A pilot study using the LASCA technique to analyze stress using heart rate variability.

In the quest to uncover biological cues that help explain organic changes brought on by an external stimulus, like stress, new technologies have become necessary. The Laser Speckle Contrast Analysis (LASCA) approach is one of these technologies that may be used to analyze biological data, including respiratory rate (RR) intervals, and then use the results to determine heart rate variability (HRV Thus, to evaluate the stress brought on by physical activity, this study used the LASCA approach. A stress induction procedure involving physical exertion was employed, and the results were compared to other established techniques (cortisol analysis and ECG signal) to verify the LASCA methodology as a tool for measuring HRV and stress. The study sample comprised 27 willing participants. The technique involving LASCA allowed for the non-invasive (non-contact) acquisition of HRV and the study of stress. Furthermore, it made it possible to gather pertinent data, such as recognizing modifications to the thermoregulation, peripheral vasomotor tonus, and renin-angiotensin-aldosterone systems that were brought on by elevated stress and, as a result, variations in HRV readings.

Psycho-physio-neurological correlates of qualitative attention, emotion and flow experiences in a close-to-real-life extreme sports situation: low- and high-altitude slackline walking.

It has been indicated that extreme sport activities result in a highly rewarding experience, despite also providing fear, stress and anxiety. Studies have related this experience to the concept of flow, a positive feeling that individuals undergo when they are completely immersed in an activity. However, little is known about the exact nature of these experiences, and, there are still no empirical results to characterize the brain dynamics during extreme sport practice. This work aimed at investigating changes in psychological responses while recording physiological (heart rate-HR, and breathing rate-BR) and neural (electroencephalographic-EEG) data of eight volunteers, during outdoors slackline walking in a mountainous environment at two different altitude conditions (1 m-low-walk- and 45 m-high-walk-from the ground). Low-walk showed a higher score on flow scale, while high-walk displayed a higher score in the negative affect aspects, which together point to some level of flow restriction during high-walk. The order of task performance was shown to be relevant for the physiological and neural variables. The brain behavior during flow, mainly considering attention networks, displayed the stimulus-driven ventral attention network-VAN, regionally prevailing (mainly at the frontal lobe), over the goal-directed dorsal attention network-DAN. Therefore, we suggest an interpretation of flow experiences as an opened attention to more changing details in the surroundings, i.e., configured as a 'task-constantly-opened-to-subtle-information experience', rather than a 'task-focused experience'.

Exploring diaphragmatic response to high-flow nasal cannula in patients with COVID-19 pneumonia using ultrasound: a proof of concept study.

BACKGROUND: Recent studies have highlighted the recognition of diaphragmatic dysfunction as a significant factor contributing to respiratory disturbances in severely ill COVID-19 patients. In the field of noninvasive respiratory support, high-flow nasal cannula (HFNC) has shown effectiveness in relieving diaphragm dysfunction. This study aims to investigate the diaphragmatic response to HFNC in patients with COVID-19 pneumonia by utilizing ultrasound. METHODS: This retrospective study was conducted in a medical-surgical intensive care unit (ICU) at a tertiary care center in Buenos Aires, Argentina (Sanatorio de Los Arcos) over a 16-month period (January 2021-June 2022). The study included patients admitted to the ICU with a diagnosis of COVID-19 pneumonia who were deemed suitable candidates for HFNC therapy by the attending physician. Diaphragm ultrasound was conducted, measuring diaphragmatic excursion (DE) both before and during the utilization of HFNC for these patients. RESULTS: A total of 10 patients were included in the study. A statistically significant decrease in respiratory rate was observed with the use of HFNC (p = 0.02), accompanied by a significant increase in DE (p = 0.04). CONCLUSION: HFNC leads to a reduction in respiratory rate and an increase in DE as observed by ultrasound in patients with COVID-19 pneumonia, indicating promising enhancements in respiratory mechanics. However, further research is required to validate these findings.

Identifying physiological indicators of the cognitive, thermal, and combined (cognitive-thermal) stress conditions.

