Abstract
Objective
Enhancing ventilatory effort during pulmonary function testing can help reveal flow limitations not evident in normal tidal breathing. This study aimed to assess the efficacy and tolerability of using a CO2/O2 gas mixture to enhance tidal breathing with a barometric whole-body plethysmography system in both healthy cats and those with feline lower airway disease (FLAD).
Methods
This prospective study included healthy cats and those with FLAD, which underwent pulmonary function testing and were exposed to a 10% CO2/90% O2 gas mixture in a barometric whole-body plethysmography chamber, with CO2 concentrations maintained within the target range of 5% to 10%.
Results
A total of 10 healthy cats and 15 FLAD cats were included. In healthy cats, tidal volume, minute volume, peak inspiratory flow, and peak expiratory flow per kilogram body weight increased significantly by medians of 4.3-, 3.5-, 3.1-, and 4.0-fold, respectively (P = .005). Cats with FLAD showed similar results, with 4.1-, 3.2-, 2.8-, and 3.7-fold increases (P < .001). Respiratory rate decreased in both healthy (52 to 40 breaths/min; P = .005) and FLAD cats (57 to 45 breaths/min; P = .04) after CO2 enhancement. All cats tolerated the CO2/O2 gas mixture well, with recovery within 60 to 120 seconds after returning to room air.
Conclusions
A CO2/O2 gas mixture successfully enhanced ventilatory variables in tidal breathing analysis and showed good tolerability in both healthy and FLAD cats.
Clinical Relevance
This approach provides a practical option for short-term breathing effort enhancement in cats for clinical settings.
Pulmonary function testing is important for evaluating the respiratory system, and barometric whole-body plethysmography (BWBP) has been 1 of the modalities used in clinical assessments of cats over the past decades.1–7 The BWBP system enables animals to move freely in a transparent chamber during pulmonary function testing, providing a nonrestrained method to assess ventilation.8–10 The net difference between nasal airflow and thoracic expansion produces pseudoflow signals, which correspond to the animal’s respiratory airflow.11,12 Due to its noninvasive and cat-friendly nature, which minimizes stress without the need for restraint, BWBP has gained popularity in clinical feline medicine for evaluating various diseases and abnormalities, such as feline lower airway disease (FLAD), parasite-associated lung disease, obesity, and respiratory distress from various etiologies.1–7,13,14
Noninvasive pulmonary function assessments in conscious animals in veterinary clinical medicine are generally limited to tidal breathing.12 Consequently, a major challenge in small animal pulmonary function testing is the relatively lower sensitivity and reproducibility of tidal breathing analysis compared to forced maneuvers that require maximal respiratory effort, which are routinely used in human medicine.15–17 Tidal breathing measurements inherently have a wide range of normal values across ventilatory parameters and are less sensitive in detecting subtle or mild abnormalities, lacking the maximal respiratory effort that requires the patient to follow specific instructions.15,16 To address this limitation, various attempts have been made in veterinary medicine to stimulate increased ventilatory effort in animals.16,18 Among these, inhaling 5% to 10% CO2 has successfully demonstrated a significant increase in tidal volume (VT) and minute ventilation (MV) in cats and has been shown to unmask flow limitations that were barely evident during normal tidal breathing.16
However, a previous study19 to use CO2 for breathing enhancement in cats was conducted with a facemask connected to a prefilled bag and a spirometric system, so it is unclear if this approach can be adapted to the BWBP system. Moreover, while a previous study found that most healthy cats tolerated 5% to 10% CO2 well, only case-based information was available for cats with respiratory disease, with no other published data at present.16,19 Therefore, the aim of this study was to assess the efficacy and tolerability of using a CO2/O2 gas mixture for tidal breathing enhancement with a BWBP system in healthy cats and clinical cats with FLAD.
