Patterns of B-cell lymphocyte expression changes in pre- and post-malignant prostate tissue are associated with prostate cancer progression

BACKROUND

Inflammation characterized by the presence of T and B cells is often observed in prostate cancer, but it is unclear how T- and B-cell levels change during carcinogenesis and whether such changes influence disease progression.

METHODS

The study used a retrospective sample of 73 prostate cancer cases (45 whites and 28 African Americans) that underwent surgery as their primary treatment and had a benign prostate biopsy at least 1 year before diagnosis. CD3+, CD4+, and CD20+ lymphocytes were quantified by immunohistochemistry in paired pre- and post-diagnostic benign prostate biopsy and tumor surgical specimens, respectively. Clusters of similar trends of expression across two different timepoints and three distinct prostate regions-benign biopsy glands (BBG), tumor-adjacent benign glands (TAG), and malignant tumor glandular (MTG) regions-were identified using Time-series Anytime Density Peaks Clustering (TADPole). A Cox proportional hazards model was used to estimate the hazard ratio (HR) of time to biochemical recurrence associated with region-specific lymphocyte counts and regional trends.

RESULTS

The risk of biochemical recurrence was significantly reduced in men with an elevated CD20+ count in TAG (HR = 0.81, p = 0.01) after adjusting for covariates. Four distinct patterns of expression change across the BBG-TAG-MTG regions were identified for each marker. For CD20+, men with low expression in BBG and higher expression in TAG compared to MTG had an adjusted HR of 3.06 (p = 0.03) compared to the reference group that had nominal differences in CD20+ expression across all three regions. The two CD3+ expression patterns that featured lower CD3+ expression in the BBG compared to the TAG and MTG regions had elevated HRs ranging from 3.03 to 4.82 but did not reach statistical significance.

CONCLUSIONS

Longitudinal and spatial expression patterns of both CD3+ and CD20+ suggest that increased expression in benign glands during prostate carcinogenesis is associated with an aggressive disease course.

Abstract 80: Change in B cell lymphocyte expression from the pre- to post-malignant prostate predicts disease aggressiveness

Background: Inflammatory cells such as tumor infiltrating lymphocytes (comprising T and B cells) are often present in prostate tissue undergoing tumorigenesis but their role in disease progression is unclear. The current study aims to characterize the expression dynamics of CD3, CD4 and CD20 lymphocytes from the pre- to post-malignant prostate environment and the association of these dynamics with aggressive prostate cancer.

Methods: The study sample included 72 prostate cancer cases (44 whites and 28 African American) that underwent surgery as their primary treatment and had a benign prostate biopsy at least one year before diagnosis and were followed for biochemical recurrence (BCR). Counts of CD3-, CD4- and CD20-positive lymphocytes were quantified by immunohistochemistry using an automated multi-image processing procedure in pre-malignant benign biopsy (BB), tumor-adjacent benign (TAB) and malignant tumor glandular (MTG) regions of prostatectomy. A cox proportional hazards model was used to estimate the hazard ratio (HR) of time to BCR associated with inflammatory marker count in different regions of the prostate. Clustering was performed to identify similar trends of expression changes of CD3, CD4 and CD20 between the regions - BB, TAG and MTG using Time-series Anytime Density Peaks Clustering (TADPole).

Results: The risk of BCR was significantly reduced in men who had an elevated CD20 count in the TAG (HR=0.80, p=0.01) after adjusting for race, age at diagnosis, PSA at the time of benign biopsy and the Gleason grade group. CD3 and CD4 counts in the prostate regions did not show any significant association to BCR. TADPole identified four main different patterns of CD20 expression changes across the BB-TAB-MTG regions namely 1) minimal to no change in expression between the regions (n=45 pairs); 2) high expression in BB/no expression in TAG/higher expression in MTG (n=3 pairs); 3) high expression in BB/higher expression in TAG/no expression in MTG (n=8 pairs); 4) no expression in BB/higher expression in TAG compared to MTG (n=16 pairs). In comparison to the reference group (Cluster 1), Cluster 4 was at 3.5 times higher risk of BCR with an adjusted HR of 3.5 (p=0.0184).