Physiologically based stress detection systems have proven to be effective in identifying different stress conditions in the body to determine the source of stress and be able to counteract it. However, some stress conditions have not been widely studied, including thermal stress, cognitive stress, and combined (thermal-cognitive) stress conditions, which are frequently encountered in work or school environments. In order to develop systems to detect and differentiate these conditions, it is necessary to identify the physiological indicators that characterize each of them. The present research aims to identify which physiological indicators (heart rate, respiratory rate, galvanic skin response, and local temperature) could differentiate different stress conditions (no-stress, cognitive stress, thermal stress, and combined (thermal-cognitive) stress conditions). Thirty participants were exposed to cognitive, thermal, and combined stress sources while recording their physiological signals. The findings indicate that both mean heart rate and mean galvanic skin response identify moderate thermal and cognitive stress conditions as distinct from a no-stress condition, yet they do not differentiate between the two stress conditions. Additionally, heart rate uniquely identifies the cognitive-thermal stress condition, effectively distinguishing this combined stress condition from the singular stress conditions and the no-stress condition. Mean local temperature specifically signals thermal stress conditions, whereas mean respiratory rate accurately identifies cognitive stress conditions, with both indicators effectively separating these conditions from each other and from the no-stress condition. This is the first basis for differentiating thermal and cognitive stress conditions through physiological indicators.

Potentiation of the depressant effect of alcohol by flunitrazepam in rats: an electrocorticographic, respiratory and electrocardiographic study.

Alcohol, a widely commercialized psychotropic drug, and the benzodiazepine Flunitrazepam, an anxiolytic widely prescribed for patients with anxiety and insomnia problems, are well known drugs and both act on the central nervous system. The misuse and the association of these two drugs are public health concerns in several countries and could cause momentary, long-lasting and even lethal neurophysiological problems due to the potentiation of their adverse effects in synergy. The present study observed the result of the association of these drugs on electrophysiological responses in the brain, heart, and respiratory rate in Wistar rats. 8 experimental groups were determined: control, one alcohol group (20% at a dose of 1 ml/100 g VO), three Flunitrazepam groups (doses 0.1; 0.2 and 0.3 mg/kg) and three alcohol-Flunitrazepam groups (20% at a dose of 1 ml/100 g VO of alcohol, combined with 0.1; 0.2 and 0.3 mg/kg of Flunitrazepam, respectively). The results showed that there was a more pronounced reduction in alpha and theta wave power in the alcohol-Flunitrazepam groups, a decrease in the power of beta oscillations and greater sedation. There was a progressive decrease in respiratory rate linked to the increase of Flunitrazepam dose in the alcohol-Flunitrazepam associated administration. It was observed alteration in heart rate and Q-T interval in high doses of Flunitrazepam. Therefore, we conclude that the association alcohol-Flunitrazepam presented deepening of depressant synergistic effects according to the increase in the dose of the benzodiazepine, and this could cause alterations in low frequency brain oscillations, breathing, and hemodynamics of the patient.

Association between early manifestations of infection or sepsis and prognosis in a high complexity hospital in the city of Medellín.

OBJECTIVE: To identify the first symptoms and signs of patients with suspected infection or sepsis and their association with the composite outcome of admission to the Intensive Care Unit (ICU) or mortality. DESIGN: Prospective cohort study between June 2019 and March 2020. SETTING: Hospital Universitario San Vicente Fundación, Colombia. PATIENTS: Over 18 years of age with suspicion or confirmation of sepsis, which required hospitalization. INTERVENTIONS: None. MAIN VARIABLES OF INTEREST: Symptoms and signs associated with infection, with their time of evolution, specified in the study. RESULTS: From 1005 eligible patients, 261 were included. After multivariable adjustment with a logistic regression model, the main factors for ICU admission or mortality were heart rate (OR 1.04 with 95% CI 1.04-3.7), respiratory rate (OR 1.19 with 95% CI 1.0-1.4) and capillary refill time (OR 3.4 with 95% CI 1.9-6.1). CONCLUSIONS: Heart rate, respiratory rate, and capillary refill may behave as early predictors of ICU admission and mortality in cases of sepsis.

Effects of the use of a cocoon on the autonomic, motor, and regulatory systems in preterm newborns: Randomized clinical trial.