Methods
Animals and study design
This study was designed to include 2 groups of cats. The first group consisted of 10 healthy cats without respiratory signs, history of respiratory disease, or exposure to cigarette smoke, recruited from university staff, veterinary students, and volunteer pet owners. The second group included 15 client-owned cats diagnosed with FLAD. The diagnosis of FLAD was based on clinical signs, a compatible history, and bronchoalveolar lavage analysis indicating eosinophilic, neutrophilic, or mixed-type inflammatory airway disease, along with microbiological examination ruling out other pathogens causing lower airway disease. When the owner declined bronchoalveolar lavage, a clinical diagnosis of FLAD was made based on the following criteria: (1) a history of chronic coughing or episodic respiratory distress with spontaneous recovery, (2) radiographic findings of a bronchial or bronchointerstitial pattern, (3) a history of or subsequent response to glucocorticoid treatment, (4) an absence of pleural space disease and congestive heart failure based on radiographic or ultrasonographic findings or both, and (5) no evidence of upper airway infection, pneumonia, or other infectious etiologies, including increased body temperature, leukocytosis, alveolar infiltration on thoracic radiographs, or other related clinical signs.
Cat owners were provided with information on the anticipated effects and safety of using 10% CO2 based on findings from a previous feline study reported in the literature.16 Additionally, all owners were informed that a 10% CO2 and 90% O2 gas mixture was chosen instead of nitrogen as a balance gas to prevent potential hypoxemia. Written informed consent was obtained from all owners prior to participation, and this study was conducted with the approval of the Research Ethics Committee of National Taiwan University Veterinary Hospital and the IACUC of National Taiwan University (approval No. NTU104-EL-00010).
To evaluate the efficacy and tolerance of enhanced tidal breathing, respiratory parameters were initially recorded under room air conditions and subsequently recorded again after exposure to a 10% CO2 and 90% O2 gas mixture.
Barometric whole-body plethysmography recording
Each BWBP recording (Figure 1) was conducted after system calibration in accordance with the manufacturer’s guidelines. Cats were placed in a transparent Plexiglas chamber (51 cm X 30 cm X 25 cm) without restraint in a quiet room with the owner present, and an acclimation period was allowed until the cat sat or lay in a comfortable position with stable breathing signals as previously described.14,20 For recording natural tidal breathing under room air, a bias flow of 6 L/min was provided to prevent CO2 accumulation, and adjustments were made for enhanced breathing recordings as described below. Breathing signals detected by a differential pressure transducer were amplified, digitized, and analyzed. Nonrespiratory artifacts, such as movements and vocalizations, were excluded using both the software’s automatic rejection setting (Biosystem XA, version 2.11.0; Buxco Electronics) and manual elimination through simultaneous visual inspection.20 Conventional BWBP parameters, including respiratory rate (RR), VT per kilogram body weight (BW), MV per kilogram BW, peak inspiratory flow (PIF) per kilogram BW, and peak expiratory flow (PEF) per kilogram BW, were calculated from a breath-by-breath analysis of box flow waveforms.
A—Barometric whole-body plethysmography (BWBP) system used in cats for pulmonary function testing. Cats were placed in the BWBP chamber, where their breathing generated both airflow at the nasal opening and thoracic expansion due to warming and humidifying air during inhalation. The net voltage difference between these 2 signals was detected by a pneumotachograph using a differential pressure transducer and subsequently amplified and digitized by the preamplifier. For recording natural tidal breathing under room air, a bias flow was provided to prevent CO2 accumulation. B—Application of a CO2/O2 gas mixture to enhance breathing effort. For enhanced tidal breathing assessments, the cat was temporarily removed while a 10% CO2/90% O2 gas mixture was administered into the chamber. A CO2 detector monitored the concentration, and the cat was reintroduced once the CO2 level reached a minimum of 7.5%.