Conclusion: Elevated CD20 expression in TAG was associated with less aggressive disease. Furthermore, cases that had CD20 expression highest in their benign prostate adjacent to tumor preceded by absence of CD20 expression in their pre-malignant benign prostate had the most aggressive disease course. Further studies are warranted to understand how CD20 lymphocyte dynamic changes influence prostate tumorigenesis.

Citation Format: Sudha M. Sadasivan, Yalei Chen, Nilesh S. Gupta, Ryan Sanii, Kevin R. Bobbitt, Dhananjay A. Chitale, Sean R. Williamson, Andrew G. Rundle, Deliang Tang, Benjamin A. Rybicki. Change in B cell lymphocyte expression from the pre- to post-malignant prostate predicts disease aggressiveness [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 80.

Treatment of Hallux Rigidus: Comparison of Hemiarthroplasty with Cartiva Implant, Allograft Interpositional Arthroplasty, and Arthrodesis

Category:

Midfoot/Forefoot; Other

Introduction/Purpose:

Hallux Rigidus (HR) can cause pain with motion, enlarged joint, decreased joint space, subchondral sclerosis, osteophyte formation and restricted joint mobility, limiting patient physical activity. A modern technique for the treatment of HR is 1st MTP hemiarthroplasty with the use of a Cartiva synthetic cartilage implant. The Cartiva implant is designed to imitate natural cartilage; this allows patients to maintain motion in the 1st MTP joint. Current scientific literature reporting early outcomes of the procedure is sparse and mixed. This discrepancy and the overall scarcity of data indicates the need for further analysis. The purpose of this study is to compare improvement in VAS with 1st MTP hemiarthroplasty with the Cartiva implant, allograft interposition arthroplasty and fusion in patients who failed conservative management or cheilectomy.

Methods:

This study evaluated subjects who underwent interpositional arthroplasty, arthrodesis, or hemiarthroplasty with the Cartiva implant from January 2008 to April 2020, with a minimum of one year documented follow-up. All subjects were 18 years of age and older, diagnosed Hallux rigidus with pain, had a decrease in 1st MTP motion, and had X-ray findings consistent with decreased joint space. Patient data collected includes age, gender, ethnicity, occupation, height, weight, BMI, diabetes status, rheumatoid arthritis status, smoking, co-morbid conditions, medication, activity of choice, duration of symptoms, and operative data. Pre-operative and post- operative Visual Analog Scale (VAS) pain scores were compared between groups. Pain, function, and alignment between groups were also evaluated, pre-operatively and post- operatively, using the AOFAS Midfoot Scale. Secondary objectives evaluated include surgical complications, surgical revision, and X-rays.

Results:

One hundred patients with 12 months of post-operative follow-up were included in this study: 52 hemiarthroplasty with Cartiva implant patients (Group A), 24 arthrodesis patients (Group B), and 24 interpositional arthroplasty patients (Group C). The mean age of patients was 57.12 years (range 35-95). Average VAS pain scores for Group A was 3.78 (0-9), for Group B was 2.71 (0-10), and Group C was 3.67 (0-8). The average AOFAS score for Group A was 63.36 (30-95), for Group B was 60.98 (32- 83), and Group C was 60.13 (31-83). Pre-operative average VAS pain scores were 4.86 (Group A), 2.32 (Group B), and 5.58 (Group C). Post-operative average VAS pain scores were 2.69 (Group A), 0.91 (Group B), and 1.75 (Group C). Pre-operative average AOFAS scores were 59.52 (Group A), 48 (Group B), and 47.25 (Group C). Post-operative average AOFAS scores were 67.20 (Group A), 73.96 (Group B), and 73 (Group C).