INTRODUCTION: The wrapping of the newborn in an orthopedic tubular mesh, simulating a cocoon, can allow the infant to regain the feeling of security and stability experienced in the uterus given that the movement of one of the parts of the body exerts tactile and pressure variation in others. OBJECTIVE: We aimed to evaluate the influence of an orthopedic tubular mesh, simulating a cocoon, in therapeutic positioning, on the variables of the autonomous, motor, and regulatory systems of preterm newborns. METHODS: A controlled and randomized clinical trial was conducted with preterm newborns positioned in dorsal decubitus and divided into two groups: (a) cocoon - newborns covered with an orthopedic tubular mesh, and (b) control - newborns positioned according to the sector's routine and without the use of an orthopedic mesh. During the follow-up, each newborn was placed in the position for 30 min and was recorded for a total of 2 min, once at the beginning and again at the end of the observation period. Variables related to the autonomous system (heart rate, respiratory rate, and peripheral oxygen saturation), motor system (general movements), and regulatory system (Neonatal Infant Pain Scale) were evaluated before and after the intervention. The videos were evaluated by a researcher blind to the purpose of the study, and the resulting data were analyzed using SPSS. RESULTS: Of the 40 preterm newborns evaluated (32.5 ± 1.83 weeks), 21 were female, and 20 were allocated to the cocoon group. The variables related to the autonomous, motor, and regulatory systems remained unchanged following the positioning in the cocoon, as compared to the typical positioning employed in the neonatal unit. CONCLUSION: The simulation of a cocoon, utilizing an orthopedic tubular mesh, when applied to preterm newborns admitted to a neonatal intensive care unit can contribute to maintaining low levels of stress, without altering variables of the autonomous, motor, and regulatory systems.

Respiratory activity during seizures induced by pentylenetetrazole.

This study investigated the respiratory activity in adult Wistar rats across different behavioral seizure severity induced by pentylenetetrazole (PTZ). Animals underwent surgery for electrodes implantation, allowing simultaneous EEG and diaphragm EMG (DIAEMG) recordings and the respiratory frequency and DIAEMG amplitude were measured. Seizures were acutely induced through PTZ injection and classified based on a pre-established score, with absence-like seizures (spike wave discharge (SWD) events on EEG) representing the lowest score. The respiratory activity was grouped into the different seizure severities. During absence-like and myoclonic jerk seizures, the breathing frequency decreased significantly (∼50% decrease) compared to pre- and post-ictal periods. Pronounced changes occurred with more severe seizures (clonic and tonic) with periods of apnea, especially during tonic seizures. Apnea duration was significantly higher in tonic compared to clonic seizures. Notably, during PTZ-induced tonic seizures the apnea events were marked by tonic DIAEMG contraction (tonic-phase apnea). In the majority of animals (5 out of 7) this was a fatal event in which the seizure-induced respiratory arrest preceded the asystole. In conclusion, we provide an assessment of the respiratory activity in the PTZ-induced acute seizures and showed that breathing dysfunction is more pronounced in seizures with higher severity.

Strategies to alleviate heat stress on performance and physiological parameters in feedlot-finished cattle under heat stress conditions. A systematic review-meta-analysis.

Strategies to alleviate heat stress on live performance - dry matter intake (DMI), average daily gain (ADG), and feed conversion efficiency (FCE) - and on physiological parameters - respiratory rate (RR) and panting score (PS) - of feedlot-finished cattle were evaluated by systematic review-meta-analysis. Using the PICO framework were identified 3813 records, with 31 publications and 6729 cattle being considered in the meta-analysis (MA). The comparison most reported was sun vs. shade (n = 24 publications), followed by shade vs. shade (area per animal and effectivity in reduce solar load) (n = 7 publications) and sun vs. sprinkling (n = 4 publications). Cattle with access to shade with total reduction in solar load improved ADG (p = 0.008) and FCE (p = 0.024), and reduced RR (p < 0.001) compared to unshaded animals. Cattle with access to shade with a height between 3 and 4 m increased ADG (p < 0.001), tended to improve FCE (p = 0.054), and reduced RR (p < 0.001) compared to unshaded animals. An area of shade from 2 to 4 m2/animal increased ADG (p = 0.002), and higher than 4 m2/animal reduced RR (p < 0.001) compared to unshaded animals. Animals that received sprinkling volume below 1 L/animal/min improved ADG (p = 0.008) compared to unshaded animals. Cattle with access to shade with a high area per animal improved DMI (p = 0.023) and ADG (p < 0.001) compared to animals with a low area. In univariate meta-regression, it was observed that the variables significantly (P < 0.05) influencing DMI were THI category; influencing ADG were cattle gender, THI category, and coat color; influencing FCE were cattle age and hemisphere; and influencing RR were country, THI category and climate. Performance and physiological parameters of feedlot-finished cattle under heat stress depend on animal and environmental characteristics.

Hypoxic peripheral chemoreflex stimulation-dependent cardiorespiratory coupling is decreased in swimmer athletes.

