Description of the condition
"Life is made up of sobs, sniffles and smiles, with sniffles predominating" (Adams 1967). Sniffles, common colds and other acute respiratory infections (ARIs) are the most common acute illnesses. They account for about 40% of employee absenteeism and about 30% of absenteeism from school (NCHSP 1985; Predy 2005). Separate studies from families have shown that the average pre-school child has six to 10 colds per year and the average adult has two to four colds per year (Monto 1974). Billions of dollars are used in caring for these patients.
Description of the intervention
Many remedial measures, such as antihistamines, decongestants, intranasal ipratropium bromide, vitamin C, interferon and traditional remedies such as Chinese herbs, garlic and ginseng etc, are used in the treatment of the common cold (AlBalawi 2011; De Sutter 2012; Linde 2008; Singh 2011a; Smith 1993; Zhang 2009). Inhaling warm, damp air is thought to offer relief from symptoms of the common cold and other ARIs. Hot water, hot soup and tea have been used for centuries for this purpose and have become subjects of scientific investigations (Saketkhoo 1978).
How the intervention might work
Lwoff 1969 suggested that raising the mucosal temperature to 43°C for three periods of 30 minutes will block rhinoviral replication and stop the common cold. Studies of the effect of heated, humidified air suggest that raising nasal mucosal temperature may indeed inhibit rhinoviral replication (Forstall 1994). A standard piece of equipment to do this (rhinotherm) was developed in Israel and it was claimed that 80% of the participants who used this apparatus in the early stages of the cold felt better the next day. This equipment has been used in several trials involving patients and volunteers infected with the common cold virus and the studies have shown conflicting results (Forstall 1994; Macknin 1990; Ophir 1987; Tyrrell 1989a; Tyrrell 1989b).
Why it is important to do this review
A billion dollar industry thrives on treatments for alleviating symptoms of the common cold. Treatments range from antihistamines, decongestants, antibiotics, vitamins and minerals from the conventional medical system to several physical therapies ranging from inhaling steam with herbs, 'neti' treatment and 'Pranayaam' from the complementary systems of medicine. The common cold and allergic rhinitis constitute a global health problem that affects social life, sleep, school and work performance and is likely to impose a substantial economic burden on society because of absence from work and reduced working capacity. A study was conducted to estimate productivity lost to the common cold by using a telephone-administered survey that measured three sources of loss: absenteeism, on-the-job productivity and caregiver absenteeism (Bramley 2002). Each cold experienced by a working adult caused an average of 8.7 lost work hours (2.8 absenteeism hours and 5.9 hours of on-the-job loss), and 1.2 work hours were lost because of attending to children under the age of 13 who were suffering from colds. We conclude that the economic cost of lost productivity due to the common cold approaches nearly USD 25 billion, of which USD 16.6 billion is attributed to on-the-job productivity loss, USD 8 billion is attributed to absenteeism, and USD 230 million (0.23 billion) is attributed to caregiver absenteeism.
Hence it is extremely important that the scientific evidence be reviewed to provide a scientific foundation to the therapies used for treating the common cold. Rhinothermy has been used to treat volunteers with laboratory-induced common cold. This review has included all such trials using hot, humid air.
To assess the effects of inhaling heated water vapour (steam) in the treatment of the common cold by comparing symptoms, viral shedding and nasal resistance.
Criteria for considering studies for this review
Types of studies
Randomised controlled trials (RCTs) using rhinothermy to treat common cold symptoms.
Types of participants
The treatment group consisted of people of all ages, suffering from naturally or experimentally induced common cold or acute viral rhinopharyngitis, receiving warm vapour inhalation via a rhinotherm. The control group consisted of people suffering from similar complaints, receiving room temperature air or room temperature humidified air.
Types of interventions
The treatment group intervention consisted of breathing from apparatus delivering hot, humidified air with the help of a rhinotherm at 40°C to 47°C in order to raise the intranasal temperature. The control group intervention consisted of breathing from an apparatus delivering humidified or ambient air at temperatures of 30°C or below.
The rhinotherm is an instrument that delivers hot, humidified air at a controlled temperature. All included trials, except the two conducted by Tyrrell (Tyrrell 1989a; Tyrrell 1989b) used a similar rhinotherm to Netzer Sereni, Beer Yaakov, Israel which is a microprocessor-controlled instrument delivering warm, saturated air with the help of two exhaust nozzles. Tyrrell used a rhinotherm manufactured by Beecham. This was presumed to be an improvement over the rhinotherm manufactured by Netzer Sereni, as it was possible to mask which machine was used in the control population.