Conclusion:

Preliminary data shows the greatest reduction in VAS pain scores in the interpositional arthroplasty group. The greatest improvement in derived AOFAS score was seen in the arthrodesis and interpositional arthroplasty groups, indicating a better overall combination of post-operative pain, function, and alignment when compared to patients who underwent hemiarthroplasty with Cartiva implant. While this study is not yet complete, it appears that hemiarthroplasty with Cartiva implant may allow patients to maintain motion in the 1st MTP joint, but at the cost of increased post-operative pain.

Evaluation of early oral cavity cancer treatment quality at a single institution

OBJECTIVE

To evaluate the adherence to oral cavity quality guidelines endorsed by the American Head and Neck Society (AHNS) at a large tertiary care hospital.

METHODS

This retrospective study identified patients treated for early-stage oral tongue squamous cell carcinoma at a tertiary care hospital from 1992 to 2013. Patient charts were reviewed for 26 process quality measures and four key indicator process quality measures as endorsed by the AHNS. Patients were then grouped by diagnosis date either before (historical group, 1992-2007) or after (current treatment group, 2008-2013) the published process quality measures from the AHNS. Descriptive statistics were used to evaluate the rates of adherence for each process quality measure within the 2 groups.

RESULTS

Of the 57 patients identified, 29 were female (51%). The mean age was 62.3 years. A majority of the oral cavity cancers were stage I (59.6%), followed by stage II (35.1%) and stage III (5.3%). Compliance with the process quality measures was in the acceptable range in both cohorts. However, several areas demonstrated lower adherence in both cohorts. Statistically significant improvements were noted between the two cohorts, which showed a measurable improvement in adherence to process quality measures in several key areas over time.

CONCLUSION

Using the process quality measures proposed by the AHNS, adherence to the process quality measures for early-stage oral cavity cancer care at a tertiary care center was successfully evaluated. In general, good compliance with the proposed process quality measures was found and several areas for improvement were identified.

LEVEL OF EVIDENCE

2c Laryngoscope, 129:1816-1821, 2019.

Respiratory response to CO2 in the hypocapnic range in awake humans

The response of respiratory motor output to CO2 in the hypocapnic range (< 36 Torr PCO2) in the absence of hypoxemia is not well characterized in awake normal humans. We induced hypocapnia with hyperoxia in 16 normal volunteers by placing them on a volume-cycled ventilator in the assist mode. Subjects were not aware of the purpose of the study. All subjects continued rhythmic breathing despite high tidal volumes and severe hypocapnia (approximately 25 Torr alveolar PCO2). Inspired CO2 fraction was increased in steps, and changes in respiratory motor output were quantitated from changes in airway pressure at constant volume and flow, changes in respiratory rate, and change in rate of decline in airway pressure before triggering (dP/dt). There was a significant increase in respiratory muscle pressure, but not in respiratory rate, from 26 to 36 Torr PCO2. The slope of the response increased gradually from 26 to 41 Torr PCO2. Respiratory rate significantly increased only above 36 Torr. We conclude that the response to PCO2 in the hypocapnic range is basically nonlinear with no clear CO2 threshold and the CO2 responsiveness extends well below eupneic CO2 levels.

An approach to the study of upper airway function in humans

Current methods for testing upper airway (UA) collapsibility in humans tend to produce intervention-related changes in some of the variables that affect UA stability. Therefore, their results may not reflect UA stability under the experimental conditions of interest. In the proposed method, the subject lies in a body enclosure with head and neck out. Pressure is altered in brief (approximately 0.2-s) pulses to avoid behavioral responses. The collapsibility of UA under "static" conditions is tested by delivering identical pressure pulses simultaneously to the airway and body surface inside the shell. Because the pressure applied to the respiratory system is not altered, cessation of flow indicates closure, and the pressure at which this happens is Pclosure. Collapsibility under dynamic conditions is tested by applying brief negative pulses to the shell only, thereby forcing an increase in inspiratory flow. Ten normal awake subjects were tested. None of the subjects developed closure when negative pulses (0 to -16 cmH2O) were applied to both airway and shell during inspiration or expiration with either nose or mouth breathing. There were only small reductions in flow, indicating minor narrowing. By contrast, pressure pulses of similar magnitude applied to the shell alone were associated with closure in 5 of 10 subjects. We conclude that the UA of normal awake humans is fairly stable under the influence of statistically applied pressure but susceptible to collapse under conditions of increased flow. Pclosure determined under static conditions underestimates the vulnerability of the UA to collapse under dynamic conditions.