Citation: American Journal of Veterinary Research 86, 4; 10.2460/ajvr.24.11.0356
Enhanced breathing using a CO2/O2 gas mixture
After baseline BWBP recordings over a 5-minute period in room air, the cat was temporarily removed from the chamber, and a gas mixture of 10% CO2 and 90% O2 was introduced at a high flow rate (> 10 L/min) through a designated inlet in the chamber wall while a side outlet allowed gradual expulsion of ambient air. The gradual increase in CO2 concentration inside the chamber was continuously monitored by a CO2 detector until it reached a minimum of 7.5%. The cat was then reintroduced, minimizing gas leakage by carefully managing the chamber lid opening. After the cat was placed back in the chamber, where CO2 levels were expected to drop briefly, the gas mixture continued to flow at a reduced rate of 4 to 8 L/min. Throughout the recording, the CO2 concentration within the BWBP chamber was measured at regular intervals of 30 to 60 seconds and closely monitored to ensure it remained within the target range of 5% to 10% (Figure 1). Respiratory parameters were recorded over a 5-minute period.
The efficacy of enhanced breathing was assessed by calculating the fold increase in VT per kilogram BW, MV per kilogram BW, PIF per kilogram BW, and PEF per kilogram BW under CO2/O2 exposure compared to room air. Tolerability was evaluated based on observed behavior in the chamber and recovery status after returning to room air.
Statistical analysis
All statistical analyses were performed using commercially available statistical software (SPSS, version 27; IBM Corp). The Shapiro-Wilk test assessed the normal distribution of continuous variables. Data with normal distribution were reported as mean ± SD, whereas non-normally distributed data were presented as median with range. Variables were compared between healthy and FLAD cats using independent t tests and Mann-Whitney tests. Ventilatory variables between room air and CO2/O2 conditions were compared using the Wilcoxon signed-rank test. The fold increase in VT, MV, PIF, and PEF was analyzed between room air and CO2/O2 conditions for both healthy and FLAD cats. The reference intervals for the enhancement effect of the CO2/O2 gas mixture on ventilatory variables were determined based on 95% CIs in healthy cats. A P value of less than .05 was considered statistically significant.
Results
The age and BW of the study population were 6.3 ± 4.2 years and 5.0 ± 1.0 kg, respectively, with a median 9-point body condition score of 5 (range, 4 to 8). There were no significant differences between healthy and FLAD cats regarding their baseline characteristics (Table 1).
Baseline characteristics of healthy cats and feline lower airway disease (FLAD) cats.
| Variables | Healthy cats (n = 10) | FLAD cats (n = 15) | P value |
|---|---|---|---|
| Age (y) | 4.8 ± 4.8 | 7.2 ± 3.8 | .18 |
| BW (kg) | 5.2 ± 0.9 | 4.9 ± 1.1 | .43 |
| BCS | 5 (5–7) | 5 (4–8) | .50 |
Values reported are mean ± SD and median (range).
BCS = Body condition score. BW = Body weight.
An independent t test and Mann-Whitney test were used to compare values.
Resultant CO2 concentration in the BWBP chamber
The CO2 concentration within the BWBP chamber was successfully maintained within the target range of 5% to 10% during recording for all 25 cats. When a cat was initially placed in the chamber with a minimum CO2 concentration of 7.5%, the levels briefly dropped (ranging from 5.0% to 7.0% at the beginning of the 5-minute recording) but stabilized within the target range as the gas mixture continued to flow at a reduced rate of 4 to 8 L/min. Exhaled CO2 from the cat further contributed to maintaining the CO2 levels. A median of 6 CO2 detector readings were recorded during the 5-minute recording period, with CO2 concentrations reaching 5.7% to 7.9% by the end.
