Telemedicine in the sleep laboratory: feasibility and economic advantages of polysomnograms transferred online.

The costs for polysomnography (PSG) and alternative diagnostic procedures for sleep-disordered breathing are challenging public health care systems. We wanted to determine if a telemedicine protocol with online transfer of PSGs from a remote site could be cost-effective and clinically useful while improving patient access to full PSG. Fifty-nine PSGs were performed in 54 pulmonary patients with suspected sleep-disordered breathing at a remote hospital. The data were transferred by File Transfer Protocol (FTP) via the Internet to Walter Reed Army Medical Center (WRAMC) for scoring and interpretation. The results were faxed back to the remote hospital. Clinical utility was assessed by evaluating the reasons for patient referral and the resulting diagnoses. The economic benefits were calculated by comparing direct expenses of the telemedicine protocol with costs for contracting PSGs at outside sleep laboratories. A total of 93% (55) of all PSGs were transferred successfully online. Of the 54 patients, 47 had PSGs performed for diagnosis (including three split-night studies), 8 underwent treatment titration, and 1 patient had both overnight studies. Diagnoses were obstructive sleep apnea in 43 patients, central sleep apnea in 2, and upper airway resistance syndrome in 2. The disease conditions were defined as severe in 27 patients, moderate in 12 patients, and mild in 8 patients. Each PSG cost $700 (including costs for lost transmissions) compared to $1,250 for referral to a private sleep laboratory. A savings of $550 per study was realized with the telemedicine protocol. The online transfer of PSGs from a remote site to a centralized sleep laboratory is technically feasible and clinically useful. Telemedicine offers an effective alternative for cost reduction in sleep medicine while improving patient access to specialized care in remote areas.

Overnight pulse oximetry for sleep-disordered breathing in adults: a review.

Pulse oximetry is a well-established tool routinely used in many settings of modern medicine to determine a patient's arterial oxygen saturation and heart rate. The decreasing size of pulse oximeters over recent years has broadened their spectrum of use. For diagnosis and treatment of sleep-disordered breathing, overnight pulse oximetry helps determine the severity of disease and is used as an economical means to detect sleep apnea. In this article, we outline the clinical utility and economical benefit of overnight pulse oximetry in sleep and breathing disorders in adults and highlight the controversies regarding its limitations as presented in published studies.

Application of telemedicine to sleep medicine.

Polysomnograms (PSGs) in specialized sleep centers with physicians and technicians trained in sleep medicine are still considered to be the most accurate form of diagnosis in patients with sleep disorders. But they are also very costly. Internet online transfer of PSGs from nonstaffed to very well-staffed sleep centers might be a solution in the future to reduce costs.

Prevalence of pulmonary disorders in patients with newly diagnosed rheumatoid arthritis.

Our objective was to determine the prevalence of airway hyperreactivity (AHR) in patients with newly diagnosed rheumatoid arthritis (RA) who had received no disease-modifying antirheumatic drugs (DMARDs) and to characterise the spectrum of lung diseases identifiable in these patients at the time of presentation. Eighteen consecutive patients with newly diagnosed RA referred to our medical centre's rheumatology clinic over 2 years underwent pulmonary evaluation with arterial blood gas analysis, chest radiographs, spirometry before and after bronchodilator medication, and body plethysmography. They returned on subsequent days in random order for methacholine inhalation challenge (MIC) and eucapnic voluntary hyperventilation (EVH) as bronchoprovocation techniques. One patient had severe obstructive disease at presentation and therefore did not undergo bronchoprovocation. We found a wide variety of pulmonary abnormalities, including two patients with hypoxia (12%), two with obstruction (12%), three with restriction (18%) and four with AHR (23%). The data also suggest a strong association between pulmonary diseases in RA and cigarette smoking. Although no single characteristic lung disease such as AHR was identified in patients presenting with RA, the association between lung disease and cigarette smoking is striking and underscores the need to emphasise smoking cessation in this patient population.

Regulatory and educational initiatives fail to promote discussions regarding end-of-life care.