Types of outcome measures
This was based on symptoms of nasal blockage, sneezing and nasal drainage which were scored on a four-point scale of zero to three (zero = no symptoms, one = mild, two = moderate and three = severe). These scores were averaged to a symptom index (SI). The percentage change in the SI was calculated by a formula [(1-A)/Bx100] where A is the SI value while on treatment and B is the baseline SI value. In using this formula, a positive change indicated an improvement in the symptoms and a negative value indicated a deterioration. Other scales (Hendley 1994; Tyrrell 1989a) using a four-point score calculated in a standard way, based on severity of the symptoms like sneezing, rhinorrhoea, nasal obstruction, sore throat, cough, headache, malaise and chills, were analysed separately.
- Decrease in the weight of nasal secretions. Nasal secretions were weighed by Tyrrell 1989b.
- Number of participants with no symptoms.
- Decrease in nasal resistance as measured by a rhinomanographer (ICS Medical Corporation, Schaumburgh Ill) (Forstall 1994; Macknin 1990). Total nasal resistance was calculated using the formula R = (RNxLN)/(RN+LN) where R indicates total resistance; right nostril (RN) resistance; and left nostril (LN) resistance. Ophir (Ophir 1987) had used the Youlten Peak Nasal Inspiratory Flow meter (Clement Clarke Ltd) to measure the nasal peak inspiratory flow. They used a MiniWright peak flow meter to measure peak expiratory flow rate through the nose and calculated a blockage index (BI) calculated according to the formula BI = PEF(mouth) - PEF (nose)/PEF(mouth). A higher BI indicates more nasal blockade.
- Decrease in viral culture titres in the nasal secretions. Tyrrell 1989b had collected nasal washings each day and tested for the virus. Hendley 1994 had performed a nasal wash with 10 ml of saline at 4 am and 8 am. 2 ml aliquots of both washings were pooled and combined with 1 ml of media containing protein and antibiotics before being stored at -70°C. The infectivity titre of the rhinovirus in the specimen was determined using fibroblast cell culture.
Search methods for identification of studies
Details of the initial search for this review first published in 1999 and the subsequent updated searches run in 2003, 2005 and 2010 are in Appendix 1.
For this 2013 update we searched the Cochrane Central Register of Controlled Trials (CENTRAL) 2013, Issue 2, part of The Cochrane Library, www.thecochranelibrary.com (accessed 12 March 2013), which contains the Cochrane Acute Respiratory Infections Group's Specialised Register, MEDLINE (May 2010 to February week 4, 2013), EMBASE (July 2010 to March 2013) and Current Contents (2010 to March 2013). We used the following search terms to search MEDLINE and CENTRAL. We combined the MEDLINE search with the Cochrane Highly Sensitive Search Strategy for identifying randomised trials in MEDLINE: sensitivity- and precision-maximising version (2008 revision); Ovid format (Lefebvre 2011). See Appendix 2 for details of the Embase.com search strategy and Appendix 3 for details of the Current Contents search strategy.
1 Common Cold/
2 common cold*.tw.
5 (nasopharyngit* or rhinopharyngit*).tw.
6 (acute adj2 rhinit*).tw.
7 (upper adj2 (respiratory infection* or respiratory tract infection*)).tw.
8 ((nasal or nose*) adj1 (blocked or blockage* or obstruct* or congest* or stuffiness or stuffy or discharge or runny or running)).tw.
9 (nasal mucus or nasal mucous).tw.
11 coronavirus/ or coronavirus 229e, human/ or coronavirus nl63, human/ or coronavirus oc43, human/
12 Coronavirus Infections/
13 Adenoviruses, Human/
14 Adenovirus Infections, Human/
15 ((rhinovir* or coronavir* or adenovir*) adj2 infect*).tw.
20 ((heat* or hot or warm* or humid*) adj3 air).tw.
21 exp "Nebulizers and Vaporizers"/
22 Administration, Inhalation/
23 (inhal* or atomi* or vapor* or vapour* or nebuli*).tw.
25 16 and 24
Searching other resources
Both review authors scanned reference lists of articles identified by handsearching and contacted trial authors and other experts in the field. We did not have any language or publication restrictions.
