Body Mass Index (BMI) Cutoffs and Racial, Ethnic, Sex, or Age Disparities in Patients Treated With Total Ankle Arthroplasty.

Background: The rising prevalence of obesity among American adults has disproportionately affected Black adults and women. Furthermore, body mass index (BMI) has historically been used as a relative contraindication to many total joint arthroplasty (TJA) procedures, including total ankle arthroplasty. The purpose of this study was to investigate potential disparities in patient eligibility for total ankle arthroplasty based on race, ethnicity, sex, and age by applying commonly used BMI cutoffs to the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database. Methods: Patients in the ACS-NSQIP database who underwent TAA from 2011 to 2020 were retrospectively reviewed in a cross-sectional analysis. BMI cutoffs of <50, <45, <40, and <35 were then applied. The eligibility rate for TAA was examined for each BMI cutoff, and findings were stratified by race, ethnicity, sex, and age. Independent t tests, chi-squared tests, and Fisher exact tests were performed to compare differences at an α = 0.05. Results: A total of 1215 of 1865 TAA patients (65.1%) were included after applying the exclusion criteria. Black patients had disproportionately lower rates of eligibility at the most stringent BMI cutoff of <35 (P = .004). Hispanic patients had generally lower rates of eligibility across all BMI cutoffs. In contrast, Asian American and Pacific Islander patients had higher rates of eligibility at the BMI cutoffs of <35 (P = .033) and <40 (P = .039), and White non-Hispanic patients had higher rates of eligibility across all BMI cutoffs. Females had lower eligibility rates across all BMI cutoffs. Ineligible patients were also younger compared to eligible patients across all BMI cutoffs. Conclusion: Stringent BMI cutoffs may disproportionately disqualify Black, female, and younger patients from receiving total ankle arthroplasty. Level of Evidence: Level III, retrospective cross-sectional study.

Association of First Metatarsal Phalangeal Joint Fusion for Hallux Rigidus With Patient-Reported Pain and Mental Health Outcomes in Patients Taking Psychotropic Medications.

Background: Limited literature examines the relationship between surgical outcomes in chronic foot and ankle conditions and concurrent psychiatric care. The present study aimed to investigate patient-reported and surgical outcomes of patients treated for a psychiatric disorder undergoing first metatarsophalangeal (MTP) fusion for hallux rigidus. We hypothesized that patients on psychotropic medications would have greater subjective pain preoperatively and less improvement in physical and mental functionality postoperatively when compared with nonmedicated patients. Methods: A single-center, retrospective review of prospectively collected data was conducted on 92 patients undergoing first MTP fusion with a preoperative diagnosis of hallux rigidus from 2015 to 2019. At their preoperative, 6-month postoperative, and 1-year postoperative visits, patients were administered visual analog pain scale (VAS) and 36-Item Short Form Health Survey (SF-36) functionality surveys. Patients were subsequently identified by chronic use of psychotropic medication preoperatively and grouped for analysis (MED, n = 42; NO MED, n = 50). Results: Postoperative mean VAS pain scores were lower for all studied patients at 6 months (VAS = 1.6 ± 2.3) and 1 year postoperatively (VAS = 1.1± 1.8) relative to the preoperative visit (VAS = 4.7 ± 2.8) (P ≤ .0001 and P ≤ .0001, respectively). No differences in mean VAS pain scores nor SF-36 physical component summary scores were detected at preoperative, 6-month, or 1-year visits between NO MED and MED groups. Mean SF-36 mental component summary scores for those in the MED group were lower at preoperative (NO MED = 83.8, MED = 71.8, P = .006) and 6-month postoperative (NO MED = 86.1, MED = 72.7, P = .037) visits than those in the NO MED group, a trend not observed at the 1-year postoperative mark (NO MED = 84.1, MED = 76.8, P = .228). There were no observed differences in operative time (P = .219), tourniquet time (P = .359), nor time to full weightbearing (P = .512) between MED and NO MED groups. Additionally, no differences in postoperative complication rates were observed between groups. Conclusion: In patients treated with psychotropically active medications with hallux rigidus, MTP Fusion appears to be a reasonable treatment choice with similar outcomes for patients requiring psychotropically active medications to the outcomes of those patients not requiring psychotropically active medications. Level of Evidence: Level III, retrospective comparative study.

Non-emergent Conditions of the Ankle, Hindfoot, and Midfoot in Elderly Patients Are as Mobility Limiting as Congestive Heart Failure.