Group 1: efficacy of breath enhancement and tolerability in healthy cats
In the healthy cat group, administration of a 10% CO2/90% O2 gas mixture led to significant enhancements in tidal breathing parameters (Figure 2). Compared to baseline room air measurements, VT per kilogram BW significantly increased by a median of 4.3-fold (P = .005) and MV per kilogram BW by a median of 3.5-fold (P = .005). Peak inspiratory flow per kilogram BW and PEF per kilogram BW also significantly increased, with a median of 3.1-fold (range, 2.3 to 3.7; P = .005) and 4.0-fold (range, 3.1 to 9.1; P = .005), respectively. Additionally, RR decreased from a median of 52 breaths/min (bpm; range, 42 to 68) to 40 bpm (range, 38 to 45; P = .005). Notable breathing effort was observed within 10 to 30 seconds of reintroduction to the chamber. All healthy cats tolerated the chamber environment with increased CO2 and O2 concentrations well, with only a few exhibiting intermittent licking or posture changes, which were considered acceptable by the clinicians and owners monitoring the process. Recovery times for all healthy cats were within 60 to 120 seconds after returning to room air, defined as the time taken to return to pre-exposure breathing status.
Administration of a CO2/O2 gas mixture led to significant enhancements in tidal breathing demonstrated in a healthy cat (A) and a cat with feline lower airway disease (B). Notable increases in volume (x-axis of the pseudo tidal breathing flow-volume loop) and flow rate (y-axis) are illustrated in both the flow-time plot and the flow-volume loop.
Citation: American Journal of Veterinary Research 86, 4; 10.2460/ajvr.24.11.0356
Group 2: efficacy of breath enhancement and tolerability in FLAD cats
In the FLAD group, significant enhancements in tidal breathing parameters were also observed when the CO2/O2 gas mixture was introduced into the chamber (Figure 2). Compared to ventilatory variables obtained from baseline room air measurements, VT per kilogram BW significantly increased by a median of 4.1-fold (P < .001) and MV/BW by a median of 3.2-fold (P < .001). Peak inspiratory flow per kilogram BW and PEF/BW also significantly increased, with PIF/BW showing a median increase of 2.8-fold (range, 1.9 to 3.6; P < .001) and PEF/BW increasing by 3.7-fold (range, 2.4 to 5.5; P < .001). The RR also significantly decreased, from a median of 57 bpm (range, 39 to 106) to 45 bpm (range, 25 to 79) (P = .04). Notable breathing effort was observed within 10 to 30 seconds after reintroduction into the chamber with the CO2/O2 gas mixture in all FLAD cats. There was no significant difference in the enhancement effect of the CO2/O2 gas mixture on ventilatory variables between healthy and FLAD cats. All FLAD cats tolerated CO2 enhancement well, showing responses during breathing of the CO2/O2 gas mixture and recovery times (within 60 to 120 seconds) after returning to room air conditions comparable to those observed in healthy cats.
Reference range
Reference intervals for the enhancement effect of the CO2/O2 gas mixture on ventilatory variables were established in healthy cats and are listed in Table 2.
Reference intervals for the enhancement effect of the CO2/O2 gas mixture on ventilatory variables calculated from the 95% CIs in healthy cats.
| Expected fold increase (after breathing CO2/O2 gas mixture) | Mean | Lower limit | Upper limit |
|---|---|---|---|
| VT per kg BW | 4.48 | 3.72 | 5.23 |
| MV per kg BW | 3.52 | 3.11 | 3.94 |
| PIF per kg BW | 3.08 | 2.73 | 3.43 |
| PEF per kg BW | 4.52 | 3.29 | 5.75 |
MV = Minute volume. PEF = Peak expiratory flow. PIF = Peak inspiratory flow. VT = Tidal volume.
Discussion
This study assessed the efficacy and tolerability of enhanced tidal breathing using a CO2/O2 gas mixture in a BWBP system for both healthy cats and cats with FLAD. The CO2 concentration in the chamber was successfully maintained within the targeted range of 5% to 10%. This protocol effectively enhanced VT and MV in healthy cats by a median of 4.3-fold and 3.5-fold, respectively. The breathing rate significantly decreased, indicating a shift toward deeper, slower breaths under CO2 enhancement. Similar enhancement effects were observed in cats with FLAD, demonstrating the applicability of the protocol for cats with respiratory conditions. Overall, both healthy and FLAD cats tolerated breathing the CO2/O2 gas mixture well, with recovery to normal tidal breathing occurring quickly, typically within 1 to 2 minutes upon returning to room air conditions.