Data collection and analysis
Selection of studies
We included studies if they met the selection criteria based on type of intervention (rhinothermy), participants (suffering from common cold) and method of allocation (randomised). An information specialist (Poonam Chaudhury) blinded the trials. The two review authors independently applied the selection criteria. Disagreements were resolved by discussion.
Evaluation of trials addressing inhalation of heated humidified air
In previous versions of this review the studies were subjected to validity scoring for methodological quality by a score based on principles set by Hill (Hill 1962) and modified by Thomsen and Kramer (Thomsen 1984). Each article was scored on 11 criteria worth 13 points in total. An arbitrary cut-off point of 70% (that is to say, 9/13) determined which articles were to be included. This validity score covers the definition of participants, allocation of participants to the treatment groups, description of treatment and measurement of the outcome. Both review authors independently assessed the studies for these scores. Differences were resolved by discussion. We also carried out a quality assessment (Schultz 1995) to see if the subject allocation was randomised, treatments were blinded to the participants and the investigators, drop-out details were given or an intention-to-treat (ITT) analysis was done.
- Research goal: is it clearly defined (that is to say, we wish to analyse the reduction in frequency of cold symptoms) or vague (that is to say, we wish to examine the effectiveness of hot, humidified air in the treatment of the common cold)?
- clearly defined (1);
- poorly defined (0).
- Subject definition: what ages and conditions were included in the study group? Were allergy, bacterial infection, septal deviation or similar conditions excluded?
- states criteria for entry (1);
- states criteria for exclusion (1);
- states how participants were obtained (1);
- not stated (0).
- 3. Randomisation: were the patients allocated to each group with a known probability?
- yes (1);
- no (0).
- Equivalence of groups: was an attempt made to ensure similarity of treatment and control groups?
- yes (1);
- no (0).
- Treatment definition: were the experimental and control treatments defined?
- yes (1);
- no (0).
- Investigator(s) blinded?
- yes (1);
- no (0).
- Subjects blinded?
- yes (1);
- no (0).
- less than 10% drop-outs (1);
- more than 10% drop-outs and accounted for (1);
- more than 10% drop-outs and not accounted for (0).
- Outcome measures: were they objective (for example, a decrease in cough frequency as measured by a tape recorder or decreased weight of nasal secretions or the number of paper tissues) or well-defined subjective assessments (for example, days of headache, nasal discharge and itchy eyes)?
- objective or well-defined subjective criteria (1);
- vague or ill-defined (0).
- Statistical inferences: was any attempt made to define statistical significance?
- yes (1);
- no (0).
- Clinical significance:
- considered error if sample was large and differences were small (1);
- considered error if sample was small and differences were not statistically significant (1);
- not discussed (0).
Data extraction and management
The two review authors independently extracted data using a pre-designed data extraction form. We resolved disagreements by discussion.
Assessment of risk of bias in included studies
We assessed risk of bias in all included studies using The Cochrane Collaboration’s 'Risk of bias' tool (Higgins 2011).
1. Random sequence generation (selection bias) assessed as high risk, low risk and unclear risk
Low risk: when the study described the method used to generate the allocation sequence in sufficient detail.
High risk: sequence not generated.
Unclear risk: when it was not described or incompletely described.
2. Allocation concealment: assessed as high risk, low risk and unclear risk
Low risk: when the study described the method used to conceal the allocation sequence in sufficient detail.
High risk: described details where allocation concealment was not done.
Unclear risk: when it was not described or incompletely described.
3. Blinding of participants and personnel assessed as high risk, low risk and unclear risk
Low risk: when it was a double-blind study.
High risk: when it was an unblinded study.
Unclear: not clearly described.
4. Blinding of outcome assessment assessed as high risk, low risk and unclear risk
Low risk: when it was a double-blind study.
High risk: when it was an unblinded study.
Unclear risk: not clearly described.
5. Incomplete outcome data: assessed as high risk, low risk, unclear risk
Low risk: described the completeness of outcome data for each main outcome, including attrition and exclusions from the analysis.
High risk: the number or reasons for dropouts and withdrawals were not described.
Unclear risk: either not described or incompletely described.
6. Free of selective outcome reporting: assessed as high risk, low risk and unclear risk
Low risk: results of study free of selective reporting. Details of all the patients enrolled in the study are included in the paper.