We conducted an observational cohort study to determine if hospital-based, reinforcing regulatory and educational interventions could encourage physicians to discuss end-of-life (EOL) care with their patients. Specifically, we measured the effect of (1) administrative prompts to encourage discussions about EOL care and (2) a mandatory educational seminar focusing on EOL issues. Study subjects were patients consecutively admitted to the medicine service who faced an anticipated 3-year mortality rate of at least 50%. The main study endpoint was the frequency of documented EOL discussions between physicians and patients. In the inception cohort of 184 patients, physicians discussed EOL care with 64 patients (34. 8%), and in the follow-up cohort of 121 patients, 41 individuals (33. 9%) had documented discussions regarding EOL issues (P = 0.90). Actual "Do Not Resuscitate"(DNR) orders were written for 53 patients (28.8%) in the inception cohort and for 33 persons (27.3%) in the follow-up cohort (P = 0.71). We conclude that enhanced, mutually reinforcing regulatory and educational efforts focusing on EOL care proved ineffectual at promoting either discussions about EOL issues or the use of DNR orders.

Impediments to writing do-not-resuscitate orders.

BACKGROUND: Physicians are frequently unaware of their patients' desires regarding end-of-life care. Consequently, opportunities to implement do-not-resuscitate (DNR) orders are often missed. OBJECTIVE: To determine the reasons attending physicians do not write DNR orders when patients face increased mortality. METHODS: Over 4 months, the medical records of all inpatients on the General Medicine Service were reviewed at the time of discharge to identify patients with conditions predicting increased mortality. These cases were presented to a 5-member panel who decided if a DNR order was indicated. Reasons for missing DNR orders were discussed with the attending physicians. RESULTS: Of 613 consecutive admissions, the panel identified 149 patients (24%) for whom DNR orders were indicated. In 88 (59%) of these, DNR orders were absent. The lack of a DNR order did not correlate with age (P = .95), sex (P = .61), or race (P = .80). The attending physicians' explanations for not writing DNR orders in these 88 cases included the belief that the patient was not in imminent danger of death (n = 49 [56%]), the belief that the primary physician should discuss DNR issues (n = 43 [49%]), and the lack of an appropriate opportunity to discuss end-of-life issues (n = 38 [43%]). In 11 (12%) of the 88 cases, patients or their families did not accept the recommendation for a DNR order. No physicians expressed concerns regarding the morality of DNR orders, discomfort discussing end-of-life issues, or the threat of litigation as reasons for not writing a DNR order. CONCLUSIONS: Limitations in the extent and depth of the physician-patient relationship appear to be the most frequent impediments to writing DNR orders in our institution.

Performance improvement in telemedicine: the essential elements.

Performance improvement activities in telemedicine may be placed into five categories. (1) Licensing and credentialing. Telemedicine overcomes geographical boundaries, but its reach is constrained by state laws on licensing. Some states require a state license, whereas others grant "consultation exemptions" for out-of-state physicians. Simple renewable licenses do not guarantee quality. Potential solutions include a national telemedicine license or license reciprocity laws for telemedicine. (2) Data security and privacy. Telemedicine technology raises some security concerns. Differences in reporting requirements among states complicate the issue of privacy. Storage of telemedicine consultation records may help physicians document care decisions for risk management, but conventional long-term storage may not be feasible because of cost constraints and may not be required to document the encounter appropriately. (3) Informed consent. Potential failures in security and transmission are new, and should be communicated to the patient. (4) Peer review. Peer review findings encourage thorough, accurate, and legible documentation. Results should be recorded by provider and must be available during the recredentialing process. (5) Tailored performance improvement initiatives. By using established principles and techniques, performance improvement initiatives can gather, analyze, and communicate information about the cost-effectiveness of telemedicine. These performance improvement efforts are the heart of quality management and are critical to the justification of telemedicine. Walter Reed Telemedicine has put into effect a performance improvement plan in accordance with this outline. This article describes the plan and suggests it as a model for other telemedicine programs.

Do-not-resuscitate decisions in the medical ICU: comparing physician and nurse opinions.