The purpose of “enhancing” tidal breathing is to effectively increase the sensitivity and reproducibility of pulmonary function assessment.16 A forced maneuver is often preferred in pulmonary function assessment for identifying airflow limitation as it offers a more sensitive methodology for evaluating obstructive lower airway disease. However, for subjects unable to perform forced maneuvers, such as human infants and clinical animals, alternative methods have been developed to enhance breathing effort. For example, rapid thoracoabdominal compression using an inflatable jacket has been applied to simulate forced expiration in infants and animals, generating flow-volume curves similar to those seen in adults; however, this technique requires specialized, costly equipment, which limits its accessibility.21,22 Intravenous injections with doxapram hydrochloride have also been effectively used to enhance breathing by pharmacologically stimulating the respiratory center in the brain,23,24 though its duration of action is brief, typically lasting within 2 minutes,24 making it less suitable for longer assessments. Breathing in 10% CO2 has been shown to make flow limitations more detectable than during standard tidal breathing.16 Alternatively, controlled CO2 inhalation offers a practical and sustainable approach for enhancing tidal breathing, requiring minimal equipment and yielding consistent results, making it a preferred method in our study.16,19
The efficacy of enhanced breathing observed in our study surpassed that reported in previous literature. A prior study observed a 2-to-3-fold enhancement in VT when administering CO2 at concentrations of 6% to 10% in healthy cats.16,19 In our study, an even greater increase was noted, with VT reaching a 4.3-fold and MV a 3.5-fold rise while breathing CO2 at a concentration ranging from 5.7% to 7.9%, which was similar to that in the aforementioned study. According to a recent study14 using BWBP to assess respiratory distress in cats, an increase of more than 1.4-fold in MV from the normal range was indicative of abnormally increased breathing effort. Therefore, an enhancement exceeding 2-fold is sufficient to represent effective breathing enhancement. The stronger enhancement effect in our study might be due to differences in the balance gas used, potentially eliciting a different response in the respiratory center. McKiernan et al19 used a mixture containing 21% O2 with nitrogen as the balance gas,16 whereas only O2 was used as the balance gas in the current study, resulting in an O2 concentration greater than 21%. Another possible explanation is the variation in the cats’ breathing status across conditions. In the study by McKiernan et al,19 cats were placed with a mask connected to a spirometric system, whereas in our study, cats were unrestrained in a chamber with a BWBP system. Thus, the manner of tidal breathing in cats may differ when breathing through a mask compared to breathing freely within an unrestrained chamber setting.
The tolerability of breathing CO2 at concentrations of 2.5%, 5.0%, 7.5%, 10%, or 12.5% with 21% O2 and nitrogen as the balance gas has been evaluated in healthy cats.19 Although most healthy cats tolerated CO2 concentrations of 2.5% to 10% well, occasional aversion to the facemask was observed, possibly due to the irritant effects of gas mixtures with higher CO2 concentrations.16 This odor may explain why some of the cats in our study showed intermittent licking and posture changes during the process, although these responses were minimal. While the potential adverse effects of CO2 inhalation warrant careful consideration, particularly at higher concentrations, previous researchers have suggested that increasing the O2 content could help mitigate these effects.16 At the targeted CO2 concentrations of 5% to 10%, no significant adverse effects were noted in either healthy cats or FLAD cats in our study. Additionally, the inclusion of O2 in our CO2 mixture likely reduced the risk of hypoxia, which can otherwise potentiate the ventilatory response to CO2. This combined CO2 and O2 approach provides a safer means of enhancing tidal breathing, especially for those with compromised respiratory health.