High risk: details of all the enrolled patients are not given in the paper.
Unclear risk: details of all the enrolled patients incompletely described.
7. Other sources of bias
Among the other sources of potential bias considered was funding agencies and their role in the study. We recorded funding agencies as government agencies, universities and research organisations or pharmaceutical companies. We considered studies supported by pharmaceutical companies to be unclear unless the study defined the role of the pharmaceutical companies. We also considered studies not mentioning the source of funding as unclear under this heading.
Measures of treatment effect
We entered data from dichotomous outcomes and determined a pooled odds ratio (OR). The data from continuous variables could not be pooled due to non-availability of the detailed values of variables and the absence of standard deviation in the published data of some of the studies.
Dealing with missing data
Drop-out rates were mentioned in all the studies. None of the studies conducted an intention-to-treat (ITT) analysis.
Assessment of heterogeneity
We assessed heterogeneity using eyeballing, the Chi
Assessment of reporting biases
We only included published studies. Funnel plots could not be constructed due to paucity of studies.
We conducted pooling of data using ORs with a fixed-effect model.
Subgroup analysis and investigation of heterogeneity
No subgroup analyses were planned for this review.
Description of studies
No new trials were included or excluded in this 2013 update.
Results of the search
We retrieved 89 records in this updated search of electronic databases. Previously we retrieved a total of 54 abstracts using the above search strategy. We included five RCTs which used the standard equipment. One review article mentioned the use of hot, humid air (Arroll 2005). Three trials were case series and were therefore excluded (Baroody 2000; Grübber 2003; Yerushalmi 1980).
We included a total of five trials (Forstall 1994; Hendley 1994; Macknin 1990; Ophir 1987; Tyrrell 1989a; Tyrrell 1989b). The trial by Tyrrell 1989 had a clinical and an experimental arm. Therefore this was dealt with separately as Tyrrell 1989a and Tyrrell 1989b. All the included studies were randomised and double-blinded. All the included studies scored 10 or more points when evaluated by 13-point scoring system.
Forstall 1994. A double-blind, randomised, placebo-controlled study was conducted at Cleveland, Ohio, USA. There were 75 participants (75.5% females) divided into two groups; 68 participants were at least 18 years of age, with nasal congestion, discharge or sneezing. The intervention was administered with the rhinotherm instrument (Netzer Sereni, Beer Yaacov, Israel) delivering 40 L/min of saturated constant air flow at 47°C. Nasal airway resistance for each participant was measured following one hour of treatment with steam. Placebo patients underwent 2 L/min of ambient air at 20 to 24°C. The outcome of the study was skewed with placebo participants having a higher nasal resistance than the treatment participants (6.0 versus 3.9, P = 0.04). Identical symptom experiences were measured by participants and investigators (using System Index (SI) cards, an averaged value calculated from the symptom score card). The percentage of change from the baseline was used as an outcome in this study between the two groups. The study concluded that warm, humidified air at 47°C was no better than 20 to 24°C with a detrimental effect on nasal resistance seven days after treatment.
Hendley 1994. A double-blind, randomised, placebo-controlled study was conducted in Charlottesville, Virginia, USA with experimentally induced rhinoviral infection in 20 healthy participants. The inoculation was done with coarse drops of untyped human virus culture. Individuals having fever, respiratory illness, taking antihistamines, decongestants, steroids or nasal spray were excluded. The intervention was delivered with the rhinotherm instrument. An active machine delivered humidified air at a temperature of 42 to 44°C at a flow rate of 38 to 40 L/min, whereas the placebo machine delivered at 22 to 23°C at flow rate of 2 L/min. At 24 and 48 hours after viral inoculation there was no difference in titres of rhinovirus in the active and placebo groups prior to and following treatment. Viral shedding and symptom scores were not statistically different between the two treatment groups.
Ophir 1987. Two groups of participants were randomised on a double-blind basis. Thirty-two participants suffering from common cold were treated with heated vapour at 42 to 44°C at a flow rate of 40 L/min and 30 participants were treated with 22 to 24°C (placebo) at 2 L/min by a rhinotherm instrument. The study was conducted at Kaplan Hospital, University of Jerusalem, Israel. Two treatments of 20 minutes with 60 to 90-minute intervals demonstrated a significant improvement in nasal blockage index in the active group (P < 0.01). Symptomatic improvement was reported by 92.9% in the active treatment group and 84.6% in the placebo-treated group. The morning after the treatment, nasal patency was significantly increased from 61% to 74% in the active treatment group and from 6% to 8% in the placebo group.