STUDY OBJECTIVE: To determine how soon after admission to a medical ICU physicians and nurses decide that attempts at resuscitation are inappropriate and how frequently physicians and nurses disagree about do-not-resuscitate (DNR) decisions. DESIGN: Prospective, opinion survey of care providers. SETTING: Ten-bed adult medical ICU in a university-affiliated tertiary care referral hospital. PATIENTS: Consecutive adult medical ICU admissions. INTERVENTIONS: Over 10 months, physicians and nurses were surveyed independently every day regarding their opinions about DNR issues on each patient in the ICU. MEASUREMENTS: ICU day when DNR order was deemed appropriate by either physicians or nurses. RESULTS: Of 368 consecutive admissions, 84 (23%) patients were designated DNR during their ICU stay. In 6 of these 84 cases (7%), the responsible nurse did not agree that DNR orders were appropriate. In the remaining 78 patients designated DNR, the median time for physicians to recommend DNR (median, 1 day; range, 0 to 22 days) was not significantly different from the median time for nurses (median, 1 day; range, 0 to 13 days); (p=0.45). For the 284 patients not designated DNR, physicians and nurses both believed DNR was appropriate in 14 cases (5%), but a DNR order was not written five times (2%) because there was not time to do so and nine times (3%) because patient or family did not concur. Physicians and nurses disagreed about a DNR recommendation in 33 of the 284 patients not designated DNR (12%). Physicians were more likely to believe that DNR was appropriate than were nurses (p<0.0005), with physicians alone recommending DNR 29 times (10%) and nurses alone favoring DNR in four cases (1%). CONCLUSIONS: At our institution, recognition of DNR appropriateness by nurses and physicians occurs over a similar time frame. However, physicians are more likely to recommend DNR in cases of disagreement between nurses and physicians.

Eucapnic voluntary hyperventilation as a bronchoprovocation technique: development of a standarized dosing schedule in asthmatics.

A variety of dosing schedules have been reported for the hyperventilation method of broncho-provocation testing. To evaluate the effect of challenge technique on the bronchoconstrictive response, we had 16 subjects perform eucapnic voluntary hyperventilation (EVH) with dry, room temperature gas using four different dosing schedules. The hyperventilation challenge dosages included the following: (1) a target minute ventilation (VE) of 20 x FEV1 for 6 min; (2) a target VE of 15 x FEV1 for 12 min; (3) an interrupted challenge with a target VE of 30 x FEV1 for 2 min repeated 3 times; and (4) a target VE of 30 x FEV1 for 6 min. Challenges 2, 3, and 4 gave identical absolute ventilatory challenges (identical factor FEV1 x minutes) but at different VE dosages or time. Challenges 1 and 4 were of identical length, but different target VE. The mean postchallenge fall in FEV1 was 16.6 +/- 10.9%, 11.0 +/- 8.1%, 19.6 +/- 9.9%, and 26.7 +/- 11.3% for challenges 1, 2, 3, and 4, respectively. The response to an identical EVH challenge (FEV1 x 30 for 6 min) was reproducible when performed on separate days. We conclude that the challenge technique used for hyperventilation testing will have a significant impact on the bronchoconstrictive response and must be taken into account when interpreting study results. Tests may be quantitatively comparable over a narrow range of challenge time and VE. We recommend that a 6-min uninterrupted EVH challenge using dry, room temperature gas at a target VE of 30 x FEV1 be adopted as the "standard" challenge.

Interpretation of eucapnic voluntary hyperventilation in the diagnosis of asthma.

Eucapnic voluntary hyperventilation (EVH) of dry gas is a physiologic bronchoprovocation challenge useful in the diagnosis of asthma. To determine the best parameter and threshold for diagnosis and the proper timing of postchallenge measurements, we reviewed 120 challenges, comparing the decrement from baseline in FVC, FEV1, mean forced expiratory flow during the middle half of the FVC (FEF25-75%), and peak expiratory flow rate (PEFR) each at 0, 5, 10, and 20 min postchallenge. After adjustment to a standard minute ventilation of 30 times the baseline FEV1 for 6 min, the mean response by 90 mild asthmatics differed from 30 normal subjects in all four parameters (p < 0.0001). In asthmatics, maximum decline from baseline (mean +/- SEM) was as follows: FVC, 12.1 +/- 1.2%; FEV1, 19.7 +/- 1.7%; FEF 25-75%, 33.5 +/- 2.5%; and PEFR, 29.0 +/- 1.9%. Normal subjects had a maximum fall as follows: FVC, 2.9 +/- 0.7%; FEV1, 3.8 +/- 0.7%; FEF25-75%, 11.8 +/- 2.0%; and PEFR, 11.5 +/- 1.0%. Based on comparison of receiver operator characteristic curves, FEV1 was more accurate than FEF25-75% and equivalent to FVC and PEFR. A threshold of 10% change or greater in FEV1 had a specificity of 90%, with a sensitivity of 63.3%. A threshold of 15% or greater had a specificity of 100%, with a sensitivity of 53.3%. The FEV1 fell by 10% or more in 55 of 90 asthmatics at 5 or 10 min after hyperventilation. Measurements at 0 or 20 min added two additional positive responses. We conclude that in the proper clinical setting, subjects whose FEV1 declines by 10% or more at 5 or 10 min after EVH should be diagnosed as having asthma.