For safety considerations, our protocol ensures that the inhaled CO2 concentration would not exceed 10% during the BWBP recording period, providing additional protection against excessive CO2 exposure. The high solubility of CO2 facilitates its rapid diffusion across the alveolar membrane, enabling efficient elimination from the lungs in response to elevated concentrations in healthy individuals.25 This aligns with the observation in our study that recovery times after CO2 exposure, when the cats returned to room air conditions, were generally short (within 1 to 2 minutes), indicating efficient elimination of CO2 from the body. However, it is important to consider that CO2 may exacerbate breathing effort and compromise cats with respiratory disease. Although cats with FLAD, representing bronchial-level etiology, tolerated the protocol well in our study, diffusion capacity could be impaired in certain conditions, which may require cautious evaluation. For example, cats with interstitial lung disease, various types of restrictive lung diseases, or diffuse alveolar pathology may have compromised diffusion capacity as well as those already exhibiting labored breathing.14,26–29 For clinical cats with these conditions, CO2 inhalation could pose additional risks, and the suitability of enhanced breathing assessments should be carefully considered.
One limitation of this study is that, although the gas mixture delivered to the chamber was controlled and the CO2 concentration was monitored, the exact gas composition that each cat actually inhaled could not be fully standardized or determined. While this limitation affected the precise understanding of the inhaled gas composition, it did not impact the effectiveness of the methodology in successfully enhancing breathing in cats using a BWBP system. Second, unlike the fixed CO2 concentrations used in a previous study19 with a spirometric system where gas was delivered from a prefilled bag, the CO2 concentration in the BWBP chamber was not steady but gradually increased. Given that ventilatory responses to increasing CO2 levels are linear,16 the results of the present study do not represent the ventilatory response to a specific CO2 concentration. Instead, our data reflect the ventilatory response averaged from breaths over a short period within a CO2 concentration range of 5% to 10%. While the protocol reported in this study is not interchangeable with the previous method using a spirometric system, both methodologies can effectively achieve the goal of enhanced breathing for clinical application. One additional limitation is the inability to perform simultaneous auscultation on cats within the BWBP chamber during periods of enhanced breathing effort, which could potentially enhance sensitivity for detecting respiratory abnormalities. However, auscultation can still be attempted during the 1 to 2 minutes of recovery time as the cats continue to exhibit increased breathing effort in the short term.
In conclusion, this study demonstrated that the use of a CO2/O2 gas mixture effectively enhanced tidal breathing in both healthy cats and those with FLAD when evaluated using a BWBP system. The protocol successfully maintained CO2 levels within the desired range of 5% to 10%, resulting in significant increases in VT, MV, and flow rates, along with a decrease in RR, reflecting a shift toward deeper and slower breaths under CO2 enhancement. Both healthy and diseased cats tolerated the CO2 enhancement well, showing rapid recovery upon returning to room air, with the increased O2 as the balance gas contributing to the protocol’s safety in clinical settings. This approach offers a practical and feasible option for a short-term enhancement of breathing effort in cats, which could theoretically improve sensitivity in detecting subtle or mild airflow limitations in pulmonary function assessments and future clinical research.
Acknowledgments
Part of the data was presented in the format of an oral presentation at the 36th Veterinary Comparative Respiratory Society symposium, October 7–10, 2018, Auburn, Alabama, United States.
Disclosures
The authors have nothing to disclose.
ChatGPT, an AI-assisted technology, was partially employed to modify grammar in this manuscript and did not generate any original content.
Funding
Part of this research was supported by the Grant NSTC 111–2313-B-002–062 from the National Science and Technology Council, Taiwan. The manuscript was funded by National Taiwan University (NTU-CDP-114L7748) and the National Science and Technology Council, Taiwan.