Macknin 1990. A randomised, double-blind, parallel-group comparison was conducted in Cleveland, Ohio, USA. A study group of 32 ranged in age from 14 to 60 (mean 36 years age) and the placebo group of 34 ranged in age from 16 to 48 (mean 32 years age). There were no gender or racial differences between the groups. The active machine delivered heated, distilled water (42 to 45°C) at 40 L/min, whereas the placebo machine delivered at 20 to 24°C at a 2 L/min flow rate. The nozzle was held at 2 to 5 cm from the nares and air was exhaled through the mouth. The intervention was for 20 minutes spaced 60 to 90 minutes apart. The rhinomanographer measured nasal resistance from day one through to day seven. It was 11% better in the placebo group and 6% worse in the active group (P < 0.05). On day three, six and seven, SI score measurements favoured the placebo group. The results did not support the use of rhinothermy in common cold treatment due to a four-fold increase in side effects in the placebo group.
Tyrrell 1989a. Ninety-six patients were enrolled in a randomised trial in the Adelaide Centre, Andover, UK. Out of 87 selected participants, 45 received humidified air at 43°C and 42 received it at 30°C at a rate of 40 L for 20 minutes with apparatus supplied by A. Beecham. The ratio of male to female was 23/22 in the study group an 17/25 in the placebo group. The data on 45 participants given steam at 43°C and 42 patients at 30°C support an improvement in common cold symptoms after treatment. Inhaling warm, humidified air through a rhinotherm also decreased the mean symptom scores to 9.3 and 25.9. Rank sum analysis was performed between the two groups which corrected the imbalances in the study.
Tyrrell 1989b. After two days of quarantine 75 participants were experimentally induced with intranasal drops of human rhinovirus type 14. The study was conducted in the Adelaide Centre, Andover, UK. Volunteers were randomised to receive water vapour at 43 or 30°C for 30 minutes. They received three treatment of 30 minutes each with 90 minutes between them. There was a significant difference in the proportion of shedding of virus and nasal secretions between the two groups. Symptom rating immediately after treatment was 14 in the 30°C group compared to 39 in the 43°C group. There was no significant difference in mean titres regarding convalescence. Antibody response frequency was 5/14 in the 43°C group and 7/13 in the 30°C group.
Risk of bias in included studies
|Figure 1. 'Risk of bias' graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.|
|Figure 2. 'Risk of bias' summary: review authors' judgements about each risk of bias item for each included study.|
Information about allocation of randomisation sequence and concealment of allocation was unclear in most of the studies.
The treatment and control interventions were delivered by similar instruments. However, the temperature of the water aerosol was set at room temperature in all the included studies.
Incomplete outcome data
We made attempts to retrieve the missing data by writing to the trial authors. However, only published information was used.
No evidence of selective reporting of outcomes, time points, subgroups or analyses could be found.
Other potential sources of bias
We did not identify any other potential bias concerns.
Effects of interventions
Reduction in the clinical severity of the common cold (i.e. a decrease in the symptom score index)
A systematic review of six studies does not give unequivocal evidence supporting the use of warm vapour inhalations in the common cold. No studies demonstrated a worsening of clinical symptom scores (odds ratio (OR) 0.31; 95% confidence interval (CI) 0.16 to 0.60) ( Analysis 1.1).
Three studies (Forstall 1994; Macknin 1990; Ophir 1987) used a similar symptom score index. While the study by Ophir 1987 conducted in Israel had shown a significant improvement in the symptom index (SI), the other two trials conducted in the USA failed to show any improvement in the symptom score index. The study by Macknin (Macknin 1990) conducted in Ohio, USA showed a greater change towards improvement in symptoms from baseline in the placebo group. These studies could not be pooled due to non-availability of standard deviations. Tyrrell 1989a in their general practice study and in the volunteer study showed more improvement in the steam group. A different symptom score used by Hendley 1994 did not show any significant difference between the study and the control interventions.
Decrease in the weight of nasal secretions
None of the studies in this review commented on the weight of nasal secretions of the participants.
Number of participants with no symptoms
None of the studies in this review commented on number of participants with no symptoms.