The refractory period after eucapnic voluntary hyperventilation challenge and its effect on challenge technique.

To evaluate whether there is a refractory period (RP) after hyperventilation challenge, we compared the bronchoconstrictive response to repetitive eucapnic voluntary hyperventilation challenge with dry, room temperature air (EVH). The serial challenges were identical with 11 known asthmatics hyperventilating for 6 min at a target minute ventilation of 30 times their FEV1 measured before either challenge. There was a significant difference between the mean postchallenge fall in FEV1 to the initial EVH challenge (27.4 +/- 9.8%) and the response to the second EVH challenge (16.1 +/- 5.9%) (p = 0.0001), indicating refractoriness. We then evaluated whether 6 min of uninterrupted EVH challenge gives a similar bronchospastic response to that which results from an equivalent (by total minute ventilation) interrupted challenge of 2 min of EVH repeated three times. The mean post-challenge fall in FEV1 in response to this interrupted challenge was 18.9 +/- 10.6%, which was significantly different from the 27.4% fall in response to 6 consecutive minutes of EVH (p = 0.036). This study demonstrates that there is a refractory period after repeated EVH challenges and this refractoriness affects the response to interrupted, or dosed, EVH challenge.

Epinephrine-induced lactic acidosis in the setting of status asthmaticus.

A relationship between intravenous epinephrine infusion and the development of lactic acidosis has been well described. We report a temporal association between the administration of subcutaneous epinephrine and the development of lactic acidosis in the setting of status asthmaticus. A 20-year-old woman with a history of asthma came to the emergency service in acute respiratory distress and was treated with subcutaneous epinephrine. Six hours later, serial arterial blood gas studies revealed the onset of a primary metabolic acidosis. Additional diagnostic studies revealed a serum lactate level of 9.5 mumol/L. The lactic acidosis resolved within 15 hours. The patient never exhibited signs of hypotension, hypoxemia, or sepsis, and other potential etiologies for lactic acidosis were excluded. We believe the events of this case constitute a new observation and theorize a mechanism of peripheral vasoconstriction and transient tissue hypoperfusion mediated by the subcutaneous epinephrine.

Refractory period during provocation with eucapnic hyperventilation and methacholine.

Eucapnic voluntary hyperventilation (EVH) and methacholine inhalation challenge (MIC) both cause bronchoconstriction in asthmatics. A refractory period, or time when the response to bronchoprovocation in a series of challenges is diminished, has been found after hyperventilation or exercise but not after MIC. We investigated whether EVH or MIC blunted the response to the other test. Sixteen asthmatics were studied on 2 d, taking both tests each day. They were randomized to either EVH or MIC first on Day 1, then the opposite order on Day 2, 6 to 14 d apart. After EVH as a first test, the mean decline in FEV1 from baseline was 18.66 +/- 4.76% (mean +/- SEM), but when EVH followed MIC, the response to EVH was reduced by 30%, to a decline in FEV1 of only 13.02 +/- 3.75% (p = 0.0026). During MIC, the mean provocation dose to cause 20% decrease in FEV1 (PD20) given as the initial challenge was 54.77 +/- 21.60 breath units, compared with 46.94 +/- 19.55 breath units when MIC followed EVH (p = 0.54). However, the subset of patients most sensitive to methacholine (PD20 < 0.1 breath unit) had changes suggestive of a refractory period after EVH, with a mean increase in the PD20 from 0.06 +/- 0.01 to 3.35 +/- 1.43 (p = 0.069). Our data show that MIC attenuates the response to subsequent challenge with EVH. Conversely, EVH may only affect subsequent MIC in those most sensitive to methacholine.

Eucapnic voluntary hyperventilation as a bronchoprovocation technique. Comparison with methacholine inhalation in asthmatics.