ORCID
W. T. Chang https://orcid.org/0009-0009-3366-9046
P. Y. Lo https://orcid.org/0009-0003-5769-9588
H. D. Wu https://orcid.org/0000-0001-6279-0384
H. W. Chen https://orcid.org/0000-0002-0595-3420
C. H. Lin https://orcid.org/0000-0002-5276-3179
References
- 1.↑
Allerton FJ, Leemans J, Tual C, Bernaerts F, Kirschvink N, Clercx C. Correlation of bronchoalveolar eosinophilic percentage with airway responsiveness in cats with chronic bronchial disease. J Small Anim Pract. 2013;54(5):258–264. doi:10.1111/jsap.12070
- 2.
Hirt RA, Galler A, Shibly S, Bilek A. Airway hyperresponsiveness to adenosine 5’-monophosphate in feline chronic inflammatory lower airway disease. Vet J. 2011;187(1):54–59. doi:10.1016/j.tvjl.2009.10.007
- 3.
García-Guasch L, Caro-Vadillo A, Manubens-Grau J, Carretón E, Camacho AA, Montoya-Alonso JA. Pulmonary function in obese vs non-obese cats. J Feline Med Surg. 2015;17(6):494–499. doi:10.1177/1098612X14548786
- 4.
García-Guasch L, Caro-Vadillo A, Manubens-Grau J, et al. Evaluation of pulmonary function variables by using plethysmography in cats with respiratory disease associated to dirofilaria immitis. Vet Parasitol. 2012;187(1–2):254–258. doi:10.1016/j.vetpar.2011.12.013
- 5.
Gareis H, Hörner-Schmid L, Zablotski Y, Palić J, Schulz B. Evaluation of barometric whole-body plethysmography for therapy monitoring in cats with feline lower airway disease. PLoS One. 2022;17(10):e0276927. doi:10.1371/journal.pone.0276927
- 6.
Lin CH, Lee JJ, Liu CH. Functional assessment of expiratory flow pattern in feline lower airway disease. J Feline Med Surg. 2014;16(8):616–622. doi:10.1177/1098612X13515461
- 7.↑
Lin CH, Wu HD, Lee JJ, Liu CH. Functional phenotype and its correlation with therapeutic response and inflammatory type of bronchoalveolar lavage fluid in feline lower airway disease. J Vet Intern Med. 2015;29(1):88–96. doi:10.1111/jvim.12494
- 8.↑
Hamelmann E, Schwarze J, Takeda K, et al. Noninvasive measurement of airway responsiveness in allergic mice using barometric plethysmography. Am J Respir Crit Care Med. 1997;156(3 pt 1):766–775. doi:10.1164/ajrccm.156.3.9606031
- 9.
Hoffman AM, Dhupa N, Cimetti L. Airway reactivity measured by barometric whole-body plethysmography in healthy cats. Am J Vet Res. 1999;60(12):1487–1492. doi:10.2460/ajvr.1999.60.12.1487
- 10.↑
Talavera J, Kirschvink N, Schuller S, et al. Evaluation of respiratory function by barometric whole-body plethysmography in healthy dogs. Vet J. 2006;172(1):67–77. doi:10.1016/j.tvjl.2005.04.019
- 11.↑
Lomask M. Further exploration of the Penh parameter. Exp Toxicol Pathol. 2006;57(suppl 2):13–20. doi:10.1016/j.etp.2006.02.014
- 12.↑
Rozanski EA, Hoffman AM. Pulmonary function testing in small animals. Clin Tech Small Anim Pract. 1999;14(4):237–241. doi:10.1016/S1096-2867(99)80017-6
- 13.↑
García-Guasch L, Manubens J, Laporta M, Carretón E, Montoya-Alonso JA. First case reported of bronchoconstriction in feline aelurostrongylosis by using barometric whole-body plethysmography. J Hell Vet Med Soc. 2015;66(2):101–105. doi:10.12681/jhvms.15615
- 14.↑
Chang WT, Lin CH, Chang CH, Lo PY, Chen HW, Wu HD. Assessing breathing effort by barometric whole-body plethysmography and its relationship with prognosis in client-owned cats with respiratory distress. J Vet Intern Med. 2024;38(3):1718–1724. doi:10.1111/jvim.17069
- 15.↑
Beydon N, Davis SD, Lombardi E, et al. An official American Thoracic Society/European Respiratory Society statement: pulmonary function testing in preschool children. Am J Respir Crit Care Med. 2007;175(12):1304–1345. doi:10.1164/rccm.200605-642ST
- 16.↑
Dye JA, Costa DL. Pulmonary mechanics. In: King LG, ed. Textbook of Respiratory Disease in Dogs and Cats. Saunders; 2004:157–175.