Decrease in nasal resistance as measured by a rhinomanographer
Three studies (Ophir 1987; Tyrrell 1989a; Tyrrell 1989b) showed improvement in subjective parameters. One study (Forstall 1994) demonstrated increased nasal resistance one week after steam inhalation (data skewed at entry) in contrast to an earlier study (Macknin 1990), which showed improvement in nasal resistance. There was no objective evidence of decreased viral shedding in the participants given steam inhalation. The data could not be pooled.
Decrease in viral culture titres in the nasal secretions
None of the studies in this review commented on decrease in viral culture titres in the nasal secretions of the participants.
Only one study (Hendley 1994) in Analysis 1.2 showed that there was no significant difference in the number of patients without any improvement in the two groups (Figure 3). Also in Analysis 1.3 only one study (Hendley 1994) showed that there was no statistically significant difference in number of nasal wash cultures obtained from the participants (Figure 4).
|Figure 3. Forest plot of comparison: 1 Rhinothermy versus control, outcome: 1.2 Number of participants with no improvement in symptom score.|
|Figure 4. Forest plot of comparison: 1 Rhinothermy versus control, outcome: 1.3 Number of participants with positive nasal wash culture.|
Macknin 1990 in Analysis 1.4 showed that side effects were more in the group in which rhinothermy was given but the result was not statistically significant (Figure 5). Minor side effects reported were nasal and lip irritation, lightheadedness, running make-up, increased congestion and discomfort from the attached mask (Macknin 1990). Forstall 1994 reported episodes of nasal congestion, minor mucosal burns and discomfort from condensation in the attached mask. Despite the difficulty in tolerating the steam treatment, both groups reported that the treatment helped. One patient was reported to have suffered temporary dizziness for two to three minutes following treatment with saturated hot air (Ophir 1987). However, the studies reporting side effects due to thermal discomfort had used the treatment for a longer duration.
|Figure 5. Forest plot of comparison: 1 Rhinothermy versus control, outcome: 1.4 Subjective response: side effects were present.|
Analysis 1.5 showed that response was better with rhinotherapy but was not statistically significant.
There is a difference in the efficacy results of warm vapour inhalation trials conducted in the UK and Israel, compared to studies conducted in the USA, even though similar equipment and methodologies were used. The studies from the UK and Israel reported beneficial effects of rhinothermy in participants with rhinopharyngitis, whereas three randomised controlled trials (RCTs) from the USA failed to replicate the findings of these previous investigations. The slight difference in equipment was in relation to the administration of warm vapour by anaesthetic mask or nozzle. It is possible that there is a difference in the epidemiology of rhinoviral infections in the participants from different geographical areas, especially in relation to viral strains. Climatic and seasonal differences may also have affected the outcome.
There was a difference in the duration of warm vapour inhalation, with a longer period (30 minutes) being associated with no benefit and increased resistance of the nasal passage. Hence, one can postulate that an optimum duration of heat administration would coincide with a subjective feeling of comfort. According to the present evidence, rhinothermy cannot be recommended in the routine treatment of common cold symptoms.
Summary of main results
This systematic review of heated, humid air in the treatment of the common cold included six trials. Three trials (Ophir 1987; Tyrrell 1989a; Tyrrell 1989b) found benefits of steam for symptom relief with the common cold (OR 0.31; 95% CI 0.16 to 0.60). The sample size, however, was small and studies showed significant heterogeneity. Results on symptom indices were equivocal. No studies demonstrated an exacerbation of clinical symptom scores (Figure 6; Figure 3). One USA study (Forstall 1994) demonstrated worsened nasal resistance, while an earlier Israeli study (Ophir 1987) showed improvement. One study (Hendley 1994) examined viral shedding and antibody titres in nasal washings: there was no change in either between treatment and placebo groups. Minor side effects (including discomfort or irritation of the nose) were reported in some studies (Forstall 1994; Macknin 1990).
|Figure 6. Forest plot of comparison: 1 Rhinothermy versus control, outcome: 1.1 Number of participants with persistent symptoms.|
Overall completeness and applicability of evidence
Although there is evidence that rhinothermy aided symptoms of common cold in two trials (Figure 6), the totality of evidence is not significant enough to recommend this therapy in routine practice.
Quality of the evidence
Most of the evidence in this review comes from well-controlled and blinded trials using hot, humid air from a standardised source. However, the sample size was small and none of the studies could be pooled due to variability in the outcomes reported.
