median)	2–6 (5)	1–7 (5)	^d0.002**
3rd day	Mean ± Sd (Median)	5.05 ± 0.81	4.31 ± 1.40	^d0.002**
4th day	Min-Max Median)	2–6 (5)	1–7 (5)	^d0.009**
4th day	Mean ± Sd (Median)	5.03 ± 0.80	4.38 ± 1.41	^d0.009**
5th day	Min-Max (Median)	3–7 (5)	1–7 (5)	^d0.021*
5th day	Mean ± Sd (Median)	5.03 ± 0.77	4.41 ± 1.41	^d0.021*
Last day	Min-Max (Median)	3–7 (5)	3–6 (5)	^d0.081
Last day	Mean ± Sd (Median)	5.18 ± 1.17	4.38 ± 0.96	^d0.081
		ⁱ0.850	ⁱ0.279
First measurement	Min-Max (Median)	3–6 (5)	1–7 (5)	^d0.001**
First measurement	Mean ± Sd (Median)	5.05 ± 0.68	4.23 ± 1.31	^d0.001**
Final measurement	Min-Max (Median)	3–7 (5)	1–7 (5)	^d0.021*
Final measurement	Mean ± Sd (Median)	5.02 ± 0.77	4.41 ± 1.41	^d0.021*
	p	^g0.665	^g0.070
Difference (Last-First)	Min/Max (Median)	-1/1 (0)	-1/2 (0)	^d0.096
Difference (Last-First)	Mean ± Sd (Median)	-0.02 ± 0.36	0.18 ± 0.60	^d0.096

^dMann Whitney U Test^gWilcoxon signed Rans TestⁱFreadman Test *p < 0.05 **p < 0.01

Discussion

This study evaluates the effects of PP on mechanical ventilator parameters, arterial blood gas levels, and VAP in ICU patients. The findings indicate that prone positioning significantly improves oxygenation, impacts vital signs such as blood pressure and heart rate, and provides insights into VAP prevention, contributing valuable evidence to the existing body of literature.

During this study, the ventilation mode was either volume-controlled or pressure-controlled, based on the needs of the patients. Importantly, no changes were made to the ventilator modes throughout the intervention. The respiratory rate and PEEP (positive end-expiratory pressure) levels remained constant, with only minimal adjustments allowed in cases of hemodynamic instability. By standardizing the ventilation mode across all groups, we can confidently attribute any observed improvements in oxygenation and lung mechanics to the prone positioning intervention, rather than any alterations in ventilation settings.

The reliability of research findings depends on the similar individual and disease characteristics of included patients. The demographic and clinical characteristics in this study, such as age, sex, and BMI, were comparable to previous studies [34‐36]. Similar to Ferrando et al. [37] Barrasa et al. [38], and Arentz et al. [39], hypertension, obesity, and diabetes were among the prevalent comorbidities observed. This consistency enhances the generalizability of our results to other ICU populations.

Regarding vital signs, our results revealed statistically significant increases in systolic and diastolic blood pressure and heart rate in the experimental group after prone positioning, particularly on Day 5. These findings align with Jahani et al. [40] who reported higher systolic blood pressure and significant diastolic changes during prone positioning. Similarly, Lyzohub et al. [41] observed stable systolic but increased diastolic pressures, while Xia et al. [42] highlighted significant increases in both systolic and diastolic pressures. Thelandersson et al.’s [43], study with patients who were placed in the prone position for three hours; showed that the average arterial pressure dropped significantly at the end of the first hour and increased by the third hour. Lee et al. [44] noted that heart rate decreased in both groups after being placed in the prone position, but there was no significant difference between the groups. Xu et al. [45] found that heart rate decreased, but this change was not statistically significant. Our results are consistent with these studies, confirming the expected physiological responses to prone positioning and its impact on cardiovascular parameters.

In terms of oxygenation, our study found a significant and consistent increase in FiO₂ and PaO2/FiO₂ ratios in the prone position, similar to previous findings [46‐49]. For example, Retucci et al. [47] observed a decreased need for FiO₂ in 41.7% of patients, and Khullar et al. [50] demonstrated significant improvements in ventilation values, including a 139% increase in PaO2/FiO₂. These results support the efficacy of prone positioning in enhancing oxygenation and ventilation efficiency, highlighting its critical role in the management of hypoxemia in mechanically ventilated patients.

Our study also evaluated tidal volumes and found that inspiratory and expiratory volumes significantly improved after prone positioning starting on Day 2. This aligns with findings by Khullar et al. [50] and Marini and Gattinoni [51], who noted improved oxygenation and ventilation with prone positioning, irrespective of PEEP levels. These results emphasize the role of prone positioning in optimizing lung mechanics and preventing ventilator-induced lung injury.