- 17.↑
Stanojevic S, Kaminsky DA, Miller MR, et al. ERS/ATS technical standard on interpretive strategies for routine lung function tests. Eur Respir J. 2022;60(1):2101499. doi:10.1183/13993003.01499-2021
- 18.↑
Couëtil LL, Rosenthal FS, Simpson CM. Forced expiration: a test for airflow obstruction in horses. J Appl Physiol (1985). 2000;88(5):1870–1879. doi:10.1152/jappl.2000.88.5.1870
- 19.↑
McKiernan BC, Rozanski EA, Jones SE. The effect of CO2 on tidal breathing flow volume (TBFVL) loops in conscious cats. In: Proceedings of the 8th Comparative Respiratory Symposium. Veterinary Comparative Respiratory Society; 1989:23.
- 20.↑
Lin CH, Wu HD, Lo PY, Lee JJ, Liu CH. Simultaneous visual inspection for barometric whole-body plethysmography waveforms during pulmonary function testing in client-owned cats. J Feline Med Surg. 2016;18(10):761–767. doi:10.1177/1098612X15592662
- 21.↑
Bark H, Epstein A, Bar-Yishay E, Putilov A, Godfrey S. Non-invasive forced expiratory flow-volume curves to measure lung function in cats. Respir Physiol Neurobiol. 2007;155(1):49–54. doi:10.1016/j.resp.2006.03.005
- 22.↑
Mallol J, Aguirre V. Advances in the study of infant lung function: forced expiratory maneuvers from an increased lung volume. Arch Bronconeumol. 2007;43(4):233–238. doi:10.1157/13100543
- 23.↑
Greenfield CL, Alsup JC, Hungerford LL, McKiernan BC. Bilateral recurrent laryngeal neurectomy as a model for the study of idiopathic canine laryngeal paralysis. Can Vet J. 1997;38(3):163–167.
- 24.↑
Manens J, Bolognin M, Bernaerts F, Diez M, Kirschvink N, Clercx C. Effects of obesity on lung function and airway reactivity in healthy dogs. Vet J. 2012;193(1):217–221. doi:10.1016/j.tvjl.2011.10.013
- 26.↑
Cohn LA, Norris CR, Hawkins EC, Dye JA, Johnson CA, Williams KJ. Identification and characterization of an idiopathic pulmonary fibrosis-like condition in cats. J Vet Intern Med. 2004;18(5):632–641. doi:10.1892/0891-6640(2004)18<632:IACOAI>2.0.CO;2
- 27.
Dear JD, Vernau W, Johnson EG, Hulsebosch SE, Johnson LR. Clinicopathologic and radiographic features in 33 cats with aspiration and 26 cats with bronchopneumonia (2007-2017). J Vet Intern Med. 2021;35(1):480–489. doi:10.1111/jvim.16005
- 28.
König A, Hartmann K, Mueller RS, Wess G, Schulz BS. Retrospective analysis of pleural effusion in cats. J Feline Med Surg. 2019;21(12):1102–1110. doi:10.1177/1098612X18816489
- 29.↑
Reinero C. Interstitial lung diseases in dogs and cats part II: known cause and other discrete forms. Vet J. 2019;243:55–64. doi:10.1016/j.tvjl.2018.11.011