BACKGROUND: Mobility limitations are well linked to increased morbidity and mortality. Older patients with chronic pathologies of the foot and ankle can suffer from significant mobility limitations; however, the magnitude of limitation experienced by this cohort is not well characterized. Conversely, the effects of congestive heart failure (CHF) on patient mobility are routinely assessed via the New York Heart Association (NYHA) classification. New York Heart Association classification is determined by a patient's physical activity limitation and is strongly correlated to functional status. We hypothesized that non-emergent conditions of the foot and ankle would be as mobility limiting as CHF. METHODS: Life-Space Mobility Assessments (LSAs) were prospectively collected from orthopaedic patients at their preoperative visits and from CHF patients at a cardiology clinic. Patients over the age of 50 years were included in this study. Congestive heart failure patients NYHA class II or greater were included. The non-emergent foot and ankle cohort included Achilles tendonitis, ankle joint cartilage defects, ankle arthritis, subtalar arthritis, and midfoot arthritis. Patient demographics and LSA scores were analyzed using Mann-Whitney U and chi-squared tests. RESULTS: A total of 96 elderly, non-emergent foot and ankle operative patients and 45 CHF patients met inclusion criteria. All medical comorbidities, except smoking status, were significantly more prevalent in the CHF cohort. No statistical difference was observed between CHF and preoperative foot and ankle LSA scores (56.1 vs 62.4, P = .320). Life-Space Mobility Assessment scores in the foot and ankle cohort were significantly improved relative to CHF patients, at 6-month and 1-year postoperative visits (P = .028, P < .0001, respectively). CONCLUSION: Non-emergent ankle, hindfoot, and midfoot pathology is associated with similar mobility limitation to that of NYHA class II and III CHF. Older patients undergoing elective foot and ankle procedures exceeded the mobility of CHF patients at 6 months post-operation, and the mobility gains persisted at 1-year post-operation. LEVELS OF EVIDENCE: Level II: Prospective cohort study.

Effect of Obesity on Patient-Perceived Outcomes After First Metatarsophalangeal Joint Arthrodesis.

BACKGROUND: While first metatarsophalangeal joint (MTPJ) arthrodesis is a common and effective procedure, there is a paucity of studies examining obesity's effect on outcomes of 1st MTPJ arthrodesis. This study's purpose was to evaluate patient-reported outcomes following 1st MTPJ arthrodesis in obese versus non-obese patients. METHODS: A retrospective cohort study of 94 patients undergoing first MTPJ fusion over the age of 18 with a diagnosis of hallux valgus or hallux rigidus was performed. Surgical and postoperative outcomes were examined preoperatively and at 6 and 12 months follow-up via Visual Analog Pain scale (VAS), and Short Form 36 (SF-36) surveys, and data were stratified into 2 patient groups: BMI < 30 (n = 62, mean age 63.9 ± 9.1 and ≥ 30 (n = 32, mean age 61.9 ± 8.4). RESULTS: Average overall VAS and SF-36 physical component scores improved significantly at 6 months (P < .001, .006) and 1 year postoperative visits (P < .001, .007) with no differences in survey scores, outcomes, or complications between weight groups. CONCLUSION: Our study showed first MTPJ fusion improves short-term pain and physical quality-of-life in arthritic obese and non-obese patients without differences in nonunion, complications, or patient-reported measures. LEVEL OF EVIDENCE: Level III, Prognostic, Case-Control Study.

Complications of Lesser Toe Surgery: How To Avoid Them before Surgery and How To Assess and Treat Them When They Have Occurred.

Complications following lesser toe surgery are challenging to manage. The keys to treatment of any of these conditions are, first, to try to avoid them through identification of patient- and surgeon-related variables that contribute to their development and, second, following the occurance of a complication, to understand what can and cannot be corrected with surgical and nonsurgical management. This review provides a comprehensive assessment of current literature, demonstrates best practices and approaches to lesser toe complications, and provides an illustration of clinical examples.

Off-label usage of RhBMP-2 in posterior cervical fusion is not associated with early increased complication rate and has similar clinical outcomes.