Potential biases in the review process
We made an attempt to reduce the bias in the review process by using a standardised search strategy. Two review authors extracted and quality scored data independently.
Agreements and disagreements with other studies or reviews
A review of non-antibiotic treatments for upper respiratory tract infections (the common cold), based on seven Cochrane Reviews and presenting risk ratios for outcomes, drew similar conclusions (Arroll 2005).
Implications for practice
Steam inhalation has not shown any consistent benefits in the treatment of the common cold, hence it is not recommended in the routine treatment of common cold symptoms until more double-blind, randomised controlled trials (RCTs) with a standardised treatment modality are conducted. The decision to use this therapy should be determined by a cost benefit analysis, depending on the prevailing economic variables of an area.
Implications for research
There is a need for a large, multicentre study using rhinothermy to treat the symptoms of the common cold, including a detailed cost benefit analysis of using this equipment. The outcome measures should be dependent upon the frequency of common cold symptoms and a definitive diagnosis based on viral cultures, using a uniform symptom score index and nasal resistance measurements.
The Library Service, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India. The author wishes to thank the following people for commenting on the 2006 update: Amy Zelmer, Ian Williamson, Robert Ware and Chris Del Mar. We also wish to thank Anil Chauhan, PhD Fellow at PGIMER, Chandigarh, for helping search the original studies, and Liz Dooley, Managing Editor of the Cochrane ARI Group for editorial assistance.
Data and analyses
- Top of page
- Authors' conclusions
- Data and analyses
- What's new
- Contributions of authors
- Declarations of interest
- Sources of support
- Index terms
Appendix 1. Previous search strategies
In 1999 when we published the first review we searched MEDLINE using the following MeSH headings: common cold; rhinopharyngitis; inhalation; steam and heated vapour. We used the highly sensitive search strategy for identifying RCTs as given in the Cochrane Handbook for Systematic Reviews of Interventions. We used different combinations of terms to retrieve the maximum number of studies. We searched EMBASE, Current Contents, review articles and cross-references. We wrote letters to the manufacturers of the rhinotherm equipment for any unpublished trials. We did not receive any replies.
In 2003, we updated this review to identify all recent RCTs in any language. We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2003, Issue 4), which contains the Cochrane Acute Respiratory Infections Group's Specialised Register, MEDLINE (January 1966 to November Week 2, 2003), EMBASE (January 1990 to November 2003) and Current Contents (current five years).
In 2005, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2005, Issue 4), which contains the Cochrane Acute Respiratory Infections Group's Specialised Register, MEDLINE (2003 to December Week 2, 2005); EMBASE (July 2003 to September 2005) and Current Contents (current five years). No new trials were identified.
In the 2010 update we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2010, Issue 3), which contains the Cochrane Acute Respiratory Infections Group's Specialised Register, MEDLINE (December 2005 to July week 1, 2010), EMBASE.com (September 2005 to July 2010) and Current Contents (2005 to July 2010). We used the following search terms to search MEDLINE and CENTRAL. We combined the MEDLINE search with the Cochrane Highly Sensitive Search Strategy for identifying randomised trials in MEDLINE.
1 Common Cold/
2 common cold*.tw.
5 coronavirus/ or coronavirus 229e, human/ or coronavirus oc43, human/
8 ((rhinovir* or coronavir* or picornavir* or adenovir*) adj2 infect*).tw.
14 ((heat* or hot or warm*) adj5 air*).tw.
16 Administration, Intranasal/
17 ((nose* or nasal or intranasal) adj5 inhal*).tw.
18 exp "Nebulizers and Vaporizers"/
19 ((heat* or hot or warm*) adj3 (vapour* or vapour* or nebul* or atomi*)).tw.