Role of central respiratory muscle fatigue in endurance exercise in normal subjects

The role of central respiratory muscle fatigue in determining endurance time (ET) of steady-state ergometry, ventilation (VE), and breathing pattern during exhaustive submaximal exercise is not known. Six normal subjects exercised on a cycle ergometer to exhaustion at 72-82% of maximal power output on three occasions. During the second test, inspiratory muscle load was reduced (approximately 50% of baseline load) for all but the last 3 min of exercise. ET was determined, and VE, tidal volume (VT), respiratory rate (f), and sense of breathing effort (Borg scale) were assessed at different points during the assisted exercise and compared with the values obtained at the same time in identical tests without assist, carried out before and after the assisted test (different days). Borg scale rating was less and there was a nonsignificant trend for VT and VE to be higher and for f to be lower when the assist was in place than at the same time during the unassisted runs. In the last 3 min of exercise, when the respiratory load was comparable (assist removed) but ventilatory work history was different, there were no significant differences in sense of respiratory effort, VE, VT, or f between the experimental and control tests, and ET was also similar. We conclude that central respiratory muscle fatigue plays no role in determining ET, sense of respiratory effort, or breathing pattern in normal subjects during exhaustive submaximal exercise.

Steady-state ventilatory responses to expiratory resistive loading in quadriplegics

Patients with quadriplegia have a limited capacity to recruit expiratory muscles and are deprived of respiratory-related feedback from the rib cage and abdominal wall. We wished to evaluate the compensatory strategies available to such patients during expiratory resistive loading (ERL) and to compare their responses with those of normal healthy individuals. In addition, to determine whether the quadriplegic subjects have a blunted sensory appreciation of added ERL, we also compared sensory detection thresholds (delta R50). Steady-state ventilatory responses to ERL (delta R = 12 cm H2O/L/s) were compared in seven quadriplegic patients (level of injury, C6, C7) and six age-matched normal subjects. Highly significant intergroup differences were evident in the extent of prolongation of expiratory time (TE) and total cycle duration (Ttot) during ERL; values of delta TE and delta Ttot in quadriplegics were, on average, 46% of those of normals (p < 0.001). Minute ventilation (VE) was defended to an equal or better extent in quadriplegics. ERL-induced changes in tidal volume, inspiratory duration, mean inspiratory and expiratory flows, and end-expiratory lung volume (EELV) were not significantly different. Average delta R50 in quadriplegics and normals were (mean +/- SD), 1.73 +/- 0.039 cm H2O/L/s and 1.62 +/- 0.4 cm H2O/L/s, respectively (p = ns). Quadriplegics, therefore, despite substantial sensory and motor deficits, defend ventilation and EELV as effectively as normal individuals and show no attenuation in the ability to detect an added expiratory resistance.