BACKGROUND CONTEXT: Arthrodesis is important for the success of posterior cervical fusion (PCF), however, there exists limited data regarding the safety and efficacy of bone morphogenic protein (BMP) in PCF. PURPOSE: The primary objective was to evaluate early postoperative complications associated with BMP in PCF and determine whether BMP leads to adverse early clinical outcomes. A secondary objective was to determine the optimal location for BMP sponge placement, within the facet joint (IF) or elsewhere, and the optimal dosage/level. DESIGN: Retrospective, consecutive case-control study. PATIENT SAMPLE: Seven hundred sixty-five patients who underwent PCF OUTCOME MEASURES: Patient-reported outcomes (PROs), complications, arthrodesis, optimum dose/level of BMP METHODS: Surgical data, including preoperative diagnosis, levels fused, type of bone graft, BMP dose (when used), and fusion technique were recorded. Complications were assessed by reviewing the medical record encompassing the first 6-weeks postoperative. These included medical, neurological, and wound-related complications and reoperation. Neurological complications were defined as any new weakness, radicular pain, or numbness. PROs were collected, including SF36, VAS, EQ-5D, and NDI scores. To determine the optimal dosage and location for BMP placement, a sub-analysis was performed. RESULTS: There were no significant differences between the BMP and no BMP group with regards to wound complications, neurological complications, or reoperation. There were no differences in PROs between BMP and no BMP. Placement of BMP for IF and at a dose of 0.87 mg/level minimized wound-related complications. The BMP group had a higher fusion rate compared to the no BMP group (96% vs. 91%, p=.02) when assessed 1 year post-operatively. CONCLUSION: BMP was not associated with a higher rate of early complications after PCF when the dose was minimized. Complications thought to be associated with BMP, such as compressive seroma, radiculitis, and wound-related complications were not seen at a higher rate. PROs at early follow-up were similar. Placement of BMP for IF and at lower doses than previously reported may minimize complications.

Nedocromil sodium and diphenhydramine HCl ameliorate exercise-induced arterial hypoxemia in highly trained athletes.

INTRODUCTION: Exercise-induced arterial hypoxemia (EIAH) has been observed in highly trained endurance athletes during near maximal exercise, which may be influenced by a histamine-mediated inflammatory response at the pulmonary capillary-alveolar membrane. In order to test this hypothesis, we examined whether the mast cell stabilizer nedocromil sodium (NS) and H1 -receptor antagonist diphenhydramine HCL (DH) would ameliorate EIAH and mitigate the drop in arterial oxyhemoglobin saturation (Sa O2 ) during intensive exercise. METHODS: Seven highly trained male cross country runners (age, 21 ± 2 years; V̇O2max , 74.7 ± 3.5 ml·kg-1 ·min-1 ) participated in the study. All subjects completed a maximal exercise treadmill test to exhaustion, followed by three 5-min constant-load exercise bouts at 70%, 80%, and 90% V̇O2max . Prior to testing, subjects received either placebo (PL), NS, or DH. RESULTS: Compared to PL, there was a significant treatment effect on Sa O2 (p < 0.001) for both NS and DH during both constant-load exercise and at V̇O2max . Post hoc tests revealed Sa O2  values, compared to PL, were significantly higher at V̇O2max and during DH trials and higher with NS at constant-load intensities except at 70% (p = 0.13). CONCLUSION: The findings provide further evidence that histamine contributes directly or indirectly to the development of EIAH during intense exercise in highly trained athletes.

Telehealth Can Be Implemented Across a Musculoskeletal Service Line Without Compromising Patient Satisfaction.

Background: The COVID-19 pandemic has led to changes to in-office orthopedic care, with a rapid shift to telemedicine. Institutions' lack of established infrastructure for these types of visits has posed challenges requiring attention to confidentiality, safety, and patient satisfaction. Purpose: The aim of this study was to analyze the feasibility of telemedicine in orthopedics during the pandemic and its effect on efficiency and patient satisfaction. Methods: Patients seen by the Emory University Department of Orthopaedics Sports Medicine and Upper Extremity Divisions via telemedicine from March 23 to April 24, 2020, were contacted by telephone. Each patient was asked to respond to questions on satisfaction, ease of use, and potential future use; satisfaction with telemedicine and previous clinical visits were measured using a modified 5-point Likert scale. Results: Of the 762 patients seen, 346 (45.4%) completed the telemedicine questionnaire. Satisfaction varied by visit type, with average scores of 4.88/5 for in-office clinic visits versus 4.61/5 for telemedicine visits. There was no significant difference among age groups for satisfaction ratings. Patients 65 years old or older reported significantly longer visit times and decreased ease of use with the telemedicine platform. Conclusion: Telemedicine in a large orthopedics department was successfully implemented without compromising patient satisfaction. The use of telemedicine allows many patients to be seen quickly and efficiently without diminishing their musculoskeletal clinical experience.