21 9 and 20
Appendix 2. Embase.com search strategy
#18 #12 AND #17
#17 #13 OR #14 OR #15
#16 inhal*:ab,ti OR atomi*:ab,ti OR vapor*:ab,ti OR vapour*:ab,ti OR nebuli*:ab,ti
#15 'nebulizer'/exp OR 'inhalation'/de
#14 steam*:ab,ti OR ((heat* OR warm* OR hot OR humid*) NEAR/3 air):ab,ti
#13 'water vapor'/de OR 'humidity'/de
#12 #1 OR #2 OR #3 OR #4 OR #5 OR #6 OR #7 OR #8 OR #9 OR #10 OR #11
#11 ((rhinovir* OR coronavir* OR adenovir*) NEAR/2 infect*):ab,ti
#10 'human adenovirus'/exp OR 'human adenovirus infection'/de
#9 'coronavirus'/de OR 'human coronavirus nl63'/de
#8 'rhinovirus infection'/de OR 'human rhinovirus'/de
#7 'nasal mucus':ab,ti OR 'nasal mucous':ab,ti
#6 ((nasal OR nose*) NEAR/1 (blocked OR blockage* OR obstruct* OR congest* OR stuffiness OR stuffy OR discharge OR runny OR running)):ab,ti
#5 'upper respiratory tract infection'/de OR 'viral upper respiratory tract infection'/de
#4 nasopharyngit*:ab,ti OR rhinopharyngit*:ab,ti
#2 'common cold':ab,ti OR 'common colds':ab,ti OR coryza:ab,ti OR (acute NEXT/2 rhinitis):ab,ti
#1 'common cold'/de OR 'common cold symptom'/de
Appendix 3. Current Contents (Thomson Reuters) search strategy
Heated humidified air for the common cold
1. I am delighted to see this review: a common and important but long neglected problem - and a marvellous introductory quote! I hope my comments may help you clarify some aspects.
2. Objectives: it would be good to specify the comparisons to be made in the review.
3. Types of participants: the treatment group includes people with "acute viral rhinopharyngitis" [avr], but the control group does not. Is avr synonymous with "common cold"? Healthy volunteers inoculated with virus are not patients, nor are people with a spontaneous or 'natural' cold who have not consulted a health professional.
4. Types of intervention: "... delivering hot humidified air ... at 40-44 deg C." This should exclude the Forstall 1994 study, in which the air was delivered at 47 deg, or if it is included it must at least be analyzed separately. It would be useful to add an illustration of the Rhinotherm apparatuses - say line drawings.
5. Types of outcome measures: detailed reporting and discussion of the symptom scores used in the trials is necessary. They are unlikely to have used the same scoring methods, and cannot be combined without explicit justification.
6. Methods of the review: the validity score used assumes that all the points are equally important, and is therefore misleading. As the Cochrane Reviewers' Handbook 4.0 [end of section 6.7.2] says " ... it is preferable to ... report how each trial scored on each criterion".
7. Results: the results should be reported separately for each of the different comparisons to be made, and also separately for each of the 5 outcome measures. Only then will it be possible to decide whether it is appropriate to lump together any of the comparisons or the
outcome measures. In the absence of such an analysis the MetaView summary cannot be interpreted.
8. Discussion: it is not clear where each trial was done. This should be noted in the table of Characteristics of included trials. Geographical differences may not only imply different epidemiology of rhinovirus infection, but also climatic and seasonal differences which could affect
outcomes. The two experimental studies by Tyrrell should not be lumped with the others.
9. Characteristics of included trials: At what stage in the infection, for how long, and how many times were the inhalations used in each trial? For some trials details are incomplete, eg Ophir: source of patients, length of follow up. Tyrrell-1 and -2: length of follow up.
10. Conclusions: I think the implications for practice need to be rethought in the light of a more detailed analysis.
The review has been revised after these comments.
Feedback and reply added 27 July 2001
Last assessed as up-to-date: 12 March 2013.
Review first published: Issue 3, 1999
Contributions of authors
Meenu Singh was the sole author of this review and subsequent updates until 2005. The current update was conducted jointly by Meenu Singh and Manvi Singh.
Declarations of interest
None known. The review authors have not received any support or benefit from the equipment manufacturer(s) mentioned in this study.
Sources of support
- Post Graduate Institute of Medical Education and Research, Chandigarh, India.
- eHealth Project, Ministry of Health and Family Welfare, Government of India, India.Financial Support to Poonam Chaudhary, B. Lib. Information specialist.
This updated review was first submitted to The Cochrane Library as a review - no protocol was ever published. The protocol and the review had been completed for an acute respiratory infection conference held in Canberra, organised by Bob Douglas.
Medical Subject Headings (MeSH)
*Air; *Steam [adverse effects]; Common Cold [*therapy; virology]; Heating; Humidity; Picornaviridae Infections [therapy]; Randomized Controlled Trials as Topic; Respiratory Therapy [*methods]; Rhinovirus [physiology]; Virus Shedding
MeSH check words