Total joint arthroplasty (TJA) surgeries are common elective surgeries that result in more than 1.3 million hospital stays in the United States annually [1], and surgical volume is expected to continue to grow through 2040 [2]. In the years since TJA surgeries transitioned away from being inpatient-only procedures, the hospital length of stay for TJA has progressively declined, and the prevalence of outpatient procedures has expanded [3]. In conjunction, clinical readiness for TJA has evolved to include optimizing preoperative education, implementing multimodal anesthesia and pain management, and initiating early lower extremity strengthening and walking rehabilitation [4-7]. However, an underappreciated aspect of TJA readiness and recovery is the potential impact of surgery on respiratory muscle capacity.

The primary inspiratory muscle, the diaphragm, undergoes acute remodeling in response to changes in activity (reviewed by Fogarty et al [8]). Hospital clinical practices such as mechanical ventilation, sedation, and anesthesia significantly decrease diaphragm recruitment, which can degrade ventilation and important related behaviors such as coughing [9]. Importantly, even short periods of mechanical ventilation typical of TJA surgeries contribute to impaired inspiratory force generation [10]. Lung volumes fall after TJA surgery and remain depressed 24 hours later [11]. The extent of the decline is most closely associated with older age [12], and acutely decreased lung function subsequently increases the risk for pulmonary complications [13].

Although postoperative pulmonary complications (PPCs) are relatively uncommon after TJA [14], they prolong the hospital stay, increase costs, and increase the mortality risk [14]. Older adults and those with preexisting lung disease and medical comorbidities may be more susceptible to respiratory weakness, poor cough function, and impaired oxygenation, which can interfere with postoperative rehabilitation and extend the projected length of stay [15,16]. In addition to patients with multiple preexisting health issues, people from racial and ethnic minority groups or those with low socioeconomic status also experience higher risks for acute complications after TJA [17-19]. Therapies designed to limit postoperative respiratory decline have the potential to address unmet needs and improve TJA outcomes for these underserved individuals.

Controlled studies in other surgical populations reveal significant clinical benefits of preoperative inspiratory strength training (IST) compared to usual surgical care. IST for 2-4 weeks before surgery significantly strengthens the respiratory muscles [20-24], mitigates surgical declines in lung function, and lowers the incidence of PPCs [22-26]. Additionally, strength gains associated with preoperative IST are associated with shorter lengths of stay [22,23], which may potentially reduce costs [23]. Although preoperative IST for cardiothoracic surgery is not in itself novel, its impacts on orthopedic surgeries are scarcely studied. We postulate that preoperative IST may be a powerful tool to preserve respiratory strength and cough force in people undergoing TJA. Aim 1 of this study is to investigate the effect of daily IST (dIST), delivered at high intensity preoperatively, on increasing respiratory strength and lung function before TJA.

Although preventative care and educational approaches are 2 recommended strategies to improve health [27], people from underserved communities may lack access to the resources necessary to attend appointments or struggle to complete unsupervised training. Lack of transportation, social support, and health literacy can impede regular adherence to a preoperative exercise plan [28]. As single intense inspiratory loading bouts transiently increase inspiratory pressure generation [29] and enhance central excitability [30], we postulate that they have the potential to counter the downregulation of respiratory neural drive during brief periods of mechanical ventilation. Thus, aim 2 of this study will evaluate whether short-term potentiation of inspiratory drive from a single acute IST (aIST) session immediately prior to surgery can attenuate postoperative declines in inspiratory pressure generation. As high-intensity IST programs that increase maximal inspiratory pressure (MIP) can enhance diaphragm fatigue resistance and reduce exercise-induced dyspnea [31,32], aim 3 of this study will evaluate whether either IST approach can improve functional mobility and dyspnea during the 24-hour postoperative rehabilitation session.

The study was funded in September 2023. IRB approval was obtained in December 2023, and procedures were approved by the safety officer that month. The first randomized participant was enrolled in March 2024. As of May 2026, 31 participants have been enrolled. Data analysis and publication of the primary study results are expected in 2027.