Feasibility of Rapid Development and Deployment of a Telemedicine Program in a Foot and Ankle Orthopedic Practice.

BACKGROUND: A lack of access to care is predictably associated with negative outcomes in foot and ankle surgery. Despite recent advances in telecommunication technologies, the field of orthopedics has been slow to adopt these resources in offsetting barriers to care. The COVID-19 pandemic has forced departments to change their clinical approach, lending unprecedented opportunity to better understand how telehealth may bridge this care gap in foot and ankle practices. The purpose of this study was to assess patient-reported outcomes of telemedicine encounters, including comfort and patient satisfaction. Our hypothesis was that patients would be significantly less satisfied with telemedicine when compared with in-office appointments for all nonemergency visit types. METHODS: Telemedicine satisfaction was assessed via phone survey with a modified 1 to 5 Likert scale. Patients who had completed a telemedicine visit between April 13, 2020, and June 19, 2020, were eligible to participate. Patient demographics were recorded, and data were analyzed using paired and independent t tests for parametric continuous data and Fisher's exact and chi-square tests for noncontinuous data. A total of 216 patients completed the telemedicine questionnaire. RESULTS: The overall mean satisfaction for telemedicine visits (4.7) was significantly lower than that for in-office visits (4.9) (P < .001). However, the majority (90.3%) of patients reported they would use telemedicine again in the future. When compared, patients seeking fracture care had significantly higher telemedicine satisfaction (4.9, n = 38) than those receiving nonfracture care (4.6, n = 178) (P = .001), and those greater than 50 miles from the clinic had higher satisfaction (5.0, n = 14) than patients living within 50 miles of the clinic (4.7, n = 202) (P < .001). CONCLUSION: Patients were more satisfied with their in-office clinic visit than telemedicine, although the vast majority of patients endorsed a willingness to utilize telemedicine in the future. Patients with trauma and greater barriers to foot and ankle care were more satisfied with their telemedicine visits. LEVEL OF EVIDENCE: Level III, retrospective cohort study.

Effect of Age on Complication Rates and Outcomes Following First Metatarsophalangeal Arthrodesis for Hallux Rigidus.

BACKGROUND: Hallux rigidus is one of the most common toe pathologies in patients greater than 50 years old. Although metatarsophalangeal (MTP) arthrodesis is used to improve pain and function, older patients are often considered to be higher-risk operative candidates. There are minimal data on outcomes of MTP fusion and no studies comparing outcomes between geriatric and younger patients. METHODS: This is a single-center, prospective study of all patients who underwent MTP fusion between August 1, 2015, and July 1, 2018. Patient-reported outcomes were assessed using the Short Form Health Survey (SF-36), Life-Space Assessment survey (LSA), and visual analog scale (VAS) for pain administered preoperatively as well as 6 months and 1 year postoperatively. Baseline characteristics and operative outcomes were collected from the electronic medical record. Clinical and patient-reported outcomes were compared between patients <65 years old and ≥65 years old. Of 143 included patients, 79 were in the younger group (mean of 56.5 years) and 64 were in the older group (mean of 72.0 years). RESULTS: Compared with the younger group, the older group was more predominantly female (95.3% older group, 77.2% younger group, P = .002). More patients in the older group had hypertension (73.4% older group, 50.6% younger group, P = .005) and coronary artery disease (9.4% older group, 0.0% younger group, P = .005). Both age groups had similar rates of postoperative wound complications requiring operative irrigation and debridement, deep vein thrombosis, deformity recurrence, and revision surgery. No differences were detected in SF-36, LSA, and VAS surveys administered at baseline, 6 months postoperation, or 1 year postoperation between younger and older patients. CONCLUSION: Despite more comorbidities, older patients had similar rates of postoperative complications and reported similar outcomes for pain, function, and mobility following MTP fusion. These findings support increased implementation of MTP fusion surgery for older patients with hallux rigidus. LEVEL OF EVIDENCE: Level II, prospective cohort.

Evidence-Based Hospital Procedural Volumes as Predictors of Outcomes After Revision Hip Arthroplasty.