Breathing pattern adjustments during the first year following cervical spinal cord injury

The alterations in lung function and breathing pattern were examined in 6 quadriplegics at 3, 6 and greater than 12 months post injury, and were compared to 6 able bodied controls. Subjects were studied in both the seated and supine positions. Functional residual capacity (FRC), forced vital capacity (FVC), inspiratory capacity (IC), and maximum mouth pressure (Pimax) at FRC were measured. Total lung capacity (TLC) and residual volume (RV) were calculated. Resting breathing pattern was assessed for 20 minutes from a spirogram derived from summed rib cage and abdominal strain gauge signals. At 3 months in quadriplegics, TLC was reduced (p less than 0.05), RV increased (p less than 0.01) and FRC was normal in sitting; in supine, only TLC was reduced (p less than 0.05); Pimax was decreased (p less than 0.01) in both positions in quadriplegics at 3 months, but increased over the first year in the seated position (p less than 0.01). There were no alterations in breathing pattern at any time interval in quadriplegics in supine. In contrast, at 3 months post injury in sitting, expiratory time (Te) was shortened (p less than 0.05), tidal volume (Vt) was decreased, and heart rate elevated as compared to controls (p less than 0.05). Inspiratory time (Ti) was not significantly shortened at 3 months in quadriplegics, but a lengthening of Ti occurred between 3 and 6 months (p less than 0.025) resulting in increased Vt, and heart rate decreased to normal. Vt/Ti was reduced, and did not alter with time. The lengthening of Ti/Ttot observed in supine in control subjects (p less than 0.025), was not observed in quadriplegics. Quadriplegics sighed as frequently in supine as did controls at all stages post injury, whereas they decreased sighing frequency in sitting at 3 and 6 months post injury (p less than 0.05). The improvement in resting breathing pattern observed in quadriplegics in sitting with time, may be due to increased accessory muscle function, improved chest wall stability and thoracoabdominal coupling, or a combination of these factors. It is also possible that the alterations in breathing pattern were a response to cardiovascular adjustments occurring in the same time frame. Quadriplegics retain the sigh reflex, but do not take as many big breaths in sitting as they do in supine, probably due to the increased work of breathing in the seated posture.

Mechanism of detection of resistive loads in conscious humans

Conscious humans easily detect loads applied to the respiratory system. Resistive loads as small as 0.5 cmH2O.l-1.s can be detected. Previous work suggested that afferent information from the chest wall served as the primary source of information for load detection, but the evidence for this was not convincing, and we recently reported that the chest wall was a relatively poor detector for applied elastic loads. Using the same setup of a loading device and body cast, we sought resistive load detection thresholds under three conditions: 1) loading of the total respiratory system, 2) loading such that the chest wall was protected from the load but airway and intrathoracic pressures experienced negative pressure in proportion to inspiratory flow, and 3) loading of the chest wall alone with no alteration of airway or intrathoracic pressure. The threshold for detection for the three types of load application in seven normal subjects was 1.17 +/- 0.33, 1.68 +/- 0.45, and 6.3 +/- 1.38 (SE) cmH2O.l-1.s for total respiratory system, chest wall protected, and chest wall alone, respectively. We conclude that the active chest wall is a less potent source of information for detection of applied resistive loads than structures affected by negative airway and intrathoracic pressure, a finding similar to that previously reported for elastic load detection.

Role of the chest wall in detection of added elastic loads

Changes in respiratory mechanical loads are readily detected by humans. Although it is widely believed that respiratory muscle afferents serve as the primary source of information for load detection, there is, in fact, no convincing evidence to support this belief. We developed a shell that encloses the body, excluding the head and neck. A special loading apparatus altered pressure in proportion to respired volume (elastic load) in one of three ways: 1) at the mouth only (T), producing a conventional load in which respiratory muscles are loaded and airway and intrathoracic pressures are made negative in proportion to volume, 2) both at the mouth and in the shell (AW), where the same pattern of airway and intrathoracic pressure occurs but the muscles are not loaded because Prs (i.e., mouth pressure minus pressure in the shell is unchanged, and 3) positive pressure in proportion to volume at the shell only, loading the chest wall but causing no change in airway or thoracic pressures (CW). The threshold for detection (delta E50) with the three types of application was determined in seven normal subjects: 2.16 +/- 0.22, 2.65 +/- 0.54, and 6.21 +/- 0.85 (SE) cmH2O/l for T, AW, and CW, respectively. Therefore the active chest wall, including muscles, is a much less potent source of information than structures affected by the negative airway and intrathoracic pressure. The latter account for the very low threshold for load detection.