Methacholine inhalation challenge (MIC) is probably the most widely used and best standardized test for nonspecific bronchoprovocation challenge (BPC). There has been increasing interest in developing "physical" stimuli such as eucapnic voluntary hyperventilation (EVH) with dry gas to assess airway hyperreactivity (AHR), because of inherent problems with using a pharmacologic agent in epidemiologic surveys. To our knowledge, no studies exist that compare MIC with EVH in known asthmatics. We conducted a prospective, randomized, crossover trial with a group of subjects (n = 16) who met the American Thoracic Society definition of asthma with these objectives: (1) to compare the sensitivity of EVH with MIC; (2) to compare the quantitative response of one test with the response to the other challenge; and (3) to correlate the response of both tests with symptoms, serum IgE levels, and serum eosinophil counts. We found that (1) EVH was positive in 75 percent of cases and MIC was positive in 81 percent of cases; one subject reacted to EVH but not to MIC and vice-versa. (2) The quantitative response to one test correlated with the response to the other test (r = -0.60, p = 0.01). (3) There was a correlation between severity of asthma symptoms and the response to EVH (r = 0.62; p = 0.01), but not to MIC. (4) Response to MIC (log PD20), but not EVH, correlated with serum IgE level (r = -0.53, p = 0.04). We suggest that EVH may be used for the initial assessment of AHR in the evaluation of asthma. Eucapnic voluntary hyperventilation is a sensitive measure of AHR and it correlates well with symptoms. Furthermore, though these points were not addressed in our study, it is more physiologic than MIC, and it is easy and less expensive to perform.

Incidence of cardiac arrhythmias during intravenous pentamidine therapy in HIV-infected patients.

STUDY OBJECTIVE: There have been 15 published cases of probable pentamidine-induced torsade de pointes (TdP). A prospective analysis of this complication of therapy is valuable considering the high frequency of Pneumocystis carinii pneumonia in the AIDS population, and the role of pentamidine in its therapy. DESIGN: Open, nonrandomized, prospective study of HIV-infected patients receiving intravenous pentamidine in a 12-month period. SETTING: Walter Reed Army Medical Center, a tertiary care, referral-based facility in Washington, DC. PATIENTS: Eighteen HIV-infected patients were enrolled with informed consent; four were withdrawn from statistical analysis after receiving only one or two doses of empiric intravenously administered pentamidine. MEASUREMENTS AND RESULTS: Daily 12-lead electrocardiography, echocardiography, weekly signal-averaged electrocardiography, and weekly 24-h ambulatory electrocardiography were performed on each patient. Of the 14 subjects, 3 developed TdP. These 3 patients and 2 others developed a prolonged rate corrected, QT interval (QTc) to greater than 0.48 s (max QTc mean, 0.55 s, mean increase, 0.12 s). The QTc prolongation was noted in all five patients by the fourth daily dose (4 mg/kg/d) of pentamidine. The other 9 patients developed minimal change in QTc intervals throughout therapy (max QTc mean, 0.45 s; mean increase, 0.03 s). The maximum QTc increase was significantly different between these two cohorts (p < 0.03). The occurrence of TdP in the subgroup of patients developing prolonged QTc intervals to greater than 0.48 s (3 of 5 patients), or a change in QTc of greater than 0.08 s (3 of 4 patients) over individual baseline also was significant (p = 0.03 and p = 0.01, respectively). No baseline clinical variables associated with TdP or QTc prolongation were identified. CONCLUSION: Intravenously administered pentamidine frequently results in QTc prolongation with a subsequent risk of TdP in HIV-infected patients. All patients treated with intravenously administered pentamidine should be evaluated with baseline and daily ECGs, at least during the first week of therapy, and should be closely monitored for a change in the QT interval. An increase in QTc to above 0.48 s or greater than 0.08 s above baseline carries a significant risk for proarrhythmia, and in this instance, continuous electrocardiographic monitoring or an alternative antibiotic regimen should be considered.

The effect of pyridostigmine on bronchial hyperreactivity.