Swimmer athletes showed a decreased ventilatory response and reduced sympathetic activation during peripheral hypoxic chemoreflex stimulation. Based on these observations, we hypothesized that swimmers develop a diminished cardiorespiratory coupling due to their decreased hypoxic peripheral response. To resolve this hypothesis, we conducted a study using coherence time-varying analysis to assess the cardiorespiratory coupling in swimmer athletes. We recruited 12 trained swimmers and 12 control subjects for our research. We employed wavelet time-varying spectral coherence analysis to examine the relationship between the respiratory frequency (Rf ) and the heart rate (HR) time series during normoxia and acute chemoreflex activation induced by five consecutive inhalations of 100% N2 . Comparing swimmers to control subjects, we observed a significant reduction in the hypoxic ventilatory responses to N2 in swimmers (0.012 ± 0.001 vs. 0.015 ± 0.001 ΔVE /ΔVO2 , and 0.365 ± 0.266 vs. 1.430 ± 0.961 ΔVE /ΔVCO2 /ΔSpO2 , both p < 0.001, swimmers vs. control, respectively). Furthermore, the coherence at the LF cutoff during hypoxia was significantly lower in swimmers compared to control subjects (20.118 ± 3.502 vs. 24.935 ± 3.832 area under curve [AUC], p < 0.012, respectively). Our findings strongly indicate that due to their diminished chemoreflex control, swimmers exhibited a substantial decrease in cardiorespiratory coupling during hypoxic stimulation.

Adaptive dynamics of indigenous sheep in Canary Islands, Spain: A machine learning approach.

The objective of the study was to characterize the adaptive profile of Ibero-American sheep of the Canaria breed, evaluating the possible changes in thermoregulatory responses and coat characteristics to which the animals are exposed in the different seasons of the year. Data collected over a period of 12 months were analyzed, with information being observed in the interval of 15 days of each month, in 23 adult ewes kept in an intensive breeding system. The rectal temperature (RT) of Canaria ewes was higher (P < 0.001) in the summer and spring seasons. In contrast, the respiratory rate (RR) of the animals was higher in autumn. The surface temperature (ST) of the herd was lower during the spring. It was observed that the hair length (HL) and the hair density (NH) did not vary during the seasons. However, the hair diameter (HD) and the coat thickness (CT) varied, being in the spring, the season in which the animals had the highest HD and autumn, the season in which they had the lowest. The performance was similar throughout the seasons (P > 0.05). The morphological variables of the coat presented 63.8% of original cases grouped, which may characterize the morphological responses of the coat of these animals as an important trait of the adaptive profile of the breed, whereas the opposite occurred for thermoregulatory responses. The variables most used by the herd and that were most important were autumn (CT, NH, HD, HR, RT, and HL), summer (ST and RR), spring (RR, ST, and RT), and winter (RT, HD, HR, and RR). Sheep of the Canaria breed have an adaptive profile that dynamically uses thermoregulatory and morphological responses, molding themselves according to climate changes resulting from seasonal periods on the Island of Tenerife, Spain. The Canaria sheep stood out for the modification of the morphological characteristics of the coat, especially during autumn and spring, and can be considered an excellent genetic resource with excellent adaptive characteristics for arid environments such as those found in the Canary Islands.

Content validation of the decannulation protocol for adult tracheostomized patients. / Validação de conteúdo de protocolo de decanulação de pacientes adultos traqueostomizados.

PURPOSE: Perform content validation of a decannulation protocol for tracheostomized adult patients. METHODS: To validate the content of the protocol developed by speech therapists, the Delphi technique was used. The 11 items of the protocol were judged by experts through rounds via e-mail and were classified as adequate, partially adequate or inadequate, in addition to providing comments and suggestions on each item. 30 speech therapists, 30 respiratory physiotherapists and 30 physicians responsible for the tracheostomy and decannulation procedure were invited. The percentage of agreement adopted was ≥ 80% and the process was interrupted when this percentage was obtained in all items. RESULTS: At the end of the process, 24 professionals participated in the third round, being 46% speech therapists, 29% physiotherapists and 25% physicians. After the experts' suggestions and comments, two items were kept as they were in the initial protocol, seven were reformulated, six were included and two were excluded. The final version of the protocol included: identification, absence of abundant secretions, characteristics of the secretion, effective cough, ability to remove secretions, tolerate the deflated cuff, aptitude in the decannulation process, level of consciousness, change of cannula to a smaller caliber, absence of current/active infection, spontaneous and effective swallowing of saliva, use of a speech valve, aptitude for occlusion of the cannula, assessment of aptitude for decannulation and objective examinations. CONCLUSION: Through the Delphi Technique, the content of the instrument was validated, with substantial changes occurring. The next stage of instrument validation is obtaining evidence of validity in relation to the internal structure.