Effect of phase shifts in pressure-flow relationship on response to inspiratory resistance

Inspiratory prolongation is an integral component of the response to added inspiratory resistance. To ascertain whether this response depends on the relation between inspiratory flow (V) and the pressure perturbation, we compared the responses when this relationship was made progressively less distinct by creating phase shifts between V and the resulting negative mouth pressure (Pm). This was done with an apparatus that altered Pm in proportion to V (J. Appl. Physiol. 62:2491-2499, 1987). V was passed through low-pass electronic filters of different frequency responses before serving as the command signal to the apparatus. In six normal subjects the average neural inspiratory duration (TI) response (delta TI) was sharply (P less than 0.01) reduced (0.32 +/- 0.07 to 0.12 +/- 0.07 s) when the filter's frequency response decreased from 7.5 to 3.0 Hz. The TI response was essentially flat between tube resistance (i.e., no lag, delta TI = 0.36 +/- 0.11 s) and the 7.5-Hz filter, and there was no further change in TI response with filters having a frequency response less than 3.0 Hz, with all TI responses in this range being not significant. Subjects could not consciously perceive a difference between various filter settings. We conclude that the TI response is critically influenced by the phase of the negative pressure wave relative to TI. Furthermore the TI responses are not deliberate, although consciousness is required for their elicitation.

Response of normal subjects to inspiratory resistive unloading

The purpose of this study was to examine the role of the normal inspiratory resistive load in the regulation of respiratory motor output in resting conscious humans. We used a recently described device (J. Appl. Physiol. 62: 2491-2499, 1987) to make mouth pressure during inspiration positive and proportional to inspiratory flow, thus causing inspiratory resistive unloading (IRUL); the magnitude of IRUL (delta R = -3.0 cmH2O.1(-1).s) was set so as to unload most (approximately 86% of the normal inspiratory resistance. Six conscious normal humans were studied. Driving pressure (DP) was calculated according to the method of Younes et al. (J. Appl. Physiol. 51: 963-1001, 1981), which provides the equivalent of occlusion pressure at functional residual capacity throughout the breath. IRUL resulted in small but significant changes in minute ventilation (0.6 1/min) and in end-tidal CO2 concentration (-0.11%) with no significant change in tidal volume or respiratory frequency. There was a significant shortening of the duration (neural inspiratory time) of the rising phase of the DP waveform and the shape of the rising phase became more convex to the time axis. There was no change in the average rate of rise of DP or in the duration or shape of the declining phase. We conclude that 1) the normal inspiratory resistance is an important determinant of the duration and shape of the rising phase of DP and 2) the neural responses elicited by the normal inspiratory resistance are similar to those observed with added inspiratory resistive loads.

Improvement in exercise endurance in patients with chronic airflow limitation using continuous positive airway pressure