We examined the effect of pyridostigmine (PY) at a dose of 30 mg orally three times a day on nonspecific bronchial hyperreactivity in ten normal nonsmokers (NNS), ten smokers (SM), and ten mild asthmatics (AS). We conducted a double-blind, placebo-controlled, crossover trial, randomly assigning subjects to receive either placebo (PL) or PY before undergoing bronchoprovocation challenge with eucapnic voluntary hyperventilation (EVH) using dry gas. Compliance with PY was confirmed by measuring red blood cell acetylcholinesterase (Achase) levels during both days of testing. While taking PL, the mean (+/- SEM) falls in FVC and FEV1 after the bronchoprovocation were as follows: NNS, 1.0 percent (+/- 0.6) FVC and 4.3 percent (+/- 1.0) FEV1; SM, 2.4 percent (+/- 1.1) FVC and 2.7 percent (+/- 1.3) FEV1; AS, 5.3 percent (+/- 2.3) FVC and 11.5 percent (+/- 2.8) FEV1. The mean decreases in FVC and FEV1 while taking PY were as follows: NNS, 1.8 percent (+/- 0.7) FVC and 4.3 percent (+/- 0.8) FEV1; SM, 3.8 percent (+/- 1.4) FVC and 5.2 percent (+/- 1.6) FEV1; AS, 4.4 percent (+/- 1.3) FVC and 11.8 percent (+/- 2.8) FEV1. Within each category, using a paired t test to compare the results on each day of testing, no statistically significant differences were noted. Pyridostigmine at the tested dose has no significant effect on nonspecific bronchial hyperreactivity in normal NNS, SM, or AS.

Sensitivity and specificity of bronchial provocation testing. An evaluation of four techniques in exercise-induced bronchospasm.

The thresholds used to define a positive result for bronchial provocation challenges (BPC) are arbitrary. Requiring smaller decrements in expired flow to define a positive study would capture more cases of reactive airways (increased sensitivity) but would include some "normal" responses (decreased specificity). To examine the relationship between threshold definition and the ability to correctly classify subjects as either normal or as having airways hyperresponsiveness (AHR), four different BPC tests were administered on different days to 20 patients with a clinical diagnosis of exercise-induced bronchospasm (EIB) and 20 control subjects. The four BPC tests were indoor exercise on a cycle ergometer, methacholine inhalation challenge (MIC), eucapnic voluntary hyperventilation (EVH) with dry gas, and EVH with cold gas. Our results indicate that the thresholds which best separate the two groups are different for each of the four BPC techniques. For methacholine inhalation (MIC), a fall in FEV1 (d%FEV1) of 15 percent or greater at 188 cumulative breath units was 100 percent specific for AHR but had a sensitivity of only 55 percent. Eucapnic voluntary hyperventilation (EVH) with room temperature dry gas was 100 percent specific at a d%FEV1 of 11 percent, but, at that threshold, sensitivity was only 50 percent. EVH with cold air was 100 percent specific at a d%FEV1 of 12 percent but sensitivity was only 35 percent. The bicycle ergometer challenge was far too insensitive to be of value in evaluating AHR. Based on their respective receiver operating characteristic curves, the best separation of the two subject groups occurred at a d%FEV1 of 5 percent and 12 percent for the two EVH techniques and MIC, respectively. An individual's response to one test was highly correlated with the response to either of the other two (r = 0.66, p less than 0.001 for dry vs cold gas EVH; r = 0.56, p less than 0.001 for dry gas EVH vs methacholine; and r = 0.69, p less than 0.001 for cold gas EVH vs methacholine). Thus, MIC and EVH techniques are equally useful in defining AHR and each has its optimal threshold for a positive test result.

Oxygen consumption and ventilation during normal labor.

Oxygen consumption (VO2) and minute ventilation (VE) were measured breath-by-breath for 10 min periods in the third trimester of pregnancy in 16 healthy women. These measurements were repeated during the first stage of labor in eight of the women. The 10-min mean VO2 was 3.56 ml/kg/min (+/- 0.82 SD) at term and 4.28 ml/kg/min (+/- 0.93) during labor, for an average increase of 23 percent (+/- 28 percent, p = 0.04) from third trimester to labor. The mean VE was 0.15 L/kg/min (+/- 0.03) at term and increased significantly (p = 0.05) to 0.24 L/kg/min (+/- 0.11) during labor for an average increase in VE of 65 percent (+/- 78 percent). Peak VO2 and VE occurred during contractions with five-breath average peak VO2 being 86 percent (+/- 53%) above the 10-min mean value at term and VE increasing 167 percent (+/- 154 percent) from third trimester to peak values during labor. These data may be useful in identifying patients at risk for developing respiratory insufficiency during labor. We propose an algorithm for approaching the obstetric patient with respiratory disease.