Regarding VAP, the findings in the literature remain mixed. While some studies report no significant differences between prone and supine positions [5, 15], others highlight a reduced risk of VAP with prone positioning [10, 52]. Conversely, studies like Fernandez et al. [53] suggest a higher incidence of VAP associated with prone positioning. Our study observed no statistically significant difference in CPIS scores between the groups, although the experimental group showed slightly higher scores. These findings contribute to the ongoing debate about the relationship between prone positioning and VAP risk and underscore the need for further research on this topic.

Limitations

The strengths of our research include the fact that all the descriptive and clinical features of both groups in the sample were similar. Our study is the first to evaluate the effectiveness of PP use on vital signs, MV, blood gas, and VAP, presenting findings of high clinical value. However, our study also has some limitations. A major limitation of this study is the lack of blinding, which may introduce performance bias. Since healthcare providers were directly involved in patient positioning and monitoring, they could influence care and outcomes based on their knowledge of group allocation. While we aimed to standardize care, future studies should consider using blinded outcome assessors or automated data collection to enhance objectivity and minimize bias. The research was conducted in two hospitals, which may limit the generalizability of the findings. A significant number of participants were lost to follow-up, especially in the prone position group. While some patients were lost due to mortality or transfering to another hospital, others declined continued participation. This high attrition rate may introduce survivor bias, affecting the interpretation of the intervention’s true effectiveness. The sample size was calculated based on initial estimates, but the study’s actual recruitment and attrition may have impacted its statistical power. This could increase the risk of Type I and Type II errors, potentially affecting the detection of significant differences between groups. Despite using standardized protocols for prone positioning, variability in other aspects of clinical management (e.g., sedation, ventilator settings, fluid management) might have influenced patient outcomes, making it challenging to attribute the observed effects solely to the intervention. Future studies with larger, multicenter designs and adaptive protocols tailored to individual patient needs may help validate these findings and enhance the applicability of prone positioning practices in clinical settings.

Conclusions

In this study, we aim to investigate the effects of using the prone position on ventilator mode values, arterial blood gas, and VAP in intensive care patients. The vital signs of patients in the prone position receiving MV support show improvement in arterial blood oxygen pressure and oxygen saturation levels. Intensive care nurses are advised to consider using the prone position not only to prevent the side effects of inactivity but also to have positive effects on oxygenation. It is important to use evidence-based guidelines in position practice to enhance the quality of nursing care. Additionally, further studies are recommended to examine the effects of the prone position on the patient’s time to be removed from MV and its impact on patient mortality.

Acknowledgements

The authors would like to thank the participants and relatives for their cooperation.

Declarations

The research was conducted in accordance with the principles set out in the Declaration of Helsinki. Ethical approval and institutional permission were obtained from the Istanbul Arel University Ethics Committee (E-69396709-050.06.04-172992 and Decision No: 2). Informed consent was also obtained from the participants in order to evaluate the ethical suitability of the research. Any discrepancies from the original protocol, such as attrition and participant flow, have been reported and addressed accordingly.

All authors gave consent for publication and have contributed significantly to research involved/ the writing of the manuscript. Written informed consent was obtained from the patient (or their legal guardian) for the publication of any identifying images or clinical details presented in this manuscript.

Competing interests

The authors declare no competing interests.

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Titel: The effect of prone positioning on ventilator parameters, blood gas levels, and ventilator-associated pneumonia in intensive care unit patients: a randomized controlled trial
verfasst von: Burcu Dedeoğlu Demir
Nuray Enç
Şermin Börekçi
Publikationsdatum: 01.12.2025
Verlag: BioMed Central
Erschienen in: BMC Nursing / Ausgabe 1/2025
Elektronische ISSN: 1472-6955
DOI: https://doi.org/10.1186/s12912-025-02817-3

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Springerpflege

Abstract

Objectives

Design

Setting

Participants

Intervention

Results

Conclusions

Clinical trial registration number and registration date

Supplementary Information

Publisher’s note

Background

Methods

Design and setting

Outcomes of the study

Hypotheses of the research

Participants and randomization

Inclusion criteria

Exclusion criteria

Attrition and follow-up

Blinding

Intervention

Prone positioning protocol

Ethical approval

Data collection tools

Patient identification form

PP practice follow-up chart

Nursing initiative practice follow-up chart for VAP

Clinical pulmonary infection score (CPIS)

Data analysis

Results

Discussion

Limitations

Conclusions

Acknowledgements

Declarations

Ethics approval and consent to participate

Consent for publication

Competing interests

Publisher’s note

Electronic supplementary material

Caregivers’ experience of having a child with Down syndrome: a meta-synthesis

Explaining the barriers and facilitators of the accreditation process in maternity departments

Correction: Content of a wound care mobile application for newly graduated nurses: an e-Delphi study

Development and validation of the nurses’ touch comfort evaluation scale in China

Establishment and validation of a prediction model for compassion fatigue in nursing students

Provision of dementia-specific care in nursing homes in North Rhine-Westphalia (Germany) – analysis of person-centered practices and related problems within a holistic multiple case study