To cope with the increased ventilatory demands of exercise, patients with severe expiratory flow limitation adopt strategies that ultimately place greater demands on their inspiratory muscles. Increased inspiratory muscle work may contribute to dyspnea causation and exercise limitation in such patients even before their ventilatory ceiling is attained. In this setting, continuous positive airway pressure (CPAP) should, by favorably affecting inspiratory muscle function and respiratory sensation, improve exercise performance. Six patients with chronic airflow limitation (CAL) (FEV1 +/- SD = 35 +/- 12% predicted) undertook constant-load, submaximal, cycle exercise at 50% of their predetermined maximal oxygen consumption: CPAP of 4 to 5 cm H2O was delivered during one exercise session and bracketed by one or two unassisted control sessions. In four patients, CPAP-assisted (4 to 5 cm H2O) exercise was bracketed by two unassisted control exercise sessions; two remaining patients undertook CPAP-assisted exercise and one unassisted control session. CPAP resulted in a significant increase in exercise endurance time (TLIM) (by 48%: CPAP TLIM (mean +/- SE) = 8.82 +/- 1.90 min; averaged control TLIM = 5.98 +/- 1.23 min (p less than 0.01). CPAP effectively ameliorated exertional dyspnea in the majority of patients; selected dyspnea ratings (Borg scale) during control (final minute) and CPAP at isotime, at comparable levels of ventilation, were (mean +/- SD) 7.83 +/- 2.25 and 5.5 +/- 2.2, respectively (p less than 0.025). Breathing frequency fell significantly during CPAP application (at isotime) by 17% (p less than 0.02); other steady-state ventilatory variables and end-expiratory lung volumes were not significantly different during CPAP and control.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of continuous positive airway pressure on respiratory sensation in patients with chronic obstructive pulmonary disease during submaximal exercise

We wished to evaluate the role of dynamic hyperinflation and dynamic airway compression as potential sources of exertional dyspnea in patients with chronic obstructive pulmonary disease (COPD). The rationale was that if such factors contribute importantly, then the administration of continuous positive airway pressure (CPAP), which serves to unload the inspiratory muscles and attenuate dynamic compression on expiration, should improve respiratory sensation. Further partitioning of CPAP into its continuous positive inspiratory pressure (CPIP) and continuous positive expiratory pressure (CPEP) components permitted an assessment of the relative importance of the above factors with respect to respiratory sensation. CPAP, CPIP, and CPEP (4 to 5 cm H2O each) were administered intermittently (for intervals of 40 to 60 s on each occasion) in random order during steady-state submaximal exercise in five patients with COPD (average FEV1, 40% predicted) and in five normal healthy subjects. Changes in the sense of breathing effort during the various pressure applications were assessed by asking the subjects to point to a category scale of -5 to +5, where -5 indicated that breathing was markedly easier and +5 indicated that breathing was markedly harder. CPAP, when administered to the COPD group, resulted in a highly significant (p less than 0.005) reduction in the sense of breathing effort. By contrast, CPAP significantly increased the sense of breathing effort in the normal group (p less than 0.01). CPIP facilitated breathing in both the COPD group and the normal group (p less than 0.05 and p less than 0.01, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

External mechanical loading in conscious humans: role of upper airway mechanoreceptors

To determine whether upper airway mechanoreceptors partly subserve the ventilatory response to external mechanical loading in conscious humans, we studied 11 laryngectomized subjects. The oropharynx (OP) or tracheostomy was selectively loaded (in random order) by attaching the mouth or tracheal tube to a special pressure-generating apparatus, and steady-state ventilatory responses were recorded. Phasic negative pressure changes generated at the OP to simulate inspiratory resistive loading, expiratory resistive unloading, and elastic loading resulted in trivial prolongation of inspiratory duration by 12, 9, and 4%, respectively; other ventilatory variables were not significantly altered. Phasic positive pressure changes at the OP that simulated inspiratory resistive unloading and expiratory resistive loading had little effect on breathing pattern. When the above loads were applied via the tracheostomy, using pressures of similar magnitude, ventilatory responses were qualitatively similar and quantitatively not significantly different from those of normal healthy controls. The results suggest that the OP does not make an important contribution to ventilatory responses during external mechanical loading in conscious humans. Loading responses to conventional mechanical loads are preserved in the absence of afferent information from the upper airways.