OBJETIVO: Realizar a validação de conteúdo de um protocolo de decanulação de pacientes adultos traqueostomizados. MÉTODO: Para a validação de conteúdo do protocolo elaborado por fonoaudiólogas foi utilizada a técnica Delphi. Os 11 itens do protocolo foram julgados por peritos, por meio de rodadas via e-mail e foram classificados como adequados, parcialmente adequados ou inadequados, além de fornecerem comentários e sugestões sobre cada item. Foram convidados 30 fonoaudiólogos, 30 fisioterapeutas respiratórios e 30 médicos responsáveis pelo procedimento de traqueostomia e decanulação. O percentual de concordância adotado foi ≥ 80% e o processo foi interrompido quando obtido esse percentual em todos os itens. RESULTADOS: Ao final do processo, 24 profissionais participaram da terceira rodada, sendo 46% fonoaudiólogos, 29% fisioterapeutas e 25% médicos. Após as sugestões e comentários dos peritos, dois itens foram mantidos como estavam no protocolo inicial, sete foram reformulados, seis incluídos e dois excluídos. A versão final do protocolo incluiu: identificação, ausência de secreções abundantes, características da secreção, tosse eficaz, capacidade para remover secreções, tolera o balonete desinsuflado, aptidão no processo de decanulação, nível de consciência, troca de cânula para menor calibre, ausência de infecção vigente/ ativa, deglutição espontânea e eficaz de saliva, uso de válvula de fala, aptidão à oclusão da cânula, avaliação da aptidão para decanulação e exames objetivos. CONCLUSÃO: Por meio da Técnica Delphi houve a validação do conteúdo do instrumento, ocorrendo mudanças substanciais. A próxima etapa de validação do instrumento é a obtenção de evidências de validade em relação a estrutura interna.

Use of thermography and physiological rate to assess heat tolerance in cattle breeds.

Thermography has grown in use in recent years. It is a valuable tool for measuring animal heat tolerance under heat stress conditions since it is a non-invasive, safe and practical methodology. Physiological variables such as respiration rate and eye temperature, and environmental variables such as air temperature and wet bulb temperature were analysed in animals from nine cattle breeds (Angus, Braford, Brangus, Canchim, Charolais, Hereford, Nelore, Simmental and Santa Gertrudis) and one bubaline (Mediterranean) at Rio Grande do Sul, Brazil. Positive correlations were observed between air temperature and respiration rate and eye temperature. Furthermore, the breed strongly influenced the eye temperature and respiration rate of the animals. Eye temperature showed strong correlation with air temperature and wet bulb temperature. Simmental and Nelore animals presented higher eye temperature values. Simmental presented alteration in respiratory rate before the other breeds and Nelore was the last breed to present this alteration. The inflection points in the broken line analysis indicated the environmental temperature limits at which breeds begin to change their respiration to compensate for environmental variation. The use of thermography has proven to be a technique with possible application to evaluate the temperature of animals. Logistic regression analysis allows us to observe how each breed behaves with the temperature change. Using respiration rates and eye temperatures it was possible to identify physiological limits for comfort in different breeds of bovine. In the future it would be interesting to conduct additional studies using other physiological variables and also other indices of climatic conditions.

Performing moderate to severe activity is safe and tolerable for healthy youth while wearing a cloth facemask.

OBJECTIVE: To investigate if a cloth facemask could affect physiological and perceptual responses to exercise at distinct exercise intensities in healthy young individuals. METHODS: Nine participants (sex, female/male: 6/3; age: 13±1 years; VO2peak: 44.5±5.5 mL/kg/min) underwent a progressive square-wave test at four intensities: (1) 80% of ventilatory anaerobic threshold (VAT), (2) VAT, and (3) 40% between VAT and [Formula: see text] wearing a triple-layered cloth facemask or not. Participants then completed a final stage to exhaustion at a running speed equivalent to the maximum achieved during the cardio-respiratory exercise test (Peak). Physiological, metabolic, and perceptual measures were measured. RESULTS: Mask did not affect spirometry (forced vital capacity, peak expiratory flow, forced expiratory volume; all p≥0.27), respiratory (inspiratory capacity, end-expiratory volume [EELV] to functional vital capacity ratio, EELV, respiratory frequency [Rf], tidal volume [VT], Rf/VT, end-tidal carbo dioxide pressure, ventilatory equivalent to carbon dioxide ratio; all p≥0.196), hemodynamic (heart rate, systolic and diastolic blood pressure; all p>0.41), ratings of perceived exertion (p = 0.04) or metabolic measures (lactate; p = 0.78) at rest or at any exercise intensity. CONCLUSIONS: This study shows that performing moderate to severe activity is safe and tolerable for healthy youth while wearing a cloth facemask. TRIAL REGISTRATION: ClinicalTrials.gov: NCT04887714.