Despite strong evidence demonstrating the benefits of IST on respiratory strength, mobility, and PPCs after major cardiothoracic surgeries [21-24], little is known about its potential to offset surgical declines and accelerate recovery following TJA. This study focuses on TJA because of its high volume and expedited discharge pathway, with hospital lengths of stay averaging <1.5 days for total knee and hip surgeries [39] and anticipated to further decrease in the future [3]. Despite efforts to maximize efficiency of these surgical interventions, certain people with preexisting lung disease, multiple comorbidities, and frailty will require preemptive monitoring due to increased risk for complications. Preoperative IST is an inexpensive, nonpharmacological intervention with the potential to enhance preoperative readiness. As we cannot precisely control the exact timing and number of preoperative dIST sessions, the statistical analysis will explore the volume of dIST as a potential covariate of the primary study end points.

The inclusion of a single, intensive IST session in preoperative holding is a novel aspect of this study. Intense respiratory loading exercises induce temporary increases in respiratory neural drive that could potentially counter the reported decreases in diaphragm contractile function during controlled mechanical ventilation [29,30]. Although single exercise bouts are not expected to achieve lasting gains in function, even a temporary countermeasure may be advantageous for higher-risk surgical candidates who lack the ability to complete weeks of preparatory exercise, whether due to a lack of transportation to attend appointments, challenges with health literacy, or the need for an unplanned or emergent surgery.

The primary outcome of this trial is MIP, a clinical estimate of strength. However, additional secondary measures were included to investigate the effects of the interventions on early postoperative activity-based measures such as coughing force, walking distance, and functional mobility, along with patient-reported dyspnea. Postoperative walking and functional mobility are important functional limitations following TJA that influence the timing of disposition and postacute rehabilitation needs [40]. Although the projected effect size of preoperative IST appears robust for impairment-level outcomes, this study will also provide early indication of its ability to carry over to functional activities and participation-level recovery. As preoperative 6MWD can predict functional ambulation after total joint surgeries [41], the statistical plan will explore preoperative walking distance as a covariate.

As a first preliminary study in TJA, some aspects of the study design remain limited. The sample size was projected from published work in cardiac surgery to detect changes in MIP between dIST and no preoperative exercise. Although we anticipate gaining valuable feasibility information regarding completion of aIST in the acute preoperative setting, we may lack the power to comprehensively distinguish which preoperative training approach (dIST or a single aIST session) can more effectively retain postoperative MIP and functional mobility. Postoperative walking and functional mobility at 24 hours can be influenced by a multitude of factors beyond respiratory strength and may include variations in pain management and pain perception, the ability to participate in same-day therapy, and lack of sleep, nutrition, or hydration. Blinded evaluators will plan for premedication with nursing before the planned 24-hour PT session and ensure that the timing does not interfere with meals. Participants randomized to SOC did not receive a respiratory trainer or training diary or undergo weekly check-ins, and the absence of a sham or attentional control group could inadvertently introduce expectation bias. Even in higher-risk patients, there may be few PPCs in the 30-day period following TJA. However, monitoring complications will enable us to further explore the prevalence of postoperative pulmonary issues in this cohort. Surgeons and study evaluators will be blinded to group assignment, but patients and other study staff will, by necessity, know the allocation.

Research dissemination will be directed toward health care specialties involved in acute TJA management. Study results will be communicated through presentations at scientific conferences and will be published in peer-reviewed journals directed toward readers in orthopedic surgery, rehabilitation, and anesthesiology.

To conclude, this investigator-initiated, randomized, single-blind trial is designed to evaluate the effects of preoperative IST on measures of respiratory strength and function, walking and mobility, and postoperative recovery from lower extremity TJA. Completion of the study will help illuminate whether dIST can improve MIP and cough efficacy preoperatively, whether daily or single-session inspiratory strengthening can attenuate postoperative declines in respiratory strength and pulmonary function, and whether group differences in postoperative inspiratory strength promote earlier recovery of functional mobility.