Steady-state response of normal subjects to an inspiratory sinusoidal pressure load

Inspiratory duration (TI) increases during inspiratory resistive loading in conscious humans. To ascertain whether this response is related to the temporal pattern of pressure perturbation (reaching a peak in early or midinspiration and declining subsequently) we compared the response of nine normal subjects to a usual resistor (narrow tube, RES) with their response when mouth pressure was reduced in a sinusoidal fashion during inspiration (SIN). Whereas the negative pressure pattern was similar with both loads (peak negative pressure near midinspiration), there was no relation between pressure and flow in the case of sinusoidal loading. Each experiment consisted of two loading periods, 4 min each, and three unloaded periods, also 4 min each, bracketing the periods of loading. The order of RES and SIN was randomized. TI during loading was compared with the average TI of the preceding and following unloaded periods. TI increased 0.74 +/- 0.12 and 0.27 +/- 0.05 (SE) s during RES and SIN, respectively (P less than 0.01). We conclude that the temporal pattern of pressure change during resistance breathing plays a small role in mediating the TI prolongation. Coupling between flow and the pressure perturbation appears to be an important determinant of TI prolongation.

Expiratory resistive loading in patients with severe chronic air-flow limitation. An evaluation of ventilatory mechanics and compensatory responses

In order to estimate the extent of dynamic compression in patients with COPD who were flow-limited at rest, we measured tidal expiratory flows before and after application of small expiratory resistive loads (ERL). We sought also to evaluate the compensatory strategies available to such patients during ERL by measuring steady-state ventilatory responses. Nine patients with severe COPD (FEV1 +/- SE, 27 +/- 3% predicted) completed the study. Mean tidal flow-volume plots representing all breaths analyzed during 4 min of ERL (resistance, 8 cm H2O/L/s) and unloaded control (4 min) were compared at isoabsolute volume in each individual subject. In 6 subjects, ERL resulted in appreciable reduction of expiratory flows throughout the tidal volume (VT) when compared with volume-matched flows during control. In the remaining subjects, expiratory flows during loading and control coincided during part of the VT. In the group as a whole at 50, 30, and 10% of VT during ERL, when mouth pressure was increased by 3, 2.5, and 2 cm H2O, respectively, flow rates were significantly lower than volume-matched flows during control (delta V, = 0.10, 0.09 and 0.06 L/s, respectively). Minute ventilation was reduced significantly by ERL, but only small insignificant changes in breathing pattern parameters occurred. End-expiratory volume increased by 0.1 L +/- 0.02 (p less than 0.005). We conclude that the majority of patients with chronic air-flow limitation do not sustain significant dynamic compression at rest, and loading response to ERL in patients with COPD are attenuated when compared with those in normal subjects.

Effect of dynamic airway compression on breathing pattern and respiratory sensation in severe chronic obstructive pulmonary disease

Patients with severe COPD are frequently flow-limited during expiration at rest. When expiratory flow is at its maximum, application of negative pressure at the mouth should accentuate dynamic compression downstream from the flow-limiting segment (FLS) without substantially affecting flow or pressure upstream. The purpose of this study was to determine the ventilatory response to such intervention and to determine its effect on respiratory sensation. Such responses should reflect the effect of airway receptors downstream from the FLS. Nine patients with severe COPD (FEV1 +/- SE = 27 +/- 3% predicted) breathed into a closed-circuit apparatus that incorporated a rolling-seal spirometer. The spirometer was fitted with a linear actuator that caused mouth pressure to become negative in proportion to expiratory flow (expiratory assistance, EA). Ventilatory responses were measured during 4 min of EA (-9.7 cm H2O/L/s) and were compared with those during control periods (4 min each) before and after this (C1 and C2). Sense of breathing effort was assessed at 1-min intervals by asking the subject to point to a category scale of 1 to 5, with 1 being minimal effort and 5 indicating that breathing was very difficult. There were small but significant (p less than 0.05) decreases in TI (mean +/- SE, -0.2 +/- 0.05 s) and TE (-0.3 +/- 0.07 s), with increases in breathing frequency (+2.25 +/- 0.7) and ventilation (+1.5 +/- 0.6 L/min). No significant changes were observed in tidal volume or end-expiratory volume. The EA caused a highly significant (p less than 0.001) increase in the sense of breathing effort.(ABSTRACT TRUNCATED AT 250 WORDS)