Parental Ability to Assess Pediatric Vital Signs.

OBJECTIVE: To evaluate parents' ability to accurately assess their child's heart and respiratory rates (RRs) in the context of potential utility for telehealth visits. STUDY DESIGN: In this controlled study of 203 child-parent pairs, parents measured their child's heart rate (HR) using 4 methods: palpation, auscultation, and 2 photoplethysmographic smartphone applications. Parents measured RR by inspecting the child and tapping the smartphone application. The gold standards were electrocardiogram for the HR and the child's breaths measured by a health care professional for 60 seconds for the RR. We plotted the measurements using a Bland-Altman plot with 95% limits of agreement. RESULTS: Parents underestimated HR by palpation with a calculated bias of -18 beats per minute (bpm) (SD, 19), with limits of agreement ranging from -56 to 19 bpm. Parents overestimated and underestimated HR by auscultation with limits of agreement ranging from -53 to 46 bpm. Smartphone applications did not improve the accuracy of measurements. The accuracy of parental RR measurements was low. For young children, bias was -0.8 breaths per minute (brpm) (SD, 9.8) with limits of agreement from -20 to 19 brpm, and for older children, bias was 0.9 brpm (SD 7.4) with limits of agreement from 6 to 15 brpm. The sensitivity of parental subjective opinion to recognize accelerated RR was 37% (95% CI, 25%-51%). CONCLUSION: Parents were not able to assess their child's RR or HR accurately. Digital remote assessment of children should not rely on parental measurements of vital signs.

Lung Injury Is Induced by Abrupt Increase in Respiratory Rate but Prevented by Recruitment Maneuver in Mild Acute Respiratory Distress Syndrome in Rats.

BACKGROUND: Gradually changing respiratory rate (RR) during time to reduce ventilation-induced lung injury has not been investigated. The authors hypothesized that gradual, compared with abrupt, increments in RR would mitigate ventilation-induced lung injury and that recruitment maneuver before abruptly increasing RR may prevent injurious biologic impact. METHODS: Twenty-four hours after intratracheal administration of Escherichia coli lipopolysaccharide, 49 male Wistar rats were anesthetized and mechanically ventilated (tidal volume, 6 ml/kg; positive end-expiratory pressure, 3 cm H2O) with RR increase patterns as follows (n = 7 per group): (1) control 1, RR = 70 breaths/min for 2 h; (2) and (3) abrupt increases of RR for 1 and 2 h, respectively, both for 2 h; (4) shorter RR adaptation, gradually increasing RR (from 70 to 130 breaths/min during 30 min); (5) longer RR adaptation, more gradual increase in RR (from 70 to 130 breaths/min during 60 min), both for 2 h; (6) control 2, abrupt increase of RR maintained for 1 h; and (7) control 3, recruitment maneuver (continuous positive airway pressure, 30 cm H2O for 30 s) followed by control-2 protocol. RESULTS: At the end of 1 h of mechanical ventilation, cumulative diffuse alveolar damage scores were lower in shorter (11.0 [8.0 to 12.0]) and longer (13.0 [11.0 to 14.0]) RR adaptation groups than in animals with abrupt increase of RR for 1 h (25.0 [22.0 to 26.0], P = 0.035 and P = 0.048, respectively) and 2 h (35.0 [32.0 to 39.0], P = 0.003 and P = 0.040, respectively); mechanical power and lung heterogeneity were lower, and alveolar integrity was higher, in the longer RR adaptation group compared with abruptly adjusted groups; markers of lung inflammation (interleukin-6), epithelial (club cell secretory protein [CC-16]) and endothelial cell damage (vascular cell adhesion molecule 1 [VCAM-1]) were higher in both abrupt groups, but not in either RR adaptation group, compared with controls. Recruitment maneuver prevented the increase in VCAM-1 and CC-16 gene expressions in the abruptly increased RR groups. CONCLUSIONS: In mild experimental acute respiratory distress syndrome in rats, gradually increasing RR, compared with abruptly doing so, can mitigate the development of ventilation-induced lung injury. In addition, recruitment maneuver prevented the injurious biologic impact of abrupt increases in RR.