BACKGROUND: The aim of this study is to define the evidence-based institutional volume-outcome relationship in revision hip arthroplasty. We hypothesized that high-volume centers would be associated with superior outcomes, and that stratum-specific likelihood ratio (SSLR) analysis would delineate concrete volume thresholds for optimizing outcomes. METHODS: The Nationwide Readmission Database was queried from 2011 to 2016 for patients undergoing revision hip arthroplasty. SSLR analysis was used to determine hospital volume cutoffs specific for outcomes of interest. Volume categories were confirmed with multivariate regression. RESULTS: SSLR analysis produced distinct hospital volume cutoffs for all outcomes. Each subsequent volume threshold diminished patients' risk for adverse outcomes. Tertiles were identified for 90-day infection (≤6, 7-51, ≥52 cases per year). Quartiles were found for 90-day readmission (≤5, 6-15, 16-79, ≥80), 90-day prosthesis-related complication (≤5, 6-16, 17-65, ≥66), 90-day dislocation (≤5, 6-19, 20-79, ≥80), and non-home discharge (≤5, 6-15, 16-40, and ≥41). Quintiles were generated for extended length of stay >2 days (≤2, 3-10, 11-20, 21-30, ≥31). Heptiles were produced for medical complications within 90 days (≤2, 3-8, 9-16, 17-51, 52-89, ≥90). CONCLUSION: This is the first known study to define evidence-based thresholds for the impact of hospital volume on revision joint arthroplasty. This supports the notion that institutional volume functions as a surrogate for protocolized interdisciplinary coordination of care and surgical experience, and that high-volume centers offer enhanced outcomes for complex cases. Additional studies should investigate the potential role for incentivization of such institutions, as they offer optimal outcomes for revision hip arthroplasty.

Mobility Limitation After Surgery for Degenerative Pathology of the Ankle, Hindfoot, and Midfoot vs Total Hip Arthroplasty.

BACKGROUND: Surgery for degenerative foot and ankle conditions often results in a lengthy recovery. Current outcome measures do not accurately assess postoperative mobility, especially in older patients. The Life-Space Assessment (LSA), a questionnaire quantifying patients' mobility after a medical event, was used in this study to assess perioperative mobility in total hip arthroplasty (THA) and foot and ankle surgery patients. We hypothesized that patients undergoing elective foot and ankle surgery would have greater postoperative mobility limitation than THA patients. METHODS: Preoperative, 3-month, and 6-month postoperative LSA data were collected from THA and foot and ankle cohorts. Twelve-month postoperative data were obtained for the foot and ankle group as well. Patient demographics were recorded, and data were analyzed using a Mann-Whitney U test. RESULTS: Twenty-eight degenerative foot and ankle operative patients and 38 THA patients met inclusion criteria. Only patients aged ≥60 years were included in this study. The mean preoperative LSA score was lower in the foot and ankle group (68.8) compared with THA (74.0), although the difference was not statistically significant (P = .602). THA patients showed a significant increase in LSA score from preoperative (74) to 6 months postoperation (95.9) (P = .003); however, foot and ankle patients showed no significant difference between preoperative (68.8) and 6-month (61.2) scores (P = .468). Twelve months postoperatively, foot and ankle patients showed improvement in LSA score (88.3) compared with preoperation (P = .065). CONCLUSION: Compared with THA, recovery of mobility after foot and ankle surgery was slower. THA patients exhibited improved mobility as early as 3 months after surgery, whereas foot and ankle patients did not show full improvement until 12 months. This work will assist the foot and ankle specialist in educating patients about challenges in mobility during their recovery from surgery. LEVEL OF EVIDENCE: Level II, prospective cohort study.

Outcomes of Operative Management of Insertional Achilles Tendinopathy in the Young vs Elderly.

BACKGROUND: Insertional Achilles tendinopathy (IAT) is a common cause of chronic posterior heel pain. Surgical intervention reproducibly improves patients' pain and functional status. We hypothesized that patients older than 60 years would have similar improvements in pain and function and low rates of complications after surgery for IAT when compared to a younger cohort. METHODS: Retrospective review of adult case series in patients undergoing surgical management of IAT. Patients were stratified into those 60 years and younger and those older than 60 years. Patients with prior or concomitant surgical procedures and revisions were excluded. Visual analog scale (VAS), Short Form-36 Physical Component Summary and Mental Component Summary (SF-36 PCS/MCS) scores, wound infection, and recurrence, defined as a redevelopment of heel pain in the operative extremity within 6 months, were assessed with a minimum follow-up of 12 months. Statistical analysis was performed using linear regression mixed models and χ2 analysis. Thirty-seven patients were enrolled, with 38 operative heels. The younger cohort had an average age of 49.1 (range, 26-60) years. The older group had an average age of 66.8 (range, 61-76) years. RESULTS: VAS and SF-36 PCS scores for the entire cohort significantly improved at 6 and 12 months postoperatively (P < .001). Postoperative SF-36 MCS scores for the cohort significantly improved only at 12 months (P < .001). No significant differences between the young and elderly were seen with regard to improvements in VAS and SF-36 PCS/MCS at 6 or 12 months postoperatively. Multiple linear regression models showed no significant difference between age groups and VAS score, SF-36 PCS/MCS, or change in pain scores after controlling for comorbidities. No significant difference in overall complication rates was seen between the 2 groups (4.9% vs 29.4%, P = .104). There was 1 recurrence of heel pain in the younger group and 4 recurrences of pain in the older group (23.5%) at 6 months, of which 2 resolved at 1 year. There was 1 case of a superficial wound infection requiring antibiotics in the older cohort (5.9%). No patients required surgical revision. CONCLUSION: Surgical management of IAT in an older population produced similar improvements in clinical results when compared to a younger cohort, with no significant increase in postoperative complications. LEVEL OF EVIDENCE: Level III, retrospective comparative series.

Comorbidities Associated With Poor Outcomes Following Operative Hammertoe Correction in a Geriatric Population.

BACKGROUND: Although complications following hammertoe correction surgery are rare, older patients with comorbid conditions are often considered poorer operative candidates compared with younger, healthier patients because of a suspected increased risk of adverse outcomes. The aim of this study was to determine if the presence of multiple comorbidities was associated with increased complications or unsuccessful patient-reported outcomes following operative hammertoe correction in geriatric patients. METHODS: Prospectively collected data was reviewed on 78 patients aged 60 years or older who underwent operative correction of hammertoe deformity. Patient demographics, comorbidities, and postoperative complications were recorded. Patient-reported outcomes were assessed using preoperative and postoperative visual analog scale for pain and Short Form Health Survey Physical and Mental Component Summary with 1 year of follow-up. Patients were divided into 2 groups based on number of comorbidities (0 or 1 vs > 2) and then compared. The average age of patients was 69.4 years and the prevalence of comorbidities in the study population was as follows: 11.5% smokers, 25.6% on blood thinners, 15.4% with rheumatoid arthritis, 7.7% with diabetes mellitus, 2.6% with peripheral arterial disease, 6.4% with chronic obstructive pulmonary disease, 11.5% with coronary artery disease, and 23.1% with osteoporosis. RESULTS: Fifty-three patients (67.9%) had 0 or 1 comorbidity and 25 (32.1%) had 2 or more comorbidities. Compared to the 0 or 1 comorbidity group, the presence of multiple comorbidities was associated with an adjusted odds ratio (OR) for superficial wound infection of 4.18 (P = .045) and deformity recurrence requiring surgery OR of 23.15 (P = .032). Patient-reported outcomes were similar between comorbidity groups. CONCLUSIONS: This study further informs foot and ankle specialists to maintain increased surveillance for postoperative complications and unsuccessful outcomes in patients with multiple comorbidities. Although geriatric patients still report significant improvements in both pain and function, patients with underlying medical conditions should be counseled about their increased risks when pursuing operative hammertoe correction. LEVEL OF EVIDENCE: Level III, retrospective comparative series.

Acute hypercapnia does not alter voluntary drive to the diaphragm in healthy humans.

Although systemic hypercapnia is a common outcome of pulmonary disease, the relationship between hypercapnia and voluntary diaphragmatic activation (VAdi) is unclear. To examine whether hypercapnia independent of ventilatory work contributes to reduced central motor drive to the diaphragm in healthy humans, 14 subjects spontaneously breathed room air (NN) or a hypercapnic gas mixture (HH; 7% CO2 with air) while at rest. Thereafter, subjects volitionally hyperventilated room air (NH) matching the minute ventilation recorded during HH while maintained at eucapnic levels. Twitch interpolation with bilateral magnetic stimulation of phrenic nerves at functional residual capacity was used to assess VAdi during the three trials. Although PETCO2 was elevated during HH compared with NN and NH (52 vs 36 mmHg), VAdi was not altered across the trials (HH = 93.3 ±â€¯7.0%, NN = 94.4 ±â€¯5.0%, NH = 94.9 ±â€¯4.6%, p = 0.48). Our findings indicate that the magnitude of hypercapnia acutely imposed may not be effective in inhibiting voluntary neural drives to the diaphragm in normal resting individuals.